X—
Between Peace and War

The academic year 1939/40, which was not a good time for most of the world, was one of great achievement and even greater promise at the Laboratory. As the Nazis prepared to invade Poland, Alvarez and Cornog cleared up the isobars of mass three; as the Nazis overran Belgium, Kamen and Ruben established the radioactivity of C¹⁴ ; on the weekend of December 22, while Finnish and Russian troops bled one another in the snow, the Laboratory presented a sample of its wide-ranging activities to the American Physical Society, meeting in Berkeley. Alvarez and Cornog disclosed their discovery of tritium; Helmholz described gamma-ray conversions in technetium and other metals; Kruger held out hope for radiological cure of cancer; Corson and Mackenzie discussed activities in bismuth and polonium irradiated by alpha particles from the 60-inch; and, to round out the spectrum, Cornog presented an engineering accomplishment, the pumping system of the mighty cyclotron.^[1] The machine hummed along, "almost a push-button cyclotron." Its breakdown in January 1940 measured the extent of troubles in the land of milk and honey.^[2]

The most promising enterprises of the year were the expansion of the medical program owing to the completion of the 60-inch, the pursuit of transuranic elements, and, above all, the planning of

what would be the largest cyclotron ever made. The macho character of cyclotroneering found clear expression as Lawrence's "boys" prepared to create their "he-man cyclotron," "the father of all cyclotrons," on a hill dominating the Berkeley campus. Oliphant's Birmingham bomber, though bigger than the 60-inch, would be—so Lawrence put it in a letter to his cousin—but a "toy," a thing for children, in comparison with the manly machine on the drawing boards in Berkeley.^[3] The requirements of this machine were to bring the war closer to the Laboratory; and the machine itself was to become the chief instrument of the Laboratory's eventual mobilization.

1—
The He-Man Cyclotron

Skinning Cats

It took a man of singular determination and self-confidence to propose a cyclotron capable of accelerating particles to 100 MeV. The substantial cost—projected at perhaps a million dollars—was not at first the major impediment. Nature, not money, seemed to set a limit to the size of cyclotrons. The difficulty, that the increase of mass with speed claimed by the theory of relativity would destroy the synchronism expressed in the cyclotron equation (2.1), had been noticed in 1931, by Livingston and by Feenberg; but the limit, whatever it might be, evidently did not affect the performance of the first cyclotrons, and the menace faded from view. When presenting Lawrence with the Comstock prize in November 1937, W.D. Coolidge saw no obstacles: "The limit to the particle energies which can be generated in this way is not yet in sight."^[4] Precisely at that moment, however, Bethe and his student Morris E. Rose declared that in their calculations relativity limited the maximum energies obtainable in a cyclotron to about those achievable with the 37-inch machine. They observed that to

compensate for the continually rising mass, the magnetic field must increase toward the periphery of the orbit to keep the circulating particles in phase with the oscillator. But to focus the particles in the median plane, the field must decrease from the center outward. The cyclotroneer wants both resonance and focusing; nature requires a choice.

According to Bethe and Rose, the best that can be done is to sacrifice exact resonance; but even so, and with the best field design they could contrive, maximum energy would be 5.5 MeV for protons, 8 MeV for deuterons, and 16 MeV for alpha particles. This estimate supposed 50 kV on the dees; with 100 kV something more could be done, since the accelerated particles would acquire energy more quickly and so have more of it when they finally fell out of phase with the accelerating voltage. Still the outlook was grim. With a magnetic field of 18 kilogauss and a final orbit 37 cm in radius, deuterons of 11 MeV would emerge, "the highest obtainable with as much as 100 kV dee voltage." For such a cyclotron, pole faces 34 inches in diameter would suffice. "Therefore it seems useless to build cyclotrons of larger proportions than the existing ones."^[5]

When the Laboratory received this news, it was engaged in what, according to the Cassandras of Cornell, was a wasteful and useless task. But its experience with the 37-inch gave it confidence that the 60-inch could go beyond 10 MeV despite the most refined calculations to the contrary. Lawrence wrote Bethe that relativity had not yet begun to inconvenience cyclotroneers; the existing inhomogeneities in the magnetic field of the 37-inch defocused more menacingly than the mass increase and indicated considerable room for maneuver in the 60-inch. And if shimming were to fail, other possibilities existed, for example, placing wire mesh across the mouths of the dees so as to obtain by electrical force the focusing that would be lost by adjustment of the magnetic field to secure resonance. "We have learned from repeated experience that there are many ways of skinning a cat."^[6]

This response was not bluff. For a year or so Robert Wilson had been poking around inside the cyclotron tank, determining empirically the strength of the vertical component of the electric field near the dee mouths and of the radial component of the fringing magnetic field, which drives ions toward the meridian plane. The investigation of the circulating current, which eventuated in the internal target for isotope production, was part of his study. Wilson painstakingly worked out the trajectories of ions beginning their courses at any distance from the median plane and reaching the center of the gap in phase with the maximum field there. His numerical integrations showed that from about 10 cm out, where the focusing effect of the electric field becomes negligible (it decreases with the particles' energy), the magnetic field swiftly reduced the vertical amplitude of the beam from a spread of some 5 cm near the ion source to about 1 cm at the exit slit. Probe measurements confirmed Wilson's semi-empirical deduction of beam width as a function of orbital radius. He therefore felt confident in recommending that the aperture of the dees also be made to decrease with radius, thereby reducing their capacitance and easing the performance requirements for power oscillators to accelerate protons.^[7]

Wilson presented his results in a seminar about the time that Bethe and Rose's letter of November 24 was circulating in Berkeley. The circumstances inspired McMillan to estimate the defocusing effect of relativity. It was he who found that for the 37-inch defocusing arising from inhomogeneities in the magnetic field exceeded that from relativity by a factor of four. Also, McMillan calculated from experience at Berkeley that the beam could fall out of phase with the electric field by more than 60° and still get through the cyclotron; and on this basis he calculated that the maximum energy of deuterons achievable without altering basic cyclotron design was perhaps   MeV with 100 kV on the dees. With Lawrence's grids, he thought, any amount of electrostatic focusing could be attained.^[8] On this last point McMillan had a short and victorious duel by mail with Bethe, who had thrust forward the opinion that "no change of the shape of the dees, no

insertion of grids at the dee openings, etc., can have any appreciable effect on the electric focusing." McMillan parried that Bethe had mistakenly assimilated a dee with grid to an open dee of smaller aperture; Bethe concurred, and allowed the possibility of doubling the energy limit.^[9]

Meanwhile Rose, who had also been working for a long time on cyclotron focusing, sweated to get his theory ready for the press. Whereas Wilson and McMillan relied on their experience with a single machine, Rose began with general equations of motion in changing electric and magnetic fields and deduced, by clever substitutions, a differential equation for the excursion of an ion from the median plane as a function of the phase of the radio frequency voltage it met as it crossed between the dees. His treatment of the general case—which "had been considered much too complicated for solution by many"—agreed with the conclusions about electric and magnetic focusing reached in Berkeley.^[10] Rose could do more: from his differential equation he could deduce the maximum energy obtainable without defocusing the beam when the gradient of the magnetic field compensates for relativity. He ended more generous than he and Bethe had begun. They allowed, in a note added to their initial announcement on December 4, that a field giving an angular velocity too large for resonance at the start and too small at the finish could deliver deuterons of 17 MeV with V = 50 kV, a number Rose raised to 21.1 MeV. These numbers would be multiplied by   if 100 kV were placed across the dees. Rose thought that no greater potential could be reached without severe difficulty and that grids would not have the power Lawrence supposed. "It seems very possible that the energies mentioned [21.1 MeV deuterons] represent the natural upper limit for the cyclotron with the given dee voltage of 50 kV, at least without very radical changes in design."^[11]

As Bethe conceded to McMillan, after explaining that he and Rose had published hurriedly because "we considered the existence of a relativistic limit so important that we thought we should communicate it to cyclotronists as quickly as possible, without endeavoring to give accurate figures," "it makes all the difference in the world whether the limit is 8 MV or 20."^[12] Or 100. The question came before that high tribunal of science, Time , whose investigative science editor, Walter Stackley, drew from Lawrence a firm rejection of the 20 MeV limit. There was new work under way at Berkeley, Lawrence said, "which may increase the energy maxima materially." "We believe that there are experimental possibilities of improving focusing conditions which remove the limitation on energy to some unknown point."^[13] And, just at this point, L.H. Thomas, known to physicists as the discoverer of a relativistic effect important in atomic theory (the "Thomas precession"), described a novel way to achieve both focusing and resonance by a magnetic field that had notably different strengths in several pie-shaped sections into which he divided the median plane. Thomas's ingenious suggestion received some attention at Berkeley and more at Stanford, where Oppenheimer's former student Leonard Schiff continued the calculations. Although the scheme, which is difficult to put into practice, was not exploited at the time, it gave ample evidence that nature did allow for several methods of cat-skinning.^[14]

The opinion of the experienced cyclotroneer about Bethe's limit is nicely reflected in notes by the Rockefeller Foundation's Tisdale. After recording that "Joliot's cyclotron, by a lucky chance, is designed just to the limit of the theoretical voltage," which would have been at once a triumph and an end to the Foundation's investments in cyclotrons, Tisdale reported that Paxton would have none of it. "P[axton] considers that the mass effect is not very important."^[15] The cyclotroneer did not doubt that so refined a thing as a relativity effect could be beaten by brute force.

Thornton: "Difficulties in reaching high voltages seem to me quite real. . . . But of course there are a number of ways [by] which one may get around [Bethe's] objections." Wells: "It can probably be compensated by applied magnetic inhomogeneities of the field or by properly chosen electrostatic fields." Compton: "[It] can be passed (theoretically) by altering pole pieces and electrostatic focusing. Thus no limit is now assignable." Oliphant: "I am not deterred by papers which have been written on the maximum energy obtainable from a cyclotron."^[16] Gentner looked to Thomas's method. Cockcroft preferred to follow Lawrence, who thought azimuthally changing magnetic fields impractical and no longer favored fitting the dees with wires. Instead, he bruited a solution in the style of the Old West: put a million or two million volts on the dees and drive the beam home before it knows that it has been defocused.^[17]

Skinning Fat Cats

Lawrence was planning to build far beyond the Bethe-Rose limit even before the 60-inch machine, which itself crossed the suppositious threshold, came on line. It was not relativity, but money, he said in a radio broadcast in the spring of 1939, that stood in his way. "Right now we are considering the possible financial difficulties of constructing a cyclotron to weigh 2,000 tons and to produce 100 million volt particles. . . . It would require more than half a million dollars."^[18] Both the size and the price were to grow during the next year with the help of the University of Texas and the Nobel Foundation, and with the encouragement of big-thinking colleagues. "I hope your new apparatus is really big," Chadwick wrote, with 60 or 70 MeV in mind. "Best wishes for the beam to end all beams. The best is none too good for the Berkeley boys," wrote I.I. Rabi of Columbia, who would later try

to snatch the best from Berkeley in the interests of East Coast physics.^[19]

Lawrence faced difficulties beyond the relativistic and the financial. For one, there was no uncontested space for a 2,000-ton cyclotron on the Campus. An engineering annex had been needed to house the 27-inch; a special building had been erected for the 60-inch; real estate as large as the Campus would be reserved for the new machine. Then there was a taint of overreaching, of imprudent haste, of gluttony, in the plan. "In some quarters it might be considered no less than shocking that we should be looking towards a larger cyclotron almost before the 60 inch is in operation."^[20] And finally, there was the disagreeable fact that no major discovery had yet been made in any cyclotron laboratory. As Arthur Compton and his colleague A.J. Dempster pointed out to the Rockefeller Foundation, cosmic-ray physicists had made several of the most spectacular discoveries in physics during the 1930s, in particular the positron and the mesotron, and cosmic rays come gratis.^[21]

To this objection Lawrence replied with a claim about the might-have-been and a statement of the what-should-be. The claim: cyclotron physicists had missed the discoveries through a compulsion to perfect their machines; in due course they would have found what others detected earlier with more primitive means. The statement: a discovery has little value unless it can be turned to practical use. "It means a great deal more to civilization, let us say, to find a new radiation or a new substance that will cure disease than it would to discover a super nova." On this reasoning, Joliot and Curie's find would have been barren had it not been for the Berkeley cyclotron. And, Q.E.D., "the discovery of mesotrons in cosmic rays will be of little value in the course of time unless there is developed a way of producing them, and learning of their manifold properties—ultimately to be put in the service of mankind."^[22]

The invocation of mesotrons and the hint that the projected cyclotron might make them came to the fore only after the University of Texas had set going a mechanism that would provide more money than Lawrence thought possible. He and Sproul turned, indeed spun, to one prospective donor or influential intermediary after another. For a time Walcott, the former senator with the leukemic son and a trustee of the Carnegie Institution, looked like an especially valuable contact. Walcott had contacts in big steel; funding would be easy, Lawrence said, if the steel were donated. The son, a physician, came to Berkeley to work with, and receive radiophosphorus from, John Lawrence. A very strong affection developed between the Lawrences and Cooksey and the Walcotts; but it did not bring steel for nothing or save Walcott's son.^[23] Other possibilities: Lewis Strauss, proposed by Oppenheimer and approached through Coolidge; Spencer Penrose, the dying benefactor of the Penrose Foundation, approached through Frank Jewett of Bell Labs; Edsel Ford and General Electric, approached through Dave Morris.^[24]

To his own considerable surprise, Weaver turned out to be the route to the pot of gold. We know his attitude on Rockefeller Foundation support of research cyclotrons. During the negotiations over Paxton and Laslett's foreign missions, he had formed the notion that Lawrence was "a happy-go-lucky sort of individual," a good scientist, but indecisive and not overly solicitous about the inconvenience his changes of plan caused others.^[25] And in his dealings with Lawrence in the spring of 1939, Weaver had not been pleased by the escalation of the Laboratory's request between discussion and submission.^[26] It is doubtful that he

received with much enthusiasm the news that Lawrence was coming East to look for donors of the $750,000 he reckoned as the amount yet to be raised for an instrument of 1,500 to 2,000 tons to crack the region above 100 MeV. The $750,000 arose by subtraction of the $250,000 Sproul promised to raise from the million that Lawrence, who liked round numbers, thought necessary. On the advice of Poillon, who judged that a request for a cool million would put off donors, Lawrence set the total at a lukewarm $900,000 and the balance at $650,000. This was the amount Morris requested of Edsel Ford, with an overheated inducement: "As this is an instrument which will enlarge the frontier of science almost beyond belief it should be something epoch-making and will link the names of those connected with it alongside of Newton and Einstein."^[27]

The justification for this instrument, as outlined to Sproul early in October, when it had grown to 2,000 tons, had no more substance than the rationale Morris offered Ford. There was a more definite and practical reason, however. The success of the cyclotron had inspired competitors, including two clones of the 60-inch; if the Laboratory wished to stay ahead, it must cross the new frontier, where, as cosmic ray studies indicated, "strikingly new and important things" were to be found. Sproul wanted to keep Berkeley ahead. He promised (so Lawrence relayed to Weaver) not only to raise part of the capital outlay but also to finance the operation of the he-man machine. Still, Weaver did not expect that his trustees would take much interest in the proposal, or in any costly esoteric project, in the state of the world in the fall of 1939. Here Lawrence guessed more accurately than Weaver. "I personally am banking on the trustees' taking the view that it is in just such times as these that the Rockefeller Foundation should undertake such important projects, thereby demonstrating a stability and confidence in the progress of civilization."^[28]

Lawrence opened negotiations with the Rockefeller Foundation in New York on October 27. Weaver accepted the desirability of

a cyclotron that endowed particles with 100 or 200 million electron volts; he encouraged Lawrence to think big, to beware of "initial presentation [of the project] on too small a scale;" and he insisted that the plan make clear that the cyclotron would be a national, even international, facility, "located at the University of California . . . [but] built for all science." Weaver assimilated Lawrence's project to what he called the Foundation's "national laboratory," the 200-inch telescope and its facilities abuilding on Mount Palomar; and he estimated its costs correspondingly, at $1.5 million including operating expenses for a decade.^[29]

The announcement on November 9 that Lawrence had received the Nobel prize for physics in 1939 (about which we shall say much more in a moment) strengthened Weaver's commitment to the Palomar of the vanishing small. With the ardor that the higher administration of the Foundation had once censored as excessive, he celebrated Lawrence's prize in a confidential bulletin sent to the Rockefeller trustees and invited the prize winner to put forth a detailed plan for presentation to the next trustees' meeting, in April 1940, a plan so complete that it would kill any fear that similar or competing requests would arise.^[30] "This is the sort of thing which should be done superbly—or not at all. And done superbly it is of compelling attractiveness." Lawrence responded that it should be superb, and raised the weight of the magnet to 3,000 tons, or perhaps (indecisively or flexibly) a little more, and he promised to have full plans for a 180-inch and a 205-inch cyclotron ready for discussion with Weaver in Berkeley in January. Lawrence naturally favored the larger version, as offering a chance of delivering 400 MeV alpha particles.^[31]

When Weaver arrived on January 7, he was hit with a plan for a magnet weighing over 4,000 tons. He had come with Lawrence's estimate of $750,000 in mind and the notion that it,

and perhaps as much again in operating expenses and auxiliary equipment, could be raised in equal shares by the Rockefeller Foundation, the University of California, and industry. "The size to which I found the project had grown, when I arrived at Berkeley [in January]," Weaver sighed, "carried me so far beyond any figures which I had ever discussed." Lawrence wanted $1.5 million of an estimated $2 million from the Foundation. In Lawrence's upbeat report to Poillon, Weaver did not "seem to be unduly distressed . . . [and] went away far more eager to consummate the project than when he came." Weaver had fallen under the spell of the California sunshine man and of the 60-inch cyclotron, then treating cancer patients and, on demand, charring plywood with a directed energy beam of deuterons released into the air. Weaver suggested to Sproul "the bare possibility" that the Foundation might give as much as a million dollars.^[32] Back in the cold East, Weaver discovered that the Foundation's president, Raymond Fosdick, who had been enthusiastic about the project in December, had lost his conviction, and doubted that the trustees would give even $500,000. The January plan was dead. Or so Weaver wrote Sproul, whose recent appointment as a Rockefeller trustee closed the funding loop. "It does not seem to me a desperately serious matter if this project is delayed somewhat. Professor Lawrence is fortunately still young, there is a great deal of rich experience which can be gained with the 60-inch cyclotron, and there is a negligible danger that anyone else will run away with the ball."^[33] This was to ignore Texas, still out in left field awaiting its fly, and Lawrence's flexibility.

During January and early February, friends of the Laboratory brought pressure on Fosdick and their acquaintances among the Rockefeller trustees. Among the friends were old supporters like Poillon, who hoped, perhaps, that something might be realized at last from the Research Corporation's cyclotron patents; Karl Compton, a Foundation trustee; former ambassador Morris, of the

Macy Foundation; and Alfred L. Loomis, who spent the riches he amassed as an investment banker on a private laboratory and the encouragement of physical research. An expert instrument designer himself, Loomis was much taken with the Laboratory on his first visit there late in 1939; his wide influence among officials of corporations and foundations made his support of the project, which he pledged in December, a most valuable acquisition.^[34]

Weaver also made a play among the trustees. He pointed out to Karl Compton the happy parallel between Lawrence's project and the 200-inch telescope. "Such a cyclotron would, I think, be correctly and generally viewed as the definitive instrument for the investigation of the nucleus—the infinitesimally small—just as the 200" telescope is viewed as the definitive instrument for the investigation of the universe—the infinitely great." Compton visited the Laboratory and returned "radiant over all the wonderful things he saw in Berkeley" and convinced that the new machine "should be built adequately large to reach the range of energy above 160 million volts in order to attack the problem of mesotron forces."^[35] After a visit from Weaver, another Foundation trustee, George Whipple, a frequent recipient of hot iron from Berkeley, declared himself keen on the project, and certain that funds would be forthcoming from somewhere; he spoke "with an enthusiasm which is very unusual for him concerning Lawrence and his group, saying that the way they do things out there is 'just right.'"^[36]

Weaver also collected professional evaluations. He asked Bohr, Bush, both Comptons, W.D. Coolidge, Jewett, Joliot, and Oliphant whether "expert opinion of the world of science is reasonably unanimous in viewing [the giant cyclotron] as one of the most interesting, the most potentially important, and the most promising projects in the whole present field of natural science."

The replies might have made Lawrence blush. Bohr: "It would be greeted with utmost pleasure by all physicists." Bush: "This opportunity is the most interesting, the most potentially important, the most promising project of large magnitude in the whole field of natural science." A.H. Compton: "If anyone can make a success of a 2000-ton cyclotron, Lawrence can. . . . On the whole, the investment would be a nice one." K.T. Compton: "I would definitely place it in the number one position by a large margin." Coolidge: "Now is the time to do it while the exceptional combination of enthusiasm, intelligence, experience and skill of Dr. Lawrence and his group are available." Jewett: "[Its] value . . . is of course beyond question." Joliot: "The realization of such an apparatus is likely to bring important results. . . . Lawrence is, without any doubt, the most qualified man to undertake its construction." Oliphant: "It is essential that the construction of the cyclotron should be carried to the limit by Professor Lawrence."^[37]

All this lobbying cancelled Fosdick's timidity. At a meeting in mid February, which Poillon attended, "the Rockefeller [administrative] group distinctly favor[ed] the larger [cyclotron] because of the certainty of its performance within and above the 160,000,000-volt range."^[38] The 160 MeV referred to one of several designs that Lawrence had supplied when he realized there was no chance of $1.5 million from the Foundation. The 205-inch, perhaps so chosen to beat Palomar, fell to 184 inches, the largest size of commercially available steel plate. And the 150-inch stayed in the running. On February 20, 1940, Lawrence provided Weaver with four options: (a) 184 inches, $1.5 million, handsomely housed and fully equipped, operating at 2,500 kW to kick ions to 200 MeV before relativity could take its toll, the "conservatively ideal in exploiting the limit of the cyclotron method;" (b) 184 inches, $1 million, cheaply housed and partially equipped, operating at 700 kW and perhaps yielding 100 MeV deuterons, easily stepped up to (a); (c) 184 inches, $875,000, a skeleton, deficient in copper and steel, producing 75 MeV

deuterons, capable of upgrading to (a); and (d) 150 inches, $750,000, able to reach 100 MeV with an oscillator more powerful than (c)'s, but not easily refashioned into (a). Lawrence took his stand between the most desirable and the least expensive: "It seems to me that attention should be concentrated on projects 'b' or 'c', of course very much preferably 'b'." The 160 MeV probably referred to option (b) and alpha particles, since, with his ear for audience, Lawrence had advised Weaver to couch his statements in terms of alpha energies, which are twice those of deuterons for the same cyclotron parameters and somewhat less afflicted by relativistic mass increase.^[39]

The fundamental alternative—184 inches versus 150 inches—represented a hedged bet. On the one hand, option (a) and its upgradable lower forms would quite possibly be able to materialize mesotrons. DuBridge and Karl Compton emphasized the desirability of building the machine that, as Compton put it, allowed a "reasonable expectation of producing mesotrons." The reasonableness depended on estimates of the mesotron's mass. Karl Compton thought 160 MeV might do; DuBridge, "energies of the order of 100 million electron volts."^[40] Oppenheimer and Fermi, who happened to be in Berkeley, put the mass of the mesotron between 70 and 120 MeV, gave it a 90 percent chance of falling under 100 MeV, and advised that the higher the bombarding energy—the closer to option (a), "which exploits the full practical potentialities of the cyclotron method"—the greater the chance of making mesotrons in the cyclotron.^[41] Lawrence rated the materialization of mesotrons "the most fundamental experimental problem that one can formulate at the present time," and thought he could succeed with 150 MeV. But he did not promise. Although mesotrons might fail to materialize, the energy region above 100 MeV was nonetheless certain to be rich: "we cannot help but entertain the possibility of nuclear chain reactions by starting

them off with sufficiently energetic particles and that maybe a hundred million volt particles will do the trick. . . . Should this prove to be true, we will have a discovery of great immediate practical importance. On the one hand, we will have a practical philosopher's stone transmuting elements on a large scale; and, as a corollary thereto, we will have tapped, on a practical scale, a vast store of nuclear energy."^[42]

Despite these formidable arguments, Lawrence retained option (d). He thus deprived the trustees of the Rockefeller Foundation of the option of arguing that if they could not put up enough for mesotrons, they should put up nothing at all. Lawrence had opened his mind on the matter to Weaver during a telephone conversation at the end of January: "The point is that it is far more important to get into the new territory now. We would rather build a, say, haywire outfit and actually have been up there than to take a chance on going up later and maybe not getting there at all." Occasionally he thought to go for the 150-inch and not risk its loss by groping for mesotrons, and he so advised Weaver by telegram. As he explained his position to Poillon, who had heard similar arguments from him before, the most important thing was "to accomplish the original and primary objective of attacking the energy range in the atom above one hundred million volts. . . . We will be in entirely new territory. . . . It is distinctly of secondary importance that we get a little further in by going 50% higher."^[43] As in the old days, Lawrence set goals expressible not in terms of progress in physics, but in terms of increase in decimals.

Weaver decided to take two options before the trustees in April: $750,000 for the 150-inch; or $1 million toward the 184-inch, on condition that the University raise at least another $250,000 for it. In either case, the University would have to provide operating costs for a decade.^[44] Sproul had already obtained authorization from the Board of Regents for the $250,000 he had promised for construction and either $50,000 or $85,000 a year for maintenance of the smaller or larger machine respectively. Sproul

regarded the commitment of such sums by the regents to such a purpose as "pretty overwhelming."^[45] It remained only to await the decision of the trustees. They reviewed the opinions of the physicist and engineering consultants from Bush to Oliphant. They had a lesson in nuclear physics and its applications from Karl Compton, who had been coached in Berkeley (plate 10.1), and from Weaver, who drew on inspirational photographs of the Laboratory and its machines supplied by Cooksey. And they heard a heady peroration from their program officer. Weaver compared Lawrence's Laboratory with Bohr's institute; he recommended that the Foundation support the 184-inch project, as an "opportunity to make discontinuous change in [the] rate of progress of science;" and he extolled the "shrewd intelligence, imagination and insight, unselfishness, inspiration for young men, [and the] charm" of the man who would carry the project through.^[46] And there would be no trouble carrying it through, as the trustees learned from Jewett, now speaking as head of the National Academy of Sciences: "a matter of engineering calculation [he said] and not one of uncertain speculation."^[47]

As a further aid to their deliberations, the Rockefeller trustees felt heavy pressure transmitted through their officers from Lawrence's agents and admirers Poillon and Morris. They were not content with the prospect of a million dollars. "I am making life miserable for Warren Weaver and Raymond Fosdick," Morris had written Lawrence at the end of February. "Confidentially, we are all striving for the million dollar cyclotron under column B, and Howard [Poillon] and I are trying to jack up this limit 12 and one half percent. I really feel that all four of us are working for

you heart and soul."^[48] The quartet missed its pitch by 2.5 percent.

At noon on April 3, 1940, Weaver called Lawrence to announce that the trustees had come down 15 percent above the expected maximum.^[49]

WW: Our trustees voted $1,150,000 . . .

EL: Really, Warren, $1,150,000 . . .

WW: And with the $250,000 that makes $1,400,000, which you see is the full original budget.

EL: The full original budget. . . . Its hard to tell you how I feel. This is the most wonderful thing that has ever happened. . . . I'm coming to New York, and it will give me a chance really to explain my feelings to you. This is the most wonderful thing that one can think of in the world.

Lawrence had the feeling he was "walking on air." So did his successful agents Morris and Poillon. "You can scarcely overestimate the joyous feeling that resulted from the news," Poillon said, and indeed he had earned the right many times over to share in this tribute to the machine and Laboratory he had backed from the beginning. The munificent grant represented many things: dollars, to be sure, but also the affection, respect, and confidence in which Lawrence's fellow physicists and prominent men of business held him. As Dave Morris wrote: "This really great triumph should mean much to you in more ways than one. There was no disagreement anywhere along the whole line. Great and small, technical and lay, they all backed the PLAN and YOU. Do get full emotional satisfaction from such rare unanimity: you deserve it."^[50] According to the formal agreement, the Rockefeller Foundation and the University would put up money as Lawrence needed it in the proportion of 23:5 until June 30, 1944, when, barring "unforeseen difficulties," the machine was to have been completed.^[51]

The University immediately obtained a fifth of its commitment of $250,000 from the Research Corporation. Lawrence asked the Markle Foundation for the balance, toward which it gave $50,000 at Weaver's urging, and tried to get Westinghouse to underbid General Electric's generous offer to make the 184-inch's power supply at cost, which Westinghouse declined to do. He spent two weeks touring Wall Street with Loomis, asking for help in knocking down the price of steel and other material and equipment. Despite the pressure of war orders, which left little incentive for price concessions, Loomis and Lawrence did very well on Wall Street. The balance of the University's share of the capital costs eventually came from the federal government, in consequence of those unforeseen but foreseeable difficulties that prevented completion of the machine before June 1944. And the war also made good the shortfall in Lawrence's ideas of eluding relativity; the machine when finished in 1946 operated on a principle invented by McMillan in 1945, perhaps as a result of his wartime experience with radar.^[52]

In a public explanation of the gift, and before the unforeseen difficulties interrupted the building of the 184-inch cyclotron, Fosdick wrote: "With so much creative human talent employed in devising increasingly powerful engines of destruction it is at least some comfort to know that today in the United States work is proceeding on two of the mightiest instruments the world has ever seen for the peaceful exploration of the Universe." The 200-inch telescope and the 184-inch cyclotron would respectively open up the infinitely great and the infinitely small, alleviating "the insatiable curiosity which is the mark of civilized man." To be sure, the cyclotron would do something practical: it would produce specialized radioactive isotopes, perhaps beams of therapeutic value, perhaps even clues to the exploitation of atomic energy. But above all, "like the 200-inch telescope, it is a mighty symbol, a token of man's hunger for knowledge, an emblem of the undiscourageable search for truth which is the noblest expression

of the human spirit."^[53] This inspired gloss, which was not entirely disingenuous, marks the end of the era of private support for Lawrence's Laboratory.

Lucky Dog

The Rockefeller Foundation had heard three substantive objections to the he-man cyclotron: that relativity would cripple it; that the muse of discovery did not attend cyclotroneers; and that the Foundation would further its program in the applications of physics to biology by favoring the production of natural, rather than artificial, isotopes of the elements of living things. All these objections lost much of their force while the Rockefeller trustees pondered. The second two both collapsed with the detection of H³ and C¹⁴ , two solid discoveries that promised to give biologists tracers for the most important ingredients in organic molecules. Lawrence made much of both these products of his Laboratory. He gave the discovery of H³ pride of place in his report to the Research Corporation for 1939. "Radioactive hydrogen," he wrote, in a gloss he doubtless expected Poillon to pass on to the Rockefeller trustees, "opens up a tremendously wide and fruitful field of investigation in all biology and chemistry."^[54]

Toward the end of the dickering, in late February 1940, Kamen and Ruben called on Lawrence, then in bed with one of his colds, to present their first, flimsy evidence of the existence of C¹⁴ . "He jumped out of bed, heedless of his cold, danced around the room, and gleefully congratulated us." His ecstasy turned to outrage on learning that the report of the discovery in the Physical Review bore the names Ruben and Kamen. "He turned on me [Kamen recalled] with ill-concealed anger and demanded to know why my name and the institutional credits placed me and the Rad Lab in a position secondary to the Chemistry Department." The explanation, that Ruben thought he needed all the credit he could amass to gain tenure in a Chemistry Department not free from anti-Semitism, did not placate Lawrence, who thought the Laboratory needed all the credit it could garner to win the Rockefeller

sweepstakes. "The best of all," Lawrence wrote Weaver, in an itemization of favorable signs, "is the discovery of carbon 14 by Kamen and Ruben [!] here. . . . All cyclotrons now in existence could be usefully employed in making radio-carbon only."^[55]

The third objection—that Lawrence did not know what he was doing, that the maker of the cyclotron knew too little physics, that he had overstepped the limit set by Einstein and nature—was answered emphatically by the certifiers of the world's greatest physicists. On November 9, 1939, Lawrence received the telegram from Stockholm that responded to the recommendations of distinguished physicists throughout the world. The Swedish Academy of Sciences had decided to award him the Nobel prize in physics, "for your having invented and developed the cyclotron and especially for the results attained by means of this device in the production of artificial radioactive elements." He thus fulfilled almost to the volt the prophecy made by Jesse Beams eight years before: "With 10^–8 amps at 900,000 volts you already have a powerful tool and Boy with 20,000,000 you'll get the Nobel prize."^[56]

Lawrence was first proposed formally in 1938, by an American, a Japanese, and an Indian (who proposed a division with Fermi). The prize committee could not decide whether the cyclotron was prizeworthy and chose Fermi for his discovery of radioactive substances and the method of activation by slow neutrons.^[57] In 1939 the Compton brothers organized a campaign for Lawrence among former American prizewinners (all prizewinners have a permanent right of nomination); two of them, Clinton Davisson and Irving Langmuir, did propose Lawrence; Carl Anderson preferred Stern; Millikan did not care to exercise his franchise. The usual rationale for the nomination was, as Langmuir put it, Lawrence's "construction of the cyclotron and his studies of radioactivity that have been made possible by its use." Another ground, which

perhaps agrees better with the facts, was expressed by Livingston in a letter forwarded to the Nobel committee by Davisson. Livingston observed that many people before Lawrence had had the idea of the cyclotron. "However the idea developed," Livingston continued, "Lawrence was the first and only one to have enough confidence in it to try it out. . . . His optimistic and inspirational attitude was what convinced me it was worth working on." And thus their division of labor: "Professor Lawrence's ability as a director and organizer and his inspirational leadership amount almost to genius, but the bulk of the development was done by others."

The foregoing enumeration does not exhaust the list of Americans who proposed Lawrence for the physics prize for 1939. Two invited to nominate that year, E.F.W. Alexanderson of General Electric and the eminent surgeon Harvey Cushing, plumped for him; and Bethe and R.C. Gibbs of Cornell decided that if Lawrence did not win, they would use their invitation to nominate for 1940 on his behalf. In a few words, as DuBridge wrote Lawrence after the happy news, "there seems to have been an unanimous feeling for the past two years at least that you were the outstanding candidate among American physicists for the Nobel award."^[58] And he had powerful support in places where he was not a favorite son. The Italians—Amaldi, Fermi, and Rasetti—endorsed him unanimously, after Fermi's victory in 1938; the most influential Scandinavian physicists, Bohr and Manne Siegbahn, favored him; and even the British, or anyway those who did not think that Cockcroft and Walton had the prior claim, "would have made the award in the way the [Nobel] Committee did."^[59]

There was rejoicing in Berkeley (plate 10.2). Birge worked out that Lawrence was the thirteenth American to win a Nobel prize in science and the first to have won while employed at an American state university. The Physics Department and the administra-

tion of the University, which had reduced Lawrence's teaching load and given him money, therefore deserved a share of the honor, Birge wrote Sproul. "I think if the outside world realized more fully the handicaps under which we work, in getting and retaining men of real eminence, it also would consider the whole collection of events leading up to this award as a seeming miracle." The regents proclaimed that the prize ranked Lawrence "with the greatest scientists of the world." Lawrence knew better and graciously associated his collaborators with the honor.^[60] In turn they gave him a high-spirited party—a "jubilation"—at their favorite Italian restaurant. Aebersold provided an apt text, which the celebrants sang to the tune of "A Ramblin' Reck from Georgia Tech:"^[61]

The prexy came around to see the gadget put to test
Of course the young professor wished to show it at its best
"You may fire the thing when ready, boy," the eager prexy cried
So Lawrence pushed the switches in and quickly stepped aside.

He aimed it at the window pane and smashed out all the glass
It hit a poor old alley cat right square upon his—face
He turned it on some students and it swept them off their feet
He bombed the Campanile and he moved it down the street.

And then he bombed some common lead and turned it into gold
The prexy jumped around with joy and loudly shouted, "Hold
I am convinced the thing is good—no more I'll have to go
To the Solons up in Sacrament' to ask them for some dough.

The publicity surrounding the prize—which made Lawrence the subject and victim of the advertisements he had courted—was its most important and useful feature.^[62] As Weaver observed in his telegram of congratulations: "Some of us think they were a year or two late. But this definitive recognition is nonetheless particularly useful just now." What Weaver had in mind appears more clearly in Lawrence's letter of thanks to Siegbahn. "It was already clear

that the difficulties in the problem [of attaining 100 MeV] were no longer technical but purely financial. The added prestige to the work of our laboratory which the Nobel award brings . . . will make it possible for us to raise the large financial support for this great project."^[63] The prize, like the successful operation of the 60-inch cyclotron, would undercut those who doubted the feasibility and/or desirability of a machine rated at five times the Bethe-Rose limit and encourage foundations willing to take risks endorsed by the Nobel authorities. Lawrence understood the power of the prize to confer legitimacy on new fields or doubtful adventures; in a report written in 1938, he had pointed out the useful advertisement provided by Nobel laureate Joliot's decision to build a cyclotron.^[64] Several successful fund-raisers made the same observation as Weaver, among them Walter Alvarez, Cottrell, and Poillon.^[65] And Lawrence spread the message widely in his answers to the several hundred letters and telegrams he received; to more than fifty of these correspondents he excused the honor, and opened his thoughts, by observing that the cyclotron would be the beneficiary of his placement among the demigods of science.

The size of the projected cyclotron grew along with its prospects in the nourishing light of the Nobel prize. The plan for a 2,000-ton machine with 120-inch pole pieces, considered, at a cost of $500,000, to be at the edge of the attainable in October 1939, swelled to a dream of a 5,000-ton atom smasher with poles of 205 inches. Answering Bohr's congratulations of November 14, Lawrence referred to a machine of 3,000 tons; answering G.W.C. Kaye's on December 30, he mentioned his Christmas wish of 5,000.^[66] It is very likely that without the Nobel prize Lawrence would not have had the boldness to have doubled his design and his costs. The 184-inch machine owes its existence as much to the prize givers of Stockholm as to the exertions of Warren Weaver.

The award to Lawrence honored not only the invention of an instrument but also the creation of the environment necessary to exploit it. What the Nobel committee had in mind appears best from the award letter quoted earlier: they were impressed by the invention and development of the machine and "especially" by its application to the production of radioisotopes. The same emphasis appears in the committee's report to the Swedish Academy of Sciences, which dwells on output figures: the cyclotron easily makes artificial sources of gamma rays equivalent to a hundred grams of radium and gives a hundred times the neutrons from a kilogram of radium mixed with beryllium. Reference to production does not occur, however, in the official citation ("for the invention and development of the cyclotron and for results obtained with it, especially with regard to artificial radioactive elements") or in Bohr's statement of Lawrence's achievement ("for the extraordinarily great contribution to the study of the reactions of atomic nuclei that he has made by construction of . . . the so-called cyclotron").^[67] The official citation and Bohr's recommendation suggest that Lawrence himself made some notable contribution to radiochemistry or nuclear physics with the help of the cyclotron. Indeed he did: the cyclotron laboratory. But he himself had not uncovered much new about the nucleus. Had the Nobel committee wished to distinguish inventors of an accelerator who had made a fundamental discovery with it, they did not have far to look. Cockcroft and Walton fit the description and had the additional advantage over Lawrence of priority. And their work was considered prizeworthy. Otto Schumann of Munich nominated them for 1935; Rutherford and Fowler did so in 1937; Chadwick took up their cause in 1938 and 1939; and the Nobel committee agreed that both their "pioneering" splitting of the nucleus and their exact determination of atomic masses had "a special importance." In 1951 they did share the prize "for their pioneer work on the transmutation of atomic nuclei by artificially accelerated atomic particles."^[68]

In preferring Lawrence to Cockcroft and Walton, the Nobel committee on physics went against its own arguments and precedents, although in a direction of which Nobel would have approved. Lawrence's was the first award for the development of an instrument for physics if we leave C.T.R. Wilson's prize of 1927 out of the reckoning. Efforts to give prizes for hardware alone had subsequently failed. In 1935 Walther Nernst proposed Hans Geiger. The Nobel committee thus evaluated his candidacy: "One can say that the Geiger counter together with the prizewinning Wilson chamber are the experimental instruments that have made possible the brilliant discoveries in nuclear physics. . . . But Geiger himself has not taken any noteworthy part in the work that led to these important discoveries."^[69] A campaign of many years on behalf of Aimé Cotton, who built a very large electromagnet (100 tons, 75 cm pole tips, 64 kG) for the Paris Academy of Sciences and used it for important spectroscopic studies, likewise did not convince the committee. Pieter Zeeman (prize of 1902) might compare Cotton's magnet with Aston's mass spectrograph or the Rowland grating, and insist that progress in physics comes equally from ideas and from machines; C.E. Guillaume (prize of 1920) might declare Cotton's magnet precious and its research potential prizeworthy; Pierre Sève of Marseilles might demand a reward for "the construction of an instrument unique in the world . . . , the Laboratoire du Gros Electroaimant, where many workers under [Cotton's] direction have already obtained extremely important results in all branches of physics;" but the committee rejected it all, on the ground that Cotton had not made any discovery with his magnet important enough to deserve a Nobel prize.^[70]

The relaxation of this condition in Lawrence's favor owed much to the progress and popularity of nuclear physics and to the scale of the machines and laboratories it required. One of Cotton's last nominators, C.E. Guye of Geneva, realized that, if the Nobel committee went for machines, they would probably prefer those of nuclear to those of atomic and molecular physics.

The only hope of the old school, he thought, was to slip in before the committee could decide which of the inventors of accelerators or discoverers of new particles to reward first. It was in connection with the confusion and profusion of claimants that the eventual need to pick an accelerator physicist was first expressed in the correspondence of the Nobel committee. Dick Coster of the University of Groningen, writing in December 1933, suggested that the "artificial disintegration of nuclei by fast protons" might prove deserving; two years later Caltech's Richard Tolman took advantage of the throng—Lawrence, Lauritsen, Van de Graaff, and Cockcroft and Walton—to dismiss all in favor of Caltech's Anderson.^[71] By 1938 Lawrence had outdistanced the rest in the building not only of machines but also of laboratories.

An instructive evaluation of the situation as it appeared to three nominators that year is preserved in the correspondence of O.W. Richardson (prize of 1928), who liked neither big nor nuclear physics. Bohr (prize of 1922) talked over options with him in December 1938. "After discussing a number of distinguished names, to several of which I would have been prepared to offer a measure of support, he finally decided on the combination of Lawrence and Kapitsa [another big machine, big laboratory man]. Well, what has Lawrence done? invented an instrument which would have been more or less obvious to anybody unfamiliar with the difficulties of experimental technique, made it to work, and done nothing with it, except to incite a large number of very able experimental physicists all over the world, unsuccessfully, to emulate his efforts. The wiser of them seem to have handed this trouble over to their students, but it is doubtful if that will help their generation! As for Kapitsa!!!" The addressee of this blast, G.P. Thomson (prize of 1937), who did some nuclear physics, returned the suggestion of Cockcroft without Walton. Bohr had also considered a prize for Cockcroft alone, but all recognized its unacceptability. In the end Bohr dropped Kapitsa, and Richardson and Thomson nominated E.V. Appleton, whose investigations concerned the upper atmosphere.^[72]

Appleton had to wait until 1947. The Nobel committee was infatuated with nuclear physics and its machinery and willing to reward discoverers of the one and inventors of the other. Oliphant read Lawrence the significance of the committee's decision in 1939: "It is extremely encouraging to find that the Nobel Prize Committee, in common with many other authorities, is now recognizing the tremendous importance of technique in scientific investigations. . . . The technical side of the subject is now recognized as equally important with advances that follow from the use of these techniques, and more important, I hope, than the theories that endeavor to explain them. . . . It is certain that you have no difficulty now in raising funds for your 'father of all cyclotrons.'"^[73]

German submarines kept Lawrence from the prize giving in Stockholm. The citation and medal were sent to the Swedish consul in San Francisco and presented at a ceremony on the Berkeley campus presided over by Sproul. Birge gave a speech reciting the accomplishments of Lawrence and the Laboratory. It was the evening of February 29, 1940. At the end of his prepared remarks, Birge announced the discovery of C¹⁴ to the crowd that filled the hall. "On the basis of its potential usefulness," Birge said, with exaggeration appropriate to the hour, "this is certainly much the most important radioactive substance that has yet been created."^[74] Lawrence's reply carried two examples of his most effective technique. For one, he let Birge say what he himself wished to say without incurring any obligations: "As [Birge] has indicated, there are substantial prospects that [the next cyclotron] will be the instrument for finding the key to the almost limitless reservoir of energy in the heart of the atom." For another, he did not miss the opportunity for fund-raising. "It goes without saying that such a great recognition at this time will aid tremendously our efforts to find the necessary large funds for the next voyage of exploration into the depths of the atom." "[This] very considerable financial problem . . . we must now hand over to President Sproul."^[75]

As we know, description of the cyclotron had always been a parade ground for military metaphors. The additional possibilities offered by the source of the Nobel prize carried the "University Explorer" to heights truly and doubly inspired. "Ernest Lawrence," he declared, "has discovered a blasting technique far more potent than anything Alfred Nobel ever dreamed of." R.W. Wood, an elder statesman of physics, improved the metaphor into prophecy. He wrote Lawrence: "As you are laying the foundations for the cataclysmic explosion of uranium (if anyone accomplishes the chain reaction) I'm sure old Nobel would approve."^[76]

2—
New Jobs for Cyclotroneers

On June 27, 1940, four men representing together the nation's best research universities and technical schools, its largest private foundations and most advanced applied science, and its most prestigious scientists obtained from Roosevelt a commission to set up a National Defense Research Committee (NDRC) under the authority of the forgotten Council of National Defense of World War I. These pooh-bahs of science and technology were Vannevar Bush, accomplished electrical engineer, former vice president of MIT, head of the Carnegie Institution, head of the National Advisory Committee for Aeronautics; Karl T. Compton, physicist, president of MIT, trustee of the Rockefeller Foundation; James B. Conant, chemist, president of Harvard; and Frank B. Jewett, electrical engineer, head of Bell Labs, president of the National Academy of Sciences.^[77] All four have appeared in our pages as promoters of cyclotrons. They were to recruit from the corps of cyclotroneers many of the men who would direct the major wartime laboratories. They knew that cyclotroneers understood how to work at the borders and edges of science and technology, and how to work in teams: cyclotroneers and their fellow travelers did not fear big projects, did not disdain to scrounge when necessary, did not insist on perfection or protocol. They were ideal people for crash programs.

In the Ether

In October 1940 Alfred Loomis, who had been appointed head of microwave work under Karl Compton's division of NDRC, called members of his committee to meetings at his home and laboratory in Tuxedo Park, New York. Lawrence was among them. They agreed that the technology made possible, and the emergency recommended, the establishment of a central national laboratory to do "anything and everything that was needed to make microwaves work."^[78] To confuse the enemy, and in honorific obfuscation, the center, located at MIT, took the name "Radiation Laboratory." It invented or perfected many sorts of radars operating at wavelengths around and below 10 cm. In devising these most important aids to detection and navigation of ships and planes, blind landings, gun laying, and so on, the MIT Radiation Laboratory drew twice over on the experience of cyclotroneers. For one, it acquired appropriately socialized staff with relevant technical knowledge. ("If all the energy which has gone into nuclear physics since 1932 were turned onto this problem [the air menace]," Cockcroft had predicted, "it would be solved.") To head the new Rad Lab, the Microwave Committee chose Lee DuBridge of Rochester, whom Lawrence rated as the most desirable laboratory leader of his generation, an excellent physicist, administrator, and team player, the perfect cyclotroneer. As DuBridge later recalled, with an exaggeration that illustrates the strength of the brotherhood he represented so well, "our whole initial group at the MIT laboratory were the cyclotroneers—all had been associated with Ernest [Lawrence] either remotely or intimately." A meeting on applied nuclear physics in Cambridge around November 1, 1940, arranged by Livingston and attended by 600 physicists from all across the country, provided a perfect recruiting ground.^[79]

Table 10.1 lists the ten cyclotroneers engaged during the first three months of the MIT Rad Lab's operations. One came and stayed as director; six entered as or quickly became group leaders; five left as division leaders (there were seven R&D divisions in all); two ended on the laboratory's steering committee. Lawrence's devotion to Loomis and conviction of the importance of radar caused him to send his very best men, Alvarez and McMillan, and his expert on radio frequency systems, Salisbury. McMillan, who left MIT soonest, worked on field tests of an interception system against aircraft and on airborne radar for detecting and homing on ships. Salisbury directed efforts in his specialty. Alvarez, who stayed the longest of the Berkeley group, moved furthest. After helping to develop radar for attack planes, he invented a system to guide approaching aircraft from the ground and directed work on other aids to detection, navigation, and identification.^[80] Another man from Berkeley, Lauriston Marshall of the Department of Electrical Engineering, had a career at the MIT laboratory similar to a cyclotroneer's: he came to work on magnetrons, rose immediately to group leader, then chairman of the Ship Committee and director of the British Branch of the Radiation Laboratory, and closed the war as head of the Laboratory's Operational Research Section attached to the Headquarters of the U.S. Air Force in the Pacific.

Marshall represents the second way in which accelerator laboratories contributed essentially to radar. In the late 1930s, he helped transform Sloan's latest piece of cyclotronics into a generator of radio waves at a frequency and power suitable to radar. This was a tube designed to remove the obstacle encountered in the early 1930s to the development of the Wideröe linac into a useful tool in nuclear physics. To recall the old difficulty, a Wideröe machine for protons of reasonable size and ambitious energy would require a power oscillator working at a wavelength of two or three meters, about an order of magnitude shorter than commercial tubes could easily handle. As he remembered his

tinkering to improve their performance, Sloan "just pushed triodes and tetrodes to high power, high frequency, beyond anything the cyclotron needed." By May 1940, he and Marshall had a tube that oscillated at 50 cm and with great power—some 2,500 watts. Cooksey reported this news to Loomis, who had not waited for the NDRC to begin to push work on microwave electronics. Loomis was elated.^[81] The cause of elation: the size of radar sets diminished, while the detail of the objects they could see increased, with decline of wavelength down to about 1 cm, where atmospheric absorption begins to make trouble. The Sloan-Marshall tube, or "resnatron," held promise as the fast-paced heart of a powerful, centimetric microwave transmitter for airborne use.^[82]

As soon as he became head of the NDRC's microwave work, Loomis asked Lawrence to take responsibility for the further development of the resnatron "in a big way," as "the major war research of the University [of California]." The Research Corporation, which had patented the resnatron, gave $4,500; Loomis provided $1,500 from his deep pocket and a promise of $20,000 of NDRC funds. Lawrence agreed to sail "full speed ahead" with the help, if necessary, of moneys diverted from the 184-inch cyclotron.^[83] The good ship resnatron was then not the only centimetric pulser at sea in the Bay Area. Loomis had asked Lawrence to send Sloan and Marshall to San Carlos, California, to join their work with efforts under way there to perfect something called the klystron.^[84] Like the resnatron, the klystron resulted from efforts at a university—in its case Stanford—to overcome the frequency limit of commercial oscillator tubes. Stanford wanted a very powerful x-ray tube, no less than 3 MV, but did not want to pay for it. Considering strategies in 1934, William Hansen, an instructor in Stanford's physics department, thought to set up oscillations in a

cavity, a transmission line, as it were, with no inner electrode. The thing itself is simple enough in principle and, moreover, of convenient size: a cube 10 cm on a side resonates at a wavelength of 14 cm. It may be driven by a transmission line that creates an appropriate magnetic field within a loop coupled to the cavity. A struck bell is a crude, but serviceable, analogy. In 1937 Hansen had a visionary plan to drive electrons to 100 MeV within his "rhumbatron," as he called his cavity resonator. He sent off a report, in the usual way, to a professional journal; but Stanford's administrators, sensing something big, made him hold it back for a year while they made sure of the commercial possibilities.^[85]

The rhumbatron transformed into the klystron when Hansen's former roommate, Russell Varian, discovered a novel way to control electrons. That was in the summer of 1937. Varian and his brother Sigurd, a former commercial pilot, then worked with Hansen as unpaid research associates on the design of a microwave device for navigating and detecting airplanes. This purpose had seized Sigurd Varian, who knew the dangers of commercial flying and could imagine those of enemy action. The klystron (fig. 10.1) consists of two reentrant cavities C₁ and C₂ , separated by a drift space RS. A beam of electrons from the tubular cathode at the top accelerates under the dc voltage between M and the grid P, whence they drift through the field-free region PQ and into the neck of the "buncher" cavity C₁ . Between Q and R they suffer an oscillating field created through the loop F. This experience causes them to collect into bunches in the drift space RS: an electron that crosses just before the oscillating field rises to zero will be slowed; one that crosses when the field goes positive will speed up. As they drift, the retarded early electron, the on-time electron, and the hurrying late electron will congregate. The neck of the "catcher" cavity C₂ stands where the density is greatest and the induced field has the proper phase to oppose the motion of the bunches (and so derive energy from them). The congregations pass at the frequency of the buncher, thereby exciting very strong

[Full Size]

Fig. 10.1
The klystron as first described by the Varian
brothers. R. Varian and S. Varian,  J1 appl. phys. ,
10 (1939), 324.

oscillations in the tuned catcher. The deceleration of the bunches in the catcher prevents them from overcoming the opposing voltage between T and U, a fact recorded by the meter at A. The whole business rests in a vacuum. By August 1937 a cardboard version coated with copper foil was working at l = 13 cm. The Sperry Corporation undertook to develop it for aircraft detection.^[86] This was the line of research to which Loomis wished to couple development of the Sloan-Marshall tube. As it happened, the Varians and Hansen went to Sperry's research laboratory in New York, where the klystron developed into a versatile circuit element. Hansen spent much of his time in the East lecturing about microwaves at the MIT Radiation Library.

Neither Berkeley's nor Stanford's entry into what had become a worldwide race for a transmitter of centimetric radar could generate the necessary power in 1940. The device on which the MIT Rad Lab was raised later in the year had much in common with them, however; it came from a university laboratory much concerned with particle accelerators and exploited the bunching principle introduced by the Varian brothers. This "cavity magnetron" came from Oliphant's institute at the University of Birmingham. Its inventors, J.T. Randall and H.A.H. Boot, arranged an anode consisting of a thick ring scalloped by cavities around a central cylindrical cathode (fig. 10.2). Electrons move toward the anode under a dc potential and a magnetic field strong enough to bend them all back to the cathode. When the cavities resonate under an external impulse, their radio frequency fields, leaking into the anode space, slow some electrons enough that the magnetic force on them (which is proportional to their velocity) no longer suffices to return them to the cathode. Electrons so affected bunch together and add energy to the resonant cavities as they pass en route to the anode. In effect, the cavity magnetron is to the klystron what the cyclotron is to the linac.^[87]

[Full Size]

Fig. 10.2
The cavity magnetron. Modulation of the radial electrostatic field between
the cylindrical cathode and the concentric anode-block by a high-frequency
field leaking from the cavities causes some of the electrons to bunch.
Terman, Elec. rad. eng. , 689.

The cavity magnetron was the centerpiece of many ingenious devices that a British technical mission under Henry Tizard, which included Cockcroft and Fowler, showed American military and scientific men in September 1940 in the hope of returns in kind. The magnetron made an impression. The Naval Research Laboratory then had a klystron transmitter operating at 10 watts. The British cavity magnetron gave a thousand times as much power at the same wavelengths. Cockcroft and E.J. Bowen explained its operation in detail at a gathering at Loomis's estate at the end of September. Two weeks later, on October 12–13, the Microwave Committee met with Bowen and Cockcroft, again at Tuxedo Park. They decided to copy Britain in entrusting development of radar to interdisciplinary teams of academic scientists and engineers. Lawrence ran to Loomis's telephone. "During the next few weeks [as Bowen recalled] he was to telephone every physicist of consequence in the United States." A month or so later the MIT Rad Lab, "a central laboratory built on the British lines, was in operation."^[88]

The magnetron did not end the war for the resnatron. After Marshall threw in his lot with the MIT group and Sloan at last won his Ph.D. in Berkeley, the new doctor took his tube for treatment at Westinghouse's Research Laboratory in Pittsburgh. There it waxed exceedingly robust. Westinghouse built forty-two of the final design, each of which weighed 500 pounds. These fat resnatrons knocked out everything on the air. They were of first importance in jamming German radar on D-Day.^[89]

Elsewhere

In August 1941 Lawrence pulled McMillan from the ether at MIT and dropped him in the water at San Diego. A new laboratory, run jointly by the navy and Jewett's division of NDRC, was being organized there under a contract with the University of California. Its director, Vern Knudsen, professor of physics at UCLA, had built up a small, strong group in applied acoustics with support from the movie industry, for which he had built

sound stages. But neither Hollywood nor UCLA had given him work on the scale on which he was now to perform: to study the physics of underwater sound, especially means to measure its spead precisely; to improve or design new methods of underwater detection and evasion appropriate to conditions in the Pacific; and to develop training manuals and devices for operators with very little technical knowledge. Knudsen turned for help to the physicist at the University of California most experienced in big operations. Lawrence "came down [to San Diego], spent time with us . . . , and participated in formulating our research program."^[90]

Perhaps most usefully, Lawrence furnished McMillan, much to the irritation of the leaders of the MIT Rad Lab. With the breadth of view and ingenuity that had made him so valuable a member of Lawrence's Laboratory, McMillan contributed to all phases of the work at San Diego. He devised an echo repeater, "Beeping Tom," the first contribution from Knudsen's shop accepted by the navy, which simultaneously freed submarines from service as training targets and sonar operators from the need for practice at sea. He was particularly effective, according to Knudsen's successor, G.P. Harnwell, "in criticizing and directing the program of the laboratory in the fundamental investigations assigned to it."^[91]

The first group of cyclotroneers entirely mobilized by NDRC was Tuve's force in the Carnegie Institution. In September 1940 they put aside their Crocker clone for "nights and days with defense work." They had taken on the task of knocking enemy planes from the sky. At the time, conventional wisdom rated very highly an antiaircraft system that could hit one plane in 2,500 shots. Under this mild inhibition, the Luftwaffe could bomb and strafe without much worry about guns on the ground. Following conversations between Lauritsen and Tuve and the navy's Bureau of Ordnance in August, the NDRC contracted with the Carnegie Institution for "preliminary experimental studies on new ordnance

devices." Tuve learned about what the British had done from Cockcroft and Fowler and set out to make a fuse activated by radio that would detonate near its target. Everyone working on the Carnegie cyclotron—Tuve himself, L.R. Hafstad, R.B. Roberts, G.K. Green, and Philip Abelson—went to work to make a radio sufficiently small and tough to fit into the space of an ice cream cone and withstand the inspiring forces—some tens of thousands of times greater than the force of gravity—exerted during firing on a five-inch shell. The Carnegie's administration, however, preferred to see its expensive cyclotron brought to completion; and, in a gambit we shall see repeated, requested Tuve's men to return to their machine as a measure of national defense. He rejected the request as selfish and the aim as ineffectual. "Representatives of every Cyclotron Laboratory in the country have individually asked us what they could use their cyclotrons for in defense work and no valid ideas have been forthcoming. . . . It is easy for an enthusiastic entrepreneur to make a casual remark that a cyclotron can be classified as a defense project. If the Institution staff had no other defense work of clearly greater urgency, this would be our position [too] as it was previous to August."^[92]

Tuve did find a little war work for his new three-story cyclotron laboratory. He and his associates dropped miniature radio tubes from its roof onto the concrete driveway below as a test of fragility. Enough survived to prompt contracting with their makers. When he declared the worthlessness of cyclotrons for national defense, Tuve had three sorts of tiny tubes that could withstand firing in a five-inch shell. By May 1941, a basic design for a fuse triggered by radio was in hand; but premature firings and duds troubled its tests during the summer. The bombing of Pearl Harbor brought new urgency and manpower to the project and its relocation to a large garage in Maryland. This new facility, dubbed the Applied Physics Laboratory of Johns Hopkins University, which contracted for its operation, improved reliability and invented an ingenious mechanism to prevent unintended explosions. Late in 1942, 4,500 shells, perfectly safe to their users,

reached the Pacific Fleet. In their first engagement they brought down a Japanese bomber in four shots. The project compared in importance, success, and expense with the making of the atomic bomb.^[93]

One of Bush's first prizes as chairman of NDRC was the Advisory Committee on Uranium. This body, chaired by Lyman J. Briggs, director of the National Bureau of Standards, had resulted from the famous letter alerting Roosevelt to the possibility of nuclear weapons, signed by Einstein but composed by Szilard and his fellow Hungarian refugees Eugene Wigner and Edward Teller. Briggs was no cyclotroneer. His committee, which had the frequent optimistic advice of Szilard, had not accomplished much by May 1940, after seven months of existence. The delay and the apparent indifference of the armed services to the opportunities opened by fission made the refugees impatient and, perhaps, self-important. "We ought not to try to save the country for the Americans [Wigner wrote Bethe], but to push them to save themselves."^[94] Without their pushing, however, a typically American instrument—a body of self-moving private citizens appointed by the president to mobilize scientists within and outside government—had come into being that would vitalize the uranium project.

The citizens, the founders of NDRC, had been drawn into the business of the uranium committee a few months before the creation of their organization. The news from Columbia in March 1940 that, as predicted by Bohr, U²³⁵ was the party guilty of fission by slow neutrons, directed attention to the importance of the separation of uranium isotopes. In April, at the meeting of the American Physical Society in Washington, Beams, Fermi, Nier, Tuve, and Urey decided that Beams's ultracentrifuge offered the best hope for separation in kilogram amounts. In May, Beams, Cooksey, Karl Compton, and Lawrence reached a similar conclusion. Compton notified Bush (as head of the rich Carnegie

Institution), who already knew about Beams's work from Tuve, whose department had deliberated purchasing a centrifuge for biological work. Tuve had rated Beams's model, which cost $5,000, as the best available for separating isotopes (he had tracers in mind) and biological materials. Tuve now recommended to Bush that the Carnegie Institution give Beams $10,000 to determine whether U²³⁵ could be spun free from U²³⁸ . In Tuve's opinion, centrifugation offered "the only hope of separating the isotopes of any but the light elements in quantity." Neither thermal diffusion nor the mass spectrograph (electromagnetic separation) seemed competitive to him.^[95]

Bush agreed to provide money and call meetings. The Naval Research Laboratory had been helping Beams with supplies and apparatus at a level estimated by Tuve at $2,000 a year. After Bush's intervention, the army and navy put up $100,000 to study the separation of isotopes, primarily by centrifugation, but also by thermal liquid diffusion, as proposed by Carnegie's Abelson, then recently returned from Berkeley and work on element 93.^[96] A possibility that Tuve had not considered explicitly, diffusion of uranium hexafluoride gas through tiny holes in a "barrier," which would slightly enrich the lighter isotope, appealed to Urey and others at Columbia, who obtained money from NDRC in the winter of 1940/41 to follow it up. The runaway favorite in July 1941, as judged by a budget then proposed by Briggs's committee, was Beams's centrifuge ($95,000); Columbia's gaseous diffusion ($25,000) came a poor second. At just this moment, however, the British intervened as decisively as they had in the fall of 1940.^[97]

For a year and a half, Chadwick, Cockcroft, Oliphant, Thomson and other leading British physicists knew that a bomb might be made from 10 kg or less of separated U²³⁵ . The relevant

considerations had been put forward in February 1940 by the émigrés O.R. Frisch (Cambridge) and Rudolph Peierls (Birmingham), who assumed, among much else, that fast neutrons as well as slow ones could cause fission in U²³⁵ . "From rather simple theoretical arguments," they wrote, without arguing, "it can be concluded that almost every collision produces fission and that neutrons of any energy are effective." This was a capital point: a slow neutron bomb would be more likely to fizzle than to devastate. And where procure the U²³⁵ ? Frisch and Peierls suggested gaseous thermal diffusion. Another émigré, Franz Simon (Oxford), showed that diffusion through a barrier could do much better. In his optimistic calculations, completed in December 1940, a plant covering forty acres and employing 1,200 people could turn out 1 kg of 99 percent pure U²³⁵ in a day. During the first six months of 1941, these prophecies drew strength from rough measurements by Tuve's group, which confirmed the fundamental hypothesis of fast-neutron fission on a sample of U²³⁵ provided by Nier. Peierls exulted: "There is [now] no doubt that the whole scheme is feasible (provided the technical problems of isotope separation are satisfactorily solved)." The official report of the British uranium committee (called the MAUD Committee) of July 1941 endorsed and refined the original Frisch-Peierls memorandum: twenty-five pounds of active material, a gaseous diffusion plant costing £5 million, a bomb deliverable at the end of 1943 equivalent in destructive power to 1,800 tons of TNT.^[98]

The MAUD report changed American thinking. Although everybody had known that a chain reaction, if achieved, might make possible a nuclear explosive, Briggs's uranium committee did not have a bomb as its goal. Looking back with the greater wisdom of 1943, Fermi recalled that he knew of no one working with either fission or element 94 in the United States who appreciated their potential as explosives until the spring (or, better, the early summer) of 1941. Ignorance of British thinking was not the reason for this devaluation. Oliphant had written Lawrence in May 1939 that the British defense authorities insisted on looking

into the possibilities of a bomb, however remote, "as there are rumours that great developments have taken place recently along these lines in Germany." Lawrence, conceding the possibility, had asked "Segrè and some of the other boys" to see whether they could fission lead or bismuth. Typically, he saw neither a danger nor the likelihood of imminent success, but an entrepreneurial opportunity. "This sort of thing is another reason why the British government should come forward with generous support of nuclear physics."^[99] Nor did disclosure of the Frisch-Peierls report by the Tizard mission inspire Lawrence or other leaders of American nuclear physics to set a high priority on making bombs. Cockcroft thought them overly skeptical about military applications and overly fascinated with the possibilities of nuclear power.^[100] But then Britain, not the United States, was at war.

The pace of the Briggs committee exasperated some of its members, particularly Urey, and busy outsiders like Lawrence. In March 1941 Lawrence managed through Karl Compton to have himself assigned by a reluctant Bush—who did not like being pressured—to the post of temporary consultant to Briggs. Lawrence obtained a modest increase ($2,000) in support of the Laboratory's work on elements 93 and 94 and a contract to Nier for 5 mg of U²³⁵ . His role was that of gadfly; he did not urge a change of program but greater vigor and less secrecy in pursuing the self-sustaining pile.^[101] At the instigation of Briggs, Bush asked Jewett to convene a committee of the National Academy of Sciences to evaluate the uranium program. Jewett appointed A.H. Compton, Coolidge, Lawrence, John Slater of MIT, and John Van Vleck of Harvard. Their report, finished in May, did not emphasize a bomb; it was vague and uplifting, in the style of Lawrence's requests for major funding. The uranium project should be supported for the general significance of achieving a chain reaction and for the importance of even a moderate separation of uranium isotopes; if successful, the project might produce,

in order of military importance, radioelements in sufficient quantities to poison enemy territory, power plant for submarines, and a bomb, the last unlikely before 1945.^[102]

Bush and Conant then knew about British hopes for a bomb, which Conant had learned of during a sojourn in London in the early spring as liaison between NDRC and British defense authorities. He and Bush dismissed the NAS report as too vague on bombs and too fanciful on power. They asked for another. Jewett added two engineers to the committee. Its report, of 11 July, did not differ significantly from its predecessor's. Conant inclined to squelch the project. No one seemed to know much of the MAUD report or to take it seriously. Lawrence heard about it in September 1941, not from Briggs, who appears to have kept the report secret even from himself, but from Oliphant, on tour of American laboratories engaged in radar and other war work. What had been missed in the United States, judging from a letter from Coolidge, who had chaired the NAS committees, was the connection between fast-neutron fission, ten-kilogram explosives, and practical gaseous diffusion. Oliphant raised Lawrence's enthusiasm for nuclear bombs. Oliphant thought that 10 kg of pure U²³⁵ might be within reach, perhaps by cyclotronics. And there was also element 94, which the Laboratory had shown to be fissionable and MAUD had mentioned as an alternative, if unlikely, explosive.^[103] At the end of September 1941, just after meeting with Oliphant, Lawrence attended the fiftieth anniversary celebrations of the University of Chicago. There he met with Compton and Conant and urged that a new NAS committee be empanelled to consider the uranium project in the light of the MAUD report.^[104]

The illumination from London came just after Bush had reorganized and extended his empire. On June 28, 1941, he took over the directorship of a new agency, the Office of Scientific Research and Development (OSRD), which gave him responsibility for development of instruments of war as well as for research of military interest, authority to coordinate the efforts of various agencies, and immediate access to the president. Conant took the chairmanship of NDRC and Briggs remained as chairman of the uranium committee, which Bush raised to an independent unit, "S-1," of OSRD. He and Conant followed Lawrence's and others' promptings and returned to the NAS to ask for a new review with emphasis on the U²³⁵ bomb and the gaseous-diffusion plant. While the new committee deliberated under the chairmanship of A.H. Compton, Bush conferred with the president. He left the White House on October 9 with authority to expedite research on nuclear weapons in every way possible short of the construction of production plants. Compton's committee, which included Lawrence and Oppenheimer, endorsed the British findings, with some qualifications that proved wrong. Oppenheimer expected that 100 kg of U²³⁵ would be needed for a bomb. The committee thought that centrifugation might work. They raised the cost of separation to $100 million.^[105]

On December 18, less than two weeks after Pearl Harbor, the complete S-1 section met at the National Bureau of Standards. It was time for a crash program. And to let contracts. Lawrence spoke up, immediately and eloquently, for study of electromagnetic separation on a large scale. The committee immediately recommended a sum of $400,000. It was easier than dealing with the Rockefeller Foundation.^[106]

3—
New Jobs for Cyclotrons

Machine Work

As Tuve observed when shelving the almost finished Carnegie cyclotron in favor of defense work, many other directors of cyclotron laboratories were imagining how their instruments might be commissioned in the war effort. Those with half-built machines worried that otherwise they would not be able to acquire needed material; those with functioning production machines wanted to keep their staffs together and their clients supplied. But what purpose central to the national defense could a cyclotron serve? In the fall of 1939, J. Stuart Foster, casting about frantically for arguments to go forward with long-laid plans for a cyclotron at Toronto, proposed radioactive labelling of foods, metals, and strategic materials, to discover what was being shipped to enemy territory, and of documents, to detect them when stolen; radioactive beacons, to demarcate combat zones, batteries, and so on. Lawrence's reply to Foster's fancies suggests that he had not thought about military uses of his invention. "It is difficult for me to suggest concrete practical applications of the cyclotron in warfare, but it seems to me there are possibilities along the lines you have suggested."^[107]

As late as June 1941, directors of cyclotron laboratories not privy to the doings of the uranium committee saw only mundane uses for their equipment. A.L. Hughes, of Washington University in Saint Louis, whose cyclotron neared completion, to cyclotron headquarters: "I suppose that Defense application of the cyclotron falls into two classes, the production of radioactive yttrium as a substitute for radium in the examination of castings and the production of tracer elements to help chemists solve their problems." Lawrence replied encouragingly. Hughes's machine got its first beam on December 10, 1941, just after Bush and Conant had decided to pursue bombs made of U²³⁵ and perhaps also bombs of element 94. Washington's deuteron beam was very large, almost 0.5 mA. It went to work producing samples of plutonium, in

which it outdid the Crocker cracker. News gets around. At the end of December, A.C.G. Mitchell of Indiana, who had inquired over a year earlier for defense work on his cyclotron to keep Kurie and Laslett, asked Lawrence whether there might now be a "possibility that we could get a project at Indiana to use our magnet for a defense job?"^[108]

Karl Compton, a man very much in the know, tried to solve the financial problems of the MIT and Harvard cyclotrons and to further the purposes of OSRD by having them declared "stand by defense group[s]." He arrived at this strategy in November 1941, after discussion with Lawrence. Compton's reasons: both laboratories needed high-priority items for supplies; both faced the breakup of their groups unless their members could "feel that they are engaged on recognized national defense work;" and lack of money. In fact, the Harvard cyclotron had received a top priority rating in August 1941, along with a contract from the NDRC to make radioisotopes for other NDRC projects; but no requests had come for over seven months.^[109] Harvard got a little business—some radiosilver, some radioarsenic—in February 1942, following a directive from NDRC to use Harvard rather than Berkeley unless "very active material is required." Insufficient demand closed it down, all set up; in which condition it was later carted to Los Alamos, where it saw important service in fast-fission work under the command of Robert Wilson.^[110]

The Berkeley cyclotrons early entered into business relations with the NDRC. A contract for production of miscellaneous isotopes existed by January 1941. It supported five research assistants. The Laboratory charged the government $25.25 an hour for

overhead computed at 50 percent of direct costs. For a time in the spring, the machine ran 24 hours a day (it then dropped back to a more normal 12) to supply other NDRC contractors and the usual internal and external users. These orders could mount up. In the fall of 1941, the Laboratory billed $2,700 for 104 hours of cyclotron time to make 500 µCi of radioiodine and 30 mCi of radioarsenic for experiments at Caltech.^[111] The contracts also provided new equipment for chemical separations, mechanisms for remote handling of hot isotopes, and so on, permanent gains from evanescent products. Kamen oversaw most of the production, under "terrific tension."^[112]

The NDRC also picked up the cost of the work on element 94. Early in January 1941, Seaborg prepared at Lawrence's request an account of bombardment time and materials expended. He understood the purpose: "I believe that he is considering the possibility of having the government finance this work as an official project." In accounts rendered on March 11, 1941, $835 was charged to making element 94 by deuterons and $8,310 to the test of its fissionability by slow neutrons, exclusive of salaries. By far the largest item in both cases was cyclotron time, 315 hours completed or estimated, most of it at the 60-inch.^[113] As we know, Lawrence acquired further support through the uranium committee when he advised Briggs later that March. The demonstration in May by Kennedy, Seaborg, Segrè, and Wahl that 94²³⁹ fissions with slow neutrons and the follow-up in July by Segrè and Seaborg, which showed that it does so with fast ones as well, and much more readily than U²³⁵ , brought a good deal more from the NDRC, some $21,500.^[114]

The demonstrated fissionability of 94²³⁵ with fast neutrons confirmed its candidacy as an explosive. It might therefore appear odd that the third, and definitive NAS report commissioned by Bush, the report of November 1941 promoted by Lawrence, did not mention 94. But that was to follow the lead of Bush and the British, who had considered 94 chiefly in relation to a power generator. Joseph Rotblat of Chadwick's group at Liverpool had guessed at the fissionability of 94 in June or July 1940 and Bretscher had done the same by November, reasoning from the theory of Bohr and Wheeler. To go further, Bretscher told the MAUD Committee, he would need a sample procurable only at Berkeley; and he agitated "whether we should ask for facilities to enable us to work there."^[115] When Oliphant visited the Laboratory in September 1941, he saw what could be accomplished with good funding, practiced investigators, and a big cyclotron. "When I saw at Berkeley the work going on there on 93 and 94 and saw activities of more than one curie of 93 I felt that you [Bretscher] were struggling against very difficult circumstances!" On this testimonial, Bretscher asked again whether he might not have samples of 93 and 94, "for which one requires neutron sources of the strength available in California."^[116] But by then the new intensity of the S-1 program had put a premium on every atom of 94²³⁹ made in the Berkeley cyclotrons.

By the time of Pearl Harbor, the 37-inch and 60-inch machines had spent much of their time for almost a year on work that the NDRC deemed to be in the national interest. By then the 184-inch had also come under government protection, if not into government service. The commissioning occurred during the summer of 1941. Lawrence had been prompt in ordering the steel and copper, at the discounted prices that he and Loomis had negotiated with U.S. Steel (a savings of $30,000) and Phelps-Dodge; and also the power supply from GE, at its generous price without overhead charge. The contracts for the metal were let in July, and

for the construction of the magnet in September; the first installment of steel, some twenty-eight tons, a good chunk to be sure but less than 1 percent of the whole, went up the newly built road to the hilltop site on the last day of October 1940.^[117] Problems with the unions in December occasioned delays in building, but design work went forward expeditiously. Around New Year the parameters had been set, or almost so, to obtain deuterons of 100 MeV: the minimum gap between the poles would be 40 inches, or even 4 feet, to allow sufficient clearance between the dees and the chamber walls to permit peak voltages of a million across the accelerating gap. By the middle of February 1941, Lawrence had succeeded in spending $534,550 on the he-man cyclotron.^[118]

In the spring, however, just as workers were to start raising the cyclotron around the 30-foot tall magnet frame, construction met resistance that money alone could not overcome. To assure its supplies, the Laboratory tried to buy up all the copper and brass available locally before the government restricted or acquired the stock. In the summer, some contractors refused to ship equipment they had already made unless the 184-inch project could acquire a priority rating. In the fall, Salisbury, visiting GE's plant to enjoy the sight of the power transformers advertised as partially completed, learned that the completion referred only to the blueprints. "I was told that nothing would be done for at least a year unless we could get a priority." The same message came from Phelps-Dodge. "This unexpected turn of events made it necessary for us to appeal to the National Defense Research Council," Lawrence wrote the Rockefeller Foundation, in explanation of the admission of a new partner to their agreement. "Washington has been most cooperative. . . . [The] construction program is now going full steam ahead."^[119] Lawrence viewed the intervention as a favor,

not as a measure for defense; most of the materials needed had already been shipped to Berkeley before priorities obtruded; the "blessing of the OSRD," Lawrence told the Research Corporation, had fallen on the project "in line with a wise and foresighted policy of encouraging steady scientific progress in the midst of the stress of war activities." He hoped to have the cyclotron ready for trials in 1943.^[120]

If this encouragement were truly the purpose of the OSRD, virtue reaped its reward. The big magnet proved a fateful instrument of war. But no one saw it in the spring or summer of 1941. The uranium committee had paid for the electromagnetic separation of microgram samples of U²³⁵ only for determination of its nuclear parameters. No more than its British counterpart did the uranium committee or the first two NAS committees consider electromagnetism to be an option for large-scale separation. The third NAS committee—the one that reported on November 6—mentioned, without specifying, "other methods" than centrifugation and gaseous diffusion then under or needing investigation.^[121] As an expert on large magnets, Lawrence took on responsibility within S-1 for electromagnetic separation of small samples of light uranium for experimental purposes. Nier came to Berkeley in November to help Brobeck convert the 37-inch cyclotron into a mass spectrograph. The principle of operation is represented in figure 10.3: gaseous uranium ions from the source traverse circular paths under the old Poulsen magnet, the lighter isotope following the tighter circle and ending (if all went well) in a collecting cup. The first rough test at the end of November gave encouraging results; the mechanism, which became known as the "calutron" after the institution that gave it birth, appeared likely to contribute samples of U²³⁵ for experimental purposes.^[122]

This performance suggested that the chief technical difficulties in large-scale separation—the skimpiness of the beam and the menace of space charge that deflects the ions from their circles—

[Full Size]

Fig. 10.3
Principle of the calutron. It is not easy to obtain the clean and copious
separation indicated. Smyth,  Atomic energy , 164.

might be overcome. Already in October, Lawrence and Henry Smyth of Princeton had discussed the difficulties and persuaded each other to be optimistic. They had quite different corrections in mind. Lawrence thought to apply cyclotron technology and to build bigger; Smyth, who had some experience with Princeton's mass spectrometer, sought a new approach that would do without the collimating slits and so make use of an extended source. The ever-resourceful Robert Wilson found a way to help his colleague Smyth and challenge his teacher Lawrence. Wilson proposed to do without slits and magnetic fields by adapting the principle of the klystron: a wide beam of uranium ions would pass through a cavity oscillating at radio frequencies and emerge in two sets of bunches, one of each uranium isotope; at the cross section of the drift space where the bunches are best defined, a transverse rf field would work, phased to draw aside the heavier isotopes while allowing the lighter to pass on to a collector. The "isotron" (so named for no reason at all) as well as the calutron received funding at the meeting of the uranium committee on December 18, 1941.^[123]

In January 1942, promising experimental versions of both machines existed. But the isotron scarcely had a chance. Lawrence's means were not limited to what the government chose to give him—Brobeck had converted the 37-inch to a calutron on money from the Research Corporation—or to local or unpracticed help. A call went out, and cyclotroneers came home—James Cork, J.R. Richardson, and Robert Thornton, among others—to join or rejoin men who had not left. (Tables 10.2 and 10.3 tell who ended where.) These men knew their business. They put poles on the frame of the 184-inch magnet and went to work squashing the bugs in calutron prototypes tested under the Rockefeller Foundation's investment in the higher aspirations of the human species. They squashed the isotron soon enough. "Ernest wanted to cannibalize our group," Wilson remembered. "We resorted [in vain] to every device of politics and rhetoric to forestall the takeover."^[124] It took most of the rest of the war, most of the efforts of the Laboratory, and most of a billion dollars to make successful calutrons.

Glimpses of a New Era

Government work had its bright side. The salaries of research assistants and associates rose sharply, some tripling, when the civil service classified them. Nonacademic staff also prospered, although less dramatically. Griggs, who received no adjustment to salary in 1940/41 despite the large increase in her duties, got 9 percent more in 1941/42; Harvie, much underpaid as shop foreman in 1940/41 at $2,000, received three times the increase under the NDRC than he had from Sproul. As for the academic staff, Lawrence paid a monthly salary of a tenth the annual rate plus a subsistence allowance of $150 a month to people he wanted to attract.^[125] Then there were deferments. Seaborg pulled a low draft number. It did not worry him: "I expect to be involved in some sort of scientific work for the war effort instead of being drafted."

In April 1941 Lawrence wrote that the Laboratory had no trouble procuring deferments for all its graduate students and research fellows. In August, Griggs reported to the American Institute of Physics that only one member of the staff had been called to duty, a research assistant who was also an ensign.^[126] No one faced unemployment. "There aren't any men available here." Lawrence raided the movie studios for engineers, junior colleges for physicists, high schools for shop boys and storeroom clerks.^[127] And, when the OSRD began to outfit the 184-inch magnet for calutron work, he reached the end, or rather, the beginning, of the supply of trained manpower. "We have government defense jobs up here for almost any number of undergraduate majors in physics."^[128]

And now the downside. All these nouveaux arrivés destroyed the spirit of the Laboratory. Ninety people, most of them employees of a few months' seniority, attended the Christmas party in 1940. "It wasn't a cozy gang. . . . We all missed you like hell." Thus insider still inside, Kamen, to insider then outside, McMillan. Some had ceased to be insiders. When Wolfgang Gentner visited Berkeley in 1939, travelling under the patronage of the German government, he had been given the freedom of the Laboratory.^[129] For several years Lawrence and Cooksey had extended themselves to help Sagane and others copy the 60-inch. None of that was possible in the fall of 1940. The regents ordered that the Laboratory be closed to foreign scientists. The reasons, as explained by Lawrence to Nishina: overcrowding and "a certain amount of work in progress of a confidential character." The boycott extended to information about cyclotrons, or so Cooksey understood it; and he evaded requests from the Japanese for blueprints of the Crocker cyclotron. The connection was pointed out by Brobeck to Kurie, who had proposed a symposium on cyclotronics. "The cyclotron is now [March 1941] working on national

defense and may soon become an official defense project, so that it might not be wise or even possible to publish information about it."^[130]

Among the disagreeable features of war is falling toward the level of one's enemies. A few years earlier Rutherford and Lawrence had joked about restriction of access to German laboratories. Rutherford: "This state of affairs in Nazi-land is rather amusing, and when some of our men from the Cavendish wished to visit Berlin to see Debye's laboratory [at the new Kaiser-Wilhelm-Institut für Physik], he wrote to Cockcroft that official permission would have to be granted by the Government before he could admit them!" Lawrence: "Your account of the state of affairs in Germany is almost unbelievable. One would think that with such a scientific tradition the German people could not adopt such an absurd course of action in scientific affairs."^[131] In the fall of 1940 the reciprocal action seemed not absurd but prudent.

The regents did not stop with closing the Laboratory to touring potential enemies. They further ordered the firing of aliens paid from state funds. The comptroller made plain to Lawrence how deep the edict cut. "We regret that under the regulation . . . Mr Segrè is not eligible for employment by the University. Immediate steps should be taken to dismiss this employee from your staff." When this ukase came, Segrè and Seaborg were engaged in establishing the fissionability of element 94 by fast neutrons. Their collaboration had been inhibited earlier by the secrecy of the uranium commitee, which asked that Seaborg direct his sensitive results directly to Briggs and not confide in Segrè, who had a tendency to inform another alien, Fermi. Lawrence had done something to regularize the situation so that (as McMillan wrote Seaborg) "You will be able to talk to Segrè after all." Lawrence saw to it that the conversations continued. He obtained

permission from the provost to have the Physics Department hire Segrè as a part-time lecturer (then much in demand) paid for not by state funds but from the Rockefeller money, the balance of his time to be spent as a research fellow on the same fund in the Laboratory. Similar arrangements kept Kenneth MacKenzie (a Canadian) and C.S. Wu.^[132]

Throughout this time of partial mobilization—from the award of the Rockefeller grant in April 1940 to Pearl Harbor—Lawrence tried to keep the Laboratory at peace work as well as at war work. The beginning of the period coincided with the end of the phony war and the beginning of the end for France. "The war has taken an almost incredible turn for the worse," he wrote Morris, on May 10. "I hope we will get busy with the problem of arming ourselves. . . . We need to take every advantage of modern science and technology." He did not include himself among those who should busy themselves with the problem. On May 21 he listed "an impossible amount of work immediately ahead," namely, the medical program, nuclear physics, and the building of "the great cyclotron." On May 29, answering Thornton, who had told of the death of his brother, a Canadian, on the battlefield: "With the world situation as it is, it does seem hard to go ahead with our work. However, this is what we must do."^[133] And did. According to Bethe, who visited California six weeks later, the hawks of scientific preparedness wheeled around the old campaigner from Caltech, not around Lawrence. "Millikan, and it seems practically everybody at Pasadena is working on defense."^[134]

The appointment to Loomis's committee under the NDRC first brought Lawrence significantly into military preparedness. But, as Millikan rightly observed, Lawrence's part was to send others to do the work, not to do it himself. At the Laboratory, too, he played the occasional expeditor in work on the uranium problem

and element 94. Unlike Tuve, intensely at work on defense matters from the fall of 1940, Lawrence's main concern until late in 1941 was the construction of cyclotrons. That fall he could still write the Rockefeller Foundation and the Research Corporation that he intended to keep up the program in basic nuclear science. In October he listed pure physics, NDRC projects, medical research, and therapy, in that order, as the chief work of the 37-inch and 60-inch cyclotrons.^[135]

Lawrence threw his heart and soul into war work during his meeting with Conant and Arthur Compton at Chicago's golden anniversary at the end of September 1941. Lawrence gave his colleagues a pep talk about the MAUD report and Berkeley's plutonium work. Conant asked whether he would set aside the big cyclotron and devote the next several years of his life to making a bomb. The question "brought up Lawrence with a start. I can still recall the expression in his eyes. . . . He hesitated only a moment. 'If you tell me this is my job, I'll do it.'"^[136] Once committed, he pursued the goal with his native optimism and relentlessness. At a meeting with Compton and others late in October, there was some talk of the uncertainties of the undertaking. "This, to my mind, is very dangerous," Lawrence wrote Compton the next day. "It will not be a calamity if when we get the answers to the Uranium problem they turn out negative from the military point of view, but if the answers are fantastically positive and we fail to get them first, the results for our country may well be a tragic disaster. I feel strongly, therefore, that anyone who hesitates on a vigorous all-out effort on Uranium assumes a grave responsibility."^[137] Lawrence could be content only with a project through which his creation, his Laboratory, might make a decisive contribution to victory. "Calutron" says it all: the contribution of California, its University, and its Radiation Laboratory to a weapon that might change the course of history.