4—
The New World and the Old
Running In
None of the European cyclotrons was in regular operation in 1938. The Cavendish had only "evidence" of a deuteron beam at the end of August (they had been expecting since March), but nothing on target; they switched to protons, coaxed forth 0.02 µA, and started shimming. Lawrence advised more voltage on the dees; hit the ions hard enough, he said, and "the beam will come through without any attention to shims at all." That worked: before Christmas Cockcroft had 12 µA of 5 MeV protons. But in trying to reach the design energy for deuterons, some 11 MeV, he ran into trouble from parasites, faulty insulators, and a badly machined chamber. At the end of May 1939, the deuteron beam amounted to only 3 µA at 9 MeV; the following month it had risen to 5 µA steadily on target and as much as 15 µA at peak performance.[69]
[68] L.A. Turner to Frisch, 23 Aug 1938 (Frisch P); Pegram to Joliot, 23 June 1938, Paxton to Joliot, 14 Nov 1938 and 4 Mar 1939, to "Ignace," 29 Jan 1939, and to Nahmias, 12 Feb 1939 (JP, F25); Tisdale, "Diary," 4 Mar 1939 (RF, 500D).
[69] Hurst to Cooksey, 31 Jan 1938 (4/21); Cockcroft to Lawrence, 24 Oct 1938, 21 Jan 1939, and [June] 1939, Lawrence to Cockcroft, 16 Nov 1938, and Cockcroft to Cooksey, 29 May 1939 (4/5); Cockcroft, Jl. sci. instr., 16 (1939), 41–2.
That was enough to do experiments and almost to impress visitors. J.G. Spear, of the Strangeways Research Hospital, Cambridge: "The Cambridge cyclotron is now beginning to function and is running at about 5 micro-amps—sufficient to make biological experiments possible but not up to the Berkeley standard yet." Bohr judged Cockcroft's cyclotron to be as capable as his own. Lawrence applauded the onset of steady operation and the 15 µA "so early in the game." It had taken three years from the commissioning of the magnet, experts and blueprints from Berkeley, the largest British electrical manufacturer, and the resources of the Cavendish to accomplish the feat. That was the fastest English pace; they still sought a stable beam in Liverpool. "With your cyclotron working so nicely [Lawrence wrote Cockcroft], Chadwick and Kinsey should feel much better, for I am sure that with all their trouble they must have doubted that a cyclotron could be made to work satisfactorily [in Britain]." Both British cyclotrons operated satisfactorily and at substantial currents during the early war years, when they provided information for guiding speculations about the possibility of nuclear explosives.[70]
A similar story can be told of the running in of the Copenhagen cyclotron. It, too, was designed to produce deuterons at over 10 MeV. In December 1938 its builders had about 1 µA of 4 MeV deuterons, with which they drove a beam of neutrons equivalent to the yield from a kilogram of radium mixed with beryllium. The Danish press, which believed Bohr could do anything, advertised that he had made a kilogram of radium. Frisch wanted to use this fine source for physics; Bohr insisted that the machine be adjusted to give bigger currents at higher energies, in order to make in quantity the radioisotopes for which the Rockefeller Foundation had paid.[71] Instead, it broke down.
Repairs brought back the microamp of 4 MeV deuterons, "a real thrill, and a great relief," but the machine did not yet run well.[72] The main difficulty was the same as Cambridge's, too little
[70] Spear to Cornog, 28 June 1939 (16/41); Bohr to F. Paneth, July 1939 (BSC); Gowing, Britain and atomic energy , 61, 403; infra, §10.2.
[71] Frisch to Meitner, 26 May 1938, to Weisskopf, 12 Dec 1938, and to Placzek, 18 Dec 1938 (Frisch P); Bohr to Lawrence, 20 Dec 1937 (expecting a beam "within a few months"), and 11 Nov 1938 ("working well") (3/3).
[72] T. Bjerge to C. Lauritsen, 20 Jan 1939 (BSC), quote; Frisch to Meitner, 20 Jan, and to Bohr, 22 Jan 1939 (Frisch P).
voltage on the dees; not until the fall of 1939 was Bohr's cyclotron "brought to the stage of producing an efficient beam of high-speed particles." During November the Copenhagen group caught a glimpse of 9 MeV and a grant from the Thrige Foundation to develop the electrotechnical part of the cyclotron "to the utmost efficiency." They achieved a steady deuteron beam at 9.5 MeV in the spring of 1940. During 1939 and 1940, the cyclotron manufactured isotopes for Hevesy as planned. It ran until March 1941, when it was idled for improvements and to conserve electrical power.[73]
Joliot was getting a fair yield of deuterons in June 1939, but the oscillating system still did not perform satisfactorily. He had the machine pulled apart for modifications, which, however, could not be completed before the mobilization of the laboratory. Joliot succeeded in recalling Nahmias from the French Army late in 1939 and in acquiring from the Rockefeller Foundation, then still in business in France, 60,000 francs for stipends for an expert and a helper in high-frequency electronics. The machine had not been returned to working order before the occupation of Paris. "I am thankful for that," Nahmias wrote from the temporary safety of Marseilles, where he had found a job in a cancer clinic, "because being in such a messy state it may look unworthy of a German lab."[74]
The fall of France closed off the Rockefeller Foundation's subvention to Joliot on orders from the U.S. government and brought the German military into the sub-basement of the Collège de France. The first officers to contemplate the broken, unkempt cyclotron wished to confiscate it for its copper and other strategic materials. The proposal came to the attention of the head of research for German Army Ordnance (Herereswaffenamt), Eric Schumann, who had been alerted to the possibility of nuclear explosives by Paul Harteck. Schumann immediately flew to Paris
[73] Jacobsen, Dansk. Vidensk. Selsk., Math.-fys. meddelser, 19:2 (1941), 4, 23, 27, 30; Bohr to Tisdale, 25 Nov 1939, and Weaver to file, 3 Jan 1940 (RF, 713D); S.H. Jensen to Frisch, 25 Nov 1939 (Frisch P); Hevesy to Lawrence, 11 Sep 1939 (9/7); Hevesy to Urey, 21 Jan and 10 Nov 1941 (Urey P, 2).
[74] Nahmias to Hansen, 18 Oct 1940, Joliot to H.M. Miller, Jr., 28 Nov 1939 and 28 Mar 1940, Miller to Joliot, 6 Dec 1939, and to file, 25 Nov 1939, and Nahmias to Miller, 10 Dec 1940 (RF, 500D).
and saved Joliot's cyclotron. An agreement was then concluded according to which Joliot would continue his research and admit three Germans to work in his laboratory.[75]
According to the field representative of the Rockefeller Foundation, Joliot thought the Germans were sincere in their expressed wish "to follow the edict that science was international, that scientific work should go on, and that, as Joliot represented a distinguished member of the scientific world, his laboratory should be approved of and supported by the Germans in every way possible." This highly implausible reading of the situation turned out to be realized. The Germans put Joliot's former collaborator Gentner, then in the service of the Heereswaffenamt, in charge of their presence in the laboratory. Gentner managed to discourage his superiors from removing the cyclotron—it would be too costly and dangerous to rip it from its cellar—and to protect it from entrepreneurs like Manfred von Ardenne, who was trying to interest Nazi agencies in building accelerators to assist in research on the exploitation of nuclear energy.[76] With the help of Gentner and German experts in radio technology and of Oerlikon, which made up the steel and copper Joliot procured into new parts for the electromagnet, the Paris cyclotron was at last set to going reliably, with an output of alpha particles equal in number and energy to those from 100 kilograms of radium.[77]
It is said that the cyclotron faltered when Bothe wanted to use it to study the fission of uranium. The French operating crew then sabotaged it in subtle ways that gave Bothe the impression that he had mishandled the controls. Gentner understood and overlooked the maneuver. He protected Joliot, whom he knew to be a leader of the Resistance, and helped French physicists elude the Gestapo. The German authorities did not approve of Gentner's style of supervision and in 1942 returned him to
[75] D.P. O'Brien to Joliot, 31 Oct 1940, and Joliot to R. Letort, 20 Oct 1941 (JP, F34); O'Brien, "Diary," 12 Sep 1940 (RF, 500D); Irving, German atomic bomb , 36, 40–1.
[76] O'Brien, "Diary," 12 Sep 1940, and Nahmias to Hansen, 18 Oct 1940 (RF, 500D); Ardenne to Joliot, 27 Nov 1940 (JP, F28); Irving, German atomic bomb , 76–8, 89; Ardenne, Mein Leben , 157–9, describing activities little in keeping with the humanitarian intentions he proclaims, ibid., 149, 268.
[77] Langevin, "Rapport" on Joliot, 1943, 15 (Langevin P); Oerlikon to Joliot, 27 Sep 1941, 15 and 22 Jan 1942, 26 Jan 1948 (JP, F25).
Heidelberg, where he made the first cyclotron in Germany, give an indication of a beam in December 1943. This machine had been planned since 1937, together with one for the University of Leipzig, both of which were ordered from Siemens in 1939. Siemens worked on them and on a larger one for the Heereswaffenamt during the war, while Krupp tended to two others, for Manfred von Ardenne and for the Research Institute of the German Post Office. The very sizable expenditures in strategic material and trained mechanics this manufacture required were intended by the physicists and the manufacturers as investments for a postwar competition in useful radioisotopes. It was also, according to a consensus of industrialists and Nazi officials, "a matter of prestige for Germany, which must be pursued even during the war, although cyclotrons have no decisive military importance." These industrialists also invested in betatrons, "exclusively," according to Steenbeck, "for business purposes. If the Americans were working on it, we must hurry, so that after the war, no matter how it turns out, we can bring our apparatus into the market place as soon as possible, if necessary with the American firm we license."[78]
Two cyclotrons were operational when the war ended: Bothe and Gentner's in Heidelberg, and the Post Office's in Miersdorf. Neither enhanced its builders' market value. The Russians stole the Miersdorf machine. As for Gentner, he had no need of out-of-date cyclotronics to enhance his merits. The French remembered his friendship and courage in the matter of Joliot's cyclotron and made him an officer of the Légion d'honneur.[79]
Running Over
It is scarcely an exaggeration to say that a week's sweating over a Berkeley cyclotron was worth six months' immersion in its blueprints. In just a few days in the spring of 1937 Cockcroft saw enough to "feel . . . that the uncertainties in my mind about
[78] Osietzki, Technikgesch., 55 (1988), 36; Steenbeck, Impulse , 124.
[79] Weisskopf in MPG, Gedankfeier , 24–5; Gentner, ibid., 41–4; Weart, Scientists in power , 156–60; Goldsmith, Joliot-Curie , 62, 99–101; Joliot, "Autobiographie," in Joliot, Textes choisis , 91–2; Gentner in FIAT, Nucl. phys., 2 , 28–31; Salow in FIAT, Nucl. phys., 2 , 32–3.
cyclotron operation have been completely removed." His visit followed immediately after one by Bohr, who found in the working machine reassurance for himself and his patron: "The decisive importance of the new grant for our work [he wrote the Rockefeller Foundation] has become still more clear to me during my stay in Berkeley, where I have been most impressed by the ingenuity with which Professor Lawrence and his group in the Radiation Laboratory ha[ve] developed his wonderful cyclotron into an ever more efficient but of course an ever more complicated apparatus."[80] Also in the spring of 1937 Nahmias arrived from Paris and Sten von Friesen from Stockholm, presaging, so Lawrence fancied, a "world wide epidemic of cyclotron construction."[81]
The epidemic continued in the winter of 1938/39 with Oliphant from Birmingham and Bothe and Gentner from Heidelberg. Their letters point not only to the value of the information they acquired but also to a quality present in an exaggerated degree in Berkeley and rapidly dwindling in Europe. Bothe: "I am especially impressed by the atmosphere of enthusiasm and comradeship ruling in your laboratory." And well he might be, since by then the institutes of the Kaiser-Wilhelm-Gesellschaft were riddled with Nazis. Among the "noteworthy" items he mentioned in his official report on his trip to the United States was "the model camaraderie among the 10 or 15 members of the cyclotron crews."[82] Gentner had not expected the great hospitality and generosity he experienced in Berkeley, where no one seemed to mind that he represented (though he did not approve) a totalitarian state. He remained for seven weeks in the cyclotroneers' Mecca: "For here [as he explained his long sojourn to his sponsors] is the center of cyclotron construction, and all other installations are more or less close imitations of the fundamental work of Professor Lawrence."[83]
[80] Mann, Nature, 143 (8 Apr 1939), 585; Cockcroft to Lawrence, 13 Apr 1937 (4/5); Bohr to Weaver, 4 Apr 1937 (RF, 713D).
[81] Lawrence to W. Buffum, 5 Apr 1937 (3/38).
[82] Bothe to Lawrence, 20 May and 30 June 1939 (3/6); Bothe, "Bericht über eine Vortrags- und Studienreise nach USA," 19 Aug 1939 (MPG, Bothe NL/30).
[83] Gentner to Cockcroft, 28 Feb 1939 (CKFT, 20/11); Gentner, "Bericht über die Reise nach Nordamerika," attached to Bothe to Generalverwaltung, Kaiser-Wilhelm-Gesellschaft, 25 May 1939 (MPG, KWG Akten/1063).
As for Oliphant, he was swept of his feet: "Many things about the cyclotron are now clear, which formerly were hazy. . . . I return with a greater confidence and a greater belief in the cyclotron, in physics, and in mankind."[84] Oliphant had plenty of money—some 60,000 pounds from Lord Nuffield, the magnate of Morris Motors, more than enough to outdo Austin's cyclotron at the Cavendish—and plenty of enthusiasm. Cambridge copied the 37-inch; Birmingham would exceed the 60-inch. Oliphant expected to be finished by Christmas 1939 and did manage to erect his magnet, "of phantastic dimensions," according to Frisch, who saw it in August. But Oliphant's new confidence in mankind was misplaced; war stopped construction, and Lord Nuffield's cyclotron was obsolete when it started up in 1950.[85]
The culture shock experienced by some Europeans who spent time in American accelerator laboratories makes the same point in reverse. The lust after machinery, the squandering of time on mere technical improvements, offended them as uncivilized and unscientific. "Americans are mostly coarse types, very good workers but without many ideas in their heads. . . . Their number is impressive, it is true, but one should not worry too much about their technical facilities. It will be a long time before they get from them what they can." So wrote Walter Elsasser, a Göttingen Ph.D., who had worked in Germany and in France and was to make his career in the United States. He excepted Lauritsen from his indictment: "Everything in his laboratory is built with great simplicity and without the technical elegance that Americans love so much. . . . Lauritsen is a European by birth as well as in spirit."[86] Likewise Emilio Segrè remarked on the want of subtlety of the machine makers at the Radiation Laboratory. Segrè trained all over Europe—in Rome with Fermi, in Hamburg with Stern, and in Amsterdam, where he continued his studies of spectroscopy in the laboratory of the old master, Pieter Zeeman. This itinerary provided a perspective quite different from Berkeley's: Fermi and
[84] Oliphant to Lawrence, 11 Jan 1939 (14/6).
[85] Oliphant to Lawrence, 19 Jul and 20 Aug 1938 (14/6); Frisch to "Franz," 16 May 1939, and to J. Koch, 28 Dec 1939 (Frisch P); Cockburn and Ellyard, Oliphant , 73–4, 78, 136.
[86] Elsasser to Joliot, 13 Sep 1936 (JP, F28). This sentiment does not recur in Elsasser, Memoirs , chap. 8, "Passage to the New World."
Stern had command of deep theory as well as of experimental technique, and Zeeman had made a career of accuracy in measurement. As Franz Kurie wrote of himself and his fellow cyclotroneers: "One feels quite the blundering caveman beside one's spectroscopic brothers."[87]
We already know some of Nahmias's ideas about American techno-physics. Here is his summary: "I've observed here [Tuve's lab] and at Van de Graaff's a certain rush to realize projects immediately after we first discuss them. [Americans] work quickly and in groups, but [he reassured Joliot] you should see their alarm when one talks about future European installations." The coordination needed to realize the projects oppressed him so heavily that he decided not to do experimental work in Berkeley. "I occupy my time better in reading nuclear physics, biology, and electro-technology than in hypnotising myself in front of an electroscope with the nth new period [of radioactive decay]."[88] When Lawrence suggested that Joliot ask the Rockefeller Foundation to extend Nahmias's stay to enable him to learn by helping to assemble the 37-inch, Joliot declined, thinking that his emissary had learned and suffered enough.[89]
The fascination with hardware and the subordination of the individual to the group that characterized Berkeley by the late 1930s were to spread from accelerator laboratories to other parts of physics and from the United States to the rest of the world. Ryokichi Sagane may serve as a weather vane. After a year at Berkeley and a return there, he toured laboratories in the United States and then visited the Cavendish. "I was rather disappointed and also astonished," he wrote Lawrence. Although he judged that some pieces of native apparatus showed some ingenuity, it was clear to him that the British like the Japanese would have to derive their methods from the Americans. "So far as the experimental techniques are concerned, America has surpassed very far the England."[90] The award to Lawrence of the Nobel prize in phy-
[87] Segrè, Ann. rev. nucl. sci., 31 (1981), 1–18; Kurie, Jl. appl. phys., 9 (1938), 692.
[88] Resp., Nahmias to Joliot, 24 Mar and 12 June 1937 (JP, F25).
[89] Nahmias to Joliot, 2 Aug 1937, Lawrence to Joliot, 25 May 1937, Ragonot to Nahmias, 9 Dec 1937, and Joliot to H.M. Miller, 5 Jul 1937 (JP, F25); Tisdale, "Diary," 12 Jul 1937 (RF, 500D).
[90] Sagane to Lawrence, 14 Nov 1938 (9/39).
physics for 1939—an event of great importance for our history—was at once an emblem of this dominance and the certification of the cyclotron at the international level. The American style of physics established a beachhead in Europe before the war. Lawrence's machine was the landing craft.