A Doubt
Meanwhile the Cavendish Laboratory had started to project deuterons. Rutherford had been most eager to procure heavy water for his experiments even before the startling discovery of the efficacy of deuteron bombardment. When Fowler returned to Cambridge from Berkeley early in May 1933 without any, he was "nearly lynched," he told Lewis, who forthwith forwarded a protective ampule containing as much deuterium as Lawrence's group had used in their disintegration experiments. Rutherford promised through Fowler not to hurry any results he might obtain into print, "so as to give Lawrence plenty of chance to get in first."[13] He received the news that deuterons had smashed atoms of lithium, nitrogen, magnesium, and beryllium. It reminded him of better times and of the Maori warrior on his baronial shield. "I should like to congratulate Lawrence and his colleagues for the
prompt use they have made of the new club to attack the nuclear enemy. . . . These developments make me feel quite young again."[14]
Rutherford hurled his clubs from a proton accelerator that had been made for him by Oliphant to follow up the experiments of Cockcroft and Walton. This accelerator may stand as a symbol of Rutherford's methods in contrast with Lawrence's. Rather than go to higher energies than Cockcroft and Walton had reached, Rutherford opted for lower; theirs could attain 800 kV, his only 200 kV. He wanted to examine the thresholds of proton-induced nuclear reactions, identify the products, and estimate yields as functions of the energy of bombardment. To achieve his purposes, he directed that his new machine have a large proton current; a directive so well executed that Oliphant and Rutherford had for their experiments about 1,000 times the single microamp of Cockcroft and Walton's early experiments.[15]
The Oliphant-Rutherford accelerator, though short on energy, was by no means the cheap, jerry-rigged contraption of string and sealing wax dear to Cavendish mythology.[16] Metropolitan-Vickers designed, built, and contributed the oil-diffusion pump that created the vacuum, which was produced and maintained with the help of Apiezon oils and greases; the accelerating system incorporated the voltage-multiplier circuit perfected by Cockcroft and Walton with the help of Metro-Vick's engineers and a 100-kV transformer bought from Metro-Vick at what Rutherford thought the extravagant price of 85 pounds; and the detectors, which recorded the ionization created in a special chamber by the disintegration products, used a linear amplifier, thyratron tubes, and a purely electronic counting system then just invented at the Cavendish by C.E. Wynn-Williams and his co-workers.[17] The Cavendish was then far ahead of Berkeley in electronics and vacuum technology and in integrating the work of academic
physicists and industrial engineers.
By February 1933 Oliphant and Rutherford were extending Cockcroft and Walton's results, provoking the disintegration of lithium with protons of only 100 kV. "It is a great show! But who would have thought that anything would happen at 100,000 volts, except perhaps Rutherford?"[18] In June, about the time the heavy water came to hand, they presented an account of their work on proton disintegration. They found that lithium's threshold stood at 20 kV and boron's at 60 kV; that beryllium's could not be determined because of its very small yield; and that in elements heavier than boron, except for a trace at fluorine, even the most energetic protons available, at 200 kV, did not stimulate disintegration. Oliphant and Rutherford traced apparent reactions in heavy metals such as gold to disintegration of boron impurities from the glass walls of their pyrex discharge tube.[19] This was an important warning. Lawrence did not heed it: he was too busy running through the periodic table, too eager to accept the astounding, to take the time to track down subtle effects.
When he ran Lewis's water against lithium, Oliphant detected particles of 13.2-cm range, which he identified with Berkeley's particles of 14.8 cm. "The Professor seems very happy."[20] Soon Oliphant and Rutherford confirmed the existence of rays that penetrated to 8.2 cm, which they showed to be alpha particles with the maximum energy possible in the reaction Li7 (d,n)2a .[21] Walton informed Cockcroft, then visting the Laboratory, of the good general agreement of Cambridge's results with Berkeley's. Cockcroft found himself curiously placed: he sat in the camp of one of his competitors while his partner, Walton, sat in the other. He decided that the most attractive subject for them was the prolific 18-cm proton, which Oliphant and Rutherford could not excite and Lawrence's company could not stop to study. "We ought to be able to get many of these [Cockcroft advised Walton]
and I hope you will be able to [borrow] some of the Professor's 
. I think that after Dee gets the Boron tracks you might go straight on to that with the Wilson chamber as we can get in long before California in this field and there are a lot of points to be cleared up."[22] For example, the origin of the 18-cm proton.
The Cavendish work, and Rutherford's congratulations to Lawrence on the "fine reward for his labour in developing his accelerated [!] system," pleased the Berkeley group and probably helped to harden their belief in what Lewis called "the most important discovery so far[:] the essential instability of the H2 nucleus and the low mass of the neutron." Cockcroft was also pleased at the confirmation obtained using the Oliphant-Rutherford accelerator. That had given him the hope that with the Cockcroft-Walton machine it would be possible to detect the 18-cm protons, for which Lawrence gave a threshold of 700 kV. "If so [Cockcroft wrote Rutherford] it [sic] will find a whole lot more work to be done with the present apparatus."[23]
To make all this work possible, the Cavendish required a steady supply of heavy water. Rutherford detailed a visitor, Paul Harteck, from the Kaiser-Wilhelm-Institut für Chemie, to the task. The Cavendish apprentice system in this respect paralleled Berkeley's: Harteck had been told to help with electronic counters, but was reassigned because of his knowledge of chemistry when Rutherford decided to domesticate the manufacture of deuterium. The change did not please Harteck. "I must take on the production of heavy water at the wish of the high Lord," he wrote his patron, K.F. Bonhoeffer. "If you know anything [about it], write me soon, for with the Lord everything must go very quickly. . . . You must hurry, since heavy water evidently seems to be no rarity in America."[24] The gift from Lewis took the heat off Harteck, who had not succeeded. An application to Lewis for information elicted a full answer that did not help; and by the end of June,
Harteck could only imagine that there was some trick to the business that had been withheld from him. Rutherford then lost half the original sample. Had Lewis then turned off his water, the Cavendish deuteronomers would have been out of business until the end of October, when Harteck managed to make enough heavy water at sufficient concentrations for their needs.[25]
There was already good reason to worry that Berkeley water did not give the same results in England as at home. Walton and Dee saw only a few 18-cm protons, nothing like the profusion the Berkeley group had reported. "I noticed Lawrence's views about the nature of these tracks," Rutherford wrote Lewis at the end of July, "but we are at the moment not inclined to view with favour the conversion of a deuton into a neutron of mass about 1. However, it is too early to take definite views."[26] The principal parties then relaxed for the summer, to prepare for more definite views in the fall.