The First War of Physics (43 page)

Death of a president

The next day, 12 April, Roosevelt died in Warm Springs, Georgia. He had been sitting for a portrait when he suffered a massive cerebral haemorrhage.
The Los Alamos community was shocked. Many mourned the departure of a much-loved national leader, a father-figure who had presided over America for thirteen years. Some wondered if the Manhattan Project would continue. At a memorial service convened on the Hill the following Sunday, 15 April, Oppenheimer delivered a eulogy. He quoted from the Hindu scripture, the Bhagavad-Gita:

‘Man is a creature whose substance is faith. What his faith is, he is.’ The faith of Roosevelt is one that is shared by millions of men and women in every country of the world. For this reason it is possible to maintain the hope, for this reason it is right that we should dedicate ourselves to the hope, that his good works will not have ended with his death.

Roosevelt’s successor, Harry S. Truman, had been Vice President for only a few months. He asked of Roosevelt’s widow, Eleanor: ‘Is there anything I can do for you?’ She replied: ‘Is there anything we can do for you? For you are the one in trouble now.’

As a Democrat senator, Truman had gained some fame and considerable respect with a campaign to reduce wastefulness in military expenditure, through the US Senate Special Committee to Investigate the National Defense Program, popularly known as the ‘Truman Committee’. He had nagged away at what seemed to be major accounting discrepancies in the War Department budget. At the time, Secretary of War Stimson had thought him an untrustworthy nuisance. As Truman was not a member of the trusted inner circle of the American administration, he had not been made aware of the existence of the Manhattan Project. He never did discover the origin of the discrepancies. Until now.

It fell to Stimson to reveal where the money had gone.

B-VIII

The Alsos mission had not found Weizsäcker in Strasbourg because towards the end of August 1944 he had already moved to Hechingen, ostensibly for a six-week visit to the Kaiser Wilhelm Institute for Physics; but in fact he
had no intention of returning to war-torn France. Shortly after returning with Heisenberg from Switzerland came news of the failure of Rundstedt’s offensive in the Ardennes. The Americans had suffered more than 80,000 casualties, the Germans slightly more. The last of the German army reserves were spent and the Luftwaffe had been largely destroyed. By early February 1945 the battle lines were redrawn more or less where they had been the previous December.

The war was lost but, Gerlach now reasoned, the peace could still be won. If German physicists could bring a nuclear reactor to criticality in one final push, then this would surely be a major achievement. One which could, perhaps, be used to bargain for better conditions in post-war Germany. Besides, as the war’s final stages dealt death even more indiscriminately, Gerlach was all too aware of the ‘safe haven’ provided by the nuclear programme. ‘Again and again the officials overseeing research and development have pressured us to [carry out a large-scale experiment]’, he had written in a letter to Heisenberg the previous October. ‘And I have to admit that they are right in the sense that many people have been exempted from front-line service in order to carry out such experiments.’

The signs were very promising. In Berlin, Wirtz reported that the reactor experiments in the bunker laboratory had yielded a neutron multiplication of 3.37 using graphite as a shield and neutron reflector. The Uranverein physicists scrambled for enough heavy water to carry out their final experiments. By 29 January, Wirtz had overseen assembly of B-VIII, their largest heavy water pile so far, consisting of hundreds of uranium cubes and a ton and a half of heavy water. The layer configuration that Heisenberg had stubbornly refused to abandon had finally given way to the much more promising lattice structure.

But time was fast running out. Soviet forces were advancing on Berlin at an alarming rate. Gerlach had no choice but to evacuate with the precious materials. Later that same day he told his friend Rosbaud that they were leaving Berlin ‘with the heavy stuff’.

Gerlach, Wirtz and Diebner travelled first to Kummersdorf, then south-west to a laboratory in Stadtilm, about 200 miles from Berlin, where Diebner had made preparations to complete his experiments. When
Heisenberg found out he was incensed. Even now he was not prepared to allow materials assigned to his research group to be used by his rival Diebner. Heisenberg and Weizsäcker made the perilous journey from Hechingen to Stadtilm to protest that the materials should now come to the cave laboratory in Haigerloch. Heisenberg prevailed. By the end of February, B-VIII was being reassembled in Haigerloch.

It was not to be. The B-VIII reactor showed a ten-fold increase in neutron intensity as the last of the heavy water was pumped in. This was a result better than anything the Uranverein had officially achieved thus far, but the physicists estimated that to achieve criticality they would need a reactor at least half as large again.
¹

Allied forces crossed the Rhine in February and by 6 March they had taken Cologne. Heisenberg planned to abandon theory and use the last of the uranium and heavy water from Stadtilm in a last-ditch effort to coax the reactor towards criticality. By the end of March American troops were converging on Stadtilm. On arriving back in Munich in early April, Gerlach found that he could no longer contact the physicists in Stadtilm. A few days later he was no longer able to make contact with Berlin.

Special task force

It seems likely that Kurchatov first learned of the implosion principle from Theodore Hall. The young spy had used a simple cipher based on Walt Whitman’s
Leaves of Grass
to arrange a rendezvous in Albuquerque with his Harvard friend Sax in December 1944. At that meeting Hall had passed to Sax a couple of pages of handwritten notes describing the first results of the Ra-La experiments and a theoretical summary of the implosion principle. Kurchatov declared the material to be of great interest. In a report dated 16 March 1945, he wrote:

It is difficult to give such a conclusion a final assessment, but the implosion method is undoubtedly of immense interest, is fundamentally correct, and should be subjected to close scrutiny both theoretically and experimentally.
²

Sax had not long delivered this information to his Soviet contact when Hall was drafted into the US Army, a victim of the pressure to recruit as many young men as possible for active service. Qualified scientists were exempted from the draft, but Hall had not completed his doctorate, and was not therefore sufficiently qualified. In Santa Fe, Hall protested to the recruiting officer, who discovered that Hall was needed back in Los Alamos. A compromise was reached: Hall was sent to Fort Bliss in Texas for his army induction and then returned to Los Alamos, in uniform, as a private in the army’s Special Engineering Detachment. Hall later put his experience down to the result of horse-trading between Oppenheimer and Groves. ‘Oppenheimer was agitating to get sidewalks’, Hall said. ‘And Groves was agitating to have people drafted. They reached a consensus: I was drafted and the sidewalks appeared.’

Fuchs arrived at his sister’s home in Cambridge in February 1945. She immediately informed him of Gold’s visit the previous November, and gave him the contact telephone number that he had left in her possession. Fuchs thus called Yatskov, who dropped everything to get to Philadelphia and ask Gold to go at once to Massachusetts. Yatskov gave Gold an envelope containing $1,500, payment to Fuchs for services rendered thus far, but insisted that Gold should not push Fuchs to accept the money.

After more than six rather nervous months, Gold met once more with Fuchs in the Heinemans’ spare bedroom. Fuchs briefly summarised the activities at Los Alamos and gave Gold a street map of Santa Fe. He suggested a future rendezvous in Alameda Street, on 2 June. In the meantime, he proposed to write a short report on everything he knew and pass this to Gold in a couple of days’ time at a pre-arranged meeting in Boston. Gold offered him the money, sealed in an envelope, but when he understood what it was he refused to accept it. Gold returned the envelope, unopened, to Yatskov.

Gold and Fuchs met again a few days later. In his report Fuchs had summarised information on the high spontaneous fission rate in reactor-bred plutonium, various aspects of implosion bomb design, including multipoint detonation and explosive lenses, the critical mass of plutonium compared with that of U-235, and current thinking on the design of the initiator. The report reached Kurchatov on 6 April.

By this time, the Soviet physicists had already become convinced of the relative advantages of implosion over the gun method for a plutonium bomb, but Fuchs’ report provided considerable additional detail. ‘All these are very valuable data,’ Kurchatov wrote, ‘but of particular substance are indications with regard to conditions conducive to achieving symmetry of the implosion effect, which is crucial to the very essence of the method.’

Thanks to espionage by Fuchs, Hall and Greenglass, the Soviet physicists were no more than a few months behind the latest developments at Los Alamos. However, Kurchatov was well aware that knowledge of fission physics and the principles of atomic bomb design were no substitute for practical experience with the materials involved. And, until the Soviet Union found a solution for its uranium supply problems, practical experience was going to be hard to gain.

But there was some progress on this front, too. By early 1945 Soviet forces had liberated Czechoslovakia with help from both Czech and Slovak resistance groups. A provisional Czechoslovak government was installed in Kosice on 4 April 1945. Edvard Beneš, President of Czechoslovakia’s government-in-exile in London, had maintained friendly relations with the Soviet Union throughout the war in an attempt to avoid a Communist coup at the war’s end. In March 1945 he appointed Czechoslovak Communist exiles in Moscow to key positions in his cabinet. He also
agreed a secret deal to allow the Soviets to source uranium ore from his country’s Joachimsthal mines.

On 23 March, Beria had suggested to Stalin that a special task force be established to ‘grope in Germany and search there for novelties of German atomic technology and for its creators’. In essence, the force was to operate in a manner similar to the ‘trophy brigades’ that had requisitioned (or looted) anything of value left behind by the fleeing German population as the Red Army advanced westwards towards Berlin. Beria chose one of his deputies, Colonel General Avram Zavenyagin, head of the NKVD 9th Chief Directorate, to lead the mission. Kurchatov was asked to submit suggestions for several search teams, and Khariton and Artsimovich were asked to provide scientific guidance.

Each unaware of the other, the Soviet mission now joined Alsos; scavengers of the Old World and New World wheeling and circling as they sought atomic technology, materials and personnel from the ruddy carcass of a defeated Germany.

Capture

Towards the end of March an Alsos team led by Pash captured Bothe and the Uranverein’s only cyclotron in the university town of Heidelberg. This was the first captured physicist known to Goudsmit personally, and he was unsure how to proceed. Bothe greeted him warmly, and they shook hands, which was specifically prohibited by regulations established to prevent fraternisation with the enemy. ‘I am glad to have someone here to talk physics with’, Bothe declared. ‘Some of your officers have asked me questions, but it is evident they are no experts on these subjects. It is so much easier to talk with a fellow physicist.’

Bothe treated the encounter as though this were a routine visit of a scientific colleague, and proudly gave Goudsmit a tour of his laboratory as he talked about the research they had done. Only when Goudsmit raised the question of ‘war problems’ did Bothe stop short, saying that he could reveal nothing that he had promised to keep secret.

At the Yalta conference in February 1945, Roosevelt, Churchill and Stalin had ratified the proposed post-war occupation zones for Germany. Initially there were to be three: American, British and Soviet; but Stalin agreed that France might have a fourth zone of occupation provided this was carved from territory within the American and British zones. In the event, the American and British administrations agreed to cede two non-contiguous areas to the French.

This left something of a problem for the Alsos mission. The southernmost of these areas included the Württemberg-Hohenzollern region, and the small towns of Tailfingen, Hechingen and Haigerloch. Groves trusted the French little more than the Soviets, and various plans were now devised to destroy or capture the last remnants of the German atomic programme before they fell into French hands.

Goudsmit argued persuasively that everything they had learned of the German programme indicated that there was little justification for a bombing raid or missions which might put Allied lives at risk (Pash was preparing nervously for his first parachute drop, on Hechingen). Events forced their hand. As French Moroccan troops closed in on the area, Pash hastily organised an ad hoc force of army engineers to get there first, by road. On 21 April, he drove into Haigerloch without incident.

The cave laboratory was quickly found. Eager to get in on the act, Perrin, Welsh and Charles Hambro, representing British interests in the mission, arrived shortly afterwards together with Lansdale and Furman to inspect the facilities. Perrin was the only one of the group to have seen Fermi’s original Chicago pile and he quickly concluded that the Haigerloch reactor would have been too small to go critical.

Uranverein physicists Bagge, Wirtz, Weizsäcker and Horst Korsching were captured in Hechingen a few days later. Max von Laue, though not part of the Uranverein, was also detained. Faced with this evidence of the sheer scale of the Alsos mission, and after lengthy interrogation, Wirtz and Weizsäcker yielded the uranium, heavy water and, eventually, documents that they had carefully hidden just a few days earlier.

Hahn was captured in Tailfingen on 25 April. He was waiting for them, his suitcase already packed. From Hahn, Goudsmit learned devastating
news. His parents had perished in an Auschwitz gas chamber. Heisenberg had written a personal letter pleading for their release, but they had been murdered five days before it was sent. Heisenberg could, perhaps, have done little more to intervene on their behalf, but Goudsmit would never forgive him for not trying harder.