Hitler's Terror Weapons (11 page)

“The experimental assemblies containing paraffin as a moderator were not suitable for neutron multiplication. They were to measure important constants for later designs.”
⁶⁷

Measurement was made of the neutron distribution inside the sphere and in the ordinary water surrounding it. It was concluded that uranium metal powder was better than uranium oxide and

“confirmed other experiments in that when evaluating the neutron figure, account should be taken of neutron capture by U
²³⁸
isotopes”.

In other words, experiments L-I and B-III with layered uranium and paraffin were concerned primarily with measuring the generation of neutrons and their capture by U
²³⁸
isotopes, for on concluding an experiment the amount of U
²³⁹
(which eventually decays into plutonium) forming in the uranium material was to be measured.

Speer Attempts to Resurrect the Official Project

On 7 February 1942 Dr Todt was killed when his personal Heinkel bomber crashed taking off in poor visibility at Rastenburg. Hitler decided to appoint Speer at once as successor to Todt. As has been mentioned, Speer was an enthusiast for the atom bomb, but soon found that the
Völkischer Beobachter
began to stir against him whenever he approached Hitler on the subject of atomic physics. The first convention of the Reich Research Council was held at its Berlin Steglitz HQ on 26 February 1942 under the chairmanship of Reich Minister Rust. Substantial funds became available to the project for the first time once Rust had become convinced that the heat reactor could definitely be built. In what must have been a speech glowing with optimism Heisenberg assured him not only that atomic reactors for energy production were “undoubtedly possible” but that an enormously powerful explosive could be bred in them.

In early May 1942 Speer arranged for Goering to be appointed head of a newly independent Reich Research Council. The restructuring was intended to emphasize the importance of the new committee which Speer was planning should oversee a progressive research programme for military purposes. Goering's presidential council consisted of 21 members who were either Ministers, Chiefs of Staff or high Party officials and thus the uranium project was taken over completely by the political side after all.

The Last Two Leipzig Experiments

Heisenberg's paper G-136:
The Proof by Experiment of Effective Neutron Multiplication in a Layered arrangement of Heavy Water and Uranium Metal in a Sphere
⁶⁸
was undated but delivered with a covering letter dated July 1942, the month following an accident which destroyed Heisenberg's Leipzig apparatus. The report was stamped
Geheime Kommandosache
(i.e.
very secret)
, an unusual classification which may possibly be explained by the conclusion in the summary that:

“A spherical arrangement of 17-cm wide layers of heavy water and 4-cm wide layers of uranium metal density 10 separated by 2 to 5mm thick aluminium support material has a
negative
coefficient for neutron absorption. The mere enlargement of the layered arrangement described herein will lead to a uranium pile for the production of nuclear energy.”

In L-II the previous year, using uranium oxide, the experiment had given a positive neutron coefficient which was very marginal: there had been a neutron multiplication but this had been lost to the aluminium material of the sphere.

L-IV consisted of two aluminium hemispheres bolted together at the equator. A chimney was fitted through which the
Präparat
would be dropped into the centre to initiate the reaction. The apparatus was bedded on a foundation of waterproofed wooden beams in a zinc tub filled with ordinary water. The internal arrangement was a 17-cm radius aluminium sphere with walls 1.2 mm thick. This contained 140 kilos of heavy water and the
Präparat.
The inner sphere rested on a lower hemispherical shell of 5-mm aluminium plate containing 90 kilos of uranium powder of density 10.8 and this in turn rested on a larger hemisphere filled with 660 kilos of uranium powder of density 9.34.

The measurements showed a neutron multiplication of 13%, and with this apparatus Heisenberg had succeeded in generating more neutrons than provided by the
Präparat
source. Simply by increasing the size of the sub-reactor one would eventually have a working uranium pile for the production of nuclear energy.

For the reactor builder the next step was an experiment in which the materials were increased and on 31 July 1942 in G-161
Observations on the Planned Intermediate Experiment with 1.5 tonnes Heavy Water and 3 tonnes Uranium Metal
Heisenberg did precisely that. It was logical. But what was not logical was that meanwhile he had set up a duplicate of L-IV. He knew what would happen. The uranium fuel would gradually become more radioactive with the products of fission and plutonium being formed in the U
²³⁸
resonances, but what would that have to do with reactor technology?

On 2 June 1942 the experiment began. 750 kilos of uranium metal powder in the outer shere surrounded a central sphere of heavy water. As before, the apparatus was immersed in a vat of ordinary water, the
Präparat
was dropped into the centre via the chimney, and Heisenberg, Mr and Mrs Döpel, master mechanic W. Paschen and technician G. Kunze, who monitored the gamma-radiation instrumentation, all sat back for a few months to see what would happen next.

In the U-metal/paraffin experiment B-III, measurements were made of neutron capture by the resonances along the diagonals outward from the central
Präparat.
From this information it was a straightforward matter to plot where the diminishing neutron velocities coincided with the greatest incidences of neutron capture, and this was in fact known as
Factor e/w
where w = probability of resonance capture.

The concentric inner sphere of Heisenberg's L-V experiment at Leipzig contained 220 litres of heavy water, the small nickel ball with the radiumberyllium neutron source being at its centre. This
Präparat
played a twofold role. It emitted neutrons into the heavy water where they lost a degree of momentum before proceeding into the surrounding uranium metal powder. Here they fissioned U
²³⁵
atoms to release more neutrons into the reaction or were captured by U
²³⁸
isotopes to decay into plutonium. Additionally, gamma radiation from the neutron source generated photoneutrons in the heavy water and these also entered the uranium. Over a period of many months this ‘experiment' would be a subtle means of uranium enrichment, since a measureable proportion of the U
²³⁸
capture band converted into the fissile isotopes of plutonium. After his return to Leipzig University on 23 June 1942, it was noticed that the sphere, which had been quietly fissioning for three weeks, was leaking bubbles. The equipment was raised from the water and an access hatch opened to inspect the interior. A hissing sound was followed by a jet of flame. The sphere was hosed down with water until the fire appeared to be extinguished. The heavy water was then drained from the inner sphere to prevent its accidental contamination, after which the main sphere was re-sealed and lowered back into the water tank for safety. A few hours later the apparatus began to give off bubbles once more and the water in the containing tank began to boil. On closer inspection it was seen that the sphere was vibrating and beginning to swell in size. The laboratory was evacuated and shortly after there was an explosion involving a hailstorm of burning uranium powder. The fire brigade succeeded in dowsing all fires except that in the sphere which was allowed to burn out over the next few days.

How did this fire start? Possibly fissioned material in the powdered uranium began to warm up. As it expanded, the pressure cracked the seal holding the two aluminium hemispheres together, allowing water to enter from the shielding tank. This would have oxidized the uranium, generating more heat. But the ignition source is a mystery. The material burnt out and the attempt to do whatever it was that was being attempted failed. So terminated this series of experiments, the purpose of the last of which seems not to have been questioned too closely previously.

Professor Goudsmit Not Deceived

The only military scientist on record as believing that Heisenberg had been involved in an attempt to build a German atom bomb is Professor Samuel Goudsmit. In his book
Alsos- The Failure in German Science
(Sigma, London, 1947) on page 183 Professor Goudsmit reproduced two sketches contained in Heisenberg's official German wartime report respecting the B-III uranium/paraffin experiment. Under a drawing of the chimneyed sphere appeared the caption “Germany's Atom Bomb” and the words “Germany's experimental uranium pile which they believed would make a bomb”. Beside a slightly adulterated version of the cut-through diagram he wrote, “Diagram for the experimental ‘bomb' which consisted of layers of uranium and paraffin”. Professor Goudsmit was Jewish and had lost both parents at Auschwitz. His book was a non-scientific publication very popular at the time and it is possible that he was merely attempting to ridicule Heisenberg's scientific circle. But one can interpret it in another sense. Perhaps this was as far as Goudsmit, who was restrained by the various US secrecy laws, was permitted to go in print with his allegation. Joke or not, this device would have worked as the warhead of a V-2 rocket.

After five or six months in the sub-reactor sphere, the uranium powder was enriched with plutonium. In the bomb casing the material would be stacked in alternate layers with paraffin. The paraffin in the top hemisphere layers prevent premature fission by the highly radioactive Pu
²⁴⁰
plutonium isotopes which would otherwise spoil the reaction when the bomb is detonated. The bottom hemisphere would be filled with iron ballast. The weight of bomb core, casing and ballast material acting as an anvil would have been limited to one tonne, the payload of a V-2, the speed of the rocket at impact rendering superfluous the four or so tonnes of HE necessary to set off the device in normal circumstances. Impact was at Mach 3.5. Because detonation would not be uniform around the bomb sphere, this method would have resulted in a ‘fizzle' equivalent to several dozen tonnes of TNT, an earthquake effect and meltdown with radioactive fallout.

It was a brilliant concept, cheap to manufacture anywhere and not difficult to produce in numbers. The failure of the Leipzig experiment after only three weeks signalled the end of Professor Heisenberg's participation in the project and in midsummer 1942 the project was transferred elsewhere.

CHAPTER 6

The German Post
Office Takes Over

“I, of all people, did in fact lead the way for the great advance in atomic development in the German Reich.”

Wilhelm Ohnesorge, Postmaster General, 1937-1945 Quoted from his obituary, Soldatenzeitung, East Berlin, 10 March 1962.

A
LBERT SPEER
⁶⁹
recalled that, although Hitler did speak to him occasionally of the possibilities of the atom bomb, the strategic benefits of having it eluded the Führer. The subject was a source of irritation to Speer, for he knew that there was in existence some sort of secret arrangement involving the Post Office about which he was being left completely in the dark, and this appeared to be a matter on which, as Armaments Minister, he really ought to have been consulted.

Explaining that there were 2200 recorded points of reference in his conferences with Hitler, and that there was only a single occasion when the subject of nuclear research appeared on the agenda, being passed over “with laconic brevity”, Speer noted Hitler's strengthening resolve not to pursue the matter.

Hitler's objection to the atom bomb was fundamental. He had read somewhere (almost certainly the article by Professor Jean Thibaud of the Sorbonne published on 12 March 1941) that a nuclear explosion might proceed to ignite all the hydrogen atoms in the atmosphere, transforming the world into a glowing star. German physicists could not guarantee that the theory was definitely wrong: even at Los Alamos in July 1945 the Italian-American physicist Fermi wondered aloud whether the test bomb he was about to ignite might trigger the heavens, destroying every living thing on earth. Speer thus concluded:

“Even if Hitler had not been against nuclear research on doctrinal grounds [i.e. Aryan Physics]: even if the stage we had reached in investigating the principles in June 1942 had provided the atomic physicists with an objective for the investment of thousands of millions of marks towards producing the atom bomb, it would have been impossible for our strained war economy to have brought together the technicians, materials and priorities for the project.”
⁷⁰

It is an odd thing that Hitler should have appeared to shun atomic physics when speaking to Speer whilst openly affirming his enthusiasm for its future prospects to his closer companions at table. Martin Bormann's stenographer Henry Picker recorded
⁷¹
that Hitler considered the splitting of the atom to be the most important of all scientific achievements for Germany's future to the extent that it was the Führer himself who was inspirational in having the short documentary film
Gold
starring Hans Albers exhibited repeatedly in cinemas in order to popularize the subject of nuclear science. Anything short of a chain reaction was Aryan Physics.

Albert Speer wrote disapprovingly
⁷²
about the unaccountable optimism in Hitler's demeanour whenever the subject of nuclear energy came under discussion in the early summer of 1942, and the Führer's disposition appeared to Speer to have the closest possible connection with a clique consisting of the Postmaster-General, Ohnesorge, Goebbels and Hitler's personal photographer, Heinrich Hoffmann, who were all apparently party to some big secret.