Life and Work of Rolf Wideröe by © Pedro Waloschek,     => Contents

7   The Hamburg-Betatron

My wife and our three children remained in Oslo while I started working in Hamburg in August 1943. I was an employee of NEBB during my entire stay in Hamburg and my wife continued to draw my salary in Oslo. So we had no problems - apart from the separation. I had rented a room in a beautiful house in a leafy suburb of Hamburg.

My first, and probably most important, contact in Hamburg was Richard Seifert. Later he became doctor honoris causa of the Universities of Hamburg and Hanover. I can't remember exactly how this contact came about. In any case, he was the owner and director of a medium sized factory, founded by his father in 1892, which had a good reputation internationally. This factory had already begun manufacturing devices for X-rays in 1897, i.e. just two years after Röntgen had discovered these rays, and during my time they manufactured these, mainly for non-destructive testing of materials, such as welded joints. Not only did they manufacture a standard range of products, but they also dealt in clients' special customised orders. During the War they were major suppliers of apparatus for materials-testing for the German air-craft industry.

Seifert was a hard-working and honest man and I had the greatest respect for him. He was very supportive to me in my strange predicament. Years later we would often visit the youngest of his three daughters, Elisabeth, when we passed through Hamburg. By then she had taken over the management of the factory. The various departments were later relocated to Ahrensburg near Hamburg.

Also in Hamburg I had a wonderful collaborator and colleague, the physicist Dr. Rudolf Kollath, who had previously worked in the aluminium factories in Sauda (near Stavanger in Norway) as well as at AEG in Berlin - I believe with Professor Ramsauer. Later on he became a professor in Mainz and he also wrote a very nice book on particle accelerators which appeared in 1955 [Ko55]. The second edition was much more comprehensive. It included contributions by several well known scientists and came out in 1965.

See Fig. 7.1: A drawing of the 15-MeV-betatron in Hamburg,
Fig. 7.2: A photograph of the 15-MeV-betatron in Hamburg,
Fig. 7.3: Pole pieces and field distribution in the betatron
and Fig. 7.4: The vacuum chamber of the Hamburg betatron.

While I was working in Hamburg I wasn't really answerable to anyone in particular. The only person to whom I had some contact of that type was Air-Force Group Captain Friedrich Geist. I occasionally paid him short visits at his office in Berlin. He was a sensible man and not without charm. After the War ended I never heard of him again, except for the following information which was conveyed to me by Jan Vaagen in 1983: Apparently David Irving refers to him quite extensively in one of his books. I had no connections whatsoever with anyone of higher rank with regard to my work.

On the other hand, I did have a lot to do with a relatively small, private company which acted as mediator between those in Berlin financing my work, (which were the Air-Force or the Ministry of Aviation, the `Reichsluftfahrtministerium' RLM), and myself. The head of this small company was called Hollnack and he was a rather strange and somewhat highly-strung person. I remember he had a high regard for Nietzsche and probably (although we never spoke about it) also for Hitler. Apart from the betatron he appeared to have some other business with aluminium alloys, but this was of no interest to me. He administrated my Hamburg project. Hollnack (his first name was probably Theodor - he changed name after the War [Gi93]) claimed to have very good relations to high-ranking personalities in Berlin, and I suppose he let or negotiated contracts between the Ministry of Aviation (or other official bodies) and individuals or companies.

I met Hollnack one more time after the War in Waldshut (Germany), after he'd telephoned me. He wanted to claim rights on patents which had come about thanks to his `mediation' in Hamburg, but of course, that was not possible. All the patents I submitted at that time belonged to Brown Boveri Company BBC in Baden (as NEBB was a subsidiary of BBC) for whom I had already worked in Oslo.

Another very important colleague was Bruno Touschek. He worked mainly on theoretical calculations about the movement of electrons, their injection into rings and other effects. He was relocating from Berlin to Hamburg or, rather, was continually going back and forth between the two cities. Touschek was a very talented Austrian student of physics. He had worked for some time in the editorial department of `Archiv für Elektrotechnik' and had therefore come across my betatron suggestions before. He had also written to me on the subject. After he came to Hamburg I made his acquaintance at the house of Professor Lenz where he had taken up lodgings.

The editor of the Magazine `Archiv für Elektrotechnik' in Berlin was Dr.Egerer, who had previously worked for `Löwe' (later renamed `Opta'), where Touschek had also been employed part-time. Egerer may have prompted Touschek to contact me. I met Dr. Egerer some time later at Hollnack's. I imagine that's how the contact to Seifert and Kollath came about as well.

After a little while we realised that the best place to build the betatron was at the big X-ray-tubes and radio-valves factory called `C.H.F.Müller', also known locally as `Röntgenmüller'. Their buildings lay in the north of Hamburg, in Fuhlsbüttel, and had survived the bombings more or less intact. This factory, which was rich in tradition, had been founded in 1865 by the glass-blower C.H.F.Müller [Be90]. They also supplied X-ray-tubes for Seifert's materials testing devices. It has been owned by the Philips group (Eindhoven) since 1927 and still exists under the name `Philips Medizin Systeme GmbH'. At the time it seemed to be particularly well suited for developing the betatron: glass-blowing and vacuum techniques available were excellent. Construction started in October or November 1943. A working drawing of March 1944 at scale 1:1 is conserved in the ETH Zurich. The engineer responsible for that drawing was Friedrich Reiniger.

Some of our colleagues at C.H.F.Müller were very Nazi and pro-Hitler, among them the physicist Dr.Müller (no relation of the factory's founding family). He was the physicist WalterMüller (born 1905) who had developed the famous counter tube with Hans Geiger in 1928. However, Müller never used his first name to sign documents, only ever `Dr.Müller'. He was a nice and hard-working man, quite popular, but we were always very careful when we spoke with him. According to a later report by Herman Kaiser [Ka47], this Dr.Müller also submitted or prepared a series of seven patents for the betatron (file references are quoted), but I have no recollection of this. In the ETH Library Archives there is a fifteen page long report by Dr.Müller [Mu43] in which he expounds on the betatron as well as on its theory.

Every now and again I was permitted to leave Hamburg by air for holidays in Norway. The journeys were often a little problematic. Once, I think it was in December 1943, I was trying to get home for Christmas. We had to wait a long time in Denmark because of fog, but we arrived in Oslo just in time for the celebrations.

I eventually found out why the German Air Force was so interested in the betatron. Physicist Dr.Schiebold from Leipzig, a specialist on non-destructive testing of materials using X-rays among other methods (after the War he became professor in Magdeburg) had had the idea that it would be possible to build an X-ray tube with a concave cathode, a bit like a concave mirror. The electrons would then be focused on the anode and this would cause the X-rays to be emitted in a narrow bundle. With sufficiently high voltage it would then be possible to achieve high radiation intensities at long distances.

Thus it may even be possible to kill the pilots of enemy aircraft, or detonate their bombs. This was one of the `death rays'. With the `wonder weapons' of Peenemünde, the `death rays' had become an urgent necessity for war-time propaganda. At the time, the use of far reaching electromagnetic waves was probably quite conceivable since bomber planes were being precisely guided far over British territory by radio waves, i.e. electromagnetic radiation. The classic example was the night attack on Coventry which would have been inconceivable before.

See Box 8:   The Mysterious Death Rays.

It appears that Dr. Schiebold hawked his ideas about. He spoke to physicists who must have thought him a hopeless case, but he also tackled some influential people in official capacities who were not in a position to make informed judgements. Most people probably dismissed him as a harmless lunatic, but some must have been convinced because the Air Force, i.e. the German Aviation Ministry (RLM) and Command of the Luftwaffe, provided a certain amount of support for his `death ray'.

In order to conduct some test experiments for this `death ray', a still unused and unpacked X-ray apparatus with a high voltage supply of a little over one million volts (made by means of a sort of cascade circuit), was taken from a hospital in Hamburg to a small military airport called Groß-Ostheim (today `Großostheim') in the region of Hanau. If I remember rightly, Richard Seifert organized this tests and Hollnack was their administrator. However, both engineers and technicians quickly understood that the danger to themselves operating the machine on the ground was far greater than to the pilots and bombs in the enemy aircraft.

Still, a ray-transformer or betatron could produce X-rays of many million volts and in doing so one could, in principle (purely on the grounds of the laws of physics), improve the `bundling' of the beam with an increase of energy. To a certain extent, the effective range could be increased. This seemed to be the reason for the German Air Force's interest in the betatron. I wasn't really supposed to know anything about it, and we only ever talked about the betatron in terms of its importance to medicine. As it turned out this was actually correct.

By November 1943 I had developed a three-phase plan [Wi43c] which provided first for the construction of a 15 MeV betatron in Hamburg, then a 200 MeV betatron and finally an experimental station in Groß-Ostheim for even larger installations. Everything apart from the first phase obviously remained an illusion.

Our work in Hamburg soon confirmed that the step from Kerst's 2.3 MeV machine (USA) to our planned 15 MeV ray-transformer was the right one. Of course, all we wanted in principle was to achieve as much energy as possible, but at 15 MeV we did not expect any imminent problems with the iron yoke (which was very similar to that of an ordinary transformer). However, these problems did appear when we built the first 31MeV machine for Brown Boveri in Baden, as I shall explain later.

See Box 9:  Betatrons in Germany.

On one occasion I went to Rendsburg to visit my brother in prison. He was not at all well, he was suffering from some ailment, but I don't know what it was; most probably it was a manifestation of malnutrition, but it could have been pneumonia. I tried to cheer him up and to get him better treatment, but it turned out that the people with whom I was in contact did not have sufficient influence to have him released. Perhaps they did what they could, but it was not enough. Viggo was given slightly better food and later transferred to a penal colony near Darmstadt where he was permitted to work out of doors, chopping wood in the forest and digging over the soil in the garden, and I am sure that this helped him a lot. At the end of the War he was liberated from this camp by the Americans.

Working in Hamburg was not always without complications. We often had to flee to the basement during air attacks and would have to wait there until the danger had passed. When we came up again there was always a big question as to whether the betatron-tube was still sealed and sufficiently evacuated. However, my sojourns in the cellar also had their up-sides. Down there it was possible to think in peace about possible improvements and to let the imagination run free. This is where I thought up my `lens-road', a precursor of the `strong focusing' for particle accelerators which was introduced some time later. I also submitted these ideas for patenting, always helped by my friend Dr. Ernst Sommerfeld who took care of everything in Berlin.

Therefore the War and the limitations of our 15 MeV betatron gave me the opportunity to spend a lot of time in meditating about improved steering and focusing of particles in circular accelerators and in thinking up other new ideas.

Fig. 7.5:   Wolfgang Paul and Rolf Wideröe