controllers of the historical cyclotron machine:

Some historical notes on our first Cyclotron

1. Memories of Hendrik B.G. Casimir

Interestingly, our first cyclotron is mentioned in the autobiography of Hendrik B.G. Cassimir (1909 – 2000), one of the most important Dutch physisist of the 20th century. He received his Ph.D. in theoretical physics under Paul Ehrenfest in 1931 and become physics professor at Leiden University in 1938. During World War II he moved to Philips Physics Laboratory, NatLab and became co-director of the research department in 1946. In this position he was closely involved in the development of the cyclotron.

Cover of the autobiography of the Dutch physicist Hendrik B.G. Casimir |
"Already during the war, C.J. Bakker and F. Heyn began to design a cyclotron, and they even began to order components, although the German supervisor had not given permission for building such a machine. I had little to do with this activity. I once had to receive the chief supervisor and some of his staff members and I had to show them the Circus. Fortunately, there had been time to wrap up the various components for the cyclotron, which were also stored in that hall. Leaning against one of the packages, I expressed my regret that we were not allowed to work on a cyclotron. After the war the original design was changed: the machine became a synchrocyclotron. Arrangements were made to install the cyclotron in Amsterdam; Bakker had acecpted a chair of physics in the university there. A small Philips group headed by Heyn also moved to Amsterdam.

The fact that our first cyclotron was now nicely accommodated at Amsterdam did not mean the end of cyclotron in Eindhoven. Several cyclotrons were manufactured at the factory in close collaboration with the research laboratory. To begin with, they were synchrocyclotrons, essentially copies of the Amsterdam machine; later, far more sophisticated 'isochronous' cyclotrons. Van Dorsen's team at the Nat. Lab. became highly proficient in designing such machines and in calculating exactly the required electric and magnetic fields. But there was permanent business in that area, the team was dissolved, two of its members became professor, at the Technical University in Eindhoven and the last prototype was donated to that same institution. 

This work on accelerators provided contacts with leading scientists and leading centers of research. On the whole such contacts were useful and pleasant but there could be awkward moments. For instance, during a visit to Oxford, I was taken to task by Lord Cherwell because of the poor quality of some of the components of a cascade generator. The complaints were justified, but during the rapid buildup after the war it was difficult to avoid such mistakes entirely. Anyway, there was little I could do about it, apart from speaking or writing to the man in charge of the factory.

A cyclotron was built for Irène Joliot-Curie. She came to Eindhoven to discuss details and I had dinner with her on that occasion. Unlike Lise Meitner, who was full of energy at seventy, she struck me as rather worn out. She died soon afterwards, on 17 March 1956, before the machine was completed.

Her husband took over; he survived his wife by no more than two years. He was only fifty-eight when he died, but I had the feeling that during the last years of his life he lived already very much in the past. He spoke mainly about the thirties, the heroic days, when Irene and he did the work that gave them a Nobel Prize, the days when the clan of active physicists was so much smaller. 

It was not without a feeling of regret that I saw Philips leave this field. I had not done much work in nuclear physics myself, but as a young theorist I had kept in touch with the developments of the thirties and I knew personally many of the leading figures of that exciting era. Joliot greeted me as an old friend, although we had not met very frequently, he recognized me as one of the clan. Now the links with such people and their laboratories were severed. My regret was not only a question of personal vanity and nostalgia. In the thirties Philips, on the basis of its technical competence, had been able to improve considerably on the original equipment of Cockcroft and Walton (see interview with van Leuffen). Later our isochronous cyclotrons were at least as good and in some ways better than the best university-built machines. But times were changing: in the field of accelerators Philips's competence was no longer superior to, and not even on a poar with, the competence of the most advanced centeres of 'big research'. And we could not afford to build up such competence. The cyclotrons had still been profitable but that was partly due to our way of calculating.

Every industrial division had to pay a fixed percentage of cost price for research, but the amount of research assistance given was at the discretion of the management of the research laboratory and was not rigorously determined by the amount paid. For cyclotrons the cost of the research effort involved was far in excess of the average percentage. That was acceptable as long as it was a question of starting a new activity; it could not be accepted as a permanent state of affairs. The 'small' cyclotron at CERN, a synchrocyclotron for 700 million volts, was already above our possibilities: we could not have afforded to construct a prototype of such a machine at out own risk, or for our own purposes. But at least we provided the high-frequency system. With the big accelerators we should have been utterly unable to assume a leading role. In this field scientific apparatus building had overtaken us and left us far behind." (290 – 292)

Source: Casimir, Hendrik Brugt Gerhard – Haphazard Reality: half a century of science, New York: Harper & Row, 1983.


2. Physics in the Netherlands
Cover of the book Physics in the Netherlands. A selection of dutch contributions to physics in the first 30 years after the second world war, edited by C. Le Pair and J. Vogler |

"The best-known resonance accelerator ist the cyclotron, in which a magnetic field is used to guide the particles in circular paths so that they cross the same gap many times.
The betatron is an accelerator in a class by itself, though it is cyclic, depending on a magnetic field to hold the particular in circular orbits. But there is no synchronization of accelerating voltage with the rotation of the particles, because there is no accelerating voltage alternating or otherwhise. Instead the acceleration is provided by the induced electric field around a changing magnetic flux. Radial decrease of the magnetic field and relativistic increase of mass of accelerating particles have necessitated correction measures on the simple fixed-frequency cyclotron. This is accomplished in the synchrocyclotron by periodic decreasing of the frequency of the accelerating voltage." (338)

Major accelerator facilities for nuclear physics research in the Netherlands (Cyclotrons):

|_. City |_. Type |_. Diameter |_. Year of operation |
| I.K.O./Amsterdam | synchrocyclotron | 1.50m | in operation 1949 – 1973 |
| V.U. Amsterdam | A.V.F. cyclotron | 1.40m | in operation since 1966 |
| T.U. Eindhoven | A.V.F. cyclotron | 1.40m | in operation since 1969 |
| K.V.I. Groningen | A.V.F. cyclotron | 2.80m | in operation since 1972 |

Source: Le Pair, C, Vogler, J. (ed.) – Physics in the Netherlands. a selection of dutch contributions to physics in the first 30 years after the second world war, Vol. 1, Utrecht: Foundation for fundamental research on matter, 1982, page 339.