Joseph Rotblat's Archive: Some Anomalies and Difficulties

By Martin C. Underwood, Dept. of Physics, Sub-dept. of Particle Physics, University of Oxford
and Dept. of the History and Philosophy of Science, University of Cambridge


Professor Sir Joseph Rotblat was a distinguished scientist who made significant contributions to nuclear physics, worked on the development of the atomic bomb (he was the only scientist to leave the Manhattan Project where these weapons of mass destruction were being developed) and was suspected of being a soviet spy. Rotblat was appalled when nuclear weapons were used on Hiroshima and Nagasaki, although he did work, albeit for a short time, on their development and in his view with little impact. Instead he dedicated himself to the medical uses of nuclear physics and radiation, taking up the post of Professor of Physics (as applied to medicine) at St. Bartholomew’s Medical College and made major contributions to this field, becoming one of the world’s leading researchers into the biological effects of radiation. Rotblat was to develop the view that scientists were responsible for the consequences of their work and scientific research should be for the benefit of humanity, a driving principle in his life and work being that scientists cannot dissociate themselves from the consequences of their work, however difficult to predict.

Joseph Rotblat worked at the University of Warsaw, discovering inelastic neutron scattering. He was invited in 1939 to work at Liverpool University with James Chadwick. Towards the end of 1939 Rotblat began experiments in Liverpool which demonstrated that the nuclear bomb was feasible. At the beginning of 1944 Rotblat joined the Chadwick group at Los Alamos, New Mexico to work on the Manhattan Project, which was developing the atomic bomb. At the end of 1944 he resigned and returned to England.1

In this paper I describe some new findings that will lead to a reappraisal of some aspects of his life and work. This has become possible as a consequence of funding from The Friends of The Center For The History of Physics at AIP, allowing me to consult Rotblat’s Archive that is now becoming available, housed in the Churchill Archives Centre, Churchill College, University of Cambridge. Many insights and anomalies have already been uncovered and in this short summary I describe some of the findings, to date.

The Manhattan Project

In his seminal paper 'Leaving the Bomb', Rotblat says 'And so, on Christmas Eve 1944, I sailed for the United Kingdom....I packed all (emphasis is mine) my documents-research notes as well as correspondence and other records in a box....Chadwick personally helped me put the box on the train to New York. But when I arrived there a few hours later, the box was missing. Nor, despite valiant efforts, was it ever recovered.'2

The Archive contains, much to my surprise, a considerable body of papers from Rotblat’s time at Los Alamos. In summary, these papers contain:

Plan of an experiment to determine the capture cross-section of 235U3

    1. A method for neutron energy measurements4

    2. Notes on an experiments to determine some nuclear constants3

    3. Monthly report5

The discovery of these papers is a significant finding as it is totally at odds with Rotblat’s account of events. It could be that Rotblat was simply mistaken, reporting over 40 years after the events, the papers could have been removed by someone else, possibly Chadwick, but this is only speculation. This contradiction will be the subject of future work.

St. Bartholomew’s Medical College

Following his return to Liverpool University in late 1944, Rotblat started to change the direction of his research activities. Perhaps, in part, as a reaction to the horrors of the use of the atom bomb on Hiroshima and Nagasaki, he became involved in the medical uses of radioisotopes and radiation in diagnosis and treatment. This culminated in his accepting the post of Professor of Physics (as applied to medicine) St. Bartholomew’s Medical College, London University. The hospital housed a 15 MeV linear accelerator, used for treatment that was employed for research when not being utilised for clinical purposes. Rotblat, however, wanted an accelerator devoted solely for research. He succeeded and a full assessment of the performance of this machine can now be made from papers contained in the Archive.6

An order was placed with Vickers in May 1961, and delivered to site in July 1963 and assembled by December of that year. The specification called for a 5 micro-second pulse at 100 pulses per second. Vickers carried out trials during 1964 and obtained a pulse length of 1.7 micro-seconds at full power. A new wave guide was fitted in 1965 and Vickers claimed a beam of electrons at an energy of 14.6 MeV and a current of 750 mA. St. Bartholomew’s staff measured the energy to be 11.8 MeV. In October 1965 it was agreed that an independent measurement should be sought and Barts agreed to take the machine if it performed within 10% of the specification. Independent assessors from the Rutherford Laboratory were appointed and carried out energy measurements in June 1966, after a new klystron was fitted. The energy was measured at 13.5 MeV at a current of 750 mA which was just within the agreed acceptance limits.

The machine was subject to frequent breakdowns and not fit for day to day running and research. Bart’s wanted a complete independent assessment of the machine but Vickers refused. In 1967 the S.R.C. were brought in for a final arbitration and the Rutherford Laboratory recommended acceptance of the machine in March 1968. However, some months later the klystron burnt out and a replacement was purchased with an S.R.C. grant. Various attempts were made to run the machine from July 1968 to March 1969 which failed due, largely, to arcing in the waveguides. In March 1969 the klystron burnt out again after only 485 hours of operation. A new klystron was eventually purchased from hospital funds but funding ceased in September 1976. Some student-based research work was undertaken, but the machine was not a success.

The Vickers 15 MeV linear accelerator installed in St. Bartholomew’s Medical College in 1963 was plagued with problems from the outset. Independent assessors were appointed to review the machine, but Bart’s agreed, it can be argued, an acceptance criterion that was not stringent enough. When Barts wanted additional outside, independent opinions as to the performance of the machine, Vickers were not pressed hard enough to agree to this. At one point, Thompson-Varian did not honor the guarantee covering the performance of the klystron and hospital funds were used to purchase a replacement. The manufacturer claimed that the klystron was running at too high a current and therefore out of specification. There is no evidence in the Archive of these claims being challenged. Project management was simply not careful and tight enough. Norman Kember, who succeeded Rotblat as Head of the Academic Department in St. Bartholomew’s Medical College (and later appointed Professor) said in relation to this machine and Joseph Rotblat, that 'great men are allowed to make great mistakes'7 and only one research paper was produced.


I am very grateful for the help provided by the staff of The Churchill Archives Centre, Churchill College, Cambridge University and the Listening Service Team of The British Library Sound Archive. I very much thank The Friends of The Center for The History of Physics, The American Institute of Physics for financial support. I would also like to acknowledge and thank Professor Robin Devenish of The Sub-Dept. of Particle Physics, Dept. of Physics, University of Oxford and Professor John Forrester of The Dept. of The History and Philosophy of Science, University of Cambridge for allowing me access to their respective Departments.


1. For an account of his life and work see Underwood. M (2009). Joseph Rotblat: A Man of Conscience in the Nuclear Age, Sussex Academic Press.

2. Rotblat. J (1985). Leaving the Bomb. Bulletin of the Atomic Scientists, reprinted in Underwood. M (2009). Joseph Rotblat: A Man of Conscience in the Nuclear Age, Sussex Academic Press.

3. Rotblat. J (1944). Churchill Archives Centre, The Papers of Joseph Rotblat, RTBT, D.53A.

4. Rotblat. J (1944). Churchill Archives Centre, The Papers of Joseph Rotblat, RTBT,D.53B.

5. Rotblat. J (1944). Churchill Archives Centre, The Papers of Joseph Rotblat, RTBT, D.52C.

6. Rotblat. J ( 1975). Churchill Archives Centre, The Papers of Joseph Rotblat, RTBT, C.156.

7. Kember. N (2006). ‘Personal Reminiscences from St. Bartholomew’s’. In (Eds) Rowlands. P & Attwood. V (2006). War and Peace: The Life and Work of Sir Joseph Rotblat, The University of Liverpool Press, p165.

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