Neutrons for Science

Neutrons for Science The story of the first forty years of the Institut Max von Laue-Paul Langevin, Grenoble 1967-2007 a successful European Cooperation Bernard Jacrot Originally published as : Des Neutrons pour la science ISBN 2-86883-878-2 EDP Sciences, Paris, 2006 Translated from the original French by Ron Ghosh The text has been translated from the French version dated 9th December 2005, corrected in February 2007. This English version was last amended on 11th May 2016. ii Contents Introduction 1 1. Forerunners to the ILL: OECD, Euratom, CERN 3 2. The three principal architects who created the ILL 15 3. Why invest so much money for a Neutron Source? 27 4. The Negotiations 37 5. The construction of the reactor and formation of the Scientific Groups 47 6. The start of research activities and the arrival of the British 71 7. The ILL matures; an EMBL outstation is created, and the ESRF is established on the site. 79 8. The Dark years 89 9. Consolidation and the future 95 Conclusions: an Appraisal 99 Acknowledgements 107 Chronology and key people in the history of the ILL 109 Appendices 113 The French-German intergovernmental agreement The visit of members of the UK-SRC in March 1970 The report by Maier-Leibnitz in 1968 Memorandum by B. Fender on installing the ESRF on the ILL site The announcement in 1991 by R. Newport that the UK would reduce its contribution to the ILL Ipoustéguy’s interpretation of the sculptural work he made for the ILL Translator’s note 129 Index 131 iii iv Introduction – why write a history of the ILL? The Institut Laue-Langevin, or more formally the Institut Max von Laue-Paul Langevin (ILL) is one of the first examples of fully successful scientific collaboration between European countries. It was preceded only by CERN, the European Centre for Nuclear Research, and by EURATOM whose origins lie in the first years after World War II. The history of CERN, created in 1953, has been described in a massive work of 3 volumes1. EURATOM was established as part of the Treaty of Rome, in 1957. To my knowledge its history has not been published. Perhaps this is a consequence of the somewhat mixed success of this organisation. In contrast to the creation of CERN, where the USA scientists played an important role, the ILL was a purely French and German initiative. Such a combined activity was far from evident between two countries which had battled, one against the other, and that the Institut should be placed in a region of France where the Resistance had its pinnacle position in the Vercors mountains. The name of the road to the ILL, the Avenue des Martyrs, bears witness to these events. How this all became possible is one of the themes which I will develop in this book. In current times where there is increased scepticism over the future of Europe I feel it is of use to show how this collaboration has progressively become European-wide (there are now 10 countries involved and this number is increasing). The driving force has been the success achieved together being far better than any country could have obtained alone. This book will attempt to show that the ILL has allowed Europe to surpass the USA in an important field of research thanks to a specific tool – a research reactor with a uniquely high continuous neutron flux – which even today is unequalled in the world. It is important to understand what led up to this success. The prehistory of the ILL goes back more than 40 years. Thus many contributors to this slow gestation which led to the construction of the Institut and its reactor are no longer alive. There remain those (notably the author) who, though all in retirement, can still harvest the evidence, though this needs to be done quickly to include in a complete history. However, this book is the work of a scientist who has no training as a historian, and who has learnt of the difficulties of this metier. The path of truth is as important in history as in physics, and calls for use of all available methods. One learns the need to recover the evidence, which is not always possible when the witnesses become sparse. The work was further complicated by the absence of archives at the ILL (and at the CENG, the Centre d’Etudes Nucléaires de Grenoble). There isn’t even a complete collection of ILL activity reports. Happily my own personal archives remained, some being rediscovered in a cupboard at the ILL. Hence this history cannot be entirely objective. After the first version of this text was finished, a book was published by the Greek scholar and philosopher Jean-Pierre Vernant, La traverse des frontières [Paris, 2004]. He analysed the problems posed for those writing up recent events, and concluded that it is not possible to write a true history if we take into account the subjective nature of all the evidence, even if this is given with perfect honesty. I have tried to do my best. I have had no responsibilities at the ILL for more than thirty years, and have been retired for more than ten. Hence I feel free to write the whole truth, even if, in a few 1 History of CERN, by A. Hermann, J. Krige et al, 1987-96 ; North-Holland Physics Pub. and Elsevier. 1 rare cases, this is not politically correct. This is a test edition, because a time will come when true professionals will take up this work again, and will explore archives unknown to me. These will remain their only source; there will no longer be any remaining living witnesses to the creation of the ILL. I can add that it gave me great satisfaction to complete this book since it is always a pleasure to reflect on a successful enterprise to which one is proud to have contributed. The creation of a scientific institution involves human interplay, with all that this entails, including conflicts between various members of the cast. Personality and charisma can play a fundamental role. For a scientific company, charisma necessarily involves an important component based on scientific credibility. I will try to highlight the human aspect in the history of the ILL. In particular I would like to try and paint a picture of three of the main actors in this story, three strong personalities Jules Horowitz, Louis Néel and Heinz Maier-Leibnitz, alas all now deceased. This book should not look like a report of a scientific meeting which only gives the conclusions of the discussions, erasing all the discussions that led to arrive at these conclusions. Where they exist such minutes are essential since they provide the framework for adding the human elements from memories of surviving witnesses. Since the ILL is a scientific establishment this requires some explanation of the research studies which are undertaken. These studies impact on a large number of scientific domains, from nuclear physics to biology; I will try and render the aim of this work, and the results, understandable to the non-specialist. 2 Chapter 1 Pre-history The neutron was discovered in 1932 by James Chadwick. It is a neutral particle with a mass very close to that of the proton, both of which are constituents of atomic nuclei. The free neutron is produced in certain nuclear reactions. The first, which led to its discovery, was the collision between alpha particles and the nuclei of beryllium 4He+ 9Be → 12 C+ n During initial years of study it was this reaction which was used in the construction of neutron sources. Such a source led to the discovery in 1939 by Hahn and Strassman that the nucleus of uranium would undergo fission, induced by capturing a neutron. It was shortly noted that this fission process, in addition to producing energy, was accompanied by the emission of about two new neutrons; theoretically this could lead to a chain reaction. The origin of the energy evolved was the loss of mass occurring during the fission reaction. This mass m is transformed into energy E following Einstein’s equation: E = mc2 where c is the speed of light. Such a reaction could lead to a new source of energy. The first practical realisation of the controlled chain reaction was achieved at the end of 1942 by Enrico Fermi in Chicago, USA. At that time the US was at war, and was working on the development of the atomic bomb, a more brutal way to implement this same chain reaction. All this work, including Fermi’s was hidden with the greatest secrecy under the codename “Manhattan Project”. The neutrons accompanying fission have energies of the order of 1 million electron volts (MeV); it was quickly understood that when these particles hit nuclei of other atoms, notably those of small atomic mass, that the neutron lost energy, and slowed. After several collisions the neutrons formed a sort of gas in thermal equilibrium with the medium in which they found themselves. These neutrons are known as thermal neutrons. The chain reaction is maintained by the fission being more favourably induced by these thermal neutrons. It follows that most nuclear reactors comprise a moderator of light material, with low neutron absorption (very pure graphite, light water, heavy water) arranged around and between bars of uranium. Fermi used graphite to construct the first reactor. Neutrons have a wavelength as defined by the de Broglie equation relating to their velocity (hence energy) λ = h/mv Here h is Planck’s constant, m is the mass of the neutron and v its velocity.

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