Bernard Jacrot (1926-2016)

Bernard Jacrot died peacefully in his ninetieth year on the 21st of January. His lifetime spanned across an epoch of great political, cultural and scientific transformation. An epoch he embraced fully as a passionate witness who continued to read the papers every day. He played an important role in the brave beginnings of neutron scattering in condensed matter physics in the nineteen fifties, international scientific collaborations in the sixties and structural biology in the seventies and eighties. His scientific legacy is very much alive through the interdisciplinary applications of neutron scattering that he pioneered.

Jacrot followed ‘classes préparatoires’, the two years after the baccalaureate preparing for competitive entrance in the Grandes Écoles engineering schools, in Dijon and at Lycée Louis le Grand in Paris. He entered École Polytechnique in 1947. After graduation, he joined the CEA establishment in Saclay, where a small reactor had just been built. Scientific research in France required serious rebuilding after the war. And it was owing to initiatives like the Summer School of Theoretical Physics at Les Houches that young physicists could be brought up to date in modern physics. Jacrot attended the Les Houches session of 1954, where he took the iconic photograph of Enrico Fermi writing on the blackboard in his mountain hiking clothes. But by then Jacrot had already published important work.

Jacrot’s first paper on neutron absorption by a flat sample appeared in 1952; like most of his early work it was written in French. The following three papers, with Magda Galula and Francis Netter, are on the fission cross-section of plutonium for slow neutrons, on the Saclay Double Chopper time-of-flight spectrometer (mentioned by Brockhouse in his Nobel lecture) and on the neutron spectrum of the Saclay reactor. Jacrot was among the few who initiated the application of inelastic neutron scattering to the then revolutionary science of condensed matter physics. Between 1955 and 1965, he combined instrumental advances and applications to explore physics as diverse as inelastic scattering in crystals, magnetism, critical scattering in iron, rare earth oxides, optical phonons in crystals and water self-diffusion. In 1964, Cribier, Jacrot, Rao and Farnoux published (in French) the first experimental observation of a vortex lattice in type II superconductors in Physics Letters. Abrikosov wrote in his Noble lecture: “… I published my paper in 1957 [10]. Even then it did not attract attention, in spite of an English translation… Only after the vortex lattice was observed experimentally, first by neutron diffraction [11]… they had no more doubts.” Reference [11] is the 1964 Physics Letters paper. With Riste, Jacrot contributed the magnetism chapter to the book edited by Egelstaff that presented the state-of-the-art of neutron scattering in condensed matter physics by 1965.

Jacrot, considered among the founding fathers of French neutron scattering, was reluctant to speak about himself. When I met him in 1974 he had already switched to biology. I learnt about his role at the beginning of the Institut Laue Langevin from his book Neutrons for Science and at the memorial organised by ILL in his honour on 2nd May. In their testimony his past colleagues brought forward not only his scientific and technical achievements but also his profound humanism. Jacrot was part of the group that first proposed the ILL at the Geneva conference in 1964. German physicists and in particular Maier-Leibnitz saw in the ILL project a concrete political act, encouraged by Adenauer and De Gaulle, to launch France and Germany on a common scientific adventure. French neutron scatterers were fascinated by the technical achievements promised by the collaboration. Yet when the Grenoble site was chosen under the influence of Néel, many in the Saclay group were reluctant to move away from the Paris area, where careers are made and unmade. Jacrot was ready and willing. He was given leave-of-absence from the CEA and named the first French associate director of ILL. With Maier-Leibnitz, they recruited the young German and French scientists and engineers who designed and built a new generation of instruments (some of which were politely considered to be ‘odd’ by other neutron scatterers) and set up the policy that opened up the ILL to other than neutron specialists (which was considered unacceptable to other neutron centres, before they too came round to this way of operating). Reinhard Scherm (who designed the IN5 spectrometer, which is still operational after several upgrades, and, years later, became German director of ILL) arrived in Grenoble during the building period. He recalls how he was driven in Jacrot’s Citroen DS to visit laboratories around France, where they introduced neutron scattering opportunities. A disagreement with the CEA hierarchy during Jacrot’s time as associate director had important consequences and gives us a glimpse into his character. In the process of choosing the computer system for ILL, Jacrot received the order from CEA ‘head-office’ to buy French. He dryly retorted that the ILL would buy ‘the best’, irrespective of country of origin. The reaction of the CEA was immediate: if the ILL did not buy French, it would be the end of Jacrot’s career at CEA. The ILL chose DEC computers and Jacrot was going to be out of a job after the end of his contract with ILL. Was it because of this that he decided the scientific move to biology? It was not the first time that Jacrot stood up against the establishment. He had been banned from ever receiving the Légion d’Honneur by his refusal to remove his name from a petition defending the mathematics professor who had been fired by Polytechnique because of his Left Wing views. It created an embarrassment when the French Republic awarded the medal to Maier-Leibnitz for his contribution to the ILL. I heard that the German government stepped in to decorate Jacrot but could find no official trace of this.

In 1973, he left Grenoble with wife and children to spend a year in Cambridge to ‘learn’ biology. Members of Aaron Klug’s virology group fondly remember Jacrot’s sabbatical year. Bernard brought with him his enthusiasm and relaxed joie de vivre, together with a strong belief that there were great discoveries to be made by applying the full breadth of physical methods to biological structure analysis. His experience with neutron diffraction and eagerness to learn about X-ray crystallography and electron microscopy contributed to lively teatime discussions for most of the year of his visit. Teatime—when scientists including a number of current and future Nobel prizewinners, technicians, students, met and chatted about science and other things. Jacrot was radically influenced by this atmosphere of open discussion and by the universal culture of Perutz and Klug, whose families had warmly welcomed his own.

He returned to ILL as senior scientist for biology determined to introduce the interdisciplinary physics/biology approach that also paved the way for neutron scattering in soft condensed matter. It was not an easy task. I remember, for example, the opposition to buying a simple spectrophotometer to measure the concentration of biological solutions before a D11 SANS experiment. Against such resistance, Jacrot patiently imposed structural biology on the site, first as ILL senior scientist then as director of the EMBL outstation. He wrote a review of small angle scattering in biology that because of its clarity is still consulted today and, as he had done at the beginning of the ILL, he visited labs to introduce neutrons to biologists in a language they could understand. He established a group in structural virology that published extensively on the molecular and structural biology of adenoviruses, which and was among the first to move to the new Institut de Biologie Structurale. He was involved in the committees that discussed ESRF structural biology beam-lines. He was appointed to the management team of the Life Sciences at CNRS and contributed significantly to the development of structural biology in France. He lectured at Les Houches on the relations between physics and biology and wrote a book on the subject. And in Neutrons for Science he wrote the history of ILL.

Jacrot retired in the Luberon, surrounded by his collection of first editions and beautiful books—books that he enjoyed buying and reading until the last weeks of his life. He is survived and mourned by Christophe and Michèle, his son and daughter from a first marriage, Micheline, his wife and her son and daughter, Jean-Frédéric and Valérie and her children.

Joe Zaccai (10th May 2016)