• Cécile DeWitt-Morette 1922–2017 • Charles Gruhn 1935–2017 • Gerhard Lutz 1939–2017

Cécile DeWitt-Morette 1922–2017

Cécile DeWitt-Morette, founder of the Les Houches summer school, passed away on 8 May at the age of 94. Born in Caen, she studied in Paris after completing her bachelor degree. In 1944 her mother, sister and grandmother were killed in the Allied bombing of Caen, but in Paris she secured a job at CNRS and was awarded a PhD three years later with a thesis about meson production. She was then invited to the Institute for Advanced Study in Princeton by Robert Oppenheimer, where she met her future husband, the US physicist Bryce DeWitt (they would go on to have four daughters).

Mixing with the best of US physics made her realise the poor situation of the field in France, especially particle physics, and drove her to do something about it. Precisely at that time, a summer school was organised at the university of Michigan in Ann Arbor, and Cécile had the idea to create such an event in France. Her beautiful eyes with double-iris rings and considerable powers of persuasion, not to mention a fantastic intuition for selecting the best possible lecturers, were difficult to resist. She had a friend whose father, the architect Albert Laprade, loaned her a piece of land at La Côte des Chavants, just above the village of Les Houches in the Arve valley, among farms and cottages. Financial input soon followed thanks to her skilful negotiating tactics, and in the summer of 1951 I was one of a few candidates to attend the school for a period of three months. She had chosen fantastic professors: Léon Van Hove for quantum mechanics and Viki Weisskopf for nuclear physics, both of whom would be future Director-Generals of CERN; Res Jost for field theory; Walter Kohn (a future Nobel Prize winner) for solid state physics; plus seminars by giants such as Wolfgang Pauli. We worked very hard, except for some excursions in the mountains, and learnt a lot.

The Les Houches school, of which Cécile remained director for 22 years, continued to be a complete success. Many of its students and some teachers received the Nobel prize, the Wolff prize or the Fields Medal. Among them were Pierre Gilles De Gennes and Claude Cohen-Tannoudji. The demand for basic courses dissipated over the years, but the school became a place for high-level specialised topics, and continues to be so.

Cécile also played an important role in founding the Institut des Hautes Scientifiques (IHES) in Bures sur Yvette, and did important work on functional integration, also collaborating with her mathematical-physicist husband. They were professors at the University of North Carolina at Chapel Hill and at the University of Texas at Austin, successively. Bryce died in 2004 just as he was about to receive the Einstein Prize from the American Physical Society.

I met Cécile for the last time at IHES in 2011 where she was made Officier De la Légion dʼHonneur. On 7 May, the day before she died, I understand that she was delighted to learn that the anti-European candidate as president of France, Marine Le Pen, had been defeated.

• André Martin.

Charles Gruhn 1935–2017

Charles Gruhn, a long-time colleague and friend for many of us at CERN and elsewhere, passed away peacefully on 24 March. Chuck, as he was known, obtained his PhD from the University of Washington, Seattle, in 1961, and throughout his professional life he worked on the development of particle detectors and their associated electronics.

Chuck started his scientific career at the Massachusetts Institute of Technology, where he worked on nuclear reactions and on studies involving alpha particles, and in 1964 he moved to Michigan State University. His development of detectors included lithium-germanium counters, silicon semiconductors and a Ge(Li) Compton spectrometer. He also performed a large variety of proton-scattering experiments.

In 1970 he took a sabbatical at the Max Planck Institute for Physics in Munich, which was working in close contact with CERN at the time. After a short period, CERN offered him an indefinite contract, which he accepted. Since Chuck was a US citizen, this was a very rare exception for a physicist who was not from a Member State. He immediately became involved in experiments at the Intersecting Storage Rings, which recorded its first proton–proton collisions in January 1971. His work on detectors was centred on silicon semiconductors and on multiwire proportional chambers within the group of Georges Charpak. His main topic in physics was the search for fractionally charged particles indicating a signal for free quarks.

Chuck left CERN to work for three years at the Los Alamos National Laboratory in the US, where he carried out further studies on silicon semiconductor detectors and worked on the development of liquid ionisation chambers. He also received a US patent for his development of laser-beam alignment systems. In 1978 he moved to the Lawrence Berkeley Laboratory (LBL) in California, where he was a professor until his retirement in 1992. LBL was deeply involved in CERN experiments and this allowed Chuck to spend most of his time at CERN, continuing to work on the Split Field Magnet experiment at the ISR. After the closure of the ISR, he participated in CERN’s heavy-ion programme in the search for the quark–gluon plasma with the NA36 experiment. He made major contributions to the design and operation of the time projection chamber, including the role of tracking in relativistic heavy-ion experiments.

After his retirement from LBL in 1992, Chuck became a consultant for the ATLAS experiment under a contract with the MPI Munich. He was the first to study the characteristics of single proportional drift tubes, to be produced later on in hundreds of thousands to form the ATLAS Muon Spectrometer, and was our main adviser during the development and testing of the first prototype chambers at the MPI.

Although suffering from heart problems, Chuck stayed active for many years to come. His main remedy against health problems was extensive hiking on the Jura mountains.

His principal scientific interest during his later years was astronomy and the study of binary stars. He developed methods for their observation, photography and analysis at home with private telescopes, recording real data once a year at the International Amateur Observatory on the Gamsberg in Namibia. Chuck’s observations found many acknowledgements due to their high-level professionalism.

Besides the many achievements in his brilliant scientific career, we would like to recall his fine personal qualities. Above all, his greatest quality was perhaps that he was simply a nice person. Our deepest sympathy goes to his wife Ute, their children and families.

• His friends and colleagues.

Gerhard Lutz 1939–2017

One of the pioneers of silicon radiation detectors, Gerhard Lutz, passed away in Vienna on 28 April. He will be remembered for numerous inventions that shaped the field of silicon detectors, his deep insight into detector physics and analysis methods, his role as mentor of many young scientists, and his modest and charming personality.

Gerhard Lutz was born in Klagenfurt, Austria, in 1939. He studied physics at the Technical University of Vienna and obtained his PhD from the University of Hamburg under Willibald Jentschke, the founder of DESY and later a Director-General of CERN. His thesis concerned the coherent bremsstrahlung and pair production on diamond crystals using the DESY synchrotron, and demonstrated the production of GeV photons with a polarisation in excess of 70%. In 1967 he moved to Northeastern University in Boston and contributed to a spectrometer experiment at Brookhaven, which had aimed to follow up spectacular results reported earlier by the “CERN missing mass spectrometer”: the splitting of the A2 resonance and the observation of narrow high-mass resonances. Based on high-quality data and a painstaking analysis, he showed that the CERN results were incorrect.

In 1972, Lutz took a position at MPI-Munich and initiated a precision measurement of the reaction π p()  π π+ n. He organised and ran the experiment, wrote the event-reconstruction software and developed the complex mathematical formalism necessary to interpret the results – marking a milestone in the understanding of exclusive hadronic reactions. In the late 1970s the CERN–Munich Group expanded into the ACCMOR collaboration, which pioneered the use of high-precision silicon tracking detectors. Together with Josef Kemmer and Robert Klanner, he developed silicon microstrip detectors using planar technology and built the vertex telescope for the CERN fixed-target experiments NA11 and NA32. The achieved precision of this device (5 μm), its ability to operate reliably in a high-intensity beam and identify charm particles against a huge background of hadronic events, unleashed the success story of silicon detectors. Today, practically all high-energy physics experiments rely on this technology.

Lutz’s contributions in the field of silicon detectors are numerous: the understanding of detector instabilities due to surface effects; the development of double-sided silicon-strip detectors; the concept of fully depleted pnCCDs based on the principle of sideway depletion; the realisation of novel concepts for silicon sensors with intrinsic gain; and the invention of the DePFET detector-amplifier structure. His developments found their way into many experiments outside particle physics, in particular in astrophysics and X-ray science, and also industry. Lutz co-founded the Max-Planck-Institut Halbleiterlabor (HLL) semiconductor laboratory in 1992, the research company PNSensor in 2002, and the instrumentation company PNDetector in 2007. Until the very end he contributed to the success of both companies with his sharp mind and inventions, while his guidance, inspiration and ideas have been essential for the success of semiconductor developers in the Munich area.

Those who had the opportunity to work with Gerhard Lutz appreciated his gentle and quiet way, his competence and deep insight. His scientific standards were very high and he detested superficial statements. His unconventional and original ideas inspired many colleagues and students, and his book Semiconductor Radiation Detectors has become a classic in the field. Gerhard Lutz’s innovative and influential work was honoured by the 1966 Röntgen Award, the 2011 Radiation Instrumentation Outstanding Achievement Award, and the 2017 High Energy Physics Prize of the European Physical Society (see “EPS awards prizes for high-energy physics”).

• His friends and colleagues.