Pierre Lazeyras, who played leading roles in the ALEPH experiment, neutrino beams and silicon detectors during a 35-year-long career at CERN, passed away on 4 April aged 88.
Born in Limoges, France, in July 1931, Pierre graduated from the École supérieure de physique et chimie industrielle (ESPCI), Paris, in 1954. After working in Anatole Abragam’s group at CEA Saclay, he joined CERN as a staff member in October 1961. Pierre was one of the early collaborators in the Track Chamber (TC) Division, which built the 2-metre bubble chamber and the Big European Bubble Chamber (BEBC). In parallel, he headed the team that developed one of the first superconducting bending magnets for BEBC’s “beam s3”.
In CERN’s early days, it was not always clear if a particle-beam apparatus would be built by the accelerator specialists or by the experiment support teams. In the TC Division, Pierre’s group designed some of the beams for the bubble chambers at the PS; later, the SPS neutrino beams were also supervised by teams in the TC Division. Pierre directed the TC SPS Neutrino Beam Group from 1972, which included the construction of the horns, the 185-metre-long iron muon shielding and the beam monitoring, for which silicon-diode particle detectors were employed. After some initial teething troubles, the SPS neutrino beams operated for nearly 20 years without major problems. The silicon monitors were found to be more precise than the early gas-filled ion chambers, but calibration remained an issue. Muon counting rather than charge integration seemed an option, and this was the beginning of the era of silicon micro-strip detectors. Pierre encouraged the microelectronics developments for this new technology and its integrated readout circuits. These advances also came just in time for the UA2 experiment at the SPS and for wider applications in the LEP experiments, ALEPH in particular.
Pierre was instrumental in the formation and success of the ALEPH experiment, and was unanimously appreciated. The collaboration benefitted from his experience on large projects and his good knowledge of and connections at CERN. From the conception of the experiment in 1982 right through to the LEP2 phase in 1996, Pierre was ALEPH Technical Coordinator. For most of us coming to ALEPH from smaller experiments, the idea of a technical coordinator was quite new, but very rapidly we appreciated the role that Pierre played. From 1983 to 1989, each group in the collaboration was building a different part of the detector. Pierre made sure we were realistic in our ambitions and our estimates of the difficulties and planning constraints and, crucially, had an overview of whether each sub-detector would fit in the overall experiment. Pierre came to each sub-detector meeting and we owe it mainly to him that the various parts of ALEPH were assembled without major problems. Pierre was always available for advice even if, in his careful and reserved style, he did not try to direct or micro-manage everything. However, when asked for help he generously gave his full support.
As the person responsible for general safety in the experiment, Pierre carefully controlled these aspects, and ALEPH had no major incidents during its 11 years of operation. He was also in charge of the overall budget and certainly contributed to the fact that construction was completed within budget. After the commissioning of the experiment in 1989, Pierre’s role was less day-to-day but he continued to oversee the budget for improvements and maintenance. He also played an essential role at a crucial moment for the experiment: the problem with the superconducting magnet cryostat. Pierre had always insisted that such a huge superconducting magnet and cryostat inherently constituted a fragile device, and had objected to the idea of warming up the magnet during annual shutdowns, citing the mechanical stress resulting from this procedure. He was absolutely right. In April 1993, there were signs of a vacuum leak, which curiously disappeared but came back in January 1994. Under Pierre’s supervision, the leak was located, close to the edge of the magnet, and the cryostat then underwent “surgery” using a milling machine suspended from a crane. It was a wonderful exercise in imagination and, to the relief of all, a complete success.
Pierre was also involved in the design of the large stabilised superconductors for the LHC experiment magnets. He was therefore a natural candidate for the Magnet Advisory Group of the LHCC, on which he served into his retirement, his wisdom being highly appreciated.
He was an active member of the CERN Staff Association. When he retired in 1996, he joined the Groupement des Anciens and became involved in October 1997 as a representative on the CERN Health Insurance Supervisory Committee, which has since become the CHIS Board. For 14 years, until December 2011, the Committee benefited from his enlightened advice and appreciated his opinions, which were always wise and measured.
Pierre was not only highly talented and used his experience most effectively, he was also a warm person, someone on whom one could always rely. He would always tell you straight how things were and then suggest how any problems could be tackled. A typical remark by Pierre would be: “ask me to approve or reject your ideas, do not ask me what work I have for you”. We will remember him as a very dear friend and colleague.
His friends and colleagues at CERN