Pierre Lazeyras 1931–2020

7 July 2020
Pierre Lazeyras

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.

Pierre graduated from the École supérieure de physique et chimie industrielle (ESPCI) in Paris in 1954 and, after working in Anatole Abragam’s group at CEA Saclay, he joined CERN as a staff member in October 1961. He was one of the early collaborators in the Track Chamber (TC) division, which built the two-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”.

Pierre directed the TC SPS neutrino beam group from 1972, which included the construction of the horns, the 185 m-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, 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.

Pierre was instrumental in the formation and success of ALEPH. From the conception of the experiment in 1982 right through to the LEP2 phase in 1996, he was ALEPH technical coordinator – a role that was quite new to those of us coming from smaller experiments. Pierre made sure we were realistic in our ambitions and our estimates of the difficulties and planning constraints, and we owe it mainly to him that the various parts of ALEPH were assembled without major problems. He was always available for advice even if, in his careful and reserved style, he did not try to direct or micro-manage everything.

In addition to being responsible for general safety in the experiment (which had no major incidents during its 11 years of operation), Pierre ensured that the construction of ALEPH was completed within budget. He also played an essential role at a crucial moment for the experiment in the early 1990s: the problem with the superconducting magnet cryostat. Under Pierre’s supervision, a vacuum 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 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.

Pierre was also involved in the design of the large stabilised superconductors for the LHC-experiment magnets and served as a member of the magnet advisory group of the LHC into his retirement, his wisdom being highly appreciated. He was also an active member of the CERN Staff Association. Following his retirement in 1996, he joined the Groupement des Anciens and was a representative on the CERN health insurance supervisory committee, where his advice and opinions 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.

bright-rec iop pub iop-science physcis connect