He joined the French Alternative Energies and Atomic Energy Commission (CEA) in 1970, as an engineer. He was promoted to the position of director of the Particle Physics Section of the Department of Astrophysics, Particle Physics, Nuclear Physics and Associated Instrumentation (DAPNIA) in 1991 and led the section until 1999. He became chargé de mission of the CEA and assistant scientific director in Centre national de la recherche scientifique (CNRS), responsible for astroparticle physics and neutrinos. He took over the leadership of DAPNIA in 2002. From 2003 to 2010 he was appointed director of Institut national de physique nucléaire et de physique des particules (IN2P3) in CNRS.