P Gregers Hansen 1933-2005
Gregers Hansen, who died on 20 July 2005, spent a large part of his scientific life connected to CERN and its ISOLDE programme. Since 1995 he was the John A Hannah distinguished professor of physics at Michigan State University (MSU).
Gregers was born in Svendborg, Denmark, and studied at the Technical University of Denmark before being employed for a decade at the Niels Bohr Institute and Risø National Lab. His work there earned him the degree of doctor of science from the University of Copenhagen in 1965. He then became professor of experimental physics at the University of Aarhus in Denmark in 1966, a chair that he held until 1995. At Aarhus he almost immediately became involved in the experimental programme at the newly constructed ISOLDE facility at CERN, coming to CERN as senior physicist in 1969. He became ISOLDE group leader in 1970 and stayed in this position until the end of 1978. During 1974-1977 he also acted as deputy division leader in CERN's Experimental Physics Division. Gregers' first-hand experience of nuclear structure physics at CERN formed the basis of his account of this period in History of CERN, III.
Gregers had a very broad interest in several fields of physics. The main themes of his work were the nuclear structure and beta decay of exotic nuclei, but he also wrote papers in atomic physics about inner-shell processes and the beta-decay effects of X-rays, and in particle physics and general physics. Besides experiments at CERN, he also conducted experiments at the LISE3 Facility at GANIL and at the ALAIN-LAND setup at GSI. At MSU Gregers worked on physics with radioactive beams and studied in particular one- and two-knockout reactions from exotic projectiles. He wrote several seminal papers about the structure of exotic nuclei.
Gregers' work received widespread recognition. He was a member of the Royal Danish Academy of Sciences and Letters and served in many advisory functions, including CERN's Scientific Policy Committee. He was also president of the Danish Physical Society (1984-1986) and chaired the Proton Synchrotron and Synchrocyclotron Committee at CERN (1981-1985). He was an inspiration for many scientists working with exotic nuclei, and his ability to express penetrating insight in elegant but clear language was admired, as well as feared.
Even though Gregers' life was devoted to science, he possessed an intellect of wide scope and also enjoyed the outdoors. His life ended much too early, but he had the privilege to work with physics every day until he died.