October 22, 2006 11:44 WSPC - Proceedings Trim Size: 9in x 6in lebois˙EXON2006 1 Production of mass-separated fission fragment beams at ALTO M. Lebois, M. Cheikh Mhamed, J M. Curaudeau, M. Ducourtieux, S. Essabaa, S. Franchoo, S. Gal` es, D. Guillemaud-Mueller, F. Ibrahim, C. Lau, J. Lesrel, A. Mueller, M. Raynaud, B. Roussi` ere, A. Said, D. Verney, C.Vogel and the ALTO collaboration. Institut de Physique Nucl´ eaire d’Orsay, IN2P3-CNRS / Univ. Paris Sud - XI Orsay, 91406, FRANCE * E-mail: lebois@ipno.in2p3.fr http://ipnweb.in2p3.fr Yields of neutron-rich isotopes produced by the photofission were measured at the ISOL ALTO facility. The identification was achieved by a combined measurement of β and γ-rays. Production rates for Xe, Kr, Sn, In and I isotopes are presented here. In parallel, empirical estimations for the yields based on the PARRNe experimental data and the results provided by a very recent FLUKA simulation are presented. Keywords : Photofission, Production yields, Radioactive beams, Uranium car- bide target, ISOL Ion source 1. Introduction The study of exotic nuclei is one of the main fields explored by nuclear physicists and the availability of new radioactive beams is essential to com- plete this task. The SPIRAL2 project will allow to study medium mass nuclei with very large neutron excess produced by fission of 238 U using the ISOL (Isotope Separation On-Line) technique. For many years the In- stitute of Nuclear Physics at Orsay has been contributing to this project, and in particular with the use of the Orsay Tandem as a deuteron driver to determine experimentally the optimal conditions for the production of fission fragment beams in ISOL conditions with the PARRNe (Production d’Atomes Radioactifs Riches en Neutrons) program. Recently, a primary beam of electrons has been used for the first time at IPN Orsay in replacement of the deuteron beam to produce mass sep- arated fission fragment beams: this marks the effective birth of the ALTO (Acc´ el´ erateur lin´ eaire aupr` es du Tandem d’Orsay) facility. With an electron beam of 10 µA at 50 MeV it was expected to improve the effective yields by