First characterization of the ultra-shielded chamber in the low-noise underground laboratory (LSBB) of Rustrel-Pays d'Apt

In compliance with international agreements on nuclear weapons limitation, the French ground-based nuclear arsenal has been decommissioned in its tota lity. One of its former underground missile control centers, located in Rus trel, 60 km east of Avignon (Provence) has been converted into the "Laborat oire Souterrain a Bas Bruit de Rustrel-Pays d'Apt" (LSBB). The deepest expe rimental hall (500 m of calcite rock overburden) includes a 100 m(2) area o f sturdy flooring suspended by and resting on shock absorbers, entirely enc losed in a 28 in long, 8 m diameter, 1 cm thick steel capsule. This results in an unparalleled combination of shielding against cosmic rays, acoustic, seismic and electromagnetic noise, which can be exploited for rare event s earches using ultra low-temperature and superconducting detectors. The firs t characterization measurements in this unique civilian site are reported. (C) 2000 Elsevier Science B.V. All rights reserved.