CATS, a low pressure multiwire proportionnal chamber for secondary beam tracking at GANIL

A beam detector system, CATS (Chambre A Trajectoires de Saclay), was design ed to provide event-by-event particle tracking in experiments with radioact ive beams at GANIL. It consists of two low pressure multiwire proportionnal chambers with one plane of anode wires placed between two cathode planes ( active area: 70 x 70 mm(2)), respectively segmented into 28 vertical or hor izontal strips (2.54 mm wide). The anode wires deliver a time signal allowi ng a time of flight measurement with an accuracy between 440 ps and 1.2 ns, depending on the energy loss of incident particles in the detector. The ca thode strips are individually read out and the position of incoming particl es is reconstructed using a charge centroid finding algorithm. A spatial re solution of 400 mu m (700 mu m) was achieved during in beam experiment, wit h a counting rate of 1.5 x 10(5) (10(6)) particles per second. (C) 1999 Els evier Science B.V. All rights reserved.