INDRA, A 4-PI CHARGED PRODUCT DETECTION ARRAY AT GANIL

INDRA, a new and innovative highly segmented detector for light charge d particles and fragments is described. It covers geometrically 90% of the 4 pi solid angle and has very low detection thresholds. The detec tor, operated under vacuum, is axially symmetric and segmented in 336 independent cells allowing efficient detection of high multiplicity ev ents. Nucleus identification down to very low energy threshold (approx imate to 1 A MeV) is achieved by using ionization chambers operated wi th low pressure C3F8 gas. Residual energies are measured by a combinat ion of silicon (300 mu m thick) and cesium iodide (5 to 14 cm in lengt h) detectors. Very forward angles are covered by fast counting phoswic h scintillators (NE102/NE115). Charge resolution up to Z = 50 is achie ved on a large energy dynamic range (5000 to 1 for silicon detectors). Isotopic separation is obtained up to Z = 3. The treatment of the sig nals is performed through specifically designed and highly integrated modules, most of which are in the new VXIbus standard. Full remote con trol of parameter settings, including visualization of signals, is thu s allowed. The detector is continuously monitored with a laser source and electronic pulsers and is found stable over several days. Energy c alibration procedures, making use of specific detectors and the abilit y of the GANIL accelerator to deliver secondary beams, have been devel oped. First experiments were performed in the spring of 1993.