Nuclear Instruments and Methods 188 ( 1981 ) 293- 303 293 North-Holland Publishing Company A TWO-DIMENSIONAL POSITION SENSITIVE AT-E COUNTER FOR ENERGETIC LIGHT CHARGED PARTICLES W.W. W1LCKE, J.R. BIRKELUND, JP. KOSKY, H.J. WOLLERSHEIM, A.D. HOOVER, J.R. HUIZENGA, W.U. SCHRODER, L.E. TUBBS Nuclear Structure Research Laboratory and Departments of Physics and Chemistry, University of Rochester, Rochester, New York 14627, U.S.A. and D. HILSCHER Hahn.Meitner Institut, Berlin, West Germany Received 24 March 1981 A large area position sensitive &E-E detector for energetic light charged particles is described. A single wire gas proportional counter is used as the AE detector, with stop detectors consisting of three 19 mm thick NE 102 scintillators coupled to RCA 8053 photomultipliers. The total active area of the &E-E detector is 43 cm2. Two dimensional position readout is obtained from the proportional counter by a combination of charge division and electron drift time measurements. The detector is suitable for c~-particles with energies between 6.5 and 180 MeV. Position resolution is 1 mm in both dimensions, zXEresolution is 10% and the energy resolution of the scintillators is 3g. The detector is compact enough to fit in a 30" scattering chamber, where solid angles >~200 msr may be attained. An application of this detector in studies of charged particle emission in a heavy ion induced reaction is discussed. 1. Introduction Experiments with heavy ion beams at energies in excess of 10 MeV/amu as well as experiments study- ing the emission of light charged particles in deep inelastic collisions require detectors which are charac- terized by the following features: 1) Tile detector should be capable of stopping pro- tons and c~-particles with ranges of several cm in solid matter. 2) The detector solid angle should be large enough to facilitate coincidence experiments which are man- datory for an understanding of complex multi-parti- cle reaction mechanisms. To retain a good angular resolution the counter should be position sensitive in and out of plane. 3) Energy resolution of the order of 5% is ade- quate to study reactions leading to continuous charged particle energy spectra. 4) The detector should be compact enough for use in 30" diameter scattering chambers which are avail- able in many accelerator laboratories. While silicon surface barrier detectors have excel- 0029-554X/81/0000-0000/$02.50 © 1981 North-Holland lent energy resolution and are compact, they are usually not available with volumes large enough to fulfill the first two requirements. Moreover, they are quite vulnerable to radiation damage, which is a serious disadvantage for large, very expensive detec- tors. Gas-filled detectors can be designed with large apertures if the gas pressure stressing the windows is low, but it is not possible to build such detectors compactly if highly penetrating particles are to be stopped. A detector design which fullfills all of the above requirements combines a scintillation counter as a stop detector with a gas-filled counter for particle identification purposes. This paper reports the design and performance of such a detector. A proportional counter, position sensitive in two dimensions, is com- bined with three plastic scintillators which are each coupled to a photomultiplier tube of 5 cm diameter. The detector stops c~-particles with energies up to 180 MeV, has an energy resolution of up to 3% and can be operated in a scattering chamber of 30" diam- eter, in which case it has a minimum solid angle of 200 msr. In section 2 the mechanical design of the detector