DEMONSTRATION OF NUCLEAR RECOIL DISCRIMINATION USING RECOIL RANGE IN A MIXED CAF2 PLUS LIQUID SCINTILLATOR GEL DETECTOR FOR DARK-MATTER SEARCHES

We present first measurements on a prototype dark matter detector bein g developed to achieve event by event discrimination of nuclear recoil s from electron recoils below 100 keV by utilising the difference in t he recoil ranges of these particles. The detector consists of sub-micr on scintillating grains of CaF2 suspended in Dioxan gel scintillator w ith matched refractive index. We call this form of detector CASPAR (Co cktail of Alkali halide Scintillating PARticles). We present here resu lts of monoenergetic neutron scattering tests on CASPAR and show how s cintillation pulse shape analysis can be used as a powerful means of d istinguishing Ca, F, C and H recoil events from electron recoils. > 90 % discrimination of Ca and F recoils from electrons at 60 keV was obse rved for < 5% loss of signal. (C) 1997 Elsevier Science B.V.