RELAXATION OF THE CONDUCTIVITY OF CSL-TL AFTER EXCITATION BY SUBNANOSECOND ELECTRON PULSES

The pulsed conductivity is investigated for a CsI-Tl crystal having a Tl+ concentration N = 8 x 10(17) cm(-3) and excited by an electron bea m (0.2 MeV, 50 ps, 10(2)-10(4) A/cm(2)). It is shown that the amplitud e of the conduction current pulse is almost an order of magnitude lowe r than for ''pure'' CsI crystals irradiated under like conditions. The conduction current relaxation time is preserved up to tau = 100 ps in this case. Under the experimental conditions, therefore, the lifetime of electrons in the conduction band is controlled by trapping at Tlcenters. The electron capture cross section at a Tl+ center is determi ned: sigma = 7 x 10(-16) cm(2), which agrees in order of magnitude wit h estimates of the capture cross section for a neutral trapping center . (C) 1998 American Institute of Physics.