Abstract
Electrical signals induced by pulses of a focused IR (λ = 1064 nm) laser beam in strip detectors were measured using a wide bandwidth current amplifier. The laser beam was focused to a spot with a diameter of about 8 μm and directed to the detector surface. The detector was mounted on a high precision moving stage allowing measurements of signals induced by a laser beam directed to different locations on the detector surface. Measurements were performed with miniature micro-strip detectors made by implanting n+ type readout strips on p-type silicon bulk (n+-p). Special type of detectors, with implants not fully covered by metal, allowed TCT measurements with a laser beam directed on the implant. The detectors were irradiated with reactor neutrons up to fluences of 5·1015 neq/cm2. The signals were measured at reverse bias voltages up to 1000 V. The measurements were repeated after several annealing steps at 60°C. Strong dependence of charge collection on distance of laser beam from the implant was observed in heavily irradiated detectors indicating that charge multiplication is increased at implant edges.