Development of multi-frame detector for ultra-fast radiography with 800 MeV protons

Two prototype small-area pixilated detectors, capable of recording signals produced by 800 MeV proton beam micropulses, with a repetition rate of 358 ns, were constructed. The first detector system was built around a two-dimensional photodiode array. The array was illuminated by light emitted by a monolithic 1.7 mm thick LSO scintillator and imaged by a simple mirror and lens optical system. Tests were carried out with an array of 8×8 pixels 1 mm2 in area. The other detector was a hydrogen ion-chamber operated at 1 to 2.5 atm. The fast positive-ion drift velocity in hydrogen helps to minimize the space charge build up. However, for pulses spaced closely in time, less than 1 μs, there appear to be a substantial accumulation of positive space charge. The electronic readout chain, for each of the 64 channels, consisted of an externally clocked fast gated integrator and an amplifier coupled to an on-board ADC and a FIFO. The detectors were tested with a beam of up to 6×106 protons per mm2 in 30 to 120 ns-wide microbursts