High Repetition Rate Gated Photomultiplier

Abstract

<p>A high repetition rate, high voltage pulse generator was built and was used to gate a photomultiplier for the detection of relatively high levels of radiation.</p> <p>A unique design has been developed which is capable of a much higher repetition rate than any system described in the literature. The pulse risetime is 1.7 ns, and the width is continuously adjustaable from 4 ns. The highest acheivable repetition rate is 100 MHz for a train of six consecutive pulses repeated every 2.5 µs. A continuous train of pulses can be generated for repetition rates below 2.5 MHz. The pulse amplitudes range between 0V and 220V.</p> <p>The gated photomuliplier is a versatile low-noise pulsed detector. One, two or three dynodes can be pulsed with positive or negative pulses, and the cut-off ratio can, within limits, be set to any desirable level. We have acheived ratios ranging between 0 and 2400. The gated photomultiplier can be adjusted to be gated on or off during intense radiation. The latter allows detection of weak radiation occurring before or after the intense radiation.</p> <p>The effect that changes in the potential drop between the dynodes has on the total current gain of the photomultiplier is investigated. Also, investigated are the saturation properties of photomultipliers at high anode currents. These studies explain the behaviour of the gated photomultipliers and indicate how to choose amongst the various photomultiplier parameters.</p> <p>The capability of the gated photomultiplier system in a given application is tested with a dye laser. This is done by carrying out measurements on the amplified spontaneous emission (ASE).</p>