Side-on Photomultiplier Gating System for Thomson Scattering and Laser-Excited Atomic Fluorescence Spectroscopy

A normally-off gating circuit for use with side-on photomultipliers (PMTs) has been developed for use in Thomson scattering and laser-excited atomic fluorescence spectroscopy. Switching of dynodes 1 and 5 provides cutoff ratios greater than 7 × 10 5 and gating times on the order of 6 ns. The gated PMT signal responds linearly up to anode currents of −6.6 mA, a saturation current roughly two orders of magnitude greater than in continuous (dc) operation. The gating circuit has an aperture width variable from 40 ns to 1.3 μs and the ability to operate at triggering rates up to 10 kHz.