Microphony in photomultipliers

Vibration, caused by rotating equipment such as vacuum pumps, and shock, due to sudden impulses, are the main sources of microphonic effects in photomultipliers. Resonant vibrations in the dynode structure in the vicinity of the anode of the multiplier generate an unwanted current analogue at the anode. Mathematical analysis based on a realistic model of the photomultiplier makes predictions on the magnitude of the effect and on the location of individual sources of resonance. Experiments are reported on that support the predictions of the model. Practical guidance is given on how to minimise microphonic effects