Studies of hybrid photomultiplier tubes in magnetic fields up to 5 Tesla

Single and multi-channel hybrid photodiode tubes were operated inside a very high magnetic field of up to 5 Tesla. The effects of focussing and image displacement on crosstalk and gain were examined as a function of angle in the B-field. Brightening of the response in the illuminated pixel, due to improved focussing of the backscatter was observed. Increased path length through the threshold layer of the photodiode decreased the response at large angles.