First results of the 25 pixel HPD

Abstract Speed properties, signal shape, response uniformity and magnetic field behavior of a 25 pixel, proximity focused HPD have been measured in different experimental conditions. Using 30 ps wide laser pulses, rise times of less than 1 ns and 10 ns long trapezoidal pulse shapes (at 200 V bias) have been observed. The 25 pixel HPD was measured to have good integrated charge response uniformity without charge losses or gain variations across pixel boundaries, although a spatial scan showed some significant pulse height and pulse shape variations near the borders between pixels. These pulse shape variations were traced to discontinuities of the electric field inside the chip. The signal shape uniformity is expected to be restored by reducing the pixel to pixel gaps. Well separated single photoelectron peaks have been registered. Magnetic field tests yielded results compatible with what already published.