Low Energy Mosaic Electron Sensor

A composite surface barrier type diode for low energy electron detection has been under development. The unit is fabricated on an approximately one inch diameter silicon wafer with a 1/2 inch by 1/2 inch sensitive window on the active side of the unit. The back side of the unit, polished to a mirror finish, has two perpendicular sets of parallel evaporated conductors insulated from each other, used for readout. The location of the incoming particle is determined by the particular channels through which the readout is accomplished. Electrons have been detected on several channels of the device. Currently, work is proceeding to increase the number of working channels and later, the resolution of the device will be increased to accommodate 32 × 32 to 64 × 64 lines per 1/2 inch2 instead of the presently used 10 x 10 lines per 1/2 inch2 . The test equipment consists of an electron gun with an accelerating potential of up to 50 KV, baffles, and a movable sample mount, capable of being cooled, all enclosed in a vacuum envelope. This unit with its readout arrangement, provides a unique scheme capable of position determination of low energy electrons with the minimum number of readout channels and readout complexity. Combining the above mosaic with a UV photocathode and a suitable accelerating potential, it is anticipated that a tube could be constructed capable of sensing extremely low intensity UV flux, down to possibly a few photons per second.