Abstract:
An image sensing device includes a wafer of semiconductor material having a first surface and a second surface. The first surface has a central portion comprising a membrane, which is surrounded by a rim. The membrane is of lesser thickness than the rim. An improved support assembly for the device comprises a lower support member in contact with the rim portion of the second surface of the wafer near the periphery thereof, and an upper tensioning member having a target contact portion which forcibly abuts the rim portion of the first surface of the wafer adjacent to the membrane and urges the wafer against the lower support member thereby tensioning the membrane. Centering brackets center and secure the lower support member and the upper tensioning member within the device.
Abstract:
An improved photomultiplier tube of the type having a longitudinally-extending tube axis includes an evacuated envelope having a generally cylindrical wall member. The wall member is closed at one end by a face-plate and at the other end by a stem, heat sealed to the wall member. At least one source of alkali vapor is within the envelope. A photoemissive cathode is formed on the faceplate. A dynode cage assembly is spaced from the cathode in proximity to the stem. A plurality of stem leads extend through the stem for energizing the cathode, the dynode cage assembly and the source of alkali vapor. A heat shield is disposed transversely across the tube axis between the dynode cage assembly and the stem. The heat shield isolates the dynode cage assembly from the deleterious effect of the heat generated during the sealing of the stem to the wall member. The heat shield comprises a substantially inert, insulative material. The source of alkali vapor is mounted on the heat shield facing the dynode cage assembly. The heat shield also shields the vapor source from the heat generated during the sealing of the stem to the wall member.
Abstract:
A method is provided for making a lithium-sodium-antimony photocathode including the step of forming a base layer including antimony on a substrate. Sodium is then deposited onto the base layer at an elevated temperature to a first peak value of responsivity, thereby forming a sodium-antimony surface. Next, at room temperature, lithium is deposited onto the substrate containing the sodium-antimony surface until the lithium-sodium-antimony photocathode develops a hazy brown color. The photocathode is sensitized by heating the substrate to an elevated temperature until a second peak value of responsivity, greater than the first peak value, is obtained. Antimony, sodium and lithium are then alternately deposited on the photocathode in order to stabilize the second responsivity peak.
Abstract:
A photoelectric tube, preferably a photomultiplier tube comprises a photoemissive cathode deposited on the inner faceplate of the tube envelope and a dynode assembly mounted within the envelope. The tube includes a generator containing an alkali metal source for deposition of alkali metal onto the cathode surface. The generator has means for directing the alkali metal vapors substantially toward the cathode surface and for preventing the alkali metal vapors from substantially depositing on the dynode assembly.