Abstract: Air cooled x-ray generating apparatus is provided with a unitary vacuum enclosure having a rotating anode target and a cathode assembly for generating x-rays. The cathode assembly may be placed within the vacuum enclosure through an opening in the top wall thereof, and comprises a disk which completely covers this opening. The unitary vacuum enclosure and the disk form a radiation shield. A plurality of fins are disposed on the exterior side wall of the vacuum enclosure, and a shroud is attached to the fins to provide additional protection of ambient against radiation. The cathode assembly may be placed through a side wall of the vacuum enclosure. The additional protection against excessive radiation in this design is provided by a shielding member placed in proximity to the anode target. The shielding member extends from the side wall of the enclosure and is substantially parallel to the top wall.

Abstract: A gallium-arsenide optical power receiver of the type having a pn junction formed over a substrate and buffer layer has a window layer of a first alloy of aluminum gallium arsenide (Al.sub.x Ga.sub.1-x As) and a conductive layer of a second alloy of aluminum gallium arsenide (Al.sub.1-x Ga.sub.x As). Alternatively, the gallium arsenide optical power receiver has a second window layer of the first alloy of aluminum gallium arsenide disposed on the conductive layer, and a cap layer of gallium arsenide disposed on the second window layer. The sheet resistance of the emitter layer is negated by being in parallel with the low sheet resistance of the conductive layer to minimize the thickness and conductivity of the emitter may therefore be optimized solely for energy conversion efficient.