Varian Associates

About: Varian Associates is a based out in . It is known for research contribution in the topics: Beam (structure) & Wafer. The organization has 2160 authors who have published 2591 publications receiving 46002 citations.

High voltage power supply for a microwave electron tube

Abstract: A power supply for helix and collector electrodes of a traveling wave tube is driven by an AC power source having a frequency of at least 500 KHz. The helix supply includes plural, stacked voltage double AC to DC modules responsive to the 500 KHz source. The collector supply includes plural AC to DC modules, each having a diode full wave rectifier bridge, connected in stacked relation. Each of the modules includes a transformer with a ferrite, toroidal core dimensioned so that it is not driven into saturation by the 500 KHz source. Each module also includes inexpensive, signal switching diodes having a recovery time of approximately 4 nanoseconds. The ratio of the collector to helix DC voltages is maintained constant by threading a common lead through the apertures of the toroidal cores of the helix and collector modules. A separate common lead threaded through the apertures of the toroidal cores in the collector modules is connected directly to the 500 KHz power source. A feedback circuit responsive to the helix-cathode voltage of the TWT controls the helix power supply voltage precisely.

Iii-v cathodes having a built-in gradient of potential energy for increasing the emission efficiency

Abstract: A gradient of potential energy was established in the active layer of a III-V photocathode for enhancing free electron diffusion toward the emissive surface of the cathode. The energy gradient was provided by decreasing the bandgap energy across the active layer which caused the conduction level to slope downwards from the substrate to the emissive surface through progressive changes in the concentration of the III-V elements forming the active layer. Alternatively, a nonuniform concentration of active layer dopant-heavy on the substrate side and light on the emissive side of the active layer-established a built-in electric field across the active layer. The graded bandgap and/or dopant levels promote free electron drift toward the outer surface of the active layer. Layers of cesium, cesium oxide, or both, were provided over the active layer to lower the work function of the photocathode emissive surface.

Wafer arm handler mechanism

Abstract: A wafer handler arm conveys a wafer from a horizontal orientation to a vertical orientation for wafer processing. The arm includes a wafer holding member which is rigidly attached to a first shaft. The first shaft is rotatable about its longitudinal axis and the first shaft is rotatable about a second axis perpendicular to the first axis.

Radiation therapy apparatus having retractable beam stopper

Abstract: A translation mechanism for linearly moving a beam stopper in radiation therapy apparatus includes first and second arms pivotally mounted to a support and third and fourth arms pivotally mounted to the first and second arms. The third and fourth arms are attached to the beam stopper and can comprise part of the beam stopper. In one embodiment, the third and fourth arms include disc shaped portions stacked in axial alignment with a drive motor attached to one disc portion ahd having a drive shaft axially aligned with and coupled to the other portion whereby relative rotation of the disc portions effects linear translation of the beam stopper.