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.

History of microwave electron linear accelerators for radiotherapy

Abstract: Some of the far reaching contributions of Henry S. Kaplan are described which helped launch the development, improvement, and widespread use of microwave electron linear accelerators in radiotherapy. These are presented in historical relationship to the fundamental inventions and developments upon which modern medical accelerator technology is based.

Substrate Bombardment During RF Sputtering

Abstract: It is shown, that for the conditions relevant to the “peak” type of rf sputtering arrangement, and in fact most rf sputtering devices, that ions are essentially unaware of the existence of the rf fields and respond only to the dc fields generated. This enables the sputtering parameters to be viewed in a simple, physical way and calculations based on this approach are shown to be fairly exact. A deduction from the theory is that the majority of the secondary electrons released by ion bombardment of the target plates strike the substrate table with considerable energy. A special gridded probe in the substrate table enabled the simple theory to be verified quantitatively and also verified the existence of the high-energy electrons. By controlling substrate bombardment during sputtering with another grid arrangement, the effects of this high-energy electron bombardment on film adherence and appearance was demonstrated.

Submicron GaAs microwave FET's with low parasitic gate and source resistances

Abstract: The substantial reduction in gate metallization resistance and improvement in performance of submicron-gate GaAs FET's has been achieved by employing a mushroom profile defined by electron-beam exposure. Using MBE growth of buffer, channel, and n+ contact layers, minimum noise figures of 1.0-1.1 dB have been demonstrated at 8 GHz, with associated gains of 13-14 dB.

R.f. transistor package having an isolated common lead

Abstract: In a radio frequency transistor package, a layer of metallization is deposited on an electrically insulative thermally conductive ceramic substrate member serving as a heat sink An insular region of the metallization serves as a pad for receiving a transistor die with the collector region of the transistor bonded to the insular region of metallization The region of the metallization surrounding the pad comprises a ground plane An apertured ceramic insulative spacer is bonded over the ground plane metallization with the aperture in registration over the transistor Input, output and a pair of common lead metal strips are bonded to the upper surface of the spacer in generally coplanar configuration The two common leads extend across the spacer adjacent opposite sides of the aperture in generally tangential relation thereto The input and output leads are disposed in between the common leads and are interrupted by the central aperture in the spacer The common leads are electrically interconnected to the ground plane metallization layer via conductive means extending through the aperture in the spacer The input lead is connected to one of the base or emitter regions of the transistor die via wire bonding leads extending through the aperture in the spacer The other base or emitter region of the transistor die is connected via parallel wire bonding leads to the surrounding ground plane metallization The output lead is connected via a set of parallel wire bond leads through the central aperture to the transistor pad

Comparative Electron-Nuclear Double Resonance Study of Two Flavoproteins

Abstract: The proton electron-nuclear double resonance (ENDOR) of flavin radicals in NADPH dehydrogenase and a flavoprotein from Azotobacter vinelandii have been studied at −160 and −120°. By combination of the apoprotein of NADPH dehydrogenase with [8-Me-2H3]FMN, it was demonstrated that the CH3(8) group of the coenzyme gives an ENDOR signal. The ENDOR signals from CH3(8) of the two proteins showed different hyperfine couplings which are consistent with the assignments of a radical anion, or a neutral radical enolized at 0(4), in NADPH dehydrogenase and a neutral radical protonated at N(5) in the Azotobacter flavoprotein. Analysis of the matrix-ENDOR signals in H2O and 2H2O yields information concerning the exchangeability of protons both in the constituent water and on the apoprotein in the vicinity of the radical.