Varian Associates

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

Production of ion beams by chemically enhanced sputtering of solids

Abstract: A method for producing an ion beam for ion implantation by chemically enhanced bombardment of solids. The method is carried out in a reaction chamber having an anode and cathode and a cathode liner rich in a selected element, namely boron, arsenic, phosphorus or antimony. A non-poisonous feed gas is introduced into the reaction chamber and energy is supplied to the feed gas to generate a plasma in the reaction chamber. The constituents of the plasma react chemically with the selected element in the cathode liner and an electrical potential is established between the anode and the cathode so that ions in the plasma bombard the cathode liner. The chemical reaction and bombardment together generate an ion species in the plasma containing the selected element. A beam of ions containing the selected species is then extracted from the plasma.

Heterojunction confinement field effect transistor

Abstract: An improved field-effect transistor is provided by forming the conducting channel boundary opposite the gate electrode as a heterojunction. For example a GaAs conducting channel may be bounded by an AlGaAs layer. The conduction electrons can penetrate the boundary very little and are constrained to the channel layer having good transport properties. The output conductance is reduced and the transconductance increased.

Tomographic scanning apparatus having detector signal digitizing means mounted to rotate with detectors

Abstract: Scanning apparatus is disclosed for use in computerized axial tomography systems. The apparatus includes an assembly rotatable about an axis extending along a central opening defined therein, and means for positioning the body portion to be examined within the central opening so that the axis of assembly rotation is perpendicular to a plane passing through the bodily structures to be examined. A source of penetrating radiation is mounted on the assembly toward one side thereof and provides radiation in the form of a fan beam. Detector means for the radiation are positioned on the assembly opposite the source, enabling detection of radiation which traverses laterally and is not absorbed in the thin body section in which the aforementioned plane resides. Means are provided for rotating the assembly so that the fan beam impinges upon said body portion at a plurality of incident directions. Signal processing and conditioning means mounted on the assembly and movable therewith, receive the output signals from the detector means and amplify and convert same to digital form. Slip ring interconnection means rotatable with the assembly, receive the outputs from the signal processors and conditioners and interfeed these signals to a computerized image reconstruction station. Slip rings rotatable with the assembly also provide interconnection enabling power and control inputs to the radiation source and to other portions of the apparatus. The assembly is continuously rotatable through successive 360 degree rotations and the examination sequence may be initiated at any point in the rotation of the assembly. The detector comprises an array of elements and means are provided for adjusting the gains of each channel associated with the individual detector elements as an incident of the examination process, thereby enabling compensation for drift in the channels.

Single-pump multiple stroke proportioning for gradient elution liquid chromatography

Abstract: In a high-performance, high-pressure liquid chromatography system, gradient elution of solvent components from a plurality of component reservoirs can be accomplished according to a programmed temporally variable ratio by a single reciprocating pump. The pumping cycle comprises a plurality of fill strokes with intervening pumping strokes. During one of the fill strokes of the cycle, a proportioned mixture of solvent components is admitted to the pump chamber from the respective reservoirs by means of proportioning valves. During each of the other fill strokes of the cycle, only a single solvent component is admitted to the pump chamber. Consequently, a relatively low concentration of a particular component can be delivered by the pump with precision over a complete pumping cycle, although a comparatively higher and therefore more accurately measurable concentration of that component is admitted to the pump chamber during any given fill stroke. The opening and closing of the proportioning valves during the component proportioning fill stroke is sequenced to minimize deviations of the relative concentrations from the programmed concentration ratio. Proper sequencing of the proportioning valves reduces inaccuracies that would otherwise tend to occur, especially at the upper and lower concentration limits, due to effects related to the compressibility of residual solvent remaining in the pump chamber at the end of each pumping stroke.