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.

A Comparison of Noise and Dose in Conventional and Energy Selective Computed Tomography

Abstract: We compare the noise properties of conventional and energy selective X-ray computed tomography. The images produced by the systems are not directly comparable so we discuss their relationship and show that the conventional image is a subset of the energy selective data. We describe how to form a conventional image from the energy selective images and demonstrate that, if this is done at the optimal display energy, the resulting conventional image will have the same noise as that produced by a conventional system with the same dose. But the energy selective system also extracts all the energy dependent information so it produces more information for the same dose than a conventional system.

Determination of the resonant frequencies in a complex cavity using the scattering matrix formulation

Abstract: A method for computing the resonant frequency in a complex cavity consisting of a series of waveguide sections is derived. The analysis is restricted to transitions in which one waveguide is wholly contained in the other. An eigenvalue problem is formed by cascading the scattering matrix from a given section outwards to the ends of the complex cavity, with appropriate boundary conditions at the ends. The eigenvalue equation is solved numerically by searching for a complex frequency, the cavity Q being determined by half of the ratio of the real to the imaginary part of the frequency. The technique is easily implemented numerically and shows good agreement with experiment. This method is suitable for modeling both abrupt changes in radius and smoothly varying tapers. >

Alkali metal leak detection method and apparatus

Abstract: A method and apparatus for detecting a leak of an alkali metal in liquid form in a structure such as the heat transfer system of a nuclear reactor. When alkali metal leaks from its containment structure and thereupon comes into contact with a compound containing hydrogen which can be displaced by the alkali metal, a chemical reaction occurs by which hydrogen gas is generated. The hydrogen gas so generated will diffuse very rapidly throughout the region proximate to the sodium leak. The hydrogen compound can be present in a variety of physical forms. The compound barium hydroxide is especially suitable as a source for the generation of hydrogen gas. Water vapor in air or in an inert gas also provides a suitable hydrogen source. A sensor located within the region of the alkali metal leak will sense the presence of hydrogen gas and will thereupon activate an alarm or recording device. The efficiency of the leak detection system can be evaluated and periodically tested by simply introducing a measured quantity of hydrogen gas into the region proximate to the alkali containment structure. This obviates the necessity of effecting a controlled alkali metal leak in order to test the leak detection system.