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Results for “arbitrary detector aperture”

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DOE OSTI2016

The solid angle (geometry factor) for a spherical surface source and an arbitrary detector aperture

It is proven that the solid angle (or geometry factor, also called the geometrical efficiency) for a spherically symmetric outward-directed surface source with an arbitrary radius and polar angle distribution and an arbitrary detector aperture is equal to the solid angle for an isotropic point source located at the center of the spherical surface source and the same detector aperture.

42 ENGINEERING↗
DOE OSTI2016

The Solid Angle for a Spherical Surface Source and a Detector with an Arbitrary Aperture: An Elegant Proof

It has previously been proven that the solid angle (or geometry factor, also called the geometrical efficiency) for a spherically symmetric outward-directed surface source with an arbitrary radius and polar angle distribution and an arbitrary detector aperture is equal to the solid angle for an isotropic point source located at the center of the spherical surface source and the same detector aperture. The solid angle for a source-detector system is the fraction of source particles that enter the detector aperture and so it is not purely geometric-the angular distribution of the source is a factor. The previous proof relied on an analytic transport-theory (streaming only) calculation of the solid angle Ω for a spherically symmetric surface source and a point detector. In this paper, a new, more elegant proof is given. Since the net current across any portion of a plane that intersects the center of a spherical surface source is zero, the solid angle for a spherical surface source with any polar angle distribution and a uniform azimuthal angle distribution and any detector aperture is equal to the solid angle for an isotropic point source and the same detector. This insight obviates the calculus and trigonometry involved in the previous proof. (author)

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2016

A multi-cone x-ray imaging Bragg crystal spectrometer

This article describes a new x-ray imaging Bragg crystal spectrometer, which—in combination with a streak camera or a gated strip detector—can be used for time-resolved measurements of x-ray line spectra at the National Ignition Facility and other high power laser facilities. The main advantage of this instrument is that it produces perfect images of a point source for each wavelength in a selectable spectral range and that the detector plane can be perpendicular to the crystal surface or inclined by an arbitrary angle with respect to the crystal surface. Furthermore, these unique imaging properties are obtained by bending the x-ray diffracting crystal into a certain shape, which is generated by arranging multiple cones with different aperture angles on a common nodal line.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗