X-ray or gamma ray systems or devices – Specific application – Diffraction – reflection – or scattering analysis
Patent
1989-03-20
1991-05-14
Westin, Edward P.
X-ray or gamma ray systems or devices
Specific application
Diffraction, reflection, or scattering analysis
378 85, 378147, 378149, 378150, 25037005, 2503901, G21K 106, G01T 300
Patent
active
050162675
DESCRIPTION:
BRIEF SUMMARY
This invention is concerned generally with x-ray and neutron beam instrumentation. In a first aspect, the invention relates to the focusing and collimation of x-rays or neutrons and provides both a method of focusing or collimating x-rays or neutrons and an x-ray or neutron instrument. In a second aspect the invention provides a condensing-collimating monochromator.
BACKGROUND OF THE INVENTION
X-ray mirrors of various types have long been used in some x-ray scattering instruments to provide a means of focusing x-rays and improving flux and intensity, relative to pin-hole optics, by increasing the angular acceptance of the system with respect to the x-ray source. These methods for enhancing intensity have not found widespread application in x-ray scattering instruments because they lack spatial compactness, and flexibility in use, and are awkward to align. In the case of x-ray optical systems, simultaneous high-resolution in wavelength, angular collimation and spatial extent are usually achievable only at the expense of considerable loss in flux and intensity.
An early proposal for an x-ray collimator consisted of two glass plates facing each other at a small angle. This principle was extended in a conical x-ray guide tube proposed by Nozaki and Nakazawa [J. Appl. Cryst. (1986) 19,453].
In a recent paper, Yamaguchi et al [Rev. Sci. Instrum. 58(1), Jan. 1987, 43], there has been proposed a two dimensional imaging x-ray spectrometer utilizing a channel plate or capillary plate as a collimator. It is apparent that Yamaguchi et al are treating the channel plate as a large aperture device acting solely as a set of Soller slits consisting of an array of channels surrounded by opaque walls.
SUMMARY OF THE INVENTION
It is an object of the invention, in its first aspect, to provide for focusing and collimation of x-ray beams as an aid to achieving both optimum angular resolution and optimum intensity in x-ray optical systems. It is believed that the solutions disclosed herein are also useful in the field of neutron scattering and in other instruments.
The invention accordingly provides, in its first aspect, an x-ray or neutron instrument incorporating x-ray or neutron lens means disposed in a path for x-rays or neutrons in the instrument, the lens means comprising multiple elongate open-ended channels arranged across the path to receive and pass segments of an x-ray or neutron beam occupying said path, which channels have side walls reflective to x-rays or neutrons of said beam incident at a grazing angle less than the critical grazing angle for total external reflection of the x-rays or neutrons, whereby to cause substantial focusing or collimation of the thus reflected x-rays or neutrons.
The invention also provides a method of focusing, collimating and/or concentrating an x-ray or neutron beam, comprising directing the beam into the open ends of multiple elongate open-ended channels which have side walls reflective to said x-rays or neutrons incident at a grazing angle less than the critical grazing angle for total external reflection of the x-rays or neutrons, at least a portion of said beam being incident at a grazing angle less than said critical grazing angle so that the beam is at least in part focused or collimated.
The instrument will typically though not necessarily include a source of x-rays and may have one or more slit assemblies, a monochromator, a sample goniometer stage and/or adjustable x-ray detector.
Advantageously, the inclinations of the side walls are uniform in each channel but progressively change from channel to channel with respect to the optical axis of said path whereby to enhance focusing or collimation of said incident beam.
Preferably, the outer side wall of each channel itself varies in inclination along the length of the channel to further enhance said focusing and collimation.
The device is preferable such that these inclinations can be adjusted, at least finely, on installation of the device in the instrument.
As employed herein, the terms "focus" and "collimate" are not str
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Chu Kim-Kwok
Commonwealth Scientific and Industrial Research
Westin Edward P.
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