A Combined Focusing X-Ray Diffractometer and Nondispersive X-Ray Spectrometer for Lunar and Planetary Analysis
An instrument is described which is intended to perform a dual purpose (elemental—structural) analysis consistent with the environmental conditions implied by lunar or planetary operation. The diffractometer section is based on a modified Seeman—Bohlin focusing principle in which a sharp-line focus target, a powdered sample, and a movable detector slit all lie on the focusing circle. The convolution of the projections on the focal circle, of a narrow receiving slit on the detector, the line focus target, combined with a high dispersion produce higher resolution and intensity than is common with Bragg focusing diffractometers with similar instrumental parameters. The range of d-spacings covered is from 1 to 7 Å (chromium target). The chemical analysis section of the instrument utilizes the fluorescent X-rays produced in the specimen by the primary beam. A proportional counter and pulse-height analyzer accomplish detection and energy discrimination. Resolution is low, but the analysis can distinguish between elements in the range of atomic numbers 11 to 29. Data from a breadboard model is presented. The entire unit, although primarily intended to meet the requirements of space, performs equally well as a routine laboratory analyzer. The horizontal, stationary nature of the specimen holder suggests several specific applications.
KeywordsProportional Counter Quartz Powder Soller Slit Chromium Radiation Chromium Target
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