Proportional chamber area detector

Ionization chambers on both sides of the sample are used to determine the absorption (Fig. 22). The scattered photons are recorded by a 200 x 200 mm proportional counter, area detector which is separated from the beamline by a mylar window. 

X-ray diffraction measurements were carried out using KARD-6 diffractometer with a 2D-area detector based on the multi-wire planar proportional chamber (Cu K -radiation, graphite monochromator, 0.1mm width incident beam slit). 

Photon counting devices are required in order to arrive at the necessary accuracy. The noise of the detector has to be lower than 4 orders of magnitude with respect to the signal. Our experience with multiwire proportional chambers may let us believe that this rather stringent condition can be fulfilled. The simultaneous measurement of the whole scattering pattern by position sensitive area detectors is absolutely mandatory... 

Three types of area detectors are presently used in macromolecular crystallographic research (1) multiwire proportional counters, (2) television area detectors, and (3) imaging plates. A multiwire proportional counter consists of an anode between two cathodes these consist of arrays of parallel wires and are arranged perpendicular to each other. The chamber is filled with a gas, consisting partly of xenon which is ionized by the incident X rays, an effect recorded by the detecting device. Television area detectors contain a fluorescent phosphor that produces visible light when hit by an X-ray beam. After intensification, the photons are detected by a television photocathode. 

The telescope ART-P aboard Granat was designed for imaging and spectroscopy in the 2.5-60 keV energy band (Sunyaev et al., 1990). It consists of a position sensitive detector (a multiwire proportional chamber with a window area of 625 cm ) equipped with a URA coded mask and a collimator. 

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