An X-ray scanner based on an "edge on" illuminated capillary plate combined with a gas amplification structure

Abstract

We have developed and successfully tested a prototype of a new type of high position resolution X-ray scanner. It contains a thin wall lead glass capillary plate converter of X-rays combined with a microgap parallel-plate avalanche chamber operating in various gas mixtures at 1 atm. The operation of these converters was studied in a wide range of X-ray energies (from 6 to 60 keV) at incident angles varying from 0-90/spl deg/. The detection efficiency, depending on the geometry, photon's energy, incident angle and the mode of operation, was between 5-30% in a single step mode and up to 50% in a multi-layered combination. Depending on the capillary's geometry, the position resolution achieved was between 50-250 /spl mu/m in digital form and was practically independent of the photon's energy or gas mixture. The usual lead glass capillary plates operated without noticeable charging up effects at counting rates of 50 Hz/mm/sup 2/, and hydrogen treated capillaries up to 10/sup 5/ Hz/mm/sup 2/. Finally, a prototype of the X-ray scanner based on an edge-on illumination capillary plate was built and tested. The developed detector open new possibilities for medical imaging, for example in mammography, portal imaging, radiography (including security' devices), crystallography and many other applications.