Abstract: An electrode plate arranging jig according to the invention which allows to arrange electrode plates with high precision and facilitates the work of constructing an array of electrode plates, characterized in that a member with a plurality of grooves cut at pitches at which the electrodes are arranged has a structure of two superimposed members (11, 12) deviatable from each other in the direction in which the plurality of grooves are arranged, and has grooves (13, 14) having a width which has enough leeway compared to the thickness of the electrode plates.

Abstract: An X-ray detector, used in an X-ray computerized tomograph systems, and method of making the same. The X-ray detector has a casing filled with gas for detecting X-rays, and flat signal electrode plates and bias electrode plates are disposed alternately at regular intervals within the casing to form a number of spatially partitioned detection chambers. When X-rays enter the detection chambers after being transmitted through an object under examination, the X-ray energy is converted into electric current flowing across the electrodes of the signal electrode plates, whereby the transmitted X-ray can be detected by an output circuit.Improvements are provided to enable the signal electrode plates and the bias electrode plates to be more densely packed into the casing, thereby to obtain higher resolution X-ray computerized tomograms.