Detection of characteristic x-rays is a fascinating and challenging subject. From its early beginnings with gas proportional counters it has evolved, like many branches of technology, into the use of a variety of semiconductors.

The lithium compensated silicon detector [Si(Li)] has been the predominant measuring tool over the last two decades, in the last five years, increasing numbers of high purity germanium detectors (HPG) have appeared and more recently a plethora of new materials and concepts are seeing a successful introduction. Among these newer materials are compound semiconductors like mercuric iodide, cadmium telluride, cadmium zinc telluride, gallium arsenide, lead iodide, indium phosphide and diamond. Among the new concepts are Bolometers, Transition Edge Detectors, Drift Detectors, PIN Diodes, CCD arrays and PN CCD arrays.