RECENT DEVELOPMENTS IN SECONDARY-EMISSION GASEOUS X-RAY-IMAGING DETECTORS

The conversion of X-ray photons in a thin solid film and the detection of the subsequent secondary electrons in a low-pressure avalanche wir e chamber is the basis for a new type of fast, high resolution paralla x-free X-ray imaging detectors. The combination of the high emission y ield of low energy secondary electrons from alkali halides with the pa rticular properties of low-pressure avalanche electron multipliers res ults in a fast detection process, free of space charge effects even at high radiation flux. We summarize recent experimental and theoretical results connected with these secondary emission gaseous detectors whi ch have a broad field of potential applications. Simulations of a real -size ultrafast transition radiation detector based on this principle indicate its outstanding particle identification properties, of prime importance for the very demanding environment of future colliders.