The status of gas-filled detector developments at a third generation synchrotron source (ESRF)

Noble gas is a homogenous, defect free medium. This unique property allows us to drift, multiply and collect electrons in a gas practically without lo sses over short time scales. The device based on these principles-the gas-f illed proportional counter-has served as an X-ray detector for more than 90 years. Different processes such as space charge effect, aging, etc. limit the perf ormance of the detector. These problems are even more severe at the third g eneration synchrotron sources owing to their high brilliance. Delay line ba sed detectors have been constructed at the ESRF. It turned out that in most cases the speed of this data acquisition system is the main limiting facto r. Recently, a very promising solution has evolved which can re-adapt the g as-filled detector to the challenges of the third generation sources. This development is based on micro-pattern detector, especially the Gas Electron Multiplier (GEM). The GEM allows higher local count rates by several order s of magnitude. (C) 2001 Elsevier Science B.V. All rights reserved.