A fast 1-D detector for imaging and time resolved SAXS experiments

A one-dimensional lest detector on the principle of a highly segmented ioni zation chamber with shielding grid (Frisch grid) was developed to evaluate if this kind of detector is suitable for advanced small-angle X-ray scatter ing (SAXS) experiments. At present it consists of 128 pixels which can be r ead out within 0.2 ms with a noise floor of 2000 e-ENC. A quantum efficienc y of 80% for a photon energy of 8 keV was achieved. This leads to DQE value s of 80% for photon fluxes above 1000 photons/pixel and integration time. T he shielding grid is based on the principles of the recently invented MCAT structure and the GEM structure which also allows electron amplification in the gas. In the case of the MCAT structure, an energy resolution of 20% at 5.9 keV was observed. The gas amplification mode enables imaging with this integrating detector on a subphoton noise level with respect to the integr ation time. Preliminary experiments of saturation behavior show that this k ind of detector digests a photon flux density up to 10(12) photons/mm(2) s and operates linearly. A spatial resolution of at least three line pairs/mm was obtained. All these features show that this type of detector is well s uited for time-resolved SAXS experiments as well as high flux imaging appli cations. (C) 1999 Elsevier Science B.V. All rights reserved.