Novel detector systems for time resolved SAXS experiments

Two novel detector concepts will be presented which together satisfy, in pr inciple, most of the requirements of modern diffraction experiments with sy nchrotron radiation. One is based on a gaseous single photon counter with a synchronous read out and interpolating position encoding, combining the adv antages of a pure pixel read out (high local and global rate capability) an d of a projecting read out (small number of channels). In order to demonstr ate the suitability of this detector for X-ray diffraction applications, me asurements at the synchrotron radiation source Elettra (Trieste, Italy) hav e been performed with the prototype (140 x 140 pixels) recording diffractio n patterns from different biological samples (a phospholipid and a protein crystal). These measurements have proven the good spatial resolution, the h igh intensity precision and the high local rate capability. Moreover, the s ingle photon read out was utilized in order to perform highly time-resolved measurements in case of SAXS studies and to apply fine phi-slicing in case of protein crystallography. The other detector system is a highly segmented one-dimensional prototype i onization chamber with an active area of 5 * 30 mm(2). Fast recording seque nces in the order of 200 mu s are ensured by a shielding grid, which is bas ed on the principle of the recently invented MicroCAT structure. The grid e nables new modes of operation such as gas amplification in combination with integration. In this fashion imaging on a sub photon noise level with resp ect to the integration time is possible. A continuous transition from integ rating mode to single photon counting mode results in a huge dynamic range that covers at least 8 orders of magnitude. Preliminary experiments on biol ogical samples will be presented.