AMORPHOUS-SILICON, SEMICONDUCTOR X-RAY CONVERTER DETECTORS FOR PROTEIN CRYSTALLOGRAPHY

Hydrogenated amorphous silicon (a-Si:H) is a semiconductor material wh ich call be inexpensively deposited to create a large array detector o r readout structure. Combining it with a suitable semiconductor X-ray sensitive converter would produce a large, sensitive detector for X-ra ys with energies of 6-20 keV such as used in measurements of diffracti on patterns for protein crystallography. In these experiments, the dif fraction patterns created when X-rays strike crystallized protein samp les are used to infer the physical structure of the molecules. The req uirements for the detector include the ability to record signal peaks to high diffraction order to obtain accurate mapping of the electron d ensity of the protein molecule, plus rapid sampling of the diffraction pattern to minimize radiation dose to the exposed crystal, while main taining high signal-to-noise ratios. In this paper we summarize our re sults to date measuring and modeling the suitability of various semico nductor thin films for direct X-ray detection, and of the noise and re adout properties of an amorphous silicon matrix array, We provide samp le diffraction patterns obtained from a protein crystal taken at the A rgonne Advanced Photon Source X-ray synchrotron using a phosphor coate d a-Si: H array.