| Protein microcrystallography is an active field of study in the synchrotron community, due to the fact that many proteins of scientific interest produce only small, weakly-diffracting crystals. New detectors must be developed to improve data quality and facilitate new experimental protocols, such as low-flux single-shot diffraction from microcrystals. The pioneering work in microcrystallography has been done primarily with phosphor-coupled CCDs and, more recently, with photon-counting pixel array detectors. However, both technologies have drawbacks that inhibit further development of the field. Phosphor-coupled CCDs have a large point spread function and relatively low signal-to-noise ratio (on the order of 0.5-1) for single x-ray photons. Photon-counting pixel array detectors have superior noise performance, but suffer from large pixel size and detector systematics which deserve consideration.;To fill the need for a detector with small pixels and low x-ray equivalent noise, a deep-depletion CCD has been developed with 24 microm x 24 microm pixels and a point spread < 50 microm FWHM. This device is based on the direct detection of x-rays in silicon, which yields a large number of charge carriers per stopped x-ray, such that the signal from a single x-ray photon far outweighs the detector read noise. The design of this device will be described, along with characterization and initial protein crystallographic measurements. |
