FAST area detector diffractometer

Detection is either via photographic film using the oscillation camera (figures 5.35(b) and (c)) on SRS-2 or via the television area detector diffractometer, FAST, of Enraf-Nonius (figures 5.35(d) and (f)). The latter has been especially beneficial for microcrystal studies (see, e.g., Andrews et al (1988)) and radiation sensitive protein crystals (see, e.g., Glover et al (1988) and section 10.2.1.4). 

In a case where the absorption of X-rays is very small and the crystal does not decompose (the decomposition can be monitored by measuring the intensity of so called standard reflection many times during the data collection, however modern area detector equipped diffractometers are so fast that virtually no X-ray radiation decay is normally observed), the data reduction is just a fast computer calculation of the Lp correction to the measured intensities and Fobs arc obtained. Improperly done data reduction or exclusion of the effects of absorption or decay can render the structure solution impossible, so care must be taken in order to do proper data reduction. 

The Biology Department beam line includes a station for protein crystallography (with Supper oscillation camera and FAST TV diffractometer) and a station for small angle diffraction (with a three-circle goniostat and MWPC electronic area detector). The latter station may be available for optimised anomalous dispersion crystallographic studies. The optical design for each consists of a bent pre-mirror, double crystal monochromator and bent post-mirror the mirrors have rhodium coatings (Wise and Schoenborn 1982). 

---