| Numéro |
J. Phys. Colloques
Volume 47, Numéro C8, Décembre 1986
EXAFS and Near Edge Structure IV
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|---|---|---|
| Page(s) | C8-127 - C8-133 | |
| DOI | https://doi.org/10.1051/jphyscol:1986823 | |
J. Phys. Colloques 47 (1986) C8-127-C8-133
DOI: 10.1051/jphyscol:1986823
AN X-RAY MONOCHROMATOR SUITABLE FOR STUDYING BIOLOGICAL SYSTEMS
R.F. PETTIFER1 et C. HERMES21 and Department of Physics, University of Warwick, GB-Coventry, CV4 7AL, Great-Britain
2 EMBL, c/o DESY, Notkestrasse 85, D-2000 Hamburg 52, F.R.G.
Abstract
An X-ray monochromator which is now in routine use at the EMBL Outstation in Hamburg is described. The device uses two separate (220) silicon crystals, the first of which is thermally isolated from the body of the monochromator. The relative angular setting of the two crystals is adjusted by a small piezoelectric stack mounted on a stiff beryllium-copper spring. Rapid settling (120 msecs) minimises the time lost for the monochromator to stabilise and hence X-ray beam damage on the specimen. The relative angular setting of the two crystals is controlled via signals from a photo-emission device and the first ionisation chamber. These signals are combined in a second order control system. By driving the monochromator piezoelectric with a periodic ramping signal, the performance and alignment of the device can be checked. The effects of a temperature difference between the crystals caused by beam heating is also discussed.