A helium-cooled, three-circle X-ray diffraction

Abstract

A single-crystal three-circle X-ray diffractometer is described in which the specimen is cooled to about 20°K by the cold-finger technique.

The avoidance of multiple diffraction errors in single-crystal intensity measurements at low temperatures

“…However, if these difficulties could eventually be satisfactorily overcome, there is no question that the fourcircle device would be superior. It is proposed, therefore, to modify the three-circle instrument of Woodley, Hine & Richards (1971) along the lines indicated.…”

“…However, at liquid-helium temperature the mechanical and cryogenic problems of constructing four-circle instruments are great and, from a constructional standpoint, the three-circle diffractometer, with 2" fixed at +90 ° (Arndt & Willis, 1966), is much simpler. One such instrument has been described by Woodley, Hine & Richards (1971). As it stands, the three-circle diffractometer of this design does not allow the azimuthal rotation necessary for the detection of multiple diffraction.…”

Data collection in protein crystallography: experimental methods for reducing background radiation

“…The gas flowing through the cell can be cooled by passage through copper heat-exchange coils immersed in a cooling bath. Several other ways of cooling crystals have been described (Coppens et al, 1974;Marsh & Petsko, 1973;Cucra, Singman, iO00 Lovell & Low, 1970;Streib & Lipscomb, 1962;Woodley, Hine & Richards, 1971). One difference between the gas-flow cell and cooling methods which rely on an open gas flow over the capillary and crystal is that there is essentially no condensation of atmospheric water on the moving parts of the diffractometer when the flow cell is used because the cooled gas does not flow over the instrument.…”

A cryostat for collection of three-dimensional diffractometer data at liquid helium temperatures

“…Instrumentation for neutron diffraction at liquidhelium temperatures has been reported by Heaton, Mueller, Adam & Hitterman (1970), while Streib & Lipscomb (1962) and Woodley, Hine & Richards (1971) have described helium-cooled X-ray diffraction equipment. All these instruments incorporate a large helium reservoir as an integral part of the diffractometer, and the designs are therefore not readily adaptable for use on commercially available three-or fourcircle X-ray diffractometers using the Eulerian geometry.…”