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Mounting a 10 K cooling device without rotating seals on a four‐circle diffractometer
Author(s) -
Henriksen K.,
Larsen F. K.,
Rasmussen S. E.
Publication year - 1986
Publication title -
journal of applied crystallography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.429
H-Index - 162
ISSN - 1600-5767
DOI - 10.1107/s0021889886089173
Subject(s) - cryocooler , cryostat , goniometer , refrigerator car , thermometer , liquid helium , materials science , liquid nitrogen , optics , cryogenics , head (geology) , triple point , refrigeration , mechanical engineering , helium , physics , engineering , thermodynamics , atomic physics , superconductivity , quantum mechanics , geomorphology , geology
Instrumentation has been developed for collection of three‐dimensional X‐ray and neutron diffraction data at temperatures below the boiling point of liquid nitrogen. A closed‐cycle two‐stage refrigerator has been mounted on the ϕ shaft of a four‐circle goniometer. The sample crystal is attached to the nominal 10 K station. The refrigerator mount functions as a goniometer head without arcs. The x−y−z centering device has a range of ± 5 mm for the z direction along the ϕ axis and ± 2 mm along x and y . Dovetails and eccentrics with narrow tolerances allow a precise firmly lockable centering of the crystal. The whole refrigerator unit undergoes all the normal ϕ , χ and ω movements during data collection without any rotating vacuum seals. These are usually integral vulnerable parts of existing liquid‐helium‐temperature cryocoolers. When refrigeration is not required, the cryo‐unit can be dismounted in a few minutes and replaced by a device for mounting an ordinary goniometer head for room‐temperature data collection. Thus, the system is simple, robust and easy to operate, both at room temperature and at cryogenic temperatures. Furthermore, the use of a closed‐cycle refrigerator makes the system more economical than comparable cryocooler systems based on flow cryostats.