A cryogenic system designed around a Joule-Thomson liquifier capable of maintaing hydrogen temperatures for long periods of time and a simple cryostat suitable for simultaneous infrared and ultraviolet matrix isolation spectroscopy are described. Design features of the gas-control apparatus and construction details for the cryostat per se are provided. The system described provides variable temperature control from 16°K to room temperature. Whereas the apparatus was designed specifically for spectroscropic studies, it may be readily adapted for applications in other areas.
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References
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GeistJ. M. and LashmetP. K., Advances in Cryogenic Engineering, TimmerhausJ. D., Ed. (Plenum Press, Inc., New York, 1960) 5, 324; GeistJ. M. and LashmetP. K., Advances in Cryogenic Engineering, TimmerhausJ. D., Ed. (Plenum Press, Inc., New York, 19(1) 6, 73; WhiteD. and MannD. E., Rev. Sci. Instr.34, 1370 (1963).
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Advanced Products Department, Air Products and Chemicals, Inc., Allentown, Pennsylvania.
4.
Plans available from the author on request.
5.
Parker-Hannifin Corp., Cleveland, Ohio, reports the following working pressures for copper tubing including a safety factor of 4: 1/8 in. (032-in. wall) ⩽3000 psi; 1/4 in. (.049-in. wall) ⩽3000 psi; 3/8 in. (.035-in. wall) ⩽1500 psi.
6.
Available from Advance Products Department, Air Products and Chemicals, Inc., Allentown, Pennsylvania.
AhlersG. and MacreJ. F., Rev. Sci. Instr.37, 962 (1966).
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Johnson-Williams Inc., Mountain View, California; model SE, combustible gas alarm.
10.
The interval may be longer for gas which is cleaner than commercial grade (99.8%–99.9%).
11.
Care must be taken not to overheat the inside of the dewar. To ensure that particulate matter is kept away from the critical orifice, the helium used in backpurging the refrigeration unit should be passed through a 7-μ filter.
