Gifford-McMahon refrigerator

Fig. 5.18. A single-stage version of the Gifford-McMahon refrigerator [74].

The cryogenic adsorption system was specially developed to measure adsorption isotherms of H2 and D2. This system is equipped with a closed helium cycle two-stage Gifford McMahon refrigerator to operate under cryogenic conditions. The adsorption temperature can be kept constant within 0.03 K at 20 K. Adsorption isotherms are obtained by gas adsorption manometry. This method is based on the measurement of the gas pressure in a calibrated, constant volume, at a known temperature. The dead space volume was calculated from a helium calibration measurement at the temperature of interest. Thermal transpiration effect was calibrated according to the work by Takaishi and Sensui [41]. 

Unfortunately, there were no solutions available on the market to characterise charcoal materials in the required temperature range. As a consequence, an own concept was developed, which evolved in the new experimental facility COOLSORP (see [2, 4] for technical details). COOLSORP combines a standard apparatus for sorbent characterisation at 77 K and a two-stage Gifford McMahon refrigerator (the cold head being in direct contact with the sample cell) so as to extend the operational range down to cryogenic temperatures. 

Solvay and A. D. Little (Gifford-McMahon) Refrigeration Systems... 

We will then describe the Collins helium liquefier and coolers which use turboexpanders (Linde He liquefier). At the end of the chapter, we will describe cooling cycles which use regenerators and other cycles used in cryocoolers (Philips-Stirling, Gifford-McMahon (GM), Klimenko cycles and pulse tube refrigerators (PTRs)). 

The series-manufactured refrigerator cryopumps from LEYBOLD use a two-stage cold head operating according to the Gifford-McMahon principle (see Fig. 2.67). In two series connected stages the temperature of the helium is reduced to about 30 K in the first stage and further to about 10 K in the... 

Fig. 2.66 Refrigerating phases using a singie-stage coid head operating according to the Gifford-McMahon process...

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