| Cryosurgery is a clinical technology which destroys the diseased cells and tissues by low temperature injuries through the cryotherapy apparatus without any use of antifreeze agent. It is a new way for effectively curing the tumours. It is an alternative of the traditional ablation and has many advantages: anaesthesia, stopping or decreasing the bleeding, high safety, no side effects, quick recovery and preventing the cancer from diffusing. So far, cryosurgery is considered as an important method to treat the massive tumours that are drug-fast.To date, modern cryosurgical probes have tended to rely on either liquid nitrogen (LN) or the Joule-Thomson expansion of Ar, carbon dioxide or nitrous oxide as the means of cooling. But in many cases the preservation and transport of liquid nitrogen and the high vapor are not so convenient for cryosurgery and in remote regions it is very difficult to get them. Compared with that, the cryosurgery apparatus served by the compression refrigeration system can run continuously with electricity available, but so far the compression refrigeration system of which is so complex and heavy with two or more compressors that it's difficult to move. The autocascade refrigeration system utilizing only one compressor with the working fluid of zeotropic refrigerants can reach low temperature of a large range around-100℃. In this paper an auto-cascade refrigeration system is proposed as the cooling source, and an experimental apparatus is designed and set up. R50, R23 and R600a mixtures chosen as the working mixture of the system. Through optimization study, the lowest temperature on the cryoprobe reaches-110℃and the refrigeration capacity is about 15W when the temperature is-80℃. The results demonstrate that auto-cascade refrigeration technology has good prospects in cryosurgery apparatus.
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