Patent ID: 7197884

Claim:
A method for producing a target temperature for storage of samples in the interior of a sealed container, which target temperature is in the range of about −140° C. to about −269° C., said method comprising the steps of: a) placing the samples to be in respective bar-coded receptacles which are positioned on a stage in the sealed container; b) compressing a gaseous cryogen; c) circulating the compressed cryogen through a closed circuit to at least one sealed heat exchanger which is disposed in the interior of the sealed container so as to lower the temperature of one or more samples disposed in the sealed container; d) expanding the compressed cryogen in an expansion space in the heat exchanger; e) recompressing the expanded cryogen; f) recirculating the recompressed cryogen through the closed circuit to the closed heat exchanger; and g) repeating steps d) through f) until the target temperature in the sealed container is produced.