| 摘要 |
<p>In the specific embodiments of the invention disclosed, a semiconductor radiation detector located in a logging tool sized for passage through a borehole is maintained at cryogenic temperatures by a cryostat housed in the tool. The cryostat includes a cryogen chamber containing a melting-solid type cryogen. Thermal insulation in the form of radiation heat shields and a vacuum chamber surround the cryogen chamber. The integrity of the vacuum insulation is maintained by an active vacuum pump. The pump may be mounted either externally of the cryostat, such that its operation is independent of temperature conditions within the cryostat, or internally thereof, so as to be cooled by the cryogen. Alternatively, a second cryostat may be provided to cool the pump.</p> |
