Cryogenic cooler for photoconductive cells

Resolution and sensitivity of photoconducting light sensitive devices vary inversely with temperature. Hence it is desirable to provide cooling means for photoconductive radiation detectors. One type of low temperature photoconductor is fabricated by placing the photomultiplier tube in a double-walled vacuum Dewar flask. In another type, the detector is mounted near a cryogenic projection, or cold finger, emenating from a refrigerator. In this case fabrication is critical, and great care must be exercised when the cryogenic cold finger is inserted in the Dewar well in order to avoid breakage. A different solution herein to the problem provides detector not as prior devices to breakage of the Dewar detector wall