Cooling radiation detectors in well logging apparatus

Claim 1

APPARATUS FOR USE IN MAINTAINING TEMPERATURE STABILITY OF A DETECTOR UNIT USED IN WELL LOGGING OPERATIONS COMPRISING: A LOGGING CASING ADAPTED TO BE SUSPENDED ON A WIRE LINE IN A WELL BORE AND INCLUDING A PLUG COMPRISING A STATIONARY RING MEMBER SCREW THREADED TO ONE END OF SAID CASING AND A ROTATABLE MEMBER BEING PROVIDED WITH INLET AND OUTLET REFRIGERATED PASSAGEWAYS EXTENDING FROM THE EXTERIOR OF SAID ROTATABLE MEMBER TO WITHIN SAID CASING: REMOVABLE CAPS ADAPTED TO SEALINGLY CLOSE OFF SAID PASSAGEWAYS; AN ENCLOSURE ARRANGED WITHIN SAID CASING; TWO CONDUITS ARRANGED IN SAID CASING, ONE EXTENDING FROM ONE OF SAID PASSAGEWAYS AND THE OTHER EXTENDING FROM THE OTHER OF SAID PASSAGEWAYS; SEALING MEANS CLOSING OFF THE SPACE BETWEEN SAID CONDUITS AND SAID PASSAGEWAYS AND THE SPACE BETWEEN SAID ROTATABLE MEMBER AND SAID STATIONARY MEMBER; A PHOTMULTIPLIER DETECTOR UNIT ARRANGED IN SAID ENCLOSURE; A RESERVOIR OF COOLING MEDIUM ARRANGED IN SAID ENCLOSURE; A REFRIGERANT CIRCULATING COIL ARRANGED IN SAID COOLING MEDIUM RESERVOIR AND CONNECTED AT ONE END TO ONE OF SAID CONDUITS AND THE OTHER END THEREOF TO SAID OTHER CONDUIT TO FORM A CONTINUOUS PASSAGEWAY; AN EXPANSION ORIFICE ARRANGED ADJACENT ONE OF SAID CONDUITS; FIRST INSULATION MEANS CLOSING OFF ONE END OF SAID ENCLOSURE; SECOND INSULATION MEANS ARRANGED BETWEEN SAID RESERVOIRVOIR OF COOLING MEDIUM AND SAID DETECTOR UNIT; A HOLLOW ANNULAR HEAT SINK ARRANGED BETWEEN SAID SECOND INSULATION MEANS AND SAID DETECTOR UNIT; AND MEANS EXTENDING THROUGH SAID ENCLOSURE FOR CARRYING ELECTRICAL LEADS TO SAID PHOTOMULTIPLIER TUBE.