LONG-TERM INVESTIGATION ON SELF-IRRADIATION AND SENSITIVITY TO COSMIC-RAYS OF TL DETECTOR TYPES TLD-200, TLD-700, MCP-N AND NEW PHOSPHATE-GLASS DOSIMETERS

The cosmic component of background gamma radiation, the intrinsic back ground (or 'self-dose') and fading of TLD-600, TLD-700 and TLD-200 (al l produced by Harshaw), MCP-N (LiF:Mg,Cu,P produced by INP Krakow) and phosphate glass dosemeters SC-1 (Toshiba Glass) were measured over a period of 557 days at the Asse salt-mine 775 m below ground level, in a steel shielding at the FZK (Karlsruhe Research Centre) laboratory an d in a buoy off-shore of an artificial lake. Assuming a reference cosm ic dose rate of 37 nGy.h(-1) over the lake, the relative response to c osmic rays was estimated at 0.76 for the LiF:Mg, Ti and CaF2:Dy detect ors and 0.86 and 0.81 for the phosphate glass and LiF:Mg,Cu,P detector s, respectively. Fading of detectors of all types did not exceed 5% pe r annum including long-term storage at 33 degrees C in the salt mine.