LOW-TEMPERATURE AND HIGH-TEMPERATURE RESPONSE OF LITHIUM-FLUORIDE DOSIMETERS TO X-RAYS

The energy response of lithium fluoride (LiF) thermoluminescent dosemeters has been determined at two temperatures. Glow peaks 3, 4, and 5 are measured at 240 degrees C and peaks 6 and 7 at 300 degrees C. In studying the response to X-radiation it was observed that the response of LiF chips to photons below 150 keV is greater, relative to cobalt-60, than that expected from the energy absorbed in the material. There is an enhancement of 10% at 240 degrees C and of about 100% at 300 degrees C for the same energy absorption. This effect is particularly important where precise measurement of X-ray dose is required and corrections of from 10 to 15% above the correction from rads in LiF to rads in water will be necessary depending upon the maximum read-out temperature. Qualitatively the enhancement may be explained in terms of the higher mean rate of linear energy transfer at low photon energies relative to cobalt-60 gamma rays.