The thermoluminescence of BaF2:Dy

Barium fluoride doped with dysprosium has been found to exhibit intense thermoluminescence. The glow curve has dominant peaks at 1200C and 2500C. The two peaks are isolated sufficiently well that they may be instrumented separately using temperature discriminators. The 1200C peak is very bright and, since incandescence is trivial, can be used to measure exposures of a few microroentgen of energetic gamma rays. Where stability over long periods or at higher temperatures is required, the high temperature peak may be used. A low temperature trap exists at about 600C. The trap is effectively emptied in five minutes at room temperature. The 1200C trap is useful without correction for times after exposure up to three hours and can be corrected for fade for times up to 200 hours. The principle application of BaF2:Dy is in x-ray detection. It exhibits an overresponse of approximately 100 at 70 kev, providing high discrimination against energetic gamma rays and cosmic ray background. Supralinearity is observed in the 1200C trap for exposures of 10 R and above and in the 2500C trap for exposures of 1R and above. The material is useful with linearity correction up to 104R. Supralinearity can be annealed for re-use of the crystal by baking at 4000C for one hour. (author)