A. zyxwvutsrqp R. LARSIIDlAN-4K e t al. zyxwvuts : y-Radiation-Induced Thermoluminescence in LiFd 617 phys. stat. sol. (a) 63, 617 (1979) Subject classification: 20.3; 10.2; 13.4; 22.5.2 zyxwv Division of Radiological Protection, Bhabha Atomic Research Centre, l'rombay, Bombay1) y-Radiation-Induced Sensitization, Supralinearity, and Photostimulated Thermolumineseence in LiF TLD-100 Correlation Studies BY A. R. LAKSHMANAN, R. C. BHATT, and K. G. VOHRA With decreasing post-annealing temperature in the region 300 to 220 "C, the sensitization factor of TL glow peak 5 in LiF TLD-100 is found to decrease systematically from a value of 8 to 3. This is accompanied by a marked increase of intensity of the residual TL peaks occuring in the region 250 to 320 "C. This is a positive indication of the conversion, on thermal annealing, of trap centres responsible for the residual TL to those responsible for the sensitisation. The mecha- nism of sensitization is otherwise similar to that proposed by Nink and Kos. The sensitization factor of peak 6 (250 "C) is found nearly 3.5 times higher than that of peak 5 (195 "C). This ob- servation confirms Attix's theory of increased range of hole migration at higher temperatures. The model of Kos and Nink, after taking into account the influence of residual TL at low post- annealing temperatures, is found to explain satisfactorily the photostimulated TL in LiF. The increased supralinearity of photo-TL as compared to the TL due to y-rays is attributed to the dif- ference in the relative spatial distribution of trap centres and luminescence centres. Mit abnehmender Vor-Temperungstemperatur im Bereich 300 bis 220 "C wird gefunden, da13 der Sensibilisierungsfaktor des TL-Glowmaximums 5 in LiF TLD-100 systematisch vom Wert 8 auf 3 abnimnit. Dies ist begleitet von einem merklichen Anstieg der Intensitat der Rest-TL-Maxima im Bereich von 250 bis 320 "C. Das stellt eine positive Indikation fur die Konversion der fur die Rest- TL verantwortlichen Haftstellen nach thermischer Ausheilung in solche dar, die fur die Sensibili- sierung verantwortlich sind. Der Mechanismus der Sensibilisierung ist andererseits demjenigen ahnlich, der von Nink und Kos vorgeschlagen wurde. Der Sensibilisierungsfaktor des Maximum 6 (250 "C) ist fast 3,5mal hoher als der des Maximum zyxwv 5 (195 "C). Diese Beobachtung bestatigt die Theorie von Attix eines zunehmenden Bereichs von Lochermigration bei hoheren Temperaturen. Es wird gefunden, da13 das Model1 von Kos und Nink, nach Beriicksichtigung des Einflusses der Rest-TL bei niedrigen Vor-Temperungstemperaturen, befriedigend die photostimulierte TL in LiF erklart. Die zunehmende Supralinearitat der Photo-TL verglichen mit der TL gegeniiber y-Strah- lung wird dem Unterschied in der relativen raumlichen Verteilung der Trapzentren und Lumi- neszenzzrntren zugeschrieben. 1. Introduction LIP TLD( thernioluniinescence dosimetry)-100 phosphor, after high y-exposures and partial annealing, exhibits enhanced t hernioluminescence (TL) sensitivity. This is called radiation-induced sensitization. A number of models have been proposed to explain the niechanism of sensitization and supralinearity [l to 101. None of these models is able to explain all the experimental data [ll]. The earliest schemes suggested were those of the creation of traps [l] or luminescent centres [Z]. But these models were not accepted because the glow curve shape and TL emission spectrum of the sensitized and virgin phosphors remained the same. The competing deep traps proposed by Suntharalingam and Cameron [3] have never been observed. I n fact, the response ~ Bombay-400085, India.