Effect of deep traps on the sensitization in LiF (TLD-100) phosphor

Abstract

The effect of UV (253.7 nm) bleaching at room temperature (= 25 "C) as well as at 300 "C on the intensity of peak 10 (425 "C), and on radiation induced sensitization of peak 5 (210 "C) and peak 7 (270 "C) is studied in LiF (TLD-100) as a function of UV bleaching time. Intense W irradiation at 300 "C for 1 h almost completely removes the RTL peak 10 (reduced by about a factor of 200) and the sensitization factor (8/8,,) of peak 7 reduces from 35 to 1.1. The decay of peak 10 and the decay of sensitization of peak 7 appear to follow each other very well. On the basis of results presented here it is confirmed that peak 10 is responsible for the sensitization of peak 7. The conversion of peak 10-centres to peak 7-centres is suggested as one of the possible mechanisms for the sensitization of peak 7 during the test y-irradiation of the sensitized sample.Der EinfluB einer W (253,7 nm)-Tilgung bei Zimmertemperatur (e 25 "C) und bei 300 "C auf die Intensitit des Maximum 10 (425 "C) und auf die strahlungsinduzierte Sensibilisierung des Maximum 5 (210 "C) und Maximum 7 (270 "C) wird in LiF (TLD-100) in Abhiingigkeit von der W-Tilgungsdauer untersucht. Eine intensive UV-Bestrahlung bei 300 "C von 1 h beseitigt fast vollstiindig den RTL-Peak 10 (reduziert urn etwa den Faktor 200) und der Sensibilisierungsfaktor (S/S,) von Maximum 7 verringert sich von 35 auf 1,l. Die Abnahme von Maximum 10 und die Abnahme der Sensibilisierung von Maximum 7 scheinen gut aufeinander zu folgen. Auf der Grundlage der vorgelegten Ergebnisse wird bestitigt, daB Maximum 10 fur die Sensibilisierung des Maximum 7 verantwortlich ist. Es wird angenommen, daB die Umwandlung der Maximum-10-Zentren in Maximum-7-Zentren als einer der moglichen Mechanismen fur die Sensibilisierung des Maximum 7 wiihrend der y-Bestrahlung der sensibilisierten Probe darstellt.

Thermoluminescence of alkali halides doped with alkaline earth impurities

“…Models suggesting supralinearity and sensitization in trapping processes therefore appear less probable. Hence, in several models the supralinearity was attributed to removal of competition from nonluminescent centres (Chandra et al 1980;Lakshmanan et al 1982 and references therein), increase in luminescent centres or increased luminescence efficiency (Claffy et al 1968;Attix 1974Attix , 1975Zimmerman 1971). Semi-empirical calculations (Moharil 1983a) showed that the model of Lakshmanan et al (1982) can lead to supralinearity and sensitization of the observed magnitude.…”

Photoluminescence, optical absorption and XRD studies on X-ray irradiated terbium doped KBr crystals

“…The lattice parameters for the alkali halides have a wide range, varying from 7.34Å for RbI to 4.03Å for LiF. This gives the possibility of incorporating impurity ions of different sizes in their lattices [1][2][3][4]. The band gap of the alkali halides also has a wide range, with 10 eV for LiF to about 6 eV for RbI, which renders them intrinsically transparent in the UV, visible and near IR making them suitable for creating defect states in the gap that could be studied optically for their radiative and non-radiative recombination processes.…”

Thermoluminescence and optical studies on X-irradiated terbium-doped potassium bromide crystals

“…The ionic radius of K + is 1.33Å. This large ionic radius of potassium makes it possible to incorporate impurity ions of different sizes in their lattices [1][2][3][4]. The band gap of the alkali halides is in a wide range, with 10 eV for LiF to about 6 eV for RbI, which renders them intrinsically transparent in the UV, visible and near IR making them suitable for creating defect states in the gap that could be studied optically for their radiative and non radiative recombination processes.…”