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TLD: basic principles
•
In imperfect crystals (i.e. TLD100: LiF doped
with Mg and Ti in trace amounts) part of the
energy absorbed by ionising radiation is
stored and re-emitted upon heating in the
form of light. Light is detected and correlated
to the absorbed dose.
•
Stored energy is in the form of the fraction of
e
-
freed by irradiation, that is trapped in a
metastable energy state.
•
When the crystal is heated, part of these e
-
recombine with holes trapped in
luminescence centers and emit light (thermo-
luminescence, TL)
•
The curve of TL output versus temperature
(glow curve) shows peaks characteristic of
trap energy depths in the crystal
•
Besides TL crystal, glow curve shape varies
with heating rate & max temperature
Figures from: Attix: Introduction to radiological physics and radiation dosimetry, © 2004 by Wiley-VCH Verlag GmbH & Co
Mayles, Nahum, Rosenwald (Eds): Handbook of radiotherapy physics: theory and practice, © 2007 by Taylor & Francis Group LLC
Rogers & Cygler (Eds), Clinical dosimetry measurements in radiotherapy (2009 AAPM Summer School), Monograph No. 34, Medical Physics Publishing 2011