S.a. Bagheri, Dr. R. Malekfar,
Volume 7, Issue 3 (12-2009)
Abstract
Background: Similar to the thermoluminescence
(TL) spectra, the optical parameters variations can
also be used in TL crystals for dosimetry purposes.
These optical parameters can include absorption,
transmission and reflection coefficients. Materials
and Methods: Single crystals of KBr and KCl which
have been used in this research were grown from
laboratory grade extra pure precursor powders.
Crystal growth was performed by using a Czochralski
crystal growth apparatus. The grown crystals were
irradiated using a 60Co source to doses of 0.5, 1.0
and 1.5 kGy. Reflection spectra were measured by a
Shimatzu UVPC 3101 model spectrometer in 5 and
45 incident degree angles. Results: Optical properties
of KClxBr1-x mixed crystals surfaces irradiated with
gamma radiation were determined. Refraction indices
and dielectric coefficients of the crystals in the optical
region of 250-750 nm were studied. It was observed
that both irradiated and non-irradiated mixed crystals
had similar surface behaviour in the order of n ≈ 1.4
and ε ≈ 2.2 in the whole range of 250-750 nm, while
colour intensities of irradiated samples were different
for various irradiation doses. The reason could have
been due to the permanent heat transfer effects with
the outer surface layers of the crystal and the rapid
relaxation of the excited states in defected surface of
the crystal. Conclusion: Reflection spectra along with
the crystal surface optical parameters could not be
efficient for the dosimetry purposes and additional
information such as absorption or transmission data
would also be necessary Iran. J. Radiat. Res., 2009 7
(3): 165-169
