332 Chapter 6. Scintillation Detectors and Photodetectors
Figure 6.1.9: Pulse decay ofLu 2 SiO 5 :Cecrystal at different
temperaturs (17).technique gives acceptable results for most applications but in high resolution sys-
tems extra care should be exercised while extrapolating the given average decay
constant to another temperature may not be very accurate. The reason is that the
temperature profiles of the individual decay constants can be quite different from
one another. Fig.6.1.10 shows the temperature dependence of two decay constants
of pureCsI. It can be seen that the two curves have different slopes and although
they can be individually extrapolated using a straight line fit but the extrapolation
of the average would require a non-linear fit.
6.1.J RadiationDamage
The scintillators used in hostile radiation environments are prone to damage caused
by high instantaneous and integrated radiation doses. Monitoring the gradual degra-
dation of the detector response with time is therefore a standard practice in such
laboratories. Not all materials behave in the same way with respect to radiation
damage, though. In fact, a number of newly developed scintillators have shown
good resistance to radiation damage and therefore suchradiation hardmaterials are
preferred over the conventional ones in applications involving high radiation fields.
Although all types of scintillators show radiation induced damage but generally
liquid scintillators have been found to be least susceptible to radiation. Plastic
scintillators, on the other hand, are highly prone to radiation damage. We will
discuss the damage mechanisms of different types of scintillators in their respective
sections.