6.1. Scintillation Mechanism and Scintillator Properties 327
Figure 6.1.5: Time profile of scintillation pulse for three different
scintillation materials (34).6.1.D Quenching.............................
Quenching describes the effect of decrease in light output of a scintillator due to
change in some parameter such as temperature, energy of the incident radiation,
impurity, or concentration of its constituents. Although the effects of these param-
eters will be discussed shortly but here we will very briefly describe the quenching
mechanisms.
D.1 SelfQuenching
The scintillation materials used in detectors are actually mixtures of two or more
materials. The light yield of the scintillators depends to a large extent on the
concentration of their constituents. In most scintillators the light output increases
with increase in the concentration of the primary fluor but then after reaching a
certain value it gets saturated.
D.2 ImpurityQuenching
Some types of scintillation materials are highly vulnerable to amount of impurities
they contain. The impurities can not only decrease their light output but can also
affect their optical properties. This type of quenching is so problematic in some
scintillators that all of their constituents must be used in highly purified form.
D.3 ThermalQuenching
When we discuss the dependence of temperature on scintillators, we will see that
some scintillation materials are highly vulnerable to large temperature changes. The