366 Chapter 6. Scintillation Detectors and Photodetectors
the outer surface of the fish-tail light guide as shown in Fig.6.4.3(b). However one
could also opt for enclosing the fish-tail light guide in a separate reflecting enclosure
as depicted in Fig. 6.4.3(a).
Radiation
Incident
Scintillation Photons
Scintillation Photons
Radiation
Incident
Reflecting Surface
Light Guide
(b)
(a)
Photodetector
Light Guide
Photodetector
Scintillator
Scintillator
Reflecting Surface
Figure 6.4.3: Two types of hybrid light guides. (a) A fish-tail
light guide is enclosed in a container having highly polished
reflecting inner surface. (b) The outer surface of a fish-tail
light guide has been covered with a reflecting paint.
The surface of the reflecting part of a hybrid light guide must be extremely
smooth and highly polished. Although the absorption of photons in such a surface
can not be totally avoided but careful construction can help minimize the loss.
6.5 Photodetectors
The photons produced by scintillators can be detected by a number of means, the
most notable of which are photomultiplier tubes (PMTs) and photodiodes (PDs).