Physics and Engineering of Radiation Detection

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).