Physics and Engineering of Radiation Detection

364 Chapter 6. Scintillation Detectors and Photodetectors

Radiation

Incident

θt

θi θr

Scintillation Photons

θp

θt

θp

θr

(Since )θr=θi

=>θp=π 2 −θr+θt

θp π

2

θi θt

π

2

−θr

π

2

π

2

θr θp π

2

θt+ π θp

2

π

2

θt

Scintillator

Light Guide

Photodetector

Or = − +

− + − + =π −

+

Figure 6.4.2: Transmission of scintillation photons through a fish-tail light

guide to a photodetector. Also shown is the derivation ofθpas a function

of the angle of incidenceθiand the tapering angleθt.

Example:

The scintillation material of a radiation detector is to be connected with a

photomultiplier tube through a fish-tail type light guide. Assume that the

light guide has a refractive index of 1.5 and the system will be used in air.