Phosphors for Radiation Detectors

2Organic Scintillators

Masanori Koshimizu

Graduate School of Engineering, Tohoku University, Sendai, Japan

2.1 Introduction

In this chapter, an overview of organic scintillators will be presented. In contrast to inorganic scintillators, the choice of elements is limited in organic scintillators. From the viewpoint of high‐energy photon detection, the low effective atomic number is generally a shortcoming of organic scintillators, because they are mainly composed of elements with low atomic numbers, such as carbon, hydrogen, oxygen, nitrogen, etc. Nevertheless, organic scintillators have various advantages, such as the use of scintillators in a liquid phase enables the detection of α‐ or β‐emitting radioactive isotopes dissolved in the liquid scintillators. Additionally, large‐scale detector systems can easily be constructed on the basis of liquid scintillators. Most of organic scintillators exhibit fast scintillation decay, which enables their use in the applications in which excellent time resolution or high counting‐rate detection capability are necessary. Plastic scintillators have high workability for their use in complicated shapes.

One of their important differences from inorganic scintillators is the occurrence of radiation‐induced ionization of molecules. Ionization of the constituent molecules in organic scintillators often results in a chemical reaction of radical species. Such chemical reactions are one of the causes of relatively low scintillation light yields ...