4.3.3.3 Particle detectors

Silicon surface barrier detectors are used to detect alpha particles. In these detectors, the p-n junction is formed by oxidation of the surface of a n-type silicon to form surface states. As the alpha particle loose energy while travelling through the matter, the use of surface detectors for in-situ applications is limited to the analysis of well resolved alpha emission energies.

Some instruments have been designed for in-situ measurement of radon and thoron gases in air. An arrangement of detectors is placed in a chamber through which the air is continuously pumped.