ABSTRACT
A radiation detector generally produces a response (i.e., a signal) to the radiation incident on it which is measured by a suitable measuring system. This chapter discusses the detectors used for area monitoring. Gas-filled detectors (GFD) are generally cylindrical, spherical, or plane parallel geometry detectors with a wall and an enclosed gas. The chapter also discusses the details of the detectors operating in the regions that are considered useful for particle identification or radiation monitoring. It explains the recombination region and ionization chamber regions. The most accurate and reliable GFD systems are ion chamber based and are the ones used in radiation oncology departments. In the proportional region, the primary ionization produced in the detector is amplified by the secondary ionization produced by primary electrons in ionization by collision. Quench gas is used as ultraviolet (UV) absorbers to prevent the production of spurious pulses in proportional counters by the UV photons-induced secondary avalanches.
