Homework Sourse9 List types of counting detectors of beta and gamma particl
Solution
Detectors used for Gamma detection mainly exploit the property of it being an ionizing radiation i.e. gamma rays can ionize the medium they pass through. The trick is to count the no. of ionization and assess the radiation dose.
Popular detectors include gas-filled detectors, semidonductor detectors and scintillation detectors. In gas filled detectors the medium is gas (at some low pressure) and ions generated are collected through electrodes placed within and current through the electrodes (be it continuous or pulsed) is representative of the dose. The principle with semiconductor detectors is identical to that of the former except the fact that here the gas is replaced by semiconductor material and instead of ions current flow is constituted by electron-hole pairs. Scintillation detectors make use of special crystals called scintillators which give away light when energy of the radiation is imparted to them. Most common scintillaors used are NaI(Tl) and CsI(Tl) although there are variety of scintillators available. Photons generated by scintillators which are typically in visible or UV range are amplified and converted into electrical signals using photomultiplier tubes (PMT).
Charge collecting detectors have three major operating regimes: a) Ionization Chamber region, b) Proportional Counter region and c) Geiger-Muller region. Detectors are operated in IC region when radiation flux is very high (Ex: in reactor cores) where the signal output is measured as current and in GM region where radiation flux is very low (Ex: in surveillance devices or low activity wastes) where readout is in terms of counts per second. Operation in PC region is necessary when energy spectroscopy of the radiation is of interest i.e. energy of the gamma rays is needed to be studied. Most of the times such detectors are used to characterize radionuclei based on gamma ray spectroscopy.
However,for beta particle we use GEIGER COUNTER.
