Suren Kandasamy Dissertation.pdf - University of Surrey

M.Sc DissertationChapter 2Background2.1 Types of detectorsDepending on the type, radiation detectors can be characterized into three majorgroups, such as Semiconductor detectors, Scintillator detectors and Gas Detectors. TheSemiconductor detectors are measure charge from the radiation event. The use ofsemiconductor materials as radiation detectors can result in a much larger number ofcarriers for a given incident radiation event than is possible with any other commondetector type. Consequently, the best energy resolution from radiation spectrometers inroutine use is achieved using semiconductor detectors. Of the available semiconductormaterials silicon predominates in the diode detectors used primarily for charged particlespectroscopy. Silicon detectors are most commonly used in α, β particle spectroscopy.But it is not suitable for X-rays and gamma rays because of it poor detection efficiency.Germanium is more widely used in gamma ray spectroscopy, since it has large volumeand high efficiency for X-rays and gamma rays. Though, highest energy resolution hasachieved for gamma ray spectroscopy by using HPGe (high purity germanium)detectors. All Germanium detectors should be cooled. Liquid nitrogen or cryo-coolers isusing for this purpose.Scintillator detectors measure light from the radiation event, which is convertedinto a current pulse via a photocathode. Normally two main types of Scintillatordetectors are available. They are Inorganic scintillators and Organic scintillators. Goodgamma efficiency, moderate/good energy resolutions are the best properties for theinorganic scintillators by using as detectors in gamma ray spectroscopy. Sodium Iodide(NaI), Barium Fluoride (BaF 2 ) and lately, cerium-doped lanthanum crystals, inparticular LaBr 3 :Ce and LaCl 3 :Ce are the good examples for inorganic scintillatordetectors. Also plastic scintillator (BC501) and liquid scintillator are the examples fororganic scintillator detectors. The organic scintillator detectors commonly called as“plastic” and have large volume, cheap, very fast pulses, poor energy resolution andlow gamma efficiency.K. Suren 3