Ionising Radiation Detectors: Anthracene, Cadmium Zinc Telluride, Civil Defense Geiger Counters, Cloud Chamber, Dosimeter, Film Badge Dosimeter, Gas

Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Pages: 46. Chapters: Anthracene, Cadmium zinc telluride, Civil Defense geiger counters, Cloud chamber, Dosimeter, Film badge dosimeter, Gaseous ionization detectors, Geiger Muller tube, Ionization chamber, Liquid scintillation counting, Lucas cell, Neutron detection, Phoswich detector, Photomultiplier, Proportional counter, Quartz fiber dosimeter, Scintillation counter, Scintillator, Semiconductor detector, Sodium iodide, Spinthariscope, Survey meter, Thermoluminescent Dosimeter, Wire chamber, Zinc sulfide. Excerpt: A scintillator is a material that exhibits scintillation the property of luminescence when excited by ionizing radiation. Luminescent materials, when struck by an incoming particle, absorb its energy and scintillate, i.e., re-emit the absorbed energy in the form of light. Sometimes, the excited state is metastable, so the relaxation back out of the excited state is delayed (necessitating anywhere from a few microseconds to hours depending on the material): the process then corresponds to either one of two phenomena, depending on the type of transition and hence the wavelength of the emitted optical photon: delayed fluorescence or phosphorescence, also called after-glow. A scintillation detector or scintillation counter is obtained when a scintillator is coupled to an electronic light sensor such as a photomultiplier tube (PMT), photodiode, or silicon photomultiplier. PMTs absorb the light emitted by the scintillator and reemit it in the form of electrons via the photoelectric effect. The subsequent multiplication of those electrons (sometimes called photo-electrons) results in an electrical pulse which can then be analyzed and yield meaningful information about the particle that originally struck the scintillator. Vacuum photodiodes are similar but do not amplify the signal while silicon photodiodes detect incoming photons by the excitation of charge carriers directly in the silicon. Silicon photomultipliers consist of an array of photodiodes which are reverse-biased with sufficient voltage to operate in avalanche mode, enabling each pixel of the array to be sensitive to single photons. The first device which used a scintillator was built in 1903 by Sir William Crookes and used a ZnS screen. The scintillations produced by the screen were visible to the naked eye if viewed by a microscope in a darkened room; the device was known as a spinthariscope. The technique led to a number of important discoveries but was obviously tedious. Scintillators gained additional att