{"id":26285,"date":"2020-02-11T17:28:50","date_gmt":"2020-02-11T17:28:50","guid":{"rendered":"http:\/\/sitepourvtc.com\/?page_id=26285"},"modified":"2023-06-24T08:36:40","modified_gmt":"2023-06-24T08:36:40","slug":"scintillation-counter-scintillation-detector","status":"publish","type":"page","link":"https:\/\/sitepourvtc.com\/nuclear-engineering\/radiation-detection\/scintillation-counter-scintillation-detector\/","title":{"rendered":"Scintillation Counter &#8211; Scintillation Detector"},"content":{"rendered":"<div   id="8n9s8rpp6h"     class=\"lgc-column lgc-grid-parent lgc-grid-100 lgc-tablet-grid-100 lgc-mobile-grid-100 lgc-equal-heights \"><div   id="8n9s8rpp6h"     class=\"inside-grid-column\">\n<figure id=\"attachment_26292\" aria-describedby=\"caption-attachment-26292\" style=\"width: 425px\" class=\"wp-caption alignright\"><a href=\"http:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/02\/Scintillation_Counter-Photomultiplier-Tube.jpg\"><img loading=\"lazy\" class=\" wp-image-26292\" src=\"http:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/02\/Scintillation_Counter-Photomultiplier-Tube-1024x637.jpg\" alt=\"Scintillation_Counter - Photomultiplier Tube\" width=\"435\" height=\"271\" srcset=\"https:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/02\/Scintillation_Counter-Photomultiplier-Tube-1024x637.jpg 1024w, https:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/02\/Scintillation_Counter-Photomultiplier-Tube-300x187.jpg 300w, https:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/02\/Scintillation_Counter-Photomultiplier-Tube-768x478.jpg 768w\" sizes=\"(max-width: 435px) 100vw, 435px\" \/><\/a><figcaption id=\"caption-attachment-26292\" class=\"wp-caption-text\">Apparatus with a scintillating crystal, photomultiplier, and data acquisition components. Source: wikipedia.org License CC BY-SA 3.0<\/figcaption><\/figure>\n<p>A <strong>scintillation counter<\/strong> or <strong>scintillation detector<\/strong> is a radiation detector that uses the effect known as <strong>scintillation<\/strong>. Scintillation is a <strong>flash of light<\/strong> produced in a transparent material by passing a particle (an electron, an alpha particle, an ion, or a high-energy photon). Scintillation occurs in the scintillator, a key part of a scintillation detector. In general, a scintillation detector consists of:<\/p>\n<ul>\n<li><strong>Scintillator<\/strong>. A scintillator generates photons in response to incident radiation.<\/li>\n<li><strong>Photodetector<\/strong>. A sensitive photodetector (usually a photomultiplier tube (PMT), a charge-coupled device (CCD) camera, or a photodiode) converts the light to an electrical signal, and electronics process this signal.<\/li>\n<\/ul>\n<p>The basic principle of operation involves the radiation reacting with a scintillator, which produces a series of flashes of varying intensity. The intensity of the flashes is proportional to the energy of the radiation, and this feature is very important. These counters are suited to measure the energy of gamma radiation (<strong>gamma spectroscopy<\/strong>) and, therefore, can be used to identify gamma-emitting isotopes.<\/p>\n<p>Scintillation counters are widely used in <a href=\"http:\/\/sitepourvtc.com\/nuclear-engineering\/radiation-protection\/\">radiation protection<\/a>, an assay of radioactive materials, and physics research because they can be made inexpensively yet with good efficiency and can measure both the intensity and the energy of incident radiation. Hospitals worldwide have gamma cameras based on the scintillation effect; therefore, they are also called <strong>scintillation cameras.<\/strong><\/p>\n<p>The advantages of a scintillation counter are its efficiency and possible high precision and counting rates. These latter attributes result from the extremely short duration of the light flashes, from about 10<sup>-9<\/sup> \u00a0(organic scintillators) to 10<sup>-6<\/sup> (inorganic scintillators) seconds. The <strong>intensity of the flashes<\/strong> and the amplitude of the output voltage pulse are <strong>proportional to the energy of the radiation<\/strong>. Therefore, scintillation counters can be used to determine the energy and the number of the exciting particles (or gamma photons). For gamma spectrometry, the most common detectors include <strong>sodium iodide (NaI) scintillation counters<\/strong> and high-purity germanium detectors.<\/p>\n<h2>Scintillation Counter-Principle of Operation<\/h2>\n<p>The operation of scintillation counters is summarized in the following points:<\/p>\n<ul>\n<li>\n<figure id=\"attachment_26289\" aria-describedby=\"caption-attachment-26289\" style=\"width: 460px\" class=\"wp-caption alignright\"><a href=\"http:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/02\/Scintillation_Detector.gif\"><img loading=\"lazy\" class=\"size-full wp-image-26289\" src=\"http:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/02\/Scintillation_Detector.gif\" alt=\"Scintillation Counter - Principle of Operation\" width=\"470\" height=\"450\" \/><\/a><figcaption id=\"caption-attachment-26289\" class=\"wp-caption-text\">Scintillation Counter-Principle of Operation. Source: wikipedia.org License: Public Domain<\/figcaption><\/figure>\n<p><a href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/atomic-nuclear-physics\/radiation\/ionizing-radiation\/\">Ionizing radiation<\/a> enters the <strong>scintillator<\/strong> and interacts with the scintillator material, and this causes <a href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/atomic-nuclear-physics\/fundamental-particles\/what-is-electron-properties-of-electron\/\">electrons<\/a> to be raised to an <strong>excited state<\/strong>.<\/p>\n<ul>\n<li>For charged particles, the track is the path of the particle itself.<\/li>\n<li>For <a href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/atomic-nuclear-physics\/fundamental-particles\/photon\/gamma-ray\/\">gamma rays<\/a> (uncharged), their energy is converted to an energetic electron via either the <a href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/interaction-radiation-matter\/interaction-gamma-radiation-matter\/photoelectric-effect\/\">photoelectric effect<\/a>, <a href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/interaction-radiation-matter\/interaction-gamma-radiation-matter\/compton-scattering\/\">Compton scattering<\/a>, or <a href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/interaction-radiation-matter\/interaction-gamma-radiation-matter\/pair-production\/\">pair production<\/a>.<\/li>\n<\/ul>\n<\/li>\n<li>The excited atoms of the scintillator material<strong> de-excite<\/strong> and rapidly <strong>emit a photon<\/strong> in the visible (or near-visible) light range. The quantity is proportional to the energy deposited by the ionizing particle, and the material is said to fluoresce.<\/li>\n<li>Three classes of phosphors are used:\n<ul>\n<li>inorganic crystals,<\/li>\n<li>organic crystals,<\/li>\n<li>plastic phosphors.<\/li>\n<\/ul>\n<\/li>\n<li>The light created in the scintillator strikes the <strong>photocathode<\/strong> of a <strong>photomultiplier tube<\/strong>, releasing at most one photoelectron per photon.<\/li>\n<li>Using a voltage potential, this group of <strong>primary electrons<\/strong> is electrostatically accelerated and focused so that they strike the first <strong>dynode<\/strong> with enough energy to release additional electrons.<\/li>\n<li>These <strong>secondary electrons<\/strong> are attracted and strike a second dynode releasing more electrons. This process occurs in the photomultiplier tube.<\/li>\n<li>Each subsequent dynode impact releases further electrons, so there is a current amplifying effect at each dynode stage. Each stage is at a higher potential than the previous to provide the accelerating field.<\/li>\n<li>The primary signal is multiplied, and this amplification continues through 10 to 12 stages.<\/li>\n<li>At the <strong>final dynode<\/strong>, sufficient electrons are available to produce a <strong>pulse<\/strong> of sufficient magnitude for further amplification. This pulse carries information about the energy of the original incident radiation, and the number of such pulses per unit of time also gives information about the intensity of the radiation.<\/li>\n<\/ul>\n<p>A <strong>scintillation detector<\/strong> or <strong>scintillation counter<\/strong> is obtained when a scintillator is coupled to an electronic light sensor such as:<\/p>\n<ul>\n<li>a photomultiplier tube (PMT),<\/li>\n<li>a charge-coupled device (CCD) camera,<\/li>\n<li>photodiode<\/li>\n<\/ul>\n<p>All these devices may be used in scintillation counters, and all convert the light to an electrical signal and contain electronics to process this signal. A photomultiplier tube (PMT) absorbs the light emitted by the scintillator and re-emits it in the form of electrons via the photoelectric effect. The PMT has been the main choice for photon detection ever since because they have high quantum efficiency and high amplification. Lately, however, semiconductors have begun to compete with the PMT. The photodiode, for example, has higher quantum efficiency in the visible range and above, lower power consumption, and smaller size.<\/p>\n<p>Vacuum photodiodes are similar but do not amplify the signal, while silicon photodiodes, on the other hand, detect incoming photons by the excitation of charge carriers directly in the silicon.<\/p>\n<p>Many portable gamma cameras for medical imaging use <strong>scintillator-CCD-based detectors<\/strong>. In this case, a scintillator converts the incident radiation (X-rays usually) into visible wavelength photons, which the CCD camera can directly detect.<\/p>\n<p>Note that the term quantum efficiency (QE) may apply to a photosensitive device&#8217;s incident photon to converted electron (IPCE) ratio. The quantum efficiency for the photodiode is high (60-80%) compared to the PMT (20-30%), which gives a higher energy resolution.<\/p>\n<h2><strong>Scintillation Materials &#8211; Scintillators<\/strong><\/h2>\n<p><strong>Scintillators<\/strong> are kinds of materials that provide detectable photons in the visible part of the light spectrum, following the passage of a charged particle or a photon. The scintillator consists of a <strong>transparent crystal<\/strong>, usually a phosphor, plastic, or organic liquid, that fluoresces when struck by ionizing radiation. The scintillator must also be transparent to its light emissions and have a short decay time. The scintillator must also be shielded from ambient light so that external photons do not swamp the ionization events caused by incident radiation. A thin opaque foil, such as aluminized mylar, is often used to achieve this. However, it must have a low enough mass to minimize undue <a href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/interaction-radiation-matter\/interaction-gamma-radiation-matter\/gamma-ray-attenuation\/\">attenuation<\/a> of the measured incident radiation.<\/p>\n<p>There are primarily two types of <strong>scintillators<\/strong> commonly used in nuclear and particle physics: organic or plastic scintillators and inorganic or crystalline scintillators.<\/p>\n<h3><strong>Inorganic Scintillators<\/strong><\/h3>\n<figure id=\"attachment_26350\" aria-describedby=\"caption-attachment-26350\" style=\"width: 290px\" class=\"wp-caption alignright\"><a href=\"http:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/02\/CsITl-crystal.jpg\"><img loading=\"lazy\" class=\"size-medium wp-image-26350\" src=\"http:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/02\/CsITl-crystal-300x225.jpg\" alt=\"CsI(Tl) scintillation crystal\" width=\"300\" height=\"225\" srcset=\"https:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/02\/CsITl-crystal-300x225.jpg 300w, https:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/02\/CsITl-crystal-768x576.jpg 768w, https:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/02\/CsITl-crystal-1024x768.jpg 1024w, https:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/02\/CsITl-crystal.jpg 1280w\" sizes=\"(max-width: 300px) 100vw, 300px\" \/><\/a><figcaption id=\"caption-attachment-26350\" class=\"wp-caption-text\">CsI(Tl) scintillation crystal. Source: wikipedia.de License: CC BY-SA 3.0<\/figcaption><\/figure>\n<p><strong>Inorganic scintillators<\/strong> are usually crystals grown in high-temperature furnaces. They include lithium iodide (LiI), <strong>sodium iodide (NaI)<\/strong>, cesium iodide (CsI), and zinc sulfide (ZnS). <strong>NaI(Tl)<\/strong> (thallium-doped sodium iodide) is the most widely used scintillation material. The iodine provides most of the stopping power in sodium iodide (since it has a high Z = 53). These crystalline scintillators are characterized by high density, high atomic number, and pulse decay times of approximately 1 microsecond (<strong>~ 10<sup>-6 <\/sup>sec<\/strong>). Scintillation in inorganic crystals is typically slower than in organic ones. They exhibit high efficiency for the detection of gamma rays and are capable of handling high count rates. Inorganic crystals can be cut to small sizes and arranged in an <strong>array configuration<\/strong> to provide position sensitivity. This feature is widely used in <strong>medical imaging<\/strong> to detect <a href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/atomic-nuclear-physics\/radiation\/x-rays-roentgen-radiation\/\">X-rays<\/a> or <a href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/atomic-nuclear-physics\/fundamental-particles\/photon\/gamma-ray\/\">gamma rays<\/a>. <strong>Inorganic scintillators<\/strong> are better at detecting gamma rays and X-rays than organic scintillators. This is due to their high density and atomic number, which gives a high electron density. A disadvantage of some inorganic crystals, e.g., NaI, is their <strong>hygroscopicity<\/strong>, a property that requires them to be housed in an airtight container to protect them from moisture.<\/p>\n<div   id="8n9s8rpp6h"    class=\"su-accordion su-u-trim\">\n<div   id="8n9s8rpp6h"    class=\"su-spoiler su-spoiler-style-default su-spoiler-icon-plus su-spoiler-closed\" data-scroll-offset=\"0\"><div   id="8n9s8rpp6h"    class=\"su-spoiler-title\" tabindex=\"0\" role=\"button\"><span class=\"su-spoiler-icon\"><\/span>Thallium-doped Sodium Iodide - NaI(Tl) scintillators<\/div><div   id="8n9s8rpp6h"    class=\"su-spoiler-content su-u-clearfix su-u-trim\">\n<p><strong>Thallium-doped Sodium Iodide<\/strong><strong> &#8211; NaI(Tl) scintillators<\/strong><\/p>\n<p><strong>NaI(Tl) (thallium-doped sodium iodide)<\/strong> is the most widely used scintillation material. NaI(Tl) as the scintillator is used in scintillation detectors, traditionally in nuclear medicine, geophysics, nuclear physics, and environmental measurements. The iodine provides most of the stopping power in sodium iodide (since it has a high Z = 53). These crystalline scintillators are characterized by high density, high atomic number, and pulse decay times of approximately 1 microsecond (~ 10<sup>-6 <\/sup>sec). The wavelength of maximum emission is <strong>415 nm<\/strong>. Scintillation in inorganic crystals is typically slower than in organic ones. They exhibit high efficiency for the detection of gamma rays and are capable of handling high count rates. Inorganic crystals can be cut to small sizes and arranged in an array configuration to provide position sensitivity. This feature is widely used in medical imaging to detect X-rays or gamma rays. Inorganic scintillators are better at detecting gamma rays and X-rays. The <strong>NaI(Tl) scintillator<\/strong> has a higher energy resolution than a <a href=\"http:\/\/sitepourvtc.com\/nuclear-engineering\/radiation-detection\/ga搜索引擎优化us-ionization-detector\/proportional-counter-proportional-detector\/\">proportional counter<\/a>, allowing more accurate energy determinations. This is due to their high density and atomic number, which gives a high electron density. A disadvantage of some inorganic crystals, e.g., NaI, is their hygroscopicity, a property that requires them to be housed in an airtight container to protect them from moisture. The crystals are usually coupled with a photomultiplier tube in a hermetically sealed assembly.<\/p>\n<\/div><\/div>\n<div   id="8n9s8rpp6h"    class=\"su-spoiler su-spoiler-style-default su-spoiler-icon-plus su-spoiler-closed\" data-scroll-offset=\"0\"><div   id="8n9s8rpp6h"    class=\"su-spoiler-title\" tabindex=\"0\" role=\"button\"><span class=\"su-spoiler-icon\"><\/span>Thallium-doped Caesium Iodide - CsI(Tl) scintillators<\/div><div   id="8n9s8rpp6h"    class=\"su-spoiler-content su-u-clearfix su-u-trim\">\n<p><strong>Thallium-doped Cesium Iodide<\/strong><strong> &#8211; CsI(Tl) scintillators<\/strong><\/p>\n<p>Cesium iodide (CsI) in crystalline form is used as the scintillator for detecting <a href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/atomic-nuclear-physics\/fundamental-particles\/what-is-proton-properties-of-proton\/\"><strong>protons<\/strong><\/a> and <strong><a href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/atomic-nuclear-physics\/fundamental-particles\/alpha-particle\/\">alpha particles<\/a><\/strong>. Pure CsI is a fast and dense scintillating material with a relatively low light yield that increases significantly with cooling. The drawbacks of CsI are a high-temperature gradient and a slight hygroscopicity.<\/p>\n<p><strong>Thallium-doped Caesium Iodide<\/strong> has an effective atomic number of 54 and a density of 4.51 g\/cm<sup>3<\/sup>. CsI(TI) is also hygroscopic and should not be subjected to high humidity or water. CsI(TI) has different decay times for different particles (680ns and 3340ns) and can be used to determine different kinds of radiation. The emission spectrum peaked at 540-560 nm.<\/p>\n<\/div><\/div>\n<\/div>\n<h3><strong>Organic Scintillators<\/strong><\/h3>\n<p><strong>Organic scintillators<\/strong> are kinds of organic materials that provide detectable photons in the visible part of the light spectrum, following the passage of a charged particle or a photon. The scintillation mechanism in organic materials is quite different from the mechanism in inorganic crystals. In inorganic scintillators, e.g., NaI, CsI, the scintillation arises because of the structure of the crystal lattice. The fluorescence mechanism in organic materials arises from transitions in the energy levels of a single molecule. Therefore the fluorescence can be observed independently of the physical state (vapor, liquid, solid).<\/p>\n<p>Organic scintillators generally have fast decay times (typically <strong>~10<sup>-8 <\/sup>sec<\/strong>), while inorganic crystals are usually far slower (~10<sup>-6 <\/sup>sec), although some also have fast components in their response. There are three types of organic scintillators:<\/p>\n<ul>\n<li><strong>Pure organic crystals<\/strong>. Pure organic crystals include crystals of anthracene, stilbene, and naphthalene. The decay time of this type of phosphor is approximately 10 nanoseconds. This type of crystal is frequently used in the detection of <a href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/atomic-nuclear-physics\/fundamental-particles\/beta-particle\/\">beta particles<\/a>. They are durable, but their response is anisotropic (which spoils energy resolution when the source is not collimated). They cannot be easily machined, nor can they be grown in large sizes. Therefore they are not very often used.<\/li>\n<li><strong>Liquid organic solutions<\/strong>. Liquid organic solutions are produced by dissolving an organic scintillator in a solvent.<\/li>\n<li><strong>Plastic scintillators<\/strong>. Plastic phosphors are made by adding scintillation chemicals to a plastic matrix. The decay constant is the shortest of the three phosphor types, approaching 1 or 2 nanoseconds. Plastic scintillators are more appropriate for use in <strong>high-flux environments<\/strong> and high dose rate measurements. The plastic has a high hydrogen content. Therefore, it is useful for <strong>fast neutron detectors<\/strong>. It takes substantially more energy to produce a detectable photon in a scintillator than in an electron-ion pair through ionization (typically by a factor of 10). Because inorganic scintillators produce more light than organic scintillators, they are better for applications at low energies.<\/li>\n<\/ul>\n<h2>Photomultiplier Tube<\/h2>\n<p><strong>Photomultiplier tubes<\/strong> (PMTs) are photon detection device that uses the photoelectric effect combined with secondary emission to convert light into an electrical signal. A photomultiplier absorbs light emitted by the scintillator and re-emits it in the form of electrons via the <a href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/interaction-radiation-matter\/interaction-gamma-radiation-matter\/photoelectric-effect\/\">photoelectric effect<\/a>. The PMT has been the main choice for photon detection ever since because they have high quantum efficiency and high amplification.<\/p>\n<h3>Components of Photomultiplier Tube<\/h3>\n<p>The device consists of several components, and these components are shown in the figure.<\/p>\n<ul>\n<li>\n<figure id=\"attachment_26292\" aria-describedby=\"caption-attachment-26292\" style=\"width: 290px\" class=\"wp-caption alignright\"><a href=\"http:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/02\/Scintillation_Counter-Photomultiplier-Tube.jpg\"><img loading=\"lazy\" class=\"size-medium wp-image-26292\" src=\"http:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/02\/Scintillation_Counter-Photomultiplier-Tube-300x187.jpg\" alt=\"Scintillation_Counter - Photomultiplier Tube\" width=\"300\" height=\"187\" srcset=\"https:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/02\/Scintillation_Counter-Photomultiplier-Tube-300x187.jpg 300w, https:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/02\/Scintillation_Counter-Photomultiplier-Tube-768x478.jpg 768w, https:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/02\/Scintillation_Counter-Photomultiplier-Tube-1024x637.jpg 1024w\" sizes=\"(max-width: 300px) 100vw, 300px\" \/><\/a><figcaption id=\"caption-attachment-26292\" class=\"wp-caption-text\">Apparatus with a scintillating crystal, photomultiplier, and data acquisition components. Source: wikipedia.org License CC BY-SA 3.0<\/figcaption><\/figure>\n<p><strong>Photocathode<\/strong>. Right after a thin entry window is a photocathode made of material in which the valence electrons are weakly bound and have a high cross-section for converting photons to electrons via the photoelectric effect. For example, Cs<sub>3<\/sub>Sb (cesium-antimony) may be used. As a result, the light created in the scintillator strikes the photocathode of a photomultiplier tube, releasing at most one photoelectron per photon.<\/p><\/li>\n<li><strong>Dynodes<\/strong>. Using a voltage potential, this group of primary electrons is electrostatically accelerated and focused so that they strike the first dynode with enough energy to release additional electrons. There is a series (&#8220;stages&#8221;) of dynodes made of relatively low work function material. These electrodes are operated at increasing potential (e.g., ~100-200 V between dynodes). At the dynode, the electrons are multiplied by secondary emission. The next dynode has a higher voltage which makes the electrons released from the first accelerate towards it. At each dynode,<strong> 3-4 electrons<\/strong> are released for every incident electron, and with <strong>6 to 14 dynodes,<\/strong> the total gain, or electron amplification factor, will be in the range of ~<strong>10<sup>4<\/sup>-10<sup>7<\/sup><\/strong> when they reach the anode. Typical operating voltages are in the range of 500 to 3000 V. At the final dynode, and sufficient electrons are available to produce a pulse of sufficient magnitude for further amplification. This pulse carries information about the energy of the original incident radiation, and the number of such pulses per unit of time also gives information about the intensity of the radiation.<\/li>\n<\/ul>\n<h3>Quantum Efficiency<\/h3>\n<p>The sensitivity of a photocathode is usually quoted in terms of <strong>quantum efficiency<\/strong>. In general, the term quantum efficiency (QE) may apply to a photosensitive device&#8217;s <strong>incident photon to converted electron<\/strong> (<strong>IPCE<\/strong>) <strong>ratio<\/strong>. The quantum efficiency of the photocathode is defined as the probability for the conversion of incident photons to an electrical signal and is defined as:<\/p>\n<p><a href=\"http:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/02\/Quantum-Efficiency-Photomultiplier-Tube.png\"><img loading=\"lazy\" class=\"aligncenter size-full wp-image-26316\" src=\"http:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/02\/Quantum-Efficiency-Photomultiplier-Tube.png\" alt=\"Quantum Efficiency - Photomultiplier Tube\" width=\"424\" height=\"67\" srcset=\"https:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/02\/Quantum-Efficiency-Photomultiplier-Tube.png 424w, https:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/02\/Quantum-Efficiency-Photomultiplier-Tube-300x47.png 300w\" sizes=\"(max-width: 424px) 100vw, 424px\" \/><\/a><\/p>\n<p>The quantum efficiency of any photosensitive device is a strong function of the wavelength of the incident light, and an effort is made to match the spectral response of the photocathode to the emission spectrum of the scintillator in use. In the <strong>photomultiplier tube,<\/strong> the quantum efficiency is limited to <strong>20-30%<\/strong>, but an average quantum efficiency over the emission spectrum of a typical scintillator is about <strong>15-20%<\/strong>.<\/p>\n<p>The standard for quotation is the number of photoelectrons per keV energy loss by fast electrons in a <strong>NaI(Tl) scintillator<\/strong>. About 8 ~ 10 photoelectrons are produced per keV energy loss for the peak quantum efficiency. Therefore, the average energy loss required to create a single photoelectron is ~ 100 eV, much bigger than the values in gas-filled or semiconductor detectors.<\/p>\n<p>The PMT has been the main choice for photon detection ever since because they have high quantum efficiency and high amplification. Lately, however, semiconductors have begun to compete with the PMT. The photodiode, for example, has higher quantum efficiency in the visible range and above, lower power consumption, and smaller size. The quantum efficiency for the photodiode is high (60-80%) compared to the PMT (20-30%), which gives a higher energy resolution.<\/p>\n<h2>Photodiodes &#8211; Scintillation Counter<\/h2>\n<p>A scintillation detector or scintillation counter is obtained when a scintillator is coupled to an electronic light sensor such as:<\/p>\n<ul>\n<li>a photomultiplier tube (PMT),<\/li>\n<li>a charge-coupled device (CCD) camera,<\/li>\n<li><strong>photodiode<\/strong><\/li>\n<\/ul>\n<p>All these devices may be used in scintillation counters, and all convert the light to an electrical signal and contain electronics to process this signal. A photodiode is a semiconductor device that converts light into an electrical current. This semiconductor device consists of a thin layer of silicon in which the light is absorbed, after which free charge carriers (electrons and holes) are created. A conventional photodiode most often refers to a PIN diode. PIN means that the p and the n doped sides are separated by a depleted i-region. Electrons and holes are collected at the anode and cathode of the diode. This results in a photocurrent that is the output of the diode. The charge is, however, not amplified, making the output signal amplitude small. This makes the photodiode sensitive to electronic noise. On the other hand, the quantum efficiency for the photodiode is high (60-80%) compared to the PMT (20-30%), which gives a higher energy resolution.<\/p>\n<h2>Detection of Alpha, Beta, and Gamma Radiation using Scintillation Counter<\/h2>\n<p><strong>Scintillation counters<\/strong> are used to measure radiation in various applications, including hand-held radiation survey meters, personnel and environmental monitoring for <a href=\"http:\/\/sitepourvtc.com\/nuclear-engineering\/radiation-protection\/protection-from-exposures\/radioactive-contamination\/\">radioactive contamination<\/a>, medical imaging, radiometric assay, nuclear security, and nuclear plant safety. They are widely used because they can be made inexpensively yet with good efficiency and can measure both the intensity and the energy of incident radiation.<\/p>\n<p>Scintillation counters can be used to detect <a href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/atomic-nuclear-physics\/radiation\/alpha-radiation\/\">alpha<\/a>, <a href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/atomic-nuclear-physics\/radiation\/beta-radiation\/\">beta<\/a>, and <a href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/atomic-nuclear-physics\/fundamental-particles\/photon\/gamma-ray\/\">gamma radiation<\/a>, and they can also be used for the\u00a0<a href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/atomic-nuclear-physics\/fundamental-particles\/neutron\/detection-neutrons\/\">detection of neutrons<\/a>. For these purposes, different scintillators are used:<\/p>\n<ul>\n<li><a href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/interaction-radiation-matter\/interaction-heavy-charged-particles\/\"><strong>Alpha Particles and Heavy Ions<\/strong><\/a>. Due to the very high ionizing power of heavy ions, scintillation counters are usually not ideal for the detection of heavy ions. For equal energies, a proton will produce 1\/4 to 1\/2 the light of an electron, while alpha particles will produce only about 1\/10 the light. Where needed, inorganic crystals, e.g., CsI(Tl) and ZnS(Ag) (typically used in thin sheets as \u03b1-particle monitors), should be preferred to organic materials. Pure CsI is a fast and dense scintillating material with a relatively low light yield that increases significantly with cooling. The drawbacks of CsI are a high-temperature gradient and a slight hygroscopicity.<\/li>\n<li><a href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/interaction-radiation-matter\/interaction-beta-radiation\/\"><strong>Beta Particles<\/strong><\/a>. For the detection of beta particles, organic scintillators can be used. Pure organic crystals include crystals of anthracene, stilbene, and naphthalene. The decay time of this type of phosphor is approximately 10 nanoseconds. This type of crystal is frequently used in the detection of beta particles. <strong>Organic scintillators<\/strong>, having a<strong> lower Z<\/strong> than inorganic crystals, are best suited for detecting low-energy (&lt; 10 MeV) beta particles.<\/li>\n<li><a href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/interaction-radiation-matter\/interaction-gamma-radiation-matter\/\"><strong>Gamma Rays<\/strong><\/a>. <strong>High-Z materials<\/strong> are best suited as scintillators for the detection of gamma rays. <strong>NaI(Tl)<\/strong> (thallium-doped sodium iodide) is the most widely used scintillation material. The iodine provides most of the stopping power in sodium iodide (since it has a high Z = 53). These crystalline scintillators are characterized by high density, high atomic number, and pulse decay times of approximately 1 microsecond (~ 10<sup>-6 <\/sup>sec). Scintillation in inorganic crystals is typically slower than in organic ones. They exhibit high efficiency for the detection of gamma rays and are capable of handling high count rates. Inorganic crystals can be cut to small sizes and arranged in an array configuration to provide position sensitivity. This feature is widely used in medical imaging to detect X-rays or gamma rays. Inorganic scintillators are better at detecting gamma rays and X-rays. This is due to their high density and atomic number, which gives a high electron density.<\/li>\n<li><a href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/atomic-nuclear-physics\/fundamental-particles\/neutron\/interactions-neutrons-matter\/\"><strong>Neutrons<\/strong><\/a>. Since the neutrons are <strong>electrically neutral particles,<\/strong> they are mainly subject to <a href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/atomic-nuclear-physics\/fundamental-interactions-fundamental-forces\/strong-interaction-strong-force\/\">strong nuclear forces<\/a> but not electric ones. Therefore, neutrons are <strong>not directly ionizing<\/strong>\u00a0and usually have to be <strong>converted<\/strong> into charged particles before they can be detected. Generally, every type of neutron detector must be equipped with a converter (to convert neutron radiation to common detectable radiation) and one of the conventional radiation detectors (scintillation detector, ga搜索引擎优化us detector, semiconductor detector, etc.). <a href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/atomic-nuclear-physics\/fundamental-particles\/neutron\/fast-neutrons-high-energy-neutrons\/\">Fast neutrons<\/a> (&gt;0.5 MeV) primarily rely on the recoil proton in (n,p) reactions. Materials rich in hydrogen, such as <strong>plastic scintillators<\/strong>, are best suited for their detection. <a href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/atomic-nuclear-physics\/fundamental-particles\/neutron\/thermal-neutron\/\">Thermal neutrons<\/a> rely on nuclear reactions such as the (n,\u03b3) or (n,\u03b1) reactions to produce ionization. Materials such as LiI(Eu) or glass silicates are therefore particularly well-suited for detecting thermal neutrons.<\/li>\n<\/ul>\n<h2>Gamma Spectroscopy using Scintillation Counter<\/h2>\n<p>See also: <a href=\"http:\/\/sitepourvtc.com\/nuclear-engineering\/radiation-detection\/gamma-spectroscopy\/spectroscopy-using-scintillation-counter\/\">Gamma Spectroscopy using Scintillation Counter<\/a><\/p>\n<p>See also: <a href=\"http:\/\/sitepourvtc.com\/nuclear-engineering\/radiation-detection\/gamma-spectroscopy\/\">Gamma Spectroscopy<\/a><\/p>\n<p><strong>Gamma spectroscopy<\/strong> generally studies the energy spectra of gamma-ray sources, such as in the nuclear industry, geochemical investigation, and astrophysics. Spectroscopes, or spectrometers, are sophisticated devices designed to measure the spectral power distribution of a source. The incident radiation generates a signal that determines the incident particle&#8217;s energy.<\/p>\n<figure id=\"attachment_26113\" aria-describedby=\"caption-attachment-26113\" style=\"width: 290px\" class=\"wp-caption alignright\"><a href=\"http:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/02\/HPGe-Detector-spectrum.png\"><img loading=\"lazy\" class=\"size-medium wp-image-26113\" src=\"http:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/02\/HPGe-Detector-spectrum-300x250.png\" alt=\"HPGe Detector spectrum\" width=\"300\" height=\"250\" srcset=\"https:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/02\/HPGe-Detector-spectrum-300x250.png 300w, https:\/\/sitepourvtc.com\/wp-content\/uploads\/2019\/02\/HPGe-Detector-spectrum.png 514w\" sizes=\"(max-width: 300px) 100vw, 300px\" \/><\/a><figcaption id=\"caption-attachment-26113\" class=\"wp-caption-text\">Figure: Caption: Comparison of NaI(Tl) and HPGe spectra for cobalt-60. Source: Radioisotopes and Radiation Methodology I, II. Soo Hyun Byun, Lecture Notes. McMaster University, Canada.<\/figcaption><\/figure>\n<p>Most <a href=\"http:\/\/sitepourvtc.com\/nuclear-engineering\/radiation-protection\/sources-of-radiation\/\">radioactive sources<\/a> produce <a href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/atomic-nuclear-physics\/fundamental-particles\/photon\/gamma-ray\/\">gamma rays<\/a>\u00a0of various energies and intensities. Gamma rays frequently <strong>accompany the emission<\/strong>\u00a0of\u00a0<a title=\"Alpha Particle\" href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/atomic-nuclear-physics\/fundamental-particles\/alpha-particle\/\">alpha\u00a0<\/a>and\u00a0<a title=\"Beta Particle\" href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/atomic-nuclear-physics\/fundamental-particles\/beta-particle\/\">beta radiation<\/a>. <strong>Gamma-ray\u00a0spectrum <\/strong><strong>energy <\/strong>can be produced when these emissions are detected and analyzed with a spectroscopy system. <strong>Gamma rays<\/strong> from <a href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/atomic-nuclear-physics\/radioactive-decay\/\">radioactive decay<\/a> are in the energy range from a few keV to ~8 MeV, corresponding to the typical energy levels in nuclei with reasonably long lifetimes. As was written, they are produced by the decay of nuclei as they transition from a high energy state to a lower state. A detailed spectrum analysis is typically used to determine the <strong>identity<\/strong> and <strong>quantity<\/strong> of gamma emitters present in a sample. It is a vital tool in the radiometric assay. The gamma spectrum is characteristic of the gamma-emitting nuclides contained in the source.<\/p>\n<\/div><\/div>\n<div   id="8n9s8rpp6h"     class=\"lgc-column lgc-grid-parent lgc-grid-100 lgc-tablet-grid-100 lgc-mobile-grid-100 lgc-equal-heights \"><div   id="8n9s8rpp6h"     class=\"inside-grid-column\"><div   id="8n9s8rpp6h"    class=\"su-spoiler su-spoiler-style-default su-spoiler-icon-plus su-spoiler-closed\" data-scroll-offset=\"0\"><div   id="8n9s8rpp6h"    class=\"su-spoiler-title\" tabindex=\"0\" role=\"button\"><span class=\"su-spoiler-icon\"><\/span>References:<\/div><div   id="8n9s8rpp6h"    class=\"su-spoiler-content su-u-clearfix su-u-trim\">\n<p><strong>Radiation Protection:<\/strong><\/p>\n<ol>\n<li>Knoll, Glenn F., Radiation Detection and Measurement 4th Edition, Wiley, 8\/2010. ISBN-13: 978-0470131480.<\/li>\n<li>Stabin, Michael G., Radiation Protection and Dosimetry: An Introduction to Health Physics, Springer, 10\/2010. ISBN-13: 978-1441923912.<\/li>\n<li>Martin, James E., Physics for Radiation Protection 3rd Edition, Wiley-VCH, 4\/2013. ISBN-13: 978-3527411764.<\/li>\n<li>U.S.NRC, NUCLEAR REACTOR CONCEPTS<\/li>\n<li>U.S. Department of Energy, Instrumentation and Control. DOE Fundamentals Handbook, Volume 2 of 2. June 1992.<\/li>\n<\/ol>\n<p><strong>Nuclear and Reactor Physics:<\/strong><\/p>\n<ol>\n<li>J. R. Lamarsh, Introduction to Nuclear Reactor Theory, 2nd ed., Addison-Wesley, Reading, MA (1983).<\/li>\n<li>J. R. Lamarsh, A. J. Baratta, Introduction to Nuclear Engineering, 3d ed., Prentice-Hall, 2001, ISBN: 0-201-82498-1.<\/li>\n<li>W. M. Stacey, Nuclear Reactor Physics, John Wiley &amp; Sons, 2001, ISBN: 0- 471-39127-1.<\/li>\n<li>Glasstone, Sesonske. Nuclear Reactor Engineering: Reactor Systems Engineering, Springer; 4th edition, 1994, ISBN: 978-0412985317<\/li>\n<li>W.S.C. Williams. Nuclear and Particle Physics. Clarendon Press; 1 edition, 1991, ISBN: 978-0198520467<\/li>\n<li>G.R.Keepin. Physics of Nuclear Kinetics. Addison-Wesley Pub. Co; 1st edition, 1965<\/li>\n<li>Robert Reed Burn, Introduction to Nuclear Reactor Operation, 1988.<\/li>\n<li>U.S. Department of Energy, Nuclear Physics and Reactor Theory. DOE Fundamentals Handbook, Volume 1 and 2. January 1993.<\/li>\n<li>Paul Reuss, Neutron Physics. EDP Sciences, 2008. ISBN: 978-2759800414.<\/li>\n<\/ol>\n<\/div><\/div><div   id="8n9s8rpp6h"    class=\"su-divider su-divider-style-dotted\" style=\"margin:15px 0;border-width:2px;border-color:#999999\"><\/div><\/div><\/div><div   id="8n9s8rpp6h"     class=\"lgc-column lgc-grid-parent lgc-grid-33 lgc-tablet-grid-33 lgc-mobile-grid-100 lgc-equal-heights \"><div   id="8n9s8rpp6h"     class=\"inside-grid-column\"><\/div><\/div><div   id="8n9s8rpp6h"     class=\"lgc-column lgc-grid-parent lgc-grid-33 lgc-tablet-grid-33 lgc-mobile-grid-100 lgc-equal-heights \"><div   id="8n9s8rpp6h"     class=\"inside-grid-column\">\n<h2>See above:<\/h2>\n<p>Detection<a href=\"http:\/\/sitepourvtc.com\/nuclear-engineering\/radiation-detection\/\" class=\"su-button su-button-style-flat\" style=\"color:#606060;background-color:#ffffff;border-color:#cccccc;border-radius:10px;-moz-border-radius:10px;-webkit-border-radius:10px\" target=\"_self\"><span style=\"color:#606060;padding:7px 20px;font-size:16px;line-height:24px;border-color:#ffffff;border-radius:10px;-moz-border-radius:10px;-webkit-border-radius:10px;text-shadow:0px 0px 0px #000000;-moz-text-shadow:0px 0px 0px #000000;-webkit-text-shadow:0px 0px 0px #000000\"><i class=\"sui sui-link\" style=\"font-size:16px;color:#5d5d5d\"><\/i> <\/span><\/a><\/p><\/div><\/div><div   id="8n9s8rpp6h"     class=\"lgc-column lgc-grid-parent lgc-grid-33 lgc-tablet-grid-33 lgc-mobile-grid-100 lgc-equal-heights \"><div   id="8n9s8rpp6h"     class=\"inside-grid-column\"><\/div><\/div>\n","protected":false},"excerpt":{"rendered":"","protected":false},"author":1,"featured_media":0,"parent":26089,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"generate_page_header":""},"_links":{"self":[{"href":"https:\/\/sitepourvtc.com\/wp-json\/wp\/v2\/pages\/26285"}],"collection":[{"href":"https:\/\/sitepourvtc.com\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/sitepourvtc.com\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/sitepourvtc.com\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/sitepourvtc.com\/wp-json\/wp\/v2\/comments?post=26285"}],"version-history":[{"count":2,"href":"https:\/\/sitepourvtc.com\/wp-json\/wp\/v2\/pages\/26285\/revisions"}],"predecessor-version":[{"id":38174,"href":"https:\/\/sitepourvtc.com\/wp-json\/wp\/v2\/pages\/26285\/revisions\/38174"}],"up":[{"embeddable":true,"href":"https:\/\/sitepourvtc.com\/wp-json\/wp\/v2\/pages\/26089"}],"wp:attachment":[{"href":"https:\/\/sitepourvtc.com\/wp-json\/wp\/v2\/media?parent=26285"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}