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201:(NaI and BGO are the most common) The suppression detector is shielded from the source by a thick collimator, and it is operated in anti-coincidence with the main detector: if they both detect a gamma ray, it must have scattered out of the main detector before depositing all of its energy, so the Ge reading is ignored. The cross section for interaction of gamma rays in the suppression detector is larger than that of the main detector, as is its size, thus it is highly unlikely that a gamma ray will escape both devices.
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The high-purity solid state germanium (HPGe) detectors used in gamma-ray spectroscopy have a typical size of a few centimeters in diameter and a thickness ranging from a few centimeters to a few millimeters. For detectors of such a size, gamma rays may
Compton scatter out of the detector's volume
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scintillator almost completely surrounded by a thick CsI anticoincidence shield, with a hole or holes to allow the desired gamma rays to enter from the cosmic source under study. A plastic scintillator may be used across the front which is reasonably transparent to gamma rays, but efficiently
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Modern experiments in nuclear and high-energy particle physics almost invariably use fast anticoincidence circuits to veto unwanted events. The desired events are typically accompanied by unwanted background processes that must be suppressed by enormous factors, ranging from thousands to many
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before they deposit their entire energy. In this case, the energy reading by the data acquisition system will come up short: the detector records an energy which is only a fraction of the energy of the incident gamma ray.
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around the X-ray/gamma-ray detector, also of CsI(Tl), with the two connected in electronic anticoincidence to reject unwanted charged particle events and to provide the required angular collimation.
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or other such elements, but it was quickly discovered that the high fluxes of very penetrating high-energy radiation present in the near-space environment created
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to intercept the unwanted background events, producing essentially simultaneous pulses that can be used with fast electronics to reject the unwanted background.
214:, where the enormous Atlas and CMS detectors must reject huge numbers of background events at very high rates, to isolate the very rare events being sought.
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In order to counteract this, the expensive and small high resolution detector is surrounded by larger and cheaper low resolution detectors, usually a
153:("BGO"), or other active shielding materials are used to detect and veto gamma-ray events of non-cosmic origin. A typical configuration might have a
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were often surrounded by an active anticoincidence shield made of some other detector, which could be used to reject the unwanted background events.
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Drawing of an active anticoincidence collimated scintillation spectrometer designed for gamma-ray astronomy in the energy range from 0.1 to 3 MeV.
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billions, to permit the desired signals to be detected and studied. Extreme examples of these kinds of experiments may be found at the
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Proc. 8th
Scintillation Counter Symposium, Washington, DC, 1–3 March 1962. IRE Trans. Nucl. Sci., NS-9, No. 3, pp. 381-385 (1962)
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out of the detector before depositing all of its energy. The goal is to minimize the background related to the
Compton effect (
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that could not be stopped by reasonable shielding masses. To solve this problem, detectors operating above 10 or 100
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is a method (and its associated hardware) widely used to suppress unwanted, "background" events in
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is a technique that improves the signal by removing data that have been corrupted by the incident
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E. Segrè. Nuclei and
Particles. New York: W. A. Benjamin, 1964 (2nd ed., 1977).
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E. Segrè (ed.). Experimental
Nuclear Physics, 3 vols. New York: Wiley, 1953-59.
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scintillators are often used to reject charged particles, while thicker CsI,
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by surrounding the detectors with heavy shielding materials made of
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charged-particle events. Gamma-rays, in particular, could be
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Method of eliminating background events in particle physics
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In the typical case, a desired high-energy interaction or
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Detector for Low Energy Gamma-ray
Astronomy Experiment,
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An early example of such a system, first proposed by
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305:"Applitcaion note: Compton suppression spectrometry"
135:in 1962, is shown in the figure. It has an active
92:found that their detectors, flown on balloons or
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270:. Annual Review of Astronomy and Astrophysics
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268:Instrumental Technique in X-Ray Astronomy
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158:rejects the high fluxes of cosmic-ray
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336:Radiation Detection and Measurement
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338:2000. John Wiley & Sons, Inc.
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114:showers of secondary particles
96:, were corrupted by the large
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285:K. J. Frost and E. D. Rothe,
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205:Nuclear and particle physics
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100:of high-energy photon and
31:Electronic anticoincidence
53:, and related fields.
84:Early experimenters in
266:Laurence E. Peterson,
249:Gamma-ray spectroscopy
172:gamma-ray spectroscopy
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43:gamma-ray spectroscopy
212:Large Hadron Collider
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141:scintillation shield
370:Compton Suppression
224:Nuclear electronics
176:Compton suppression
166:Compton suppression
90:gamma-ray astronomy
80:Gamma-ray astronomy
66:nuclear electronics
47:gamma-ray astronomy
35:high energy physics
18:Compton suppression
162:present in space.
133:Kenneth John Frost
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74:particle detectors
244:Uhuru (satellite)
188:Compton continuum
184:Compton scattered
151:bismuth germanate
16:(Redirected from
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334:Knoll, Glenn F.
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255:References
106:collimated
102:cosmic-ray
317:8 January
180:gamma ray
380:Category
239:INTEGRAL
218:See also
182:getting
62:detector
160:protons
147:Plastic
234:HEAO 3
229:HEAO 1
98:fluxes
70:photon
308:(PDF)
139:(Tl)
86:X-ray
58:event
319:2024
110:lead
88:and
170:In
155:NaI
137:CsI
118:keV
72:or
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327:^
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294:^
272:13
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