Anticoincidence circuits

Radiometric analysis using a plastic scintillator connected to coincidence and anticoincidence circuits (e.g. a Picobeta counter) can be used to detect "Tc. The detection limit is estimated to be about 10 mBq. A slightly better detection limit (1-5 mBq) is reported for a gas flow counter with an anticoincidence shield [8],... 

In a cryogenic experiment, one or several detectors are used for a definite goal for which they have been optimized. For example, in CUORE experiment described in Section 16.5, the sensors are the Ge thermistors, i.e. thermometers used in a small temperature range (around 10 mK). One detector is a bolometer made up of an absorber and a Ge sensor. The experiment is the array of 1000 bolometers arranged in anticoincidence circuits for the detection of the neutrinoless double-beta decay. Note that the sensors, if calibrated, could be used, as well, as very low-temperature thermometers. Also the array of bolometers can be considered a single large detector and used for different purposes as the detection of solar axions or dark matter. 

Gas ionization, solid scintillation, liquid scintillation and semiconductor detectors, autoradiography. Single and multichannel pulse height analysers. Coincidence and anticoincidence circuits. 

On the other hand, by application of an anticoincidence circuit only those events are recorded that are not in coincidence with others. 

An application of anticoincidence circuits is the anti-Compton spectrometer. The Compton continuum in y spectra can be reduced relative to the photopeaks by placing the Ge detector inside a second detector, usually a scintillation detector, connected in anticoincidence, so that only pulses in the central detector that are not coincident with those in the outer detector are recorded. Anti-Compton spectrometers are very useful for measurement of y rays of very high energy. 

If samples of very low activity are to be measured, the contribution of the background to the counting rate and hence the error of the measurement are relatively high. The influence of the background can be reduced by intensiflcation of the detector shielding and by coincidence or anticoincidence circuits. 

By coincidence or anticoincidence methods the background of a detector may by decreased by a factor of about 100 or more. The application of an anticoincidence circuit is the same as in an anti-Compton spectrometer. 

Counter combinations with anticoincidence circuit (measuring counter surrounded by a ring of protective counters which lower the zero effect). 

Large-area counters with anticoincidence circuit and appropriate lead screening, combined with a suitable measuring and evaluation unit, are frequently selected as detectors in water analysis. 

Geiger counters, and in the range of 1 pulse/min. for Geiger counters in the form of end-window counters with anticoincidence circuit. The zero... 

The efficiency of Geiger counters is approximately 10 %, and for those with anticoincidence circuit it can be estimated at 20 %. 

Methane flow counters have an efficiency of around 50 %, on account of the positive geometry of the measuring unit. The zero effect in flow counters is in the region of 20 pulses/min., but this counter equipment can nevertheless compete successfully with an anticoincidence circuit as a result of its high efficiency. 

ANTICOINCIDENCE CIRCUIT A circuit with two inputs. An output signal is blocked and does NOT appear if both inputs receive a pulse within a certain small time interval of each other. Often used in a gating circuit where a logic pulse triggers rejection of a linear pulse. 

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