Geiger detector, counting rate

Intensity measurements are simplified when a detector always gives one electrical pulse for each x-ray quantum absorbed the detector remains linear so long as this is true. For low intensities, when the rates of incidence upon the detector are low, the Geiger counter fulfills this condition. As this rate increases above (about) 500 counts per second, the number of pulses per second decreases progressively below the number of quanta absorbed per second. This decrease occurs even with electronic circuits that can handle higher counting rates without appreciable losses. 

The cause of this difficulty therefore resides within the counter itself. The difficulty is described by saying that the Geiger counter has a dead time, by which is meant the time interval after a pulse during which the counter cannot respond to a later pulse. This interval, which is usually well below 0.5 millisecond, limits the useful maximum counting rate of the detector. The cause of the dead time is the slowness with which the positive-ion space charge (2.5) leaves the central wire under the influence of the electric field. This reduction in observed counting rate is known as the coincidence loss. 

A sample of a particular radioisotope is placed near a Geiger counter, which is observed to register 160 counts per minute. Eight hours later, the detector counts at a rate of 10 counts per minute. What is the half-life of the material ... 

Finally, the influence of the dead time D in eq. (7.3)) has to be taken into account, particularly if the dead time of the detector is high (as in the case of Geiger Muller counters) and if the counting rates of the sample and the calibration source are markedly different. 

Geiger Flow-proportional Proportional Scintillation Routine control analysis where low counting rates and physical discrimination are adequate. Determination of all elements of atomic number 24 or below. Unique applications where the maximum resolution of a detector is required. Determination of all elements of atomic number 25 and above. 

Material around the source and detector, notably the detector housing, cause scattering into the detector. The opportunity for scattering into the detector increases when the source is more distant. This scattering adds a few percent to the count rate for end-window Geiger-Mueller (G-M) detectors when the sample is 2 cm or more distant (Zumwalt 1950), but little for gas-flow proportional counters with the sample only about 0.3 cm from a relatively large window. Scattering, attenuation. 

Counting rates measured with Geiger-Miiller, scintillation, or semiconductor detectors are usually compared with suitable standards to obtain quantitative data. Pulse analyzers (either single or multichannel), when coupled to a suitable radiation detector, can yield qualitative as well as quantitative data about individual components of the sample. 

After irradiation, the sample is removed and its activity measured with a suitable detector, such as a Geiger or scintillation counter. If the efficiency of the detector (counts recorded per disintegration in the foil) is s, the count rate immediately after the foil is removed from the reactor will be obtained by multiplying e by the activity of the foil, AiV. Then... 

Emanation thermal analysis is usually carried out in conjunction with other TA techniques, most notably DTA and EGA. In this context, ETA can be considered as a coupled TA technique. Carrier gas at a constant flow rate is used to carry the released gas from the sample to appropriate detectors—usually radioactive counting devices. In the case of desorbed radon, a scintillation counter is used, whereas Geiger counters are used for krypton, xenon, and argon. 

A rate meter generates a time-averaged number of pulses obtained from the signal amplifier. Rate meters are normally used in portable radiation dose rate monitors with a Geiger-Muller counter or a scintillation detector. A sealer is a device counting the number of pulses in a selected time. 

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