IEEE N42.25-1997 pdf download American National Standard Calibration and Usage of AlphdBeta Proportional Counters
1.1 Scope
This standard establishes methods for the calibration and use of gas proportional counters with and without active guard detectors. This standard also establishes methods for measuring the alpha and beta counting plateau, crosstalk factors, background, alpha and beta efficiency from prepared standards, correction factors for samples whose self-attenuation or mass differs from that of the standard, and calculation of the sample activities together with their random and total uncertainties. Correction for pulse pileup due to high count rate is also discussed. Although many principles articulated in this standard apply to the counting of radionuclides emitting a maximum beta energy below 100 keV as well, the counting of these low-energy beta emitters requires a higher degree of attention to detail in sample preparation, instrument calibration, and measurement correction factors than addressed in this standard. Therefore, this standard is intended for measuring radionuclides with maximum beta energies above 100 keV.
1.2 Special word usage
The word shal! denotes a requirement, the word should denotes a recommendation, and the word madenotes permission. To conform to this standard, gas proportional counting shall be performed in accordancewith the requirements of this standard, but not necessarily with its recommendations. However, justifcationshould be documented for deviations from a recommendation.
2. References
ANSI N42.14-1991 American National Standard Calibration and Use of Germanium Spectrometers for theMeasurement of Gamma-Ray Emission Rates of Radionuclides.-
ANSI N42.22-1995,American National Standard Traceability of Radioactive Sources to the NationalInstitute of Standards and Technology (NIST) and Associated Instrument Quality Control.
ANSI N42.23-1996,American National Standard Measurement and Associated Instrumentation OualityAssurance for Radioassay Laboratories.
3. Definitions
3.1 Glossary
3.1.1 active guard detector: A detector constructed from similar materials with similar geometry to themain sample counting detector This detector is mounted in proximity to the sample counting detector inorder to intercept and react to the same background cosmic and terrestrial radiation field as the sampledetector. Normally this detector is used-in an anti-coincidence mode to cancel out the effect of thisbackground radiation field on the sample detector in order to produce a real-time adjusted net count rate forthe sample detector.
3.1.2 activity: The expected number of spontaneous nuclear decays (transformations) in unit time from aspecifed energy state (excluding prompt decays from a lower nuclear level) for a given amount of aradionuclide. Its standard unit (SI) is the becquerel (Bq), where one Bq equals one decay per second.Activity is often also expressed in curies, where 3,7×101% Bq equals one Ci exactly or in disintegrations perminute (dpm), where 1 dpm equals 1/60 Bq exactly.u
3.1.3 alpha emission rate: The rate at which alpha particles of all energies are emitted from one or allalpha-emitting radionuclides present in a source or sample.
3.1.4 alpha surface emission rate: The rate at which alpha particles of all energies emanate from thesurface of a source or sample that contains one or more alpha-emitting radionuclides.
3.1.5 attenuation: The net loss of radiation field from the sample resulting from scattering or absorption inthe sample or in material between the sample and the active volume of the counting chamber
3.1.6 background count rate: Events per unit time from radioactive decay not caused by a calibrationsource or sample but rather from that occurring in the surrounding environment or from cosmic-rayinteractions in or adjacent to the detector that have escaped detection by the guard detector, when present
IEEE N42.25-1997 pdf download
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