Nuclear Instrumentation - Measurement of Gamma-Ray Emission Rates of Radionuclides - Calibration and Use of Germanium Spectrometers
|Publication Date:||1 August 1995|
|ICS Code (Radiation measurements):||17.240|
Scope and object
This standard establishes methods for the calibration and use of germanium spectrometers for the measurement of gamma-ray energies and emission rates over the energy range from 59 keV to approximately 3 000 keV and the calculation of source activities from these measurements. Minimum requirements for automated peak finding are stated. This standard establishes methods for measuring the full-energy peak efficiency with calibrated sources.
Performance tests are described that ascertain if the Ge spectrometer is functioning within acceptable limits. These tests evaluate the limitations of the algorithms used for locating and fitting single and multiplet peaks. Methods for the measurement of and the correction for pulse pile-up are suggested. A test to ascertain the approximate magnitude of cascade summing is described. Techniques are recommended for the inspection of spectralanalysis results for large errors resulting from summing of cascade gamma rays in the detector. Suggestions are provided for the establishment of data libraries for radionuclide identification, decay corrections and the conversion of gamma-ray emission rates to decay rates.
The measurement of X-ray emission rates is not included because different functional fits are required for X-ray peaks, which have intrinsically different peak shapes than gammaray peaks. Further, X-ray peaks are complex multiplets (e.g. the K X-rays of TI are composed of eight components that form four partially resolved individual peaks). This standard does not address the measurement of emission rates of annihilation radiation peaks or single- and double-escape peaks resulting from partial energy deposition in the detector from pair production. Escape peaks may require different fitting functions than comparable full-energy peaks. Further, annihilation radiation and single-escape peaks have a different and larger width than a corresponding gamma-ray energy. Discussion of acceptable methods for measuring the lower limits of detection as they relate to specific radionuclides is beyond the scope of this standard.
The object of this standard is to provide a basis for the routine calibration and use of germanium (Ge) semiconductor detectors for the measurement of gamma-ray emission rates and thereby the activities of the radionuclides in a sample. It is intended for use by persons who have an understanding of the principles of Ge gamma-ray spectrometry and are responsible for the development of correct procedures for the calibration and use of such detectors. This standard is primarily intended for routine analytical measurements. A related document is IEC 973.