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1、The Institute of Electrical and Electronics Engineers, Inc. 345 East 47th Street, New York, NY 10017-2394, USA Copyright 1999 by the Institute of Electrical and Electronics Engineers, Inc. All rights reserved. Published 1 June 1999. Printed in the United States of America. Print: ISBN 0-7381-1412-X
2、SH94702 PDF: ISBN 0-7381-0740-9 SS94702 No part of this publication may be reproduced in any form, in an electronic retrieval system or otherwise, without the prior written permission of the publisher. ANSI N42.14-1999 (R2004) (Revision of ANSI N42.14-1991) American National Standard for Calibration
3、 and Use of Germanium Spectrometers for the Measurement of Gamma-Ray Emission Rates of Radionuclides Sponsor Accredited Standards Committee on Radiation Instrumentation, N42 Accredited by the American National Standards Institute Secretariat The Institute of Electrical and Electronics Engineers, Inc
4、. Reaffirmed December 2, 2004 American National Standards Institute Abstract: 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 3000 keV, and for the calculation of source act
5、ivities from these measurements, are established. Minimum requirements for automated peak finding are stated. Methods for measuring the full- energy peak efficiency with calibrated sources are given. Performance tests that ascertain the prop- er functioning of the Ge spectrometer and evaluate the li
6、mitations of the algorithms used for locating and fitting single and multiple peaks are described. Methods for the measurement of, and the correction for pulse pileup are suggested. Techniques are recommended for the inspection of spec- tral-analysis results for large errors resulting from summing o
7、f cascade gamma rays in the detector. Suggestions are provided for the establishment of data libraries for radionuclide identification, de- cay corrections, and the conversion of gamma-ray rates to decay rates. Keywords: calibration, cascade summing, decay rates, gamma-ray emission rates, germanium
8、spectrometers, radionuclides, spectrometers Copyright The Institute of Electrical and Electronics Engineers, Inc. Provided by IHS under license with IEEELicensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/21/2007 11:57:46 MDTNo reproduction or networking permitted without license from
9、IHS -,-,- American National Standard An American National Standard implies a consensus of those substantially concerned with its scope and provisions. An American National Standard is intended as a guide to aid the manufacturer, the consumer, and the general public. The existence of an American Nati
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15、sale, 04/21/2007 11:57:46 MDTNo reproduction or networking permitted without license from IHS -,-,- Copyright 1999 IEEE. All rights reserved. iii Introduction (This introduction is not part of ANSI N42.14-1999, American National Standard for Calibration and Use of Germanium Spectrometers for the Mea
16、surement of Gamma-Ray Emission Rates of Radionuclides.) This standard covers the techniques for the calibration and use of germanium spectrometers for the measure- ment of gamma-ray emission rates of radionuclides to assure the reliability of such measurements. This standard is the responsibility of
17、 the Accredited Standards Committee N42 on Radiation Instrumenta- tion. Committee N42 delegated the development of the standard to its Subcommittee N42.RM. Drafts were reviewed by members of Committee N42, Subcommittee N42.RM, and other interested parties, and the comments received were utilized in
18、producing the standard as fi nally approved and issued. The standard was approved by Committee N42 letter ballot of 17 December 1997. Participants At the time it approved this standard, the Accredited Standards Committee on Radiation Instrumentation, N42, had the following members: Louis Costrell, C
19、hair Michael P. Unterweger, Vice Chair Naeem Ahmad, Secretariat Organization RepresentedName of Representative American Conference of Governmental Industrial Hygienists.Jesse Lieberman Applied Safety Technology.Edward J. Vallario* Battelle Pacifi c NW Laboratories .Joseph C. McDonald BicronJoseph G.
20、 Bellian Eberline Instruments.James K. Hesch EG b)Coincidence (cascade) summing; c) The decay of the source during sampling (e.g., with air fi lters) and counting; d)The decay of the source from a previous time to the counting period; e)Attenuation of photons within and external to the source that i
21、s not accounted for by the full-energy peak effi ciency calibration. 2. References This standard shall be used in conjunction with the following publications. When the following standards are superseded by an approved revision, the revision shall apply. ANSI N13.30-1996, American National Standard P
22、erformance Criteria for Radiobioassay. 3 ANSI N42.23-1996, American National Standard Measurement and Associated Instrument Quality Assur- ance for Radioassay Laboratories. 4 IEEE Std 100-1996, IEEE Standard Dictionary of Electrical and Electronics Terms. 5 IEEE Std 325-1996, IEEE Standard Test Proc
23、edures for Germanium Gamma-Ray Detectors. 3 ANSI publications are available from the Sales Department, American National Standards Institute, 11 West 42nd Street, 13th Floor, New York, NY 10036, USA (www.ansi.org/). 4 This publication is available from the Institute of Electrical and Electronics Eng
24、ineers, 445 Hoes Lane, P.O. Box 1331, Piscataway, NJ 08855-1331, USA (www.standards.ieee.org/). 5 IEEE publications are available from the Institute of Electrical and Electronics Engineers, 445 Hoes Lane, P.O. Box 1331, Piscataway, NJ 08855-1331, USA (www.standards.ieee.org/). Copyright The Institut
25、e of Electrical and Electronics Engineers, Inc. Provided by IHS under license with IEEELicensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/21/2007 11:57:46 MDTNo reproduction or networking permitted without license from IHS -,-,- ANSI FOR THE MEASUREMENT OF GAMMA-RAY EMISSION RATES OF
26、RADIONUCLIDESStd N42.14-1999 Copyright 1999 IEEE. All rights reserved. 3 3. Defi nitions The word “shall” denotes a requirement, the word “should” denotes a recommendation, and the word “may” denotes permission. To conform to this standard, Ge spectrometry shall be performed in accordance with the r
27、equirements of this standard, but not necessarily with its recommendations; however, justifi cation should be documented for deviations from a recommendation. For the purposes of this standard, the following terms and defi nitions apply. IEEE Std 100-1996 should be referenced for terms not defi ned
28、in this clause. 3.1 abundance: See: emission probability per decay P ( E ) or P ( E ). 3.2 activity (A): The expected number of spontaneous nuclear decays (transformations) in unit time from a specifi ed energy state (excluding prompt decays from a lower nuclear level) for a given amount of a radion
29、u- clide. Its standard unit (SI) is the becquerel (Bq), where one Bq equals one decay per second. Activity has often been expressed in curies (Ci), where 3.7 10 10 Bq equals 1 Ci, exactly. 3.3 ADC conversion gain: The number of channels over which the full amplitude span can be spread; usu- ally 204
30、88192 channels are used for Ge gamma-ray spectrometry. 3.4 analog-to-digital converter (ADC): An electronic device used to convert the amplitude of a voltage pulse from analog to digital format. 3.5 attenuation: The net loss at the detector of primary photons of a given energy resulting from their i
31、nter- action with matter either due to the occurrence of scattering or absorption in the sample or in material between the sample and the detector crystal. 3.6 background: Spectral data including peaks not caused by the source but rather resulting from radioac- tive decay occurring in the surroundin
32、g environment or resulting from cosmic-ray interactions in or adjacent to the detector. See also: continuum. 3.7 baseline: See: continuum. 3.8 calibration: The determination of a value that converts a measured number into a desired physical quan- tity (e.g., pulse height into photon energy, or count
33、s per second into emission rate). 3.9 cascade summing: See: coincidence summing of x and gamma rays. 3.10 cascade transitions: Gamma rays in the radioactive decay of a single atom that are emitted sequen- tially and within the resolving time of the spectrometer. 3.11 coincidence summing of x and gam
34、ma rays: The simultaneous detection of two or more photons originating from a single nuclear disintegration that results in only one observed (summed) pulse. Syn: cas- cade summing; true coincidence summing. 3.12 combined uncertainty: The uncertainty resulting from combining category A and category
35、B uncer- tainties, as defi ned by the Bureau International des Poids et Mesures (BIPM), using standard statistical methods. Category A uncertainties are evaluated by applying statistical methods to a series of repeated mea- surements and are characterized by the estimated standard deviation, s A ; c
36、ategory B uncertainties are assigned to quantities whose variation is not explicitly observed. Category B uncertainties are determined by estimating from other information an approximation to a corresponding “standard deviation,” s B , whose existence is assumed. They are combined as if they are all
37、 standard deviations. Copyright The Institute of Electrical and Electronics Engineers, Inc. Provided by IHS under license with IEEELicensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/21/2007 11:57:46 MDTNo reproduction or networking permitted without license from IHS -,-,- ANSI Std N42
38、.14-1999AMERICAN NATIONAL STANDARD CALIBRATION AND USE OF GERMANIUM SPECTROMETERS 4 Copyright 1999 IEEE. All rights reserved. 3.13 continuum: The part of the pulse-height distribution lying underneath a peak, including contributions associated with the source, detector, and measuring conditions that
39、 affect the spectral shape. Syn: baseline. 3.14 counting rate: The rate at which detector pulses are being registered in a selected voltage interval. The unit is reciprocal seconds (i.e., s -1 ). 3.15 crossover transition: A gamma ray occurring between two nonadjacent nuclear levels. 3.16 dead time:
40、 The time during which the ADC is unable to process input pulses because it is processing a previous pulse. 3.17 detection effi ciency: The ratio between the number of selected pulses recorded per unit time to the number of photons emitted by the source per unit time. See also: full-energy peak effi
41、 ciency; total effi ciency. 3.18 direct current (dc) level: The input or output voltage level on a dc-coupled instrument when there are no pulses present. For Ge spectrometer systems, the dc level of an output signal from a linear amplifi er should be matched to the input requirements for dc levels
42、of an ADC if the gain conversion scale is to include the origin. 3.19 elapsed time ( T r ): Counting time uncompensated for periods in which an instrument might be unable to respond. Elapsed time of a count equals live time plus dead time. 3.20 emission probability per decay P ( E ) or P ( E ): The
43、probability that a radioactive decay will be fol- lowed by the emission of the specifi ed radiation. Gamma-ray emission probabilities are often expressed per 100 decays. Syn: yield; abundance. 3.21 energy resolution, full width at half maximum (FWHM): The width of a peak at half of the maxi- mum pea
44、k height with the baseline removed. 3.22 energy resolution, full width at tenth maximum (FWTM): The width of a peak at one-tenth of the maximum peak height with the baseline removed. For a normal (Gaussian) distribution, FWTM is 1.823 times its FWHM. 3.23 full-energy peak: A peak in the spectrum res
45、ulting from the complete (total) absorption of a photon of a given energy in the active volume of the Ge crystal and the collection of all of the resulting charge. Syn: photopeak. 3.24 full-energy peak effi ciency ( E ): The ratio between the number of counts in the net area of the full- energy peak
46、 to the number of photons of that energy emitted by a source with specifi ed characteristics for a specifi ed source-to-detector distance. 3.25 gamma-ray branching ratio f ( E ): For a given excited state, the ratio of the emission rate of a partic- ular gamma ray to the total transition rate from t
47、he level (not to be confused with emission probability per decay). 3.26 gamma-ray emission rate R ( E ): The rate at which a gamma ray of a given energy from the decay of a particular radionuclide is emitted from a given source. The gamma-ray emission rate is the activity times the gamma-ray emissio
48、n probability. 3.27 live time ( T L ): The time interval of a count during which a counting system is capable of processing input pulses. Elapsed (or real) time equals live time plus dead time. Copyright The Institute of Electrical and Electronics Engineers, Inc. Provided by IHS under license with I
49、EEELicensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/21/2007 11:57:46 MDTNo reproduction or networking permitted without license from IHS -,-,- ANSI FOR THE MEASUREMENT OF GAMMA-RAY EMISSION RATES OF RADIONUCLIDESStd N42.14-1999 Copyright 1999 IEEE. All rights reserved. 5 3.28 Monte Carlo: A modeling technique in which the int