1、The Institute of Electrical and Electronics Engineers, Inc.345 East 47th Street, New York, NY 10017-2394, USACopyright 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 SH94
2、702PDF: ISBN 0-7381-0740-9 SS94702No 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 ofANSI N42.14-1991)American National Standard forCalibration and Use of
3、 Germanium Spectrometers for the Measurement of Gamma-Ray Emission Rates of RadionuclidesSponsorAccredited Standards Committee on Radiation Instrumentation, N42Accredited by theAmerican National Standards InstituteSecretariatThe Institute of Electrical and Electronics Engineers, Inc.Reaffirmed Decem
4、ber 2, 2004American National Standards InstituteAbstract: Methods for the calibration and use of germanium spectrometers for the measurementof gamma-ray energies and emission rates over the energy range from 59 keV to approximately3000 keV, and for the calculation of source activities from these mea
5、surements, 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 limitations of the algorith
6、ms used for locatingand fitting single and multiple peaks are described. Methods for the measurement of, and thecorrection for pulse pileup are suggested. Techniques are recommended for the inspection of spec-tral-analysis results for large errors resulting from summing of cascade gamma rays in the
7、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, germaniumspectrometers, radionuclides, sp
8、ectrometersAmerican National StandardAn American National Standard implies a consensus of those substantially concerned with its scopeand provisions. An American National Standard is intended as a guide to aid the manufacturer, theconsumer, and the general public. The existence of an American Nation
9、al Standard does not in anyrespect preclude anyone, whether he has approved the standard or not, from manufacturing, market-ing, purchasing, or using products, processes, or procedures not conforming to the standard. Amer-ican National Standards are subject to periodic reviews and users are cautione
10、d to obtain the latesteditions.CAUTION NOTICE:This American National Standard may be revised or withdrawn at any time.The procedures of the American National Standards Institute require that action be taken to reaf-firm, revise, or withdraw this standard no later than five years from the date of pub
11、lication. Purchas-ers of American National Standards may receive current information on all standards by calling orwriting the American National Standards Institute.Authorization to photocopy portions of any individual standard for internal or personal use isgranted by the Institute of Electrical an
12、d Electronics Engineers, Inc., provided that the appropriatefee is paid to Copyright Clearance Center. To arrange for payment of licensing fee, please contactCopyright Clearance Center, Customer Service, 222 Rosewood Drive, Danvers, MA 01923 USA;(508) 750-8400. Permission to photocopy portions of an
13、y individual standard for educational class-room use can also be obtained through the Copyright Clearance Center.Copyright 1999 IEEE. All rights reserved.iiiIntroduction(This introduction is not part of ANSI N42.14-1999, American National Standard for Calibration and Use of GermaniumSpectrometers fo
14、r the Measurement 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 responsibil
15、ity of the Accredited Standards Committee N42 on Radiation Instrumenta-tion. Committee N42 delegated the development of the standard to its Subcommittee N42.RM. Drafts werereviewed by members of Committee N42, Subcommittee N42.RM, and other interested parties, and thecomments received were utilized
16、in producing the standard as finally approved and issued. The standard wasapproved by Committee N42 letter ballot of 17 December 1997.ParticipantsAt the time it approved this standard, the Accredited Standards Committee on Radiation Instrumentation,N42, had the following members:Louis Costrell,Chair
17、Michael P. Unterweger, Vice ChairNaeem Ahmad,SecretariatOrganization Represented Name of RepresentativeAmerican Conference of Governmental Industrial Hygienists.Jesse LiebermanApplied Safety Technology.Edward J. Vallario*Battelle Pacific NW Laboratories .Joseph C. McDonaldBicronJoseph G. BellianEber
18、line Instruments .James K. HeschEGb) Coincidence (cascade) summing;c) The decay of the source during sampling (e.g., with air filters) 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 is not accounted
19、 for by the full-energypeak efficiency calibration.2. ReferencesThis standard shall be used in conjunction with the following publications. When the following standards aresuperseded by an approved revision, the revision shall apply.ANSI N13.30-1996, American National Standard Performance Criteria f
20、or Radiobioassay.3ANSI N42.23-1996, American National Standard Measurement and Associated Instrument Quality Assur-ance for Radioassay Laboratories.4IEEE Std 100-1996, IEEE Standard Dictionary of Electrical and Electronics Terms.5IEEE Std 325-1996, IEEE Standard Test Procedures for Germanium Gamma-R
21、ay Detectors.3ANSI 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/).4This publication is available from the Institute of Electrical and Electronics Engineers, 445 Hoes Lane, P.O. Box 1
22、331, Piscataway, NJ08855-1331, USA (www.standards.ieee.org/).5IEEE 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/).ANSIFOR THE MEASUREMENT OF GAMMA-RAY EMISSION RATES OF RADIO
23、NUCLIDES Std N42.14-1999Copyright 1999 IEEE. All rights reserved.33. DefinitionsThe 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 therequirements
24、 of this standard, but not necessarily with its recommendations; however, justification should bedocumented for deviations from a recommendation.For the purposes of this standard, the following terms and definitions apply. IEEE Std 100-1996 should bereferenced for terms not defined in this clause.3.
25、1 abundance:See:emission probability per decay P(E) or Pg(E).3.2 activity (A):The expected number of spontaneous nuclear decays (transformations) in unit time from aspecified energy state (excluding prompt decays from a lower nuclear level) for a given amount of a radionu-clide. Its standard unit (S
26、I) is the becquerel (Bq), where one Bq equals one decay per second. Activity hasoften been expressed in curies (Ci), where 3.7 1010Bq equals 1 Ci, exactly.3.3 ADC conversion gain:The number of channels over which the full amplitude span can be spread; usu-ally 20488192 channels are used for Ge gamma
27、-ray spectrometry.3.4 analog-to-digital converter (ADC):An electronic device used to convert the amplitude of a voltagepulse from analog to digital format.3.5 attenuation:The net loss at the detector of primary photons of a given energy resulting from their inter-action with matter either due to the
28、 occurrence of scattering or absorption in the sample or in materialbetween 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 surrounding environment or resulting from cosmic-ray int
29、eractions in or adjacentto 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 counts per second into emission rate).3.9 cascade summing:
30、 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 gamma rays: The simultaneous detection of two or more photons
31、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 B uncer-tainties, as defined by the Bureau International des Po
32、ids et Mesures (BIPM), using standard statisticalmethods. Category A uncertainties are evaluated by applying statistical methods to a series of repeated mea-surements and are characterized by the estimated standard deviation, sA; category B uncertainties areassigned to quantities whose variation is
33、not explicitly observed. Category B uncertainties are determined byestimating from other information an approximation to a corresponding “standard deviation,” sB, whoseexistence is assumed. They are combined as if they are all standard deviations.ANSIStd N42.14-1999 AMERICAN NATIONAL STANDARD CALIBR
34、ATION AND USE OF GERMANIUM SPECTROMETERS4Copyright 1999 IEEE. All rights reserved.3.13 continuum:The part of the pulse-height distribution lying underneath a peak, including contributionsassociated with the source, detector, and measuring conditions that affect the spectral shape. Syn:baseline.3.14
35、counting rate:The rate at which detector pulses are being registered in a selected voltage interval. Theunit is reciprocal seconds (i.e., s-1).3.15 crossover transition:A gamma ray occurring between two nonadjacent nuclear levels.3.16 dead time:The time during which the ADC is unable to process inpu
36、t pulses because it is processing aprevious pulse.3.17 detection efficiency:The ratio between the number of selected pulses recorded per unit time to thenumber of photons emitted by the source per unit time. See also:full-energy peak efficiency; totalefficiency.3.18 direct current (dc) level:The inp
37、ut or output voltage level on a dc-coupled instrument when there areno pulses present. For Ge spectrometer systems, the dc level of an output signal from a linear amplifiershould be matched to the input requirements for dc levels of an ADC if the gain conversion scale is toinclude the origin.3.19 el
38、apsed time (Tr):Counting time uncompensated for periods in which an instrument might be unableto respond. Elapsed time of a count equals live time plus dead time.3.20 emission probability per decay P(E) or Pg(E):The probability that a radioactive decay will be fol-lowed by the emission of the specif
39、ied radiation. Gamma-ray emission probabilities are often expressed per100 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 peak height with the baseline removed.3.22 energy resolution, full width at tenth maximum (FW
40、TM): The width of a peak at one-tenth of themaximum peak height with the baseline removed. For a normal (Gaussian) distribution, FWTM is 1.823times its FWHM.3.23 full-energy peak:A peak in the spectrum resulting from the complete (total) absorption of a photon ofa given energy in the active volume o
41、f the Ge crystal and the collection of all of the resulting charge.Syn: photopeak.3.24 full-energy peak efficiency e(E):The ratio between the number of counts in the net area of the full-energy peak to the number of photons of that energy emitted by a source with specified characteristics for aspeci
42、fied 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 the level (not to be confused with emission probability perdecay).3.26 gamma-ray emission rate R(E):The rate at
43、which a gamma ray of a given energy from the decay ofa particular radionuclide is emitted from a given source. The gamma-ray emission rate is the activity timesthe gamma-ray emission probability.3.27 live time (TL):The time interval of a count during which a counting system is capable of processingi
44、nput pulses. Elapsed (or real) time equals live time plus dead time.ANSIFOR THE MEASUREMENT OF GAMMA-RAY EMISSION RATES OF RADIONUCLIDES Std N42.14-1999Copyright 1999 IEEE. All rights reserved.53.28 Monte Carlo:A modeling technique in which the interaction of a gamma-ray of energy Ewith matteris pre
45、dicted by simulation.3.29 multichannel analyzer:See:multichannel pulse-height analyzer.3.30 multichannel pulse-height analyzer (MCA):An electronic device that records and stores pulsesaccording to their height. It consists of three function segments: an ADC to provide a means of measuringpulse ampli
46、tude; memory registers (one for each channel of the spectrum) to tally the number of pulseshaving an amplitude within a given voltage increment; an input/output section that permits transfer of thespectral information to other devices, such as a computer, oscilloscope display, or permanent storage m
47、edia(disk or magnetic tape storage). Syn:multichannel analyzer.3.31 peak-to-Compton ratio for the 1332 keV 60Co peak: The ratio of the full-energy peak height, for60Co measured at 1332 keV, to the average height of the corresponding Compton plateau between 1040 keVand 1096 keV.3.32 Peak-to-total rat
48、io:The net area of a full-energy mono-energetic peak divided by the counts in the fullspectrum detected, including scattering contributions making up the spectrum (e.g., backscattering) fromsaid gamma ray.3.33 photopeak: See:full-energy peak.3.34 pole-zero cancellation:The pole-zero adjustment on th
49、e shaping amplifier adjusts the zero location ofthe pole-zero network to cancel exactly the preamplifier output pole and thus provide single-pole (i.e., nounder or overshoot) response of the signal pulse at the amplifier output. This operation converts the long-tailed preamplifier pulse to a short-tailed pulse suitable for signal optimization and subsequent pulse-heightanalysis. Proper pole-zero cancellation is an absolute necessity to prevent spectral degradation at moderate(2000 s-1) rates. (See Figure B.1 for an example of proper adjustment for pole-zero cancellatio
