ANSI N42.25-1997 Calibration and Usage of Alpha Beta Proportional Counters《a β射线正比计数器的校准和使用》.pdf

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1、 STD-IEEE N42.25-ENGL L777 4805702 05527q 731 m ANSI N42.25-1997 American National Standard Calibration and Usage of AlphdBeta Proportional Counters uj a z Accredited Standards Committee Sponsored by the National Committee on Radiation Instrumentation, N42 PIrbliShed by the Instute of EMcai and EEec

2、aoniics En (508) 750-8400. Permission to photocopy portions of any individual standard for educational classroom use can also be obtained through the Copyright Clearance Center. 11 Copyright The Institute of Electrical and Electronics Engineers, Inc. Provided by IHS under license with IEEENot for Re

3、saleNo reproduction or networking permitted without license from IHS-,-,- STD-IEEE N42-25-ENGL L997 4805702 D5.52951 226 = Introduction (This introduction is not part of ANSI N42.25-1997, American National Standard Calibration and Usage of Alphmeta Proportional Counters.) This standard is the respon

4、sibility of the Accredited Standards Committee on Radiation Instrumentation, N42. Committee N42 delegated development of this standard to Subcommittee N42.M. Drafts were reviewed by Committee N42, Subcommittee N42.M, and other interested parties, and the comments received were utilized in producing

5、the standard as finally approved. The standard was approved by N42 letter ballot of 18 March 1996. At the time it approved this standard, the Accredited Standards Committee on Radiation Instrumentation, N42, had the following members: Louis Costrell, Chair Luigi Napoli, Administrative Secretary Orga

6、nization Represented Name of Representative American Conference of Governmental Industrial Hygienists Jesse Lieberman Battelle Pacific Northwest Laboratories Kenneth L. Swinth Health Physics Society . . George Campbell Joseph R. Stencel (Ast.) Julian Forster (Alt.) Anthony J. Spurgin (Alt.) Institut

7、e of Electrical and Electronics Engineers . Louis Costrell Lawrence Berkeley Laborato ry. Lawrence Livermore National Laborato ry. Massachusetts Institute of Technology, Bates Li US Department of Commerce, National Institute of Standards and Edward J. Lampo . Paul L. Phelps celerator Center . Frank

8、X. Masse US Army Center for EWIRSDA Edward Groeber Technology Louis Costrell Michael Unterweger (Alt.) US Department of Energy Gerald Goldstein US Federal Emergency Management Agency . Carl R. Siebentritt Members-at-Large Joseph C. Bellian Ernesto A. Corte John M. Gallagher Jack M. Selby Al N. Tscha

9、eche Edward J. Vallario Lee J. Wagner Sanford Wagner At the time this standard was approved, Subcommittee N42.M had the following members: Frank X. Masse, Chair J. M. R. Hutchinson, Secretary Robert Ayres Joseph G. Bellian John D. Buchanan R. F. Coley Bert M. Coursey Michael Devine Roger Ferris Robe

10、rt J. Gehrke Y. Kobyashi Markku Koskeio J. L. Lazewatsky David E. McCurdy D. M. Montgomery Carl W. Seidel John Sonewald M. P. Unterweger iii Copyright The Institute of Electrical and Electronics Engineers, Inc. Provided by IHS under license with IEEENot for ResaleNo reproduction or networking permit

11、ted without license from IHS-,-,-STDaIEEE N42.25-ENGL 1997 VAU5702 0552752 Lb2 H The working group for this standard had the following members: Robert Gehrke, Project Leader Markku Koskelo, Project Leader David Bailey Kenneth Bloomfield Michael Devine Rick Tomblinson The following persons were on th

12、e balloting committee that approved this document for submission to the American National Standards Institute: Joseph G. Bellian Hugh R. Brashear George Campbell Emesto A. Corte Louis Costrell Morgan Cox Julian Forster John M. Gallagher Gerald Goldstein Edward Groeber Edward J. Lampo Jesse Lieberman

13、 Frank X. Masse Paul L. Phelps Jack M. Selby Carl L. Siebentritt Anthony J. Spurgin Rochelle L. Stem Joseph R. Stencel Kenneth L. swinth AI N. Tschaeche Michael Unterweger Edward J. Vallario Lee J. Wagner Sanford Wagner Edward C. Wenzinger, Sr. iv Copyright The Institute of Electrical and Electronic

14、s Engineers, Inc. Provided by IHS under license with IEEENot for ResaleNo reproduction or networking permitted without license from IHS-,-,- STD-IEEE N42.25-ENGL 1977 W 4805702 0552953 UT9 m Contents 1 . 2 . 3 . 4 . 5 . 6 . 7 . 8 . Overview 1 1.1 Scope 1 1.2 Special word usage 2 References 2 Definit

15、ions 2 3.1 Glossary . 2 3.2 Symbols . 5 3.3 Apparatus . 5 Calibration 5 4.1 General . 5 4.2 Detector plateau measurement . 6 4.3 Discriminator settings 8 4.4 Background 9 4.5 Efficiency 10 Sources . . 11 5.1 Efficiency calibration so . : . 11 5.2 Check sources 11 Performance tests . 12 6.1 Sources .

16、 12 6.2 Verification of counter background . 12 6.3 Verification of alpha, b s . 13 6.4 Verification of crosstalk 13 6.5 Effectiveness of guard d 13 6.6 Verification of alpha a . 14 6.7 Estimated uncertainty 14 Determination of uncertainties and their propagation . 15 Quality control and assurance 1

17、7 Annex A (informative) Preparation of working standards from standard solutions . 19 A.l A.2 Simple volumetric preparation of planchet style sources 19 Simple gravimetric preparation of planchet style sources . 20 (informative) Guidance on measurement of samples 21 Annex B B.l General precautions .

18、 21 B.2 Net count rates . 21 V Copyright The Institute of Electrical and Electronics Engineers, Inc. Provided by IHS under license with IEEENot for ResaleNo reproduction or networking permitted without license from IHS-,-,- STD-IEEE N42-25-ENGL L977 4805702 055295Y T35 m B.3 Concentrations . 23 B.4

19、Weight correction . 24 B.5 Health physics smear samples . 25 Annex C (informative) Bibliography 26 vi Copyright The Institute of Electrical and Electronics Engineers, Inc. Provided by IHS under license with IEEENot for ResaleNo reproduction or networking permitted without license from IHS-,-,- STD-I

20、EEE N42-25-ENGL 1997 48057U2 0552755 771 D American National Standard Calibration and Usage of AlphdBeta Proportional Counters 1. Overview This standard provides a basis for the routine calibration and use of gas proportional counters with or without active guard detectors. Gas proportional counters

21、 are used for the measurement of alpha and beta emission rates, and for the measurement of radionuclide activities when interferences from other radionuclides are not present. This standard is intended for use by persons who have an understanding of the principles of gas proportional counting and ar

22、e responsible for the development of correct procedures for the calibration and use of these radiation measurement counters. References B6, B7, and Bl i provide information on the principles of operation of alphaheta proportional counters. A typical alphaheta gas proportional counter consists of one

23、 or more gas proportional counters, active guard detectors, associated counting gas, signal processing electronics, and a scaler, or a multi-channel analyzer to record the detected counts. Computers are commonly interfaced to these systems to provide computer control as well as to permit automatic c

24、orrection for efficiency, self attenuation, and other sample specific factors, and for storage of quality assurance/quality control information. Automatic propagation of uncertainties is also provided by many commercially supplied computer-controlled instruments. 1.1 Scope This standard establishes

25、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

26、 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

27、 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. There

28、fore, this standard is intended for measuring radionuclides with maximum beta energies above 100 keV. The numbers in brackets correspond to those of the bibliography in Annex C. 1 Copyright The Institute of Electrical and Electronics Engineers, Inc. Provided by IHS under license with IEEENot for Res

29、aleNo reproduction or networking permitted without license from IHS-,-,-ANSI N42.25-1997 AMERICAN NATIONAL STANDARD CALIBRATION AND USAGE OF 1.2 Special word usage The word shall denotes a requirement, the word should denotes a recommendation, and the word may denotes permission. To conform to this

30、standard, gas proportional counting shall be performed in accordance with the requirements of this standard, but not necessarily with its recommendations. However, justification should be documented for deviations from a recommendation. 2. References ANSI N42.14-1991, American National Standard Cali

31、bration and Use of Germanium Spectrometers for the Measurement of Gamma-Ray Emission Rates of Radionuclides.* ANSI N42.22-1995, American National Standard Traceability of Radioactive Sources to the National Institute of Standards and Technology (NIST) and Associated Instrument Quality Control. ANSI

32、N42.23-1996, American National Standard Measurement and Associated Instrumentation Quality Assurance for Radioassay Laboratories. 3. Definitions 3.1 Glossary 3.1.1 active guard detector: A de main sample counting detector. Th order to intercept and react to the s detector. Normally this detector is

33、background radiation field on the s the sample detector. 3.1.2 activity: The expected nu specified energy state (excluding pro radionuclide. Its standard unit (SI) is Activity is often also expressed in curies minute (dpm), where 1 dpm equals 1/60 aterials with similar geometry to the to the sample

34、counting detector in stria1 radiation field as the sample mode to cancel out the effect of this al-time adjusted net count rate for sformations) in unit time from a r nuclear level) for a given amount of a re one Bq equals one decay per second. Is one Ci exactly or in disintegrations per 3.1.3 alpha

35、 emission rate: The rate at which alpha particles of all energies are emitted from one or all alpha-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 the surface of a source or sample that contains

36、one or more alpha-emitting radionuclides. 3.1.5 attenuation: The net loss of radiation field from the sample resulting from scattering or absorption in the 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 r

37、adioactive decay not caused by a calibration source or sample but rather from that occurring in the surrounding environment or from cosmic-ray interactions in or adjacent to the detector that have escaped detection by the guard detector, when present. 2These ANSI N42 publications are available from

38、the institute of Electrical and Electronics Engineers, 445 Hoes Lane, P.O. Box 1331, Piscataway, NJ 08855-1331, USA. 2 Copyright The Institute of Electrical and Electronics Engineers, Inc. Provided by IHS under license with IEEENot for ResaleNo reproduction or networking permitted without license fr

39、om IHS-,-,- STD-IEEE N42.25-ENGL 1997 W 4805702 0552757 744 = ALPHNBETA PROPORTIONAL COUNTERS ANSI N42.25-1997 Contributions to the background count rate can include naturally occurring radioactive decay in the structural materials comprising the counter, shielding, and cosmic-ray-induced ionizing r

40、adiation. 3.1.7 beta emission rate: The rate at which beta particles of all energies are emitted from one or ail beta- emitting radionuclides present in a source or a sample. 3.1.8 beta surface emission rate: The rate at which beta particles of all energies emanate from the surface of a source or sa

41、mple that contains one or more beta-emitting radionuclides. 3.1.9 blank count. rate: Events per unit time from radioactive decay or cosmic-ray interactions in materials that make up the proportional counter, surrounding materials (background count rate), and the sample blank (consisting of the planc

42、het and sample matrix). A sample blank may contain naturally occurring radionuclides and their daughter products. 3.1.10 check source: A radioactive source, not necessarily calibrated, which is used to confirm satisfactory operation of an instrument. 3.1.11 combined uncertainty: The uncertainty resu

43、lting from combining category A and category B uncertainties, as defined by the Bureau International des Poids et Measures (BIPM) (see BS), using standard statistical methods. Category A uncertai evaluated by applying statistical methods to a series of repeated measurements and are characte e estima

44、ted standard deviation, SA; category B uncertainties are assigned to quantities whose variation is not explicitly observed. Category B uncertainties are determined by estimating from 0th approximation to a corresponding “standard deviation,” SB, whose existence is assume ed as if they are all standa

45、rd deviations. 3.1.12 count rate: The rate at which dete unit is reciprocal seconds (i.e., s-l) or reci 3.1.13 crosstalk: The fraction of all articles that are recorded in the beta channel due to degradation in their pulse height or the fraction of all recorded pulses from beta particles that are re

46、corded in the alpha channel due to pulse pileup or other phenomenon. The beta crosstalk into the alpha channel should be negligible if the operation point (see definition) has been selected correctly. This term is equivalent to the term spiZlup/spiZldown. Crosstalk is commonly used to indicate that

47、the method of discrimination is pulse-height discrimination. See al 3.1.14 dead band: A region between the highest beta pulse and the lowest alpha pulse for a given radionuclide or mix of radionuclides that contains no pulses when using energy or rise time discrimination, Due to physical processes o

48、r electronic limitations this region may contain pulses not anticipated to be present. d in a selected voltage interval. The 3.1.15 interference or cross chamber interference: The fraction of all recorded pulses in either the alpha channel or the beta channel of a multiple chamber counting system th

49、at are due to the presence of a sample in an adjacent counting chamber. 3.1.16 measurements assurance program (MAP): A program that allows manufacturers to verify the accuracy of their measurements through exchange of samples with the National Institute of Standards and Technology (NIST). This involves the analysis of blind test samples sent to the suppliers by NIST, and NIST measurement of sources certified and provided by the suppl