1、Designation: E 720 08Standard Guide forSelection and Use of Neutron Sensors for DeterminingNeutron Spectra Employed in Radiation-Hardness Testing ofElectronics1This standard is issued under the fixed designation E 720; the number immediately following the designation indicates the year oforiginal ad
2、option or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.1
3、. Scope1.1 This guide covers the selection and use of neutron-activation detector materials to be employed in neutron spectraadjustment techniques used for radiation-hardness testing ofelectronic semiconductor devices. Sensors are described thathave been used at many radiation hardness-testing facil
4、ities,and comments are offered in table footnotes concerning theappropriateness of each reaction as judged by its cross-sectionaccuracy, ease of use as a sensor, and by past successfulapplication. This guide also discusses the fluence-uniformity,neutron self-shielding, and fluence-depression correct
5、ions thatneed to be considered in choosing the sensor thickness, thesensor covers, and the sensor locations. These considerationsare relevant for the determination of neutron spectra fromassemblies such as TRIGA- and Godiva-type reactors and fromCalifornium irradiators. This guide may also be applic
6、able toother broad energy distribution sources up to 20 MeV.NOTE 1For definitions on terminology used in this guide, see Termi-nology E 170.1.2 This guide also covers the measurement of the gamma-ray or beta-ray emission rates from the activation foils andother sensors as well as the calculation of
7、the absolute specificactivities of these foils. The principal measurement techniqueis high-resolution gamma-ray spectrometry. The activities areused in the determination of the energy-fluence spectrum of theneutron source. See Guide E 721.1.3 Details of measurement and analysis are covered asfollows
8、:1.3.1 Corrections involved in measuring the sensor activi-ties include those for finite sensor size and thickness in thecalibration of the gamma-ray detector, for pulse-height ana-lyzer deadtime and pulse-pileup losses, and for backgroundradioactivity.1.3.2 The primary method for detector calibrati
9、on that usessecondary standard gamma-ray emitting sources is consideredin this guide and in General Methods E 181. In addition, analternative method in which the sensors are activated in theknown spectrum of a benchmark neutron field is discussed inGuide E 1018.1.3.3 A data analysis method is presen
10、ted which accountsfor the following: detector efficiency; background subtraction;irradiation, waiting, and counting times; fission yields andgamma-ray branching ratios; and self-absorption of gammarays and neutrons in the sensors.1.4 The values stated in SI units are to be regarded asstandard. No ot
11、her units of measurement are included in thisstandard.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility
12、of regulatory limitations prior to use.2. Referenced Documents2.1 General considerations of neutron-activation detectorsdiscussed in Practice E 261, Test Method E 262, and GuidesE 721 and E 844 are applicable to this guide. Backgroundinformation for applying this guide are given in these and otherre
13、levant standards as follows:2.2 ASTM Standards:2E 170 Terminology Relating to Radiation Measurementsand DosimetryE 181 Test Methods for Detector Calibration and Analysisof RadionuclidesE 261 Practice for Determining Neutron Fluence, FluenceRate, and Spectra by Radioactivation TechniquesE 262 Test Me
14、thod for Determining Thermal Neutron Re-action and Fluence Rates by Radioactivation Techniques1This guide is under the jurisdiction of ASTM Committee E10 on NuclearTechnology and Applications and is the direct responsibility of SubcommitteeE10.07 on Radiation Dosimetry for Radiation Effects on Mater
15、ials and Devices.Current edition approved July 1, 2008. Published July 2008. Originally approvedin 1980. Last previous edition approved in 2004 as E 720 041.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of AS
16、TMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.E 263 Test Method for Measuring Fast-Neutron ReactionRates by Radioactivation of IronE 26
17、4 Test Method for Measuring Fast-Neutron ReactionRates by Radioactivation of NickelE 265 Test Method for Measuring Reaction Rates andFast-Neutron Fluences by Radioactivation of Sulfur-32E 266 Test Method for Measuring Fast-Neutron ReactionRates by Radioactivation of AluminumE 393 Test Method for Mea
18、suring Reaction Rates byAnaly-sis of Barium-140 From Fission DosimetersE 496 Test Method for Measuring Neutron Fluence andAverage Energy from3H(d,n)4He Neutron Generators byRadioactivation TechniquesE 704 Test Method for Measuring Reaction Rates by Ra-dioactivation of Uranium-238E 705 Test Method fo
19、r Measuring Reaction Rates by Ra-dioactivation of Neptunium-237E 721 Guide for Determining Neutron Energy Spectra fromNeutron Sensors for Radiation-Hardness Testing of Elec-tronicsE 844 Guide for Sensor Set Design and Irradiation forReactor Surveillance, E 706(IIC)E 944 Guide for Application of Neut
20、ron Spectrum Adjust-ment Methods in Reactor Surveillance, E 706 (IIA)E 1018 Guide for Application of ASTM Evaluated CrossSection Data File, Matrix E 706 (IIB)E 1297 Test Method for Measuring Fast-Neutron ReactionRates by Radioactivation of Niobium3. Significance and Use3.1 Because of the wide variet
21、y of materials being used inneutron-activation measurements, this guide is presented withthe objective of bringing improved uniformity to the specificfield of interest here: hardness testing of electronics primarilyin critical assembly reactor environments.NOTE 2Some of the techniques discussed are
22、useful for 14-MeVdosimetry. See Test Method E 496 for activation detector materialssuitable for 14-MeV neutron effects testing.NOTE 3The materials recommended in this guide are suitable for252Cf or other weak source effects testing provided the fluence issufficient to generate countable activities.3
23、.2 This guide is organized into two overlapping subjects;the criteria used for sensor selection, and the procedures usedto ensure the proper determination of activities for determina-tion of neutron spectra. See Terminology E 170 and GeneralMethods E 181. Determination of neutron spectra with activa
24、-tion sensor data is discussed in Guides E 721 and E 944.4. Foil Sets4.1 Reactions Considered:4.1.1 Neutron-induced reactions appropriate for this guideare listed in Table 1. The table includes most of the reactionsused in this field. Those not marked with an asterisk arerecommended because of their
25、 demonstrated compatibilitywith other reactions used in spectrum adjustment determina-tions. This compatibility is primarily based on experience withthe ENDF/B-VI (1, 2),and IRDF-90 (3) cross-sections. Theserecommendations may change modestly as revisions are madein the ENDF/B and IRDF dosimetry cro
26、ss sections. Otherreactions may be useful in particular circumstances withappropriate care. It is important that the user take full accountof both the footnotes attached to each reaction and thediscussions in the body of the text about individual reactionswhen implementing the foil-activation techni
27、que.4.1.2 The four paired columns under the labels fast burst (4)and “TRIGA (5) Type” list the energy ranges within which95 % of the response occurs for these two representativespectra.These limits are just a guide because the response oftenvaries widely within each range. The response limits for an
28、idealized fission spectrum with no 1/E tail can be muchdifferent (shifted toward higher energy) for resonance reac-tions. For example, in a Watt fission spectrum the197Au(n,g)198Au has a 95 % response between 5.0 3 102and 2.7 MeV. The recommended foil mass column gives valuesthat are designed to min
29、imize self-absorption, self-shielding,and other corrections, provided the foils are 1.27 cm indiameter. The Et 0 fission foils,235U and239Pu, have similarcross-section shapes. However, the235U foil is preferred sinceit is less expensive and is much less of a health hazard than239Pu. In addition, whe
30、n measuring soft (TRIGA) spectra, the235U foil is useful in determining the correction for the235Uimpurity in the238U foil (which is readily available with about400 ppm or less235U impurity).4.1.3 Although sulfur is listed and is used widely as amonitor foil, it is the only recommended sensor requir
31、ing betaparticle detection and, therefore, requires a different calibrationand counting technique. The58Ni(n,p)58Co reaction has aboutthe same threshold energy and, therefore, can be used insteadof the32S(n,p)32P if it acquires sufficient activity. Manyfacilities use sulfur as a routine monitor beca
32、use its two-weekhalf-life allows a convenient period for counting and permitsreuse of the sensor after 6 to 9 months. Automated betacounters are commercially available. Neither nickel nor sulfurshould be counted for the (n,p) reaction products immediatelyafter irradiation because for nickel the58Co
33、must build upthrough a metastable state, and for sulfur there are competingreactions. According to Test Method E 264 the waiting periodfor58Co should be 4 days. For32P, Test Method E 265recommends waiting 24 h. Corrections can be made for shorterwaiting periods.4.1.4 In selecting dosimetry reactions
34、 one should considerthe validation of the cross sections and associated uncertaintyas demonstrated in the235U thermal fission and the252Cfspontaneous fission benchmark neutron fields. Ref (6) providesa recent comparison of the measured and calculated spectrum-averaged cross sections for these benchm
35、ark fields.4.1.5 Some frequently used reactions have shown relativelyconsistent deviations of measured to calculated activity ratiosin many different spectra determinations. For example, whenENDF/B-V cross sections are used in the reaction63Cu(n,g)64Cu, the calculated activity is usually low, and an
36、adjustment code will try to raise the spectrum in the vicinity ofCu resonances. In fact, however, this consistent behaviorindicates that the tabulated cross-section values in someimportant energy region are too small. The analyst must thenchoose one of the following alternatives: (1) leave out react
37、ionswhich have demonstrated consistent deviations; (2) seek betterE720082cross-section sets; (3) assign wide error bars or low statisticalweight to these reactions. It is recommended that the firstoption be chosen because a sufficient number of well-established cross sections do exist to satisfactor
38、ily determinefast reactor spectra. Furthermore, if the cross section for aparticular reaction is not well established, and it is assigned tooTABLE 1 Activation FoilsReactionFast BurstATRIGA TypeAEg, keVGamma/ReactionB(Fast FissionYield,%C)T1/2BRecommendedFoil Mass, gDFootnotesEL, MeV EH, MeV EL, MeV
39、 EH, MeV197Au(n,g)198Au 4.00 6 7.20 4 3.80 6 9.20 6 411.8 0.956 2.694 days 0.06E,F,G59Co(n,g)60Co 7.60 6 4.50 4 6.90 7 1.43 4 1173.2 0.9998 5.271 years 0.06E,G1332.5 0.9998*58Fe(n,g)59Fe 1.00 6 2.10 + 0 5.25 7 1.00 2 1099.2 0.565 44.5 days 0.15E,H1291.6 0.43255Mn(n,g)56Mn 5.25 7 6.60 1 4.75 7 1.10 3
40、 846.8 0.989 2.58 h 0.05E,F1810.7 0.272*63Cu(n,g)64Cu 1.15 6 2.30 + 0 5.25 7 9.60 3 1345.9 0.0049 12.7 h 0.15E23Na(n,g)24Na 6.30 7 2.00 + 0 5.25 7 3.00 3 1368.6 1.00 14.96 h 0.10E,I,J45Sc(n,g)46Sc 4.25 7 1.00 + 0 4.00 7 4.75 4 889.3 1.00 83.81 days 0.05E235U(n,f)140La 9.20 2 4.70 + 0 6.30 4 3.80 + 0
41、 1596.2 0.954 (6.105) 40.27 h 0.30E,K,L235U(n,f)95Zr 9.20 2 4.70 + 0 6.30 4 3.80 + 0 724.2 0.441 (6.363) 64.02 days 0.60E,L239Pu(n,f)140La 1.43 1 4.80 + 0 8.80 4 4.30 + 0 1596.2 0.954 (5.326) 40.27 h 1.00E,K,L239Pu(n,f)95Zr 1.43 1 4.80 + 0 8.80 4 4.30 + 0 724.2 0.441 (4.685) 64.02 days 0.60E,L93Nb(n
42、,n8)93mNb 8.40 1 5.70 + 0 1.00 + 0 5.50 + 0 16.6 0.115 16.13 yearsM103Rh(n,n8)103mRh 5.50 1 5.70 + 0 6.90 1 5.70 + 0 39.8 0.068 56.1 minM237Np(n,f)140La 5.75 1 5.60 + 0 6.60 1 5.50 + 0 1596.2 0.954 (5.489) 40.27 h 0.60E,K,L,N237Np(n,f)95Zr 5.75 1 5.60 + 0 6.60 1 5.50 + 0 724.2 0.441 (5.699) 64.02 da
43、ys 0.60E,L*115In(n,n8)115mIn 1.00 + 0 6.00 + 0 1.20 + 0 5.80 + 0 336.2 0.459 4.49 h 0.12238U(n,f)140La 1.50 + 0 6.90 + 0 1.50 + 0 6.60 + 0 1596.2 0.954 (5.948) 40.27 h 1.00E,K,L,O238U(n,f)95Zr 1.50 + 0 6.90 + 0 1.50 + 0 6.60 + 0 724.2 0.441 (5.105) 64.02 days 1.00E,L232Th(n,f)140Ba 1.50 + 0 7.40 + 0
44、 1.50 + 0 7.10 + 0 537.3 0.244 (7.704) 12.75 days 1.00E,K,P232Th(n,f)95Zr 1.50 + 0 7.40 + 0 1.50 + 0 7.10 + 0 724.2 0.441 (5.374) 64.02 days 1.00E,L54Fe(n,p)54Mn 2.30 + 0 7.70 + 0 2.30 + 0 7.40 + 0 834.8 1.00 312.1 days 0.15E58Ni(n,p)58Co 2.00 + 0 7.60 + 0 2.00 + 0 7.30 + 0 810.8 0.995 70.8 days 0.3
45、0E47Ti(n,p)47Sc 1.90 + 0 7.60 + 0 1.90 + 0 7.30 + 0 159.4 0.683 3.35 days 0.15E,Q,R32S(n,p)32P 2.40 + 0 7.50 + 0 2.30 + 0 7.30 + 0 1710.(beta) 1.00 (beta) 14.28 days .S64Zn(n,p)64Cu 2.60 + 0 7.70 + 0 2.60 + 0 7.40 + 0 1345.9 0.0049 12.7 h 0.30E27Al(n,p)27Mg 3.50 + 0 9.40 + 0 3.40 + 0 9.20 + 0 843.8
46、0.718 9.46 min 0.30E46Ti(n,p)46Sc 3.80 + 0 9.60 + 0 3.70 + 0 9.20 + 0 889.3 1.00 83.81 days 0.15E,Q56Fe(n,p)56Mn 5.50 + 0 1.14 + 1 5.50 + 0 1.10 + 1 846.8 0.989 2.58 h 0.15E,T24Mg(n,p)24Na 6.50 + 0 1.17 + 1 6.50 + 0 1.13 + 1 1368.6 1.00 14.96 h 0.03E,J27Al(n,a)24Na 6.50 + 0 1.21 + 1 6.50 + 0 1.17 +
47、1 1368.6 1.00 14.96 h 0.30E,J48Ti(n,p)48Sc 5.90 + 0 1.24 + 1 5.90 + 0 1.20 + 1 983.5 1.00 43.7 h 0.15E1037.5 0.9751312.1 1.0093Nb(n,2n)92mNb 9.70 + 0 1.45 + 1 9.40 + 0 1.40 + 1 934.4 0.992 10.15 days127I(n,2n)126I 9.70 + 0 1.47 + 1 9.70 + 0 1.43 + 1 388.6 0.341 13.02 days 0.25E666. 0.33165Cu(n,2n)64
48、Cu 1.08 + 1 1.57 + 1 1.07 + 1 1.53 + 1 1345.9 0.0049 12.7 h 0.15E,M*63Cu(n,2n)62Cu 1.19 + 1 1.66 + 1 1.19 + 1 1.63 + 1 875.7 0.00150 9.74 min 0.15E,H90Zr(n,2n)89Zr 1.28 + 1 1.69 + 1 1.27 + 1 1.67 + 1 909.1 0.999 78.4 h 0.1058Ni(n,2n)57Ni 1.32 + 1 1.71 + 1 1.31 + 1 1.69 + 1 1377.6 0.80 1.49 days 0.30
49、AEnergy limits inside of which 95 % of the detector response occurs for each reaction (see Practice E 261 and Refs (7,8). The foils are assumed to have Cd coversas described in Footnote E.BData taken from Refs (9-11). Ref (11) takes precedent, but it only addresses reactions used in detector calibration. In other cases, Ref (9) provides the half-life andRef (10) provides the gamma yields.CFission yields can be found in Ref (12).DChoice of mass is based on assumed foil diameter of 1.27 cm.ECd covers 0.5
