1、Designation: E720 11Standard Guide forSelection and Use of Neutron Sensors for DeterminingNeutron Spectra Employed in Radiation-Hardness Testing ofElectronics1This standard is issued under the fixed designation E720; the number immediately following the designation indicates the year oforiginal adop
2、tion 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 facilit
4、ies,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 correctio
5、ns 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 applicab
6、le toother broad energy distribution sources up to 20 MeV.NOTE 1For definitions on terminology used in this guide, see Termi-nology E170.1.2 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 the
7、 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 E721.1.3 Details of measurement and analysis are covered asfollows:1.3
8、.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 calibration t
9、hat usessecondary standard gamma-ray emitting sources is consideredin this guide and in General Methods E181. In addition, analternative method in which the sensors are activated in theknown spectrum of a benchmark neutron field is discussed inGuide E1018.1.3.3 A data analysis method is presented wh
10、ich 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 other un
11、its 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 of reg
12、ulatory limitations prior to use.2. Referenced Documents2.1 General considerations of neutron-activation detectorsdiscussed in Practice E261, Test Method E262, and GuidesE721 and E844 are applicable to this guide. Backgroundinformation for applying this guide are given in these and otherrelevant sta
13、ndards as follows:2.2 ASTM Standards:2E170 Terminology Relating to Radiation Measurements andDosimetryE181 Test Methods for Detector Calibration andAnalysis ofRadionuclidesE261 Practice for Determining Neutron Fluence, FluenceRate, and Spectra by Radioactivation TechniquesE262 Test Method for Determ
14、ining Thermal Neutron Reac-tion Rates and Thermal Neutron Fluence Rates by Radio-activation 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
15、on Materials and Devices.Current edition approved June 1, 2011. Published July 2011. Originally approvedin 1980. Last previous edition approved in 2008 as E720 08. DOI: 10.1520/E0720-11.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceas
16、tm.org. For Annual Book of ASTMStandards 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.E263 Test Method for Measuring Fast-Neutron ReactionRates by
17、 Radioactivation of IronE264 Test Method for Measuring Fast-Neutron ReactionRates by Radioactivation of NickelE265 Test Method for Measuring Reaction Rates and Fast-Neutron Fluences by Radioactivation of Sulfur-32E266 Test Method for Measuring Fast-Neutron ReactionRates by Radioactivation of Aluminu
18、mE393 Test Method for Measuring Reaction Rates by Analy-sis of Barium-140 From Fission DosimetersE496 Test Method for Measuring Neutron Fluence andAverage Energy from3H(d,n)4He Neutron Generators byRadioactivation TechniquesE704 Test Method for Measuring Reaction Rates by Radio-activation of Uranium
19、-238E705 Test Method for Measuring Reaction Rates by Radio-activation of Neptunium-237E721 Guide for Determining Neutron Energy Spectra fromNeutron Sensors for Radiation-Hardness Testing of Elec-tronicsE844 Guide for Sensor Set Design and Irradiation forReactor Surveillance, E 706 (IIC)E944 Guide fo
20、r Application of Neutron Spectrum Adjust-ment Methods in Reactor Surveillance, E 706 (IIA)E1018 Guide for Application of ASTM Evaluated CrossSection Data File, Matrix E706 (IIB)E1297 Test Method for Measuring Fast-Neutron ReactionRates by Radioactivation of Niobium3. Significance and Use3.1 Because
21、of the wide variety 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 techniq
22、ues discussed are useful for 14-MeVdosimetry. See Test Method E496 for activation detector materials suitablefor 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 count
23、able activities.3.2 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 E170 and GeneralMethods E181. Determination of neutron spec
24、tra with activa-tion sensor data is discussed in Guides E721 and E944.4. 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 bec
25、ause of their 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
26、dosimetry cross 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-acti
27、vation technique.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
28、limits for anidealized 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 de
29、signed to minimize 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
30、addition, when 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
31、sensor requiring 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
32、 monitor because 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 ni
33、ckel the58Co must build upthrough a metastable state, and for sulfur there are competingreactions. According to Test Method E264 the waiting periodfor58Co should be 4 days. For32P, Test Method E265recommends waiting 24 h. Corrections can be made for shorterwaiting periods.4.1.4 In selecting dosimetr
34、y reactions 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 t
35、hese benchmark 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
36、low, and anadjustment 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) leav
37、e out reactionswhich have demonstrated consistent deviations; (2) seek betterE720 112TABLE 1 Activation FoilsReactionFast BurstATRIGA TypeAEgB, (keV)GammaEmissionProbabilityBFast FissionYield,C% T1/2BRecommendedFoil Mass, gDFootnotesEL, MeV EH, MeV EL, MeV EH, MeV197Au(n,g)198Au 4.00 6 7.20 4 3.80 6
38、 9.20 6 411.8025 95.54 2.6944 days 0.06E,F,G59Co(n,g)60Co 7.60 6 4.50 4 6.90 7 1.43 4 1173.2 99.85 5.2711 years 0.06E,G1332.5 99.98*58Fe(n,g)59Fe 1.00 6 2.10 + 0 5.25 7 1.00 2 1099.245 56.59 44.495 days 0.15E,H1291.59 43.2155Mn(n,g)56Mn 5.25 7 6.60 1 4.75 7 1.10 3 846.76 98.85 2.57878 h 0.05E,F1810.
39、726 26.9*63Cu(n,g)64Cu 1.15 6 2.30 + 0 5.25 7 9.60 3 1345.77 0.4743 12.700 h 0.15E23Na(n,g)24Na 6.30 7 2.00 + 0 5.25 7 3.00 3 1368.626 99.993 14.9574 h 0.10E,I,J2754.1 99.87245Sc(n,g)46Sc 4.25 7 1.00 + 0 4.00 7 4.75 4 889.27 99.983 83.788 days 0.05E1120.537 99.986235U(n,f)140La 9.20 2 4.70 + 0 6.30
40、4 3.80 + 0 1596.2 95.4 6.105 40.28 h 0.30E,K,L235U(n,f)95Zr 9.20 2 4.70 + 0 6.30 4 3.80 + 0 724.2 44.27 6.363 64.03 days 0.60E,L756.7 54.4239Pu(n,f)140La 1.43 1 4.80 + 0 8.80 4 4.30 + 0 1596.2 95.4 5.326 40.28 h 1.00E,K,L239Pu(n,f)95Zr 1.43 1 4.80 + 0 8.80 4 4.30 + 0 724.2 44.1 4.685 64.02 days 0.60
41、E,L756.7 54.493Nb(n,n8)93mNb 8.40 1 5.70 + 0 1.00 + 0 5.50 + 0 16.5-19.6 11.0 16.12 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 95.4 5.489 40.28 h 0.60E,K,L,N237Np(n,f)95Zr 5.75 1 5.60 + 0 6.60 1 5.50 + 0 724.2 44
42、.1 5.699 64.02 days 0.60E,L756.7 54.4*115In(n,n8)115mIn 1.00 + 0 6.00 + 0 1.20 + 0 5.80 + 0 336.2 45.9 4.49 h 0.12238U(n,f)140La 1.50 + 0 6.90 + 0 1.50 + 0 6.60 + 0 1596.2 95.4 5.948 40.28 h 1.00E,K,L,O238U(n,f)95Zr 1.50 + 0 6.90 + 0 1.50 + 0 6.60 + 0 724.2 44.1 5.105 64.02 days 1.00E,L756.7 54.4232
43、Th(n,f)140Ba 1.50 + 0 7.40 + 0 1.50 + 0 7.10 + 0 537.3 24.4 7.704 12.753 days 1.00E,K,P232Th(n,f)95Zr 1.50 + 0 7.40 + 0 1.50 + 0 7.10 + 0 724.2 44.1 5.374 64.02 days 1.00E,L756.7 54.454Fe(n,p)54Mn 2.30 + 0 7.70 + 0 2.30 + 0 7.40 + 0 834.838 99.9746 312.13 days 0.15E58Ni(n,p)58Co 2.00 + 0 7.60 + 0 2.
44、00 + 0 7.30 + 0 810.7 99.45 70.83 days 0.30E47Ti(n,p)47Sc 1.90 + 0 7.60 + 0 1.90 + 0 7.30 + 0 159.4 68.3 3.35 days 0.15E,Q,R32S(n,p)32P 2.40 + 0 7.50 + 0 2.30 + 0 7.30 + 0 1710.6 100. (beta) 14.284 days .S64Zn(n,p)64Cu 2.60 + 0 7.70 + 0 2.60 + 0 7.40 + 0 1345.7 0.4743 12.700 h 0.30E27Al(n,p)27Mg 3.5
45、0 + 0 9.40 + 0 3.40 + 0 9.20 + 0 843.8 71.8 9.46 min 0.30E1014.4 28.046Ti(n,p)46Sc 3.80 + 0 9.60 + 0 3.70 + 0 9.20 + 0 889.3 99.983 83.788 days 0.15E,Q1120.5 99.98656Fe(n,p)56Mn 5.50 + 0 1.14 + 1 5.50 + 0 1.10 + 1 846.7 98.85 2.57878 h 0.15E,T1810.7 26.924Mg(n,p)24Na 6.50 + 0 1.17 + 1 6.50 + 0 1.13
46、+ 1 1368.6 99.993 14.9574 h 0.03E,J2754.1 99.87227Al(n,a)24Na 6.50 + 0 1.21 + 1 6.50 + 0 1.17 + 1 1368.6 99.993 14.9574 h 0.30E,J2754.1 99.87248Ti(n,p)48Sc 5.90 + 0 1.24 + 1 5.90 + 0 1.20 + 1 983.5 100.1 43.7 h 0.15E1037.5 97.561312.1 100.193Nb(n,2n)92mNb 9.70 + 0 1.45 + 1 9.40 + 0 1.40 + 1 934.4 99
47、.1 10.15 days127I(n,2n)126I 9.70 + 0 1.47 + 1 9.70 + 0 1.43 + 1 388.6 35.6 12.93 days 0.25E666.3 32.965Cu(n,2n)64Cu 1.08 + 1 1.57 + 1 1.07 + 1 1.53 + 1 1345.7 0.475 12.701 h 0.15E,M*63Cu(n,2n)62Cu 1.19 + 1 1.66 + 1 1.19 + 1 1.63 + 1 875.7 0.150 9.74 min 0.15E,H90Zr(n,2n)89Zr 1.28 + 1 1.69 + 1 1.27 +
48、 1 1.67 + 1 909.1 99.0 78.4 h 0.1058Ni(n,2n)57Ni 1.32 + 1 1.71 + 1 1.31 + 1 1.69 + 1 1377.6 81.2 35.9 h 0.30AEnergy limits inside of which 95 % of the detector response occurs for each reaction (see Practice E261 and Refs (7,8). The foils are assumed to have Cd covers asdescribed in Footnote E.BData
49、 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. Many gamma-ray energies rounded to nearest 0.1 keV. For uncertainties on values, see references.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 to 1-mm thicknesses. Pairs of bare and Cd-covered foils are advantageous for resonance reaction
