1、Designation: E 1855 05e1Standard Test Method forUse of 2N2222A Silicon Bipolar Transistors as NeutronSpectrum Sensors and Displacement Damage Monitors1This standard is issued under the fixed designation E 1855; the number immediately following the designation indicates the year oforiginal adoption o
2、r, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.e1NOTEEditorial changes were made throughout in September 2005.1. Scope1.1 This test meth
3、od covers the use of 2N2222A siliconbipolar transistors as dosimetry sensors in the determination ofneutron energy spectra, and as silicon 1-MeV equivalentdisplacement damage fluence monitors.1.2 The neutron displacement damage is especially valuableas a spectrum sensor in the range 0.1 to 2.0 MeV w
4、hen fissionfoils are not available. It has been applied in the fluence rangebetween 2 3 1012n/cm2and 1 3 1014n/cm2and should beuseful up to 1015n/cm2. This test method details the steps forthe acquisition and use of silicon 1-MeV equivalent fluenceinformation (in a manner similar to the use of activ
5、ation foildata) for the determination of neutron spectra.1.3 In addition, this sensor can provide important confirma-tion of neutron spectra determined with other sensors, andyields a direct measurement of the silicon 1-MeV fluence bythe transfer technique.1.4 This standard does not purport to addre
6、ss 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 regulatory requirements prior to use.2. Referenced Documents2.1 TheASTM standards E 170, E 261
7、, and E 265 provide abackground for understanding how sensors are used in radia-tion measurements and general dosimetry. The rest of thestandards referenced in the list discuss the choice of sensors,spectrum determinations with sensor data, and the prediction ofneutron displacement damage in some se
8、miconductor devices,particularly silicon.2.2 ASTM Standards:2E 170 Terminology Relating to Radiation Measurementsand DosimetryE 261 Practice for Determining Neutron Fluence, FluenceRate, and Spectra by Radioactivation TechniquesE 265 Test Method for Measuring Reaction Rates andFast-Neutron Fluences
9、by Radioactivation of Sulfur-32E 720 Guide for Selection and Use of Neutron-ActivationFoils for Determining Neutron Spectra Employed inRadiation-Hardness Testing of ElectronicsE 721 Guide for Determining Neutron Energy Spectra fromNeutron Sensors for Radiation-Hardness Testing of Elec-tronicsE 722 P
10、ractice for Characterizing Neutron Energy FluenceSpectra in Terms of an Equivalent Monoenergetic NeutronFluence for Radiation-Hardness Testing of ElectronicsE 844 Guide for Sensor Set Design and Irradiation forReactor Surveillance, E706 (IIC)E 944 Practice forApplication of Neutron SpectrumAdjust-me
11、nt Methods in Reactor Surveillance, (IIA)E 1854 Practice for Ensuring Test Consistency in Neutron-Induced Displacement Damage of Electronic PartsE 2005 Guide for the Benchmark Testing of Reactor Do-simetry in Standard and Reference Neutron Fields3. Terminology3.1 Symbols:F1= the silicon 1-MeV equiva
12、lent fluence (see PracticeE 722).hFE= ic/ibwhere icis the collector current and ibis the basecurrent, in a common emitter circuit.1This test method is under the jurisdiction ofASTM Committee E10 on NuclearTechnology and Applications and is the direct responsibility of SubcommitteeE10.07 on Radiation
13、 Dosimetry for Radiation Effects on Materials and Devices.Current edition approved July 1, 2005. Published August 2005. Originallyapproved in 1996. Last previous edition approved in 2004 as E 1855 04e1.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Serv
14、ice at serviceastm.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.4. Summary of Test Method4.1 Gain degradatio
15、n of 2N2222Asilicon bipolar transistorsmeasured in a test (simulation) environment is compared withthat measured in a reference neutron environment. The F1rinthe reference environment is derived from the known referencespectrum and is used to determine a measured F1tin the testenvironment (1,2)3by t
16、he transfer technique. The subscripts rand t refer to the reference and test environments respectively.4.2 The measured F1tmay be used as a sensor response ina spectrum adjustment code in a manner similar to the use ofreaction foil activities to determine the spectrum (3,4).4.3 Spectra compatible wi
17、th the responses of many sensorsmay be used to calculate a more reliable measure of thedisplacement damage.5. Significance and Use5.1 The neutron spectrum in a test (simulation) environmentmust be known in order to use a measured device response inthe test environment to predict the device performan
18、ce in anoperational environment (see Practice E 1854).Typically, spec-tra are determined by use of a set of sensors that have responsefunctions that are sensitive over the neutron energy region towhich the device under test (DUT) responds (see Guide E 721).In particular, for silicon devices exposed
19、in reactor neutronspectra, this effective energy range is between 0.01 and 10MeV. A typical set of activation reactions which lack fissionreactions from nuclides such as235U,237Np, or239Pu, willhave very poor sensitivity to the spectrum between 0.01 and 2MeV. For a pool-type reactor spectrum, 70 % o
20、f the DUTelectronic damage response may lie in this range. Often, fissionfoils are not included in the sensor set for spectrum determi-nations because their use must be licensed, and they requirespecial handling for health physics considerations. The silicontransistors provide the needed response to
21、 define the spectrumin this critical range.5.2 If fission foils are a part of the sensor set, the siliconsensor provides an important confirmation of the spectrumshape.5.3 Bipolar transistors, such as type 2N2222A, are inexpen-sive, are smaller than fission foils contained in a boron ball, andare ea
22、sy and quick to read provided the proper steps are taken.They also can be used directly in arrays to map 1-MeVequivalent fluence. The proper set of steps to take in readingthe transistor-gain degradation is the primary subject of thistest method.5.4 Fig. 1 shows the displacement damage function fors
23、ilicon.As can be seen from the figure, the major portion of theresponse for the silicon transistors will generally be above 100keV. The currently recommended silicon damage function islisted in Practice E 722.6. Apparatus6.1 A transistor with demonstrated response in agreementwith calculated F1value
24、s in widely varied environments is thesilicon bipolar transistor 2N2222A. It is recommended thatthree or more of these transistors be calibrated together andused at each location to be characterized. At least three othersshould be used as temperature correction devices (controldevices) during readou
25、t. The control transistors should beexposed one time to a calibration exposure of about 1.0 3 1013n/cm21-MeV equivalent fluence and then annealed (baked out)at 180C for 24 h followed by ambient air cooling before beingused as controls. These control transistors are not exposedeither during the calib
26、ration or test step, but are read with theexposed transistors to provide temperature correction.6.2 A dry oven for annealing is needed to stabilize the gainafter both the calibration-exposure and gain readout are com-pleted for the reference environment. The oven shall be able tomaintain the set tem
27、perature to within 63.0C at 80C and at180C. It would be prudent to have a timer for automaticshutdown and an emergency power system (UPS). Shutdownwith a timer will require a door-opening mechanism forambient air cooling.3The boldface numbers in parentheses refer to a list of references at the end o
28、fthis test method.FIG. 1 Silicon Displacement Damage Response FunctionE185505e126.3 An electronic system is required to maintain appropriatetransistor bias and currents and to read the currents for the gainmeasurements. It is recommended that a programmable semi-conductor parameter tester (such as a
29、 Hewlett Packard 4145A)be used. A programmable tester can operate in pulsed mode tocontrol heating effects and provide gain values quickly. Theparameter tester determines the common emitter current gainby injecting a pulse of current into the base region, measuringthe collector current, and determin
30、ing the current ratio ic/ibata fixed bias of 10 V, where icis the collector current and ibisthe base current. The bias voltage is measured between thecollector and the base (see Ref (5).6.4 A reference neutron source (see Guide E 2005) forcalibration of the transistors is required. The neutron fluen
31、ceand neutron fluence spectrum of the reference source must beknown. National Institute for Standards and Technology(NIST) benchmark fields (6) are recommended for use asprimary standards, and the Fast Burst Reactors (FBRs) atSandia National Laboratories, White Sands Missile Range, andAberdeen Provi
32、ng Ground also are recommended as referencebenchmark fields.6.5 If the transistors are exposed on a different run than theone used to expose foils for spectrum determination, a suitablemonitor such as a nickel foil must be exposed along with thetransistors during calibration to relate the magnitude
33、of theneutron fluence during the spectrum determination exposure tothat during the transistor calibration exposure (see Section 7).A photon-sensitive (and neutron insensitive) detector such as aCaF2thermoluminescent detector (TLD) shall be included ineach test package to monitor the gamma-ray dose i
34、n case acorrection must be made for the transistor damage fromgamma-rays.7. Description of the Test Method7.1 2N2222A transistors exhibit a range of initial gainvalues and responses, but each responds linearly with 1-MeVequivalent fluence, F1, at fixed collector current according tothe Messenger-Spr
35、att equation (7), if gamma rays do notcontribute to the change of gain.1hFEF21hFEO5 KtF1 MeV! (1)The term hFEOis the common emitter current gain at somefixed collector current before irradiation in the test environ-ment, and hFEFis the same quantity measured at the samecollector current after irradi
36、ation. Ktis the damage constant. Ifgamma-ray dose contributes to the change in the reciprocal ofthe gain, then that contribution must be subtracted from the leftside of Eq 1 (see 8.3).7.2 A semiconductor parameter analyzer may be used todetermine hFE. A basic schematic circuit used by semiconduc-tor
37、 analyzers for measuring hFE= ic/ibis shown in Fig. 2. Anyequivalent method for making the electrical measurement isacceptable as long as the currents do not exceed the limitsdetailed in 8.1.2 and 8.1.3.7.3 Since Ktdiffers for each transistor, each must becalibrated. When the technology of manufactu
38、re is such thatthe Kts within a batch are the same to within a few percentagepoints, a calibration by batch may be satisfactory. A typicalvalue for Ktis about 1.5 3 1015cm2/neutron for a collectorcurrent of 1 mA.7.4 The linearity of response of a given batch of transistorsshall be verified by exposu
39、re of samples of the batch to at leastthree levels of neutron fluence covering the range in which thedevices will be used.7.5 The calibration is accomplished by exposing the tran-sistors in a reference field for which the absolute values of theneutron fluence spectrum are known over the neutron ener
40、gyrange in which significant damage is caused. The 1-MeVequivalent fluence of the reference environment, F1r,isob-tained by folding the spectrum with the silicon displacementdamage response as is described in Practice E 722. The gainvalues, hFEObefore irradiation, and hFEFafter irradiation aremeasur
41、ed, and the left side of Eq 1 is calculated. The followingquantity can be defined.DS1hD51hFEF21hFEO(2)This is the change in reciprocal gain.Asubscript of r is usedto denote the reciprocal gain change in the reference calibrationenvironment. A subscript of t is used to denote the reciprocalgain chang
42、e in the test or unknown environment. This mea-surement and the known value of F1rin the referenceenvironment provide the calibration for the transistor, Kt.NOTE 1As mentioned in 6.5, if the transistors are exposed on adifferent run than the run for measuring the spectrum, a monitor foil mustbe incl
43、uded with the transistors. This monitor foil should be the same asone of the sensor set so that a simple ratio of the monitor responsesmultiplied by the transistor response will provide the proper scalingbetween the runs.This procedure of using the ratio of activities to scale thefluences is valid b
44、ecause the same spectrum is used for both runs.7.6 When the D(1/h) is measured in the unknown testenvironment, the F1tcan be found in the following manner.Take the ratio of equations (Eq 1) for the reference and testenvironments and rearrange the terms to yield Eq 3 (see Ref(3).F1t5DS1hDtDS1hDrF1r51
45、KtDS1hDt(3)7.7 The F1tis the quantity needed as a sensor value in thespectrum determination procedure. The D(1/h)tis the change inthe reciprocal gain induced by the test environment. Forneutron damage on 2N2222A transistors, Ktis a constant forneutron fluences up to about 1015n/cm2. The method descr
46、ibedFIG. 2 Schematic for Transistor Read-OutE185505e13here provides a direct determination of F1t. Strictly speaking,if F1tis the only quantity desired from the test when thetransistor is irradiated, then a monitor is not needed. However,it is recommended that a monitor be included for possiblescali
47、ng and for ensuring that the ratio of responses between thetransistors and the monitor remain the same at characterizedpositions in the neutron field.8. Experimental Procedure8.1 To ensure proper calibration of the sensor, follow thesteps described in 8.1.1-8.1.9.8.1.1 Step 1The 2N2222Atransistors a
48、re inexpensive andcan be purchased in large lots from electronic supply houses.Those purchased from readily available commercial sourceshave been found to be fairly uniform in electrical propertiesand come with initial gains between about 50 and 200. The firststep is to measure, at 1 mA collector cu
49、rrent, the initial gainvalues of all the transistors in the batch. Throw out all thosewith gain less than 100, and then remove the top and bottom5 % fractions of the remaining set.Thus, if one begins with 100transistors there may be two with gains below 100, and afterremoving 10 % of the remaining distribution, one might end upwith about 88 transistors that can be calibrated. If the calibra-tion environment is large enough to provide a uniform fluenceto all the transistors on the same run, it is best to calibrate thewhole batch together. The minimum number of transistorss
