1、Designation: E668 10Standard Practice forApplication of Thermoluminescence-Dosimetry (TLD)Systems for Determining Absorbed Dose in Radiation-Hardness Testing of Electronic Devices1This standard is issued under the fixed designation E668; the number immediately following the designation indicates the
2、 year oforiginal adoption 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 Depa
3、rtment of Defense.1. Scope1.1 This practice covers procedures for the use of thermolu-minescence dosimeters (TLDs) to determine the absorbed dosein a material irradiated by ionizing radiation. Although someelements of the procedures have broader application, thespecific area of concern is radiation-
4、hardness testing of elec-tronic devices. This practice is applicable to the measurementof absorbed dose in materials irradiated by gamma rays, Xrays, and electrons of energies from 12 to 60 MeV. Specificenergy limits are covered in appropriate sections describingspecific applications of the procedur
5、es. The range of absorbeddose covered is approximately from 102to 104Gy (1 to 106rad), and the range of absorbed dose rates is approximatelyfrom 102to 1010Gy/s (1 to 1012rad/s). Absorbed dose andabsorbed dose-rate measurements in materials subjected toneutron irradiation are not covered in this prac
6、tice. Further, theportion of these procedures that deal with electron irradiationare primarily intended for use in parts testing. Testing ofdevices as a part of more massive components such aselectronics boards or boxes may require techniques outside thescope of this practice.NOTE 1The purpose of th
7、e upper and lower limits on the energy forelectron irradiation is to approach a limiting case where dosimetry issimplified. Specifically, the dosimetry methodology specified requires thatthe following three limiting conditions be approached: (a) energy loss ofthe primary electrons is small, (b) seco
8、ndary electrons are largely stoppedwithin the dosimeter, and (c) bremsstrahlung radiation generated by theprimary electrons is largely lost.1.2 This standard dose not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard t
9、o establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E170 Terminology Relating to Radiation Measurements andDosimetryE380 Practice for Use of the International System of Units(SI) (the
10、Modernized Metric System)E666 Practice for CalculatingAbsorbed Dose From Gammaor X Radiation2.2 International Commission on Radiation Units andMeasurements (ICRU) Reports:3ICRU Report 14Radiation Dosimetry: X Rays andGamma Rays with Maximum Photon Energies Between0.6 and 50 MeVICRU Report 17Radiatio
11、n Dosimetry: X Rays Generatedat Potentials of 5 to 150 keVICRU Report 21Radiation Dosimetry: Electrons with Ini-tial Energies Between 1 and 50 MeVICRU Report 31Average Energy Required to Produce anIon PairICRU Report 33Radiation Quantities and UnitsICRU Report 34The Dosimetry of Pulsed RadiationICRU
12、 Report 37Stopping Powers for Electrons andPositrons3. Terminology3.1 Definitions:3.1.1 absorbed dose, Dthe quotient of dbydm, where dis the mean energy imparted by ionizing radiation to the matterin a volume element and dm is the mass of matter in thatvolume element.1This practice is under the juri
13、sdiction of ASTM Committee E10 on NuclearTechnology and Applications and is the direct responsibility of SubcommitteeE10.07 on Radiation Dosimetry for Radiation Effects on Materials and Devices onMaterials and Devices.Current edition approved June 1, 2010. Published August 2010. Originallyapproved i
14、n 1978. Last previous edition approved in 2005 as E668 05. DOI:10.1520/E0668-10.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page
15、onthe ASTM website.3Available from International Commission on Radiation Units and Measure-ments, 7910, Woodmont Ave., Suite 800, Bethesda, MD 20814.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.D 5ddm(1)Previously, the special uni
16、t of absorbed dose was the rad;however, the gray (Gy) has been adopted as the official SI unit(see Practice E380).1Gy5 1Jkg215 102rad (2)3.1.2 absorbed-dose ratethe absorbed dose per unit timeinterval.3.1.3 annealingthermal treatment of a TLD prior toirradiation or prior to readout.3.1.3.1 Discussio
17、nPre-irradiation annealing of TLDs isusually done to erase the effects of previous irradiation and toreadjust the sensitivity of the phosphor; pre-readout annealingusually is done to reduce low-temperature TLD response.3.1.4 calibration conditionsthe normal environmentalconditions prevailing during
18、routine calibration irradiationssuch as the ambient temperature, humidity, and lighting.3.1.5 equilibrium absorbed dosethe absorbed dose atsome incremental volume within the material which thecondition of electron equilibrium (as many electrons of a givenenergy enter as leave the volume) exists (1)4
19、(see AppendixX1).3.1.6 exposure, Xthe quotient of dQ by dm, where dQ isthe absolute value of the total charge of the ions of one signproduced in air when all the electrons (negatrons and positrons)liberated by photons in a volume element of air having massdm are completely stopped in air.X 5dQdm(3)U
20、nitCkg13.1.6.1 DiscussionFormerly the special unit of exposurewas the roentgen (R).1 R 5 2.58 3 1021C kg21exactly! (4)3.1.7 primary electronsfor the case of electron irradia-tion, the electrons introduced into the device under test by theirradiation source.3.1.8 secondary-electron equilibriumfor the
21、 case of elec-tron irradiation, the condition where as many secondaryelectrons of a given energy enter a given volume as leave it.3.1.9 secondary-electron equilibrium absorbed doseforthe case of electron irradiation, the absorbed dose at someincremental volume within the material in which the condit
22、ionof secondary-electron equilibrium exists.3.1.9.1 DiscussionAdditional definitions can be found inICRU Report 33.3.1.10 secondary electronsfor the case of electron irra-diation, electrons knocked out of the electron shells of thematerial being irradiated by the primary electron. For the caseof pho
23、ton irradiation, energetic electrons (photoelectrons,Auger electrons, and Compton electrons) produced within thematerial being irradiated by the action of the incident photons.3.1.10.1 DiscussionSecondary electrons are produced bythe interaction of the primary electrons with the atoms of thematerial
24、 being irradiated. This interaction is a principal meansof energy loss for the primary electrons. The kinetic energy ofa secondary electron is typically much lower than that of theprimary electron which creates it.3.1.11 test conditionsthe normal environmental condi-tions prevailing during routine h
25、ardness-test irradiations suchas the ambient temperature, humidity, and lighting.3.1.12 thermoluminescence dosimeter (TLD)a TL phos-phor, alone, or incorporated in a material, used for determiningthe absorbed dose in materials. For example, the TL phosphoris sometimes incorporated in a TFE-fluorocar
26、bon matrix.3.1.13 thermoluminescence dosimeter (TLD) batchagroup of TLDs, generally originating from a single mix or lotof TL phosphor, having similar TL responses and similarthermal and irradiation histories.3.1.14 thermoluminescence dosimeter (TLD) readeran in-strument used to measure the light em
27、itted from a TLDconsisting essentially of a heating element, a light-measuringdevice, and appropriate electronics.3.1.15 thermoluminescence dosimeter (TLD) responsethemeasured light emitted by the TLD and read out during itsheating cycle consisting of one of the following: (a) the totallight output
28、over the entire heating cycle, (b) a part of that totallight output, or (c) the peak amplitude of the light output.3.1.16 thermoluminescence (TL) phosphora material thatstores, upon irradiation, a fraction of its absorbed dose invarious excited energy states. When thermally stimulated, thematerial e
29、mits this stored energy in the form of photons in theultraviolet, visible, and infrared regions.3.1.17 TLD preparationthe procedure of cleaning, an-nealing, and encapsulating the TLphosphor prior to irradiation.3.2 For units and terminology in reports of data, Terminol-ogy E170 may be used as a guid
30、e.4. Significance and Use4.1 Absorbed dose in a material is an important parameterthat can be correlated with radiation effects produced inelectronic components and devices that are exposed to ionizingradiation. Reasonable estimates of this parameter can becalculated if knowledge of the source radia
31、tion field (that is,energy spectrum and particle fluence) is available. Sufficientlydetailed information about the radiation field is generally notavailable. However, measurements of absorbed dose withpassive dosimeters in a radiation test facility can provideinformation from which the absorbed dose
32、 in a material ofinterest can be inferred. Under certain prescribed conditions,TLDs are quite suitable for performing such measurements.NOTE 2For comprehensive discussions of various dosimetry methodsapplicable to the radiation types and energy and absorbed dose-rate rangediscussed in this practice,
33、 see ICRU Reports 14, 17, 21, and 34.5. Apparatus5.1 The TLD System consists of the TLDs, the equipmentused for preparation of the TLDs, and the TLD reader.5.2 Calibration Facility delivers a known quantity of radia-tion to materials under certain prescribed environmental andgeometrical conditions.
34、Its radiation source is usually a radio-active isotope, commonly either60Co or137Cs, whose radiation4The boldface numbers in parentheses refer to the list of references at the end ofthis practice.E668 102output has been calibrated by specific techniques to somespecified uncertainty (usually to withi
35、n 65 %) and is traceableto national standards.5.3 Storage Facility provides an environment for the TLDsbefore and after irradiation, that is light tight and that has anegligible background absorbed-dose rate.ATLD stored in thefacility for the longest expected storage period should absorbno more than
36、 1 % of the lowest absorbed dose expected to bemeasured in hardness-testing applications.5.4 Environmental Chamber is used in testing the effects oftemperature and humidity on TLD response. The chambershould be capable of controlling the temperature and humiditywithin 65 % over the range expected un
37、der both calibrationand test conditions.6. Handling and Readout Procedures6.1 Bare TLDs should not be handled with the bare fingers;dirt or grease on their surfaces can affect their response and cancontaminate the heating chamber of the TLD reader.Avacuumpen or tweezers coated with TFE-fluorocarbon
38、should be usedin handling. If required, the TLDs can be cleaned by using theprocedures in accordance with Appendix X2.6.2 TLDs, especially those with high sensitivity, should beprotected from light having an appreciable ultraviolet compo-nent, such as sunlight or fluorescent light. Prolonged exposur
39、eto ultraviolet light, either before or after irradiation, can causespurious TLD response or enhanced post-irradiation fading.Incandescent lighting should be used for the TLD preparationand readout areas. However, brief exposures of a few minutesto normal room fluorescent lighting is not likely to s
40、ignificantlyaffect the TLD response except for low absorbed-dose mea-surements (102Gy (104rad). See, however, X2.2.2.8.2 Reproducibility of TLD Response of Individual ReusableDosimetersCertain types of TLDs may be utilized as indi-vidual reusable dosimeters. In this case, the identity of eachindivid
41、ual dosimeter is maintained during repeated measure-ment cycles throughout its useful life. This is in contrast toutilization in the batch mode where individual dosimeterswithin the batch are not identified. To test the reproducibility ofthe response of an individual reusable dosimeter, the followin
42、gprocedures should be followed:8.2.1 Select the individual TLD to be tested, prepare it,irradiate it in the calibration facility to a specific absorbed-doselevel (for example, at the midpoint of the absorbed-dose rangeof interest), and read it out. In an identical manner, repeat thisprocedure 30 tim
43、es. Determine the variance, s2, of the re-sponses and estimate the standard deviation of the TLDresponse distribution s5=s2!. The standard deviation, s,should not exceed 5 % of the mean response value, Y0, that iss # (0.05) Y0.8.2.2 Some types of TLDs may exhibit a change in sensi-tivity (that is, r
44、esponse per unit absorbed dose) with repeatedanneal-irradiation-readout cycling. This effect is most pro-nounced if the TLD is not annealed thoroughly. The test resultsin accordance with 8.2.1 may not show such a change inresponse sensitivity. However, if such a change is shown in thattest or if it
45、appears after a larger number of cycles thanspecified in that test, then a different analysis of the data isrequired. In this case, a curve should be fitted to the data ofresponse versus number of cycles by a least-squares method.Ameasure of reproducibility would then be given by the averagestandard
46、 deviation of the data points from the least-squarescurve. The performance criterion is the same as in 8.2.1.8.2.3 Since the identity of each TLD is maintained when itis utilized as an individual dosimeter, it is not necessary thatgroups of such individual TLDs meet the batch requirements inaccordan
47、ce with 8.1. However, for the other performance testsand correction factors discussed in Section 8, it is assumed thatsuch tests and factors are evaluated by utilizing TLDs in abatch mode.8.3 Dependence of TLD Response on Absorbed-Dose Rate:8.3.1 From a TLD batch meeting the requirements inaccordanc
48、e with 8.1.1, select a number of TLDs. Divide theTLDs into x number of groups, each group containing nsamples. Determine the absorbed-dose-rate range of interestfor the intended application and divide this range into xintervals (for example, one interval per decade). Prepare all theTLDs in an identi
49、cal manner and irradiate each group to thesame dose level, but at a different absorbed-dose rate for eachx group, covering the absorbed-dose-rate range of interest.Read out the TLDs. Determine the mean response, Yi, for eachx group of n samples. Determine an overall mean value, Y0, forall x group means. Then the absolute difference between anygroup mean and the overall mean should not exceed 20 % ofthe overall mean. That is,|Yi2 Y0|# 0.2!Y0(7)8.3.2 If | Yi Y0| (0.05) Y0, then appropriate correctionfactors to the TLD response
