ASTM_E_1250_-_15.pdf

Designation:E125015Standard Test Method forApplication of Ionization Chambers to Assess the LowEnergy Gamma Component of Cobalt-60 Irradiators Used inRadiation-Hardness Testing of Silicon Electronic Devices1This standard is issued under the fixed designation E1250;the number immediately following the designation indicates the 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.1.Scope1.1 Low energy components in the photon energy spectrumof Co-60 irradiators lead to absorbed dose enhancement effectsin the radiation-hardness testing of silicon electronic devices.These low energy components may lead to errors in determin-ing the absorbed dose in a specific device under test.Thismethod covers procedures for the use of a specialized ioniza-tion chamber to determine a figure of merit for the relativeimportance of such effects.It also gives the design andinstructions for assembling this chamber.1.2 This method is applicable to measurements in Co-60radiation fields where the range of exposure rates is 7 106to 3 102C kg1s1(approximately 100 R/h to 100 R/s).Forguidance in applying this method to radiation fields where theexposure rate is 100 R/s,see Appendix X1.NOTE1See Terminology E170 for definition of exposure and its units.1.3 The values stated in SI units are to be regarded as thestandard.The values given in parentheses are for informationonly.1.4 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 regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2E170 Terminology Relating to Radiation Measurements andDosimetryE668 Practice for Application of Thermoluminescence-Dosimetry(TLD)Systems for Determining AbsorbedDose in Radiation-Hardness Testing of Electronic DevicesE1249 Practice for Minimizing Dosimetry Errors in Radia-tion Hardness Testing of Silicon Electronic Devices UsingCo-60 Sources3.Terminology3.1 absorbed dose enhancement factor ratio of the ab-sorbed dose at a point in a material of interest to theequilibrium absorbed dose in that same material.3.2 average absorbed dosemass-weighted mean of theabsorbed dose over a region of interest.3.3 average absorbed dose enhancement factorratio ofthe average absorbed dose in a region of interest to theequilibrium absorbed dose.3.4 dosimeterany device used to determine the equilib-rium absorbed dose in the material and at the irradiationposition of interest.Examples of such devices include ther-moluminescencedosimeters(TLDs),liquidchemicaldosimeters,and radiochromic dye films.(See Practice E668,for a discussion of TLDs.)3.5 equilibrium absorbed doseabsorbed dose at someincremental volume within the material in which the conditionof charged particle equilibrium(the energies,number,anddirection of charged particles induced by the radiation areconstant throughout the volume)exists.(See TerminologyE170.)4.Significance and Use4.1 Although Co-60 nuclei only emit monoenergetic gammarays at 1.17 and 1.33 MeV,the finite thickness of sources,andencapsulation materials and other surrounding structures thatare inevitably present in irradiators can contribute a substantialamount of low-energy gamma radiation,principally by Comp-ton scattering(1,2).3In radiation-hardness testing of electronicdevices this low-energy photon component of the gamma1This method is under the jurisdiction of ASTM Committee E10 on NuclearTechnology and Applicationsand is the direct responsibility of SubcommitteeE10.07 on Radiation Dosimetry for Radiation Effects on Materials and Devices.Current edition approved June 1,2015.Published August 2015.Originallyapproved in 1988.Last previous approved in 2010 as E1250-10.DOI:10.1520/E1250-15.2For 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 onthe ASTM website.3The boldface numbers in parentheses refer to the list of references appended tothis test method.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 spectrum can introduce significant dosimetry errors for adevice under test since the equilibrium absorbed dose asmeasured by a dosimeter can be quite different from theabsorbed dose deposited in the device under test because ofabsorbed dose enhancement effects(3,4).Absorbed doseenhancement effects refer to the deviations from equilibriumabsorbed dose caused by non-equilibrium electron transportnear boundaries between dissimilar materials.4.2 The ionization chamber technique described in thismethod provides an easy means for estimating the importanceof the l