ASTM_E_2450_-_16.pdf

Designation:E245016Standard Practice forApplication of CaF2(Mn)Thermoluminescence Dosimeters inMixed Neutron-Photon Environments1This standard is issued under the fixed designation E2450;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 This practice describes a procedure for correcting aCaF2(Mn)thermoluminescence dosimeter(TLD)reading forits response to neutrons during the irradiation.The neutronresponse may be subtracted from the total TLD response togive the gamma-ray response.In fields with a large neutroncontribution to the total response,this procedure may result inlarge uncertainties.1.2 More precise experimental techniques may be applied ifthe uncertainty derived from this practice is larger than thelevel that the user can accept.These more precise techniquesare not discussed here.The references in Section 8 describesome of these techniques.1.3 This practice does not discuss effects on the TLDreading from neutron interactions with the material surround-ing the TLD and used to ensure a charged particle equilibrium.These effects will depend on the isotopic composition of thesurrounding material and its thickness,and on the incidentneutron spectrum(1).21.4 The values stated in SI units are to be regarded asstandard.2.Referenced Documents2.1 ASTM Standards:3E170 Terminology Relating to Radiation Measurements andDosimetryE666 Practice for Calculating Absorbed Dose From Gammaor X RadiationE668 Practice for Application of Thermoluminescence-Dosimetry(TLD)Systems for Determining AbsorbedDose in Radiation-Hardness Testing of Electronic DevicesE720 Guide for Selection and Use of Neutron Sensors forDetermining Neutron Spectra Employed in Radiation-Hardness Testing of ElectronicsE721 Guide for Determining Neutron Energy Spectra fromNeutron Sensors for Radiation-Hardness Testing of Elec-tronicsE722 Practice for Characterizing Neutron Fluence Spectra inTerms of an Equivalent Monoenergetic Neutron Fluencefor Radiation-Hardness Testing of ElectronicsE1854 Practice for Ensuring Test Consistency in Neutron-Induced Displacement Damage of Electronic PartsF1190 Guide for Neutron Irradiation of Unbiased ElectronicComponents3.Terminology3.1 Definitions:3.1.1 absorbed dosesee Terminology E170.3.1.2 exposuresee Terminology E170.3.1.3 kermasee Terminology E170.3.1.4 linear energy transfer(LET)the energy loss per unitdistance as a charged particle passes through a material.3.1.4.1 DiscussionElectrons resulting from gamma-rayinteractions in a material generally have a low LET.Heavycharged particles resulting from neutron interactions with amaterial generally have a high LET.3.1.5 neutron sensitivity m(E)the ratio of the detectorreading,that is,the effective neutron dose,to the neutronfluence.Thus,mE!5ME!E!(1)where:(E)=the neutron fluence,andM(E)=the apparent dose(light output)in the TLD causedby neutrons of energy E.4.Significance and Use4.1 Electronic devices are typically tested for survivabilityto gamma radiation in pure gamma-ray fields.Testing elec-tronic device response against neutrons is more complex sincethere is invariably a gamma-ray component in addition to the1This practice 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 Materials and Devices.Current edition approved June 1,2016.Published July 2016.Originally approvedin 2005.Last previous edition approved in 2011 as E2450 11.DOI:10.1520/E2450-16.2The boldface numbers in parentheses refer to the list of references at the end ofthis standard.3For 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.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 neutron field.The gamma-ray response of the electronic deviceis typically subtracted from the overall response to find thedevice response to neutrons.This approach to the testingrequires a determination of the gamma-ray exposure in themixed field.To enhance the neutron effects,the radiation fieldis sometimes selected to have as large a neutron component aspossible.4.2 CaF2(Mn)TLDs are often used to monitor the gamma-ray dose in mixed neutron/gamma radiation fields.Since thedosimeters are exposed along with the device under test to themixed field,their response must be corrected for neutrons.In afield rich in neutrons,the uncertainty in the interpretation of theTLD response grows.In fields with relatively few neutrons,thetotal TLD response may be used to make a correction forgamma response of the device u