ASTM E2304-2003(2011) Standard Practice for Use of a LiF Photo-Fluorescent Film Dosimetry System《使用Lif照片荧光薄膜计量系统的标准操作规程》.pdf

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1、Designation: E2304 03 (Reapproved 2011)An American National StandardStandard Practice forUse of a LiF Photo-Fluorescent Film Dosimetry System1This standard is issued under the fixed designation E2304; the number immediately following the designation indicates the year oforiginal adoption or, in the

2、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 covers the handling, testing, and procedurefor using a lithium fluoride (L

3、iF)-based photo-fluorescent filmdosimetry system to measure absorbed dose (relative to water)in materials irradiated by photons or electrons. Other alkalihalides that may also exhibit photofluorescence (for example,NaCl, NaF, and KCl) are not covered in this practice.Althoughvarious alkali halides h

4、ave been used for dosimetry for yearsutilizing thermoluminescence, the use of photoluminescence isrelatively new.1.2 This practice applies to photo-fluorescent film dosim-eters (referred hereafter as photo-fluorescent dosimeters) thatcan be used within part or all of the following ranges:1.2.1 Absor

5、bed dose range of 5 3 10-2to 3 3 102kGy(1-3).21.2.2 Absorbed dose rate range of 0.3 to 2 3 104Gy/s(2-5).1.2.3 Radiation energy range for photons of 0.05 to 10 MeV(2).1.2.4 Radiation energy range for electrons of 0.1 to 10 MeV(2).1.2.5 Radiation temperature range of -20 to +60C (6,7).1.3 The values s

6、tated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.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

7、and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:3E170 Terminology Relating to Radiation Measurements andDosimetryE275 Practice for Describing and Measuring Performanceof Ultraviolet and Visible SpectrophotometersE

8、925 Practice for Monitoring the Calibration of Ultraviolet-Visible Spectrophotometers whose Spectral Bandwidthdoes not Exceed 2 nm2.2 ISO/ASTM Standards:51204 Practice for Dosimetry in Gamma Irradiation Facili-ties for Food Processing51261 Guide for Selection and Calibration of DosimetrySystems for

9、Radiation Processing51431 Practice for Dosimetry in Electron and Bremsstrahl-ung Irradiation Facilities for Food Processing51608 Practice for Dosimetry in an X-ray (Bremsstrahlung)Facility for Radiation Processing51649 Practice for Dosimetry in an Electron Beam Facilityfor Radiation Processing at En

10、ergies between 300 keVand25 MeV51702 Practice for Dosimetry in a Gamma Irradiation Fa-cility for Radiation Processing51707 Guide for Estimating Uncertainties in Dosimetry forRadiation Processing51818 Practice for Dosimetry in an Electron Beam Facilityfor Radiation Processing at Energies between 80 k

11、eV and300 keV51956 Practice for Thermoluminescence-Dosimetry (TLD)Systems for Radiation Processing2.3 International Commission on Radiation Units andMeasurements (ICRU) Reports:4ICRU Report 14 Radiation Dosimetry: X-rays and Gammarays with Maximum Photon Energies Between 0.6 and 50MeVICRU Report 17

12、Radiation Dosimetry: X-rays Generated atPotentials of 5 to 150 kVICRU Report 34 The Dosimetry of Pulsed RadiationICRU Report 35 Radiation Dosimetry: Electron Beams withEnergies Between 1 and 50 MeVICRU Report 60 Fundamental Quantities and Units forIonizing Radiation1This practice is under the jurisd

13、iction of ASTM Committee E10 on NuclearTechnology and Applications and is the direct responsibility of SubcommitteeE10.01 on Radiation Processing: Dosimetry and Applications.Current edition approved Nov. 1, 2011. Published October 2003. Originallyapproved in 2003. Last previous edition approved in 2

14、003 as E2304-03. DOI:10.1520/E2304-03R11.2The 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 i

15、nformation, refer to the standards Document Summary page onthe ASTM website.4Available from International Commission on Radiation Units and Measure-ments, 7910 Woodmont Ave., Suite 800, Bethesda, MD 20814, USA.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 1

16、9428-2959, United States.3. Terminology3.1 Definitions:3.1.1 absorbed dose, Dquantity of ionizing radiationenergy imparted per unit mass of a specified material. The SIunit of absorbed dose is the gray (Gy), where 1 gray isequivalent to the absorption of 1 joule per kilogram of thespecified material

17、 (1 Gy = 1 J kg-1). The mathematical rela-tionship is the quotient of dby dm, where dis the meanincremental energy imparted by ionizing radiation to matter ofincremental mass dm (see ICRU 60).D 5ddm3.1.1.1 DiscussionAbsorbed dose is sometimes referredto simply as dose. For a photon source under cond

18、itions ofcharged particle-equilibrium, the absorbed dose, D, may beexpressed as:D 5fEenrwhere:f = particle fluence (m-2),E = energy of the ionizing radiation (J), anden/r = mass energy absorption coefficient (m2kg-1).If bremsstrahlung production within the specified material isnegligible, the mass e

19、nergy absorption coefficient (en/r)isequal to the mass energy transfer coefficient (tr/r), andabsorbed dose is equal to kerma if, in addition, charged-particleequilibrium exists.3.1.2 alkali halidea binary compound consisting of ahalogen (any of the five elements fluorine, chlorine, bromine,iodine,

20、and astatine) and an alkali metal (for example, lithium,sodium, and potassium).3.1.3 analysis wavelengthwavelength used in a spectro-photometric instrument to help determine a desired dosimetricquantity, for example, absorbed dose, by means of the mea-surement of optical absorbance, optical density,

21、 reflectance orluminescence.3.1.4 calibration facilitycombination of an ionizing radia-tion source and its associated instrumentation that provides auniform and reproducible absorbed dose, or absorbed-dose ratetraceable to national or international standards at a specifiedlocation and within a speci

22、fic material, and that may be used toderive the dosimetry systems response function or calibrationcurve.3.1.5 charged-particle equilibriumthe condition that ex-ists in an incremental volume within a material under irradia-tion if the kinetic energies and number of charged particles (ofeach type) ent

23、ering the volume are equal to those leaving thevolume.3.1.6 color centerimperfections (for example, negative-or positive-ion vacancies) within the ionic lattice of com-pounds that have trapped electrons or electron holes. Thesecenters, upon excitation by energy in the form of light or heat,can produ

24、ce luminescence.3.1.7 dosimeter batchquantity of dosimeters made from aspecific mass of material with uniform composition, fabricatedin a single production run under controlled, consistent condi-tions, and having a unique identification code.3.1.8 dosimetry systemsystem used for determining ab-sorbe

25、d dose, consisting of dosimeters, measurement instru-ments and their associated reference standards, and proceduresfor the systems use.3.1.9 electron equilibriumcharged particle equilibriumfor electrons.3.1.10 fluorescenceone of the four main luminescencemechanisms. In many materials, it involves th

26、e liberatedelectrons falling back to the valence banddirectly or via arelaxation stateto fill an electron hole, resulting in the releaseof a photon. In the case of alkali-halides the liberated electronsdo not fall back to the valance band, but are excited to a higherstate within the color center, an

27、d subsequently fall back to thecenters ground state, resulting in the release of a photon.3.1.11 fluorescence signal, Efthe photometric reading bya spectrofluorimeter in terms of light intensity incident on thephotodetector. Typically, the value measured is some quantityproportional to the standardi

28、zed quantity, irradiance, Ei(forexample, volts or amperes per unit area of detector surface, Vcm-2orAcm-2).3.1.12 fluorescence standarda solid or liquid material thatproduces a fluorescence upon excitation, with an emittedradiance that is calibrated and made traceable to a recognizedstandard.3.1.13

29、fluorimeterinstrument used to measure the amountof fluorescence signal, Ef, emitted from a sample upon excita-tion by an energy source (usually in the form of light).3.1.14 irradiance, Eia radiometric term for the radiantflux that is incident upon a surface, having units of W m-2.Alsosee radiance.NO

30、TE 1The standard symbol for irradiance is E; however, for thisdocument the subscript, i, was added to distinguish irradiance from energyof ionizing radiation (see 3.1.1) and fluorescence signal.3.1.15 luminescencephoton emission from a solid or liq-uid phosphor material during, or after, exposure to

31、 a form ofenergy. The main luminescence mechanisms are fluorescence,phosphorescence, thermoluminescence, and photolumines-cence.3.1.16 measurement quality assurance plana documentedprogram for the measurement process that ensures on acontinuing basis that the overall uncertainty meets the require-me

32、nts of the specific application.This plan requires traceabilityto, and consistency with, nationally or internationally recog-nized standards.3.1.17 measurement traceabilitythe ability to demonstrateby means of an unbroken chain of comparisons that a mea-surement is in agreement within acceptable lim

33、its of uncer-tainty with comparable nationally or internationally recognizedstandards.3.1.18 net fluorescence, DEfmeasured fluorescence sig-nal, Ef, from an irradiated sample, subtracted by the pre-irradiation fluorescence, Eo, as follows:DEf5 Ef2 Eo3.1.19 photo-fluorescent film dosimetera film-type

34、 dosim-eter, which upon excitation by visible or UV light, emitsfluorescent light.E2304 03 (2011)23.1.20 primary-standard dosimeterdosimeter of the high-est metrological quality, established and maintained as anabsorbed dose standard by a national or international standardsorganization.3.1.21 qualit

35、y assuranceall systematic actions necessaryto provide adequate confidence that a calibration, measure-ment, or process is performed to a predefined level of quality.3.1.22 radiance, Lradiant flux (watts) in a light beam,emanating from a surface, or falling on a surface, in a givendirection, per unit

36、 of projected area of the surface (m2)asviewed from that direction, per unit of solid angle (steradians).Has units of W m-2sr-1. See also, irradiance.3.1.23 reference-standard dosimetera dosimeter of highmetrological quality, used as a standard to provide measure-ments traceable to, and consistent w

37、ith, measurements madeusing primary-standard dosimeters.3.1.24 stockpart of a dosimeter batch, held by the user.3.1.25 transfer-standard dosimetera dosimeter, often areference-standard dosimeter suitable for transport betweendifferent locations, used to compare absorbed-dose measure-ments.3.1.26 ver

38、ificationconfirmation by examination of objec-tive evidence that specified requirements have been met.3.1.26.1 DiscussionIn the case of measuring equipment,the result of verification leads to a decision to restore to serviceor to perform adjustments, repair, downgrade, or declareobsolete. In all cas

39、es it is required that a written trace of theverification performed be kept on the instruments individualrecord.3.2 Definitions of other terms used in this standard thatpertain to radiation measurement and dosimetry may be foundin Terminology E170. Definitions in Terminology E170 arecompatible with

40、ICRU 60; that document, therefore, may beused as an alternative reference.4. Significance and Use4.1 A lithium fluoride (LiF)-based photo-fluorescent filmdosimetry system provides a means of determining absorbeddose to materials by the photo-stimulated emission of wave-lengths longer than that of th

41、e stimulation wavelength. Theabsorbed dose is obtained from the amount of the lightemission. Imperfections within the ionic lattice of alkali-halidecompounds such as LiF act as traps for electrons and electronholes (positively charged negative-ion vacancies). These im-perfections are known as color

42、centers because of the part theyplay in the compounds ability to absorb and then releaseenergy in the form of visible-light photons. Like an atom, thesecolor centers have discrete, allowed energy levels, and elec-trons can be removed from these sites when energy of theappropriate wavelength and inte

43、nsity is transferred to thematerial. The resulting fluorescence spectra contain discretepeaks that can cover a range of wavelengths, depending uponthe type of alkali-halide (8). An example of fluorescencespectra from a LiF-based dosimeter is provided in Fig. 1.Asystem of optical filters within a lig

44、ht-detecting instrument(that is, fluorimeter) can be used to block all but a narrow rangeof wavelengths that are desired for use. Theories on how colorcenters are formed, how luminescence mechanisms work, andtheir application in dosimetry are found in Refs (8-13). Forcharacterization studies on spec

45、ific photo-fluorescent dosim-eters see Refs (1-7) and (14-19).NOTEAlso shown are transmission curves for green and red emission filters.FIG. 1 Excitation Spectrum and Resulting Fluorescence Spectrum from the Sunna LiF-based Film DosimeterE2304 03 (2011)34.2 In the application of a specific dosimetry

46、 system,absorbed dose is determined by use of an experimentally-derived calibration curve. The calibration curve for the photo-fluorescent dosimeter is the functional relationship betweenDEfand D, and is determined by measuring the net fluores-cence of sets of dosimeters irradiated to known absorbed

47、 doses.These absorbed doses span the range of utilization of thesystem.4.3 Photo-fluorescent dosimetry systems require calibrationtraceable to national standards. See ISO/ASTM Guide .4.4 The absorbed dose is usually specified relative to water.Absorbed dose in other materials may be determined byapp

48、lying the conversion factors discussed in ISO/ASTM Guide.4.5 During calibration and use, possible effects of influencequantities such as temperature, light exposure, post-irradiationstabilization of signal, and absorbed-dose rate need to be takeninto account.4.6 Photo-fluorescent dosimeters are sens

49、itive to light, es-pecially during irradiation and post-irradiation stabilization (7).Some color centers are sensitive to the UV and blue regions ofthe spectrum, while other centers are only sensitive to the UV.Therefore, they need to be packaged in appropriate light-tightpackaging shortly after manufacture, and during use they needto be packaged or the appropriate filters placed over roomlighting. Filtering the light fixtures involved during irradiationmay be required for irradiations using low-energy X-rays orelectrons where unpackag