ANSI ASTM E2304-2003 Standard Practice for Use of a LiF Photo-Fluorescent Film Dosimetry System.pdf

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1、Designation: E2304 03 (Reapproved 2011)Standard 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 case of revision, the year of

2、 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 (LiF)-based photo-fluorescent f

3、ilmdosimetry 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 have been used for dosimetry f

4、or 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 Absorbed dose range of510-2to3102k

5、Gy (1-3).21.2.2 Absorbed dose rate range of 0.3 to2104Gy/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 stated in SI units are to be regarded as

6、standard. 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 and health practices and determine the

7、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 Performance ofUltraviolet and Visible SpectrophotometersE925 Practice for Monitoring the Calibra

8、tion 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 Radiation Processing51431 Practice for

9、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 Energies between 300 keVand25 MeV51702 Pr

10、actice for Dosimetry in a Gamma Irradiation Facil-ity 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 keV and300 keV51956 Practice for Thermol

11、uminescence-Dosimetry (TLD)Systems for Radiation Processing2.3 International Commission on Radiation Units and Mea-surements (ICRU) Reports:4ICRU Report 14 Radiation Dosimetry: X-rays and Gammarays with Maximum Photon Energies Between 0.6 and 50MeVICRU Report 17 Radiation Dosimetry: X-rays Generated

12、 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 jurisdiction of ASTM Committee E61 on Radia

13、tionProcessingand is the direct responsibility of Subcommittee E61.02 on DosimetrySystems.Current edition approved Nov. 1, 2011. Published November 2011. Originallyapproved in 2003. Last previous edition approved in 2003 as E2304-03. DOI:10.1520/E2304-03R11.2The boldface numbers in parentheses refer

14、 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.4Availa

15、ble from International Commission on Radiation Units andMeasurements, 7910 Woodmont Ave., Suite 800, Bethesda, MD 20814, USA.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13. Terminology3.1 Definitions:3.1.1 absorbed dose, Dquantity

16、of ionizing radiation en-ergy imparted per unit mass of a specified material. The SI unitof absorbed dose is the gray (Gy), where 1 gray is equivalentto the absorption of 1 joule per kilogram of the specifiedmaterial (1 Gy = 1 J kg-1). The mathematical relationship is thequotient of d by dm, where d

17、 is the mean incremental energyimparted by ionizing radiation to matter of incremental massdm (see ICRU 60).D 5ddm3.1.1.1 DiscussionAbsorbed dose is sometimes referred tosimply as dose. For a photon source under conditions ofcharged particle-equilibrium, the absorbed dose, D, may beexpressed as:D 5

18、Eenwhere: = particle fluence (m-2),E = energy of the ionizing radiation (J), anden/ = mass energy absorption coefficient (m2kg-1).If bremsstrahlung production within the specified material isnegligible, the mass energy absorption coefficient (en/)isequal to the mass energy transfer coefficient (tr/)

19、, 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, and astatine) and an alkali metal (for example, lithium,sodium, and potassium).3.1.3 anal

20、ysis 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, reflectance orluminescence.3.1.4 calibration facilitycombination of an ionizing radia-ti

21、on 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 specific material, and that may be used toderive the dosimetry systems response function or ca

22、librationcurve.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) entering the volume are equal to those leaving thevolume.3.1.6 color centerimperfections (fo

23、r 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 produce luminescence.3.1.7 dosimeter batchquantity of dosimeters made from aspecific mass of m

24、aterial with uniform composition, fabricatedin a single production run under controlled, consistentconditions, and having a unique identification code.3.1.8 dosimetry systemsystem used for determining ab-sorbed dose, consisting of dosimeters, measurement instru-ments and their associated reference s

25、tandards, and proceduresfor the systems use.3.1.9 electron equilibriumcharged particle equilibrium forelectrons.3.1.10 fluorescenceone of the four main luminescencemechanisms. In many materials, it involves the liberatedelectrons falling back to the valence banddirectly or via arelaxation stateto fi

26、ll 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, and subsequently fall back to thecenters ground state, resulting in the release of a photon.3

27、.1.11 fluorescence signal, Efthe photometric reading by aspectrofluorimeter in terms of light intensity incident on thephotodetector. Typically, the value measured is some quantityproportional to the standardized quantity, irradiance, Ei(forexample, volts or amperes per unit area of detector surface

28、, 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 fluorimeterinstrument used to measure the amountof fluorescence signal, Ef, emitted from a

29、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.NOTE 1The standard symbol for irradiance is E; however, for thisdocument the subscript, i, wa

30、s 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 a form ofenergy. The main luminescence mechanisms are fluorescence,phosphorescence, thermo

31、luminescence, 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-ments of the specific application.This plan requires traceabilityto, and consistency with, na

32、tionally 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 limits of uncer-tainty with comparable nationally or internationally recognizedstandards.3.1.1

33、8 net fluorescence, Efmeasured fluorescence signal,Ef, from an irradiated sample, subtracted by the pre-irradiationfluorescence, Eo, as follows:Ef5 Ef2 EoE2304 03 (2011)23.1.19 photo-fluorescent film dosimetera film-typedosimeter, which upon excitation by visible or UV light, emitsfluorescent light.

34、3.1.20 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 quality assuranceall systematic actions necessaryto provide adequate confidence that a calibration,measu

35、rement, or process is performed to a predefined level ofquality.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 of projected area of the surface (m2)asviewed from that direction, per unit of solid angle (steradia

36、ns).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 with, measurements madeusing primary-standard dosimeters.3.1.24 stockpart of a dosimeter batch, held b

37、y 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 verificationconfirmation by examination of objec-tive evidence that specified requirements have been met

38、.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 cases it is required that a written trace of theverification performed be kept on the instruments indivi

39、dualrecord.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 ICRU 60; that document, therefore, may beused as an alternative reference.4. Significance and Use4.1

40、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 the stimulation wavelength. Theabsorbed dose is obtained from the amount of the lightemission. Imperfec

41、tions 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 centers because of the part theyplay in the compounds ability to absorb and then releaseenergy in the

42、 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 intensity is transferred to thematerial. The resulting fluorescence spectra contain discretepeaks that ca

43、n 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 light-detecting instrument(that is, fluorimeter) can be used to block all but a narrow rangeof wavelengt

44、hs that are desired for use. Theories on how colorNOTE 1Also 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)3centers are formed, how luminescence mechanisms work, an

45、dtheir application in dosimetry are found in Refs (8-13). Forcharacterization studies on specific photo-fluorescent dosim-eters see Refs (1-7) and (14-19).4.2 In the application of a specific dosimetry system,absorbed dose is determined by use of an experimentally-derived calibration curve. The cali

46、bration curve for the photo-fluorescent dosimeter is the functional relationship betweenEfand D, and is determined by measuring the net fluores-cence of sets of dosimeters irradiated to known absorbed doses.These absorbed doses span the range of utilization of thesystem.4.3 Photo-fluorescent dosimet

47、ry systems require calibrationtraceable to national standards. See ISO/ASTM Guide 51261.4.4 The absorbed dose is usually specified relative to water.Absorbed dose in other materials may be determined byapplying the conversion factors discussed in ISO/ASTM Guide51261.4.5 During calibration and use, p

48、ossible 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 sensitive to light, es-pecially during irradiation and post-irradiation stabilization (7).Some

49、 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 unpackaged dosimeters are used.4.7 The signal from photo-fluorescent dosimeters eithe