1、Designation: E 2304 03An American National StandardStandard Practice forUse of a LiF Photo-Fluorescent Film Dosimetry System1This standard is issued under the fixed designation E 2304; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision
2、, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) 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
3、-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 have been used
4、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 Absorbed dose range
5、 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 This standard does not pur
6、port 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:E 1
7、70 Terminology Relating to Radiation Measurementsand Dosimetry3E 275 Practice for Describing and Measuring Performanceof Ultraviolet, Visible, and Near Infrared Spectrophotom-eters4E 925 Practice for the Periodic Calibration of Narrow Band-Pass Spectrophotometers42.2 ISO/ASTM Standards:51204 Practic
8、e for Dosimetry in Gamma Irradiation Facili-ties for Food Processing351261 Guide for Selection and Calibration of DosimetrySystems for Radiation Processing351431 Practice for Dosimetry in Electron and Bremsstrahl-ung Irradiation Facilities for Food Processing351608 Practice for Dosimetry in an X-ray
9、 (Bremsstrahlung)Facility for Radiation Processing351649 Practice for Dosimetry in an Electron Beam Facilityfor Radiation Processing at Energies between 300 keV and25 MeV351702 Practice for Dosimetry in a Gamma Irradiation Fa-cility for Radiation Processing351707 Guide for Estimating Uncertainties i
10、n Dosimetry forRadiation Processing351818 Practice for Dosimetry in an Electron Beam Facilityfor Radiation Processing at Energies between 80 keV and300 keV351956 Practice for Thermoluminescence-Dosimetry (TLD)Systems for Radiation Processing32.3 International Commission on Radiation Units andMeasure
11、ments (ICRU) Reports:5ICRU Report 14 Radiation Dosimetry: X-rays and Gammarays with Maximum Photon Energies Between 0.6 and 50MeVICRU Report 17 Radiation Dosimetry: X-rays Generated atPotentials of 5 to 150 kVICRU Report 34 The Dosimetry of Pulsed RadiationICRU Report 35 Radiation Dosimetry: Electro
12、n Beams withEnergies Between 1 and 50 MeVICRU Report 60 Fundamental Quantities and Units forIonizing Radiation3. 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
13、 gray isequivalent to the absorption of 1 joule per kilogram of the1This practice is under the jurisdiction of ASTM Committee E10 on NuclearTechnology and Applications and is the direct responsibility of SubcommitteeE10.01 on Dosimetry for Radiation Processing.Current edition approved July 10, 2003.
14、 Published October 2003.2The boldface numbers in parentheses refer to the list of references at the end ofthis standard.3Annual Book of ASTM Standards, Vol 12.02.4Annual Book of ASTM Standards, Vol 03.06.5Available from International Commission on Radiation Units and Measure-ments, 7910 Woodmont Ave
15、., Suite 800, Bethesda, MD 20814, USA.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.specified material (1 Gy = 1 J kg-1). The mathematical rela-tionship is the quotient of deby dm, where deis the meanincremental energy imparted by
16、ionizing radiation to matter ofincremental mass dm (see ICRU 60).D 5dedm3.1.1.1 DiscussionAbsorbed dose is sometimes referredto simply as dose. For a photon source under conditions ofcharged particle-equilibrium, the absorbed dose, D, may beexpressed as:D 5fEenrwhere:f = particle fluence (m-2),E = e
17、nergy of the ionizing radiation (J), anden/r = mass energy absorption coefficient (m2kg-1).If bremsstrahlung production within the specified material isnegligible, the mass energy absorption coefficient (en/r)isequal to the mass energy transfer coefficient (tr/r), andabsorbed dose is equal to kerma
18、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 analysis wavelengthwavelength used in a s
19、pectro-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-tion source and its associated instrume
20、ntation 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 calibrationcurve.3.1.5 charged-particle
21、 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 (for example, negative-or positive-ion v
22、acancies) 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 material with uniform composition, fab
23、ricatedin a single production run under controlled, consistent condi-tions, 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 standards, and proceduresfor the sys
24、tems use.3.1.9 electron equilibriumcharged particle equilibriumfor electrons.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 fill an electron hole, resulting in t
25、he 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.3.1.11 fluorescence signal, Efthe ph
26、otometric reading bya spectrofluorimeter 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, Vcm-2orAcm-2).3.1.12 fluorescence
27、 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 sample upon excita-tion by an energ
28、y 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, was added to distinguish irradiance
29、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, thermoluminescence, and photolumines-cen
30、ce.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, nationally or internationally recog
31、-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.3.1.18 net fluorescence, DEfmeasured f
32、luorescence 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 dosim-eter, which upon excitation by visible or UV light, emitsfluorescent light.3.1.20 primary-standard dosimeterdosimeter
33、 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, measure-ment, or process is performed to a pre
34、defined level of quality.E23040323.1.22 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 (steradians).Has units of W m-2sr-1. See
35、 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 by the user.3.1.25 transfer-stan
36、dard 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.3.1.26.1 DiscussionIn the case
37、 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 individualrecord.3.2 Definitions of o
38、ther terms used in this standard thatpertain to radiation measurement and dosimetry may be foundin Terminology E 170. Definitions in Terminology E 170 arecompatible with ICRU 60; that document, therefore, may beused as an alternative reference.4. Significance and Use4.1 A lithium fluoride (LiF)-base
39、d 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. Imperfections within the ionic lattic
40、e 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 form of visible-light photon
41、s. 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 can cover a range of wavelength
42、s, 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 wavelengths that are desired for use.
43、 Theories on how colorcenters are formed, how luminescence mechanisms work, andtheir 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
44、 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 doses.These absorbed
45、 doses span the range of utilization of thesystem.4.3 Photo-fluorescent dosimetry 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 conver
46、sion factors discussed in ISO/ASTM Guide51261.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 DosimeterE23040334.5 During calibration and use, possible effects of influencequantitie
47、s 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 color centers are sensitive to the U
48、V 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 fixtu
49、res 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 eitherincreases or decreases with time following irradiation, depend-ing on the color center utilized (19). This stabilization process,which can last from hours to days depending on storagetemperature (and dose for some color centers) can be acceler-ated and stabilized by heat treating the dosimeters afterirradiation and before readout (see 9.2).5. Apparatus5.1
