1、Designation: E 1654 94 (Reapproved 2004)Standard Guide forMeasuring Ionizing Radiation-Induced Spectral Changes inOptical Fibers and Cables for Use in Remote RamanFiberOptic Spectroscopy1This standard is issued under the fixed designation E 1654; the number immediately following the designation indi
2、cates 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 (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This guide covers the method for measurin
3、g the realtime, in situ radiation-induced alterations to the Raman spectralsignal transmitted by a multimode, step index, silica opticalfiber. This guide specifically addresses steady-state ionizingradiation (that is, alpha, beta, gamma, protons, etc.) withappropriate changes in dosimetry, and shiel
4、ding considerations,depending upon the irradiation source.1.2 The test procedure given in this guide is not intended totest the other optical and non-optical components of an opticalfiber-based Raman sensor system, but may be modified to testother components in a continuous irradiation environment.1
5、.3 The values in SI units are to be regarded as standard.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-bili
6、ty of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E 1614 Guide for Procedure for Measuring IonizingRadiation-Induced Attenuation in Silica-Based Optical Fi-bers and Cables for Use in Remote Fiber-Optic Spectros-copy and Broadband Systems2.2 EIA Standards:2.2.1 Test
7、 or inspection requirements include the followingreferences:EIA-455-57 Optical Fiber End Preparation and Examina-tion3EIA-455-64 Procedure for Measuring Radiation-InducedAttenuation in Optical Fibers and Cables32.3 Military Standard:MIL-STD-2196-(SH) Glossary of Fiber Optic Terms43. Terminology3.1 D
8、efinitionsRefer to the following documents for thedefinition of terms used in this guide: MIL-STD-2196-(SH)and E 1614.4. Significance and Use4.1 Ionizing environments will affect the performance ofoptical fibers/cables being used to transmit spectroscopicinformation from a remote location. Determina
9、tion of the typeand magnitude of the spectral variations or interferencesproduced by the ionizing radiation in the fiber, or both, isnecessary for evaluating the performance of an optical fibersensor system.4.2 The results of the test can be utilized as a selectioncriteria for optical fibers used in
10、 optical fiber Raman spectro-scopic sensor systems.NOTE 1The attenuation of optical fibers generally increases whenthey are exposed to ionizing radiation.This is due primarily to the trappingof radiolytic electrons and holes at defect sites in the optical materials, thatis, the formation of color ce
11、nters. The depopulation of these color centersby thermal or optical (photobleaching) processes, or both, causes recov-ery, usually resulting in a decrease in radiationinduced attenuation.Recovery of the attenuation after irradiation depends on many variables,including the temperature of the test sam
12、ple, the composition of thesample, the spectrum and type of radiation employed, the total doseapplied to the test sample, the light level used to measure the attenuation,and the operating spectrum. Under some continuous conditions, recoveryis never complete.5. Apparatus5.1 The test schematic is show
13、n in Fig. 1. The following listidentifies the equipment necessary to accomplish this testprocedure.5.2 Light SourceA laser source shall be used for theRaman analysis, and the wavelength must be chosen so that thefluorescent signals from the optical components (especially the1This guide is under the
14、jurisdiction of ASTM Committee E13 on MolecularSpectroscopy and is the direct responsibility of Subcommittee E13.09 on FiberOptics in Molecular Spectroscopy.Current edition approved Nov. 1, 2004. Published January 2005. Originallyapproved in 1994. Last previous version approved in 1999 as E 165494 (
15、1999).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.3Available from Electronic Industry Association, Engine
16、ering Dept., 2001Pennsylvania Ave., NW, Washington, DC 20006.4Available from Standardization Documents Order Desk, Bldg. 4 Section D, 700Robbins Ave., Philadelphia, PA 19111-5094, Attn: NPODS.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United
17、States.spectral activator sample and optical fibers) are minimized, andso that the wavelength corresponds to the spectral sensitivity ofthe detection scheme. Typically, the wavelength range ex-ploited spans from 0.4 to 1.06 m. The laser source must havesufficient power to obtain the desired minimum
18、signal-to-noiseratio (S/N) (see 10.3).5.3 Focusing/Collection OpticsA number of optical ele-ments are needed for the launch and collection of lightradiation into and from the optical fibers (interfacing, sampleand reference), and other instrumentation (light source, spec-trograph, detector). The min
19、imal requirement for these ele-ments shall be that the numerical aperture of the componentsFIG. 1 Test ConfigurationE 1654 94 (2004)2are matched for efficient coupling. Optics may also be neces-sary to enhance the interaction of the input light with thespectral activator.5.4 Interfacing Optical Fibe
20、rThe primary requirement ofthe interfacing optical fiber is to provide the minimum powerto the activator sample at the proper wavelength(s). The fiberlength may be adjusted so that the power requirements are met.5.5 Light Radiation FilteringIt is important that all neigh-boring laser lines are remov
21、ed from the source beam prior tointeraction with the spectral activator. This can be accom-plished before or after the interfacing optical fiber. Placementof the filter before the interfacing fiber will eliminate theneighboring laser lines, but any fluorescence and Ramanscattering due to the fiber o
22、r associated optics will be allowedto interact with the sample. Placement of the laser pass filterafter the interfacing fiber is preferable because it will eliminateany signals created within the fiber. If it is necessary to placethe filter before the interfacing fiber, then the fiber should bekept
23、as short as possible (several metres).5.6 Spectral Activator SampleThe spectral activator usedmust demonstrate a strong, well-characterized Raman spectralsignal. The sample may be either liquid, gas, or solid, depend-ing on the requirements of the optical fiber arrangement. It isrecommended that a l
24、iquid be used, since the Raman scatteringin the proposed configuration will launch similarly into thesample and reference fibers. Standard recommended samplesare: acetonitrile, benzene, and carbon tetrachloride.The sampleshould be contained in a standard spectroscopic rectangularsilica cuvette.5.7 O
25、ptical InterconnectionsThe input and output ends ofthe interfacing, reference, and sample optical fibers shall havea stabilized optical interconnection, such as a clamp, connector,splice, or weld. During an attenuation measurement, theinterconnection shall not be changed or adjusted.5.8 Irradiation
26、SystemThe irradiation system should havethe following characteristics:5.8.1 Dose RateACo60or other irradiation source shall beused to deliver radiation at dose rates ranging from 10 to 100Gy (SiO2)/min. (See Note 2.)5.8.2 Radiation EnergyThe energy of the gamma raysemitted by the source should be gr
27、eater than 500 KeV to avoidserious complications with the rapid variations in total dose asa function of depth within the test sample.5.8.3 Radiation DosimeterDosimetry traceable to Na-tional Standards shall be used. Dose should be measured in thesame uniform geometry as the actual fiber core materi
28、al toensure that dose-buildup effects are comparable to the fibercore and the dosimeter. The dose should be expressed in graycalculated for the core material.5.9 Temperature-Controlled ContainerUnless otherwisespecified, the temperature-controlled container shall have thecapability of maintaining th
29、e specified temperature to 23 62C. The temperature of the sample/container should bemonitored prior to and during the test.5.10 Collection Optics into Detection SystemAn appro-priate collection configuration shall be used at the distal end ofthe sample and reference optical fibers. It is recommended
30、 thatthe collection and focusing optic(s) is f/number matched to thenumerical aperture of the fibers and detection system.5.10.1 Raman analysis requires that the laser line be elimi-nated prior to detection.Alaser reject (or long pass filter) mustbe used at the entrance to the detection system. The
31、filtershould pass all energy at 500 cm1below the laser excitationline. The filter should be placed between the optical elementsprior to the spectrometer.5.11 Optical DetectionAn optical detector with a knownresponse over the range of intensities that are encountered shallbe used. A typical system fo
32、r Raman might include a single-point detector (that is, PMT) or a multichannel analyzer (thatis, CCD array). The spectrograph must exhibit fast scanningcapabilities. As Fig. 1 indicates, it is recommended that asingle-imaging spectrometer be used with a 2D CCD detectorso that the output from the ref
33、erence and sample fibers can beevaluated simultaneously. Two spectrometers operating simul-taneously may also be used.5.11.1 The optical detection system must be capable ofobtaining the Raman spectrum from 500 to 3000 cm1from theexcitation frequency.5.12 Recorder SystemA suitable data recording, suc
34、h as acomputer data acquisition system, is recommended.5.13 Ambient Light ShieldingThe irradiated fiber lengthshall be shielded from ambient light to prevent photobleachingby any external light sources and to avoid baseline shifts in thezero light level. An absorbing fiber coating or jacket can beus
35、ed as the light shield provided that it has been demonstratedto block ambient light and its influence on the dose within thefiber core has been taken into consideration.NOTE 2The average total dose should be expressed in gray (Gy,where 1 Gy = 100 rads) to a precision of 65 %, traceable to nationalst
36、andards. For typical silica core fibers, dose should be expressed in graycalculated for SiO2, that is, Gy(SiO2).6. Hazards6.1 Carefully trained and qualified personnel must be usedto perform this test procedure since radiation (both ionizingand optical), as well as electrical, hazards will be presen
37、t.7. Test Specimens7.1 Sample Optical FiberThe sample fiber shall be apreviously unirradiated step-index, multimode fiber. The fibershall be long enough to have an irradiated test length of 50 65 m and to allow coupling between the optical instrumentationoutside the radiation chamber and the sample
38、area.7.2 The test specimen may be an optical-fiber cable assem-bly, as long as the cable contains at least one of the specifiedfibers for analysis.7.3 Test ReelThe test reel shall not act as a shield for theradiation used in this test or, alternatively, the dose must bemeasured in a geometry duplica
39、ting the effects of reel attenu-ation. The diameter of the test reel and the winding tension ofthe fiber can influence the observed radiation performance,therefore, the fiber should be loosely wound on a reel diameterexceeding 10 cm.7.4 Fiber End PreparationPrepare the test sample suchthat its end f
40、aces are smooth and perpendicular to the fiber axis,in accordance with EIA-455-57.E 1654 94 (2004)37.5 Reference FiberThe reference fiber shall have thesame requirements as the sample fiber. It should have similarcharacteristics, be packaged in the same configuration, andshould be used in an identic
41、al fashion as the sample fiberexcept for the radiation exposure.8. Radiation, Calibration, and Stability8.1 Calibration of Radiation SourceMake calibration ofthe radiation source for dose uniformity and dose level at thelocation of the device under test (DUT) and at a minimum offour other locations,
42、 prior to introduction of fiber test samples.The variation in dose across the fiber reel volume shall notexceed 610 %. If thermoluminescent detectors (TLDs) areused for the measurements, use four TLDs to sample dosedistribution at each location. Average the readings from themultiple TLDs at each loc
43、ation to minimize dose uncertainties.To maintain the highest possible accuracy in dose measure-ments, do not use the TLDs more than once. TLDs should beused only in the dose region where they maintain a linearresponse.8.2 Measure the total dose with an irradiation time equal tosubsequent fiber measu
44、rements. Alternatively, the dose ratemay be measured and the total dose calculated from theproduct of the dose rate and irradiation time. Source transittime (from off-to-on and on-to-off positions) shall be less than5 % of the irradiation time.8.3 Stability of Radiation SourceThe dose rate must beco
45、nstant for at least 95 % of the shortest irradiation time ofinterest. The dose variation provided across the fiber sampleshall not exceed 610 %.9. System Stability and Calibration9.1 System StabilityThe stability of the total system underillumination conditions, including the light source, light inj
46、ec-tion conditions into the interfacing fiber, variation in fibermicrobend conditions, light coupling from the spectral activa-tor to the sample and reference fibers, light coupling to adetector/spectrometer, the detector, the recording device, andthe sample temperature must be verified prior to any
47、 measure-ment.9.1.1 The intensity (counts per second) detected from thesample and reference fibers prior to irradiation shall be within10 %.9.2 Baseline StabilityVerify the baseline stability for atime comparable to the attenuation measurement with the lightsource turned off. Record the maximum fluc
48、tuation in outputpower and reject any subsequent measurement if the transmit-ted power out of the irradiated fiber is not greater than ten timesthe recorded baseline.10. Procedure10.1 Place the reel of fiber or cable in the attenuation testsetup as shown in Fig. 1. Couple the light source into the e
49、ndof the interfacing fiber.10.2 Position the output end of the interfacing fiber suchthat all the light exiting the fiber impinges the spectral activatorsample. Position the sample and reference fibers to collect thespectral energy scattered (see Note 3).10.3 Position the light exiting the fibers for collection by thedetection scheme. The spectra obtained through the sample andreference fibers must exhibit a minimum signal-to-noise ratio(S/N) of 9 prior to irradiation for the primary Raman peaks (seeNote 4).10.4 Stabilize the test sample in the temperat
