ASTM E803-17 Standard Test Method for Determining the LD Ratio of Neutron Radiography Beams.pdf
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1、Designation: E803 17Standard Test Method forDetermining the L/D Ratio of Neutron Radiography Beams1This standard is issued under the fixed designation E803; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision.
2、 A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This test method defines an empirical technique for themeasurement of the effective collimation ratio, L/D, of neutronradiography b
3、eams. The technique is based upon analysis of aneutron radiographic image and is independent of measure-ments and calculations based on physical dimensions of thecollimation system. The values derived by this techniqueshould be more accurate than those based on physicalmeasurements, particularly for
4、 poorly defined apertures.1.2 This test method covers both the manufacture and use ofthe device to measure L/D ratios.1.3 Neutron images for this method can be produced onradiographic film using an appropriate conversion screen asdetailed in Guide E748 or a CR screen with appropriateneutron converte
5、r. The method has not been validated withimages produced by digital detector arrays.1.4 This test method only applies to neutron beam lines withcold or thermal neutron spectrums.1.5 The values stated in SI units are to be regarded asstandard.1.6 This standard does not purport to address all of thesa
6、fety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety, health, and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.7 This international standard was developed in accor-da
7、nce with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM St
8、andards:2E748 Guide for Thermal Neutron Radiography of MaterialsE1316 Terminology for Nondestructive Examinations3. Summary of Test Method3.1 Determination of neutron beam L/D ratio (length of thebeam line divided by the diameter of the aperture) using theNU (no umbra) technique3is accomplished by r
9、adiographingthe NU device with the neutron beam to be measured andsubsequently analyzing the resulting image by one of threemethods. Each of the three methods is based upon thedetermination of that point at which the umbral shadow widthreaches zero. See Fig. 1. The neutron radiography method isdiscu
10、ssed in Guide E748 and the terms are defined in Termi-nology E1316.4. Significance and Use4.1 The quality of a neutron radiographic image is depen-dent upon many factors. The L/D ratio is one of those factorsand constitutes a numerical definition of the geometry of theneutron beam. The L/D ratio req
11、uired for a specific neutronradiographic examination is dependent upon the thickness ofthe specimen and the physical characteristics of the particularelement of interest. Use of this test method allows theradiographer and the user to determine and periodically mea-sure the effective collimation rati
12、o.5. Apparatus5.1 The NU Device (see Fig. 2(a) and (b), and Fig. 3)employs neutron absorbing rods positioned at various distancesfrom the image plane. In practice this device consists ofcadmium rods located in V-grooves accurately machined in the1This test method is under the jurisdiction of Committ
13、ee E07 on NondestructiveTesting and is the direct responsibility of Subcommittee E07.05 on Radiology(Neutron) Method.Current edition approved Nov. 1, 2017. Published November 2017. Originallyapproved in 1986. Last previous edition approved in 2013 as E803 91(2013). DOI:10.1520/E0803-17.2For referenc
14、ed 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.3Newacheck, R. L., and Underhill, P. E., “The NU Method for Determining L/
15、DRatio Of Neutron Radiography Facilities,” Aerotest Operations, Inc., Report A.O.77-27, June 1977.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international stand
16、ard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1surfac
17、e of an aluminum channel section set at a 45 614 angleto the side support plate. Near the image plane end theV-grooves are machined on 0.283-cm centers. After 21V-grooves, counting one on the end, the grooves are machinedon 0.707-cm centers to the source end. The 0.64-mm diametercadmium rods are lai
18、d into the V-grooves and secured withneutron transparent adhesive tape. The aluminum channel issupported by side plates to maintain the 45 614 anglerelative to the image plane. Nylon rods included in the groovesadjacent to the cadmium rods are present in some devices.These nylon rods are not used in
19、 L/D calculations, nor do theydetract from the function of the device, and so are consideredoptional.5.2 A single A unit or B unit as shown in Fig. 2(b) and Fig.3 can be used for L/D values expected to be less than 150,while multiple device segments can be used in combination tomeasure larger L/D ra
20、tios.Alternately, a singleAor B unit usedwith appropriate spacers may be used to accommodate a widerange of L/D values when using the methods described in 7.1or 7.3 to establish the collimation ratio.6. Procedure6.1 Align the plane of the imaging device perpendicular tothe axis of the neutron beam.6
21、.2 Insert spacers of known thickness, if required.6.3 Place the NU device against the imaging device (orspacers) with the finely spaced rods nearest the imaging deviceif using an A unit.6.4 Film Procedure:6.4.1 Expose the single-emulsion film and NU device for atime span that will produce a nominal
22、background film densityof 2.5 6 0.4.6.4.2 Process the exposed film in accordance with themanufacturers recommendations.6.4.3 Analyze the resultant image in accordance with one ormore of the three methods outlined in Section 7.6.4.4 Digitization of film (optional) should be performedwith a transmissi
23、on scanner. A minimum of 300 dpi forscanning is required. Accuracy is improved considerably at orabove 600 dpi.FIG. 1 Diagram of Zero Umbra Image ConfigurationNOTE 1Rods at “A” positions are 1 cm each side of center line (22 ea.)NOTE 2Rods at “B” positions are 2 cm each side of center line (9 ea.)NO
24、TE 3Rods at “C” positions are 2.5 cm each side of center line (1 ea.)NOTE 4All dimensions from base line to reduce accumulative errorsNOTE 5Rod arrangement shown for single system device. For an add-on device, to form a double system, extend the 11 spaces for 7.78 cm to 19spaces for 13.43 cm and eli
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