1、Designation: E2861 11Standard Test Method forMeasurement of Beam Divergence and Alignment inNeutron Radiologic Beams1This standard is issued under the fixed designation E2861; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the yea
2、r 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 test method covers the design, materials, manufac-ture, and use of a divergence and alignment indicator (DAI
3、) formeasuring the effective divergence of a thermal neutron beamused for neutron imaging as well as determining the alignmentof the imaging plane relative (usually normal) to the centerlineof the beam. This test method is applicable to thermal neutronimaging.1.2 The values stated in SI units are to
4、 be regarded as thestandard.1.3 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-bility of regulatory limitations
5、prior to use.2. Referenced Documents2.1 ASTM Standards:2E543 Specification for Agencies Performing Nondestruc-tive TestingE545 Test Method for Determining Image Quality in DirectThermal Neutron Radiographic ExaminationE748 Practices for Thermal Neutron Radiography of Mate-rialsE803 Test Method for D
6、etermining the L/D Ratio of Neu-tron Radiography BeamsE1316 Terminology for Nondestructive Examinations2.2 Other Documents:ANSI Y14.5M Dimensioning and Tolerances33. Terminology3.1 DefinitionsFor definitions of terms used in this guideother than those defined in this section, refer to TerminologyE13
7、16.3.2 Definitions:3.2.1 neutron imagerecord in two dimensions of theintensity of neutron radiation. Examples include radiographs,radioscopic images, and track etch images produced from aneutron source.3.2.2 neutron imagingprocess of making a neutron image.4. Summary of Test Method4.1 The DAI allows
8、 the user to determine the alignment ofthe imaging plane with the beam centerline and the beamdivergence for a thermal neutron beam. The user can determineif the imaging system is aligned, aligned only in one directionor completely misaligned and the angle of misalignment, aswell as the divergence a
9、ngle for the imaging system. The DAIis made using aluminum plate and rods, and incorporatescadmium wires for contrast. Circular symmetry is utilized tosimplify manufacture. An important feature of the DAI isflexibility to adapt the “as-built” dimensions into the analysis.The DAI is placed with the f
10、ive stand off posts against the filmcassette or radioscopic imaging device in the physical center ofthe beam. The DAI is perpendicular to the selected beam radiuswhen the center S1 and center S4 cadmium wire imagesoverlap (see Figs. 1 and 2). The degree of misalignment can bemeasured by the cadmium
11、wire image positions. After the DAIis aligned, analysis of the cadmium wire “+” image spacingyields the beam divergence.5. Significance and Use5.1 As discussed in Practice E748, traditional neutron radi-ography typically employs a high flux reactor source with awell defined collimation system to pro
12、duce an image on film.The alignment of the imaging plane and the divergence angleare generally well defined and a small degree of misalignmentor uncertainty in divergence angle makes little difference in thefinal image. These systems are well characterized by theirphysical dimension, the L/D ratio,
13、and image quality indicators1This test method is under the jurisdiction of ASTM Committee E07 onNondestructive Testing and is the direct responsibility of Subcommittee E07.05 onRadiology (Neutron) Method.Current edition approved Dec. 1, 2011. Published January 2012. DOI:10.1520/E2861-11.2For referen
14、ced 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 American National Standards Institute (ANSI), 25 W. 43rd
15、St.,4th Floor, New York, NY 10036, http:/www.ansi.org.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.(Beam Purity Indicator and Sensitivity Indicator) described inTest Method E545. Neutron computed tomography is anexample where it i
16、s important to know with some precisionboth the beams centerline and the degree of beam divergence,FIG. 1 Image of the DAI device with added labels to label the S2 surface as the un-grooved side of the plate, the S3 surface as the endof the stand off post that is mounted to surface S2, and S4, the e
17、nd of the stand off post to be positioned at the imaging plane.FIG. 2 Image of the S1 surface of a DAI device (with added S1 label), showing grooves, cadmium crosses, and aluminum screw heads.This device used tape to hold the cadmium wire crosses in place. The surfaces S1, S2, S3, and S4 shown in Fi
18、gs. 1 and 2 are allparallel.E2861 112especially if the beam does not closely approximate a parallelbeam. Portable or movable neutron imaging systems oftenutilize shorter collimation systems, a less precise alignmentand poor symmetry in divergence angles, which may affectimage analysis. In these exam
19、ple cases, direct measurement ofthe alignment and the divergence angles is desirable ascalculation from system geometry would be less straightfor-ward and accurate. Fabrication of the device is an extension ofthe Test Method E803 L/D device, providing different infor-mation through a similar approac
20、h.6. Basis of Application6.1 If specified in the contractual agreement, personnelperforming examinations to this standard shall be qualified inaccordance with a nationally or internationally recognizedNDT personnel qualification practice or standard such asANSI/ASNT-CP-189, SNT-TC-1A, NAS-410 or a s
21、imilardocument and certified by the employer or certifying agency,as applicable. The practice or standard used and its applicablerevision shall be identified in the contractual agreement be-tween the using parties.6.2 Qualification of Nondestructive AgenciesIf specifiedin the contractual agreement,
22、NDT agencies shall be qualifiedand evaluated as described in Specification E543. The appli-cable edition of Specification E543 shall be specified in thecontractual agreement.6.3 Procedures and TechniquesThe procedures and tech-niques to be utilized shall be as specified in this standard.6.4 Reportin
23、g CriteriaReporting criteria for the examina-tion results shall be in accordance with Section 14 unlessotherwise specified. Since acceptance criteria are not specifiedin this standard, they shall be specified in the contractualagreement.7. Materials7.1 The DAI is made using aluminum plate, rod, and
24、screwsto minimize neutron attenuation and long-lived induced radio-activity. An aluminum alloy such as Al 6061 or Al 1100 issuitable for device construction. Cadmium wire and thincadmium sheet (0.5 mm is appropriate) are incorporated forcontrast, the exact diameter of the cadmium wire is not critica
25、l,but all groove dimensions and holes drilled for the cadmiummust be adjusted to fit the actual wire diameter. Cadmium wirebelow 1.0 mm in diameter is suitable for use.8. Hazards8.1 Since cadmium can represent a safety concern, theMaterial Safety Data Sheet (MSDS) for cadmium should bereviewed and s
26、afe handling practices followed.8.2 Radiation hazards exist when operating radiation imag-ing systems. The activity of the DAI should be measured priorto handling or transporting following use as some activationwill occur during imaging.9. Sampling and Test Specs and Units9.1 Distances on the images
27、 can best be measured digitallyusing the “as built” distance between the images of the standoff posts on the S4 surface of the device to determine thedistance each pixel represents in the image. Though digitiza-tion of radiographs may allow higher precision measurements,a vernier caliper can alterna
28、tely be utilized to take measure-ments from a film radiograph.NOTE 1If using a vernier caliper and film, a clear sheet of plastic canbe placed between the film and caliper to prevent damage to the film.9.2 Neutron images of the DAI device must be taken underthe conditions of interest (with the same
29、collimation system,image plane distance, etc.) and the DAI positioned as describedin Section 12. For film-based images, Practice E748 describesthe standard practice for thermal neutron radiography ofmaterials.10. Preparation of Apparatus10.1 Circular symmetry is utilized to simplify manufactureand a
30、ssembly of the device. The DAI is illustrated in Fig. 3with device dimensions. An important feature of the DAI isflexibility to adapt the “as-built” dimensions into the analysis.Therefore, a high degree of dimensional accuracy is notrequired in either the cadmium wire or in the fabrication of themac
31、hined parts, however, the plate must be straight (a diametertolerance zone of 1.0 mm), otherwise the minor differences inheight will lead to discrepancies in the data. The degree ofaccuracy in the calculated alignment and divergence anglesdepends on the accuracy of measurement of the “as-built”dimen
32、sions and the features observed in the neutron image ofthe DAI. Device construction is adapted from Ref. (1).10.2 DAI Device Construction:10.2.1 Machine a disk 22.0-cm in diameter from 0.30-cmthick aluminum plate. See Fig. 3. The maximum variationacross the plate must be under 1.0 mm. Any deviation
33、indistance from the imaging device to surface S1 results in anincrease in uncertainty in calculated divergence angles.10.2.2 Cut 44 pieces of 0.5-mm diameter by 1-cm longcadmium wire and 80 pieces of 0.5-mm diameter by 0.5-cmlong cadmium wire. Although the exact diameter of thecadmium wire is not cr
34、itical, all grooves dimensions and holesdrilled for cadmium wire must be adjusted to fit the actual wiredimension, for example, depth and radius of the groove shouldmatch the radius of the wire to ensure the wire fits tightly in thegroove and the groves widest point is at the S1 surface.10.2.3 Machi
35、ne five grooves of 0.25-mm radius, 0.25-mmdeep, at 2.0, 4.0, 6.0, 8.0 and 10.0-cm radii in one side of the22.0-cm disk from 10.2.1. The side with the grooves will nowbe called the S1 surface of the DAI. See Fig. 3 and Fig. 2.NOTE 2The accuracy of the groove positions affects the accuracy ofthe DAI.1
36、0.2.4 Machine four grooves of 0.25-mm radius, 0.25-mmdeep, across the diameter of the 22.0-cm disk from 10.2.1 onthe S1 surface. Each groove should be at 45 as shown in Fig.3.NOTE 3The accuracy of the groove positions affects the accuracy ofthe DAI.10.2.5 Machine four grooves of 0.25-mm radius, 0.25
37、-mmdeep, on surface S1 to fit the cadmium wire from 10.2.2 ofappropriate size to hold the “L” and “T” orientation markers asdepicted in Fig. 3a. The exact position and size are notimportant as they are only for reference.E2861 11310.2.6 Machine five aluminum posts 1.25 cm in diameterand 5.0 cm in le
38、ngth, making sure the faces of the posts arefinished perpendicular to the post length.10.2.7 Obtain five flat-head aluminum machine screwsabout 1.3 cm in length. The diameter of the screw is notcritical, but should be approximately 0.6 cm in diameter.10.2.8 Orient the S1 surface of the 22.0-cm diame
39、ter platesuch that one groove machined in 10.2.4 is vertical relative toyour position. The position of the posts and screws areillustrated in Fig. 3 and Fig. 2, respectively. Drill appropriatethrough holes for the screws of 10.2.7 in the center of the plateand at a radius of 7.07 cm in the 45, 135,
40、225, and 315grooves machined in 10.2.4. On surface S1 of the disk, countersink the holes for the screw heads such that the screw heads areflush with the S1 surface.10.2.9 Drill and tap one end of each post from 10.2.6 for thescrews from 10.2.7, making sure the tapped holes are perpen-dicular to the
41、post face. This end of the post will be referred toas the S3 surface.10.2.10 Cut five pieces of 0.5-mm diameter cadmium wireeach 0.3 cm long.10.2.11 Drill a hole for the cadmium wire from 10.2.10 inthe center of each post opposite the tapped hole, making surethe holes are perpendicular to the post f
42、ace. This end of the postwill be referred to as the S4 surface.10.2.12 Mount the S3 surface of the posts to the S2 surfaceof the 22.0-cm disk (the surface without the grooves) using theflat-head aluminum screws. Check that the posts are perpen-dicular to the S2 surface.10.2.13 From the S1 surface of
43、 the 22.0-cm disk, drill a holefor a cadmium wire from 10.2.10 in the exact center of thecenter post mounting screw, making sure the hole is drilledperpendicular to the disk surface.10.2.14 Insert a piece of cadmium wire from 10.2.10 intothe hole drilled into the center post mounting screw in 10.2.1
44、3(S1 surface) and four of the holes in the stand off posts (S4surface), leaving the center post empty. A small amount ofneutron transparent epoxy or glue can be used to secure thecadmium wire if it is loose.10.2.15 Cut a small piece of cadmium from a 0.5-mm thicksheet. Cut the piece such that its cr
45、oss section is square and itwill fit into the unfilled center post hole from 10.2.11 (S4surface).NOTE 4The square shape of the cadmium piece in the S4 surface willpermit differentiation between S1 and S4 cadmium pieces in the radio-graphic image.10.2.16 Insert the square cadmium piece from 10.2.15 i
46、ntothe center post hole in the S4 surface left empty in 10.2.14.Asmall amount of neutron transparent epoxy or glue can be usedto secure the cadmium piece if it is loose.FIG. 3 Diagram of the DAI Device Showing the Cadmium Pieces in Solid Black: (a) the S1 surface with machined grooves anddimensions
47、in centimetres, and (b) different orientation illustrates post positions.E2861 114NOTE 5Be careful not to fill the hole with a neutron attenuatingadhesive which would prevent differentiation between S1 and S4 surfacecadmium pieces on the DAI image.10.2.17 At each groove intersection on the S1 surfac
48、e of the22.0-cm disk, except at the center, secure a “+” made from one1.0-cm piece of cadmium wire and two 0.5-cm pieces ofcadmium wire from 10.2.2. Use the 1.0-cm piece in the circulargroove and two 0.5-cm pieces in the radial grooves as shownin Fig. 4. The wire may be secured with a small amount o
49、fneutron transparent epoxy, glue or tape. See Fig. 3 for the crosslocations.10.2.18 Using the remaining four cadmium wires from10.2.2, make an “L” and “T” at the locations shown in Fig. 3in the grooves from 10.2.5. Affix the wire with a small amountof neutron transparent epoxy, glue or tape.11. Calibration and Standardization11.1 To calibrate the device and ensure no bias exists,precise measurement of the devices “as built” dimensions anduse of these measured values in calculations (rather then thosespecified for device construction) is required. Specifically
