1、Designation: E2861 11E2861 16Standard 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,
2、 the year 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. Scope Scope*1.1 This test method covers the design, materials, manufacture, and use of a divergence and alignment
3、indicator (DAI) formeasuring the effective divergence of a thermal neutron beam used for neutron imaging as well as determining the alignment ofthe imaging plane relative (usually normal) to the centerline of the beam.This test method is applicable to thermal neutron imaging.1.2 The values stated in
4、 SI units are to be regarded as the standard.1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulat
5、orylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E543 Specification for Agencies Performing Nondestructive TestingE545 Test Method for Determining Image Quality in Direct Thermal Neutron Radiographic ExaminationE748 Guide for Thermal Neutron Radiography of MaterialsE803 Test Me
6、thod for Determining the L/D Ratio of Neutron Radiography BeamsE1316 Terminology for Nondestructive Examinations2.2 Other Documents:ANSI Y14.5M Dimensioning and Tolerances33. Terminology3.1 DefinitionsFor definitions of terms used in this guide other than those defined in this section, refer to Term
7、inology E1316.3.2 Definitions:3.2.1 neutron imagerecord in two dimensions of the intensity of neutron radiation. Examples include radiographs, radioscopicimages, computed radiography (CR) images, and track etch images produced from a neutron source.3.2.2 neutron imagingprocess of making a neutron im
8、age.4. Summary of Test Method4.1 The DAI allows the user to determine the alignment of the imaging plane with the beam centerline and the beam divergencefor a thermal neutron beam. The user can determine if the imaging system is aligned, aligned only in one direction or completelymisaligned and the
9、angle of misalignment, as well as the divergence angle for the imaging system. The DAI is made usingaluminum plate and rods, and incorporates cadmium wires for contrast. Circular symmetry is utilized to simplify manufacture.Animportant feature of the DAI is flexibility to adapt the “as-built” dimens
10、ions into the analysis. The DAI is placed with the five standoff posts against the film cassette or radioscopic imaging device in the physical center of the beam. The DAI is perpendicular to1 This test method is under the jurisdiction of ASTM Committee E07 on Nondestructive Testing and is the direct
11、 responsibility of Subcommittee E07.05 on Radiology(Neutron) Method.Current edition approved Dec. 1, 2011June 1, 2016. Published January 2012June 2016. DOI:10.1520/E2861-11. Originally approved in 2011. Last previous editionapproved as E2861-11. DOI:10.1520/E2861-16.2 For referencedASTM standards, v
12、isit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.3 Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New
13、York, NY 10036, http:/www.ansi.org.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM reco
14、mmends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C7
15、00, West Conshohocken, PA 19428-2959. United States1the selected beam radius when the center S1 and center S4 cadmium wire images overlap (see Figs. 1 and 2). The degree ofmisalignment can be measured by the cadmium wire image positions. After the DAI is aligned, analysis of the cadmium wire “+”imag
16、e spacing yields the beam divergence.5. Significance and Use5.1 As discussed in Practice E748, traditional neutron radiography typically employs a high flux reactor source with a welldefined collimation system to produce an image on film.The alignment of the imaging plane and the divergence angle ar
17、e generallywell defined and a small degree of misalignment or uncertainty in divergence angle makes little difference in the final image. Thesesystems are well characterized by their physical dimension, the L/D ratio, and image quality indicators (Beam Purity Indicator andSensitivity Indicator) desc
18、ribed in Test Method E545. Neutron computed tomography is an example where it is important to knowwith some precision both the beams centerline and the degree of beam divergence, especially if the beam does not closelyapproximate a parallel beam. Portable or movable neutron imaging systems often uti
19、lize shorter collimation systems, a less precisealignment and poor symmetry in divergence angles, which may affect image analysis. In these example cases, direct measurementof the alignment and the divergence angles is desirable as calculation from system geometry would be less straightforward andac
20、curate. Fabrication of the device is an extension of the Test Method E803 L/D device, providing different information througha similar approach.6. Basis of Application6.1 If specified in the contractual agreement, personnel performing examinations to this standard shall be qualified inaccordance wit
21、h a nationally or internationally recognized NDT personnel qualification practice or standard such as ANSI/ASNT-CP-189, SNT-TC-1A, NAS-410 or a similar document and certified by the employer or certifying agency, as applicable. Thepractice or standard used and its applicable revision shall be identi
22、fied in the contractual agreement between the using parties.6.2 Qualification of Nondestructive AgenciesIf specified in the contractual agreement, NDT agencies shall be qualified andevaluated as described in Specification E543. The applicable edition of Specification E543 shall be specified in the c
23、ontractualagreement.6.3 Procedures and TechniquesThe procedures and techniques to be utilized shall be as specified in this standard.6.4 Reporting CriteriaReporting criteria for the examination results shall be in accordance with Section 14 unless otherwisespecified. Since acceptance criteria are no
24、t specified in this standard, they shall be specified in the contractual agreement.7. Materials7.1 The DAI is made using aluminum plate, rod, and screws to minimize neutron attenuation and long-lived inducedradioactivity.An aluminum alloy such asAl 6061 orAl 1100 is suitable for device construction.
25、 Cadmium wire and thin cadmiumFIG. 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 end of the stand off post to be positioned at the imaging plane.E2861
26、162sheet (0.5 mm is appropriate) are incorporated for contrast, the exact diameter of the cadmium wire is not critical, but all groovedimensions and holes drilled for the cadmium must be adjusted to fit the actual wire diameter. Cadmium wire below 1.0 mm indiameter is suitable for use.8. Hazards8.1
27、Since cadmium can represent a safety concern, the Material Safety Data Sheet (MSDS) for cadmium should be reviewedand safe handling practices followed.8.2 Radiation hazards exist when operating radiation imaging systems. The activity of the DAI should be measured prior tohandling or transporting fol
28、lowing use as some activation will occur during imaging.9. Sampling, Test Specimens, and Test Units9.1 Distances on the images can best be measured digitally using the “as built” distance between the images of the stand offposts on the S4 surface of the device to determine the distance each pixel re
29、presents in the image. Though For images on film,digitization of the radiographs may allow higher precision measurements, but a vernier caliper can alternately be utilized to takemeasurements from a film the radiograph.NOTE 1If using a vernier caliper and film, a clear sheet of plastic can be placed
30、 between the film and caliper to prevent damage to the film.9.2 Neutron images of the DAI device must be taken under the conditions of interest (with the same collimation system, imageplane distance, etc.) and the DAI positioned as described in Section 12. For film-based images, Practice E748 descri
31、bes thestandard practice for thermal neutron radiography of materials.10. Preparation of Apparatus10.1 Circular symmetry is utilized to simplify manufacture and assembly of the device. The DAI is illustrated in Fig. 3 withdevice dimensions. An important feature of the DAI is flexibility to adapt the
32、 “as-built” dimensions into the analysis. Therefore,a high degree of dimensional accuracy is not required in either the cadmium wire or in the fabrication of the machined parts,FIG. 2 Image of the S1 surface of a DAI device (with added S1 label), showing grooves, cadmium crosses, and aluminum screw
33、heads.This device used tape to hold the cadmium wire crosses in place. The surfaces S1, S2, S3, and S4 shown in Figs. 1 and 2 are all paral-lel.E2861 163however, the plate must be straight (a diameter tolerance zone of 1.0 mm), otherwise the minor differences in height will lead todiscrepancies in t
34、he data. The degree of accuracy in the calculated alignment and divergence angles depends on the accuracy ofmeasurement of the “as-built” dimensions and the features observed in the neutron image of the DAI. Device construction isadapted from Ref. (1).10.2 DAI Device Construction:10.2.1 Machine a di
35、sk 22.0-cm in diameter from 0.30-cm thick aluminum plate. See Fig. 3. The maximum variation across theplate must be under 1.0 mm. Any deviation in distance from the imaging device to surface S1 results in an increase in uncertaintyin calculated divergence angles.10.2.2 Cut 44 pieces of 0.5-mm diamet
36、er by 1-cm long cadmium wire and 80 pieces of 0.5-mm diameter by 0.5-cm longcadmium wire. Although the exact diameter of the cadmium wire is not critical, all grooves dimensions and holes drilled forcadmium wire must be adjusted to fit the actual wire dimension, for example, depth and radius of the
37、groove should match theradius of the wire to ensure the wire fits tightly in the groove and the groves widest point is at the S1 surface.10.2.3 Machine five grooves of 0.25-mm radius, 0.25-mm deep, at 2.0, 4.0, 6.0, 8.0 and 10.0-cm radii in one side of the 22.0-cmdisk from 10.2.1. The side with the
38、grooves will now be called the S1 surface of the DAI. See Fig. 3 and Fig. 2.NOTE 2The accuracy of the groove positions affects the accuracy of the DAI.10.2.4 Machine four grooves of 0.25-mm radius, 0.25-mm deep, across the diameter of the 22.0-cm disk from 10.2.1 on the S1surface. Each groove should
39、 be at 45 as shown in Fig. 3.NOTE 3The accuracy of the groove positions affects the accuracy of the DAI.10.2.5 Machine four grooves of 0.25-mm radius, 0.25-mm deep, on surface S1 to fit the cadmium wire from 10.2.2 ofappropriate size to hold the “L” and “T” orientation markers as depicted in Fig. 3a
40、. The exact position and size are not importantas they are only for reference.10.2.6 Machine five aluminum posts 1.25 cm in diameter and 5.0 cm in length, making sure the faces of the posts are finishedperpendicular to the post length.10.2.7 Obtain five flat-head aluminum machine screws about 1.3 cm
41、 in length. The diameter of the screw is not critical, butshould be approximately 0.6 cm in diameter.FIG. 3 Diagram of the DAI Device Showing the Cadmium Pieces in Solid Black: (a) the S1 surface with machined grooves and dimen-sions in centimetres, and (b) different orientation illustrates post pos
42、itions.E2861 16410.2.8 Orient the S1 surface of the 22.0-cm diameter plate such that one groove machined in 10.2.4 is vertical relative to yourposition. The position of the posts and screws are illustrated in Fig. 3 and Fig. 2, respectively. Drill appropriate through holes forthe screws of 10.2.7 in
43、 the center of the plate and at a radius of 7.07 cm in the 45, 135, 225, and 315 grooves machined in10.2.4. On surface S1 of the disk, counter sink the holes for the screw heads such that the screw heads are flush with the S1 surface.10.2.9 Drill and tap one end of each post from 10.2.6 for the scre
44、ws from 10.2.7, making sure the tapped holes are perpendicularto the post face. This end of the post will be referred to as the S3 surface.10.2.10 Cut five pieces of 0.5-mm diameter cadmium wire each 0.3 cm long.10.2.11 Drill a hole for the cadmium wire from 10.2.10 in the center of each post opposi
45、te the tapped hole, making sure the holesare perpendicular to the post face. This end of the post will be referred to as the S4 surface.10.2.12 Mount the S3 surface of the posts to the S2 surface of the 22.0-cm disk (the surface without the grooves) using theflat-head aluminum screws. Check that the
46、 posts are perpendicular to the S2 surface.10.2.13 From the S1 surface of the 22.0-cm disk, drill a hole for a cadmium wire from 10.2.10 in the exact center of the centerpost mounting screw, making sure the hole is drilled perpendicular to the disk surface.10.2.14 Insert a piece of cadmium wire from
47、 10.2.10 into the hole drilled into the center post mounting screw in 10.2.13 (S1surface) and four of the holes in the stand off posts (S4 surface), leaving the center post empty. A small amount of neutrontransparent epoxy or glue can be used to secure the cadmium wire if it is loose.10.2.15 Cut a s
48、mall piece of cadmium from a 0.5-mm thick sheet. Cut the piece such that its cross section is square and it willfit into the unfilled center post hole from 10.2.11 (S4 surface).NOTE 4The square shape of the cadmium piece in the S4 surface will permit differentiation between S1 and S4 cadmium pieces
49、in the radiographicimage.10.2.16 Insert the square cadmium piece from 10.2.15 into the center post hole in the S4 surface left empty in 10.2.14. A smallamount of neutron transparent epoxy or glue can be used to secure the cadmium piece if it is loose.NOTE 5Be careful not to fill the hole with a neutron attenuating adhesive which would prevent differentiation between S1 and S4 surface cadmiumpieces on the DAI image.10.2.17 At each groove intersection on the S1 surface of the 22.0-cm disk, except at the center, secure a “+” made from one1.0-cm piece of cadmium
