ASTM E2861-11
(Test Method)Standard Test Method for Measurement of Beam Divergence and Alignment in Neutron Radiologic Beams
Standard Test Method for Measurement of Beam Divergence and Alignment in Neutron Radiologic Beams
SIGNIFICANCE AND USE
As discussed in Practice E748, traditional neutron radiography typically employs a high flux reactor source with a well defined collimation system to produce an image on film. The alignment of the imaging plane and the divergence angle are generally well defined and a small degree of misalignment or uncertainty in divergence angle makes little difference in the final image. These systems are well characterized by their physical dimension, the L/D ratio, and image quality indicators (Beam Purity Indicator and Sensitivity Indicator) described in Test Method E545. Neutron computed tomography is an example where it is important to know with some precision both the beam’s centerline and the degree of beam divergence, especially if the beam does not closely approximate a parallel beam. Portable or movable neutron imaging systems often utilize shorter collimation systems, a less precise alignment and poor symmetry in divergence angles, which may affect image analysis. In these example cases, direct measurement of the alignment and the divergence angles is desirable as calculation from system geometry would be less straightforward and accurate. Fabrication of the device is an extension of the Test Method E803 L/D device, providing different information through a similar approach.
SCOPE
1.1 This test method covers the design, materials, manufacture, and use of a divergence and alignment indicator (DAI) for measuring the effective divergence of a thermal neutron beam used for neutron imaging as well as determining the alignment of the 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 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 responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: E2861 − 11
StandardTest Method for
Measurement of Beam Divergence and Alignment in
Neutron Radiologic Beams
This standard is issued under the fixed designation E2861; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 3. Terminology
3.1 Definitions—For definitions of terms used in this guide
1.1 This test method covers the design, materials,
other than those defined in this section, refer to Terminology
manufacture, and use of a divergence and alignment indicator
E1316.
(DAI) for measuring the effective divergence of a thermal
neutron beam used for neutron imaging as well as determining
3.2 Definitions:
the alignment of the imaging plane relative (usually normal) to
3.2.1 neutron image—record in two dimensions of the
the centerline of the beam. This test method is applicable to
intensity of neutron radiation. Examples include radiographs,
thermal neutron imaging. radioscopic images, and track etch images produced from a
neutron source.
1.2 The values stated in SI units are to be regarded as the
3.2.2 neutron imaging—process of making a neutron image.
standard.
4. Summary of Test Method
1.3 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
4.1 The DAI allows the user to determine the alignment of
responsibility of the user of this standard to establish appro-
the imaging plane with the beam centerline and the beam
priate safety and health practices and determine the applica-
divergenceforathermalneutronbeam.Theusercandetermine
bility of regulatory limitations prior to use.
if the imaging system is aligned, aligned only in one direction
or completely misaligned and the angle of misalignment, as
2. Referenced Documents
well as the divergence angle for the imaging system. The DAI
2 is made using aluminum plate and rods, and incorporates
2.1 ASTM Standards:
cadmium wires for contrast. Circular symmetry is utilized to
E543 Specification forAgencies Performing Nondestructive
simplify manufacture. An important feature of the DAI is
Testing
flexibility to adapt the “as-built” dimensions into the analysis.
E545 Test Method for Determining Image Quality in Direct
The DAI is placed with the five stand off posts against the film
Thermal Neutron Radiographic Examination
cassette or radioscopic imaging device in the physical center of
E748 Practices for Thermal Neutron Radiography of Mate-
thebeam.TheDAIisperpendiculartotheselectedbeamradius
rials
when the center S1 and center S4 cadmium wire images
E803 TestMethodforDeterminingthe L/DRatioofNeutron
overlap (see Figs. 1 and 2).The degree of misalignment can be
Radiography Beams
measured by the cadmium wire image positions.After the DAI
E1316 Terminology for Nondestructive Examinations
is aligned, analysis of the cadmium wire “+” image spacing
2.2 Other Documents:
yields the beam divergence.
ANSI Y14.5M Dimensioning and Tolerances
5. Significance and Use
5.1 As discussed in Practice E748, traditional neutron radi-
1 ography typically employs a high flux reactor source with a
This test method is under the jurisdiction of ASTM Committee E07 on
Nondestructive Testing and is the direct responsibility of Subcommittee E07.05 on
well defined collimation system to produce an image on film.
Radiology (Neutron) Method.
The alignment of the imaging plane and the divergence angle
Current edition approved Dec. 1, 2011. Published January 2012. DOI:10.1520/
are generally well defined and a small degree of misalignment
E2861-11.
or uncertainty in divergence angle makes little difference in the
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
final image. These systems are well characterized by their
Standards volume information, refer to the standard’s Document Summary page on
physical dimension, the L/D ratio, and image quality indicators
the ASTM website.
(Beam Purity Indicator and Sensitivity Indicator) described in
Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
4th Floor, New York, NY 10036, http://www.ansi.org. Test Method E545. Neutron computed tomography is an
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E2861 − 11
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 end
of 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.
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 Figs. 1 and 2 are all paral-
lel.
example where it is important to know with some precision especially if the beam does not closely approximate a parallel
both the beam’s centerline and the degree of beam divergence, beam. Portable or movable neutron imaging systems often
E2861 − 11
utilize shorter collimation systems, a less precise alignment tion of radiographs may allow higher precision measurements,
and poor symmetry in divergence angles, which may affect a vernier caliper can alternately be utilized to take measure-
image analysis. In these example cases, direct measurement of ments from a film radiograph.
the alignment and the divergence angles is desirable as
NOTE 1—If using a vernier caliper and film, a clear sheet of plastic can
calculation from system geometry would be less straightfor-
be placed between the film and caliper to prevent damage to the film.
ward and accurate. Fabrication of the device is an extension of
9.2 Neutron images of the DAI device must be taken under
the Test Method E803 L/D device, providing different infor-
the conditions of interest (with the same collimation system,
mation through a similar approach.
imageplanedistance,etc.)andtheDAIpositionedasdescribed
in Section 12. For film-based images, Practice E748 describes
6. Basis of Application
the standard practice for thermal neutron radiography of
6.1 If specified in the contractual agreement, personnel
materials.
performing examinations to this standard shall be qualified in
accordance with a nationally or internationally recognized 10. Preparation of Apparatus
NDT personnel qualification practice or standard such as
10.1 Circular symmetry is utilized to simplify manufacture
ANSI/ASNT-CP-189, SNT-TC-1A, NAS-410 or a similar
and assembly of the device. The DAI is illustrated in Fig. 3
document and certified by the employer or certifying agency,
with device dimensions. An important feature of the DAI is
as applicable. The practice or standard used and its applicable
flexibility to adapt the “as-built” dimensions into the analysis.
revision shall be identified in the contractual agreement be-
Therefore, a high degree of dimensional accuracy is not
tween the using parties.
required in either the cadmium wire or in the fabrication of the
6.2 Qualification of Nondestructive Agencies—If specified machinedparts,however,theplatemustbestraight(adiameter
in the contractual agreement, NDT agencies shall be qualified tolerance zone of 1.0 mm), otherwise the minor differences in
and evaluated as described in Specification E543. The appli- height will lead to discrepancies in the data. The degree of
cable edition of Specification E543 shall be specified in the accuracy in the calculated alignment and divergence angles
contractual agreement. depends on the accuracy of measurement of the “as-built”
dimensions and the features observed in the neutron image of
6.3 Procedures and Techniques—The procedures and tech-
the DAI. Device construction is adapted from Ref. (1).
niques to be utilized shall be as specified in this standard.
10.2 DAI Device Construction:
6.4 Reporting Criteria—Reporting criteria for the examina-
10.2.1 Machine a disk 22.0-cm in diameter from 0.30-cm
tion results shall be in accordance with Section 14 unless
thick aluminum plate. See Fig. 3. The maximum variation
otherwise specified. Since acceptance criteria are not specified
across the plate must be under 1.0 mm. Any deviation in
in this standard, they shall be specified in the contractual
distance from the imaging device to surface S1 results in an
agreement.
increase in uncertainty in calculated divergence angles.
10.2.2 Cut 44 pieces of 0.5-mm diameter by 1-cm long
7. Materials
cadmium wire and 80 pieces of 0.5-mm diameter by 0.5-cm
7.1 The DAI is made using aluminum plate, rod, and screws
long cadmium wire. Although the exact diameter of the
to minimize neutron attenuation and long-lived induced radio-
cadmium wire is not critical, all groove’s dimensions and holes
activity. An aluminum alloy such as Al 6061 or Al 1100 is
drilled for cadmium wire must be adjusted to fit the actual wire
suitable for device construction. Cadmium wire and thin
dimension, for example, depth and radius of the groove should
cadmium sheet (0.5 mm is appropriate) are incorporated for
matchtheradiusofthewiretoensurethewirefitstightlyinthe
contrast, the exact diameter of the cadmium wire is not critical,
groove and the grove’s widest point is at the S1 surface.
but all groove dimensions and holes drilled for the cadmium
10.2.3 Machine five grooves of 0.25-mm radius, 0.25-mm
must be adjusted to fit the actual wire diameter. Cadmium wire
deep, at 2.0, 4.0, 6.0, 8.0 and 10.0-cm radii in one side of the
below 1.0 mm in diameter is suitable for use.
22.0-cm disk from 10.2.1. The side with the grooves will now
be called the S1 surface of the DAI. See Fig. 3 and Fig. 2.
8. Hazards
NOTE 2—The accuracy of the groove positions affects the accuracy of
8.1 Since cadmium can represent a safety concern, the
the DAI.
Material Safety Data Sheet (MSDS) for cadmium should be
10.2.4 Machine four grooves of 0.25-mm radius, 0.25-mm
reviewed and safe handling practices followed.
deep, across the diameter of the 22.0-cm disk from 10.2.1 on
8.2 Radiation hazards exist when operating radiation imag-
the S1 surface. Each groove should be at 45° as shown in Fig.
ing systems. The activity of the DAI should be measured prior
3.
to handling or transporting following use as some activation
will occur during imaging. NOTE 3—The accuracy of the groove positions affects the accuracy of
the DAI.
9. Sampling, Test Specimens, and Test Units
10.2.5 Machine four grooves of 0.25-mm radius, 0.25-mm
9.1 Distances on the images can best be measured digitally deep, on surface S1 to fit the cadmium wire from 10.2.2 of
using the “as built” distance between the images of the stand appropriate size to hold the “L” and “T” orientation markers as
off posts on the S4 surface of the device to determine the depicted in Fig. 3a. The exact position and size are not
distance each pixel represents in the image. Though digitiza- important as they are only for reference.
E2861 − 11
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 positions.
10.2.6 Machine five aluminum posts 1.25 cm in diameter flat-head aluminum screws. Check that the posts are perpen-
and 5.0 cm in length, making sure the faces of the posts are dicular to the S2 surface.
finished perpendicular to the post length.
10.2.13 FromtheS1surfaceofthe22.0-cmdisk,drillahole
10.2.7 Obtain five flat-head aluminum machine screws
for a cadmium wire from 10.2.10 in the exact center of the
about 1.3 cm in length. The diameter of the screw is not
center post mounting screw, making sure the hole is drilled
critical, but should be approximately 0.6 cm in diameter.
perpendicular to the disk surface.
10.2.8 Orient the S1 surface of the 22.0-cm diameter plate
10.2.14 Insert a piece of cadmium wire from 10.2.10 into
such that one groove machined in 10.2.4 is vertical relative to
the hole drilled into the center post mounting screw in 10.2.13
your position. The position of the posts and screws are
(S1 surface) and four of the holes in the stand off posts (S4
illustrated in Fig. 3 and Fig. 2, respectively. Drill appropriate
surface), leaving the center post empty. A small amount of
through holes for the screws of 10.2.7 in the center of the plate
neutron transparent epoxy or glue can be used to secure the
and at a radius of 7.07 cm in the 45°, 135°, 225°, and 315°
cadmium wire if it is loose.
grooves machined in 10.2.4. On surface S1 of the disk, counter
10.2.15 Cut a small piece of cadmium from a 0.5-mm thick
sinktheholesforthescrewheadssuchthatthescrewheadsare
sheet. Cut the piece such that its cross section is square and it
flush with the S1 surface.
will fit into the unfilled center post hole from 10.2.11 (S4
10.2.9 Drill and tap one end of each post from 10.2.6 for the
surface).
screws from 10.2.7, making sure the tapped holes are perpen-
NOTE 4—The square shape of the cadmium piece in the S4 surface will
dicular to the post face. This end of the post will be referred to
permit differentiation between S1 and S4 cadmium pieces in the radio-
as the S3 surface.
graphic image.
10.2.10 Cut five pieces of 0.5-mm diameter cadmium wire
10.2.16 Insert the square cadmium piece from 10.2.15 into
each 0.3 cm long.
the center post hole in the S4 surface left empty in 10.2.14.A
10.2.11 Drill a hole for the cadmium wire from 10.2.10 in
small amount of neutron transparent epoxy or glue can be used
the center of each post opposite the tapped hole, making sure
to secure the cadmium piece if it is loose.
theholesareperpendiculartothepostface.Thisendofthepost
will be referred to as the S4 surface.
NOTE 5—Be careful not to fill the hole with a neutron attenuating
10.2.12 Mount the S3 surface of the posts to the S2 surface
adhesive which would prevent differentiation between S1 and S4 surface
of the 22.0-cm disk (the surface without the grooves) using the cadmium pieces on the DAI image.
E2861 − 11
10.2.17 At each groove intersection on the S1 surface of the the device, (possibly the result of warping or poor construc-
22.0-cm disk, except at the center, secure a “+” made from one tion) the accuracy will be significantly degraded.
1.0-cm piece of cadmium wire and two 0.5-cm pieces of
12. Procedure
cadmiumwirefrom10.2.2.Usethe1.0-cmpieceinthecircular
groove and two 0.5-cm piec
...
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