ASTM E545-19

Standard Test Method for Determining Image Quality in Direct Thermal Neutron Radiographic Examination

SIGNIFICANCE AND USE
5.1 The BPI is designed to yield quantitative information concerning neutron beam and image system parameters that contribute to film exposure and thereby affect overall image quality. In addition, the BPI can be used to verify the day-to-day consistency of the neutron radiographic quality. Gadolinium conversion screens and single-emulsion silver-halide films, exposed together in the neutron imaging beam, were used in the development and testing of the BPI. Use of alternative detection systems may produce densitometric readings that are not valid for the equations used in Section 9.  
5.2 The only truly valid sensitivity indicator is a reference standard part. A reference standard part is a material or component that is the same as the object being neutron radiographed except with a known standard discontinuity, inclusion, omission, or flaw. The sensitivity indicators were designed to substitute for the reference standard and provide qualitative information on hole and gap sensitivity.  
5.3 The number of areas or objects to be radiographed and the film acceptance standard used should be specified in the contract, purchase order, specification, or drawings.
SCOPE
1.1 This test method covers the use of an Image Quality Indicator (IQI) system to determine the relative2 quality of radiographic images produced by direct, thermal neutron radiographic examination. The requirements expressed in this test method are not intended to control the quality level of materials and components.  
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 30-Apr-2019
• ICS: 19.100 - Non-destructive testing
• Technical Committee: E07 - Nondestructive Testing
• Drafting Committee: E07.05 - Radiology (Neutron) Method

Relations

• Replaces: ASTM E545-14 - Standard Test Method for Determining Image Quality in Direct Thermal Neutron Radiographic Examination
• Effective Date: 01-May-2019
• Refers: ASTM E1316-24 - Standard Terminology for <?Pub Dtl?>Nondestructive Examinations
• Effective Date: 01-Feb-2024
• Refers: ASTM E803-20 - Standard Test Method for Determining the <emph type="ital">L/D&#x2009;</emph>Ratio of Neutron Radiography Beams
• Effective Date: 01-Jul-2020
• Refers: ASTM E1316-19b - Standard Terminology for Nondestructive Examinations
• Effective Date: 01-Dec-2019
• Refers: ASTM E748-19 - Standard Guide for Thermal Neutron Radiography of Materials
• Effective Date: 01-May-2019
• Refers: ASTM E1316-19 - Standard Terminology for Nondestructive Examinations
• Effective Date: 01-Mar-2019
• Refers: ASTM E1316-18 - Standard Terminology for Nondestructive Examinations
• Effective Date: 01-Jan-2018
• Refers: ASTM E803-17 - Standard Test Method for Determining the <emph type="ital">L/D&#x2009;</emph>Ratio of Neutron Radiography Beams
• Effective Date: 01-Nov-2017
• Refers: ASTM E1316-17a - Standard Terminology for Nondestructive Examinations
• Effective Date: 15-Jun-2017
• Refers: ASTM E1316-17 - Standard Terminology for Nondestructive Examinations
• Effective Date: 01-Feb-2017
• Refers: ASTM E1316-16a - Standard Terminology for Nondestructive Examinations
• Effective Date: 01-Aug-2016
• Refers: ASTM E748-16 - Standard Guide for Thermal Neutron Radiography of Materials
• Effective Date: 15-Feb-2016
• Refers: ASTM E1316-16 - Standard Terminology for Nondestructive Examinations
• Effective Date: 01-Feb-2016
• Refers: ASTM E1316-15a - Standard Terminology for Nondestructive Examinations
• Effective Date: 01-Dec-2015
• Refers: ASTM E1316-15 - Standard Terminology for Nondestructive Examinations
• Effective Date: 01-Sep-2015

Overview

ASTM E545-19: Standard Test Method for Determining Image Quality in Direct Thermal Neutron Radiographic Examination is an internationally recognized guideline published by ASTM International. This standard defines procedures for assessing image quality in direct, thermal neutron radiographic examination using image quality indicators (IQIs)-specifically, a Beam Purity Indicator (BPI) and a Sensitivity Indicator (SI). These indicators are essential for verifying and quantifying the performance of neutron radiographic imaging systems, supporting consistency and reliability in non-destructive testing (NDT).

Key Topics

• Image Quality Indicators (IQIs):

  • Beam Purity Indicator (BPI): Provides quantitative data on neutron beam and image system parameters, impacting overall film exposure and image quality. The BPI consists of components such as boron nitride disks, metallic lead, and cadmium or gadolinium wires.
  • Sensitivity Indicator (SI): Qualitatively assesses the radiographic sensitivity to holes and gaps, substituting as a reference standard when actual flawed parts are unavailable.

• Radiographic Examination Procedure:

  • Use of gadolinium conversion screens and single-emulsion silver-halide films for image generation.
  • Proper placement and orientation of BPI and SI on radiographs to avoid overlap and ensure accurate measurement.
  • Measurement of film densities using calibrated densitometers.

• Evaluation Metrics:

  • Determination of exposure contributors, including thermal neutron content, scattered neutron content, gamma content, and pair production content.
  • Assignment of image category based on quantitative and qualitative analysis, supporting standardized comparison across facilities.

• Process Control Radiographs:

  • Requirements for additional radiographs to verify conformity when standard indicator placement or density conditions cannot be met.

• Certification and Record Keeping:

  • Mandates for certification of compliance upon request and maintenance of detailed examination records for defined periods.

Applications

The ASTM E545-19 standard is vital for organizations and agencies that rely on non-destructive testing (NDT) using thermal neutron radiography. Typical sectors applying this method include:

• Aerospace: Inspection of structural components and detection of internal flaws.
• Nuclear Industry: Verification of material integrity in nuclear fuel and reactor components.
• Defense and Military: Quality assessment of critical safety components.
• Research Facilities: Consistent, repeatable evaluation of experimental results in neutron imaging.

By standardizing the process, ASTM E545-19 ensures reproducibility and defensibility of results. It is especially useful for:

• Confirming day-to-day consistency of neutron radiographic imaging systems.
• Specifying film acceptance and examination requirements in contracts and technical documentation.
• Objectively measuring and comparing the effectiveness of different imaging systems and operational procedures across multiple facilities.

Related Standards

ASTM E545-19 references several related ASTM standards which support its implementation and broaden its context within NDT, including:

• ASTM E543: Specification for Agencies Performing Nondestructive Testing.
• ASTM E748: Guide for Thermal Neutron Radiography of Materials.
• ASTM E803: Test Method for Determining the L/D Ratio of Neutron Radiography Beams.
• ASTM E1079: Practice for Calibration of Transmission Densitometers.
• ASTM E2003: Practice for Fabrication of the Neutron Radiographic Beam Purity Indicators.
• ASTM E2023: Practice for Fabrication of Neutron Radiographic Sensitivity Indicators.
• ASTM E1316: Terminology for Nondestructive Examinations.

By following ASTM E545-19 and its referenced standards, organizations ensure compliance with internationally recognized NDT best practices, maintain quality assurance across projects, and meet contractual, regulatory, and safety requirements related to neutron radiographic imaging.

Keywords: ASTM E545-19, neutron radiography, image quality indicator, beam purity indicator, sensitivity indicator, non-destructive testing, NDT, radiographic examination, gadolinium conversion screen, film density, thermal neutron content.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation:E545 −19
Standard Test Method for
Determining Image Quality in Direct Thermal Neutron
Radiographic Examination
This standard is issued under the fixed designation E545; 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.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope* Radiography Beams
E1079 Practice for Calibration of Transmission Densitom-
1.1 This test method covers the use of an Image Quality
2 eters
Indicator (IQI) system to determine the relative quality of
E1316 Terminology for Nondestructive Examinations
radiographic images produced by direct, thermal neutron
E2003 Practice for Fabrication of the Neutron Radiographic
radiographic examination. The requirements expressed in this
Beam Purity Indicators
test method are not intended to control the quality level of
E2023 Practice for Fabrication of Neutron Radiographic
materials and components.
Sensitivity Indicators
1.2 The values stated in SI units are to be regarded as
standard. No other units of measurement are included in this
3. Terminology
standard.
3.1 Definitions—For definitions of terms used in this test
1.3 This standard does not purport to address all of the
method, see Terminology E1316, Section H.
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
4. Summary of Test Method
priate safety, health, and environmental practices and deter-
4.1 The judgment of the quality of a neutron radiograph is
mine the applicability of regulatory limitations prior to use.
based upon the evaluation of images obtained from indicators
1.4 This international standard was developed in accor-
that are exposed along with the test object. In cases of limited
dance with internationally recognized principles on standard-
filmsizeorextendedobjectsize,theindicatorsmaybeexposed
ization established in the Decision on Principles for the
on another film immediately prior to or following exposure of
Development of International Standards, Guides and Recom-
the test object under exactly the same conditions (refer to
mendations issued by the World Trade Organization Technical
ProcessControlRadiographs,Section10).TheIQIvaluesmust
Barriers to Trade (TBT) Committee.
be determined from films with an optical density between 2.0
to 3.0. Two types of IQIs are used.
2. Referenced Documents
4.1.1 Beam Purity Indicator (BPI)—The BPI is a device
2.1 ASTM Standards:
usedforquantitativedeterminationofradiographicquality.Itis
E543 Specification forAgencies Performing Nondestructive
a polytetrafluoroethylene block containing two boron nitride
Testing
disks, two lead disks, and two cadmium or gadolinium wires.
E748 Guide for Thermal Neutron Radiography of Materials
Akey feature of the BPI is the ability to make a visual analysis
E803 TestMethodforDeterminingthe L/D RatioofNeutron
of its image for subjective information, such as image unsharp-
ness and film and processing quality. Densitometric measure-
ments of the image of the device permit quantitative determi-
This test method is under the jurisdiction of ASTM Committee E07 on
nation of the effective value for the thermal neutron content,
Nondestructive Testing and is the direct responsibility of Subcommittee E07.05 on
gamma content, pair production content, and scattered neutron
Radiology (Neutron) Method.
Current edition approved May 1, 2019. Published September 2019. Originally
content. The BPI shall be constructed in accordance with
approved in 1975. Last previous edition approved in 2014 as E545 – 14. DOI:
Practice E2003. Optionally, any BPI fabricated prior to publi-
10.1520/E0545-19.
cation of Practice E2003 which conforms toTest Method E545
The numerical values obtained in the calculations described herein may vary
- 81 through 91 may be used.
between different film processing systems, film types, and within one processing
system if processing variables change.
4.1.2 Sensitivity Indicator (SI)—The SI device is used for
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
qualitative determination of the sensitivity of detail visible on
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
a neutron radiograph.The SI is a step-wedge device containing
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. gaps and holes of known dimensions. Visual inspection of the
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E545−19
image of this device provides subjective information regarding 7.3 Each radiograph shall include a beam purity indicator
total radiographic sensitivity with respect to the step-block and a sensitivity indicator or a Process Control Radiograph
material. The SI shall be constructed in accordance with shall be used (refer to Section10 for details on Process Control
Practice E2023. Optionally, any SI fabricated prior to publica- Radiographs).
tion of Practice E2023 which conforms to Test Method
7.4 The indicators shall be located no less than 25 mm from
E545-81 through 91 may be used.
any edge of the exposed area of the film when feasible.
4.2 Neutron radiography practices are discussed in Guide
7.5 Theindicatorsshallbelocatedsuchthattheimageofthe
E748.
indicators on the film do not overlap the image of the object.
7.6 The SI should be oriented parallel to and as close as
5. Significance and Use
possible to the film.
5.1 The BPI is designed to yield quantitative information
7.7 The SI should be oriented such that its thickest step is
concerning neutron beam and image system parameters that
not adjacent to the BPI or the objects being radiographed.
contribute to film exposure and thereby affect overall image
7.8 The BPI surface must be parallel against the film
quality. In addition, the BPI can be used to verify the
cassette face during exposure or density readings will be
day-to-day consistency of the neutron radiographic quality.
invalid.
Gadolinium conversion screens and single-emulsion silver-
halide films, exposed together in the neutron imaging beam,
7.9 The cadmium or gadolinium wires in the BPI shall be
were used in the development and testing of the BPI. Use of
orientedsuchthattheirlongitudinalaxisisperpendiculartothe
alternative detection systems may produce densitometric read-
nearest film edge.
ings that are not valid for the equations used in Section 9.
7.10 Measure the film densities using a diffuse transmission
5.2 The only truly valid sensitivity indicator is a reference densitometer.Thedensitometershallbecalibratedaccordingto
standard part. A reference standard part is a material or Practice E1079.
component that is the same as the object being neutron
7.11 For the purpose of determining image quality, the
radiographed except with a known standard discontinuity,
background optical density shall be between 2.0 and 3.0
inclusion, omission, or flaw. The sensitivity indicators were
measured at the hole in the center of the BPI.
designed to substitute for the reference standard and provide
7.12 Determine the thermal neutron content (NC), scattered
qualitative information on hole and gap sensitivity.
neutron content (S), gamma content (γ), and pair production
5.3 The number of areas or objects to be radiographed and
content (P) by densitometric analysis of the BPI image. Make
the film acceptance standard used should be specified in the
a determination of the constituents of film exposure by
contract, purchase order, specification, or drawings.
measuring the densities in the BPI image as shown in Table 1.
6. Basis of Application
6.1 Qualification of Nondestructive Agencies—If specified
in the contractual agreement, NDT agencies shall be qualified
and evaluated in accordance with Specification E543. The
applicable revision of Specification E543 shall be specified in
the contractual agreement.
6.2 Procedures and Techniques—The procedures and tech-
niques to be utilized shall be as described in this test method
unless otherwise specified. Specific techniques may be speci-
fied in contractual documents.
6.3 Extent of Examination—The extent of examination shall
be in accordance with Section 7 unless otherwise specified.
6.4 Reporting Criteria/Acceptance Criteria—Reporting cri-
teria for the examination results shall be in accordance with
Section 11 unless otherwise specified. Acceptance criteria (for
TABLE 1 Definitions of Density Variables
example, for reference radiographs) shall be specified in the
higher D Larger film density measured through the images of the boron nitride
B
contractual agreement.
disks.
lower D Smaller film density measured through the images of the boron nitride
B
disks.
7. Procedure
higher D Larger film density measured through the images of the lead disks.
L
lower D Smaller film density measured through the images of the lead disks.
L
7.1 The direction of the beam of radiation should be as
D Film density measured at the center of the hole in the BPI.
H
perpendicular as possible to the plane of the film.
D Film density measured through the image of the polytetrafluoroethylene.
T
∆D higher D - lower D
L L L
7.2 Use Conversion screens that respond to neutrons of
∆D higher D - lower D
B B B
t
...

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. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: E545 − 14 E545 − 19
Standard Test Method for
Determining Image Quality in Direct Thermal Neutron
Radiographic Examination
This standard is issued under the fixed designation E545; 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.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope*
1.1 This test method covers the use of an Image Quality Indicator (IQI) system to determine the relative quality of radiographic
images produced by direct, thermal neutron radiographic examination. The requirements expressed in this test method are not
intended to control the quality level of materials and components.
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this 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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.3 The values stated in SI units are regarded to be standard.
1.4 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
E543 Specification for Agencies Performing Nondestructive Testing
E748 Guide for Thermal Neutron Radiography of Materials
E803 Test Method for Determining the L/D Ratio of Neutron Radiography Beams
E1079 Practice for Calibration of Transmission Densitometers
E1316 Terminology for Nondestructive Examinations
E2003 Practice for Fabrication of the Neutron Radiographic Beam Purity Indicators
E2023 Practice for Fabrication of Neutron Radiographic Sensitivity Indicators
3. Terminology
3.1 Definitions—For definitions of terms used in this test method, see Terminology E1316, Section H.
4. Summary of Test Method
4.1 The judgment of the quality of a neutron radiograph is based upon the evaluation of images obtained from indicators that
are exposed along with the test object. In cases of limited film size or extended object size, the indicators may be exposed on
another film immediately prior to or following exposure of the test object under exactly the same conditions (refer to Process
Control Radiographs, Section 10). The IQI values must be determined from films with an optical density between 2.0 to 3.0. Two
types of IQIs are used.
This test method is under the jurisdiction of ASTM Committee E07 on Nondestructive Testing and is the direct responsibility of Subcommittee E07.05 on Radiology
(Neutron) Method.
Current edition approved June 1, 2014May 1, 2019. Published June 2014September 2019. Originally approved in 1975. Last previous edition approved in 20102014 as
E545 - 05E545 – 14.(2010). DOI: 10.1520/E0545-14.10.1520/E0545-19.
The numerical values obtained in the calculations described herein may vary between different film processing systems, film types, and within one processing system
if processing variables changes.change.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E545 − 19
4.1.1 Beam Purity Indicator (BPI)—The BPI is a device used for quantitative determination of radiographic quality. It is a
polytetrafluoroethylene block containing two boron nitride disks, two lead disks, and two cadmium or gadolinium wires. A key
feature of the BPI is the ability to make a visual analysis of its image for subjective information, such as image unsharpness and
film and processing quality. Densitometric measurements of the image of the device permit quantitative determination of the
effective value for the thermal neutron content, gamma content, pair production content, and scattered neutron content. The BPI
shall be constructed in accordance with Practice E2003. Optionally, any BPI fabricated prior to publication of Practice E2003
which conforms to Test Method E545 - 81 through 91 may be used.
4.1.2 Sensitivity Indicator (SI)—The SI is one of several devices device is used for qualitative determination of the sensitivity
of detail visible on a neutron radiograph. The SI is a step-wedge device containing gaps and holes of known dimensions. Visual
inspection of the image of this device provides subjective information regarding total radiographic sensitivity with respect to the
step-block material. The SI shall be constructed in accordance with Practice E2023. Optionally, any SI fabricated prior to
publication of Practice E2023 which conforms to Test Method E545-81 through 91 may be used.
4.2 Neutron radiography practices are discussed in PracticesGuide E748.
5. Significance and Use
5.1 The BPI is designed to yield quantitative information concerning neutron beam and image system parameters that contribute
to film exposure and thereby affect overall image quality. In addition, the BPI can be used to verify the day-to-day consistency of
the neutron radiographic quality. Gadolinium conversion screens and single-emulsion silver-halide films, exposed together in the
neutron imaging beam, were used in the development and testing of the BPI. Use of alternative detection systems may produce
densitometric readings that are not valid for the equations used in Section 9.
5.2 The only truly valid sensitivity indicator is a reference standard part. A reference standard part is a material or component
that is the same as the object being neutron radiographed except with a known standard discontinuity, inclusion, omission, or flaw.
The sensitivity indicators were designed to substitute for the reference standard and provide qualitative information on hole and
gap sensitivity.
5.3 The number of areas or objects to be radiographed and the film acceptance standard used should be specified in the contract,
purchase order, specification, or drawings.
6. Basis of Application
6.1 Qualification of Nondestructive Agencies—If specified in the contractual agreement, NDT agencies shall be qualified and
evaluated in accordance with PracticeSpecification E543. The applicable revision of PracticeSpecification E543 shall be specified
in the contractual agreement.
6.2 Procedures and Techniques—The procedures and techniques to be utilized shall be as described in this test method unless
otherwise specified. Specific techniques may be specified in contractual documents.
6.3 Extent of Examination—The extent of examination shall be in accordance with Section 7 unless otherwise specified.
6.4 Reporting Criteria/Acceptance Criteria—Reporting criteria for the examination results shall be in accordance with Section
11 unless otherwise specified. Acceptance criteria (for example, for reference radiographs) shall be specified in the contractual
agreement.
7. Procedure
7.1 The direction of the beam of radiation should be as perpendicular as possible to the plane of the film.
7.2 Use Conversion screens that respond to neutrons of thermal energies, such as metallic gadolinium.
7.3 Each radiograph shall include a beam purity indicator and a sensitivity indicator or a Process Control Radiograph shall be
used (refer to Section 10 for details on Process Control Radiographs).
7.4 The indicators shall be located no less than 25 mm from any edge of the exposed area of the film when feasible.
7.5 Each radiograph shall include a beam purity indicator and a sensitivity indicator (refer to Section 10 for exceptions). The
indicators shall be located no less than 25 mm from any edge of the exposed area of the film when feasible. The indicators shall
be located such that the image of the indicators on the film do not overlap the image of the object.
7.6 The SI should be oriented parallel to and as close as possible to the film.
7.7 The SI should be oriented such that its thickest step is not adjacent to the BPI or the objects being radiographed.
7.8 The BPI surface must be parallel against the film cassette face during exposure or density readings will be invalid.
7.9 The cadmium or gadolinium wires in the BPI shall be oriented such that their longitudinal axis is perpendicular to the nearest
film edge.
7.10 Measure the film densities using a diffuse transmission densitometer. The densitometer shall be accurate calibrated
according to 60.02Practice E1079density units.
E545 − 19
7.11 For the purpose of determining image quality, the background optical density shall be between 2.0 and 3.0 measured at
the hole in the center of the BPI.
7.10 The only true measurement of the beam uniformity is with a radiograph made without objects. Background film optical
density in the range from 2.0 to 3.0 across the film should not vary more than 65 % from the numerical mean of five
measurements: one measurement at the center and one measurement approximately 25 to 30 mm toward the center from each
corner of the film. If the beam diameter is smaller than the film, the four outside measurements shall be taken 25 to 30 mm from
the edge of the beam located at 90° intervals.
7.11 Radiographs shall be free of any blemish that may interfere with subsequent examination of the image.
7.12 Determine the thermal neutron content (NC), scattered neutron content (S), gamma content (γ), and pair production content
(P) by densitometric analysis of the BPI image. Make a determination of the constituents of film exposure by measuring the
densities in the BPI image as shown in Table 1. Calculate the various exposure contributors by the equations given in Section 9.
7.13 Determine the sensitivity level by visually analyzing the image of the SI. Determine the values for G and H using Tables
2 and 3.
7.14 Determine the neutron radiographic category from Table 4.
7.15 Visually compare the images of the cadmium w
...