ISO/ASTM 51818:2009

Practice for dosimetry in an electron beam facility for radiation processing at energies between 80 and 300 keV

ISO 51818:20090 applies to dosimetric procedures to determine the performance of low-energy (300 keV or less) single-gap electron-beam radiation processing facilities. Other practices and procedures related to facility characterization, process qualification and routine processing are also discussed. The electron-energy range covered in ISO 51538:2009 is from 80 keV to 300 keV. Such electron beams can be generated by single-gap self-contained thermal filament or plasma-source accelerators.

Pratique de la dosimétrie dans une installation de traitement par irradiation utilisant un faisceau d'électrons d'énergies comprises entre 80 et 300 keV

General Information

• Status: Withdrawn
• Publication Date: 06-Jul-2009
• Withdrawal Date: 06-Jul-2009
• ICS: 17.240 - Radiation measurements
• Technical Committee: ISO/TC 85 - Nuclear energy, nuclear technologies, and radiological protection
• Drafting Committee: ISO/TC 85 - Nuclear energy, nuclear technologies, and radiological protection
• Current Stage: 9599 - Withdrawal of International Standard
• Completion Date: 15-May-2013

Relations

• Revised: ISO/ASTM 51818:2013 - Practice for dosimetry in an electron beam facility for radiation processing at energies between 80 and 300 keV
• Effective Date: 20-Oct-2012
• Revises: ISO/ASTM 51818:2002 - Practice for dosimetry in an electron-beam facility for radiation processing at energies between 80 keV and 300 keV
• Effective Date: 15-Apr-2008
• Consolidated By: ISO/TS 18234-9:2013 - Intelligent transport systems — Traffic and travel information via transport protocol experts group, generation 1 (TPEG1) binary data format — Part 9: Traffic event compact (TPEG1-TEC)
• Effective Date: 06-Jun-2022

Standards Content (Sample)

INTERNATIONAL ISO/ASTM
STANDARD 51818
Second edition
2009-06-15
Practice for dosimetry in an electron
beam facility for radiation processing at
energies between 80 and 300 keV
Pratique de la dosimétrie dans une installiation de traitement par
irradiation utilisant un faisceau d’électrons d’énergies comprises
entre 80 keV et 300 keV
Reference number
ISO/ASTM 51818:2009(E)
© ISO/ASTM International 2009

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ISO/ASTM 51818:2009(E)
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ISO/ASTM FDIS 51818:2009(E)
Contents Page
1 Scope . 1
2 Referenced documents . 1
3 Terminology . 1
4 Significance and use . 4
5 Dosimetry systems . 4
6 Calibration of the dosimetry system . 4
7 Installation and operational qualification . 5
8 Performance qualification . 5
9 Throughput calculations . 5
10 Measurement uncertainty . 6
11 Certification . 6
12 Keywords . 7
Annexes . 7
Bibliography . 11
Figure 1 Depth dose curves calculated from Monte Carlo Code (ITS) for acceleration voltages
ranging 100 to 300 keV in 25 keV increments. The curves show only depth-dose in a unit density
substrate passing under the beam path (13-µm titanium window, 20-mm air gap). . 2
Figure A1.1 Depth dose curve 300 kV (2.5 cm air gap, 13 µm Titanium foil window). Depth value
intervals are based on depth measurements from the back surface of the dosimeter. . 8
Figure A1.2 Electron beam width dose uniformity . 10
Table 1 Measured dose at surface, K f, dose from calculated K , and derived values of f at
A i A i
specific acceleration voltages (13-µm Titanium window, 20-mm air gap, 30-cm wide processor
-1
running at 25 cm sec with a beam current of 10 mA) . 3
Table A1.1 Example of depth-dose distribution at 300 kV (air gap 2.5 cm, 13 µm Titanium foil
window) . 9
Table A2.1 Energy deposition per electron in FWT dosimeter calculated from Monte Carlo Code
-2
(MeV/g-cm ) (12 µm Titanium window, variable air gap) . 11
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ISO/ASTM 51818:2009(E)
Foreword
ISO(theInternationalOrganizationforStandardization)isaworldwidefederationofnationalstandardsbodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
Draft International Standards adopted by the technical committees are circulated to the member bodies for
voting. Publication as an International Standard requires approval by at least 75% of the member bodies
casting a vote.
ASTM International is one of the world’s largest voluntary standards development organizations with global
participation from affected stakeholders. ASTM technical committees follow rigorous due process balloting
procedures.
A project between ISO and ASTM International has been formed to develop and maintain a group of
ISO/ASTM radiation processing dosimetry standards. Under this project, ASTM Subcommittee E10.01,
Radiation Processing: Dosimetry and Applications, is responsible for the development and maintenance of
these dosimetry standards with unrestricted participation and input from appropriate ISO member bodies.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. Neither ISO nor ASTM International shall be held responsible for identifying any or all such patent
rights.
International Standard ISO/ASTM 51818 was developed by ASTM Committee E10, Nuclear Technology and
Applications, through Subcommittee E10.01, and by Technical Committee ISO/TC 85, Nuclear energy.
Thissecondeditioncancelsandreplacesthefirstedition(ISO/ASTM51818:2002),whichhasbeentechnically
revised.
iv © ISO/ASTM International 2009 – All rights reserved

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ISO/ASTM 51818:2009(E)
Standard Practice for
Dosimetry in an Electron Beam Facility for Radiation
1
Processing at Energies Between 80 and 300 keV
This standard is issued under the fixed designation ISO/ASTM 51818; the number immediately following the designation indicates the
year of original adoption or, in the case of revision, the year of last revision.
1. Scope 51607 Practice for Use of the Alanine-EPR Dosimetry
System
1.1 This practice covers dosimetric procedures to be fol-
51649 Practice for Dosimetry in an Electron Beam Facility
lowedtodeterminetheperformanceoflowenergy(300keVor
for Radiation Processing at Energies Betweeen 300 keV
less) single-gap electron beam radiation processing facilities.
and 25 MeV
Other practices and procedures related to facility characteriza-
51650 Practice for Use of a Cellulose Acetate Dosimetry
tion, process qualification, and routine processing are also
System
discussed.
51707 Guide for Estimating Uncertainties in Dosimetry for
1.2 The electron-energy range covered in this practice is
Radiation Processing
from80keVto300keV.Suchelectronbeamscanbegenerated
2.3 International Commission on Radiation Units and
by single-gap self-contained thermal filament or plasma source
3
Measurements (ICRU) Report:
accelerators.
ICRU Report 60 Fundamental Quantities and Units for
1.3 This standard does not purport to address all of the
Ionizing Radiation
safety concerns, if any, associated with its use. It is the
2.4 Monte Carlo Codes for CalculatingAbsorbed Dose and
responsibility of the user of this standard to establish appro-
4
Dose Distribution:
priate safety and health practices and determine the applica-
ZTRAN
bility of regulatory limitations prior to use.
PENELOPE
2. Referenced documents Integrated Tiger Series (ITS)
2
Monte Carlo Neutron Proton (MCNP)
2.1 ASTM Standards:
Electron Gamma Shower (EGS4)
E 170 Terminology Relating to Radiation Measurements
Energy Deposition in Multiple Layers (EDMULT)
and Dosimetry
E 2232 Guide for Selection and Use of Mathematical Meth-
3. Terminology
odsforCalculatingAbsorbedDoseinRadiationProcessing
3.1 Definitions:
Applications
3.1.1 absorbed dose (D)—quantity of ionizing radiation
E 2303 Guide for Absorbed-Dose Mapping in Radiation
energy imparted per unit mass of a specified material. The SI
Processing Facilities
2 unit of absorbed dose is the gray (Gy), where 1 gray is
2.2 ISO/ASTM Standards:
equivalent to the absorption of 1 joule per kilogram of the
51261 Guide for Selection and Calibration of Dosimetry
specified material (1 Gy = 1 J/kg). The mathematical relation-
Systems for Radiation Processing
– –
51275 Practice for Use of a Radiochromic Film Dosimetry ship is the quotient of d´ by dm, where d´ is the mean
System
incremental energy imparted by ionizing radiation to matter of
51400 Practice for Characterization and Performance of a incremental mass dm.
High-Dose Radiation Dosimetry Calibration Laboratory
d´¯
D 5 (1)
dm
3.1.1.1 Discussion—The discontinued unit for absorbed
1
This practice is under the jurisdiction of ASTM Committee E10 on Nuclear
dose is the rad (1 rad = 100 erg/g = 0.01 Gy).Absorbed dose is
Technology and Applications and is the direct responsibility of Subcommittee
sometimes referred to simply as dose.
E10.01 on Radiation Processing: Dosimetry andApplications, and is also under the
jurisdiction of ISO/TC 85/WG 3.
Current edition approved June 18, 2008. Published June 2009. Originally
´1 3
published asASTM E 1818–96. Last previousASTM edition E 1818–96 .ASTM Available from the International Commission on Radiation Units and Measure-
´1
E 1818–96 was adopted in 1998 with the intermediate designation ISO ments, 7910 Woodmont Ave., Suite 800, Bethesda, MD 20814, U.S.A.
4
15573:1998(E). The present International Standard ISO/ASTM 51818:2008(E) Available in the USA from the Radiation Safety Information Computational
replaces ISO 15573 and is a major revision of the last previous edition ISO/ASTM Center (RSICC), Oak Ridge National Laboratory (ORNL), P.O. Box 2008, Oak
51818:2002(E). Ridge, TN 37831, Tel: [phone], Fax: [phone], Web Address: www-
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or rsicc.ornl.gov. Available in Europe from CERN or web address www.cern.ch/
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM geant4, OECD Nuclear EnergyAgency, Le Seine Saint-Germain, 12 boulevard des
Standards volume information, refer to the standard’s Document Summary page on Iles, 92130 Issy-les-Moulineaux, France. Tel: [phone], Fax: +33 (0) 1
the AST M website. 4524 1110, Web address: www.nea.fr.
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ISO/ASTM 51818:2009(E)
3.1.2 average beam current—time-averaged electron beam beam width and beam length may be interchangeable. (5)
current delivered from the accelerator. Beam width may be quantified as the distance between two
3.1.3 beam length—dimension of the irradiation zone along points along the dose profile, which are at a defined fraction of
thedirectionofproductmovement,ataspecifieddistancefrom the maximum dose value in the profile. (6) Various techniques
the accelerator window. may be employed to produce an electron beam width adequate
3.1.3.1 Discussion—For graphic illustration, see ISO/ to cover the processing zone, for example, use of electromag-
ASTM Practice 51649. (1) This term usually applies to netic scanning of a pencil beam (in which case beam width is
electron irradiation. (2) Beam length is therefore perpendicular also referred to as scan width), defocusing elements, and
to beam width and to the electron beam axis. (3) In case of scattering foils.
product that is stationary during irradiation, beam length and 3.1.7 depth-dose distribution—variation of absorbed dose
beam width may be interchangeable. with depth from the incident surface of a material exposed to
3.1.4 beam power—product of the average electron beam a given radiation.
energy and the average beam current (unit kW). 3.1.7.1 Discussion—See Fig. 1 for calculated values for
3.1.5 beam uniformity—dose variation distributed across electron energies from 100 to 300 keV.
the beam width. 3.1.8 dose uniformity ratio—ratio of the maximum to the
3.1.6 beam width—dimension of the irradiation zone per- minimum absorbed dose within the process load. The concept
pendicular to the direction of product movement, at a specified is also referred to as the max/min dose ratio.
distance from the accelerator window. 3.1.9 dosimeter—device that, when irradiated, exhibits a
3.1.6.1 Discussion—For graphic illustration, see ISO/ quantifiable change that can be related to absorbed dose in a
ASTM Practice 51649. (1) This term usually applies to given material using appropriate measurement instruments and
electron irradiation. (2) Beam width is therefore perpendicular procedures.
to beam length and to the electron beam axis. (3) In case of a 3.1.10 dosimetry system—system used for determining ab-
low-energy, single-gap electron accelerator, beam width is sorbed dose, consisting of dosimeters, measurement instru-
equal to the active length of the cathode assembly in vacuum. ments and their associated reference standards, and procedures
(4) In the case of product that is stationary during irradiation, for the system’s use.
FIG. 1 Depth dose curves calculated from Monte Carlo Code (ITS) for acceleration voltages
ranging 100 to 300 keV in 25 keV increments. The curves show only depth-dose in a unit density substrate passing under the beam
path (13-µm titanium window, 20-mm air gap).
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ISO/ASTM 51818:2009(E)
3.1.11 electron beam energy—average kinetic energy of the 3.2.3 linear rate coeffıcient (K )—quantity relating the
L
accelerated electrons in the beam (units—eV (electron volts)). product length irradiated per unit time to beam current and
3.1.11.1 Discussion—Often, the numeric value of the accel- absorbed dose.
eration voltage in kV is used to characterize beam energy in 3.2.3.1 Discussion—Typically, this value is expressed in
keV. The maximum energy of the beam inside the accelerator kilogray meters per milliampere minute, or megarad feet per
is equal to the acceleration voltage but expressed in keV units. milliampere minute. Theoretical values can be calculated from
The beam energy at the product surface is less than the the surface area rate coefficients given in Table 1 for particular
maximum energy inside the accelerator due to losses in the beam widths. This quantity is sometimes called the linear
beam path, such as the window and the air gap. processing coefficient (see 9.3) In this standard the terms “rad”
3.1.12 practical electron range R —depth in homogeneous or“megarad(Mrad)”areincludedinadditiontotheSIunitsfor
p
materialtothepointwherethetangentatthesteepestpoint(the the convenience of some industry users.
inflection point) on the almost straight descending portion of 3.2.4 mass processing rate—mass throughput rate based on
the depth-dose distribution curve meets the extrapolated X-ray the output power (expressed in watts) of the electron beam, the
background. mass of the irradiated material and the dose.
3.1.12.1 Discussion—For graphic illustration, see ISO/ 3.2.4.1 Discussion—Typically this value is expressed in
ASTM Practice 51649. kilogray kilograms per kilowatt hour or megarad pounds per
3.1.13 process load—volume of material with a specified kilowatt hour. In this standard the terms “rad” or “megarad
product loading configuration irradiated as a single entity. (Mrad)” are included in addition to the SI units for the
3.1.14 production run (for continuous-flow and shuffle- convenience of some industry users.
dwell irradiation)—series of process loads consisting of ma- 3.2.5 product plane—planecorrespondingtothetopsurface
terials or products having similar radiation-absorption charac- of the product being irradiated.
teristics, that are irradiated sequentially to a specified range of 3.2.6 single-gap accelerator—electron beam source con-
absorbed dose. sisting of a vacuum chamber and a high voltage power supply
3.1.15 self-shielded accelerator—electron beam source that that can accelerate a dispersed beam of electrons from a high
is integrally designed with radiation shielding, product trans- voltage potential to ground potential in one stage.
port system, and irradiation chamber. 3.2.7 surface area rate coeffıcient (K )—quantity relating
A
3.1.16 traceability—propertyoftheresultofameasurement the product area irradiated per unit time to beam current and
or the value of a standard whereby it can be related to stated absorbed dose.
references, usually national or international standards, through 3.2.7.1 Discussion—Typically this value is expressed in
an unbroken chain of comparisons all having stated uncertain- kilogray square meter per milliampere minute, or megarad
ties. squarefootpermilliampereminute.Examplevaluesareshown
3.1.17 uncertainty—parameter associated with the result of in Table 1. This quantity is sometimes called the area process-
a measurement that characterizes the dispersion of the values ing coefficient. In this standard the terms “rad” or “megarad
that could reasonably be attributed to the measurand or derived (Mrad)” are included in addition to the SI units for the
quantity (see ISO/ASTM Guide 51707). convenience of some industry users.
3.2 Definitions of Terms Specific to This Standard: 3.3 Definitions of other terms used in this standard that
3.2.1 air gap—distance between the product plane and the pertain to radiation measurement and dosimetry may be found
electron beam window. in Terminology E 170. Definitions in Terminology E 170 are
3.2.2 electron processor—electron beam accelerator and compatible with ICRU Report 60; that document, therefore,
associated equipment. may be used as an alternative reference.
TABLE 1 Measured dose at surface, K f, dose from calculated K , and derived values of f at specific acceleration voltages
A i A i
-1
(13-µm Titanium window, 20-mm air gap, 30-cm wide processor running at 25 cm sec with a beam current of 10 mA)
Electron Beam kGy Monte Carlo Beam Current
2
Dosimetry Mrad Foot /Milliampere
2
Acceleration Meter /Milliampere TIGER Result Utilization
A
kGy (Mrad) minute (K · f)
A A i B
Voltage second (K · f) kGy (Mrad) Efficiency (f)
A i i
100 kV 9.37 (0.937) 0.0722 4.69 13.6 (1.36) 0.69
125 kV 34.3 (3.43) 0.265 17.2 51.4 (5.14) 0.67
150 kV 46.2 (4.62) 0.355 23.1 66.8 (6.68) 0.69
175 kV 49.5 (4.95) 0.382 24.8 69.5 (6.95) 0.71
200 kV 47.3 (4.73) 0.365 23.7 66.1 (6.61) 0.72
225 kV 45.1 (4.51) 0.348 22.6 61.7 (6.17) 0.73
250 kV 41.2 (4.12) 0.317 20.6 55.8 (5.58) 0.74
275 kV 39.6 (3.96) 0.305 19.8 50.7 (5.07) 0.78
300 kV 35.8 (3.58) 0.275 17.9 46.7 (4.67) 0.77
A
Calculations based on dosimetry (8). The beam current utilization efficiency factor (f) is an integral part of the calculation.
i
B
The 1-D Monte Carlo TIGER calculation does not include the beam current utilization efficiency factor (f). When the calculation is compared with dosimetry, the beam
i
current utilization efficiency factor (f) is thus derived for each voltage. (See Note 7 in 9.2 for discussion.)
i
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ISO/ASTM 51818:2009(E)
4. Significance and use standard dosimeters, along with their useful dose ranges, are
given in ISO/ASTM Guide 51261.
4.1 A variety of irradiation or treatment processes use low
5.1.1.3 Transfer-Standard Dosimeters—Transfer-standard
energy electron processors to modify product characteristics.
dosimeters are specially selected dosimeters used for transfer-
Dosimetry requirements, the number and frequency of mea-
ring absorbed-dose information from an accredited or national
surements, and record keeping requirements will vary depend-
standards laboratory to an irradiation facility in order to
ing on the type and end use of the products being processed.
establish traceability for that facility. These dosimeters should
Dosimetry measurements are often used in conjunction with
be carefully used under conditions that are specified by the
physical, chemical, or biological testing of the product, to help
issuing laboratory. Transfer-standard dosimeters may be se-
verify specific treatment parameters.
lected from either reference-standard dosimeters or routine
NOTE 1—In many cases reference data may be developed, comparing
dosimeters taking into consideration the criteria listed in
dosimetry results with other quantitative product testing; for example, gel
ISO/ASTM Guide 51261.
fraction, melt flow, modulus, molecular weight distribution, or cure
5.1.1.4 Routine Dosimeters—Routine dosimeters may be
analysis tests can be used to estimate radiation dose in specific relevant
used for radiation process quality control, dose monitoring and
materials.
dose mapping. Proper dosimetric techniques, including cali-
4.2 Radiation processing specifications usually include a
bration, shall be employed to ensure that measurements are
minimum or maximum absorbed dose limit, or both. For a
reliable and accurate. Examples of routine dosimeters, along
given application these limits may be set by government
with their useful dose ranges, are given in ISO/ASTM Guide
regulation or by limits inherent to the product itself.
51261.
4.3 Critical process parameters must be controlled to obtain
5.2 The documents listed in Section 2 provide detailed
reproducible dose distribution in processed materials. The
information on the selection and use of appropriate dosimetry
electron beam energy (in eV or keV), beam current (in mA),
systems for electron beam irradiation. Due to the limited depth
spatial distribution of the beam, and exposure time or process
of penetration of low energy electron beams and the narrow air
line speed all affect absorbed dose.
gaps that are inherent in self-shielded equipment, thin film
dosimeters are usually preferred over thicker systems (see Refs
NOTE 2—In some liquid-to-solid polymerization applications (often
5
1-6, ISO/ASTM Practices 51275, 51607 and 51650, and
referred to as radiation curing), the residual oxygen level during irradia-
ISO/ASTM Guide 51261).
tion must be controlled to achieve consistent results. A high level of
residual oxygen can affect product performance in these curing applica-
NOTE 3—Dosimetry systems are available that provide the option of
tions, but does not affect the absorbed dose. However, oxygen effects on
usingeitherasinglepointmeasurementdosimetermethodoracontinuous
the response function of the dosimeter used in the measurement of dose
scan area readout technique for use with film strips or segments of film.
should be taken into account.
6. Calibration of the dosimetry system
4.4 Before any radiation process system can be utilized, it
must be validated to determine its effectiveness. This involves 6.1 A dosimetry system shall be calibrated prior to use and
at intervals thereafter in accordance with the user’s docu-
testing of the process equipment, calibrating the measuring
instruments, and demonstrating the ability to deliver the mented procedure that specifies details of the calibration
process and quality assurance requirements. Calibration meth-
desired dose within the desired dose range in a reliable and
reproducible manner. ods are given in ISO/ASTM Guide 51261.
6.2 Calibration Irradiation—Irradiation is a critical compo-
nent of the calibration of the dosimetry system. Acceptable
5. Dosimetry systems
ways of performing the calibration irradiation depend on
5.1 Description of Dosimeter Classes:
whether the dosimeter is used as a reference-standard, transfer-
5.1.1 Dosimeters may be divided into four basic classes
standard or routine dosimeter.
according to their relative quality and areas of application:
6.2.1 Reference- or Transfer-Standard Dosimeters—
primary-standard, reference-standard, transfer-standard, and
Calibration irradiations shall be performed at a national or
routine dosimeters. ISO/ASTM Guide 51261 provides infor-
accredited laboratory using criteria specified in ISO/ASTM
mation about the selection of dosimetry systems for different
Practice 51400.
applications. All classes of dosimeters, except the primary
6.2.2 Routine Dosimeters—The calibration irradiation may
standards, require calibration before their use.
be performed by irradiating the dosimeters at (a) a national or
5.1.1.1 Primary-Standard Dosimeters—Primary-standard
accredited laboratory using criteria specified in ISO/ASTM
dosimeters are established and maintained by national stan-
Practice 51400, (b) an in-house calibration facility that pro-
dards laboratories for calibration of radiation environments
vides an absorbed dose (or an absorbed-dose rate) having
(fields) and other classes of dosimeters. The two most com-
measurement traceability to nationally or internationally rec-
monly used primary-standard dosimeters are ionization cham-
ognized standards, or (c) a production irradiator under actual
bers and calorimeters.
production irradiation conditions, together with reference- or
5.1.1.2 Reference-Standard Dosimeters—Reference-
standard dosimeters are used to calibrate radiation environ-
5
ments and routine dosimeters. Reference-standard dosimeters
The boldface numbers in parentheses refer to the bibliography at the end of this
mayalsobeusedasroutinedosimeters.Examplesofreference- standard.
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ISO/ASTM 51818:2009(E)
transfer-standard dosimeters that have measurement traceabil- 7.2.1 Surface Area Rate Coeffıcient Measurements—Use a
ity to nationally or internationally recognized standards. In minimum of five measurements over the voltage range of
caseofoption (a)or (b),theresultingcalibrationcurveshallbe interest with at least five dosimeters or dose measurements
verified for the actual conditions of use (see ISO/ASTM Guide equally spaced across the width of the beam at the product
51261). plane at a nominal dose level. The surface area rate measure-
ment should be repeated at a typical operating voltage level at
NOTE 4—While 6.2.2 is valid for most dosimeter calibrations, it must
several different beam current levels to establish and test the
be recognized that the irradiation of many dosimeters with low energy
linearity between beam current and surface dose (see Annex
electrons (less than 300 keV) will lead to dose gradients through the
A1).
thickness of the dosimeter.When the dosimeter is measured, this will lead
to an apparent dose that is related to the dose distribution. For a given set
7.2.2 Beam Uniformity Measurements—Use a minimum of
ofirradiationconditions,theapparentdosewilldependonthethicknessof
one dosimeter or dose measurement per 2.5 cm over full beam
the dosimeter, ie., different thickness dosimeters will measure different
width (see Annex A1).
apparent doses (7). One solution to overcome this problem might be to
7.2.3 Depth-dose Measurements—Depth-dose measure-
suggest that all dose measurements are specified as dose to water in the
first micrometer of the absorbing material. This is given the symbol D
ments shall be made to cover the voltage range of interest. A
µ
and is independent of dosimeter thickness.
minimum of three measurements shall be made at each voltage
The relationship between D and the apparent dose strongly depends on
µ selected for testing.Apractical method to accomplish this is to
dosimeter response function, dosimeter thickness, dose, radiation energy,
measure depth-dose with a stack of dosimeters, at the product
acceleratorwindowmaterialandthickness,distancewindowtodosimeter,
surface (see Annex A1).
and temperature of air between window and dosimeter. The relationship
must be calculated for each set of irradiation conditions. The relationship
8. Performance qualification
must be applied for calibrations that are carried out by comparison
between two different dosimeter systems (ISO/ASTM Guide 51261).
8.1 Initial proces
...