ISO/ASTM 51650:2002

Practice for use of a cellulose triacetate dosimetry system

ISO 51650 covers the preparation, handling, testing and procedures for the use of cellulose acetate dosimetry systems, and the spectrometric, densitometric or photometric read-out equipment for measuring absorbed doses in materials irradiated by photons and electrons in terms of absorbed dose in water. Cellulose acetate dosimeter refers to untinted and tinted cellulose triacetate (CTA) or cellulose diacetate (CDA) film dosimeter. This practice applies to cellulose acetate film dosimeters that can be used within part or all of the specified ranges as follows: the absorbed dose range for untinted CTA is 5 times 103 Gy to 3 times 10 5 Gy for photons and electrons; the absorbed dose range for tinted CDA is 1 times 104 Gy to 1 times 10 6 Gy for photons and electrons; the absorbed dose rate for both CTAand CDA is from 0,03 to 4 times 1010 Gy s -1; the radiation energy range for photons is from 0,1 MeV to 50 MeV; the radiation energy range for electrons is from 0,2 MeV to 50 MeV; the irradiation temperature range is from - 10 °C to 70 °C.

Pratique de l'utilisation d'un système dosimétrique au triacétate de cellulose

General Information

• Status: Withdrawn
• Publication Date: 17-Apr-2002
• Withdrawal Date: 17-Apr-2002
• 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: 22-Jul-2005

Relations

• Revised: ISO/ASTM 51650:2005 - Practice for use of a cellulose triacetate dosimetry system
• Effective Date: 15-Apr-2008
• Revises: ISO 15570:1998 - Practice for use of cellulose acetate dosimetry system
• Effective Date: 15-Apr-2008

Standards Content (Sample)

INTERNATIONAL ISO/ASTM
STANDARD 51650
First edition
2002-03-15
Practice for use of cellulose acetate
dosimetry systems
Pratique de l’utilisation des systèmes dosimétriques à l’acétate
de cellulose
Reference number
ISO/ASTM 51650:2002(E)
© ISO/ASTM International 2002

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ISO/ASTM 51650:2002(E)
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ii © ISO/ASTM International 2002 – All rights reserved

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ISO/ASTM 51650:2002(E)
Contents Page
1 Scope . 1
2 Referenced documents . 1
3 Terminology . 2
4 Significance and use . 3
5 Apparatus . 3
6 Preparation of dosimeters . 3
7 Calibration of the dosimetry system . 4
8 Calibration of cellulose acetate dosimeter . 4
9 Condition for practical use . 6
10 Report . 6
11 Measurement uncertainty . 7
12 Keywords . 7
Annex . 7
Bibliography . 8
Figure 1 Absorption spectra before and after irradiation of untinted cellulose triacetate (CTA) film
with a 2 MeV electron beam . 3
Figure 2 The relation between the increment of absorbance/nominal thickness and dose in
untinted CTA . 4
Figure 3 Absorption spectra before and after irradiation to high doses . 4
Figure 4 Increase in the reciprocal of absorbance as a function of absorbed dose . 5
Table A1.1 Basic properties of available dosimeters . 7
Table A1.2 An example of single purpose absorbance measuring devices for cellulose acetate
dosimeters . 7
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ISO/ASTM 51650:2002(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(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 pilot project between ISO and ASTM International has been formed to develop and maintain a group of
ISO/ASTM radiation processing dosimetry standards. Under this pilot project, ASTM Subcommittee E10.01,
Dosimetry for Radiation Processing, 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 International Standard 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 51650 was developed by ASTM Committee E10, Nuclear Technology and
Applications, through Subcommittee E10.01, and by Technical Committee ISO/TC 85, Nuclear Energy.
Annex A1 of this International Standard is for information only.
iv © ISO/ASTM International 2002 – All rights reserved

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ISO/ASTM 51650:2002(E)
Standard Practice for
1
Use of Cellulose Acetate Dosimetry Systems
This standard is issued under the fixed designation ISO/ASTM 51650; 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 E 170 Terminology Relating to Radiation Measurements
3
and Dosimetry
1.1 This practice covers the preparation, handling, testing
E 275 Practice for Describing and Measuring Performance
and procedures for the use of cellulose acetate dosimetry
of Ultraviolet, Visible, and Near Infrared Spectrophotom-
systems, and the spectrometric, densitometric, or photometric
4
eters
readout equipment for measuring absorbed dose in materials
E 666 Practice for Calculating Absorbed Dose from Gamma
irradiated by photons and electrons in terms of absorbed dose
3
or X Radiation
in water.
E 925 Practice for the Periodic Calibration of Narrow Band-
NOTE 1—Cellulose acetate dosimeter refers to untinted and tinted 4
Pass Spectrophotometers
cellulose triacetate (CTA) or cellulose diacetate (CDA) film dosimeter.
E 958 Practice for Measuring Practical Spectral Bandwidth
4
1.2 This practice applies to cellulose acetate film dosimeters
of Ultraviolet-Visible Spectrophotometers
that can be used within part or all of the specified ranges as
E 1026 Practice for Using the Fricke Reference Standard
3
follows:
Dosimetry System
3
1.2.1 The absorbed dose range for untinted CTA is 5 3 10
2.2 ISO/ASTM Standards:
5
to 3 3 10 Gy for photons and electrons,
51205 Practice for Use of a Ceric-Cerous Sulfate Dosimetry
4
3
1.2.2 The absorbed dose range for tinted CDA is 1 3 10 to
System
6
1 3 10 Gy for photons and electrons,
51261 Guide for Selection and Calibration of Dosimetry
3
1.2.3 The absorbed dose rate for both CTA and CDA is from
Systems for Radiation Processing
10
0.03 to 4 3 10 Gy/s,
51275 Practice for Use of a Radiochromic Film Dosimetry
3
1.2.4 The radiation energy range for photons is from 0.1 to
System
50 MeV, and
51276 Practice for Use of a Polymethylmethacrylate Do-
3
1.2.5 The radiation energy range for electrons is from 0.2 to
simetry System
50 MeV.
51310 Practice for Use of a Radiochromic Optical
3
Waveguide Dosimetry System
NOTE 2—In cases where low-energy electrons and charged particles
51400 Practice for Characterization and Performance of a
cannot completely penetrate the thickness of standard CTA and DCA
2
High-Dose Gamma Radiation Dosimetry Calibration
films, thin films may be used (1,2).
3
Laboratory
1.2.6 The irradiation temperature range is from − 10 to
3
51401 Practice for Use of a Dichromate Dosimetry System
70°C.
51538 Practice for Use of the Ethanol-Chlorobenzene Do-
1.3 This standard does not purport to address all of the
3
simetry System
safety concerns, if any, associated with its use. It is the
51540 Practice for Use of a Radiochromic Liquid Dosim-
responsibility of the user of this standard to establish appro-
3
etry System
priate safety and health practices and determine the applica-
51607 Practice for Use of the Alanine-EPR Dosimetry
bility of regulatory limitations prior to use.
3
System
2. Referenced Documents 51608 Practice for Dosimetry in an X-Ray (Bremsstrahl-
3
ung) Irradiation Facility for Radiation Processing
2.1 ASTM Standards:
51631 Practice for Use of Calorimetric Dosimetry Systems
for Electron Beam Dose Measurements and Dosimeter
3
Calibrations
1
This practice is under the jurisdiction of ASTM Committee E10 on Nuclear 51649 Practice for Dosimetry in an Electron Beam Facility
Technology and Applications and is the direct responsibility of Subcommittee
for Radiation Processing at Energies between 300 keV and
E10.01 on Dosimetry for Radiation Processing, and is also under the jurisdiction of
3
25 MeV
ISO/TC 85/WG 3.
51707 Guide for Estimating Uncertainties in Dosimetry for
Current edition approved Jan. 22, 2002. Published March 15, 2002. Originally
e1 3
published as ASTM E 1650–94. Last previous ASTM edition E 1650–97 . ASTM
Radiation Processing
E 1650–94 was adopted by ISO in 1998 with the intermediate designation ISO
51818 Practice for Dosimetry in an Electron Beam Facility
15570:1998(E). The present International Standard ISO/ASTM 51650:2002 (E) is a
revision of ISO 15570.
2
The boldface numbers in parentheses refer to the bibliography at the end of this
practice.
3
Annual Book of ASTM Standards, Vol 12.02.
4
Annual Book of ASTM Standards, Vol 03.06.
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ISO/ASTM 51650:2002(E)
21
for Radiation Processing at Energies Between 80 and 300
SI unit:Gy·s (4)
3
keV
3.3.1 Discussion—The absorbed-dose rate is often specified
2.3 International Commission on Radiation Units and
˙
in terms of the average value of D over long-time interval, for
5
Measurements (ICRU) Reports:
−1 −1
example, in units of Gy · min or Gy · h .
ICRU Report 14 Radiation Dosimetry: X-Rays and Gamma
3.4 analysis wavelength—wavelength used in a spectropho-
Rays with Maximum Photon Energies Between 0.6 and 50
tometric instrument for the measurement of optical absorbance
MeV
or reflectance.
ICRU Report 17 Radiation Dosimetry: X-Rays and Gamma
3.5 calibration curve—graphical representation of the do-
Rays at Potentials of 5 to 150 kV
simetry system’s response function.
ICRU Report 34 The Dosimetry of Pulsed Radiation
3.6 cellulose acetate dosimeter—untinted and tinted cellu-
ICRU Report 35 Radiation Dosimetry: Electron Beams
lose triacetate (CTA) or cellulose diacetate (CDA) film dosim-
with Energies Between 1 and 50 MeV
eter that undergoes change in optical absorbance or optical
ICRU Report 37 Stopping Powers for Electrons and
density under ionizing radiation.
Positrons
3.6.1 Discussion—This change in absorbance or optical
ICRU Report 44 Tissue Substitutes in Radiation Dosimetry
density is related to radiation chemical change in cellulose
and Measurement
acetate, plasticizer and tinted dyes, and can be related to
ICRU Report 60 Radiation Quantities and Units
absorbed dose in water.
3.7 charged particle equilibrium—a condition that exists in
3. Terminology
a material under irradiation if the kinetic energies, number, and
3.1 absorbed dose,(D)—quantity of ionizing radiation en-
direction of charged particles induced by the radiation are
ergy imparted per unit mass of a specified material. The SI unit
uniform throughout the measurement volume of interest. Thus,
of absorbed dose is the gray (Gy), where 1 gray is equivalent
the sum of the kinetic energies of the charged particles entering
to the absorption of 1 joule per kilogram of the specified
the volume equals the sum of the kinetic energies of the
material (Gy = 1 J/kg). The mathematical relationship is the
charged particles leaving the volume.
quotient of de¯by dm, where de¯ is the mean incremental energy
3.7.1 Discussion—Electron equilibrium is often referred to
imparted by ionizing radiation to matter of incremental mass
as charged-particle equilibrium.
dm (see ICRU 60).
3.8 dosimeter batch—quantities of dosimeters made from a
D 5 de¯/dm (1)
specific mass of material with uniform composition, fabricated
3.1.1 Discussion—The discontinued unit for absorbed dose
in a single production run under controlled, consistent condi-
is the rad (rad = 100 erg/g = 0.01 Gy). Absorbed dose is
tions and having a unique identification code.
sometimes referred to simply as dose.
3.9 dosimetry system—a system used for determining ab-
For a photon source under conditions of charged particle
sorbed dose, consisting of dosimeters, measurement instru-
equilibrium (see definition), the absorbed dose, D, may be
ments and their associated reference standards, and procedures
expressed as:
for the system’s use.
D5F @E ~μ /r!# (2) 3.10 electron equilibrium—charged-particle equilibrium for
en
secondary electrons.
where:
3.11 measurement quality assurance plan—a documented
F = particle fluence (see definition),
program for the measurement process that assures on a
E = energy of the ionizing radiation, and
continuing basis that the overall uncertainty meets the require-
μ /r = mass energy absorption coefficient (see defini-
en
ments of the specific application. This plan requires traceability
tion).
to, and consistency with, nationally or internationally recog-
If bremsstrahlung production within the specified material is
nized standards.
negligible, the mass energy absorption coefficient (μ /r)is
en
3.12 measurement traceability—the ability to demonstrate
equal to the mass energy transfer coefficient (μ /r), and
tr
by means of an unbroken chain of comparisons that a mea-
absorbed dose is equal to air kerma.
surement is in agreement within acceptable limits of uncer-
3.2 absorbed-dose mapping—measurement of absorbed-
tainty with comparable nationally or internationally recognized
dose within a process load using dosimeters placed at specified
standards.
locations to produce a one-, two- or three-dimensional distri-
3.13 net absorbance (DA)—change in measured optical
bution of absorbed dose, thus rendering a map of absorbed
absorbance at a selected wavelength determined as the absolute
dose values.
difference between the pre-irradiation absorbance, A , and the
˙ 0
3.3 absorbed-dose rate (D)—the absorbed dose in a mate-
post-irradiation absorbance, A as follows:
rial per incremental time interval, ie. the quotient of dD by dt.
DA 5 |A 2 A | (5)
0
˙
D 5 dD/dt (3)
3.14 net optical density, DOD—another expression for “net
absorbance.”
5
3.14.1 Discussion—This expression is more commonly
Available from the International Commission on Radiation Units and Measure-
ments, 7910 Woodmont Ave., Suite 800, Bethesda, MD 20814, USA. used for film and plastic dosimeters than for liquid dosimeters.
© ISO/ASTM International 2002 – All rights reserved
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ISO/ASTM 51650:2002(E)
3.15 specific net absorbance (Dk)—net absorbance, D A,at 5.1.2 UV/visible spectrophotometer or an equivalent instru-
a selected wavelength divided by the optical pathlength, d, ment having documentation covering: (1) the analytical wave-
through the dosimeter as follows: length at which absorbance or optical density is measured (see
8.2); (2) the accuracy of wavelength selection, absorbance or
Dk5DA/d (6)
optical density reading (see Figs. 1-4 for suitable wavelength—
3.16 stock—part of a dosimeter batch, held by the user.
for example, 280 nm for untinted CTA and 390 nm for dyed
3.17 traceabilty—see measurement traceability.
CDA); and (3) the spectral wavelength range (in the case of
3.18 Other appropriate terms may be found in Terminology
absorption spectral readout as discussed in Ref 16). In addition,
E 170.
stray light rejection is needed. The spectrophotometer or the
equivalent instrument should also be able to read the absor-
4. Significance and Use
bance up to a value of 2.0 at a suitable wavelength with an
4.1 The cellulose acetate (CTA and CDA) dosimetry sys-
uncertainty of no more than 61%.
tems provide a means of measuring absorbed dose in materials
5.1.3 A film holder for spectrophotometer, or equivalent
(3-17). Under the influence of radiation, chemical reactions
device, should keep the film perpendicular to the analytical
take place in the cellulose acetate, plasticizer or dyes in the
beam, or a built-in automatic film feeder at a speed of the order
matrix, changing the optical absorption properties (absorption
of 0.1 to 1 cm/s with the same specifications of the film holder
wavelength (band) and density) (18). Absorbance or optical
used for automatic one-dimensional dose profile measurement.
density values are measured at the selected wavelength using a
5.1.4 The thickness gage shall be calibrated and traceable to
spectrophotometer, densitometer, or photometer.
nationally or internationally recognized standards within a
4.2 In the use of a specific dosimetry system, absorbed dose
precision of 61 % of the film thickness at the 95 % confidence
is evaluated by the use of a calibration curve or response
level.
function traceable to nationally or internationally recognized
standards.
6. Preparation of Dosimeters
4.3 Absorbed dose that is measured is usually specified in
6.1 Cellulose acetate dosimeters can be prepared by pouring
water. Absorbed dose in other materials may be evaluated by
a prescribed recipe solution (for example, see Ref. 5) consist-
applying the conversion factors discussed in ISO/ASTM Guide
ing of cellulose diacetate or triacetate, plasticizer, dye, and
51261.
solvent onto an optical flat plate and evaporating the solvent
NOTE 3—For a comprehensive discussion of various dosimetry meth- slowly and gently. The thickness of the film can be controlled
ods applicable to the radiation types and energies discussed in this
by the concentration of solutes or by the amount of solution
practice, see ICRU Reports 14, 17, 34, 35, and 37.
poured on to a given area of the horizontal plate.
4.4 These dosimetry systems may be used in the industrial 6.1.1 For both untinted and tinted CTA dosimeter films, the
recommended recipe is 85 weight % of cellulose triacetate and
radiation processing of various products, for example radiation
effects tests, polymer modifications, and sterilization of medi- balance of triphenyl phosphate (TPP) as a sole plasticizer, plus
compatible kinds and amounts of solvents, for example,
cal devices.
4.5 The available dynamic ranges indicated in 1.2.1 and methylenechloride-methanol mixture (18).
6.2 In-house preparation of cellulose acetate dosimeters has
1.2.2 are achieved by using a variety of plasticizer and dye
an advantage that the film thickness can be adjusted according
concentrations in the CTA and CDA systems.
to the intended application, the measurable dose range and the
4.6 The difference in dose response due to changes in the
range of the electron beam. The disadvantage lies in the
parameters of the irradiation conditions, such as dose rate,
temperature, humidity, and atmosphere should be considered difficulty in making a large size film of constant thickness.
Such film may be used for small size dosimeters but, unless the
when these are different from the parameters of the calibration.
NOTE 4—The dose response of the CTA dosimeter increases linearly
with temperature (−10 to 40°C) and relative humidity (20 to 80 %) when
irradiated at lower dose-rates (<10 kGy/h) typical of gamma-irradiators.
The effects are found to be less severe at the higher dose-rates for electron
irradiators (>100 kGy/h). Moreover, as mentioned in Ref 16, these effects
are known to vary from batch to batch. All these effects need to be
considered before CTA dosimeters can be used routinely for processing
(6,9,11,12,16,17, and 20).
6
5. Apparatus
5.1 The following shall be used to evaluate absorbed dose
with cellulose acetate dosimetry systems:
5.1.1 A batch or portion of a batch of cellulose acetate film. NOTE—The suggested wavelength of 280 nm is chosen due to low
absorbance before irradiation (A ), and linear absorbance (A) increase
o
with dose. (Original drawing by the author of Refs 1,2, and 19).
6
Corning S5-58, available from Corning, Inc., Technical Products Division, FIG. 1 Absorption Spectra Before and After Irradiation of
Advanced Materials Dept., Main Plant 21-3, Corning, NY 14831, USA, has been Untinted Cellulose Triacetate (CTA) Film with a 2 MeV Electron
found satisfactory. Beam
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ISO/ASTM 51650:2002(E)
7
NOTE 1—O: electron beam (dose rate: 10 /Gy/h, temperature: 15°C,
4
relative humidity: 60 %). •: gamma-rays (dose rate: 10 /Gy/h, temperature
25°C, relative humidity: 50 to 60 %).
NOTE 2—The DA values were measured 2 h after irradiation (19).
FIG. 2 The Relation Between the Increment of Absorbance DA/
Nominal Thickness (0.125 mm) at 280 nm and Dose in Untinted
CTA by Electron and Gamma-Radiation
thickness is uniform, may not be used as long strips or large
size films for continuous dose mapping purposes.
6.3 Some CTA and CDA films are commercially available,
and are described in the nonmandatory annex of this practice.
NOTE—The suggested wavelength for spectrophotometric analysis for
7. Calibration of the Dosimetry System
dosimetry is indicated by the vertical arrow. If the spectrophotometer or
7.1 Prior to use, the dosimetry system shall be calibrated in
densitometer is not able to measure very high absorbance (A = 4.55),
390 nm
measurement may be made at a higher wavelength on a shoulder of the
accordance with the user’s documented procedure that speci-
absorption spectrum (for example, at 410 nm) or using a broad band-pass
fies details of the calibration process and quality assurance
6
filter with a densitometer (16).
requirements. This calibration procedure shall be repeated at
FIG. 3 Absorption Spectra Before and After Irradiation to High
regular intervals to ensure that the accuracy of the absorbed
60
Doses (Using Co g Rays, 0.4- and 10-MeV Electron Beams) of
dose measurement is maintained within required limits. De-
Yellow Cellulose Diacetate (CDA) Film
tailed calibration procedures are provided in ISO/ASTM Guide
51261.
verified at periodic intervals. These calibrations shall be
7.2 Calibration Irradiation of Dosimeters—Irradiation is a
traceable to nationally or internationally recognized standards.
critical component of the calibration of the dosimetry system.
For example, if an optical absorbance-measuring instrument
Calibration irradiations may be performed in several ways,
such as a spectrophotometer or densitometer is used, then
including irradiating the dosimeters using:
appropriate standards shall be used to verify the accuracy of the
7.2.1 a calibration facility that provides an absorbed dose or
optical absorbance at a specified wavelength(s). See ASTM
an absorbed-dose rate having measurement traceability to
Practices E 275, E 925, and E 958.
nationally or internationally recognized standards, or
8. Calibration of Cellulose Acetate Dosimeter
7.2.2 an in-house calibration facility that provides an ab-
sorbed dose or an absorbed-dose rate having measurement 8.1 Irradiation:
traceability to nationally or internationally recognized stan- 8.1.1 Randomly select five dosimeters from the batch or
dards, or stock and do not irradiate them. Use them for determining
7.2.3 a production or research irradiation facility together A (see 8.3.1).
o
with reference or transfer–standard dosimeters that have mea- 8.1.2 Select a set of at least four dosimeters for each
surement traceability to nationally or internationally recog- absorbed dose value.
nized standards. 8.1.3 Irradiate these sets of dosimeters to at least five known
7.3 Instrument Calibration—Calibrations of the individual dose values per decade covering the range of utilization, or at
instruments used in the analysis of the dosimeters shall be
least four sets if the range of use is less than one decade.
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ISO/ASTM 51650:2002(E)
FIG. 4 Increase in the Reciprocal of Absorbance (I/A), at 390 nm Wavelength, as a Function of Absorbed Dose (in Water), when Yellow
CDA is Irradiated with Electrons and Gamma Rays (16)
NOTE 5—If the dose range exceeds a decade, the number of values of
eter response during gamma-irradiation is about + 0.5 % per
dose, N, is calculated by the following equation:
°C.
N 5 Nearest integer @5 3 log ~D /D !# (7) 7
10 max min
NOTE 7—Untinted CTA (FTR-125) does not show appreciable tem-
For example, if the maximum dose range (D ) is 200 kGy, and the 6
max
perature dependence when used at dose rates of 10 Gy/h and higher (22).
minimum dose range (D )is10kGy,
min
Extremes in relative humidity affect the sensitivity. Therefore, avoid very
low (<20 %) and very high humidity conditions (>80 %). For high
N 5 Nearest integer @5 3 log ~200/10!# (8)
dose-rate dosimetry (for example, electron beams), the effect of humidity
5 Nearest integer @~5 3 1.301!#
differences on dosimeter response is less severe than at low dose rates (for
example, gamma radiation) (6,9). For high doses exceeding 200 kGy, CTA
5 Nearest integer @6.505#
film becomes brittle and must be handled with care.
5 7
8.1.10 Calibrate each batch or stock of dosimeters prior to
8.1.4 Specify the calibration dose in terms of absorbed dose
routine use, and at least once per year.
in water or in another material appropriate for the specific
8.2 Measurement:
application (for example, see ASTM Practice E 1026 and
8.2.1 Depending on the cellulose acetate dosimeter used
ISO/ASTM Practice 51205).
(see Table A1.1), set the spectrophotometer at the appropriate
8.1.5 Position the dosimeter in the calibration radiation field
wavelength at a band width of no more than 1 nm, or use
in a defined, reproducible location.
photometer or densitometer equipped with an appropriate
8.1.6 When using photon radiation for calibration, surround
band-pass filter or hollow cathode lamp or light-emitting diode
the dosimeters with a sufficient amount of water-equivalent
(LED) of appropriate wavelength.
material to ensure approximate electron equilibrium condition.
8.2.2 Set the balance of the spectrophotometer, densitom-
60
NOTE 6—For example, for a Co gamma-ray source, this could be
eter, or photometer to zero absorbance, without a film dosim-
accomplished by surrounding the dosimeter with 3 to 5 mm of polymeric
eter (with only air) in the analytical light beam.
material, (for example, polystyrene) in all directions.
8.2.3 Insert the non-irradiated film dosimeter in the holder
8.1.7 When using an electron beam for the calibration, and insert it in the analytical light beam of the spectrophotom-
locate the dosimeter in a well characterized position within the eter, densitometer, or photometer. Measure the absorbance with
radiation field (17,21). only air in the reference light beam. Record this value (A ).
o
8.1.8 Make the calibration field within the volume occupied With use of the scanning spectrophotometer, densitometer, or
by the dosimeter(s) as uniform as possible. The variation in photometer, read the average value of absorbance with air as
dose rate within the occupied volume should be within 61%. the reference. Record these values (A ).
o
8.1.9 Control (or monitor) the temperature and humidity of 8.2.4 Insert the irradiated dosimeter film in the analytical
the dosimeters during irradiation. Take into account any light beam of the spectrophotometer, densitometer, or photom-
temperature and humidity variation that can affect dosi
...