ASTM E2450-05

Standard Practice for Application of CaF<inf>2</inf>(Mn) Thermoluminescence Dosimeters in Mixed Neutron-Photon Environments

SCOPE
1.1 This practice describes a procedure for measuring gamma-ray absorbed dose in CaF2(Mn) thermoluminescence dosimeters (TLDs) exposed to mixed neutron-photon environments during irradiation of materials and devices. The practice has broad application, but is primarily intended for use in the radiation-hardness testing of electronics. The practice is applicable to the measurement of absorbed dose from gamma radiation present in fields used for neutron testing.
1.2 This practice describes a procedure for correcting for the neutron response of a CaF2(Mn) TLD. The neutron response may be subtracted from the total response to give the gamma-ray response. In fields with a large neutron contribution to the total response, this procedure may result in large uncertainties.
1.3 More precise experimental techniques may be applied if the uncertainty derived from this practice is larger than the user can accept. These techniques are not discussed here. The references in Section 8 describe some of these techniques.
1.4 This practice does not discuss effects on the TLD reading of neutron interactions with material surrounding the TLD to ensure charged particle equilibrium. These effects depend on the surrounding material and its thickness, and on the neutron spectrum (1).²

General Information

• Status: Historical
• Publication Date: 31-May-2005
• ICS: 17.240 - Radiation measurements
• Technical Committee: E10 - Nuclear Technology and Applications
• Drafting Committee: E10.07 - Radiation Dosimetry for Radiation Effects on Materials and Devices

Relations

• Replaced By: ASTM E2450-06 - Standard Practice for Application of CaF<inf>2</inf>(Mn) Thermoluminescence Dosimeters in Mixed Neutron-Photon Environments
• Effective Date: 01-May-2006
• Referred By: ASTM E668-20 - Standard Practice for Application of Thermoluminescence-Dosimetry (TLD) Systems for Determining Absorbed Dose in Radiation-Hardness Testing of Electronic Devices
• Effective Date: 01-Jun-2005
• Referred By: ASTM E1855-20 - Standard Test Method for Use of 2N2222A Silicon Bipolar Transistors as Neutron Spectrum Sensors and Displacement Damage Monitors
• Effective Date: 01-Jun-2005
• Referred By: ASTM F1190-18 - Standard Guide for Neutron Irradiation of Unbiased Electronic Components
• Effective Date: 01-Jun-2005
• Referred By: ASTM E1854-19 - Standard Practice for Ensuring Test Consistency in Neutron-Induced Displacement Damage of Electronic Parts
• Effective Date: 01-Jun-2005

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation:E2450–05
Standard Practice for
Application of CaF (Mn) Thermoluminescence Dosimeters in
Mixed Neutron-Photon Environments
This standard is issued under the fixed designation E 2450; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope E 720 Guide for Selection and Use of Neutron-Activation
Foils for Determining Neutron Spectra Employed in
1.1 This practice describes a procedure for measuring
Radiation-Hardness Testing of Electronics
gamma-ray absorbed dose in CaF (Mn) thermoluminescence
E 721 Guide for Determining Neutron Energy Spectra from
dosimeters (TLDs) exposed to mixed neutron-photon environ-
Neutron Sensors for Radiation-Hardness Testing of Elec-
ments during irradiation of materials and devices. The practice
tronics
has broad application, but is primarily intended for use in the
E 722 Practice for Characterizing Neutron Energy Fluence
radiation-hardness testing of electronics. The practice is appli-
Spectra in Terms of an Equivalent Monoenergetic Neutron
cable to the measurement of absorbed dose from gamma
Fluence for Radiation-Hardness Testing of Electronics
radiation present in fields used for neutron testing.
E 1854 Practice for Assuring Test Consistency in Neutron-
1.2 Thispracticedescribesaprocedureforcorrectingforthe
Induced Displacement Damage of Electronic Parts
neutron response of a CaF (Mn) TLD. The neutron response
F 1190 Guide for Neutron Irradiation of Unbiased Elec-
may be subtracted from the total response to give the gamma-
tronic Components
ray response. In fields with a large neutron contribution to the
total response, this procedure may result in large uncertainties.
3. Terminology
1.3 More precise experimental techniques may be applied if
3.1 Definitions:
theuncertaintyderivedfromthispracticeislargerthantheuser
3.1.1 absorbed dose—see Terminology E 170.
can accept. These techniques are not discussed here. The
3.1.2 exposure—see Terminology E 170.
references in Section 8 describe some of these techniques.
3.1.3 kerma—see Terminology E 170.
1.4 This practice does not discuss effects on the TLD
3.1.4 linear energy transfer (LET)—the energy loss per unit
reading of neutron interactions with material surrounding the
distance as a charged particle passes through a material.
TLD to ensure charged particle equilibrium. These effects
Electrons resulting from gamma-ray interactions in a material
depend on the surrounding material and its thickness, and on
2 generally have a low LET. Heavy charged particles resulting
the neutron spectrum (1).
from neutron interactions with a material generally have a high
2. Referenced Documents LET.
3 3.1.5 neutron sensitivity m(E)—the ratio of the detector
2.1 ASTM Standards:
reading, that is, the effective neutron dose, to the neutron
E 170 Terminology Relating to Radiation Measurements
fluence. Thus,
and Dosimetry
E 666 PracticeforCalculatingAbsorbedDosefromGamma M~E!
m~E! 5 (1)
or X Radiation F~E!
E 668 Practice forApplication of Thermoluminescence Do-
where:
simetry (TLD) Systems for DeterminingAbsorbed Dose in
F(E) = the neutron fluence, and
Radiation-Hardness Testing of Electronics
M(E) = the apparent dose (extra light output) in the TLD
caused by neutrons of energy E.
This practice is under the jurisdiction of ASTM Committee E10 on Nuclear
4. Significance and Use
Technology and Applications and is the direct responsibility of Subcommittee
E10.07 on Radiation Dosimetry for Radiation Effects on Materials and Devices.
4.1 Electronic devices are typically tested for survivability
Current edition approved June 1, 2005. Published July 2005.
against gamma radiation in pure gamma-ray fields. Testing
The boldface numbers in parentheses refer to the list of references at the end of
their response against neutrons is more complex since there is
this standard.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
invariably a gamma-ray component to the neutron field. The
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
gamma-ray response of the device is subtracted from the
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E2450–05
overall response to find the response to neutrons. This testing 6. Neutron Sensitivity of CaF (Mn)
thusrequiresadeterminationofthegamma-rayexposureinthe
6.1 Thermal Neutrons:
mixed field. To enhance the neutron effects, the field is
6.1.1 Thermal neutron responses of CaF (Mn) ranging from
sometimes selected to have as large a neutron component as
10 2
0.06 to 0.89 rad(CaF (Mn)) per 10 n/cm are reported (2).
possible.
The sensitivity may depend on the manganese doping of the
4.2 CaF (Mn) thermoluminescent detectors are often used
TLD. The sensitivity may also be a function of dosimeter size,
to monitor the gamma-ray dose for this type of testing. Since
since the dosimeter surface-to-volume ratio affects the portion
they are exposed along with the device under test to the mixed
of the charged particles born within the TLD that deposit their
field, their response must be corrected for neutrons. In a field
dose outside the TLD. Horowitz (3) calculates a thermal
rich in neutrons, the uncertainty in the TLD response grows, 10 2
neutron response of 0.34 rad(CaF ) per 10 n/cm for
butthismaybeunimportantsincethegamma-rayeffectsonthe
CaF (Mn (2 % by weight)) for TLD of dimensions 0.165 by
device under test may be relatively small. In fields with
0.165 by 0.083 cm.
relatively few neutrons, the TLD response may be used to
make a relatively large correction for gamma response on the NOTE 1—Thermal neutron response is typically reported in terms of
TLD response relative to a Co-60 equivalent Roentgen (R)/n/cm . For
device under test. Under this condition, the relative uncertainty
Co-60 decay gamma rays, the conversion from Roentgen to rad(air) is
in the TLD response shrinks.
0.869 rad(air)/R.The conversion from rad(air) to rad(CaF ) is 0.975.Thus
4.3 This practice gives a means of estimating the response
rad(CaF ) is 0.85 times the exposure in Roentgen.
of CaF (Mn) to neutrons. This neutron response is then
6.1.2 Avalue of 0.45 6 0.45 rad (1 s) (CaF (Mn)) per 10
subtracted from the measured response to give the response to
thermal n/cm shall be used for CaF (Mn) TLDs.
gamma rays. The procedure has relatively high uncertainty
because the neutron response of CaF (Mn) may vary depend-
2 NOTE 2—The variation in measured thermal neutron sensitivities for
ing on the source of the material, and this procedure is a
CaF (Mn) is as large as the average sensitivity.
generic calculation applicable to CaF (Mn) independent of
6.2 Fast Neutrons—A recommended fast-neutron response
source. The neutron response given in this practice is a
is displayed in Fig. 1 and listed in Table 1. For the purpose of
summary of responses reported in the literature.The associated
this practice, the fast-neutron response is the response due to
uncertaintyenvelopstherangeofresultsreported,andincludes
all neutrons above 0.4 eV. Table 1 is the Rinard (4) response
the variety of TLDs used as well as the uncertainties in the
function multiplied by 1.2. The factor of 1.2 was used to scale
determination of the neutron response as reported by various
the response function to give an optimal fit to a variety of
authors.
measured data. See Fig. 2 for the quality of this coverage. Use
4.4 Should the user find the resulting uncertainties too large
this response to calculate the fast neutron response in rad-
forhispurposes,theneutronresponseoftheparticularTLDsin
(CaF ).
use must be determined. This practice does not supply guid-
ance on how to determine the neutron response of a specific
Response 5 R~E!· F~E!dE (2)
*
batch of TLDs.
where R(E) is taken from Table 1 and F(E) is the neutron
4.5 Neutron effects on electronics under test are usually
-2 -1
spectrum in n·cm ·MeV . Take the 1 s uncertainty in this
reported in terms of 1 MeV equivalent fluence (E 722).
response as 50 % of the calculated value.
Neutron effects of TLDs, as discussed here, are reported in
6.3 Subtractthethermalandfastneutronresponsesfromthe
rads, since they are corrections to the gamma-ray dose.
measured responses to obtain the gamma-ray response:
5. Exposure Procedure D 5 D 2 D 2 D (3)
G Meas Thermal Fast
5.1 Determine the neutron and gamma-ray environments. 6.3.1 The uncertainties are added in quadrature:
Calculate the relative neutron response of the TLDs. If this
2 2 2
s 5 s 1s 1s (4)
=
D D D D
G Meas Thermal Fast
response is negligible, document this result. No further mea-
surements are required for the purpose of neutron sensitivity of
7. Reporting
the TLDs.
5.2 Expose the TLD along with the device under test (see 7.1 The gamma-ray dose is reported after the neutron
Practice E 1854 and Gui
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