ASTM E668-00
(Practice)Standard Practice for Application of Thermoluminescence-Dosimetry (TLD) Systems for Determining Absorbed Dose in Radiation-Hardness Testing of Electronic Devices
Standard Practice for Application of Thermoluminescence-Dosimetry (TLD) Systems for Determining Absorbed Dose in Radiation-Hardness Testing of Electronic Devices
SCOPE
1.1 This practice covers procedures for the use of thermoluminescence dosimeters (TLDs) to determine the absorbed dose in a material irradiated by ionizing radiation. Although some elements of the procedures have broader application, the specific area of concern is radiation-hardness testing of electronic devices. This practice is applicable to the measurement of absorbed dose in materials irradiated by gamma rays, X rays, and electrons of energies from 12 to 60 MeV. Specific energy limits are covered in appropriate sections describing specific applications of the procedures. The range of absorbed dose covered is approximately from 10 -2 to 104 Gy (1 to 106 rad), and the range of absorbed dose rates is approximately from 10 -2 to 10 10 Gy/s (1 to 10 12 rad/s). Absorbed dose and absorbed dose-rate measurements in materials subjected to neutron irradiation are not covered in this practice. Further, the portion of these procedures that deal with electron irradiation are primarily intended for use in parts testing. Testing of devices as a part of more massive components such as electronics boards or boxes may require techniques outside the scope of this practice. Note 1-The purpose of the upper and lower limits on the energy for electron irradiation is to approach a limiting case where dosimetry is simplified. Specifically, the dosimetry methodology specified requires that the following three limiting conditions be approached: (a) energy loss of the primary electrons is small, (b) secondary electrons are largely stopped within the dosimeter, and (c) bremsstrahlung radiation generated by the primary electrons is largely lost.
1.2 This standard does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation:E668–00
Standard Practice for
Application of Thermoluminescence-Dosimetry (TLD)
Systems for Determining Absorbed Dose in Radiation-
Hardness Testing of Electronic Devices
This standard is issued under the fixed designation E668; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope E170 Terminology Relating to Radiation Measurements
and Dosimetry
1.1 This practice covers procedures for the use of thermolu-
E380 Practice for Use of the International System of Units
minescencedosimeters(TLDs)todeterminetheabsorbeddose
(SI) (the Modernized Metric System)
in a material irradiated by ionizing radiation. Although some
E665 Practice for Determining Absorbed Dose Versus
elements of the procedures have broader application, the
Depth in Materials Exposed to the X-ray Output of Flash
specific area of concern is radiation-hardness testing of elec-
X-Ray Machines
tronic devices. This practice is applicable to the measurement
E666 PracticeforCalculatingAbsorbedDosefromGamma
of absorbed dose in materials irradiated by gamma rays, X
or X Radiation
rays, and electrons of energies from 12 to 60 MeV. Specific
2.2 International Commission on Radiation Units and
energy limits are covered in appropriate sections describing
Measurements (ICRU) Reports:
specific applications of the procedures. The range of absorbed
−2 4 6
ICRU Report 14—Radiation Dosimetry: X Rays and
dose covered is approximately from 10 to 10 Gy (1 to 10
Gamma Rays with Maximum Photon Energies Between
rad), and the range of absorbed dose rates is approximately
−2 10 12
0.6 and 50 MeV
from 10 to 10 Gy/s (1 to 10 rad/s). Absorbed dose and
ICRU Report 17—Radiation Dosimetry: X Rays Generated
absorbed dose-rate measurements in materials subjected to
at Potentials of 5 to 150 keV
neutronirradiationarenotcoveredinthispractice.Further,the
ICRUReport 21—RadiationDosimetry:ElectronswithIni-
portion of these procedures that deal with electron irradiation
tial Energies Between 1 and 50 MeV
are primarily intended for use in parts testing. Testing of
ICRU Report 31—Average Energy Required to Produce an
devices as a part of more massive components such as
Ion Pair
electronics boards or boxes may require techniques outside the
ICRU Report 33—Radiation Quantities and Units
scope of this practice.
ICRU Report 34—The Dosimetry of Pulsed Radiation
NOTE 1—The purpose of the upper and lower limits on the energy for
ICRU Report 37—Stopping Powers for Electrons and
electron irradiation is to approach a limiting case where dosimetry is
Positrons
simplified.Specifically,thedosimetrymethodologyspecifiedrequiresthat
the following three limiting conditions be approached: (a) energy loss of
3. Terminology
the primary electrons is small, (b) secondary electrons are largely stopped
3.1 Definitions:
within the dosimeter, and (c) bremsstrahlung radiation generated by the
primary electrons is largely lost. 3.1.1 absorbed dose, D—thequotientofde¯bydm,wherede¯
isthemeanenergyimpartedbyionizingradiationtothematter
1.2 This standard dose not purport to address all of the
in a volume element and dm is the mass of matter in that
safety concerns, if any, associated with its use. It is the
volume element.
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica- de¯
D 5 (1)
dm
bility of regulatory limitations prior to use.
Previously, the special unit of absorbed dose was the rad;
2. Referenced Documents
however, the gray (Gy) has been adopted as the official SI unit
2.1 ASTM Standards:
(see Practice E380).
This practice is under the jurisdiction of ASTM Committee E10 on Nuclear
Technology and Applications and is the direct responsibility of Subcommittee Annual Book of ASTM Standards, Vol 12.02.
E10.07 on Radiation Dosimetry for Radiation Effects on Materials and Devices. Annual Book of ASTM Standards, Vol 14.02.
Current edition approved June 10, 2000. Published July 2000. Originally Available from International Commission on Radiation Units and Measure-
published as E668–78. Last previous edition E668–97. ments, 7910, Woodmont Ave., Suite 800, Bethesda, MD 20814.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E668
21 2
3.1.11 test conditions—the normal environmental condi-
1Gy 51J·kg 510 rad (2)
tions prevailing during routine hardness-test irradiations such
3.1.2 absorbed-dose rate—the absorbed dose per unit time
as the ambient temperature, humidity, and lighting.
interval.
3.1.12 thermoluminescence dosimeter (TLD)—a TL phos-
3.1.3 annealing—thermal treatment of a TLD prior to
phor,alone,orincorporatedinamaterial,usedfordetermining
irradiation or prior to readout.
the absorbed dose in materials. For example, the TL phosphor
3.1.3.1 Discussion—Pre-irradiation annealing of TLDs is
is sometimes incorporated in a TFE-fluorocarbon matrix.
usually done to erase the effects of previous irradiation and to
3.1.13 thermoluminescence dosimeter (TLD) batch—a
readjust the sensitivity of the phosphor; pre-readout annealing
group of TLDs, generally originating from a single mix or lot
usually is done to reduce low-temperature TLD response.
of TL phosphor, having similar TL responses and similar
3.1.4 calibration conditions—the normal environmental
thermal and irradiation histories.
conditions prevailing during routine calibration irradiations
3.1.14 thermoluminescencedosimeter(TLD)reader—anin-
such as the ambient temperature, humidity, and lighting.
strument used to measure the light emitted from a TLD
3.1.5 equilibrium absorbed dose—the absorbed dose at
consisting essentially of a heating element, a light-measuring
some incremental volume within the material which the
device, and appropriate electronics.
conditionofelectronequilibrium(asmanyelectronsofagiven
3.1.15 thermoluminescence dosimeter (TLD) response—the
energy enter as leave the volume) exists (1) (see Appendix
measured light emitted by the TLD and read out during its
X1).
heating cycle consisting of one of the following: (a) the total
3.1.6 exposure, X—the quotient of dQ by dm, where dQ is
lightoutputovertheentireheatingcycle,(b)apartofthattotal
the absolute value of the total charge of the ions of one sign
light output, or (c) the peak amplitude of the light output.
producedinairwhenalltheelectrons(negatronsandpositrons)
3.1.16 thermoluminescence (TL) phosphor—a material that
liberated by photons in a volume element of air having mass
stores, upon irradiation, a fraction of its absorbed dose in
dm are completely stopped in air.
various excited energy states. When thermally stimulated, the
dQ
material emits this stored energy in the form of photons in the
X 5 (3)
dm
ultraviolet, visible, and infrared regions.
−1
3.1.17 TLD preparation—the procedure of cleaning, an-
UnitC·kg
nealing,andencapsulatingtheTLphosphorpriortoirradiation.
3.1.6.1 Discussion—Formerly the special unit of exposure
3.2 For units and terminology in reports of data, Terminol-
was the roentgen (R).
ogy E170 may be used as a guide.
21 21
1 R 52.58 310 C·kg ~exactly! (4)
4. Significance and Use
3.1.7 primary electrons—for the case of electron irradia-
4.1 Absorbed dose in a material is an important parameter
tion, the electrons introduced into the device under test by the
that can be correlated with radiation effects produced in
irradiation source.
electroniccomponentsanddevicesthatareexposedtoionizing
3.1.8 secondary-electron equilibrium—for the case of elec-
radiation. Reasonable estimates of this parameter can be
tron irradiation, the condition where as many secondary
calculated if knowledge of the source radiation field (that is,
electrons of a given energy enter a given volume as leave it.
energy spectrum and particle fluence) is available. Sufficiently
3.1.9 secondary-electron equilibrium absorbed dose—for
detailed information about the radiation field is generally not
the case of electron irradiation, the absorbed dose at some
available. However, measurements of absorbed dose with
incremental volume within the material in which the condition
passive dosimeters in a radiation test facility can provide
of secondary-electron equilibrium exists.
information from which the absorbed dose in a material of
3.1.9.1 Discussion—Additional definitions can be found in
interest can be inferred. Under certain prescribed conditions,
ICRU Report 33.
TLDs are quite suitable for performing such measurements.
3.1.10 secondary electrons—for the case of electron irra-
NOTE 2—Forcomprehensivediscussionsofvariousdosimetrymethods
diation, electrons knocked out of the electron shells of the
applicable to the radiation types and energy and absorbed dose-rate range
material being irradiated by the primary electron. For the case
discussed in this practice, see ICRU Reports 14, 17, 21, and 34.
of photon irradiation, energetic electrons (photoelectrons,
Auger electrons, and Compton electrons) produced within the
5. Apparatus
material being irradiated by the action of the incident photons.
5.1 The TLD System consists of the TLDs, the equipment
3.1.10.1 Discussion—Secondary electrons are produced by
used for preparation of the TLDs, and the TLD reader.
the interaction of the primary electrons with the atoms of the
5.2 Calibration Facility deliversaknownquantityofradia-
material being irradiated. This interaction is a principal means
tion to materials under certain prescribed environmental and
of energy loss for the primary electrons. The kinetic energy of
geometrical conditions. Its radiation source is usually a radio-
a secondary electron is typically much lower than that of the
60 137
activeisotope,commonlyeither Coor Cs,whoseradiation
primary electron which creates it.
output has been calibrated by specific techniques to some
specified uncertainty (usually to within 65%) and is traceable
to national standards.
5.3 Storage Facility provides an environment for theTLDs
Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof
this practice. before and after irradiation, that is light tight and that has a
E668
negligiblebackgroundabsorbed-doserate.ATLDstoredinthe 7. Summary of Requirements for Performance Testing of
facility for the longest expected storage period should absorb a TLD System
no more than 1% of the lowest absorbed dose expected to be
7.1 The performance of a specific TLD system should be
measured in hardness-testing applications.
evaluated to determine its suitability for use in a specific
5.4 Environmental Chamber isusedintestingtheeffectsof radiation-hardness test. Acceptable performance of the TLD
temperature and humidity on TLD response. The chamber system should be verified before applying the system in a
particular radiation-hardness-testing facility. Specific perfor-
should be capable of controlling the temperature and humidity
mance criteria will be discussed in Section 8.
within 65% over the range expected under both calibration
7.2 Performance tests should be repeated whenever a sig-
and test conditions.
nificant change is made in the TLD system or in the specific
application. Examples of such changes are: a change in the
6. Handling and Readout Procedures
physical form or type of phosphor in theTLD, a change in any
6.1 Bare TLDs should not be handled with the bare fingers;
critical component or in any adjustable readout factor of the
dirtorgreaseontheirsurfacescanaffecttheirresponseandcan
TLD reader, or a change in the irradiation source characteris-
contaminatetheheatingchamberoftheTLDreader.Avacuum
tics.
pen or tweezers coated with TFE-fluorocarbon should be used
7.3 A particular performance test may be omitted if widely
in handling. If required, the TLDs can be cleaned by using the
accepted documentation exists in the scientific and technical
procedures in accordance with Appendix X2.
literature to show that the performance of the TLD system is
6.2 TLDs, especially those with high sensitivity, should be satisfactory for that specific requirement. For example, if
protected from light having an appreciable ultraviolet compo- previously accepted studies document that a particular TLD
nent, such as sunlight or fluorescent light. Prolonged exposure has no absorbed-dose-rate dependence for the expected condi-
tions of irradiation, then performance testing for absorbed-
to ultraviolet light, either before or after irradiation, can cause
dose-rate dependence of that TLD system is unnecessary. All
spurious TLD response or enhanced post-irradiation fading.
reportsoftestresultsshouldincludeappropriatereferencesthat
Incandescent lighting should be used for the TLD preparation
substantiate the performance of the system and thereby justify
and readout areas. However, brief exposures of a few minutes
the omission of such performance tests.
tonormalroomfluorescentlightingisnotlikelytosignificantly
7.4 IfaparticularTLDsystemfailstomeettheperformance
affect the TLD response except for low absorbed-dose mea-
specification of any performance test, then use of that TLD
surements (<1 Gy or <100 rad) or measurements with high-
system is not recommended. Such a system may be used only
sensitivity TLDs.
if appropriate corrections to the TLD response can be deter-
6.3 Preparation of the TLDs for irradiation consists of
mined sufficiently well in order that the results of the specific
cleaning the TL phosphor (if required), annealing (if reusable
radiation-hardness test can be determined within the required
TLDs are employed), and encapsulating the TL phosphor.
uncertainty.
Reusable TLDs require careful treatment during annealing in
7.5 The number of TLDs, or the number of replicates of
order to obtain the best results in dose measurements. The
measurements with a single TLD, used for each test should be
annealingprocedureshouldincludeareproducibletemperature
sufficient to assure that the test results are significant at the
cycle of the annealing oven, accurate timing of the annealing
95% confidence level. See Ref 2 for details of the procedures
period, and a reproducible cooling rate.
usedtoselectrandomsamplesandtodeterminethesamplesize
6.4 For low absorbed-dose measurements (<1 Gy (100
required.
rad)), dry nitrogen should be flowed through the heating
NOTE 3—Ifasampleof nmeasurements Y , Y ,., Y istaken,thebest
1 2 n
chamberoftheTLDreaderduringreadout.Thissuppressesthe
estimate of the population mean, m, of a normal distribution is given by
spurious TLD response that occurs in most forms of TLDs as
¯
the mean value, Y, of the s
...
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