ASTM E722-94(2002)

Standard Practice for Characterizing Neutron Energy Fluence Spectra in Terms of an Equivalent Monoenergetic Neutron Fluence for Radiation-Hardness Testing of Electronics

SCOPE
1.1 This practice covers procedures for characterizing a neutron fluence from a source in terms of an equivalent monoenergetic neutron fluence. It is applicable to neutron effects testing, to the development of test specifications, and to the characterization of neutron test environments. The sources may have a broad neutron-energy spectrum, or may be mono-energetic neutron sources with energies up to 20 MeV. The relevant equivalence is in terms of a specified effect on certain physical properties of materials upon which the source spectrum is incident. In order to achieve this, knowledge of the effects of neutrons as a function of energy on the specific property of the material of interest is required. Sharp variations in the effects with neutron energy may limit the usefulness of this practice in the case of mono-energetic sources.
1.2 This practice is presented in a manner to be of general application to a variety of materials and sources. Correlation between displacements () caused by different particles (electrons, neutrons, protons, and heavy ions) is beyond the scope of this practice. In radiation-hardness testing of electronic semiconductor devices, specific materials of interest include silicon and gallium arsenide, and the neutron sources generally are test and research reactors and californium-252 irradiators.
1.3 The technique involved relies on the following factors: (1) a detailed determination of the energy spectrum of the neutron source, and (2) a knowledge of the degradation (damage) effects of neutrons as a function of energy on specific material properties.
1.4 The detailed determination of the neutron energy spectrum referred to in need not be performed afresh for each test exposure, provided the exposure conditions are repeatable. When the spectrum determination is not repeated, a neutron fluence monitor shall be used for each test exposure.
1.5 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 and health practices and determine the applicability of regulatory limitations prior to use.

General Information

• Status: Historical
• Publication Date: 14-Sep-1994
• ICS: 31.080.01 - Semiconductor devices in general
• Technical Committee: E10 - Nuclear Technology and Applications
• Drafting Committee: E10.07 - Radiation Dosimetry for Radiation Effects on Materials and Devices

Relations

• Replaced By: ASTM E722-04 - Standard Practice for Characterizing Neutron Energy Fluence Spectra in Terms of an Equivalent Monoenergetic Neutron Fluence for Radiation-Hardness Testing of Electronics
• Effective Date: 01-Jun-2004
• Referred By: ASTM F1190-18 - Standard Guide for Neutron Irradiation of Unbiased Electronic Components
• Effective Date: 15-Sep-1994
• Referred By: ASTM E261-16(2021) - Standard Practice for Determining Neutron Fluence, Fluence Rate, and Spectra by Radioactivation Techniques
• Effective Date: 15-Sep-1994
• Referred By: ASTM E170-23 - Standard Terminology Relating to Radiation Measurements and Dosimetry
• Effective Date: 15-Sep-1994
• Referred By: ASTM E2450-23 - Standard Practice for Application of CaF<inf>2</inf>(Mn) Thermoluminescence Dosimeters in Mixed Neutron-Photon Environments
• Effective Date: 15-Sep-1994
• Referred By: ASTM F980-16 - Standard Guide for Measurement of Rapid Annealing of Neutron-Induced Displacement Damage in Silicon Semiconductor Devices
• Effective Date: 15-Sep-1994
• Referred By: ASTM E721-22 - Standard Guide for Determining Neutron Energy Spectra from Neutron Sensors for Radiation-Hardness Testing of Electronics
• Effective Date: 15-Sep-1994
• 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: 15-Sep-1994
• Referred By: ASTM E1854-19 - Standard Practice for Ensuring Test Consistency in Neutron-Induced Displacement Damage of Electronic Parts
• Effective Date: 15-Sep-1994
• Referred By: ASTM E3084-17(2022)e1 - Standard Practice for Characterizing Particle Irradiations of Materials in Terms of Non-Ionizing Energy Loss (NIEL)
• Effective Date: 15-Sep-1994

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: E 722 – 94 (Reapproved 2002)
Standard Practice for
Characterizing Neutron Energy Fluence Spectra in Terms of
an Equivalent Monoenergetic Neutron Fluence for
Radiation-Hardness Testing of Electronics
This standard is issued under the fixed designation E 722; 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.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope test exposure, provided the exposure conditions are repeatable.
When the spectrum determination is not repeated, a neutron
1.1 This practice covers procedures for characterizing a
fluence monitor shall be used for each test exposure.
neutron fluence from a source in terms of an equivalent
1.5 This standard does not purport to address all of the
monoenergetic neutron fluence. It is applicable to neutron
safety concerns, if any, associated with its use. It is the
effects testing, to the development of test specifications, and to
responsibility of the user of this standard to establish appro-
the characterization of neutron test environments. The sources
priate safety and health practices and determine the applica-
may have a broad neutron-energy spectrum, or may be mono-
bility of regulatory limitations prior to use.
energetic neutron sources with energies up to 20 MeV. The
relevant equivalence is in terms of a specified effect on certain
2. Referenced Documents
physical properties of materials upon which the source spec-
2.1 ASTM Standards:
trum is incident. In order to achieve this, knowledge of the
E 265 Test Method for Measuring Reaction Rates for Fast-
effects of neutrons as a function of energy on the specific
Neutron Fluences by Radioactivation of Sulfur-32
property of the material of interest is required. Sharp variations
E 693 Practice for Characterizing Neutron Exposures in
in the effects with neutron energy may limit the usefulness of
Ferritic Steels in Terms of Displacement per Atom (DPA)
this practice in the case of mono-energetic sources.
E 720 Guide for Selection and Use of Neutron-Activation
1.2 This practice is presented in a manner to be of general
Foils for Determining Neutron Spectra Employed in
application to a variety of materials and sources. Correlation
2 Radiation-Hardness Testing of Electronics
between displacements (1-3) caused by different particles
E 721 Test Method for Determining Neutron Energy Spec-
(electrons, neutrons, protons, and heavy ions) is beyond the
tra with Neutron Activation Foils for Radiation-Hardness
scope of this practice. In radiation-hardness testing of elec-
Testing of Electronics
tronic semiconductor devices, specific materials of interest
E 844 Guide for Sensor Set Design and Irradiation for
include silicon and gallium arsenide, and the neutron sources
Reactor Surveillance, E706 (IIC)
generally are test and research reactors and californium-252
E 944 Practice for Applications of Neutron Spectrum Ad-
irradiators.
justment Methods in Reactor Surveillance, (IIA)
1.3 The technique involved relies on the following factors:
2.2 International Commission on Radiation Units and
(1) a detailed determination of the energy spectrum of the
Measurements (ICRU) Reports:
neutron source, and (2) a knowledge of the degradation
ICRU Report 13—Neutron Fluence, Neutron Spectra, and
(damage) effects of neutrons as a function of energy on specific
Kerma
material properties.
ICRU Report 26—Neutron Dosimetry for Biology and
1.4 The detailed determination of the neutron energy spec-
Medicine
trum referred to in 1.3 need not be performed afresh for each
ICRU Report 33—Radiation Quantities and Units
3. Terminology
This practice is under the jurisdiction of ASTM Committee E10 on Nuclear
3.1 Definitions of Terms Specific to This Standard:
Technology and Applicationsand is the direct responsibility of Subcommittee
E10.07on Radiation Dosimetry for Radiation Effects on Materials and Devices.
Current edition approved Sept. 15, 1994. Published November 1994. Originally
published as E 722 – 80. Last previous edition E 722 – 93. Annual Book of ASTM Standards, Vol 12.02.
2 4
The boldface numbers in parentheses refer to a list of references at the end of Available from International Commission on Radiation Units and Measure-
this practice. ments, 7910 Woodmont Ave., Bethesda, MD 20814.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E 722
3.1.1 displacement damage function—(F ) an energyde- kerma. Calculations of ionization and displacement kerma in
D,mat
pendent parameter proportional to the quotient of the observ- silicon and gallium arsenide as a result of irradiation by
able displacement damage per target atom and the neutron neutrons with energies up to 20 MeV are described in Refs 5-8
fluence. and in the annexes.
3.1.1.1 Discussion—Observable changes in a material’s
4. Summary of Practice
properties attributable to the atomic displacement process are
useful indices of displacement damage in that material. In
4.1 The equivalent monoenergetic neutron fluence, F -
eq,Eref
cases where the observed displacement damage is not in linear
,mat, is given as follows:
proportion to the applied fluence, the displacement damage
‘
F~E!F ~E!dE
* D,mat
function represents the quotient F (E)/dF, in the limiting
D,mat 0
F
eq,Eref,mat
case of zero fluence. Examples of suitable representations of
F
D,Eref,mat
(1)
displacement damage functions are given in the annexes. In the
case of silicon, it has been shown that the displacement damage
where:
function may be successfully equated with the displacement
F(E) = incident neutron energy-fluence spectral dis-
kerma factor. This question is discussed further in the annexes.
tribution,
3.1.2 displacement kerma factor—(K (E)) the energy
D,mat
F = neutron displacement damage function for
D,mat
dependent quotient of the displacement kerma per target atom
the irradiated material (displacement dam-
and the neutron fluence.
age per unit fluence) as a function of energy,
3.1.2.1 Discussion—This quantity may be calculated from
and
the microscopic neutron interaction cross sections, the kine-
F = displacement damage reference value desig-
D,Eref,mat
matic relations for each reaction and from a suitable partition
nated for the irradiated material and for the
function which divides the total kerma into ionization and
specified equivalent energy, Eref, as given
displacement kerma.
in the annexes.
3.1.3 energy-spectrum hardness parameter—(H
The energy limits on the integral are determined in practice
mat = F /F) this parameter is defined as the ratio of the
eq,Eref,mat by the incident-energy spectrum and by the material being
equivalent monoenergetic neutron fluence to the true total
irradiated.
fluence, F /F. The numerical value of the hardness
eq,Eref,mat 4.2 The neutron energy spectrum hardness parameter, H ,
mat
parameter is also equal to the fluence of monoenergetic
is given as follows:
neutrons at the specific energy, Eref, required to produce the
‘
F~E!F ~E!dE
same displacement damage in the specified material, mat unit
* D,mat
H 5 (2)
mat
fluence of neutrons of spectral distribution F(E). ‘
F F~E!dE
D,Eref,mat*
3.1.3.1 Discussion—For damage correlation, a convenient 0
method of characterizing the shape of an incident neutron
4.3 Once the neutron energy-fluence spectrum has been
energy-fluence spectrum F(E), is in terms of an energy
determined (for example, in accordance with Test Method
spectrum hardness parameter (4). The hardness parameter in a
E 721) and the equivalent monoenergetic fluence calculated,
particular neutron field depends on the displacement damage
then a monitor (such as an activation foil) can be used in
function used to compute the damage (see annexes) and is
subsequent irradiations at the same location to determine the
therefore different for different semiconductor materials.
fluence; that is, the neutron fluence is then described in terms
3.1.4 equivalent monoenergetic neutron fluence—(F -
of the equivalent monoenergetic neutron fluence per unit
eq,Eref
,mat) an equivalent monoenergetic neutron fluence, F ,
monitor response, F /M . Use of a monitor foil to
eq,Eref,mat eq,Eref,mat r
characterizes an incident energy-fluence spectrum, F(E), in
predict F is valid only if the energy spectrum remains
eq,Eref,mat
terms of the fluence of monoenergetic neutrons at a specific
constant.
energy Eref required to produce the same displacement damage
in a specified irradiated material, mat, as F(E). 5. Significance and Use
3.1.4.1 Discussion—Note that F is equivalent to
eq,Eref,mat 5.1 This practice is important in characterizing the radiation
F(E) if, and only if, the specific device effect (for example,
hardness of electronic devices irradiated by neutrons. This
current gain degradation in silicon) being correlated is de-
characterization makes it feasible to predict some changes in
scribed by the displacement damage function used in the
operational properties of irradiated semiconductor devices or
calculation.
electronic systems. To facilitate uniformity of the interpretation
3.1.5 kerma—(K (E)) the sum of the initial kinetic
and evaluation of results of irradiations by sources of different
mat
energies of all the charged particles liberated by indirectly
energy spectra, it is convenient to reduce the incident neutron
ionizing particles (for example, neutrons) in a volume element
fluence from a source to a single parameter—an equivalent
containing a unit mass of the specified material (see ICRU
monoenergetic neutron fluence—applicable to a particular
reports 13 and 33).
semiconductor material.
3.1.5.1 Discussion—When a material is irradiated by a 5.2 In order to determine an equivalent monoenergetic
neutron field, the energy imparted to the material may be neutron fluence, it is necessary to evaluate the displacement
described by the quantity kerma. The total kerma may be damage of the particular semiconductor material. Ideally, this
divided into two parts, ionization kerma and displacement quantity is correlated to the degradation of a specific functional
E 722
performance parameter (such as current gain) of the semicon- After F is determined and the monitor foil counted,
eq,Eref,mat
ductor device or system being tested. However, this correlation calculate the ratio of the equivalent monoenergetic fluence to
has not been established unequivocally for all device types and the unit monitor response, F /M .
eq,Eref,mat r
performance parameters since, in many instances, other effects 7.2 Use the response of the fast-neutron monitor foil, M,to
r
also can be important. Ionization effects produced by the predict F in subsequent routine device test irradia-
eq,Eref,mat
incident neutron fluence or by gamma rays in a mixed neutron tions. For this method to be valid, it is important to keep the
fluence, short-term and long-term annealing, and other factors source-foil geometry essentially identical to that used for
can contribute to observed performance degradation (damage). calibrating the monitor foil. Moderate changes in source-to-foil
Thus, caution should be exercised in making a correlation distance are allowable. In addition, make sure the source
between calculated displacement damage and performance location (of a Godiva-type reactor) with respect to scattering
degradation of a given electronic device. The types of devices materials (walls, floor, etc.) is the same. Do not change or
for which this correlation is applicable, and numerical evalu- move nearby scattering materials or moderators.
ation of displacement damage are discussed in the annexes. 7.3 Precautions in maintaining original calibration condi-
5.3 The concept of 1-MeV equivalent fluence is widely used tions are necessary to avoid altering the neutron energy
in the radiation-hardness testing community. It has merits and spectrum significantly in subsequent irradiations. An appre-
disadvantages that have been debated widely (9-12). For these ciable change in the spectrum will invalidate the calibration of
reasons, specifics of a standard application of the 1-MeV the monitor foil and, therefore, would necessitate a new
equivalent fluence are presented in the annexes. measurement of F(E) and recalibration of the monitor foil.
Whenever the neutron source configuration is changed, as for
6. Procedure for Calculating F
eq,Eref,mat
example, if the core fuel elements are replaced or rearranged in
6.1 To evaluate Eq 1 and 2, determine the energy limits E
a nuclear reactor, the activation foil spectrum measurements
min
and E to be used in place of zero and infinity in the integrals and all quantities derived from them may need to be remea-
max
of (Eq 1) and (Eq 2) and the values of the displacement damage
sured.
function F (E) for the irradiated material and perform the
7.4 The choice of a monitor foil material depends on several
D,mat
indicated integrations.
factors:
6.1.1 Choose the upper limit E to be at an energy above
7.4.1 The activation threshold should be high enough so as
max
which the integral damage falls to an insignificant level. For
to make it insensitive to neutrons below the E value used in
min
Godiva- or TRIGA-type spectra, this limit is about 12 MeV.
Eq 1 and 2. However, the threshold energy should be low
6.1.2 Choose the lower-energy limit E to be at an energy
enough to sample a significant fraction of the total fluence.
min
below which the integral damage falls to an insignificant level.
7.4.2 The monitor foil should have a high neutron sensitiv-
For silicon irradiated by Godiva-type spectra, this energy has
ity and a convenient half-life.
been historically chosen to be about 0.01 MeV. More highly
7.4.3 The detector system available for counting the moni-
moderated spectra may require lower thresholds or specialized
tor foil may dictate the choice of foil material. A germanium
54 58
filtering requirements such as a boron shield, or both.
gamma-ray detector system can be used, and Fe or Ni foils
6.1.3 The values of the neutron displacement damage func- utilized as monitors. However, if a beta particle detector
tion used in Eq 1 and 2 obviously depend on the material and
system is available, then S foils are suitable. Details of the
the equivalent energy chosen. For silicon, resonance effects use of sulfur foils are given in Test Method E 265.
cause large variations (by a factor of 20 or more) in the
8. Report
displacement damage function as a function of energy over the
8.1 In the report of the results of radiation-hardness tests in
...