ASTM F526-21

Standard Test Method for Using Calorimeters for Total Dose Measurements in Pulsed Linear Accelerator or Flash X-ray Machines

SIGNIFICANCE AND USE
5.1 An accurate measure of the total absorbed dose is necessary to ensure the validity of the data taken, to enable comparison to be made of data taken at different facilities, and to verify that components or circuits are tested to the radiation specification applied to the system for which they are to be used.  
5.2 The primary value of a calorimetric method for measuring dose is that the results are absolute. They are based only on physical properties of materials, that is, the specific heat of the calorimeter-block material and the Seebeck EMF of the thermocouple used or the temperature coefficient of resistance (α) of the thermistor used, all of which can be established with non-radiation measurements.  
5.3 The method permits repeated measurements to be made without requiring entry into the radiation cell between measurements.
SCOPE
1.1 This test method covers a calorimetric measurement of the total absorbed dose delivered by a single pulse of electrons from an electron linear accelerator or a flash X-ray machine (FXR, e-beam mode). The test method is designed for use with pulses of electrons in the energy range from 10 to 50 MeV and is only valid for cases in which both the calorimeter and the test specimen to be irradiated are “thin” compared to the range of these electrons in the materials of which they are constructed.  
1.2 The procedure described can be used in those cases in which (1) the dose delivered in a single pulse is 5 Gy(matl)2 [500 rd (matl)] or greater, or (2) multiple pulses of a lower dose can be delivered in a short time compared to the thermal time constant of the calorimeter. The units for the total absorbed dose delivered to a material require the specification of the material and the notation “matl” refers to the active material of the calorimeter. The minimum dose per pulse that can be acceptably monitored depends on the variables of the particular test, including pulse rate, pulse uniformity, and the thermal time constant of the calorimeter.  
1.3 A determination of the total dose is made directly for the material of which the calorimeter block is made. The total dose in other materials can be calculated from this measured value using Eq 3 presented in this test method. The need for such calculations and the choice of materials for which calculations are to be made shall be subject to agreement by the parties to the test.  
1.4 The values stated in SI units are to be regarded as the standard. The values in parenthesis are provided for information only.  
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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 31-May-2021
• 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

• Refers: ASTM E1894-18 - Standard Guide for Selecting Dosimetry Systems for Application in Pulsed X-Ray Sources
• Effective Date: 01-Dec-2018
• Refers: ASTM E170-17 - Standard Terminology Relating to Radiation Measurements and Dosimetry
• Effective Date: 01-Jun-2017
• Refers: ASTM E170-16a - Standard Terminology Relating to Radiation Measurements and Dosimetry
• Effective Date: 01-Oct-2016
• Refers: ASTM E170-16 - Standard Terminology Relating to Radiation Measurements and Dosimetry
• Effective Date: 15-Feb-2016
• Refers: ASTM E170-15a - Standard Terminology Relating to Radiation Measurements and Dosimetry
• Effective Date: 01-Sep-2015
• Refers: ASTM E170-15 - Standard Terminology Relating to Radiation Measurements and Dosimetry
• Effective Date: 15-Mar-2015
• Refers: ASTM E170-14a - Standard Terminology Relating to Radiation Measurements and Dosimetry
• Effective Date: 15-Oct-2014
• Refers: ASTM E170-14 - Standard Terminology Relating to Radiation Measurements and Dosimetry
• Effective Date: 01-Sep-2014
• Refers: ASTM E1894-13a - Standard Guide for Selecting Dosimetry Systems for Application in Pulsed X-Ray Sources
• Effective Date: 01-Aug-2013
• Refers: ASTM E1894-13 - Standard Guide for Selecting Dosimetry Systems for Application in Pulsed X-Ray Sources
• Effective Date: 01-Jun-2013
• Refers: ASTM E170-10 - Standard Terminology Relating to Radiation Measurements and Dosimetry
• Effective Date: 01-Jun-2010
• Refers: ASTM E170-09a - Standard Terminology Relating to Radiation Measurements and Dosimetry
• Effective Date: 15-Aug-2009
• Refers: ASTM E170-09 - Standard Terminology Relating to Radiation Measurements and Dosimetry
• Effective Date: 15-Jun-2009
• Refers: ASTM E170-08d - Standard Terminology Relating to Radiation Measurements and Dosimetry
• Effective Date: 01-Nov-2008
• Refers: ASTM E1894-08 - Standard Guide for Selecting Dosimetry Systems for Application in Pulsed X-Ray Sources
• Effective Date: 15-Sep-2008

Overview

ASTM F526-21 - "Standard Test Method for Using Calorimeters for Total Dose Measurements in Pulsed Linear Accelerator or Flash X-ray Machines" - is a critical international standard from ASTM International. This document outlines a standardized calorimetric method to measure the total absorbed dose delivered by single or multiple pulses of electrons from an electron linear accelerator (linac) or a flash X-ray machine (FXR) used in radiation-effects testing. This standard is particularly relevant for electron pulse energies in the range of 10 to 50 MeV, with applications where both the calorimeter and the test specimen are "thin" relative to the electron range in the respective materials.

Accurate measurement of absorbed dose is essential for verifying compliance with radiation specifications, comparing data across different facilities, and ensuring integrity in radiation-testing of electronic components and systems.

Key Topics

• Calorimetric Dose Measurement: Employs calorimeters constructed from various materials, where the absorbed dose is determined by measuring the temperature rise due to radiation pulses.
• Single and Multiple Pulse Methods: Procedures for both single, high-dose pulses and multiple-pulse series for scenarios where a single pulse does not provide sufficient signal.
• Material Considerations: Direct measurement is made in the calorimeter-block material. Conversion equations are provided to estimate doses in other materials based on physical properties.
• Thermal and Measurement Precautions: Emphasizes proper thermal isolation, bonding techniques for thermocouples or thermistors, and minimizing heat loss to maximize accuracy.
• Instrument Calibration: Specifications for amplifiers, data recorders, and voltage calibration sources to ensure precision.
• Practical Usage: Enables repeatable measurements without repeated access to the radiation cell, improving operational efficiency.
• Uncertainty and Error Management: Addresses expected measurement bias and sources of error, supporting reliable dosimetry analysis.

Applications

• Radiation Hardness Testing: Ensures that components, circuits, and materials used in space, military, or high-reliability electronics endure specified radiation doses.
• Inter-Laboratory Comparisons: Facilitates standardized measurement practices across test laboratories, supporting benchmark testing, and quality control.
• Flash X-ray and Pulsed Electron Facilities: Used within facilities employing pulsed, high-energy radiation sources for testing and research.
• Material Dosimetry: Serves sectors requiring precise dose measurements in specific materials, such as silicon or copper, using conversion methods provided in the standard.
• Automated Test Systems: The method’s ability to facilitate repeated measurements remotely, without entering hazardous radiation environments, supports safe and streamlined operations.

Related Standards

• ASTM E170: Terminology Relating to Radiation Measurements and Dosimetry - Defines key terms used in F526.
• ASTM E230: Specification for Temperature-Electromotive Force (emf) Tables for Standardized Thermocouples - Provides thermocouple reference data essential for calorimeter design.
• ASTM E1894: Guide for Selecting Dosimetry Systems for Application in Pulsed X-Ray Sources - Offers guidance on suitable dosimetry systems for pulsed radiation sources.

Practical Value

By implementing the calorimetric test method described in ASTM F526-21, laboratories and facilities benefit from:

• Absolute Dose Measurement: Results are based solely on physical properties of materials, not requiring calibration in a radiation field.
• Enhanced Accuracy and Traceability: Direct, repeatable readings enhance data quality for regulatory compliance and certification.
• Operational Efficiency: Minimizes the need for exposure to radiation environments, supporting worker safety and cost-effective testing.
• Standardized Reporting: Facilitates clear documentation and traceability, supporting international acceptance of test results.

Keywords: ASTM F526-21, calorimetric measurements, total absorbed dose, pulsed linear accelerator, flash X-ray machine, radiation effects testing, dose measurement, electron irradiation, dosimetry, materials testing, electron beam, radiation laboratory standards.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: F526 − 21
Standard Test Method for
Using Calorimeters for Total Dose Measurements in Pulsed
Linear Accelerator or Flash X-ray Machines
ThisstandardisissuedunderthefixeddesignationF526;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginal
adoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscript
epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
1.1 This test method covers a calorimetric measurement of
mine the applicability of regulatory limitations prior to use.
the total absorbed dose delivered by a single pulse of electrons
1.6 This international standard was developed in accor-
from an electron linear accelerator or a flash X-ray machine
dance with internationally recognized principles on standard-
(FXR,e-beammode).Thetestmethodisdesignedforusewith
ization established in the Decision on Principles for the
pulses of electrons in the energy range from 10 to 50 MeVand
Development of International Standards, Guides and Recom-
isonlyvalidforcasesinwhichboththecalorimeterandthetest
mendations issued by the World Trade Organization Technical
specimen to be irradiated are “thin” compared to the range of
Barriers to Trade (TBT) Committee.
these electrons in the materials of which they are constructed.
1.2 The procedure described can be used in those cases in
2. Referenced Documents
which (1) the dose delivered in a single pulse is 5 Gy(matl)
2.1 ASTM Standards:
[500rd(matl)]orgreater,or(2)multiplepulsesofalowerdose
E170Terminology Relating to Radiation Measurements and
can be delivered in a short time compared to the thermal time
Dosimetry
constant of the calorimeter. The units for the total absorbed
E230Specification for Temperature-Electromotive Force
dose delivered to a material require the specification of the
(emf) Tables for Standardized Thermocouples
materialandthenotation“matl”referstotheactivematerialof
E1894Guide for Selecting Dosimetry Systems for Applica-
the calorimeter. The minimum dose per pulse that can be
tion in Pulsed X-Ray Sources
acceptablymonitoreddependsonthevariablesoftheparticular
test, including pulse rate, pulse uniformity, and the thermal
3. Terminology
time constant of the calorimeter.
3.1 Definitions:
1.3 Adeterminationofthetotaldoseismadedirectlyforthe
3.1.1 device under test (DUT)—the device that is being
materialofwhichthecalorimeterblockismade.Thetotaldose
tested.
in other materials can be calculated from this measured value
3.1.2 Seebeck EMF—the electromagnetic force (EMF) gen-
using Eq 3 presented in this test method. The need for such
erated by the Seebeck effect when two wires composed of
calculations and the choice of materials for which calculations
dissimilar metals are joined at both ends and the ends are held
are to be made shall be subject to agreement by the parties to
atdifferenttemperatures.Avoltagecanbemeasuredacrossthe
the test.
terminals when current flows through the wires.
1.4 The values stated in SI units are to be regarded as the
3.1.3 temperature coeffıcient of resistance—the resistance
standard. The values in parenthesis are provided for informa-
change in a material per degree of temperature change dΩ/
tion only.
(Ω*dθ), where Ω denotes the resistance and θ denotes the
1.5 This standard does not purport to address all of the
temperature. This quantity has units of inverse temperature
safety concerns, if any, associated with its use. It is the
and, for small changes about a reference temperature in a
conductor, this quantity is often modeled as a linear relation-
ThistestmethodisunderthejurisdictionofASTMCommitteeE10onNuclear ship with temperature.
Technology and Applications and is the direct responsibility of Subcommittee
E10.07 on Radiation Dosimetry for Radiation Effects on Materials and Devices.
Current edition approved June 1, 2021. Published July 2021. Originally
published as F526–77 T. Last previous edition approved in 2016 as F526–16. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
DOI: 10.1520/F0526-21. contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
In1975theGeneralConferenceonWeightsandMeasuresadoptedtheunitgray Standards volume information, refer to the standard’s Document Summary page on
(symbol – Gy) for absorbed dose; 1 Gy=100 rd. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F526 − 21
3.1.4 thermal time constant of a calorimeter—the time for 6.2 Thermal Equilibrium—The initial value of the transient
the temperature excursion of the calorimeter material resulting temperature change following a radiation pulse may not reflect
from a radiation pulse to drop to 1/e of its initial maximum the true temperature change of the calorimeter-block material.
value.
NOTE 2—This situation can be brought about by a temperature rise
3.1.5 TSP—twisted shielded pair, a shielded case of a occurring in the materials at the point of attachment of the thermocouple
or the thermistor different from that in the calorimeter-block material.As
twistedpaircableinwhichtwoconductorsaretwistedtogether
long as the calorimeter block comprises the great bulk of the calorimeter
for the purpose of canceling out electromagnetic interference
material, the temperature will quickly equilibrate to that of the block, and
from external sources.
the subsequent temperature record will be that of the calorimeter-block
material (see Appendix X1).
3.2 Definitions of other terms used in this standard that
pertaintoradiationmeasurementsanddosimetrymaybefound 6.3 Pulse Reproducibility—If pulse-to-pulse reproducibility
in Terminology E170.
of the radiation source varies more than 620%, a good
measure of the dose per pulse may not be attainable from the
4. Summary of Test Method
average value calculated in the multiple-pulse method.
4.1 Single-Pulse Method—This method consists of (1)
6.4 Facility Spot Size—If the calorimeter is used in high-
irradiating, with a single pulse of high-energy electrons from doseratepositions,thespotsize(especiallyinebeamfacilities)
an electron linear accelerator (linac) or flash X-ray machine
may not be large enough to adequately cover the calorimeter
(FXR),asmallblockofmaterialtowhicheitherathermistoror
material.
athermocouplemadefromsmall-diameterwireisattached;(2)
7. Apparatus
recording and measuring the resulting signal from a bridge
circuit or directly from the thermocouple; (3) calculating the
7.1 Pulsed Electron Source:
total dose deposited in the block based on the temperature rise
7.1.1 Linac—Electron linear accelerator and associated in-
and the specific heat of the material; and (4) if required,
strumentation and controls suitable for use as an ionizing
calculating the equivalent dose in other specified materials
source for radiation-effects testing. See Guide E1894.
exposed to this same pulse.
7.1.2 FXR—Flash X-ray system that provides intense
bremsstrahlung X-ray radiation environments, usually in a
4.2 Multiple-Pulse Method—Ifthedoseavailableinasingle
single sub-microsecond pulse, and which can often fluctuate in
pulse is not large enough to give measurable results, the linac
amplitude, shape, and spectrum from shot to shot.This system
is pulsed repeatedly within a time short compared to the
can be operated in an electron beam mode by not utilizing the
thermaltimeconstantofthecalorimeter.Thismethodissimilar
bremsstrahlung converter. See Guide E1894.
to the single-pulse method except that the average dose
delivered in each pulse is calculated from the measured
7.2 Calorimeter—Special instrument suitable for measuring
cumulative dose of all the pulses.
the total dose delivered by the linac and constructed in
accordance with any of several designs indicated in Appendix
5. Significance and Use
X1.Aselectionofcalorimetermaterialsandtheirpropertiesare
shown in Table 1.Although measurement differences resulting
5.1 An accurate measure of the total absorbed dose is
from the use of different designs should not be significant, all
necessary to ensure the validity of the data taken, to enable
partiestothetestshallagreetoasingledesignutilizingasingle
comparison to be made of data taken at different facilities, and
calorimeter-block material and a specific thermocouple or
to verify that components or circuits are tested to the radiation
thermistor (see Fig. 1). The calorimeter design shall be such
specification applied to the system for which they are to be
that the material surrounding the active calorimeter material
used.
that is penetrated along the beam path is less than or equal to
5.2 The primary value of a calorimetric method for measur-
no more than 20% of the range of the beam-energy electrons.
ingdoseisthattheresultsareabsolute.Theyarebasedonlyon
physical properties of materials, that is, the specific heat of the
TABLE 1 Physical Properties of Some Calorimeter-Block
calorimeter-block material and the Seebeck EMF of the ther-
Materials
mocouple used or the temperature coefficient of resistance (α)
A B B 3
Energy Loss dE/dx Specific Heat, c Density, ρ (10
p
Material
−14 2 3
of the thermistor used, all of which can be established with
(10 J·m /kg) (J/kg·K) kg/m )
non-radiation measurements.
C 2.92 711 2.10
Al 2.74 900 2.70
5.3 The method permits repeated measurements to be made
Si 2.84 711 2.33
without requiring entry into the radiation cell between mea- Fe 2.52 452 7.87
Cu 2.42 385 8.96
surements.
Ge 2.45 322 5.32
W 2.08 134 19.3
6. Interferences Au 2.06 130 19.3
Pb 2.07 128 11.4
6.1 Thermal Isolation—If the thermal isolation of the calo-
A
The data are given for 20-MeV electrons, but ratios based on these values are
rimeter is not sufficient, the thermal time constant of the
good to better than 2 % over the energy range from 10 to 50 MeV, inclusive. These
calorimeter response will be too short for it to be useful.
values have been converted to SI units from data given in Refs (1) and (2).
B
These values have been converted to SI units from data given in the Ref (3).
NOTE 1—This condition can be caused by insufficient insulation
(The specific heat values are applicable in the range from 18 to 30°C, inclusive.)
material or by heat loss through the thermocouple wires themselves.
F526 − 21
FIG. 1 Typical Block Diagram of Calorimeter Dosimeter Circuit
7.3 D-C Low Noise Amplifier (LNA), with a gain of 1000 to 7.5 Voltage Calibration Source—Voltage source capable of
10 000 (see Fig. 2). meeting the following specifications:
7.5.1 Output voltages including 1.5, 3.0, 5.0, 10.0, 15, 30,
NOTE 3—An analog nanovoltmeter with a recorder output can also be
50, and 100 µV,
used as a low noise amplifier. These devices produce a 1–V output for a
full scale reading.
7.5.2 Accuracy of 61% of the selected voltage, or better,
7.3.1 Response time less than 0.1 s for the amplifier output 7.5.3 Thermallygeneratedvoltagesoflessthan100nVwith
to reach 90% of its final reading,
the source stabilized, and
7.3.2 Noiselevellessthan10mVrmsreferredtotheoutput,
7.5.4 Source resistance of 100 Ω or less.
7.3.3 Measurement accuracy of 2% of full scale or better,
7.6 Wheatstone Bridge Circuit, designed so that the therm-
7.3.4 Normal-mode rejection capability such that AC volt-
istor forms one leg of the bridge, and so that the adjustable
ages of 50 Hz and above and 60 dB greater than the range
resistor of the bridge will be equal to the resistance of the
setting shall not affect the instrument reading by greater than
thermistor at balance (see Fig. 1B).
2%.
7.7 Flash X-ray Machine (E-beam Mode)—An FXR oper-
NOTE 4—If the meter does not have an internal nulling circuit, it may
ated in the e-beam mode generally provides a higher dose rate
be necessary to use a simple bucking circuit to null out thermal EMFs in
the measuring circuit to keep the meter on scale at the high-gain positions
than similar machines operated in photon, for example,
used in this measurement (see Fig. 1).
bremsstrahlung, mode. However, testing in the e-beam mode
7.4 Data Recorder—Linear-response recorder or digital os- requires that appropriate precautions be taken and special test
cilloscope meeting the following specifications: fixtures be used to ensure meaningful results. The beam
7.4.1 Recording duration sufficient to capture 5 to 10 s of produces a large magnetic field, which may interfere with the
calorimeter response. instrumentation, and can induce large circulating currents in
7.4.2 Therecordingfrequencyshallbechosentosufficiently deviceleadsandmetals.Thebeamalsoproducesairionization,
capture the measurement signal. inducedchargeonopenleads,andunwantedcablecurrentsand
F526 − 21
FIG. 2 Recommended Low Noise Amplifier Schematic Diagram
voltages. E-beam testing is generally performed with the 9. Calibration
device-under-test (DUT) mounted in a vacuum to reduce air
9.1 The LNAand recorder should be calibrated to be within
ionization effects. Some necessary precautions are:
62 % of full scale.
7.7.1 The electron beam must be constrained to the region
that is to be irradiated. Support circuits and components must 10. Procedure
be properly shielded.
10.1 Single-Pulse Method:
7.7.2 The total electron beam current shall be absorbed
10.1.1 Position the calorimeter at the location where the
within the test chamber and returned to the FXR to prevent
dose measurement is desired.
unwanted currents in cables and secondary radiation in the
10.1.2 Connect all components of the calorimetric dosim-
exposure room.
eter system in accordance with the circuit shown in Fig. 1.
7.7.3 All cables and wires must be shielded from exposure
10.1.3 Set the LNA for a gain of 10 000 (or 1000, if using
to prevent unwanted signal noise. Noise may be caused by
the thermistor circuit).
direct deposition of the beam in cables, or by magnetic
NOTE 5—ALNAis not always needed if the calorimeter is used at high
coupling of the beams into the cable.
dose positions. The signal for some calorimeter materials can be quite
7.7.4 An evacuated chamber for the test is required to
large.
reduce the effects of air ionization.
10.1.4 For the thermocouple measurements, adjust either
the internal nulling circuit of the LNAor the external bucking
8. Sampling
circuit so that the meter deflection caused by the quiescent
8.1 The number of measurements shall be subject to agree- level of the calorimeter output is less than full scale. For
ment by the parties to the test. Care should be taken to select thermistor measurements adjust the bridge for a null. Use the
a sample size that will produce an acceptable uncertainty. zero-adjust capability of the data recorder to position the
F526 − 21
all shots. This protocol should be done two or three times during a shot
recorder trace near the center of the recorder chart. If using an
day. If you want best accuracy, wait for the calorimeter to cool down
oscilloscope, adjust the settings accordingly to make sure that
between pulses and allow the calorimeter signal to use at least half the
the response is fully captured within the oscilloscope window.
range.
Refer to the oscilloscope manual to ensure that the proper
10.1.7 Repeat 10.1.5 and 10.1.6 until a range is found for
resolution is set to capture the response signal.
which the greater-than-10% criterion is met, or until there are
NOTE 6—With either system, there will likely be a drift as the
no more ranges to try.
temperature of the calorimeter equilibrates. This drift is compensated for
in data reduction and may be neglected if the rate of change is much less 10.1.7.1 When a range is found for which this greater-than-
than that caused by the radiation pulse.
10% criterion is met, note the data recorder setting beside the
recorded transient with the shot number, date, LNA gain,
10.1.5 If using a data recorder sweep speed set within the
range from 0.5 to 2.0 cm/s, inclusive, trigger the recorder and calorimeter identification, and description of irradiation geom-
etry (including scatterer thickness and distance of the calorim-
pulse the source.
10.1.6 If the transient deflection of the recorder is less than eter from the scatterer) as shown in Fig. 3 and Fig. 4.
10% of full scale, set the recorder range to the next lower
10.1.7.2 If no range if found for which a 10% deflection is
range and repeat 10.1.5.
obtained which is easily distinguishable from noise, use the
multiple-pulse method beginning with 10.2.2.
NOTE 7—Care should be taken if multiple pulses are going to be
administered, because of the temperature that the pulses generate, which
10.1.7.3 Otherwise, repeat 10.1.7.1 four more times.
will cause the calorimeter to rise. The protocol for establishing the
10.1.7.4 If using an oscilloscope, set the necessary param-
temperatureinamultipleirradiationshallbeestablishedbeforethetesting
eters to capture the response. Refer to the oscilloscope refer-
isinitiated,forexample,itshouldbestatedupfrontifyouaregoingtouse
the average from a specified number of pulses as being representative of ence manual to set the parameters.
FIG. 3 Typical Chart Record of Calorimeter Dosimetry Using Single-Pulse Method
F526 − 21
FIG. 4 Typical Digital Oscilloscope Recording of the Calorimeter Response
10.2 Multiple-Pulse Method: 11.1.2 Determine whether a period of time was required for
10.2.1 Carry out 10.1.1 through 10.1.4. the temperature to equilibrate after the pulse, as indicated by
10.2.2 If using the recorder chart speed set within the range thepresenceofaspike(Fig.5a)oraflatportion(Fig.5b)ofthe
from 0.5 to 2.0 cm/s, inclusive, pulse the linac repeatedly data recorder trace at the end of the transient.
within a time that is short compared to the thermal time 11.1.2.1 If no such feature is present, draw a line extrapo-
constantofthecalorimetertogivearecorderdeflectiongreater lating the steepest part of the cooling curve following each
than 10% of full scale. radiation pulse back to intersect the perpendicular line (see
10.2.2.1 From the data, measure the voltage rise resulting 11.1.1). When using digital storage oscilloscopes, built in
from this series of pulses. cursors usually can be used.
10.2.2.2 For the time interval beginning with the cessation
NOTE 8—These lines are dashed in Fig. 3.
of the radiation and equal in duration to the total time during
11.1.2.2 If such a feature is present, draw a line extrapolat-
which the radiation dose was accumulated, measure the ther-
ing from the slope of the curve where a smooth cooling trend
mocouple voltage drop.
resumes. Do this for each pulse.
10.2.2.3 Calculate the ratio of the voltage from 10.2.2.2 to
that of 10.2.2.1.
NOTE 9—These lines are dashed in Fig. 5.
10.2.2.4 If this ratio is less than 0.15, continue with 10.2.3
11.1.3 Measure along each perpendicular line the length
(the thermal time constant of the calorimeter is sufficiently
from the start of each transient to the intersection of the
greater than the radiation time for the dose to be determined
perpendicular line with the extrapolated line.
accurately).
11.1.4 Convert these measurements to output voltage level.
10.2.2.5 If this ratio is equal to or greater than 0.15, repeat
11.1.5 For each pulse calculate and record the dose in Gy
10.2.2 through 10.2.2.5 using a higher pulse repetition rate for
(calorimeter-block material) producing the transient, using for
a shorter radiation time period.
a thermocouple measurement, the relation:
10.2.3 Annotate the data recorder output, as well as the
Dose 5 100 Vc /PG (1)
number of pulses used (see Fig. 5, Fig. 6, and Fig. 7). p
10.2.4 Repeat 10.2.2 and 10.2.3 four more times, omitting
where:
the time constant determination (10.2.2.1 through 10.2.2.5).
V = deflection caused by irradiation pulse, in microvolts,
10.2.5 If using the oscilloscope, refer to the reference
c = specific heat capacity of calorimeter-block material,
p
manual to set the oscilloscope, pulse the linac repeatedly
J/kg·K,
within a time that is short compared to the thermal time
P = temperature coefficient of the calorimeter thermo-
constant of the calorimeter to ensure that the response is
couple in the vicinity of room temperature, µV/K,
properly captured on the oscilloscope.
G = gain of low noise amplifier, and,
100 = numerical conversion factor, rad·kg/J.
11. Calculation and Interpretation of Results
NOTE 10—Calibration curves for converting thermocouple voltage
measurements to temperature measurements are available for some
11.1 Single-Pulse Method:
thermocouples. If available, these can be used to supplement Eq 1.
11.1.1 On the recorder output, determine the perpendicular
to the time axis at the start of each transient, as shown in Fig. 11.1.6 For a thermistor measurement, use the equation
3. (Appendix X2):
F526 − 21
11.2 Multiple-Pulse Method:
11.2.1 Drawalineperpendiculartothetimeaxisatthetime
midway between the start and end of the sets of multiple
radiation pulses, as shown in Fig. 6.
11.2.2 For each multiple-pulse transient, draw a linear
extrapolation of the cooling curve immediately preceding the
radiation, and extend it to intercept the perpendicular line (see
11.2.1).
NOTE 12—These lines are dashed in Fig. 6.
11.2.3 Foreachtransient,drawalineextrapolatingbackthe
cooling curve, following the transient, to intercept the perpen-
dicular line drawn for that transient.
NOTE 13—These lines are also dashed in Fig. 6.
11.2.4 For each transient, measure the length along the
perpendicular line between the intersections with the extended
and extrapolated lines.
11.2.5 Convertthesemeasurementstofractionsoffull-scale
width.
(a) Spike Indicating Initial Thermocouple Junction Temperature Higher than that
of the Calorimeter Block.
11.2.6 Calculate and record the dose delivered in each burst
of multiple pulses in accordance with 11.1.5.
11.2.7 Divide the dose calculated for each set of pulses by
the number of pulses in the set to obtain the average dose per
pulse for that set. Record these figures.
11.2.8 Average the five values obtained. Record this figure.
NOTE14—Thisfigureprovidesthebestestimateoftheaveragedoseper
pulse. However, this average value is seldom useful if the pulse-to-pulse
reproducibility is not within 620% of a median value.
11.3 Dose Conversion:
11.3.1 To convert the dose measured in 11.1
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: F526 − 16 F526 − 21
Standard Test Method for
Using Calorimeters for Total Dose Measurements in Pulsed
Linear Accelerator or Flash X-ray Machines
This standard is issued under the fixed designation F526; 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 (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope
1.1 This test method covers a calorimetric measurement of the total absorbed dose delivered inby a single pulse of electrons from
an electron linear accelerator or a flash X-ray machine (FXR, e-beam mode) used as an ionizing source in radiation-effects testing.
mode). The test method is designed for use with pulses of electrons in the energy range from 10 to 50 MeV and is only valid for
cases in which both the calorimeter and the test specimen to be irradiated are “thin” compared to the range of these electrons in
the materials of which they are constructed.
1.2 The procedure described can be used in those cases in which (1) the dose delivered in a single pulse is 5 Gy(matl) [500 rd
(matl)] or greater, or (2) multiple pulses of a lower dose can be delivered in a short time compared to the thermal time constant
of the calorimeter. The units for the total absorbed dose delivered to a material require the specification of the material and the
notation “matl” refers to the active material of the calorimeter. The minimum dose per pulse that can be acceptably monitored
depends on the variables of the particular test, including pulse rate, pulse uniformity, and the thermal time constant of the
calorimeter.
1.3 A determination of the total dose is made directly for the material of which the calorimeter block is made. The total dose in
other materials can be calculated from this measured value by formulasusing Eq 3 presented in this test method. The need for such
calculations and the choice of materials for which calculations are to be made shall be subject to agreement by the parties to the
test.
1.4 The values stated in SI units are to be regarded as the standard. The values in parenthesis are provided for information only.
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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
This test method is under the jurisdiction of ASTM Committee E10 on Nuclear Technology and Applications and is the direct responsibility of Subcommittee E10.07
on Radiation Dosimetry for Radiation Effects on Materials and Devices.
Current edition approved June 1, 2016June 1, 2021. Published July 2016July 2021. Originally published as F526 – 77 T. Last previous edition approved in 20112016 as
F526 – 11.F526 – 16. DOI: 10.1520/F0526-16.10.1520/F0526-21.
In 1975 the General Conference on Weights and Measures adopted the unit gray (symbol–Gy) (symbol – Gy) for absorbed dose; 1 Gy = 100 rad.rd.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F526 − 21
2. Referenced Documents
2.1 ASTM Standards:
E170 Terminology Relating to Radiation Measurements and Dosimetry
E230 Specification for Temperature-Electromotive Force (emf) Tables for Standardized Thermocouples
E1894 Guide for Selecting Dosimetry Systems for Application in Pulsed X-Ray Sources
3. Terminology
3.1 Definitions:
3.1.1 device under test (DUT)—the device that is under the current test.being tested.
3.1.2 Seebeck EMF—the electromagnetic force (EMF) generated by the Seebeck effect when two wires composed of dissimilar
metals are joined at both ends and the ends are held at different temperatures. A voltage can be measured across the terminals when
current flows through the wires.
3.1.3 temperature coeffıcient of resistance—the resistance change in a material per degree of temperature change dΩ/(Ω*dθ),
where Ω denotes the resistance and θ denotes the temperature. This quantity has units of inverse temperature and, for small changes
about a reference temperature in a conductor, this quantity is often modeled as a linear relationship with temperature.
3.1.4 thermal time constant of a calorimeter—the time for the temperature excursion of the calorimeter material resulting from
a radiation pulse to drop to 1/e of its initial maximum value.
3.1.5 TSP—twisted shielded pair, a shielded case of a twisted pair cable in which two conductors are twisted together for the
purpose of canceling out electromagnetic interference from external sources.
3.2 Definitions of other terms used in this standard that pertain to radiation measurements and dosimetry may be found in
Terminology E170.
4. Summary of Test Method
4.1 Single-Pulse Method—This method consists of (1) irradiating, with a single pulse of high-energy electrons from an electron
linear accelerator (linac) or flash X-ray machine (FXR), a small block of material to which either a thermistor or a thermocouple
made from small-diameter wire is attached; (2) recording and measuring the resulting signal from a bridge circuit or directly from
the thermocouple; (3) calculating the total dose deposited in the block based on the temperature rise and the specific heat of the
material; and (4) if required, calculating the equivalent dose in other specified materials exposed to this same pulse.
4.2 Multiple-Pulse Method—If the dose available in a single pulse is not large enough to give measurable results, the linac is
pulsed repeatedly within a time short compared to the thermal time constant of the calorimeter. This method is similar to the
single-pulse method except that the average dose delivered in each pulse is calculated from the measured cumulative dose of all
the pulses.
5. Significance and Use
5.1 An accurate measure of the total absorbed dose is necessary to ensure the validity of the data taken, to enable comparison to
be made of data taken at different facilities, and to verify that components or circuits are tested to the radiation specification applied
to the system for which they are to be used.
5.2 The primary value of a calorimetric method for measuring dose is that the results are absolute. They are based only on physical
properties of materials, that is, the specific heat of the calorimeter-block material and the Seebeck EMF of the thermocouple used
or the temperature coefficient of resistance (α) of the thermistor used, all of which can be established with non-radiation
measurements.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
F526 − 21
5.3 The method permits repeated measurements to be made without requiring entry into the radiation cell between measurements.
6. Interferences
6.1 Thermal Isolation—If the thermal isolation of the calorimeter is not sufficient, the thermal time constant of the calorimeter
response will be too short for it to be useful.
NOTE 1—This condition can be caused by insufficient insulation material or by heat loss through the thermocouple wires themselves.
6.2 Thermal Equilibrium—The initial value of the transient temperature change following a radiation pulse may not reflect the true
temperature change of the calorimeter-block material.
NOTE 2—This situation can be brought about by a temperature rise occurring in the materials at the point of attachment of the thermocouple or the
thermistor different from that in the calorimeter-block material. As long as the calorimeter block comprises the great bulk of the calorimeter material, the
temperature will quickly equilibrate to that of the block, and the subsequent temperature record will be that of the calorimeter-block material (see
Appendix X1).
6.3 Pulse Reproducibility—If pulse-to-pulse reproducibility of the radiation source varies more than 620 %, a good measure of
the dose per pulse may not be attainable from the average value calculated in the multiple-pulse method.
6.4 Facility Spot Size—If the calorimeter is used in high-dose rate positions, the spot size (especially in ebeam facilities) may not
be large enough to adequately cover the calorimeter material.
7. Apparatus
7.1 Pulsed Electron Source:
7.1.1 Linac—Electron linear accelerator and associated instrumentation and controls suitable for use as an ionizing source infor
radiation-effects testing. See Guide E1894.
7.1.2 FXR—Flash X-ray system that provides intense bremsstrahlung X-ray radiation environments, usually in a single
sub-microsecond pulse, and which can often fluctuate in amplitude, shape, and spectrum from shot to shot. This system can be
operated in an electron beam mode by not utilizing the bremsstrahlung converter. See Guide E1894.
7.2 Calorimeter—Special instrument suitable for measuring the total dose delivered by the linac and constructed in accordance
with any of several designs utilizing anyindicated in Appendix X1of several materials as indicated in. A selection of calorimeter
materials Appendix X1. and their properties are shown in Table 1. Although measurement differences resulting from the use of
different designs should not be significant, all parties to the test shall agree to a single design utilizing a single calorimeter-block
material and a specific thermocouple or thermistor. thermistor (see Fig. 1). The calorimeter design shall be such that the surface
TABLE 1 Physical Properties of Some Calorimeter-Block
Materials
A B B 3
Energy Loss dE/dx Specific Heat, c Density, ρ (10
p
Material −14 2 3
(10 J·m /kg) (J/kg·K) kg/m )
C 2.92 711 2.10
Al 2.74 900 2.70
Si 2.84 711 2.33
Fe 2.52 452 7.87
Cu 2.42 385 8.96
Ge 2.45 322 5.32
W 2.08 134 19.3
Au 2.06 130 19.3
Pb 2.07 128 11.4
A
The data are given for 20-MeV electrons, but ratios based on these values are
good to better than 2 % over the energy range from 10 to 50 MeV, inclusive. These
values have been converted to SI units from data given in Refs (31) and (52).
B
These values have been converted to SI units from data given in the Ref (63).
(The specific heat values are applicable in the range from 18 to 30°C, inclusive.)
F526 − 21
density in the material surrounding the active calorimeter material that is penetrated along the beam path is less than or equal to
no more than 20 % of the range of the beam-energy electrons (see electrons.Fig. 1).
7.3 D-C Low Noise Amplifier (LNA), with a gain of 1000 to 10 000 (see Fig. 2).
NOTE 3—An analog nanovoltmeter with a recorder output can also be used as a low noise amplifier. These devices produce a 1–V output for a full scale
reading.
7.3.1 Response time less than 0.1 s for the amplifier output to reach 90 % of its final reading,
7.3.2 Noise level less than 10 mV rms referred to the output,
7.3.3 Measurement accuracy of 2 % of full scale or better,
7.3.4 Normal-mode rejection capability such that AC voltages of 50 Hz and above and 60 dB greater than the range setting shall
not affect the instrument reading by lessgreater than 2 %.
NOTE 4—If the meter does not have an internal nulling circuit, it may be necessary to use a simple bucking circuit to null out thermal EMFs in the
measuring circuit to keep the meter on scale at the high-gain positions used in this measurement (see Fig. 1).
7.4 Data Recorder—Linear-response recorder or digital oscilloscope meeting the following specifications:
7.4.1 Recording duration sufficient to capture 5 to 10 s of calorimeter response.
7.4.2 The recording frequency shall be chosen to sufficiently capture the measurement signal.
FIG. 1 Typical Block Diagram of Calorimeter Dosimeter Circuit
F526 − 21
FIG. 2 Recommended Low Noise Amplifier Schematic Diagram
7.5 Voltage Calibration Source—Voltage source capable of meeting the following specifications:
7.5.1 Output voltages including 1.5, 3.0, 5.0, 10.0, 15, 30, 50, and 100 μV,
7.5.2 Accuracy of 61 % of the selected voltage, or better,
7.5.3 Thermally generated voltages of less than 100 nV with the source stabilized, and
7.5.4 Source resistance of 100 Ω or less.
7.6 Wheatstone Bridge Circuit, designed so that the thermistor forms one leg of the bridge, and so that the adjustable resistor of
the bridge will be equal to the resistance of the thermistor at balance (see Fig. 1B).
7.7 Flash X-ray Machine (E-beam Mode)—An FXR operated in the e-beam mode generally provides a higher dose rate than
similar machines operated in photon, for example, bremsstrahlung, mode. However, testing in the e-beam mode requires that
appropriate precautions be taken and special test fixtures be used to ensure meaningful results. The beam produces a large magnetic
field, which may interfere with the instrumentation, and can induce large circulating currents in device leads and metals. The beam
also produces air ionization, induced charge on open leads, and unwanted cable currents and voltages. E-beam testing is generally
performed with the device-under-test (DUT) mounted in a vacuum to reduce air ionization effects. Some necessary precautions are:
7.7.1 The electron beam must be constrained to the region that is to be irradiated. Support circuits and components must be
properly shielded.
F526 − 21
7.7.2 The total electron beam must current shall be stoppedabsorbed within the test chamber and returned to the FXR to prevent
unwanted currents in cables and secondary radiation in the exposure room.
7.7.3 All cables and wires must be protectedshielded from exposure to prevent extraneous currents. These currentsunwanted signal
noise. Noise may be caused by direct deposition of the beam in cables, or by magnetic coupling of the beams into the cable.
7.7.4 An evacuated chamber for the test is required to reduce the effects of air ionization.
8. Sampling
8.1 The number of measurements shall be subject to agreement by the parties to the test. Care should be taken to select a sample
size that will produce an acceptable uncertainty.
9. Calibration
9.1 The LNA and recorder should be calibrated to be within 62 % of full scale.
10. Procedure
10.1 Single-Pulse Method:
10.1.1 Position the calorimeter at the location where the dose measurement is desired.
10.1.2 Connect all components of the calorimetric dosimeter system in accordance with the circuit shown in Fig. 1.
10.1.3 Set the LNA for a gain of 10 000 (or 1000, if using the thermistor circuit).
NOTE 5—A LNA is not always needed if the calorimeter is used at high dose positions. The signal for some calorimeter materials can be quite large.
10.1.4 For the thermocouple measurements, adjust either the internal nulling circuit of the LNA or the external bucking circuit so
that the meter deflection caused by the quiescent level of the calorimeter output is less than full scale. For thermistor measurements
adjust the bridge for a null. Use the zero-adjust capability of the data recorder to position the recorder trace near the center of the
recorder chart. If using an oscilloscope, adjust the settings accordingly to make sure that the response if noticeable is fully captured
within the oscilloscope window. Refer to the oscilloscope manual to ensure that the proper resolution areis set to capture the
response signal.
NOTE 6—With either system, there will likely be a drift as the temperature of the calorimeter equilibrates. This drift is compensated for in data reduction
and may be neglected if the rate of change is much less than that caused by the radiation pulse.
10.1.5 If using a data recorder sweep speed set within the range from 0.5 to 2.0 cm/s, inclusive, trigger the recorder and pulse the
source.
10.1.6 If the transient deflection of the recorder is less than 10 % of full scale, set the recorder range to the next lower range and
repeat 10.1.5.
NOTE 7—Care should be taken if multiple pulses are going to be administered, because of the temperature that the pulses generate, which will cause the
calorimeter to rise. The protocol for establishing the temperature in a multiple irradiation shall be established before the testing is initiated, for example,
it should be stated up front if you are going to use the average from a specified number of pulses as being representative of all shots. This protocol should
be done two or three times during a shot day. If you want best accuracy, wait for the calorimeter to cool down between pulses and allow the calorimeter
signal to use at least half the range.
10.1.7 Repeat 10.1.5 and 10.1.6 until a range is found for which the greater-than-10 % criterion is met, or until there are no more
ranges to try.
10.1.7.1 When a range is found for which this greater-than-10 % criterion is met, note the data recorder setting beside the recorded
transient with the shot number, date, LNA gain, calorimeter identification, and description of irradiation geometry (including
scatterer thickness and distance of the calorimeter from the scatterer) as shown in Fig. 3 and Fig. 4.
F526 − 21
FIG. 3 Typical Chart Record of Calorimeter Dosimetry Using Single-Pulse Method
FIG. 4 Typical Digital Oscilloscope Recording of the Calorimeter Response
F526 − 21
10.1.7.2 If no range if found for which a 10 % deflection is obtained which is easily distinguishable from noise, use the
multiple-pulse method beginning with 10.2.2.
10.1.7.3 Otherwise, repeat 10.1.7.1 four more times.
10.1.7.4 If using an oscilloscope, set the necessary parameters to capture the response. Refer to the oscilloscope reference manual
to set the parameters.
10.2 Multiple-Pulse Method:
10.2.1 Carry out 10.1.1 through 10.1.4.
10.2.2 If using the recorder chart speed set within the range from 0.5 to 2.0 cm/s, inclusive, pulse the linac repeatedly within a
time that is short compared to the thermal time constant of the calorimeter to give a recorder deflection greater than 10 % of full
scale.
10.2.2.1 From the data, measure the voltage rise resulting from this series of pulses.
10.2.2.2 For the time interval beginning with the cessation of the radiation and equal in duration to the total time during which
the radiation dose was accumulated, measure the thermocouple voltage drop.
10.2.2.3 Calculate the ratio of the voltage from 10.2.2.2 to that of 10.2.2.1.
10.2.2.4 If this ratio is less than 0.15, continue with 10.2.3 (the thermal time constant of the calorimeter is sufficiently greater than
the radiation time for the dose to be determined accurately).
10.2.2.5 If this ratio is equal to or greater than 0.15, repeat 10.2.2 through 10.2.2.5 using a higher pulse repetition rate for a shorter
radiation time period.
10.2.3 Annotate the data recorder output, as well as the number of pulses used (see Fig. 5, Fig. 6, and Fig. 7).
10.2.4 Repeat 10.2.2 and 10.2.3 four more times, omitting the time constant determination (10.2.2.1 through 10.2.2.5).
10.2.5 If using the oscilloscope, refer to the reference manual to set the oscilloscope, pulse the linac repeatedly within a time that
is short compared to the thermal time constant of the calorimeter to ensure that the response is properly captured on the
oscilloscope.
11. Calculation and Interpretation of Results
11.1 Single-Pulse Method:
11.1.1 On the recorder output, determine the perpendicular to the time axis at the start of each transient, as shown in Fig. 3.
11.1.2 Determine whether a period of time was required for the temperature to equilibrate after the pulse, as indicated by the
presence of a spike (Fig. 5a) or a flat portion (Fig. 5b) of the data recorder trace at the end of the transient.
11.1.2.1 If no such feature is present, draw a line extrapolating the steepest part of the cooling curve following each radiation pulse
back to intersect the perpendicular line (see 11.1.1). When using digital storage oscilloscopes, built in cursors usually can be used.
NOTE 8—These lines are dashed in Fig. 3.
11.1.2.2 If such a feature is present, draw a line extrapolating from the slope of the curve where a smooth cooling trend resumes.
Do this for each pulse.
NOTE 9—These lines are dashed in Fig. 5.
F526 − 21
(a) Spike Indicating Initial Thermocouple Junction Temperature Higher than that
of the Calorimeter Block.
(b) Flat Portion Indicating Initial Thermocouple Junction Temperature Lower
than that of the Calorimeter Block.
FIG. 5 Possible Aberrations Observed in Strip-Chart Recorder Transient Signals
11.1.3 Measure along each perpendicular line the length from the start of each transient to the intersection of the perpendicular
line with the extrapolated line.
11.1.4 Convert these measurements to output voltage level.
11.1.5 For each pulse calculate and record the dose in Gy (calorimeter-block material) producing the transient, using for a
thermocouple measurement, the relation:
Dose 5 100 Vc /PG (1)
p
where:
V = deflection caused by irradiation pulse, in microvolts,
c = specific heat capacity of calorimeter-block material, J/kg·K,
p
P = temperature coefficient of the calorimeter thermocouple in the vicinity of room temperature, μV/K,
G = gain of low noise amplifier, and,
100 = numerical conversion factor, rad·kg/J.
F526 − 21
NOTE 1—Rise times have been deliberately lengthened in this figure to enable the construction of the perpendicular and extrapolated lines to be seen
more easily. The reference shot time is assigned to the midpoint of the multi-pulse train.
FIG. 6 Typical Chart Record of Calorimeter Dosimetry Using Multiple-Pulse Method
FIG. 7 Multiple Pulse Method Using a Digital Storage Scope and LNA (Five Radiation Pulses)
NOTE 10—The specific heat capacity for a material is a temperature-dependent quantity. If the temperature change in the calorimeter is large or if there
is some significant temperature-dependent changes in the specific heat in the temperature region of interest, then the user will have to useCalibration
curves for converting thermocouple voltage measurements to temperature measurements are available for some thermocouples. If available, these can be
F526 − 21
used to supplement Eq 1an integral formulation to determine the “effective” specific heat to use in this dose determination. .
11.1.6 For a thermistor measurement, use the equation (Appendix X2):
R 1R k c
~ !
A B P
Dose 5 V (2)
R R αE
A B
where:
R = value of the fixed bridge resistors, Ω,
A
R = value of the variable bridge resistor, Ω,
B
–2
k = numerical conversion constant=10 J/kg·rad,
–1
α = thermistor temperature coefficient of resistance, K ,
E = bridge voltage, V, and
V and c have the same meaning as above.
P
NOTE 11—The specific heat capacity for a material is a temperature-dependent quantity. If the temperature change in the calorimeter is large, or if there
are some significant temperature-dependent changes in the specific heat in the temperature region of interest, then the user will have to use an integral
formulation to determine the “effective” specific heat to use in
...