ISO 15632:2021

FINAL
INTERNATIONAL ISO/FDIS
DRAFT
STANDARD 15632
ISO/TC 202
Microbeam analysis — Selected
Secretariat: SAC
instrumental performance
Voting begins on:
2020­09­23 parameters for the specification and
checking of energy-dispersive X-ray
Voting terminates on:
2020­11­18
spectrometers for use in electron
probe microscope or an electron
probe microanalyser (EPMA)
Analyse par microfaisceaux — Paramètres de performance
instrumentale sélectionnés pour la spécification et le contrôle des
spectromètres X à sélection d'énergie utilisés en microanalyse par
sonde à électrons
RECIPIENTS OF THIS DRAFT ARE INVITED TO
SUBMIT, WITH THEIR COMMENTS, NOTIFICATION
OF ANY RELEVANT PATENT RIGHTS OF WHICH
THEY ARE AWARE AND TO PROVIDE SUPPOR TING
DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
Reference number
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO­
ISO/FDIS 15632:2020(E)
LOGICAL, COMMERCIAL AND USER PURPOSES,
DRAFT INTERNATIONAL STANDARDS MAY ON
OCCASION HAVE TO BE CONSIDERED IN THE
LIGHT OF THEIR POTENTIAL TO BECOME STAN­
DARDS TO WHICH REFERENCE MAY BE MADE IN
©
NATIONAL REGULATIONS. ISO 2020

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ISO/FDIS 15632:2020(E)

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© ISO 2020
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ISO/FDIS 15632:2020(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Requirements . 3
4.1 General description . 3
4.2 Energy resolution . 4
4.3 Dead time . 4
4.4 Peak­to­background ratio . 4
4.5 Energy dependence of instrumental detection efficiency . 4
5 Check of further performance parameters . 5
5.1 General . 5
5.2 Stability of the energy scale and resolution . 5
5.3 Pile­up effects . 5
5.4 Periodical check of spectrometer performance . 5
Annex A (normative) Measurement of line widths (FWHMs) to determine the energy
resolution of the spectrometer . 6
Annex B (normative) Determination of the L/K ratio as a measure for the energy
dependence of the instrumental detection efficiency .11
Bibliography .13
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ISO/FDIS 15632:2020(E)

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non­governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www .iso .org/
iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 202, Microbeam analysis.
This third edition cancels and replaces the second edition (ISO 15632:2012), which has been technically
revised. The main changes compared to the previous edition are as follows:
— The title has been detailed;
— The definition of dead time (3.4) is more detailed;
— A Note (including a new Reference [5]) has been added to General description (4.1) related to the net
active sensor area;
— Detailed explanation on “adaptive filtering” (4.3) has been removed.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/ members .html.
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ISO/FDIS 15632:2020(E)

Introduction
Progress in energy-dispersive X-ray spectrometry (EDS) by means of improved manufacturing
technologies for detector crystals and the application of advanced pulse-processing techniques have
increased the general performance of spectrometers, in particular at high count rates and at low
energies (below 1 keV). Meanwhile, the Si-Li detector technology has been successfully replaced by the
silicon drift detector (SDD) technology which provides performance comparable to Si-Li detectors, even
at considerably higher count rates. In addition, a smaller detector capacitance results in the capability
of measuring even higher count rates and in the availability of larger area detectors. This document
has therefore been updated with criteria for the evaluation of the performance of such modern
spectrometers.
A spectrometer is commonly specified by its energy resolution at high energies defined as the full
peak width at half maximum (FWHM) of the manganese Kα line. To specify the properties in the
low energy range, values for the FWHM of carbon K, fluorine K or/and the zero peak are given by the
manufacturers. Some manufacturers also specify a peak-to-background ratio, which may be defined as
55
a peak­to­shelf ratio in a spectrum from an Fe source or as a peak-to-valley ratio in a boron spectrum.
Differing definitions of the same quantity have sometimes been employed. The sensitivity of the
spectrometer at low energies related to that at high energies depends strongly on the construction of
the detector crystal and the X-ray entrance window used. Although high sensitivity at low energies is
important for the application of the spectrometer in the analysis of light-element compounds, normally,
the manufacturers do not specify an energy dependence for spectrometer efficiency.
This document was developed in response to a worldwide demand for minimum specifications of
an energy-dispersive X-ray spectrometer. EDS is one of the most applied methods used to analyse
the chemical composition of solids and thin films. This document should permit comparison of the
performance of different spectrometer designs on the basis of a uniform specification and help to
find the optimum spectrometer for a particular task. In addition, this document contributes to the
[1]
equalization of performances in separate test laboratories. In accordance with ISO/IEC 17025 , such
laboratories should periodically check the calibration status of their equipment according to a defined
procedure. This document may serve as a guide for similar procedures in all relevant test laboratories.
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FINAL DRAFT INTERNATIONAL STANDARD ISO/FDIS 15632:2020(E)
Microbeam analysis — Selected instrumental performance
parameters for the specification and checking of energy-
dispersive X-ray spectrometers for use in electron probe
microscope or an electron probe microanalyser (EPMA)
1 Scope
This document defines the most important quantities that characterize an energy-dispersive X-ray
spectrometer consisting of a semiconductor detector, a pre-amplifier and a signal-processing unit as
the essential parts. This document is only applicable to spectrometers with semiconductor detectors
operating on the principle of solid-state ionization. This document specifies minimum requirements
and how relevant instrumental performance parameters are to be checked for such spectrometers
attached to a scanning electron microscope (SEM) or an electron probe microanalyser (EPMA). The
[2] [3]
procedure used for the actual analysis is outlined in ISO 22309 and ASTM E1508 and is outside the
scope of this document.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 23833, Microbeam analysis — Electron probe microanalysis (EPMA) — Vocabulary
ISO 22493, Microbeam analysis — Scanning electron microscopy — Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 23833, ISO 22493 and the
following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
NOTE With the exception of 3.1, 3.2, 3.2.1, 3.2.2, 3.9, 3.11, 3.12, 3.13 and 3.14, these definitions are given in
[2] [4]
the same or analogous form in ISO 22309 , ISO 18115­1 and ISO 23833.
3.1
energy-dispersive X-ray spectrometer
device for determining X-ray signal intensity as a function of the energy of the radiation by recording
the whole X-ray spectrum simultaneously
Note 1 to entry: The spectrometer consists of a solid-state detector, a preamplifier, and a pulse processor. The
detector converts X-ray photon energy into electrical current pulses which are amplified by the preamplifier. The
pulse processor then sorts the pulses by amplitude so as to form a histogram distribution of X-ray signal intensity
(3.8) vs energy.
3.2 Measurement rates
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ISO/FDIS 15632:2020(E)

3.2.1
count rate
number of X-ray photons per second
3.2.2
input count rate
ICR
number of X-ray photons absorbed in the active detector area per second that are input to the electronics
3.2.3
output count rate
OCR
number of valid X-ray photon measurements per second that are output by the electronics and stored in
memory, including sum peaks
Note 1 to entry: When the electronics measures individual X-ray photon energies, there is some dead time (3.4)
associated with each individual measurement. Consequently, the number of successful measurements is less
than the number of incident photons in every practical case. Thus, the accumulation rate into the spectrum
(output count rate (3.2.3)) is less than the count rate of photons that cause signals in the detector (input count rate
(3.2.2)). Output count rate (3.2.3) may be equal to input count rate (3.2.2), e.g. at very low count rates and for very
short measurements.
3.3
real time
duration in seconds of an acquisition as it would be measured with a conventional clock
Note 1 to entry: For X-ray acquisition, in every practical case the real time (3.3) always exceeds the live time (3.5).
3.4
dead time
time during which the system is unable to record a photon measurement because it is busy processing a
previous event (frequently expressed as a percentage of the real time)
Note 1 to entry: Dead time = real time – live time.
Note 2 to entry: Dead-time fraction = 1 − OCR/ICR.
3.5
live time
effective duration of an acquisition, in seconds, after accounting for the presence of dead time (3.4)
Note 1 to entry: Live time = real time for an analysis minus cumulative dead time.
Note 2 to entry: Live-time fraction = 1 − dead-time fraction.
3.6
spectral channel
discrete interval of the measured energy for the histogram of recorded measurements with a width
defined by a regular energy increment
3.7
instrumental detection efficiency
ratio of quantity of detected photons and quantity of the photons incident on the active detector area
3.8
signal intensity
strength of the signal in counts per channel or counts per second per channel at the spectrometer
output after pulse processing
Note 1 to entry: This definition permits intensity to be expressed as either “counts” or “counts per second” (CPS).
The distinction is not relevant to the procedures described in this standard so long as either one or the other is
consistently employed.
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ISO/FDIS 15632:2020(E)

3.9
peak height
maximum signal intensity (3.8) of a spectral peak measured as height of the peak above a defined
background signal (3.11)
3.10
peak area
net peak area
sum of signal intensities (3.8) of a spectral peak after background signal (3.11) removal
3.11
background signal
continuous X-ray spectrum
continuum
non-characteristic component of an X-ray spectrum arising from the bremsstrahlung (3.12) and
other effects
Note 1 to entry: Apart from the bremsstrahlung (3.12), degraded events occurring due to the operation of the
spectrometer may contribute to the background signal (3.11). Extraneous signals arising from one or more parts
of the spectrometer, microscope chamber or specimen itself (by X-ray scattering) may also add to the background
signal (3.11).
3.12
bremsstrahlung
braking radiation
non-characteristic X-ray spectrum created by electron deceleration in the coulombic field of an atom
and having an energy distribution from 0 up to the incident beam energy
3.13
X-ray take-off angle
TOA
angle between the specimen surface and the direction where exiting X-rays will strike the centre of the
detector’s sensor
Note 1 to entry: With increasing solid angle encompassed by the detector, TOA may vary significantly within a
range around that TOA corresponding to the central position on the X-
...