ISO/FDIS 15632

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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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

resolution of the spectrometer .............................................................................................................................................................. 6

dependence of the instrumental detection efficiency ................................................................................................11

Bibliography .............................................................................................................................................................................................................................13

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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

— A Note (including a new Reference [5]) has been added to General description (4.1) related to the net

Any feedback or questions on this document should be directed to the user’s national standards body. A

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

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

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

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.

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

procedure used for the actual analysis is outlined in ISO 22309 and ASTM E1508 and is outside the

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

For the purposes of this document, the terms and definitions given in ISO 23833, ISO 22493 and the

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

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

device for determining X-ray signal intensity as a function of the energy of the radiation by recording

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

number of X-ray photons absorbed in the active detector area per second that are input to the electronics

number of valid X-ray photon measurements per second that are output by the electronics and stored in

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

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).

time during which the system is unable to record a photon measurement because it is busy processing a

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.

discrete interval of the measured energy for the histogram of recorded measurements with a width

ratio of quantity of detected photons and quantity of the photons incident on the active detector area

strength of the signal in counts per channel or counts per second per channel at the spectrometer

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

maximum signal intensity (3.8) of a spectral peak measured as height of the peak above a defined

sum of signal intensities (3.8) of a spectral peak after background signal (3.11) removal

non-characteristic component of an X-ray spectrum arising from the bremsstrahlung (3.12) and

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

non-characteristic X-ray spectrum created by electron deceleration in the coulombic field of an atom

angle between the specimen surface and the direction where exiting X-rays will strike the centre of the

Note 1 to entry: With increasing solid angle encompassed by the detector, TOA may vary significantly within a