ASTM E2426-10

Standard Practice for Pulse Counting System Dead Time Determination by Measuring Isotopic Ratios with SIMS

SIGNIFICANCE AND USE
Electron multipliers are commonly used in pulse-counting mode to detect ions from magnetic sector mass spectrometers. The electronics used to amplify, detect and count pulses from the electron multipliers always have a characteristic time interval after the detection of a pulse, during which no other pulses can be counted. This characteristic time interval is known as the “dead time.” The dead time has the effect of reducing the measured count rate compared with the “true” count rate.
In order to measure count rates accurately over the entire dynamic range of a pulse counting detector, such as an electron multiplier, the dead time of the entire pulse counting system must be well known. Accurate count rate measurement forms the basis of isotopic ratio measurements as well as elemental abundance determinations.
The procedure described herein has been successfully used to determine the dead time of counting systems on SIMS instruments. The accurate determination of the dead time by this method has been a key component of precision isotopic ratio measurements made by SIMS.
SCOPE
1.1 This practice provides the Secondary Ion Mass Spectrometry (SIMS) analyst with a method for determining the dead time of the pulse-counting detection systems on the instrument. This practice also allows the analyst to determine whether the apparent dead time is independent of count rate.
1.2 This practice is applicable to most types of mass spectrometers that have pulse-counting detectors.
1.3 This practice does not describe methods for precise or accurate isotopic ratio measurements.
1.4 This practice does not describe methods for the proper operation of pulse counting systems and detectors for mass spectrometry.
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: 31-May-2010
• ICS: 71.040.50 - Physicochemical methods of analysis
• Technical Committee: E42 - Surface Analysis
• Drafting Committee: E42.06 - SIMS

Relations

• Replaces: ASTM E2426-05 - Standard Practice for Pulse Counting System Dead Time Determination by Measuring Isotopic Ratios with SIMS
• Effective Date: 01-Jun-2010
• Replaced By: ASTM E2426-10(2019) - Standard Practice for Pulse Counting System Dead Time Determination by Measuring Isotopic Ratios with SIMS
• Effective Date: 01-Jan-2019

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: E2426 − 10
Standard Practice for
Pulse Counting System Dead Time Determination by
1
Measuring Isotopic Ratios with SIMS
This standard is issued under the fixed designation E2426; 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.
1. Scope 3. Terminology
1.1 This practice provides the Secondary Ion Mass Spec- 3.1 Definitions:
trometry (SIMS) analyst with a method for determining the 3.1.1 SeeTerminology E673 for definitions of terms used in
dead time of the pulse-counting detection systems on the SIMS.
instrument. This practice also allows the analyst to determine 3.1.2 See Terminology ISO 21270 for definitions of terms
whether the apparent dead time is independent of count rate. related to counting system measurements.
m2 m1
3.1.3 isotopic ratio, n—written as X/ X, for an element
1.2 This practice is applicable to most types of mass
X with isotopes m1 and m2, refers to the ratios of their atomic
spectrometers that have pulse-counting detectors.
abundances. When it is a value measured in a mass spectrom-
1.3 This practice does not describe methods for precise or
eter it refers to the ratio of the signal intensities for the two
accurate isotopic ratio measurements.
species.
m2 m2
3.1.3.1 Discussion—Thenotation∆ Xorδ Xreferstothe
1.4 This practice does not describe methods for the proper
operation of pulse counting systems and detectors for mass fractional deviation of the measured isotopic ratio from the
m2
standard ratio or reference. In this practice, ∆ X will refer to
spectrometry.
the fractional deviation of the measured ratio, uncorrected for
1.5 This standard does not purport to address all of the
m2
mass-fractionation (see 3.1.4) and δ X will refer to the
safety concerns, if any, associated with its use. It is the
fractional deviation of the measured ratio that has been
responsibility of the user of this standard to establish appro-
corrected for mass-fractionation. An example for magnesium
priate safety and health practices and determine the applica-
(Mg) is:
bility of regulatory limitations prior to use.
25 24
~ Mg/ Mg!
25 Meas
∆ Mg 5 21 (1)
25 24
2. Referenced Documents Mg/ Mg
~ !
Ref
2
2.1 ASTM Standards:
where:
E673 Terminology Relating to SurfaceAnalysis (Withdrawn 25 24 5
( Mg/ Mg) = 0.12663 .
Ref
3
2012)
3.1.4 mass-fractionation, n—sometimes called “mass-bias,”
4
2.2 ISO Standards:
referstothetotalmass-dependent,intra-isotopevariationinion
ISO 21270 Surface Chemical Analysis—X-ray photoelec- intensity observed in the measured isotopic ratios for a given
tron and Auger electron spectrometers—Linearity of in- elementcomparedwiththereferenceratios.Itcanbeexpressed
tensity scale; and references 1, 2, 10, 13 and 14 therein. as the fractional deviation per unit mass.
3.1.4.1 Discussion—The mass of an isotope i of element X
mi
( X) shall be represented by the notation m, where “i”isan
i
integer.
1
This practice is under the jurisdiction of ASTM Committee E42 on Surface
Analysis and is the direct responsibility of Subcommittee E42.06 on SIMS.
4. Summary of Practice
CurrenteditionapprovedJune1,2010.PublishedJuly2010.Originallyapproved
in 2005. last previous edition approved in 2006 as E2426 – 05 (2006). DOI:
4.1 This practice describes a method whereby the overall
10.1520/E2426-10.
2
effective dead time of a pulse counting system can be deter-
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
mined by measuring isotopic ratios of an element having at
Standards volume information, refer to the standard’s Document Summary page on
least 3 isotopes. One of the isotopes should be approximately
the ASTM website.
3
The last approved version of this historical standard is referenced on
www.astm.org.
4 5
Available from International Organization for Standardization (ISO), 1, ch. de Catanzaro, E. J., Murphy T. J., Garner E. L., and Shields W. R., “Absolute
la Voie-Creuse, Case postale 56, CH-1211, Geneva 20, Switzerland, http:// IsotopicAbundanceRatiosandAtomicWeightofMagnesium,” Journal of Research
www.iso.ch. of the National Bureau of Standards, Vol 70a, 1966, pp. 453–458.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

---------------------- Page: 1 ----------------------
E2426 − 10
afactorof10moreabundantthantheotherssothatafirstorder bination of the two. In a retriggerable system the length of the
estimate of the dead time can be calculated that will be close to discriminator output pulse is increased if a pulse arrives at th
...

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:E2426–05 Designation:E2426–10
Standard Practice for
Pulse Counting System Dead Time Determination by
1
Measuring Isotopic Ratios with SIMS
This standard is issued under the fixed designation E2426; 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.
1. Scope
1.1 This practice provides the Secondary Ion Mass Spectrometry (SIMS) analyst with a method for determining the dead time
of the pulse-counting detection systems on the instrument. This practice also allows the analyst to determine whether the apparent
dead time is independent of count rate.
1.2 This practice is applicable to most types of mass spectrometers that have pulse-counting detectors.
1.3 This practice does not describe methods for precise or accurate isotopic ratio measurements, or both. measurements.
1.4 This practice does not describe methods for the proper operation of pulse counting systems and detectors for mass
spectrometry.
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.
2. Referenced Documents
2
2.1 ASTM Standards:
E673 Terminology Relating to Surface Analysis
3
2.2 ISO Standard: ISO Standards:
ISO 21270Surface chemical analysis — X-ray photoelectron and Auger electron spectrometers — Linearity of intensity scale;
and references 1, 2, 10, 13 and 14 therein. ISO 21270 Surface Chemical Analysis—X-ray photoelectron and Auger electron
spectrometers—Linearity of intensity scale; and references 1, 2, 10, 13 and 14 therein.
1
This practice is under the jurisdiction of ASTM Committee E42 on Surface Analysis and is the direct responsibility of Subcommittee E42.06 on SIMS.
Current edition approved Nov. 1, 2005. Published January 2006. DOI: 10.1520/E2426-05.
Current edition approved June 1, 2010. Published July 2010. Originally approved in 2005. last previous edition approved in 2006 as E2426 – 05 (2006). DOI:
10.1520/E2426-10.
2
For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM 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.
3
Available from International Organization for Standardization (ISO), 1 rue1, ch. de Varembé, la Voie-Creuse, Case postale 56, CH-1211, Geneva 20, Switzerland,
http://www.iso.ch.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
1

---------------------- Page: 1 ----------------------
E2426–10
3. Terminology
3.1 Definitions:
3.1.1 See Terminology E673 for definitions of terms used in SIMS.
3.1.2 See Terminology ISO 21270 for definitions of terms related to counting system measurements.
m2 m1
3.1.3 isotopic ratio, n—written as X/ X, for an element X with isotopes m1 and m2, refers to the ratios of their atomic
abundances. When it is a value measured in a mass spectrometer it refers to the ratio of the signal intensities for the two species.
m2 m2
3.1.3.1 Discussion—The notation D X or d X refers to the fractional deviation of the measured isotopic ratio from the
m2
standard ratio or reference. In this guide,practice, D X will refer to the fractional deviation of the measured ratio, uncorrected
m2
for mass-fractionation (see 3.1.4) and d X will refer to the fractional deviation of the measured ratio that has been corrected for
mass-fractionation. An example for magnesium (Mg) is:
25 24
~ Mg/ Mg!
Meas
25
D Mg 5 – 1 (1)
25 24
~ Mg/ Mg!
Ref
where:
25 24 4
( Mg/ Mg) = 0.12663 .
Ref
3.1.4 mass-fractionation, n—sometimes called “mass-bias,” refers to the total mass-dependent, intra-isotope variation in ion
intensity observed in the measured isotopic ratios for a given element compared with the reference ratios. It can be expressed as
the fractional deviation per unit mass.
mi
3.1.4.1 Discussion—Themassofanisotope iofelement X( X)shallberepresentedbythenotation m,where“i”isaninteger.
i
4. Summary of Practice
4.1 This practice describes a method whereby the overall effective dead time of a pulse counting system can be determined by
measuring isotopic ratios of an element having at least 3 isotopes. One o
...