Blind deconvolution of time-of-flight mass spectra from atom probe tomography

2013 ◽  
Vol 132 ◽  
pp. 60-64 ◽  
Author(s):  
L.J.S. Johnson ◽  
M. Thuvander ◽  
K. Stiller ◽  
M. Odén ◽  
L. Hultman
Keyword(s):  
Atom Probe Tomography ◽  
Mass Spectra ◽  
Blind Deconvolution ◽  
Time Of Flight ◽  
Atom Probe

Kinetic-Energy Discrimination for Atom Probe Tomography

2011 ◽  
Vol 17 (1) ◽  
pp. 1-14 ◽  
Author(s):  
Thomas F. Kelly
Keyword(s):  
Kinetic Energy ◽  
Atom Probe Tomography ◽  
Mass Spectra ◽  
Three Dimensional ◽  
Time Of Flight ◽  
Atom Probe ◽  
Flight Path ◽  
Energy Discrimination ◽  
Energy Information ◽  
Peak Discrimination

AbstractThe benefits of using kinetic-energy information to aid ion discrimination in atom probe tomography (APT) are explored. Ion peak interferences in time-of-flight (TOF) mass spectra are categorized by difficulty of discrimination using TOF and kinetic-energy information. Several of these categories, which are intractable interferences when only TOF information is available, may be discriminated when kinetic-energy information also is available. Furthermore, many opportunities for removing noise from composition determinations and three-dimensional images are enabled. Modest kinetic-energy resolving powers (KRPs) of 10 or so should be sufficient to have a major impact on APT. With KRP of about 100, the energy deficits in voltage pulsing may be resolved to enable peak discrimination in straight-flight-path instruments. Real examples and simulated mass spectra are used to illustrate the benefits of kinetic-energy discrimination. Many of the conclusions are applicable generally in TOF spectroscopy. Current detectors do not provide the kinetic energy of incoming ions, but there are realistic prospects for building such detectors and these are discussed. A program to develop these detectors should be pursued.

On the Field Evaporation Behavior of a Model Ni-Al-Cr Superalloy Studied by Picosecond Pulsed-Laser Atom-Probe Tomography

2008 ◽  
Vol 14 (6) ◽  
pp. 571-580 ◽  
Author(s):  
Yang Zhou ◽  
Christopher Booth-Morrison ◽  
David N. Seidman
Keyword(s):  
Atom Probe Tomography ◽  
Mass Spectra ◽  
Pulsed Laser ◽  
Picosecond Laser ◽  
Atom Probe ◽  
Resolving Power ◽  
Noise Levels ◽  
Thermally Activated ◽  
Mass Resolving Power

AbstractThe effects of varying the pulse energy of a picosecond laser used in the pulsed-laser atom-probe (PLAP) tomography of an as-quenched Ni-6.5 Al-9.5 Cr at.% alloy are assessed based on the quality of the mass spectra and the compositional accuracy of the technique. Compared to pulsed-voltage atom-probe tomography, PLAP tomography improves mass resolving power, decreases noise levels, and improves compositional accuracy. Experimental evidence suggests that Ni2+, Al2+, and Cr2+ ions are formed primarily by a thermally activated evaporation process, and not by post-ionization of the ions in the 1+ charge state. An analysis of the detected noise levels reveals that for properly chosen instrument parameters, there is no significant steady-state heating of the Ni-6.5 Al-9.5 Cr at.% tips during PLAP tomography.

Enhancing Element Identification by Expectation–Maximization Method in Atom Probe Tomography

2019 ◽  
Vol 25 (2) ◽  
pp. 367-377 ◽  
Author(s):  
Francois Vurpillot ◽  
Constantinos Hatzoglou ◽  
Bertrand Radiguet ◽  
Gerald Da Costa ◽  
Fabien Delaroche ◽  
...  
Keyword(s):  
Data Analysis ◽  
Data Visualization ◽  
Expectation Maximization ◽  
Atom Probe Tomography ◽  
Mass Spectra ◽  
Signal To Noise Ratio ◽  
Atom Probe ◽  
Decomposition Methods ◽  
Signal To Noise ◽  
Extract Information

AbstractThis paper describes an alternative way to assign elemental identity to atoms collected by atom probe tomography (APT). This method is based on Bayesian assignation of label through the expectation–maximization method (well known in data analysis). Assuming the correct shape of mass over charge peaks in mass spectra, the probability of each atom to be labeled as a given element is determined, and is used to enhance data visualization and composition mapping in APT analyses. The method is particularly efficient for small count experiments with a low signal to noise ratio, and can be used on small subsets of analyzed volumes, and is complementary to single-ion decomposition methods. Based on the selected model and experimental examples, it is shown that the method enhances our ability to observe and extract information from the raw dataset. The experimental case of the superimposition of the Si peak and N peak in a steel is presented.

Atom Probe Tomography for Isotopic Analysis: Development of the 34S/32S System in Sulfides

2021 ◽  
pp. 1-14
Author(s):  
Phillip Gopon ◽  
James O. Douglas ◽  
Frederick Meisenkothen ◽  
Jaspreet Singh ◽  
Andrew J. London ◽  
...  
Keyword(s):  
Atom Probe Tomography ◽  
Time Of Flight ◽  
Simulated Data ◽  
Isotopic Analysis ◽  
Atom Probe ◽  
Standard Material ◽  
Peak Fitting ◽  
Isotopic Analyses ◽  
Fitting Algorithm ◽  
Adaptive Peak

Using a combination of simulated data and pyrite isotopic reference materials, we have refined a methodology to obtain quantitative δ34S measurements from atom probe tomography (APT) datasets. This study builds on previous attempts to characterize relative 34S/32S ratios in gold-containing pyrite using APT. We have also improved our understanding of the artifacts inherent in laser-pulsed APT of insulators. Specifically, we find the probability of multi-hit detection events increases during the APT experiment, which can have a detrimental effect on the accuracy of the analysis. We demonstrate the use of standardized corrected time-of-flight single-hit data for our isotopic analysis. Additionally, we identify issues with the standard methods of extracting background-corrected counts from APT mass spectra. These lead to inaccurate and inconsistent isotopic analyses due to human variability in peak ranging and issues with background correction algorithms. In this study, we use the corrected time-of-flight single-hit data, an adaptive peak fitting algorithm, and an improved deconvolution algorithm to extract 34S/32S ratios from the S2+ peaks. By analyzing against a standard material, acquired under similar conditions, we have extracted δ34S values to within ±5‰ (1‰ = 1 part per thousand) of the published values of our standards.

scholarly journals Best Practices for Analysis of Carbon Fibers by Atom Probe Tomography

2021 ◽  
pp. 1-10
Author(s):  
Marcus Johansen ◽  
Fang Liu
Keyword(s):  
Best Practices ◽  
Carbon Fibers ◽  
Atom Probe Tomography ◽  
Mass Spectra ◽  
High Spatial Resolution ◽  
Atom Probe ◽  
Three Dimensions ◽  
Significant Development ◽  
Fiber Technology ◽  
Multiple Hit

Carbon fiber technology drives significant development in lightweight and multifunctional applications. However, the microstructure of carbon fibers is not completely understood. A big challenge is to obtain the distribution of heteroatoms, for instance nitrogen, with high spatial resolution in three dimensions. Atom probe tomography (APT) has the potential to meet this challenge, but APT of carbon fibers is still relatively unexplored. We performed APT on three types of carbon fibers, including one high modulus type and two intermediate modulus types. Here, we present the methods to interpret the complex mass spectra of carbon fibers, enhance the mass resolution, and increase the obtained analysis volume. Finally, the origin of multiple hit events and possible methods to mitigate multiple hit events are also discussed. This paper provides guidance for future APT studies on carbon fibers, and thus leads the way to a deeper understanding of the microstructure, and consequently advancements in wide applications of carbon fibers.

Laser-Assisted Atom Probe Tomography of Oxide Materials

2007 ◽  
Vol 13 (5) ◽  
pp. 342-346 ◽  
Author(s):  
Christian Oberdorfer ◽  
Patrick Stender ◽  
Christoph Reinke ◽  
Guido Schmitz
Keyword(s):  
Atom Probe Tomography ◽  
Mass Spectra ◽  
Laser Pulses ◽  
Careful Analysis ◽  
Atom Probe ◽  
Oxide Materials ◽  
Field Evaporation ◽  
Conductive Materials ◽  
Lattice Planes ◽  
Thermal Pulses

Atom probe tomography provides a chemical analysis of nanostructured materials with outstanding resolution. However, due to the process of field evaporation triggered by nanosecond high voltage pulses, the method is usually limited to conductive materials. As part of recent efforts to overcome this limitation, it is demonstrated that the analysis of thick NiO and WO3 oxide layers is possible by laser pulses of 500 ps duration. A careful analysis of the mass spectra demonstrates that the expected stoichiometries are well reproduced by the measurement. The reconstruction of lattice planes proves that surface diffusion is negligible also in the case of thermal pulses.

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