Thermo Electron Scientific Instruments Corporation

Wisconsin Alumni Research Foundation

Thermo Noran, Inc.

Patrick Paul Camus

David B Rohde

Thomas F Kelly

Gregory S Fritz

Louis M Holzman

Dean A Stocker

Sateeshchandra S Bajikar

Thomas B Jacobs

David J Larson

Dale Anders Wade

An X-ray spectroscope collects an energy-dispersive spectrum from a sample under analysis, and generates a list of candidate elements that may be present in the sample. A wavelength dispersive spectral collector is then tuned to obtain X-ray intensity measurements at the energies/wavelengths of some or all of the candidate elements, thereby verifying whether or not these candidate elements are in fact present in the sample. Additionally, the alignment of the wavelength dispersive spectral collector versus the sample can be optimized by tuning the wavelength dispersive spectral collector to the energy/wavelength of a selected one of the candidate elements&#x2014;preferably one whose presence in the sample has been verified, or one which has a high likelihood of being present in the sample&#x2014;and then varying the alignment of the wavelength dispersive spectral collector versus the sample until the wavelength dispersive spectral collector returns the maximum intensity reading for the selected candidate element. Intensity readings for the other candidate elements can then be collected at this optimized alignment.

Synergistic energy-dispersive and wavelength-dispersive X-ray spectrometry

In an energy dispersive spectrometer wherein event (particle/photon) detection is performed by counting events spaced by greater than a shaping time, events which are spaced by less than the shaping time are also collected and counted. These 'combined events' are treated similarly to 'single events' which are spaced by greater than the shaping time, and can be used to generate combined-event spectra for comparison and/or use with the conventional single-event spectra. The combined-event spectra can be compared to the single-event spectra to provide an indication of data quality; can be subtracted from the single-event spectra to remove artifacts, and/or can be deconvolved into a single-event spectrum to increase the resolution of the single-event spectrum.

Processing of spectrometer pile-up events

A system for performing spectral microanalysis delivers analysis results during the course of data collection. As spectra are collected from pixels on a specimen, the system periodically analyzes the spectra to statistically derive underlying spectra representing proposed specimen components, wherein the derived spectra combine in varying proportions to result (at least approximately) in the measured spectra at each pixel. Those pixels having the same dominant proposed component, and/or which contain at least approximately the same proportions of the proposed components, may then have their measured spectra combined (i.e., added or averaged). These spectra may then be cross-referenced via reference libraries to identify the components actually present. During the foregoing analysis, the measured spectra are preferably condensed, as by reducing the number of energy channels/intervals making up the measured spectra and/or by combining the measured spectra of adjacent pixels, to reduce the size of the data cube and expedite analysis results.

Automatic material labeling during spectral image data acquisition

A system and method for correcting automatically the distortions in electron background diffration (EBSD) patterns which result from magnetic fields produced by some scanning electron microscopes (SEMs) used for collecting such patterns from polycrystalline sample materials. The method may be implemented as a software program running on a computer which is part of a conventional system for obtaining and analyzing EBSD patterns to obtain crystallographic information about the sample material. The method includes a calibration procedure and a correction procedure. In the calibration procedure, a distorted EBSD pattern obtained from a calibration sample is displayed on an operator display and user interface. Using an input device, an operator defines segment endpoints along a Kikuchi band in the distorted EBSD pattern image. From the user defined segment endpoints, correction parameters are calculated based on a mathematical curve (e.g., cubic spline) fitting the endpoints. The correction parameters may also be corrected automatically, without user intervention. The correction parameters are saved and may be used to correct magnetic field distortions in all subsequent EBSD patterns obtained using the SEM geometry for which the calibration procedure is run. In the correction procedure, the correction parameters are employed to shift lines of pixels in the distorted EBSD pattern image by an amount defined by the correction parameters to correct the distortion in the EBSD pattern image. Thus corrected EBSD pattern images may be displayed to a operator of the system and saved for subsequent EBSD pattern analysis using conventional EBSD pattern analysis techniques.

Method and apparatus for correcting magnetic field distortions in electron backscatter diffraction patterns obtained in an electron microscope

An atom probe provides rapidly pulsed field evaporation/desorption of ions from a tip utilizing a local extraction electrode positioned closely adjacent to the tip. A bias potential is applied between the tip and the local extraction electrode which provides an electric field at the tip which is less than but near the field intensity required for field evaporation of ions. Additional potential is applied between the tip and the extraction electrode in relatively low over-voltage pulses to obtain field evaporation of ions without substantially accelerating the ions. The ions extracted from the tip by the sharply defined pulses pass through an aperture in the extraction electrode and are accelerated by a large potential difference between the tip and a detector spaced from the tip and the local extraction electrode. An intermediate acceleration electrode may be positioned between the extraction electrode and the detector, with the acceleration electrode having an aperture therein to pass ions therethrough to the detector. The acceleration electrode is maintained at a higher potential with respect to the tip than the extraction electrode, and may be maintained at the same potential as the detector so that ions passed through the acceleration electrode coast to the detector. The use of relatively low voltage pulses to obtain evaporation of ions permits rapid repetition of the pulses, on the order of hundreds of thousands of pulses per second, to allow rapid accumulation of atom probe data.

High mass resolution local-electrode atom probe

A position sensitive detector has one or more wedge-and-wedge anode units, each of which has four electrodes on a planar surface arranged in a plurality of sets of four wedge-shaped electrode elements each, with the sets extending across the anode unit. Two of the electrode elements become progressively wider from set to set from one side of the anode unit to the other, while the other two electrode elements become progressively narrower. The respective electrode elements in each set are electrically connected together to complete the four electrodes. The charge measured on each of the four electrodes can be utilized to determine the X and Y coordinates of an event which results in a charge cloud impacting the anode, with redundant information available from the four electrodes. The coordinates calculated using charge information from any three of the electrodes can be compared with information calculated from the charge measured from the fourth electrode and two of the other electrodes, and the two sets of calculations can be compared. If each set of calculations does not yield the same result, two or more events have occurred simultaneously at different positions, and the measured data can be rejected to avoid erroneous data. The electrodes of large arrays of such anode units can be readily connected together to cover a large detector area with a minimal number of data output lines required, and with the capability of determining the position of simultaneous events by taking advantage of the redundant information available from each anode unit.

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Middleton, WI, United States of America

Patrick Paul Camus