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Experimental Gun Brightness Measurements on a 300 kV CFEG

Published online by Cambridge University Press:  02 July 2020

Nestor J. Zaluzec  and
Alan Nicholls
Nestor J. Zaluzec
Affiliation:
MATERIALS SCIENCE DIV., ARGONNE NATIONAL LABORATORY, ARGONNE, IL., 60439, USA
Alan Nicholls
Affiliation:
UNIVERSITY OF ILLINOIS AT CHICAGO, RESEARCH RESOURCE CENTER, CHICAGO, IL., USA
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Extract

Effective use of the ANL 300kV CFEG/A AEM requires a knowledge of the probe current and size distribution during operation. In most cases this can be calculated once basic parameters of the system are experimentally determined. Central to this is a determination of the source brightness of the Cold Field Emission Gun (CFEG) under standard operating conditions of the instrument. For the last ten years most probe calculations of CFEG's have been done assuming a brightness parameter of β∼×109 A/cm2/sterad2 at 100 kV, while few if any experimental values have been reported at 300 kV. Using β and the relationship that the operating probe diameter is obtained by adding in quadrature the Gaussian probe size (dg, the CFEG source contribution), and the diameters of least confusion due to spherical abberation (ds) and diffraction limits (dd) one obtains the total probe size dt as :

Type
Advances in Instrumentation and Performance
Information
Microscopy and Microanalysis , Volume 4 , Issue S2: Proceedings: Microscopy & Microanalysis '98, Microscopy Society of America 56th Annual Meeting, Microbeam Analysis Society 32nd Annual Meeting, Atlanta, Georgia July 12-16, 1998 , July 1998 , pp. 386 - 387
Copyright
Copyright © Microscopy Society of America

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References

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5.) This work was supported by US. DoE under BES-MS W-31-109-Eng-38 at ANL.Google Scholar