Magnetic shielding in ultrahigh vacuum systems: Using a computer code to design a shield for an electron energy loss spectrometer

The electron energy loss spectrometer developed at Berkeley differs from most other ones in four ways: 1) it uses the projector lens crossover as the spectrometer entrance object plane, 2) its magnet is asymmetric so that the entrance object is de-magnified about 5x, 3) it counts electrons admitted through the energy-selecting slit singly at rates up to 20MHz while adding zero dark count, and 4) it fits neatly at the back of the available leg space of the electron microscope, and requires no substantial alterations to the microscope. The energy resolution attainable routinely at any primary voltage is 3eV over an energy loss range 0 to 1keV, as illustrated by resolving the π* transition on the K-edge of amorphous carbon (Fig. 1). The 3 eV limit comes mainly from 120Hz stray magnetic fields (the 60Hz component has been compensated out). Fast scanning of the spectrum improves the resolution to 1eV (Fig. 2). This indicates that with proper magnetic shielding of the electron flight path, especially in the microscope viewing chamber which is made out of brass, the energy resolution attainable with the spectrometer will be limited only by the energy spread of the primary beam.

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High resolution electron energy loss spectrometer for the study of vapor phase samples

Journal of Electron Spectroscopy and Related Phenomena ◽

10.1016/j.elspec.2006.11.015 ◽

2007 ◽

Vol 156-158 ◽

pp. 145-149 ◽

Cited By ~ 4

Author(s):

S. Urpelainen ◽

M. Huttula ◽

P. Kovala ◽

A. Mäkinen ◽

A. Caló ◽

...

Keyword(s):

High Resolution ◽

Energy Loss ◽

Electron Energy ◽

Vapor Phase ◽

Resolution Electron ◽

Electron Energy Loss Spectrometer ◽

Electron Energy Loss

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A New High Performance Electron Energy Loss Spectrometer for use with Monochromated Microscopes

Microscopy and Microanalysis ◽

10.1017/s1431927600030610 ◽

2001 ◽

Vol 7 (S2) ◽

pp. 908-909

Author(s):

H.A. Brink ◽

M. Barfels ◽

B. Edwards ◽

P. Burgner

Keyword(s):

Energy Loss ◽

Electron Energy ◽

Energy Resolution ◽

Optical Design ◽

Electron Source ◽

High Voltage Power Supply ◽

Electron Energy Loss Spectrometer ◽

Electron Microscopes ◽

Electron Energy Loss ◽

Better Than

A new type of electron energy loss spectrometer for use with monochromated microscopes is presented. The energy resolution of the spectrometer is better than 0.100 eV. A completely new electron optical design with a number of extra optical elements and advanced tuning software makes it possible to correct spectrum aberrations to 4th order, which increases sensitivity and collection angles. New high-stability electronics make it possible to maintain energy resolution over a period of several minutes in a practical laboratory environment.The energy resolution of Transmission Electron Microscopes (TEMs) equipped with electron energy loss spectrometers is determined by a combination of the energy spread of the electron source, the stability of the microscope’s high voltage power supply, and the energy resolution of the spectrometer. Commercial microscopes usually employ electron sources with an energy distributions of around 0.5 eV or more (FWHM), limiting the energy ultimate energy resolution that can be achieved. Recently FEI constructed a special 200 kV TEM with a built-in monochromator which makes it possible to monochromize the electron source to better than 0.100 eV. A prototype of the presented spectrometer has been installed on this microscope.

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