High Resolution Electron Energy Loss Spectrometer (EELS)
- Ultrahigh resolution of 0.5 meV FWHM
- Guaranteed detector current ≥10 pA at 1.0 meV resolution (FWHM)
- Space-charge optimized, double-pass monochromator with dual analyzer
- High-transmission zoom lens system for operation from 1-200 eV impact energy
- Low-noise digital-control electronics with menu driven software and auto-optimization modes
- User selectable scan ranges up to 50 eV for vibronic/electronic applications
- Available as a component or with complete UHV system
- Demonstrated performance and reliability in laboratories worldwide
The ELS3000 Spectrometer
The ELS3000 is a state-of-the-art instrument based on the development by Professor Harald Ibach and his co-workers at the KFA, Jülich, Germany. This instrument design initially led to the first reported resolution below 1.0 meV [0.98 meV (FWHM) for CO absorbed on Ir (100) (see figure below)]. The ELS3000 is now manufactured by LK Technologies per a worldwide licensing agreement with the KFA. The ELS3000 version of this design has obtained a resolution as high as 0.5 meV in direct beam geometry and less than 0.8 meV on a polymer film (see figure below). The ELS3000 was the first instrument to achieve such a high resolution on a polymer surface.
The ELS3000 takes advantage of a highly optimized double-pass monochromator design whereby space charge compensation of the 127° cylindrical deflector is made in both monochromator stages by careful choices of parameters. The pre-monochromator operates as a "retarding" monochromator whereby the kinetic energy of electrons exiting this stage and entering the second monochromator is about 1/5 the nominal pass energy of the pre-monochromator. The second monochromator acts as a non-retarding monochromator with a deflection angle appropriate to reduced space change. The electron gun employs a repeller geometry with a LaB6 cathode.
The ELS3000 analyzer is also of double-pass geometry. A symmetrical system of input-output "zoom" lenses positioned between monochromator and analyzer is used to focus and decelerate/ accelerate the electron beam to and from the sample surface.A patented, non-circular symmetric lens design is employed that yields excellent transmission characteristics. The combined monochromator-analyzer system with this high transmission lens results in exceptional detector currents as a function of energy resolution (Table 1).
General Performance Specifications
The ELS3000 has achieved a resolution of 0.5 meV in direct beam geometry and 0.8 meV on a polymer film (PTFE) while maintaining high detector current and counting rates. The Table 1 below shows both guaranteed specifications as well as optimal results which have been achieved in our testing laboratory. Every ELS3000 is carefully tested before shipment to meet or exceed the guaranteed specifications. Since improvements are made on a regular basis, the prospective customer should consult the company for the latest specifications.
Click on graph to enlarge
The ELS3000 is mounted as an integral unit on a 12 inch (305 mm) O. D. vacuum flange. Construction materials are all non-magnetic to insure the lowest possible stray magnetic field (e.g. no stainless steel is utilized). Dual magnetic shields are provided at the flange to interface with the chamber magnetic shields. Angle-dependent studies are accomplished by rotation of the monochromator from "straight through" position to 90° away from straight through by means of a precision, linear-feedthrough/rack-and-pinion gear system. Importantly, a direct readout of the monochromator angle is provided by a scale which is viewed through a port on the mounting flange. This removes the uncertainty associated with gear backlash or drive calibration.
Electronics Specification -- Model ELS3000 DAC
Digital-control electronics package for control of the Model ELS3000 spectrometer. Includes digital control of spectrometer voltages and readout of critical currents. Package includes picoammeter, noise reduction filter, power supply, PC compatible computer, floppy drive, and interface equipment. Includes Model LK2000-CE counting electronics package. Includes menu-driven software for data acquisition and control of spectrometer voltages. Operation is for 1-200 eV kinetic energy. Scan range up to 50 eV. Ripple on voltages less than 250 microvolt p-p. Controller operates with sample near earth ground.
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