|LIBRA® 200 MC|
Monochromated Field Emitter
An exclusive monochromator (MC) technology for the field emission gun may be specified as a factory option or as a field upgrade to the standard LIBRA® 200FE to create the
Symmetric hexapole shaped fields in the electrostatic omega-type imaging element MC cancel 2nd order aberrations to yield minimum loss of brightness while producing a non-dispersive image of the source at the MC exit plane. As a result of no source image dispersion the monochromator also maintains the original spot size and unlike other dispersive designs is ideal for both MC-STEM and EELS spectroscopy under all operating conditions.
A large energy dispersion of 12 um/eV allows a range of selectable energy widths from ~0.7 eV (non-monochromated) down to 0.2 eV. Energy width is controlled by a set of mechanically or electro-optically driven apertures in the energy dispersive plane of the element. The electrostatic gun lens control and MC is persistently powered and continuously ready for use with no significant alignments required over a wide range of operating conditions.
LIBRA® 200MC offers a unique ease-of-use in a design that preserves both the angular and spatial distribution of the source to deliver an uncompromised monochromated spot for STEM mode and even energy illumination with improved temporal coherence in TEM mode with minimum loss of brightness.
No longer limited by the energy spread of the source, the corrected Omega energy filter com-bines with the monochromator to yield high resolution EELS spectroscopy enabling access to chemistry, structure and electronic state infor-mation at less than 0.14 nm spatial resolution on the