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The SESAM instrument during the setup | | SESAM Instrument
The SESAM- (Sub-Electronvolt-Sub-Ångstrom-Microscope) instrument targets at highest performance for energy filtering-applications (resolution better than 0,2 eV, very large transmitted angles for filtered diffraction experiments) and is therefore equipped with the so-called Mandoline-Filter. The Mandoline incorporates a total of 9 magnetic multiple elements that will provide complete correction for all aberrations up to the 3. order. This most sophisticated imaging energy filter ever been realised now offers unrivalled performance capabilities regarding dispersion (6,2 µm/eV) and transmissivity.
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The UHRTEM instrument during the setup | | UHRTEM Instrument
The UHRTEM (Ultra High Resolution TEM) instrument targets at highest resolution in imaging-mode. Therefore an electron optical correction module is integrated, compensating the spherical aberration (coefficient Cs) of the objective lens and thus improving the resolution limit to below 0,1 nm. The so called Cs-corrector is an ingenious optical set-up consisting of 2 hexapole-lenses and several transfer-lenses and is adapted into the column directly beneath our newly developed objective-lens. Furthermore the UHRTEM is equipped with the new corrected 90° OMEGA Filter - the standard Filter for the LIBRA® 200kV series – and therefore also here highly sophisticated energy-filtered TEM-applications are possible.
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 | | 200kV Field emission emitter
High resolution TEM and STEM (Scanning Transmission Electron Microscopy) performance requires a high brightness of the electron source. This is provided by a Field Emission point source, giving high spatial coherence for optimum information transfer in TEM and realisation of minimum spot sizes for superior STEM resolution. The Schottky emitter poses an optimum trade off between intensity, bright-ness and energy spread, thus enabling very good energy resolution at the high intensity required for maximum spectrum SNR ratio. The Field emission module incorporates a five stage acceleration sys-tem and is designed for optional integration of an electrostatic OMEGA-type monochromator. Together with the 3 lens condenser optics the unique Koehler illumination system for TEM is provides superior definition of the illumination conditions like independent control of brightness and illuminated area at strictly parallel beam incidence.
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| | Monochromator
The FEG of both SESAM and UHRTEM instruments is equipped with a Monochromator. This optical component acts as an energy filter for the electrons emitted by the source and enables to reduce the width of the electron energy distribution in the beam from the FEG-inherent value of 0,7 eV down to values below 0,2 eV. Due to his compact design the monochromator fits completely into the FEG-housing and in no way influences the standard TEM-performance when the filter function is switched off. With monochromatic illumination of the sample under investigation, EELS-Analytics (Electron Energy Loss Spectroscopy) with a resolution below 0,2 eV becomes possible. Moreover such a mono-chromatic electron-beam is a prerequisite to increase the resolution of a transmission electron micro-scope in imaging or STEM-mode to values better than 1 Ångstrom (0,1nm) by incorporating electron optical aberration correctors.
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Viewing chamber and Mandoline filter housing of the new 300 mm column for the SESAM | | New 300mm TEM-column
In order to obtain the required mechanical stability and to gain space for further improvements of magnetic lenses and other electron optical components the electron optical column diameter has been increased to 300mm. The newly constructed 300 mm column as well as the new Field Emission Gun (FEG) and the corrected 90° Omega Filter consequently are integrated into the innovative newly launched LIBRA® 200kV series.
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| | New corrected OMEGA filter
The well established OMEGA-type In-column filter technology was further optimised in order to provide its Field Emission instruments with a filter of increased performance properties. The new corrected OMEGA filter comprises 7 magnetic multipole elements, giving full second-order aberration correction and resulting in higher dispersion and increased transmissivity. Thus electron energy filtering applica-tions with extended isochromatic fields of view, small energy slit widths and transfer of large acceptance angles (e.g. CBED) are straightforward available. This is achieved without restrictions for all no filtered applications or any need for complicated customer alignments, due to the highly robust factory prealignment.
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Highly stable frame supporting the hanging TEM column | | New column support system
The optical performance of SESAM and UHRTEM can in only is achieved, if extremely stable operation conditions are provided for the electron-optical column. Besides an optimised installation in an extraordinarily disturbance-free laboratory, the sensitivity of the column against any transmission of external mechanical excitations – e.g. caused by floor vibrations or acoustics – has to be minimised. To achieve this, new „hanging-column concept“ was developed. The TEM column is supported like a pendulum in a highly stable frame, which has been optimised for maximum stiffness while providing the necessary accessibility to the column. This innovative concept leads to a completely new appearance for the SESAM and the UHRTEM and we are convinced that it will be trendsetting for future „State-of-the-Art“ Transmission electron microscopes.
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