Beam Down in the SALVE-III/TITAN Microscope
July 24, 2015 - This Friday, one milestone of the SALVE III project was reached: the SALVE-III/TITAN has been handled over from FEI Electron Optics to CEOS company, after the beam traveled down the column with the SALVE++1 Cc/Cs corrector installed.
History: The SALVE-III/FEI column has been built-up as an uncorrected tool with the special PICO frame on the factory floor and is equipped with a XFEG/Monochromator gun, STEM unit, piezo stage, Ceta camera and with the special GIF Quantum filter of Gatan. It is aligned for 20 kV, 30 kV, 40 kV, 60 kV, and 80 kV. During the alignment of these voltages, extra focus was on screening of potential charging at low voltages, although it was not observed during the low voltage tests. The retrofitting of the SALVE++ Cc/Cs-corrector to the FEI Titan platform has been completed in May 2015. Since the electric stability of the corrector's electromagnetic multipoles is extremely important for the final resolution of the corrected TEM, the corresponding electrostatic quadrupoles have carefully been tested for electric stability and electric strength during several assembly steps. The interfacing between corrector and microscope with respect to mechanics, vacuum, and magnetic parts has been realized in close collaboration between CEOS and FEI.
On June 8th the SALVE-TITAN was delivered from FEI in Eindhoven to CEOS in Heidelberg. Immediately after delivery the build-up of the instrument was started and the Cc corrector of CEOS and special parts provided by FEI were incorporated. Furthermore FEI demonstrated that the monochromator, which is part of the SALVE instrument, is in best operation for HR-TEM work and that it can produce a high brightness.
Now as a next step, the optics will be adjusted. The team is waiting for the message: Beam down with corrector! Then the corrector will be further evaluated and finally, at the beginning of next year, the achievement of the required specifications will be demonstrated. Since the image spread of the base instrument is below the required limit at all accelerating voltages, the total image spread of corrector + base instrument should be sufficiently small to enable the predicted resolution of the final SALVE microscope. The technical task from the side of Ulm University is to construct the new SALVE building. The start will be in September this year, finished at the end of 2016.
1: Plus plus stand for the improved Cc/Cs corrector after optimizing the ray paths to reduce the image spread caused by Johnson noise [1].
Uhlemann, S., Müller, H., Hartel, P., Zach, J., & Haider, M. (2013). Thermal magnetic field noise limits resolution in transmission electron microscopy. Physical Review Letters, 111: 046101, doi: 10.1103/PhysRevLett.111.046101