Regensburg 2013 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 89: Surface Dynamics II
O 89.4: Vortrag
Freitag, 15. März 2013, 11:15–11:30, H33
Space-Charge Interaction in Electron Momentum Microscopy — •Gerd Schönhense1, Katerina Medjanik1, Marieke de Loos2, and Bas van der Geer2 — 1Institut für Physik, Uni. Mainz, Germany — 2Pulsar Physics, Eindhoven, The Netherlands
Ultrahigh-brightness sources like (X)FELs, but also table-top higher harmonics sources offer fascinating experimental possibilities. Unfortunately, electron spectroscopic methods like photo- or Auger-electron spectroscopy at such sources are facing a dramatic loss in performance due to the space-charge problem. Coulomb interaction in the beam can induce prohibitively large energy broadenings ΔE of hundreds to thousands of eV. We have considered the space-charge effect for the special situation of a momentum microscope in the hard X-ray range, based on simulations with the General Particle Tracer (GPT) code. We find that momentum microscopy offers a pathway for a certain space-charge correction since the instrument detects the k||- distribution in a parallel-imaging microscope column. For XFEL applications in the hard X-ray range a strong immersion field of 5 MV/m (close to the limit of potential breakthrough) accelerates and widens the electron beam very rapidly, in order to reduce Coulomb repulsion. The correction makes use of the fact that the line of best-fit of the electron distribution in an energy-vs-radius plot appears tilted and can be used for a re-normalization of the measured kinetic energies. GPT calculations for different model distributions including the intense low-energy signal from the secondary cascade reveal chances of a possible space-charge correction approach. Project funded by BMBF (05K12UM2).