Asymmetric electrostatic dodecapole: compact bandpass filter with low aberrations for momentum microscopy

Autor: O. Tkach, S. Chernov, S. Babenkov, Y. Lytvynenko, O. Fedchenko, K. Medjanik, D. Vasilyev, A. Gloskowskii, C. Schlueter, H.-J. Elmers, G. Schönhense
Jazyk: angličtina
Rok vydání: 2024
Předmět:
Zdroj: Journal of Synchrotron Radiation, Vol 31, Iss 4, Pp 829-840 (2024)
Druh dokumentu: article
ISSN: 1600-5775
16005775
DOI: 10.1107/S1600577524003540
Popis: Imaging energy filters in photoelectron microscopes and momentum microscopes use spherical fields with deflection angles of 90°, 180° and even 2 × 180°. These instruments are optimized for high energy resolution, and exhibit image aberrations when operated in high transmission mode at medium energy resolution. Here, a new approach is presented for bandpass-filtered imaging in real or reciprocal space using an electrostatic dodecapole with an asymmetric electrode array. In addition to energy-dispersive beam deflection, this multipole allows aberration correction up to the third order. Here, its use is described as a bandpass prefilter in a time-of-flight momentum microscope at the hard X-ray beamline P22 of PETRA III. The entire instrument is housed in a straight vacuum tube because the deflection angle is only 4° and the beam displacement in the filter is only ∼8 mm. The multipole is framed by transfer lenses in the entrance and exit branches. Two sets of 16 different-sized entrance and exit apertures on piezomotor-driven mounts allow selection of the desired bandpass. For pass energies between 100 and 1400 eV and slit widths between 0.5 and 4 mm, the transmitted kinetic energy intervals are between 10 eV and a few hundred electronvolts (full width at half-maximum). The filter eliminates all higher or lower energy signals outside the selected bandpass, significantly improving the signal-to-background ratio in the time-of-flight analyzer.
Databáze: Directory of Open Access Journals
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