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Differential pumping unit for windowless coupling of laser beams to ultra high vacuum

: Tschernajew, M.; Gierschke, P.; Lin, H.; Hilbert, V.; Kurdal, J.; Stancalie, A.; Limpert, J.; Rothhardt, J.


Vacuum 178 (2020), Art. 109443
ISSN: 0042-207X
Fraunhofer IOF ()
coupling; differential; Gradient; Laser; UHV

Current laser technology enables table-top high flux XUV sources with photon energies from several tens to several hundreds of eV via high harmonic generation in noble gases. Here we present a compact versatile coupling unit to establish windowless, and thus lossless coupling of such light sources to ultra high vacuum (UHV). The particular coupling unit has been developed to couple a XUV laser source to a heavy ion storage ring. Three-stage differential pumping allows to reduce the input pressure of ~10−6 mbar down to the 10−12 mbar range at the output. The unit particularly reduces the partial pressure of argon, which is used to generate the XUV radiation, by 6 orders of magnitude. Measurements of the pressure distribution inside the different chambers agree well with theoretical simulations. In principle, this unit can also serve for other purposes, where a windowless vacuum coupling is needed, with a transition from High Vacuum (HV) levels to deep UHV, such as coupling to cryogenically cooled detectors, ion traps or to photoelectron emission spectroscopy experiments.