Use of astigmatic re-focusing at HP-XPS end-station

• In this paper we present the refocusing optics for the new high pressure photoelectron spectroscopy (HP-XPS) branch line at MAX-lab, based on a plane grating monochromator with vertically collimated beam. For the HP-XPS instrument, the required spot size is dictated by the small geometric acceptance of the HP-XPS electron energy analyzer. Whereas a pair of bendable mirrors in a KB configuration has some advantages as refocusing elements, we have studied whether similar performance can be achieved with a single non-bendable mirror. In this solution, however, the need for strong horizontal magnification results in a strong vertical magnification and into a very asymmetric image, the height being just a fraction of the width. We have studied through an analytical geometrical model and ray tracing simulations the use of astigmatism to increase the vertical beam size up to the geometric acceptance of the detector. As a result the vertical beam size at sample plane is mostly determined by the photon angular distribution and is not dependent on the exit slit aperture size. In addition the vertical beam size can be controlled by the grating c(ff) parameter, making possible to adjust the photon density and minimize sample damage by the radiation.

Subject headings

NATURVETENSKAP  -- Fysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences (hsv//eng)

NATURVETENSKAP  -- Fysik -- Atom- och molekylfysik och optik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Atom and Molecular Physics and Optics (hsv//eng)

Publication and Content Type

kon (subject category)

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