The micro spot size on the second branch has been first measured and calibrated using an imaging setup consisting of a YAG crystal, a microscope objective and a visible CCD camera. At 140 ev, the total demagnication factor of the beamline for this branch is 110 and 70 for the horizontal and the vertical direction respectively. The best beamspot measured has a FWHM of 7.2x3.5 μm (HxV). Note that due to grazing incidence of the light onto the sample in the PEEM microscope, the effective beamspot size is 7x10 μm. The beamspot can be enlarged by a factor 2, without noticing a drastic change in the shape. Above that, the beamspot starts to be very inhomogeneous and affected by striations. A new optical setup has been developed and tested in order to overcome these defficulties (ZoomX). It allows to vary homogeneously the beamspot up to 30 μm. It is planned that the new setup will be later installed on the second branch, in order to allow working with larger microscope field of view in X-PEEM mode.
Image of the photon beam spot on the second branchline.
Intensity profiles along the beam spot.
Left: horizontal; Right: vertical.
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