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Beamlines

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Beamline design

The source of synchrotron light at the DEMETER beamline is an elliptical undulator (EPU - Eliptically Polarized Undulator), located in straight section of the storage ring. It provides soft X-rays in a wide energy range of 100-2000 eV. A fully motorized undulator motion control system allows for full polarization control, providing photon beam at any polarization: linear (in any direction), circular (right- and left-handed) and elliptical.  

The first optical element just behind undulator is collimating (toroidal) mirror that minimize the astigmatism of a photon beam and enables focus it on a point.

fig. Beamline design

After toroidal mirror, DEMETER beamline has a variable angle plane grating monochromator. A plane mirror and three diffraction gratings are used to cover the full energy range of 100 to 2000 eV. After the grating chamber, there are two toroidal mirrors which focus the beam onto the exit slit of the PEEM and STXM branch. The energy resolution of the monochromator is around 8000 at an exit slit of 20 um and Cff = 2.25

Each branch is equipped with exit slits (vertical and horizontal) that enables to change the beam size. The PEEM end-stations is additionally equipped with a Kirkpatrick-Baez refocusing mirror pair focusing the beam down to 12 x 36 µm2 (footprint on the sample).

Beamline parameters:

Source

EPU (undulator)

Available energy range

100–2000 eV (horizontal polarization)

Resolution

E/dE=3 x 103–1,5 x 104

Beam spot size at sample (H x V)

0,2(v) x 0,8(h) mm2

Photon flux at sample

~1012ph/s/0,1% bw

Polarization

circular left- and right-handed, linear horizontal and vertical

Available techniques

XMCD, XMLD, PEEM, XPS, STXM