The MAXPEEM beamline (top figure) consists of an elliptically polarizing undulator as a light source (EPU 58) and a collimated plane grating monochromator (SX-700) with corresponding focusing and re-focussing optics (ellipsoidal M4 mirror), and ACLEEM microscope as the end station. The spot size at the sample position (bottom figure) in the XPEEM branch is around 18(h) x 15(v) µm² (with a 0.15 exit slit opening vertically and horizontally) and can be reduced down to approximately 15(h) x 4(v) µm² or increased by defocussing (up to 50 x 50 µm²). More details are provided in the table below.

A diagram depicting the optical schematics of MAXPEEM

Beamline properties

X-ray source (IVU)Elliptical undulator EPU-58, 58 mm period, 2.6 m magnetic length
variable polarization
Energy range30-1500 eV using 3ʳᵈ-11ᵗʰ harmonic of the EPU
MonochromatorSX-700 with three interchangeable gratings
Energy bandwidthΔE/E 2x10⁻⁴
Focusing opticsM3 - Toroidal mirror focusing the light both vertically and horizontally onto the exit slit
Refocusing opticsM4 - Ellipsoidal mirror focusing vertically and horizontally onto the sample
Beam size at sample (37 m)16 x 16 μm² (FWHM, horizontal x vertical), larger beam (up to 50 μm) by defocusing (M4 - mirror yaw rotation). A smaller beam (down to 5 μm) is envisaged for high-resolution measurements by closing the exit slit.
Flux at sample (focused) at 100 eV5x10¹³ ph/s
Experiment set-upLow Energy Electron microscope (LEEM III, Elmitec) with aberration corrector

It will be possible to build another branch into this beamline by inserting an additional focusing mirror into the beam path. The other branch will have its own permanent exit slit and refocusing optics designed for the special needs of that particular end station.