The optical scheme is based on the collimated plane-grating monochromator (cPGM), astigmatic intermediate focus and switchable refocusing mirrors.

The maximum beamline acceptance is 0.62 mrad x 1.36 mrad (h x v) and corresponds to full illumination of M1. Acceptance can be reduced using movable masks in the front end and/or baffles in front of the monochromator.

Main optical components:

M1Horizontally deflecting vertically collimating side-cooled Au-coated cylindrical mirror; angle of incidence is 2°
cPGMPlane grating monochromator (Zeiss SX700 modified to work with collimated light); up to three gratings (for now only 1200 l/mm and 1800 l/mm gratings installed); both M2 and gratings are Au-coated; plane M2 is side-cooled, gratings are back-cooled
M3 (x2)A pair of switchable horizontally-deflecting Au-coated toroidal mirrors focusing onto two exit slits each (foci in the horizontal and the vertical planes are at different distances from M3); angle of incidence is 1.95°
Exit slitsA pair of precision exit slits (spatially separated H-focus and V-focus) on each branch
ChopperA retractable chopper is planned to be installed in 2019 on the gas-phase branch for Time-Of-Flight experiments (see below)
M4 (x4)Horizontally deflecting refocusing Au-coated double-striped toroidal mirrors; each stripe can focus x-rays into a specific single point (in total four focal points allow for four different experimental setups); angle of incidence is 2°


Main beamline specifications:

Photon energy resolution ΔE, meV
(for V-slit of 10 µm)
2.4 @ 40 eV, 26 @ 400 eV, 140 @ 1500 eV
Flux at sample, ph/s
(@ E/ΔE = 10000)
0.5 – 3 x 1013 (40 – 200 eV), 1 – 5 x 1012 (200 – 900 eV), down to 2 x 1011 at 1500 eV
Beam size at sample Defocused (h x v): up to 2 x 1 mm
Focused (h x v): 65 x 10 µm (UHV XPS), 100 x 20 µm (open port), 80 x 15 µm (ToF), 130 x 25 µm (LDM XPS); further reduction in size is possible with baffles (at the cost of flux)



The LDM-branch will house a permanently installed chopper to be used in single-bunch mode to increase the interval between X-ray pulses, for e.g. time-of-flight measurements of electrons or ions. The design is based on that of Plogmaker et al. (Rev. Sci. Instrum. 83, 013115 (2012)), adapted to the specifics of the MAX IV 1.5 GeV ring and the FlexPES beamline. When not in operation the chopper can be moved out of the beam path without breaking vacuum.

Disc radius120 mm
Rotation speed ≈ 0.8 kHz
Number of slits (two slit circles)12/120
Slit width85 µm
Opening time≤ 300 ns
Repetition rates (two slit circles)≈ 10/100 kHz
Single bunch period time320 ns
Bunch length≈0.15 ns
Projected single bunch current≈20 mA
Projected impurity<0.3%