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:
| M1 | Horizontally deflecting vertically collimating side-cooled Au-coated cylindrical mirror; angle of incidence is 2° |
| cPGM | Plane 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 slits | A pair of precision exit slits (spatially separated H-focus and V-focus) on each branch |
| Chopper | A 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) |
Chopper:
| Disc radius | 120 mm |
| Rotation speed | ≈ 0.8 kHz |
| Number of slits (two slit circles) | 12/120 |
| Slit width | 85 µm |
| Opening time | ≤ 300 ns |
| Repetition rates (two slit circles) | ≈ 10/100 kHz |
| Single bunch period time | 320 ns |
| Bunch length | ≈0.15 ns |
| Projected single bunch current | ≈20 mA |
| Projected impurity | <0.3% |