Most of the applications at I08-SXM are considered to require horizontal linear polarisation but there is a growing demand for circular polarisation as for example biomagnetic studies. Other polarisations as circular polarisation can also reduce the heat load on optical components. An Apple-II type insertion device with its flexibility in producing helical and planar fields is therefore an ideal choice. An HU53 undulator with 53mm allows accessing photon energies comfortably below the carbon K-edge, using photon energies up to 1200 eV in the first harmonic, and about 4000 eV using third, fifth or higher harmonics. Peak brightnesses are in the 500-2000 eV photon energy, required by the majority of experiments. Minimum gap of the insertion device is 16 mm.
|APPLE-II type Undulator: HU53, 4.5 m long|
|Linear (horizontal / vertical), Circular (left / right) polarization available; circular polarisation is limited to a 247-1200 eV photon energy range|
|Minimum Gap: 16 mm|
|Peak Field at Min. Gap: 0.82 T (H), 0.46 T (C), 0.54 T (V)|
The monochromator at I08-SXM is a collimated plane grating monochromator of SX700-type.
The resolving power of the I08-SXM is kept moderate for high-flux applications but is kept suffient for spectromicroscopy applications (XANES, XRF) in the entire photon energy range. The resolving power is dominated by the source size for lower photon energies but limited by the slope error of the plane mirror in the monochromator for higher photon energies. In overall, a resolving power of > 4000 is maintained over the entire photon energy range:
I08-SXM is among the few beamlines that can cover the entire photon energy up to 4200 eV by gratings. The c-PGM installed at I08-SXM hosts currently two laminar and one blazed grating but has a fourth substrate cartridge for a future installation of a multilayer grating optimised for high-flux applications at higher photon energies:
|PG4||for future reserve (ML)|
I08-SXM is unique in covering a broadest photon energy range from about 250-4200 eV covering K-edges of C, N, O, F, P, S, Cl, K, Ca as well as the L-edges of the first row transition metals and M edges of many rare-earth metals.
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