The undulator source of the MS beamline was installed at the beginning of 2011. It is a cryogenically cooled, permanent-magnet undulator with a 14-mm periodicity. The accessible range of energies spans 5 - 40 keV. The brilliance is approximately two orders of magnitude greater than that provided by the previous source, the W61 minigap wiggler. The brilliance increased manifold after the SLS2.0 ring upgrade. The latter entails a higher electron energy (2.7 GeV instead of 2.4 GeV) that has significantly enhanced the photon flux in the harder X-ray range (20-40 keV).
The natural angular divergence of the source was 0.032 mrad vertical by 0.16 mrad horizontal, it is expected to be smaller after the SLS2.0 ring upgrade. In monochromatic mode, the energy resolution is determined by the Si 111 monochromating crystals of the Cinel DCM to be 0.014%.
| Type | cryogenically cooled, permanent-magnet undulator (CPMU) |
|---|---|
| Length | 2.0 m |
| Period length | 14 mm |
| Minimum magnetic gap | 3.5 mm |
| Number of periods | 120 |
| Emitted power | 3 kW total. 214 W on optics |
U14 Undulator
Brilliance curves of some x-ray sources used at the SLS. Note in particular the difference between the curve for our previous wiggler source ("W61, practice") and for our new undulator ("U14").
The U14 uses novel Nd-Dy-Fe-B alloy magnets which maintain their remanence efficiently at approximately 150 K. The undulator operates around a deviation parameter K of approximately 1.5.
Front end
The front end safety system consists of two X beam position monitors (XBPM1 and XBPM2), followed by two beam-defining aperture (0.392 = 0.160 mrad^2 and 0.270 x 0.070 mrad^2), a synchrotron radiation shutter, a fast valve, a CVD diamond filter (120 um), and a CVD diamond window (80 um).
A. Cervellino, June 2025
