X-ray source

Source

Two insertion devices (IDs), an undulator and a wiggler, have been installed in a low straight section. The energy range 5 keV < E < 42 keV is covered by the different harmonics of the undulator. The wiggler is dedicated to energies lower than 5 keV since it will be used in the undulator regime which is reached when the gap is set to large values.

To avoid loss of low energy photons due to absorption by beryllium windows, the beamline can be windowless in normal operation mode. The insulation from the storage ring is assured by 2 differential pumping stages and valves. Nevertheless, two Be windows mounted inside valves can be inserted in the beam path in case the windowless operation mode is not necessary.

42 mm Undulator (38 periods) and 70 mm Wiggler on low  section
ID	Undulator	Wiggler
Magnet period:	42mm	70 mm
Critical energy c:	n/a	20.3 keV
K (at 20 mm gap):	2.0	5.5
Bmax field:	0.58 T	0.84 T
Source size:	0.134 x 0.024 mm2 (HxV) FWHM	0.260 x 0.110 mm2 (HxV) FWHM
Source divergence:	0.208 x 0.009 mrad2 (HxV) FWHM	0.800 x 0.400 mrad2 (HxV) FWHM
Total power emitted:	1.9 kW	5.3 kW

 

The undulator:

The minimun undulator gap is 16 mm. and the maximum is 200 mm. The graphs below give peak field, deflection parameter K and Energy of the fundamental as a funtion of gap values.

 

 

 

Example for a typical undulator setting of Gap=21.0 mm; E_fun

= 3.71 keV, Peaks are found at 11.204 (third harmonic) and 18.673 (fifth harmonic).

 

The undulator gap versus the harmonic energies is recorder in the data table

handbook placed also at the beamline. The undulator and the wiggler are controlled from the SPEC application OPTICS (motors u42 and w70 respectively).

 

The wiggler: The wiggler has a 70 mm of magnet period, with a critical energy of 20.3 keV. The maximum magnet field is of 0.84 T and the K (at 20 mm gap) is equal to 5.5. The wiggler is dedicated to energies lower than 5 keV since it will be used in the undulator regime which is reached when the gap is set to large values. Its minimum gap is 20.2 mm and the maximum is 300mm.