A new Electromagnetic/Permanent Magnets Helical Undulator (EMPHU), with a 65 mm magnetic period is under construction at SOLEIL [1] for providing a rapid switching at 5 Hz of the photon polarization required to perform dichroism experiments. The vertical field is produced by coils fed by a fast switching power supply, with a maximum current of 350 A and a polarity switching time shorter than 100 ms. The coils consist of copper sheets shaped by water jet cutting. 25 layers of copper are stacked together. The current flows in 16 layers and nine of them are cooled with thermal drain to a water piping. The current-regulated power supply, in-house developed [2], should be able to operate in the 4 quadrant with a 50 ppm current resolution over the full scale. It is complemented by eight power supplies for the correction coils required to provide dynamics correction of the field integrals. The horizontal field is generated by NdFeB permanent magnets. The designed vertical and horizontal first harmonic field values in the helical configuration reach 0.24 T at the minimum 14.7 mm gap. The magnetic design, the magnetic measurements (DC and AC) and the correction schemes are described.
The French 3 rd generation synchrotron light source, SOLEIL, was successfully commissioned in 2006. The Linac and the Booster are operational at their performance design. During the early phase of storage ring commissioning, essential designed parameters were reached very quickly even though the project incorporates some innovative techniques such as the use of a superconducting RF cavity, solid state RF amplifiers, NEG coating for all straight parts of the storage ring and new BPM electronics. Prior to the start of the commissioning, most of Insertion Device low gap vacuum vessels, including 10 mm inner vertical aperture vessels, were installed on the ring. The main results of one year commissioning and achieved performances are summarized in this paper.
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