First pre-series sextupole for the SESAME storage ring
First SESAME sextupole pre-series undergoing magnetic measurements in the ISR tunnel at CERN. The electric and hydraulic connections are in test configuration. Image credit: CERN
In November 2013, CERN has completed the first assembly of a pre-series sextupole for the SESAME storage ring, within the CESSAMag European project. This is indeed the first magnet for the new synchrotron light source in construction in Jordan.
The magnetic design of the sextupole has been finalized at CERN on the basis of the initial proposal of SESAME. The compact magnet is actually multi-purpose, incorporating – on top of the main sextupolar field – three correctors, namely the horizontal / vertical dipole and a skew quadrupole. Since the aperture (75 mm diameter) is comparable to the length (iron length 100 mm), the optimization of the pole tip geometry was carried out directly in 3D. A peculiar feature from the magnetic viewpoint is the unconventional choice of avoiding any end pole chamfering, while still minimizing the first allowed harmonic. This was obtained by introducing a careful bias in the 2D design, that cancels out in 3D due to edge effects. This simplifies the manufacture without compromising on the field quality. Indeed a magnetic measurement on the pre-series confirmed the simulations, with a first allowed harmonics of 0.4∙10-4 at a reference radius of 24 mm.
This pre-series sextupole validates the design and opens the way for the 64 units needed for the SESAME storage ring. Contracts for the main components are on-going in Europe, whereas for the final assembly and testing options in Cyprus and Pakistan are currently being finalized.
