Division of accelerators, cryogenics and magnetism

The Paul Scherrer Institute (PSI) is the largest research institute for natural and engineering sciences within Switzerland and runs an accelerator complex. It consists of four facilities: a High Intensity Proton Accelerator (HIPA), a third-generation synchrotron light source (SLS), a cancer treatment facility (PROSCAN) with a compact superconducting cyclotron and three gantries, and a free electron laser (SwissFEL).

PSI is currently preparing the upgrade of the Swiss Light Source (SLS-2) in order to meet the demand of the users for higher photon flux and brilliance. This project involves the exchange of the existing storage ring by a new one providing about 40-50 times lower emittance in user operation. The new lattice concept is based on longitudinal gradient bends (LGBs) and reverse bends to realize low emittance. In three positions the LGBs are replaced by superconducting super-bends to produce hard X-rays. The super-bends have a hyperbolic longitudinal field variation with a narrow peak (FWHM) of about 40-70 mm. The total magnet length should not exceed 400 mm with a field integral of 0.54 Tm. The peak field value at the beam position has to be 4 T. The magnet is made of a “C”-shaped iron core and two sets of Nb-Ti coils:  two inner racetrack coils and two outer solenoidal coils. To accommodate the new lattice in the previous tunnel (287 m long), all the magnets need to be very compact. To reduce the coil to coil distance, the superbend magnets will be conduction cooled using a liquid helium reservoir and a cryocooler as re-condensing unit.

The status of the development of the 4 T super-bend magnets together with the perspective of an upgrade to higher fields (above 6 T) will be the focus of the presentation. The development of the required infrastructure at PSI to build and test superconducting magnets and magnet components under operating conditions will also be introduced.