Magnets for the Upgrade of the Swiss Light Source at the Paul Scherrer Institute-Design, Production, Measurement Challenges

To improve the performance of the Swiss Light Source (SLS) at the Paul Scherrer Institute (PSI), an upgrade is ongoing (referred to as SLS 2.0), 2021-2025, that includes the complete renewal of the storage ring, providing about 40 times lower emittance in user operation mode and therefore an enhanced brightness. SLS 2.0 imposes very strict requirements in terms of field quality and magnetic alignment on more than 1000 magnets, which are being produced and magnetically qualified. For the first time a light source will operate with a combination of three types of magnets: i) NdFeB based permanent magnets; ii) Electro-magnets; iii) 5-T Nb-Ti superconducting longitudinal gradient dipoles (installed in the second phase of the machine upgrade). This article provides an overview of the project's progress with respect to the design and production aspects of the magnets, the assembly and measurement strategy, and the challenges associated with series magnetic tests requiring 10
^-3
relative accuracy level.