Permanent magnet-based dipole-quadrupole magnet for SPring-8-II

In recent years, permanent magnet (PM) based multi-pole magnets have become an increasing concern as a replacement for conventional electro-magnets for light sources. The PMs are possible to save both energy and costs for operating and construction the facilities due to the absence of a power supply and cooling system. They have other advantages such as less space without magnetic coils and fewer failures than the conventional electro-magnets. PMs have specific issues, such as the adjustability of the magnetic field, demagnetization, and temperature dependence. Solutions to these issues were already confirmed with dipole structures for SPring-8-II, a major upgrade project of SPring-8 to the fourth generation. We have extended the knowledge and schemes to a dipole-quadrupole combined-function magnet (DQM) that comes in a quadrupole structure. The DQM is readily splittable into an upper and lower half for installation of a vacuum chamber. The reproducibility of the field gradient with half-splitting was less than 0.1%, which is within the required value. We report on the design and trial-manufacture of the PM based DQM.