This paper focuses on the R&D performed for the development of permanent magnets-based dipoles-quadrupoles combined function magnets (PMQs) for the future NSLSII upgrade “complex bend” lattice (CB). This new lattice uses PMQs that provide both bending (dipole) and strong focusing (quadrupole) magnetic field on the electron beam. The permanent magnet (PM) technology is suitable for the high magnetic field strengths (0.5 T, 130 T/m) required for such combine function magnets. PM technology leads to a compact magnet design that is essential in realizing the complex bend lattice concept, as well as a passive magnet solution which does not require electrical power supply reducing power consumption by ~ 80% (from 1.7 MW to 0.3 MW for NSLS-II). Two PMQs magnets designs are under consideration: A hybrid design that use both PM and soft iron poles, and Halbach type that is a pure PM design. Both PMQs designs present challenges in achieving the specified magnetic field quality due to their higher sensitivity to errors (mechanical tolerances and PM properties). This paper presents cost-effective designs and prototypes results for hybrid and Halbach PMQs, addressing various technical challenges while meeting the field requirements of the complex bend lattice for the NSLS-II upgrade.

For the NSLS-II upgrade, a novel Complex Bend (CB) optics solution has been proposed to achieve near-diffraction-limited emittance. A key challenge in this design is the requirement for high-gradient quadrupoles (150 T/m) in a compact space. To demonstrate feasibility, a CB prototype was developed and tested using the NSLS-II linac beamline, scaling the beam energy to 100–200 MeV while maintaining strong focusing. The prototype utilized a 16-wedge symmetric Halbach permanent magnet design, achieving a gradient of 140 T/m within ultra-compact quadrupoles. The CB beamline was installed and commissioned in two phases, first as a strong periodic focusing element and later as a combined bending and focusing system. The beam commissioning results showed good agreement with theoretical models, confirming that the Complex Bend functions effectively as both a strong focusing and bending element by offsetting CB poles. This validates the strong focusing design of the Complex Bend for future synchrotron light source upgrades.