Principle
- Two concentric Halbach rings (dipole, quadrupole, etc)
- Individually rotatable
- Synchronized rotation of two n-pole fields can set both magnitude and direction
- Minimal stray field outside the rings
- Inherent magnetic field quality measurement (by rotating the rings)
Features
- Can be mounted/unmounted around existing vacuum pipe
→ compatible with bake-out - Repositioning with high accuracy
- Field quality measurement at any time
- Play-free driving mechanism
- Convertible between dipole/quadrupole/etc by replacing one component
- Zero energy consumption in steady state
- Tunability: ~ 0.01T
- Mitigation of temperature-dependent remanent flux density: by tuning
- Br degradation due to radiation:
– By tuning, if homogeneous
– By reshuffling the magnets if non-homogeneous + tuning - Can be stacked with no gap (current design: 30 mm extra length w.r.t. magnets)
- Different lengths easily achievable
Magnetic field
Practical limits:
- Dipole: up to 1.5 T
- Quadrupole: up to 125 T/m
References
Tunable, unmountable, permanent-magnet-based accelerator
magnet, Phys. Rev. Accel. Beams 28, 072401
A prototype was procured and tested by CERN (European Laboratory for Particle Physics) for evaluation.
