Speaker
Dr
Stephen Brooks
(Brookhaven National Laboratory)
Description
The original circular Halbach magnet design creates a strong pure multipole field from permanent magnet pieces without intervening iron. This design was modified for the CBETA 4-turn ERL, whose return loop includes combined-function (dipole+quadrupole) Halbach-derived magnets, plus a modular system of tuning shims to improve all 216 magnets' relative field accuracy to better than 10^-3. This talk also describes further modifications of the design enable a larger range of accelerator applications, such as open-midplane designs to allow synchrotron radiation to escape and magnets with an oval aperture to allow larger gradients, including in hadron therapy machines.
