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@inproceedings{brooks:ipac2021-tuxc07,
author = {S.J. Brooks},
title = {{Modified Halbach Magnets for Emerging Accelerator Applications}},
booktitle = {Proc. IPAC'21},
pages = {1315--1318},
eid = {TUXC07},
language = {english},
keywords = {permanent-magnet, quadrupole, dipole, collider, electron},
venue = {Campinas, SP, Brazil},
series = {International Particle Accelerator Conference},
number = {12},
publisher = {JACoW Publishing, Geneva, Switzerland},
month = {08},
year = {2021},
issn = {2673-5490},
isbn = {978-3-95450-214-1},
doi = {10.18429/JACoW-IPAC2021-TUXC07},
url = {https://jacow.org/ipac2021/papers/tuxc07.pdf},
note = {https://doi.org/10.18429/JACoW-IPAC2021-TUXC07},
abstract = {{The original circular Halbach magnet design creates a strong pure multipole field from permanent magnet pieces without intervening iron. This design has been extended recently at 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 paper describes further modifications of the Halbach design enable a larger range of accelerator applications in the future: (1) open-midplane designs to allow synchrotron radiation in light sources and other high-energy electron rings, ERLs or RLAs to escape. (2) Quadrupole magnets with an oval aperture allow larger gradients than a circular aperture, provided the beam is more extended in one axis than the other, as usual for a quadrupole in a focussing system. These can be used in compact hadron therapy gantries. (3) New collider complexes often require multiple rings for acceleration or top-up, accumulation, collision and cooling. Multi-aperture permanent magnets are possible to cheaply and compactly build ring systems with several stable orbits separated by a few cm.}},
}