| Paper | Title | Page |
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THBC2 |
Mitigation of 4th Order Resonance and Envelope Instability by Beam Angular Momentum | |
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| For modern high-intensity linear accelerators, the well-known envelope instability and recently reported fourth-order particle resonance impose a fundamental operational limit: zero-current phase advance (sig0)<90deg. In particular, it has been discovered that the fourth-order particle resonance is always excited and manifested predominantly over the envelope instability along the drift-tube linac when sig0>90deg and sig<90deg. In this study, we present a novel method to mitigate the space-charge driven fourth-order resonance by introducing a new concept of ‘spinning beam’. Motivated by classical mechanics on the stability of spinning flying objects, ‘spinning beam’ has non-zero average canonical angular momentum under axisymmetric system. From the analytical and numerical simulation studies, we found that spinning beams have an intrinsic characteristic that can suppress the impact of the fourth-order resonance on emittance growth and the following envelope instability. Unlike other approaches to suppress the coherent instabilities, we have demonstrated beam spinning as a possible control knob for mitigating the fourth-order resonance to surpass the linac operational limit. | ||
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