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RIS citation export for TUXA06: Loss of Transverse Landau Damping by Diffusion in High-Energy Hadron Colliders

TY  - CONF
AU  - Furuseth, S.V.
AU  - Buffat, X.
ED  - Liu, Lin
ED  - Byrd, John M.
ED  - Neuenschwander, Regis T.
ED  - Picoreti, Renan
ED  - Schaa, Volker R. W.
TI  - Loss of Transverse Landau Damping by Diffusion in High-Energy Hadron Colliders
J2  - Proc. of IPAC2021, Campinas, SP, Brazil, 24-28 May 2021
CY  - Campinas, SP, Brazil
T2  - International Particle Accelerator Conference
T3  - 12
LA  - english
AB  - Circular hadron colliders rely on Landau damping to stabilize the beams. Landau damping depends strongly on the bunch distribution, which is often assumed to be Gaussian in the transverse planes. In this paper, we introduce and explain an instability mechanism observed in the LHC, where Landau damping is eventually lost due to a diffusion that modifies the transverse bunch distribution. The mechanism is caused by a wide-spectrum noise that excites the transverse motion of the beam, which consequently produces wakefields that drive a narrow-spectrum diffusion. It is shown that this diffusion efficiently lowers the stability diagram at the frequency of the least stable coherent mode, leading to a loss of Landau damping after a latency. A semi-analytical model agrees with measurements in dedicated latency experiments performed in the LHC. This instability mechanism explains the need for a stability margin in octupole current in the LHC, relative to the amount needed to stabilize a Gaussian beam. We detail the impact of this mechanism and possible mitigations for the LHC and HL-LHC.
PB  - JACoW Publishing
CP  - Geneva, Switzerland
SP  - 1286
EP  - 1289
KW  - wakefield
KW  - damping
KW  - hadron
KW  - collider
KW  - feedback
DA  - 2021/08
PY  - 2021
SN  - 2673-5490
SN  - 978-3-95450-214-1
DO  - doi:10.18429/JACoW-IPAC2021-TUXA06
UR  - https://jacow.org/ipac2021/papers/tuxa06.pdf
ER  -