Design of an rf quadrupole for Landau damping

Papke, K.

doi:10.1103/physrevaccelbeams.20.082001

Cited by 3 publications

(8 citation statements)

References 14 publications

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“…Recently, the design and working principle of a radio frequency (rf) quadrupole has been published, including a numerical analysis of its stabilizing effect [8][9][10]. Unlike Landau octupoles, an rf quadrupole generates a betatron tune spread depending on the longitudinal rather than the transverse actions.…”

Section: Introductionmentioning

confidence: 99%

Experimental stabilization of transverse collective instabilities in the LHC with second order chromaticity

Schenk

Buffat

Carver

et al. 2018

Phys. Rev. Accel. Beams

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This paper discusses measurements on the stabilization of single bunches with second order chromaticity (Q 00) in the Large Hadron Collider (LHC) at CERN. Q 00 introduces an incoherent betatron tune spread which can produce Landau damping of transverse instabilities. Although the resulting stabilizing effect is similar to that provided by Landau octupoles, the underlying beam dynamics are different. Since the tune spread from Q 00 is based on the longitudinal rather than the transverse action of the particles, it will not be affected by the smaller transverse emittance beams of future machines, such as the High Luminosity LHC or the Future Circular Collider, and may hence provide more efficient Landau damping than magnetic octupoles. This study serves as a proof-of-principle experiment to demonstrate Landau damping from detuning with longitudinal action by means of Q 00 in a carefully prepared and well-understood accelerator environment. The agreement between measurements and PyHEADTAIL tracking simulations shows that Q 00 indeed contributes to the beam stability, that the numerical model of the LHC is accurate, and that the involved beam dynamics mechanisms are understood from both the single-and multiparticle effects points of view. The results also serve as a first experimental validation of the recently proposed radio frequency quadrupole for Landau damping.

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Section: Introductionmentioning

confidence: 99%

Experimental stabilization of transverse collective instabilities in the LHC with second order chromaticity

Schenk

Buffat

Carver

et al. 2018

Phys. Rev. Accel. Beams

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“…This section gives a brief overview on the main aspects of an rf quadrupole device. It discusses first two cavity designs explaining the main differences between the two geometries as well as the relevant parameters that have been optimized [8,12]. The basic working principle of the device is then explained by deriving an analytical formula for the incoherent betatron detuning that it generates.…”

Section: Radio Frequency Quadrupolementioning

confidence: 99%

“…First, the bunches of the HL-LHC and FCC-hh (hadron-hadron) are foreseen to have a length of the order of σ z ≈ 0.1 m [1,2]. An rf quadrupole operating at 800 MHz has an rf wave length that matches the bunch length and provides the best beam stabilizing efficiency according to numerical simulations [12]. Second, for practical reasons, the rf quadrupole frequency is limited to harmonics of the main rf system (400 MHz) of the aforementioned machines.…”

Section: A Device Descriptionmentioning

confidence: 99%

“…In [12], two different cavity designs for a superconducting rf quadrupole have been proposed and thoroughly optimized primarily for quadrupolar field strength, but also in terms of transverse and longitudinal beam coupling impedance, and peak electric E pk and magnetic B pk surface fields. While the first type is an elliptical cavity operating in a transverse magnetic (TM) quadrupolar mode, the second one is a four-vane cavity operating in a transverse electric (TE) quadrupolar mode.…”

Section: A Device Descriptionmentioning

confidence: 99%

“…2. The main advantages of the four-vane cavity compared to an elliptical one are [12]: (i) the quadrupolar field strength per cavity is up to two to five times larger than that of the elliptical one, given that the aperture has a radius <50 mm, and (ii) the four-vane cavity is more compact and requires hence smaller cryomodules and less cooling power. As a result, the number of cavities can be reduced and therewith the overall impedance and cost of the system.…”

Section: A Device Descriptionmentioning

confidence: 99%

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Analysis of transverse beam stabilization with radio frequency quadrupoles

Schenk

Papke

2017

Phys. Rev. Accel. Beams

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A radio frequency (rf) quadrupole has been considered as a potential alternative device for Landau damping in circular hadron colliders. The objective of this study is to benchmark and confirm its stabilizing effect predicted by stability diagram theory by means of numerical tracking simulations. To that end, two complementary models of the device are implemented in PyHEADTAIL, a 6D macroparticle tracking code designed to study the formation and mitigation of collective instabilities. The rf quadrupole model is applied to a slow head-tail instability observed experimentally in the Large Hadron Collider to show that such a device can in principle provide beam stability similarly to magnetic octupoles. Thereafter, alternative usage schemes of rf quadrupoles also in combination with magnetic octupoles are proposed, discussed, and benchmarked with simulations.

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