HB2016 - Table of Session: THA6 (Working Group A

Paper

Title

Page

Typology of Space Charge Resonances

486

I. Hofmann
GSI, Darmstadt, Germany

The existence of structural space charge resonant effects in otherwise linear periodic focusing systems is well-known, but referred to in a variety of languages and contexts. We show here that for short bunched beams a ‘‘classification'' in two major groups is possible, e.g. parametric resonances or instabilities on the one hand and single particle type space charge resonances on the other hand. The primary feature of distinction is that for the former the driving space charge force initially exists on the noise level (rms or higher order mismatch) only and gets amplified parametrically, hence an entirely coherent response; for the latter the driving space charge multipole is part of the initial density profile and the coherent response is weak. In the extreme limit of KV beams only parametric resonances (instabilities) exist, and in principle in all orders. For waterbag or Gaussian distributions we find half-integer parametric resonances only up to fourth order, but evidence for single particle resonances in all orders up to tenth have been identified.

Slides THPM1X01 [3.094 MB]

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reference for this paper ※ DOI:10.18429/JACoW-HB2016-THPM1X01

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THPM2X01

Head-Tail Modes With Strong Space Charge: Theory and Simulations

A.V. Burov
Fermilab, Batavia, Illinois, USA

Low and medium energy hadron circular machines are operating at a condition of the strong space charge, i.e. with the space charge tune shift much higher than the synchrotron tune. Theory of transverse instabilities developed by the author for such cases was recently checked in multiparticle tracking with the Synergia code, and a good agreement was demonstrated both for the modes structure and Landau damping rates. Main aspects of the theory will be reminded and the comparison results be demonstrated.

Slides THPM2X01 [5.082 MB]

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THPM3X01

Head-Tail Instability and Landau Damping in Bunches with Space Charge

V. Kornilov, O. Boine-Frankenheim
GSI, Darmstadt, Germany

Landau damping of the head-tail modes defines the impedance budget and the intensity limits for ring machine performance. The long-known source of the damping has been the octupole nonlinearity. So far, only the damping of the rigid mode k=0 has been modeled using a 2D dispersion relation. Recently, the transverse space-charge field has been identified as an important damping component. Quantitive estimations of the resulting Landau damping is still an open question, especially for the higher order modes. There is also a long-standing debate how to describe the head-tail frequency shifts due to coherent and due to incoherent effect in the stability calculations. We present a model for the Landau damping in bunches based on the concept of the collective mode positioning with respect to the incoherent spectrum. Secondly, we discuss an accurate description for the head-tail eigenfrequency shifts. The predictions and the physical understanding are verified using particle tracking simulations, and in particular by the experimental results.

Slides THPM3X01 [1.745 MB]

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THPM4X01

Resonances and Envelope Instability in High Intensity Linear Accelerators

491

D. Jeon, J.-H. Jang, H. Jin
IBS, Daejeon, Republic of Korea

Funding: This work was supported by the Institute for Basic Science funded by the Ministry of Science, ICT and Future Planning (MSIP) and the NRF of Korea under Contract 2013M7A1A1075764.
Understanding of space charge effects has grown and recent studies have led to the findings of resonances of high intensity linear accelerators. Lately the sixth order resonance of high intensity linear accelerators was reported, along with the in-depth studies on the fourth order resonance and the envelope instability. Experiment studies on space charge resonances were reported. This paper reviews the resonances of high intensity linear accelerators such as the 4σ =360deg, and the 6σ =720deg resonances, along with the envelope instability.

Slides THPM4X01 [3.279 MB]

DOI •

reference for this paper ※ DOI:10.18429/JACoW-HB2016-THPM4X01

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Paper	Title	Page
THPM1X01	Typology of Space Charge Resonances	486
	I. Hofmann GSI, Darmstadt, Germany
	The existence of structural space charge resonant effects in otherwise linear periodic focusing systems is well-known, but referred to in a variety of languages and contexts. We show here that for short bunched beams a ‘‘classification'' in two major groups is possible, e.g. parametric resonances or instabilities on the one hand and single particle type space charge resonances on the other hand. The primary feature of distinction is that for the former the driving space charge force initially exists on the noise level (rms or higher order mismatch) only and gets amplified parametrically, hence an entirely coherent response; for the latter the driving space charge multipole is part of the initial density profile and the coherent response is weak. In the extreme limit of KV beams only parametric resonances (instabilities) exist, and in principle in all orders. For waterbag or Gaussian distributions we find half-integer parametric resonances only up to fourth order, but evidence for single particle resonances in all orders up to tenth have been identified.
	Slides THPM1X01 [3.094 MB]
DOI •	reference for this paper ※ DOI:10.18429/JACoW-HB2016-THPM1X01
Export •	reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPM2X01	Head-Tail Modes With Strong Space Charge: Theory and Simulations
	A.V. Burov Fermilab, Batavia, Illinois, USA
	Low and medium energy hadron circular machines are operating at a condition of the strong space charge, i.e. with the space charge tune shift much higher than the synchrotron tune. Theory of transverse instabilities developed by the author for such cases was recently checked in multiparticle tracking with the Synergia code, and a good agreement was demonstrated both for the modes structure and Landau damping rates. Main aspects of the theory will be reminded and the comparison results be demonstrated.
	Slides THPM2X01 [5.082 MB]
Export •	reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPM3X01	Head-Tail Instability and Landau Damping in Bunches with Space Charge
	V. Kornilov, O. Boine-Frankenheim GSI, Darmstadt, Germany
	Landau damping of the head-tail modes defines the impedance budget and the intensity limits for ring machine performance. The long-known source of the damping has been the octupole nonlinearity. So far, only the damping of the rigid mode k=0 has been modeled using a 2D dispersion relation. Recently, the transverse space-charge field has been identified as an important damping component. Quantitive estimations of the resulting Landau damping is still an open question, especially for the higher order modes. There is also a long-standing debate how to describe the head-tail frequency shifts due to coherent and due to incoherent effect in the stability calculations. We present a model for the Landau damping in bunches based on the concept of the collective mode positioning with respect to the incoherent spectrum. Secondly, we discuss an accurate description for the head-tail eigenfrequency shifts. The predictions and the physical understanding are verified using particle tracking simulations, and in particular by the experimental results.
	Slides THPM3X01 [1.745 MB]
Export •	reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPM4X01	Resonances and Envelope Instability in High Intensity Linear Accelerators	491
	D. Jeon, J.-H. Jang, H. Jin IBS, Daejeon, Republic of Korea
	Funding: This work was supported by the Institute for Basic Science funded by the Ministry of Science, ICT and Future Planning (MSIP) and the NRF of Korea under Contract 2013M7A1A1075764. Understanding of space charge effects has grown and recent studies have led to the findings of resonances of high intensity linear accelerators. Lately the sixth order resonance of high intensity linear accelerators was reported, along with the in-depth studies on the fourth order resonance and the envelope instability. Experiment studies on space charge resonances were reported. This paper reviews the resonances of high intensity linear accelerators such as the 4σ =360deg, and the 6σ =720deg resonances, along with the envelope instability.
	Slides THPM4X01 [3.279 MB]
DOI •	reference for this paper ※ DOI:10.18429/JACoW-HB2016-THPM4X01
Export •	reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)