HB2014 - List of Authors (Boine-Frankenheim, O.)

Paper

Title

Page

Transverse Decoherence of Ion Bunches with Space Charge and Feedback System

45

I. Karpov
TEMF, TU Darmstadt, Darmstadt, Germany
O. Boine-Frankenheim, V. Kornilov
GSI, Darmstadt, Germany

The transverse decoherence of the bunch signal after an initial bunch displacement is an important process in synchrotrons and storage rings. It can be useful, for the diagnostic purposes, or undesirable. Collective bunch oscillations can appear after the bunch-to-bucket transfer between synchrotrons and can lead to the emittance blow-up. In order to preserve the beam quality and to control the emittance blow-up, transverse feedback systems (TFS) are used. But, TFS operation can also lead to emittance blow-up due to imperfections (noise, bandwidth limitation, time delay errors), which also depends on the TFS settings. In heavy ion and proton beams, like in SIS100 synchrotron of the FAIR project, transverse space charge strongly modify decoherence. The resulting transverse bunch decoherence and beam blow-up is due to a combination of the lattice settings (like chromaticity), nonlinearities (residual or imposed by octupole magnets), space-charge, and the TFS. We study these effects using particle tracking simulations with the objective of correct combinations for a controlled beam blow-up.

WEO1LR02

Thresholds of the Head-Tail Instability in Bunches with Space Charge

240

V. Kornilov, O. Boine-Frankenheim
GSI, Darmstadt, Germany
D.J. Adams, B. Jones, B.G. Pine, C.M. Warsop, R.E. Williamson
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom

Recent experimental studies of the unstable head-tail modes in the ISIS synchrotron (RAL, UK) provided intriguing findings about the intensity thresholds for the instability/stability along the acceleration ramp for different bunch parameters in single-rf and dual-rf operation. We explain the role of space-charge and the related Landau damping using particle tracking simulations and an airbag-bunch theory, and relate the observations to the classical single-rf, no space-charge theories in order to identify the driving impedances.

Slides WEO1LR02 [3.203 MB]

WEO4LR03

Noise and Entropy in Non-Equipartitioned Particle Beams

309

I. Hofmann, O. Boine-Frankenheim
GSI, Darmstadt, Germany
O. Boine-Frankenheim
TEMF, TU Darmstadt, Darmstadt, Germany

The numerical noise generated in particle-in-cell simulation of 3D high intensity bunched beams is studied with the TRACEWIN code and compared with the analytical entropy model by Struckmeier. In this model the logarithm of the six-dimensional rms emittance is shown to qualify as rms-based entropy. We confirm the dependence of this growth on the bunch temperature anisotropy as predicted by Struckmeier, but also find modifications not predicted by theory. Our findings are applicable in particular to high current linac simulation, where they can help to estimate noise effects and find an effective balance between the number of simulation particles and the grid resolution. In principle, they can also be generalized to bunches in circular machines.

Slides WEO4LR03 [2.946 MB]

WEO4LR03

Noise and Entropy in Non-Equipartitioned Particle Beams

309

I. Hofmann, O. Boine-Frankenheim
GSI, Darmstadt, Germany
O. Boine-Frankenheim
TEMF, TU Darmstadt, Darmstadt, Germany

The numerical noise generated in particle-in-cell simulation of 3D high intensity bunched beams is studied with the TRACEWIN code and compared with the analytical entropy model by Struckmeier. In this model the logarithm of the six-dimensional rms emittance is shown to qualify as rms-based entropy. We confirm the dependence of this growth on the bunch temperature anisotropy as predicted by Struckmeier, but also find modifications not predicted by theory. Our findings are applicable in particular to high current linac simulation, where they can help to estimate noise effects and find an effective balance between the number of simulation particles and the grid resolution. In principle, they can also be generalized to bunches in circular machines.

Slides WEO4LR03 [2.946 MB]

Paper	Title	Page
MOPAB11	Transverse Decoherence of Ion Bunches with Space Charge and Feedback System	45
	I. Karpov TEMF, TU Darmstadt, Darmstadt, Germany O. Boine-Frankenheim, V. Kornilov GSI, Darmstadt, Germany
	The transverse decoherence of the bunch signal after an initial bunch displacement is an important process in synchrotrons and storage rings. It can be useful, for the diagnostic purposes, or undesirable. Collective bunch oscillations can appear after the bunch-to-bucket transfer between synchrotrons and can lead to the emittance blow-up. In order to preserve the beam quality and to control the emittance blow-up, transverse feedback systems (TFS) are used. But, TFS operation can also lead to emittance blow-up due to imperfections (noise, bandwidth limitation, time delay errors), which also depends on the TFS settings. In heavy ion and proton beams, like in SIS100 synchrotron of the FAIR project, transverse space charge strongly modify decoherence. The resulting transverse bunch decoherence and beam blow-up is due to a combination of the lattice settings (like chromaticity), nonlinearities (residual or imposed by octupole magnets), space-charge, and the TFS. We study these effects using particle tracking simulations with the objective of correct combinations for a controlled beam blow-up.

WEO1LR02	Thresholds of the Head-Tail Instability in Bunches with Space Charge	240
	V. Kornilov, O. Boine-Frankenheim GSI, Darmstadt, Germany D.J. Adams, B. Jones, B.G. Pine, C.M. Warsop, R.E. Williamson STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
	Recent experimental studies of the unstable head-tail modes in the ISIS synchrotron (RAL, UK) provided intriguing findings about the intensity thresholds for the instability/stability along the acceleration ramp for different bunch parameters in single-rf and dual-rf operation. We explain the role of space-charge and the related Landau damping using particle tracking simulations and an airbag-bunch theory, and relate the observations to the classical single-rf, no space-charge theories in order to identify the driving impedances.
	Slides WEO1LR02 [3.203 MB]

WEO4LR03	Noise and Entropy in Non-Equipartitioned Particle Beams	309
	I. Hofmann, O. Boine-Frankenheim GSI, Darmstadt, Germany O. Boine-Frankenheim TEMF, TU Darmstadt, Darmstadt, Germany
	The numerical noise generated in particle-in-cell simulation of 3D high intensity bunched beams is studied with the TRACEWIN code and compared with the analytical entropy model by Struckmeier. In this model the logarithm of the six-dimensional rms emittance is shown to qualify as rms-based entropy. We confirm the dependence of this growth on the bunch temperature anisotropy as predicted by Struckmeier, but also find modifications not predicted by theory. Our findings are applicable in particular to high current linac simulation, where they can help to estimate noise effects and find an effective balance between the number of simulation particles and the grid resolution. In principle, they can also be generalized to bunches in circular machines.
	Slides WEO4LR03 [2.946 MB]

WEO4LR03	Noise and Entropy in Non-Equipartitioned Particle Beams	309
	I. Hofmann, O. Boine-Frankenheim GSI, Darmstadt, Germany O. Boine-Frankenheim TEMF, TU Darmstadt, Darmstadt, Germany
	The numerical noise generated in particle-in-cell simulation of 3D high intensity bunched beams is studied with the TRACEWIN code and compared with the analytical entropy model by Struckmeier. In this model the logarithm of the six-dimensional rms emittance is shown to qualify as rms-based entropy. We confirm the dependence of this growth on the bunch temperature anisotropy as predicted by Struckmeier, but also find modifications not predicted by theory. Our findings are applicable in particular to high current linac simulation, where they can help to estimate noise effects and find an effective balance between the number of simulation particles and the grid resolution. In principle, they can also be generalized to bunches in circular machines.
	Slides WEO4LR03 [2.946 MB]