IPAC2018 - List of Authors (Stern, E.G.)

Paper	Title	Page
THPAF068	Suppression of Instabilities Generated by an Anti-Damper With a Nonlinear Magnetic Element in IOTA	3134
	E.G. Stern, J.F. Amundson, A. Macridin Fermilab, Batavia, Illinois, USA
	Funding: US Department of Energy The Integrable Optics Test Accelerator (IOTA) storage ring is being constructed at Fermilab as a testbed for new accelerator concepts. One important series of experiments tests the use of a novel nonlinear magnetic insert to damp coherent instabilities. To test the damping power of the ele- ment, an instability of desired strength may be intentionally excited with an anti-damper. We report on simulations of beam stabilization using the Synergia modeling framework over ranges of driving and damping strengths.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF068
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THPAF069	Particle Tracking Simulation of Collective Modes - Parametric Landau Damping Off Coupling Resonance	3137
	A. Macridin, J.F. Amundson, A.V. Burov, P. Spentzouris, E.G. Stern Fermilab, Batavia, Illinois, USA
	Employing Synergia simulations with the DMD method we investigate the Landau damping of space charge modes in bunched beams. The simulations reveal two instances of the parametric damping mechanism in bunched beams. The first example occurs in the proximity of coupling resonance and is due to the oscillation of particles' amplitudes in the transverse plane. This oscillation modulates the mode-particle coupling with particle dependent trapping frequency. The second example is due to the modulation of the mode-particle coupling in one transverse plane by the oscillatory motion in the other plane.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF069
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THPAF071	McMillan Lens in a System with Space Charge	3143
	I. Lobach University of Chicago, Chicago, Illinois, USA S. Nagaitsev, E.G. Stern, T. Zolkin Fermilab, Batavia, Illinois, USA
	Space charge (SC) in a circulating beam in a ring produces both betatron tune shift and betatron tune spread. These effects make some particles move on to a machine resonance and become unstable. Linear elements of beam optics cannot reduce the tune spread induced by SC because of its intrinsic nonlinear nature. We investigate the possibility to mitigate it by a thin McMillan lens providing a nonlinear axially symmetric kick, which is qualitatively opposite to the accumulated kick by SC. Experimentally, the proposed concept can be tested in Fermilab's IOTA ring. A thin McMillan lens can be implemented by a short (70 cm) insertion of an electron beam with specifically chosen density distribution in transverse directions. In this article, to see if McMillan lenses reduce the tune spread induced by SC, we make several simulations with particle tracking code Synergia. We choose such beam and lattice parameters that tune spread is roughly 0.5 and a beam instability due to the half-integer resonance 0.5 is observed. Then, we try to reduce emittance growth by shifting betatron tunes by adjusting quadrupoles and reducing the tune spread by McMillan lenses.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF071
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THPAF075	Numerical Simulations of Space Charge Compensation with an Electron Lens	3154
	E.G. Stern, Y.I. Alexahin, J.F. Amundson, A.V. Burov, A. Macridin, V.D. Shiltsev Fermilab, Batavia, Illinois, USA
	The future high energy physics program at Fermilab requires that the proton complex operate with beam bunch intensities four times larger than is currently handled. At these intensities space charge nonlinear defocussing effects cause unacceptable particle losses especially in the low energy rapid-cycling-synchrotron (RCS) Booster. Focusing electron lens elements may offer a solution by providing partial space charge compensation but there is a need for detailed simulations as this technique has not been demonstrated. We report on high fidelity numerical 6D space charge simulations in a model accelerator lattice with a record high space charge tune shift approaching unity.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF075
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Paper

Title

Page

Suppression of Instabilities Generated by an Anti-Damper With a Nonlinear Magnetic Element in IOTA

3134

E.G. Stern, J.F. Amundson, A. Macridin
Fermilab, Batavia, Illinois, USA

Funding: US Department of Energy
The Integrable Optics Test Accelerator (IOTA) storage ring is being constructed at Fermilab as a testbed for new accelerator concepts. One important series of experiments tests the use of a novel nonlinear magnetic insert to damp coherent instabilities. To test the damping power of the ele- ment, an instability of desired strength may be intentionally excited with an anti-damper. We report on simulations of beam stabilization using the Synergia modeling framework over ranges of driving and damping strengths.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF068

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THPAF069

Particle Tracking Simulation of Collective Modes - Parametric Landau Damping Off Coupling Resonance

3137

A. Macridin, J.F. Amundson, A.V. Burov, P. Spentzouris, E.G. Stern
Fermilab, Batavia, Illinois, USA

Employing Synergia simulations with the DMD method we investigate the Landau damping of space charge modes in bunched beams. The simulations reveal two instances of the parametric damping mechanism in bunched beams. The first example occurs in the proximity of coupling resonance and is due to the oscillation of particles' amplitudes in the transverse plane. This oscillation modulates the mode-particle coupling with particle dependent trapping frequency. The second example is due to the modulation of the mode-particle coupling in one transverse plane by the oscillatory motion in the other plane.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF069

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reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPAF071

McMillan Lens in a System with Space Charge

3143

I. Lobach
University of Chicago, Chicago, Illinois, USA
S. Nagaitsev, E.G. Stern, T. Zolkin
Fermilab, Batavia, Illinois, USA

Space charge (SC) in a circulating beam in a ring produces both betatron tune shift and betatron tune spread. These effects make some particles move on to a machine resonance and become unstable. Linear elements of beam optics cannot reduce the tune spread induced by SC because of its intrinsic nonlinear nature. We investigate the possibility to mitigate it by a thin McMillan lens providing a nonlinear axially symmetric kick, which is qualitatively opposite to the accumulated kick by SC. Experimentally, the proposed concept can be tested in Fermilab's IOTA ring. A thin McMillan lens can be implemented by a short (70 cm) insertion of an electron beam with specifically chosen density distribution in transverse directions. In this article, to see if McMillan lenses reduce the tune spread induced by SC, we make several simulations with particle tracking code Synergia. We choose such beam and lattice parameters that tune spread is roughly 0.5 and a beam instability due to the half-integer resonance 0.5 is observed. Then, we try to reduce emittance growth by shifting betatron tunes by adjusting quadrupoles and reducing the tune spread by McMillan lenses.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF071

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPAF075

Numerical Simulations of Space Charge Compensation with an Electron Lens

3154

E.G. Stern, Y.I. Alexahin, J.F. Amundson, A.V. Burov, A. Macridin, V.D. Shiltsev
Fermilab, Batavia, Illinois, USA

The future high energy physics program at Fermilab requires that the proton complex operate with beam bunch intensities four times larger than is currently handled. At these intensities space charge nonlinear defocussing effects cause unacceptable particle losses especially in the low energy rapid-cycling-synchrotron (RCS) Booster. Focusing electron lens elements may offer a solution by providing partial space charge compensation but there is a need for detailed simulations as this technique has not been demonstrated. We report on high fidelity numerical 6D space charge simulations in a model accelerator lattice with a record high space charge tune shift approaching unity.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF075

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)