HB2016 - Table of Session: THA7 (Working Group A

Paper	Title	Page
THPM5X01	Using an Electron Cooler for Space Charge Compensation in the GSI Synchrotron SIS18	496
	W.D. Stem, O. Boine-Frankenheim TEMF, TU Darmstadt, Darmstadt, Germany O. Boine-Frankenheim GSI, Darmstadt, Germany
	Funding: Work is supported by BMBF contract FKZ:05P15RDRBA For the future operation of the SIS18 as a booster synchrotron for the FAIR SIS100, space charge and beam lifetime are expected to be the main intensity limitations. Intensity is limited in part by the space-charge-induced incoherent tune shift in bunched beams. A co-propagating, low energy electron lens can compensate for this tune shift by applying opposing space-charge fields in the ion beam. In this paper, we study the effect of using the existing electron cooler at the SIS18 as a space charge compensation device. We anticipate beta beating may arise due to the singular localized focusing error, and explore the possibility of adding additional lenses to reduce this error. We also study the effect of electron lenses on the coherent (collective) and incoherent (single-particle) stopbands. Furthermore, we estimate the lifetime of partially stripped heavy-ions due to charge exchange process in the lens.
	Slides THPM5X01 [4.731 MB]
DOI •	reference for this paper ※ DOI:10.18429/JACoW-HB2016-THPM5X01
Export •	reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPM6X01	Space Charge Effects in FFAG	499
	M. Haj Tahar, F. Méot BNL, Upton, Long Island, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. Understanding space charge effects in FFAG is crucial in order to assess their potential for high power applications. This paper shows that, to carry out parametric studies of these effects in FFAG, the average field index of the focusing and defocusing magnets are the natural parametrization. Using several classes of particle distribution functions, we investigate the effects of space charge forces on the non-linear beam dynamics of FFAG and provide stability diagrams for an FFAG-like lattice. The method developed in this study is mainly applicable to systems with slowly varying parameters, i.e slow acceleration.
	Slides THPM6X01 [2.171 MB]
DOI •	reference for this paper ※ DOI:10.18429/JACoW-HB2016-THPM6X01
Export •	reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPM7X01	Use of RF Quadrupole Structures to Enhance Stability in Accelerator Rings	505
	M. Schenk, A. Grudiev, K.S.B. Li, K. Papke CERN, Geneva, Switzerland
	The beams required for the high luminosity upgrade of the Large Hadron Collider (HL-LHC) at CERN call for efficient mechanisms to suppress transverse collective instabilities. In addition to octupole magnets installed for the purpose of Landau damping, we propose to use radio frequency (rf) quadrupole structures to considerably enhance the aforementioned stabilising effect. By means of the PyHEADTAIL macroparticle tracking code, the stabilising mechanism introduced by an rf quadrupole is studied and discussed. As a specific example, the performance of an rf quadrupole system in presence of magnetic octupoles is demonstrated for HL-LHC. Furthermore, potential performance limitations such as the excitation of synchro-betatron resonances are pointed out. Finally, efforts towards possible measurements with the CERN Super Proton Synchrotron (SPS) are discussed aiming at studying the underlying stabilising mechanisms experimentally.
	Slides THPM7X01 [37.755 MB]
DOI •	reference for this paper ※ DOI:10.18429/JACoW-HB2016-THPM7X01
Export •	reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPM8X01	Early Tests and Simulation of Quasi-Integrable Octupole Lattices at the University of Maryland Electron Ring	511
	K.J. Ruisard, H. Baumgartner, B. Beaudoin, I. Haber, T.W. Koeth, D.B. Matthew UMD, College Park, Maryland, USA
	Funding: Work and travel supported by NSF GRFP, NSF Accelerator Science Program, DOE-HEP and UMD Graduate School ICSSA award. Nonlinear quasi-integrable optics is a promising development on the horizon of high-intensity ring design. Large amplitude-dependent tune spreads, driven by strong nonlinear magnet inserts, lead to decoherence from incoherent tune resonances. This reduces intensity-driven beam loss while quasi-integrability ensures contained orbits. The experimental program at the University of Maryland Electron Ring (UMER) will explore the performance of a strong octupole lattice at a range of operating points. Early measurements use a distributed octupole lattice, consisting of several small octupole inserts. We vary lattice tune to change the quasi-integrable condition as well as probe behavior near different resonant conditions. Simulation results show there should be invariant conservation under carefully chosen conditions. We discuss the effect of steering errors on the lattice performance and on-going efforts to reduce these errors. We also discuss plans for a single-channel insert.
	Slides THPM8X01 [56.742 MB]
DOI •	reference for this paper ※ DOI:10.18429/JACoW-HB2016-THPM8X01
Export •	reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPM9X01	Space Charge Effects and Mitigation in the CERN PS Booster, in View of the Upgrade	517
	E. Benedetto, M. Cieslak-Kowalska, V. Forte, F. Schmidt CERN, Geneva, Switzerland M. Cieslak-Kowalska EPFL, Lausanne, Switzerland V. Forte Université Blaise Pascal, Clermont-Ferrand, France
	The CERN PS Booster (PSB) is presently running with a space-charge tune spread larger than 0.5 at injection. Since the High Luminosity LHC (HL-LHC) will require beams with twice the intensity and brightness of today, the LHC Injector Upgrade (LIU) Project is putting in place an upgrade program for all the injector chain and, in particular, it relies on the important assumption that the PS Booster can successfully produce these beams after the implementation of the 160 MeV H⁻ injection from Linac4. This contribution describes the studies (measurements and simulations) that have been carried out to confirm that the PSB can indeed perform as needed in terms of beam brightness for the future HL-LHC runs. The importance of the mitigation measures already in place, such as the correction of the half-integer line, and the effects of non-linear resonances on the beam are also discussed.
	Slides THPM9X01 [6.786 MB]
DOI •	reference for this paper ※ DOI:10.18429/JACoW-HB2016-THPM9X01
Export •	reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPM10X01	Stripline Beam Position Monitors With Improved Frequency Response and Their Coupling Impedances	523
	Y. Shobuda JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan Y.H. Chin, K. Takata KEK, Ibaraki, Japan K.G. Nakamura Kyoto University, Kyoto, Japan T. Toyama J-PARC, KEK & JAEA, Ibaraki-ken, Japan
	In J-PARC Main Ring, transverse intra-bunch oscillations have been observed during the injection and at the onset of acceleration. Up to now, the beam instability is suppressed by the intra-bunch feedback system, where the stripline beam position monitors operate at 10⁸.8 MHz. However, there is a concern that electron cloud instabilities may appear and limit the beam current at future higher power operations. For the case, we have developed a wider-band (several GHz) beam position monitor by deforming the electrode shapes. The modification of the electrode can be done not to enhance the beam coupling impedance. For the typical electrode shapes, we show the coupling impedances as well as the frequency responses of the electrodes.
	Slides THPM10X01 [5.240 MB]
DOI •	reference for this paper ※ DOI:10.18429/JACoW-HB2016-THPM10X01
Export •	reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

Using an Electron Cooler for Space Charge Compensation in the GSI Synchrotron SIS18

496

W.D. Stem, O. Boine-Frankenheim
TEMF, TU Darmstadt, Darmstadt, Germany
O. Boine-Frankenheim
GSI, Darmstadt, Germany

Funding: Work is supported by BMBF contract FKZ:05P15RDRBA
For the future operation of the SIS18 as a booster synchrotron for the FAIR SIS100, space charge and beam lifetime are expected to be the main intensity limitations. Intensity is limited in part by the space-charge-induced incoherent tune shift in bunched beams. A co-propagating, low energy electron lens can compensate for this tune shift by applying opposing space-charge fields in the ion beam. In this paper, we study the effect of using the existing electron cooler at the SIS18 as a space charge compensation device. We anticipate beta beating may arise due to the singular localized focusing error, and explore the possibility of adding additional lenses to reduce this error. We also study the effect of electron lenses on the coherent (collective) and incoherent (single-particle) stopbands. Furthermore, we estimate the lifetime of partially stripped heavy-ions due to charge exchange process in the lens.

Slides THPM5X01 [4.731 MB]

DOI •

reference for this paper ※ DOI:10.18429/JACoW-HB2016-THPM5X01

Export •

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

THPM6X01

Space Charge Effects in FFAG

499

M. Haj Tahar, F. Méot
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Understanding space charge effects in FFAG is crucial in order to assess their potential for high power applications. This paper shows that, to carry out parametric studies of these effects in FFAG, the average field index of the focusing and defocusing magnets are the natural parametrization. Using several classes of particle distribution functions, we investigate the effects of space charge forces on the non-linear beam dynamics of FFAG and provide stability diagrams for an FFAG-like lattice. The method developed in this study is mainly applicable to systems with slowly varying parameters, i.e slow acceleration.

Slides THPM6X01 [2.171 MB]

DOI •

reference for this paper ※ DOI:10.18429/JACoW-HB2016-THPM6X01

Export •

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

THPM7X01

Use of RF Quadrupole Structures to Enhance Stability in Accelerator Rings

505

M. Schenk, A. Grudiev, K.S.B. Li, K. Papke
CERN, Geneva, Switzerland

The beams required for the high luminosity upgrade of the Large Hadron Collider (HL-LHC) at CERN call for efficient mechanisms to suppress transverse collective instabilities. In addition to octupole magnets installed for the purpose of Landau damping, we propose to use radio frequency (rf) quadrupole structures to considerably enhance the aforementioned stabilising effect. By means of the PyHEADTAIL macroparticle tracking code, the stabilising mechanism introduced by an rf quadrupole is studied and discussed. As a specific example, the performance of an rf quadrupole system in presence of magnetic octupoles is demonstrated for HL-LHC. Furthermore, potential performance limitations such as the excitation of synchro-betatron resonances are pointed out. Finally, efforts towards possible measurements with the CERN Super Proton Synchrotron (SPS) are discussed aiming at studying the underlying stabilising mechanisms experimentally.

Slides THPM7X01 [37.755 MB]

DOI •

reference for this paper ※ DOI:10.18429/JACoW-HB2016-THPM7X01

Export •

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

THPM8X01

Early Tests and Simulation of Quasi-Integrable Octupole Lattices at the University of Maryland Electron Ring

511

K.J. Ruisard, H. Baumgartner, B. Beaudoin, I. Haber, T.W. Koeth, D.B. Matthew
UMD, College Park, Maryland, USA

Funding: Work and travel supported by NSF GRFP, NSF Accelerator Science Program, DOE-HEP and UMD Graduate School ICSSA award.
Nonlinear quasi-integrable optics is a promising development on the horizon of high-intensity ring design. Large amplitude-dependent tune spreads, driven by strong nonlinear magnet inserts, lead to decoherence from incoherent tune resonances. This reduces intensity-driven beam loss while quasi-integrability ensures contained orbits. The experimental program at the University of Maryland Electron Ring (UMER) will explore the performance of a strong octupole lattice at a range of operating points. Early measurements use a distributed octupole lattice, consisting of several small octupole inserts. We vary lattice tune to change the quasi-integrable condition as well as probe behavior near different resonant conditions. Simulation results show there should be invariant conservation under carefully chosen conditions. We discuss the effect of steering errors on the lattice performance and on-going efforts to reduce these errors. We also discuss plans for a single-channel insert.

Slides THPM8X01 [56.742 MB]

DOI •

reference for this paper ※ DOI:10.18429/JACoW-HB2016-THPM8X01

Export •

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

THPM9X01

Space Charge Effects and Mitigation in the CERN PS Booster, in View of the Upgrade

517

E. Benedetto, M. Cieslak-Kowalska, V. Forte, F. Schmidt
CERN, Geneva, Switzerland
M. Cieslak-Kowalska
EPFL, Lausanne, Switzerland
V. Forte
Université Blaise Pascal, Clermont-Ferrand, France

The CERN PS Booster (PSB) is presently running with a space-charge tune spread larger than 0.5 at injection. Since the High Luminosity LHC (HL-LHC) will require beams with twice the intensity and brightness of today, the LHC Injector Upgrade (LIU) Project is putting in place an upgrade program for all the injector chain and, in particular, it relies on the important assumption that the PS Booster can successfully produce these beams after the implementation of the 160 MeV H⁻ injection from Linac4. This contribution describes the studies (measurements and simulations) that have been carried out to confirm that the PSB can indeed perform as needed in terms of beam brightness for the future HL-LHC runs. The importance of the mitigation measures already in place, such as the correction of the half-integer line, and the effects of non-linear resonances on the beam are also discussed.

Slides THPM9X01 [6.786 MB]

DOI •

reference for this paper ※ DOI:10.18429/JACoW-HB2016-THPM9X01

Export •

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

THPM10X01

Stripline Beam Position Monitors With Improved Frequency Response and Their Coupling Impedances

523

Y. Shobuda
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
Y.H. Chin, K. Takata
KEK, Ibaraki, Japan
K.G. Nakamura
Kyoto University, Kyoto, Japan
T. Toyama
J-PARC, KEK & JAEA, Ibaraki-ken, Japan

In J-PARC Main Ring, transverse intra-bunch oscillations have been observed during the injection and at the onset of acceleration. Up to now, the beam instability is suppressed by the intra-bunch feedback system, where the stripline beam position monitors operate at 10⁸.8 MHz. However, there is a concern that electron cloud instabilities may appear and limit the beam current at future higher power operations. For the case, we have developed a wider-band (several GHz) beam position monitor by deforming the electrode shapes. The modification of the electrode can be done not to enhance the beam coupling impedance. For the typical electrode shapes, we show the coupling impedances as well as the frequency responses of the electrodes.

Slides THPM10X01 [5.240 MB]

DOI •

reference for this paper ※ DOI:10.18429/JACoW-HB2016-THPM10X01

Export •

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