HB2012 - List of Keywords (damping)

Paper	Title	Other Keywords	Page
MOP212	Simulation of Longitudinal Beam Instability caused by HOMs	HOM, simulation, linac, cavity	73
	P. Cheng, Z. Li, J.Y. Tang, J.Q. Wang IHEP, Beijing, People's Republic of China
	Superconducting cavities are employed in C-ADS linac to accelerate 10mA CW proton beams from 3.2 MeV to 1.5 GeV. High order modes in superconducting cavities are found by using the simulation tools CST and HFSS, then power dissipation caused by HOMs have been investigated, it is indicated that the Qext should not go beyond 10⁷} in order to limit the additional heat load. Beam instabilities caused by high order modes in elliptical cavity sections are investigated using the code offered by Dr. Jean-Luc Biarrotte (CNRS, IPN Orsay, France). Beam errors, linac errors and high order modes frequency spread are investigated in detail. It shows that the monopole modes do not affect the proton beam critically and need no HOM couplers (Q_ext=10⁵}) if high order modes frequency spread is more than 100 kHz.

WEO1A02	LHC Impedance Model: Experience with High Intensity Operation in the LHC	impedance, octupole, injection, brightness	349
	B. Salvant, O. Aberle, G. Arduini, R.W. Aßmann, V. Baglin, M.J. Barnes, P. Baudrenghien, A. Bertarelli, C. Bracco, R. Bruce, X. Buffat, F. Carra, F. Caspers, G. Cattenoz, S.D. Claudet, H.A. Day, J. Esteban Müller, M. Garlaschè, L. Gentini, B. Goddard, A. Grudiev, B. Henrist, W. Herr, S. Jakobsen, R.J. Jones, G. Lanza, L. Lari, T. Mastoridis, N. Mounet, E. Métral, A.A. Nosych, J.L. Nougaret, S. Persichelli, T. Pieloni, A.M. Piguiet, S. Redaelli, F. Roncarolo, G. Rumolo, B. Salvachua, M. Sapinski, E.N. Shaposhnikova, L.J. Tavian, M.A. Timmins, J.A. Uythoven, A. Vidal, R. Wasef, D. Wollmann CERN, Geneva, Switzerland A.V. Burov Fermilab, Batavia, USA S.M. White BNL, Upton, Long Island, New York, USA
	The CERN Large Hadron Collider (LHC) is now in luminosity production mode and has been pushing its performance in the past months by increasing the proton beam brightness, the collision energy and the machine availability. As a consequence, collective effects have started to become more and more visible and have effectively slowed down the performance increase of the machine. Among these collective effects, the interaction of brighter LHC bunches with the longitudinal and transverse impedance of the machine has been observed to generate beam induced heating and transverse instabilities since 2010. This contribution reviews the current LHC impedance model obtained from theory, simulations and bench measurements as well as a selection of measured effects with the LHC beam.
	Slides WEO1A02 [7.991 MB]

WEO1A04	Longitudinal Instabilities in the SPS and Beam Dynamics Issues with High Harmonic RF Systems	emittance, beam-loading, synchrotron, controls	358
	E.N. Shaposhnikova, T. Argyropoulos, T. Bohl, J. Esteban Müller, H. Timko CERN, Geneva, Switzerland
	Even after a successful impedance reduction programme which eliminated the microwave instability in the SPS another longitudinal instability is still one of the main intensity limitations. It is observed during acceleration ramp for both single bunch and multibunch beams at intensities below the nominal LHC intensity. With the lower transition energy of the new SPS optics, under intensive studies now, the thresholds are increased. However, even in this case the operation of the 4th harmonic RF system is required for stability of the nominal beams. To cope with the higher intensity beams required for the future High Luminosity LHC an upgrade program for both RF systems is under way. The results of studies of the parameter space required for beam stability are presented and compared with operation modes of double RF systems in other accelerators.
	Slides WEO1A04 [6.135 MB]

WEO1B02	Optics Design Optimization for IBS Dominated Beams	emittance, optics, scattering, ion	386
	F. Antoniou, H. Bartosik, Y. Papaphilippou CERN, Geneva, Switzerland T. Demma LAL, Orsay, France N. Milas, A. Streun PSI, Villigen PSI, Switzerland M.T.F. Pivi SLAC, Menlo Park, California, USA
	Intra-beam scattering is a small angle multiple Coulomb scattering effect, leading to emittance growth. It becomes important for high brightness beams in low emittance lepton rings, but also hadron synchrotrons and ring colliders. Several theoretical models have been developed over the years, however, when the IBS becomes predominant, the divergence between the models becomes important. In addition, the theoretical models are based on the consideration of Gaussian beams and uncoupled transverse motion. Recently, two multi-particle tracking codes have been developed, in order to enable the understanding of the IBS influence on the beam distribution and the inclusion of coupling. The comparison between theoretical models in different lattices and different regimes is discussed here and the benchmarking of the theoretical models with the tracking codes is presented. Finally, first measurement results are presented in low emittance rings and hadron synchrotrons.
	Slides WEO1B02 [2.389 MB]

THO1B02	Test of Optical Stochastic Cooling in Fermilab	radiation, kicker, optics, pick-up	514
	V.A. Lebedev Fermilab, Batavia, USA M.S. Zolotorev LBNL, Berkeley, California, USA
	A new 150 MeV electron storage ring is planned to be build in Fermilab. The construction of new machine pursues two goals a test of highly non-linear integrable optics and a test of optical stochastic cooling (OSC). This paper discusses details of OSC arrangements and choice of major parameters of the cooling scheme. At the first step the cooling will be achieved without optical amplifier. It should introduce the damping rates of about 1 order of magnitudes higher than the cooling rates due to synchrotron radiation. Similar scheme looks as a promising technique for the LHC luminosity upgrade. Its details are also discussed.
	Slides THO1B02 [1.109 MB]

Paper

Title

Other Keywords

Page

MOP212

Simulation of Longitudinal Beam Instability caused by HOMs

HOM, simulation, linac, cavity

73

P. Cheng, Z. Li, J.Y. Tang, J.Q. Wang
IHEP, Beijing, People's Republic of China

Superconducting cavities are employed in C-ADS linac to accelerate 10mA CW proton beams from 3.2 MeV to 1.5 GeV. High order modes in superconducting cavities are found by using the simulation tools CST and HFSS, then power dissipation caused by HOMs have been investigated, it is indicated that the Qext should not go beyond 10⁷} in order to limit the additional heat load. Beam instabilities caused by high order modes in elliptical cavity sections are investigated using the code offered by Dr. Jean-Luc Biarrotte (CNRS, IPN Orsay, France). Beam errors, linac errors and high order modes frequency spread are investigated in detail. It shows that the monopole modes do not affect the proton beam critically and need no HOM couplers (Q_ext=10⁵}) if high order modes frequency spread is more than 100 kHz.

WEO1A02

LHC Impedance Model: Experience with High Intensity Operation in the LHC

impedance, octupole, injection, brightness

349

B. Salvant, O. Aberle, G. Arduini, R.W. Aßmann, V. Baglin, M.J. Barnes, P. Baudrenghien, A. Bertarelli, C. Bracco, R. Bruce, X. Buffat, F. Carra, F. Caspers, G. Cattenoz, S.D. Claudet, H.A. Day, J. Esteban Müller, M. Garlaschè, L. Gentini, B. Goddard, A. Grudiev, B. Henrist, W. Herr, S. Jakobsen, R.J. Jones, G. Lanza, L. Lari, T. Mastoridis, N. Mounet, E. Métral, A.A. Nosych, J.L. Nougaret, S. Persichelli, T. Pieloni, A.M. Piguiet, S. Redaelli, F. Roncarolo, G. Rumolo, B. Salvachua, M. Sapinski, E.N. Shaposhnikova, L.J. Tavian, M.A. Timmins, J.A. Uythoven, A. Vidal, R. Wasef, D. Wollmann
CERN, Geneva, Switzerland
A.V. Burov
Fermilab, Batavia, USA
S.M. White
BNL, Upton, Long Island, New York, USA

The CERN Large Hadron Collider (LHC) is now in luminosity production mode and has been pushing its performance in the past months by increasing the proton beam brightness, the collision energy and the machine availability. As a consequence, collective effects have started to become more and more visible and have effectively slowed down the performance increase of the machine. Among these collective effects, the interaction of brighter LHC bunches with the longitudinal and transverse impedance of the machine has been observed to generate beam induced heating and transverse instabilities since 2010. This contribution reviews the current LHC impedance model obtained from theory, simulations and bench measurements as well as a selection of measured effects with the LHC beam.

Slides WEO1A02 [7.991 MB]

WEO1A04

Longitudinal Instabilities in the SPS and Beam Dynamics Issues with High Harmonic RF Systems

emittance, beam-loading, synchrotron, controls

358

E.N. Shaposhnikova, T. Argyropoulos, T. Bohl, J. Esteban Müller, H. Timko
CERN, Geneva, Switzerland

Even after a successful impedance reduction programme which eliminated the microwave instability in the SPS another longitudinal instability is still one of the main intensity limitations. It is observed during acceleration ramp for both single bunch and multibunch beams at intensities below the nominal LHC intensity. With the lower transition energy of the new SPS optics, under intensive studies now, the thresholds are increased. However, even in this case the operation of the 4th harmonic RF system is required for stability of the nominal beams. To cope with the higher intensity beams required for the future High Luminosity LHC an upgrade program for both RF systems is under way. The results of studies of the parameter space required for beam stability are presented and compared with operation modes of double RF systems in other accelerators.

Slides WEO1A04 [6.135 MB]

WEO1B02

Optics Design Optimization for IBS Dominated Beams

emittance, optics, scattering, ion

386

F. Antoniou, H. Bartosik, Y. Papaphilippou
CERN, Geneva, Switzerland
T. Demma
LAL, Orsay, France
N. Milas, A. Streun
PSI, Villigen PSI, Switzerland
M.T.F. Pivi
SLAC, Menlo Park, California, USA

Intra-beam scattering is a small angle multiple Coulomb scattering effect, leading to emittance growth. It becomes important for high brightness beams in low emittance lepton rings, but also hadron synchrotrons and ring colliders. Several theoretical models have been developed over the years, however, when the IBS becomes predominant, the divergence between the models becomes important. In addition, the theoretical models are based on the consideration of Gaussian beams and uncoupled transverse motion. Recently, two multi-particle tracking codes have been developed, in order to enable the understanding of the IBS influence on the beam distribution and the inclusion of coupling. The comparison between theoretical models in different lattices and different regimes is discussed here and the benchmarking of the theoretical models with the tracking codes is presented. Finally, first measurement results are presented in low emittance rings and hadron synchrotrons.

Slides WEO1B02 [2.389 MB]

THO1B02

Test of Optical Stochastic Cooling in Fermilab

radiation, kicker, optics, pick-up

514

V.A. Lebedev
Fermilab, Batavia, USA
M.S. Zolotorev
LBNL, Berkeley, California, USA

A new 150 MeV electron storage ring is planned to be build in Fermilab. The construction of new machine pursues two goals a test of highly non-linear integrable optics and a test of optical stochastic cooling (OSC). This paper discusses details of OSC arrangements and choice of major parameters of the cooling scheme. At the first step the cooling will be achieved without optical amplifier. It should introduce the damping rates of about 1 order of magnitudes higher than the cooling rates due to synchrotron radiation. Similar scheme looks as a promising technique for the LHC luminosity upgrade. Its details are also discussed.

Slides THO1B02 [1.109 MB]