IPAC2011 - List of Authors (Bhat, C.M.)

Paper

Title

Page

Loss of Landau Damping in the LHC

211

E.N. Shaposhnikova, T. Argyropoulos, P. Baudrenghien, T. Bohl, A.C. Butterworth, J. Esteban Muller, T. Mastoridis, G. Papotti, J. Tückmantel, W. Venturini Delsolaro, U. Wehrle
CERN, Geneva, Switzerland
C.M. Bhat
Fermilab, Batavia, USA

Loss of Landau damping leading to a single bunch longitudinal quadrupole instability has been observed in the LHC during the ramp and on the 3.5 TeV flat top for small injected longitudinal emittances. The first measurements are in good agreement with the threshold calculated for the expected longitudinal reactive impedance budget of the LHC as well as with the threshold dependence on beam energy. The cure is a controlled longitudinal emittance blow-up during the ramp which for constant threshold through the cycle should provide an emittance proportional to the square root of energy.

TUPZ032

LHC Luminosity Upgrade with Large Piwinski Angle Scheme: A Recent Look

1879

C.M. Bhat
Fermilab, Batavia, USA
F. Zimmermann
CERN, Geneva, Switzerland

Funding: Work is supported by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy and US LARP.
Luminosity upgrade at the LHC collider using bunches with constant line charge density (longitudinally flat bunches) but with same beam-beam tune shift at collision, the so called large Piwinski angle scheme* is being studied with renewed interest in recent years**. By design the total beam-beam tune shift at the LHC is less than 0.015. But the initial operational experience at the LHC indicates the possibility of operating with beam-beam tune shifts as high as 0.02. In view of this development we have revisited the requirements for the Large Piwinski Angle scheme at the LHC. In this paper we present a new parameter list supported by 1) calculations on the luminosity gain, 2) reduction of e-cloud issues on nearly flat bunches and 3) longitudinal beam dynamics simulations. We also make some remarks on the needed upgrades on the LHC injector accelerators.
* F. Ruggiero and F. Zimmermann, PRST-AB 5, 061001 (2002).
** C. M. Bhat, CERN-2009-004, pp. 10⁶-114.
Thanks to O.Bruning, E.Shaposhnikova, H.Damerau, E.Mahner, F.Caspers & CERN BE/ABP & RF Depts.

WEPS107

Phase Space Coating in Synchrotrons: Some Applications*

2763

C.M. Bhat
Fermilab, Batavia, USA

Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy
Phase-space painting to produce very high intensity beam in synchrotrons is one of the widely studied topics in accelerator physics. A remarkable example of this is multi-turn beam injection by transverse phase-space painting in spallation sources. Use of barrier buckets at synchrotron storage rings has paved way for further advancements in this field. The Fermilab Recycler, antiproton storage ring, has been augmented with multipurpose broad-band barrier rf systems. Recently we have developed a longitudinal phase-space coating technique over already e-cooled high intensity low longitudinal antiproton beam and demonstrated with beam experiments. This method is extended to map the incoherent synchrotron tune of beam particles in a barrier bucket. Here I review various phase-space painting techniques being used in particle accelerators including some new schemes developed using barrier rf systems and possible new applications.

THOBA01

Electron Cloud Observations in LHC

2862

G. Rumolo, G. Arduini, V. Baglin, H. Bartosik, P. Baudrenghien, N. Biancacci, G. Bregliozzi, S.D. Claudet, R. De Maria, J. Esteban Muller, M. Favier, C. Hansen, W. Höfle, J.M. Jimenez, V. Kain, E. Koukovini, G. Lanza, K.S.B. Li, G.H.I. Maury Cuna, E. Métral, G. Papotti, T. Pieloni, F. Roncarolo, B. Salvant, E.N. Shaposhnikova, R.J. Steinhagen, L.J. Tavian, D. Valuch, W. Venturini Delsolaro, F. Zimmermann
CERN, Geneva, Switzerland
C.M. Bhat
Fermilab, Batavia, USA
U. Iriso
CELLS-ALBA Synchrotron, Cerdanyola del Vallès, Spain
N. Mounet, C. Zannini
EPFL, Lausanne, Switzerland

Operation of LHC with bunch trains different spacings has revealed the formation of an electron cloud inside the machine. The main observations of electron cloud build-up are the pressure rise measured at the vacuum gauges in the warm regions, as well as the increase of the beam screen temperature in the cold regions due to an additional heat load. The effects of the electron cloud were also visible as a strong instability and emittance growth affecting the last bunches of longer trains, which could be improved running with higher chromaticity and/or larger transverse emittances. A summary of the 2010 and 2011 observations and measurements and a comparison with existing models will be presented. The efficiency of scrubbing and scrubbing strategies to improve the machine running performance will be also briefly discussed.

Slides THOBA01 [2.911 MB]

Paper	Title	Page
MOPC057	Loss of Landau Damping in the LHC	211
	E.N. Shaposhnikova, T. Argyropoulos, P. Baudrenghien, T. Bohl, A.C. Butterworth, J. Esteban Muller, T. Mastoridis, G. Papotti, J. Tückmantel, W. Venturini Delsolaro, U. Wehrle CERN, Geneva, Switzerland C.M. Bhat Fermilab, Batavia, USA
	Loss of Landau damping leading to a single bunch longitudinal quadrupole instability has been observed in the LHC during the ramp and on the 3.5 TeV flat top for small injected longitudinal emittances. The first measurements are in good agreement with the threshold calculated for the expected longitudinal reactive impedance budget of the LHC as well as with the threshold dependence on beam energy. The cure is a controlled longitudinal emittance blow-up during the ramp which for constant threshold through the cycle should provide an emittance proportional to the square root of energy.

TUPZ032	LHC Luminosity Upgrade with Large Piwinski Angle Scheme: A Recent Look	1879
	C.M. Bhat Fermilab, Batavia, USA F. Zimmermann CERN, Geneva, Switzerland
	Funding: Work is supported by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy and US LARP. Luminosity upgrade at the LHC collider using bunches with constant line charge density (longitudinally flat bunches) but with same beam-beam tune shift at collision, the so called large Piwinski angle scheme* is being studied with renewed interest in recent years*. By design the total beam-beam tune shift at the LHC is less than 0.015. But the initial operational experience at the LHC indicates the possibility of operating with beam-beam tune shifts as high as 0.02. In view of this development we have revisited the requirements for the Large Piwinski Angle scheme at the LHC. In this paper we present a new parameter list supported by 1) calculations on the luminosity gain, 2) reduction of e-cloud issues on nearly flat bunches and 3) longitudinal beam dynamics simulations. We also make some remarks on the needed upgrades on the LHC injector accelerators. F. Ruggiero and F. Zimmermann, PRST-AB 5, 061001 (2002). ** C. M. Bhat, CERN-2009-004, pp. 10⁶-114. Thanks to O.Bruning, E.Shaposhnikova, H.Damerau, E.Mahner, F.Caspers & CERN BE/ABP & RF Depts.

WEPS107	Phase Space Coating in Synchrotrons: Some Applications*	2763
	C.M. Bhat Fermilab, Batavia, USA
	Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy Phase-space painting to produce very high intensity beam in synchrotrons is one of the widely studied topics in accelerator physics. A remarkable example of this is multi-turn beam injection by transverse phase-space painting in spallation sources. Use of barrier buckets at synchrotron storage rings has paved way for further advancements in this field. The Fermilab Recycler, antiproton storage ring, has been augmented with multipurpose broad-band barrier rf systems. Recently we have developed a longitudinal phase-space coating technique over already e-cooled high intensity low longitudinal antiproton beam and demonstrated with beam experiments. This method is extended to map the incoherent synchrotron tune of beam particles in a barrier bucket. Here I review various phase-space painting techniques being used in particle accelerators including some new schemes developed using barrier rf systems and possible new applications.

THOBA01	Electron Cloud Observations in LHC	2862
	G. Rumolo, G. Arduini, V. Baglin, H. Bartosik, P. Baudrenghien, N. Biancacci, G. Bregliozzi, S.D. Claudet, R. De Maria, J. Esteban Muller, M. Favier, C. Hansen, W. Höfle, J.M. Jimenez, V. Kain, E. Koukovini, G. Lanza, K.S.B. Li, G.H.I. Maury Cuna, E. Métral, G. Papotti, T. Pieloni, F. Roncarolo, B. Salvant, E.N. Shaposhnikova, R.J. Steinhagen, L.J. Tavian, D. Valuch, W. Venturini Delsolaro, F. Zimmermann CERN, Geneva, Switzerland C.M. Bhat Fermilab, Batavia, USA U. Iriso CELLS-ALBA Synchrotron, Cerdanyola del Vallès, Spain N. Mounet, C. Zannini EPFL, Lausanne, Switzerland
	Operation of LHC with bunch trains different spacings has revealed the formation of an electron cloud inside the machine. The main observations of electron cloud build-up are the pressure rise measured at the vacuum gauges in the warm regions, as well as the increase of the beam screen temperature in the cold regions due to an additional heat load. The effects of the electron cloud were also visible as a strong instability and emittance growth affecting the last bunches of longer trains, which could be improved running with higher chromaticity and/or larger transverse emittances. A summary of the 2010 and 2011 observations and measurements and a comparison with existing models will be presented. The efficiency of scrubbing and scrubbing strategies to improve the machine running performance will be also briefly discussed.
	Slides THOBA01 [2.911 MB]