IPAC2017 - Classification: 05 Beam Dynamics and Electromagnetic Fields / D10 Beam-beam Effects - Theory, Simulations, Measurements, Code Developments

Paper	Title	Page
THPAB016	Investigation on the Ion Motion Towards Clearing Electrodes in an Accelerator	3723
	G. Pöplau COMPAEC e.G., Rostock, Germany A. Meseck HZB, Berlin, Germany
	High brightness beams provided by linac-based accelerators require several measures to preserve their high quality and to avoid instabilities, where the mitigation of the impact of residual ions is one of these measures, in particular if high repetition rates are aimed for. Over the last decade three ion-clearing strategies: clearing electrodes, bunch gaps and beam shaking have been applied to counteract the degrading impact of the ions on the electron beam. Currently, their merit as clearing strategies for next generation high brightness accelerators such as energy recovery linacs (ERLs) are under intensive investigations with both simulations and measurements. In this paper, we present numerical studies for the behavior of ions generated by electron bunch passages within the field of electrodes. The objective is to investigate the ion motion towards the electrodes and to study under which circumstances and up to which ratio, equilibrium between ion generation and ion-clearing is established. Hereby several ion species and shapes of electrodes are considered with typical parameters of future high current linacs.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB016
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THPAB021	Wake Field and Head-Tail Instability in Beam-Beam Collision with a Large Crossing Angle	3738
	K. Ohmi, D. Zhou KEK, Ibaraki, Japan N. Kuroo UTTAC, Tsukuba, Ibaraki, Japan K. Oide, F. Zimmermann CERN, Geneva, Switzerland
	Head-tail type of coherent beam-beam instability has been seen in a strong-strong beam-beam simulation for collision with a large Piwinski angle σ_zθ/σ_x>>1, where θ is a half crossing angle. Beta x* is key parameter for the instability. The instability is not serious for SuperKEKB, but can be seen in phase II commissioning stage. It has a large impact for design of FCC-ee. We introduce wake field due to the beam-beam collision. The wake field gives turn-by-turn correlation of head-tail mode. Head-tail instability caused by the wake field explains that seen in the strong-strong beam-beam simulation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB021
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THPAB042	Long-Range Beam-Beam Orbit Effects in LHC, Simulations and Observations From Machine Operation in 2016	3799
	A.A. Gorzawski, K. Fuchsberger, M. Hostettler, T. Pieloni, J. Wenninger CERN, Geneva, Switzerland
	To limit the number of head on collisions to only one at the interaction point in the Large Hadron Collider (LHC), two beams are colliding with a non zero crossing angle. Under the presence of such angle the closed orbits of the individual bunches in the bunch train varies due to the long-range beam-beam effects. These variations leave a signature as a non zero transverse offset at the collision points visible in the front and trail of the bunch train. When operation team aims for the optimised beam orbit and therefore maximised luminosity, those front and tail bunches due to the overall offset experience reduced luminosity. This paper describes an overview of the existing tool for simulating these effects and compares to operational data. The effects of different operational scenarios (i.e. beam brightness, reduced or asymmetric crossing angles between the interaction points etc.) are simulated and discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB042
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THPAB050	Simulations of Beam-Beam Interactions With RF-Track for the AWAKE Primary Beam Lines	3823
	J.S. Schmidt, A. Latina CERN, Geneva, Switzerland
	The AWAKE project at CERN will use a high-energy proton beam at 400 GeV/c to drive wake'elds in a plasma. The amplitude of these wake'elds will be probed by injecting into the plasma a low-energy electron beam (10-20 MeV/c), which will be accelerated to several GeV. Upstream of the plasma cell the two beams will either be transported coaxially or with an o'set of few millimetres for about 6 m. The interaction between the two beams in this beam line has been investigated in the past, with a dedicated simulation code tracking particles under the in'uence of direct space-charge e'ects. These simulations have recently been crosschecked with a new simulation code called RF-Track, developed at CERN to simulate low energy accelerators. RF-Track can track multiple-specie beams at arbitrary energies, taking into account the full electromagnetic particle-to-particle inter-action. For its characteristics RF-Track seems an ideal tool to study the AWAKE two-beam interaction. The results of these studies are presented in this paper and compared to the previous results. The implications for the facility performance are discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB050
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THPAB056	Dynamic Aperture Studies of the Long-Range Beam-Beam Interaction at the LHC	3840
	M.P. Crouch, R.B. Appleby UMAN, Manchester, United Kingdom J. Barranco García, T. Pieloni, C. Tambasco EPFL, Lausanne, Switzerland X. Buffat, M. Giovannozzi, E.H. Maclean CERN, Geneva, Switzerland B.D. Muratori STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
	Long-range beam-beam interactions dictate the choice of operational parameters for the LHC, such as the crossing angle and β^* and therefore the luminosity reach for the collider. These effects can lead to particle losses, closed orbit effects and emittance growth. Defining how these effects depend on the beam-beam separation will determine the minimum crossing angle and the β^* the LHC can operate. In this article, analysis from a dedicated machine study is presented in which the crossing angle was reduced in steps and the impact on beam intensity and luminosity lifetimes were observed. Based on the observations during the machine study, the intensity decays are compared to expectations from models. Estimates of the luminosity reach in the LHC are also computed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB056
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THPAB082	The Beam-Beam Effect and Its Consequences for the Modeling of the Jefferson Lab EIC	3909
	E.W. Nissen JLab, Newport News, Virginia, USA
	Funding: Notice: This manuscript has been authored by Jefferson Science Associates, LLC under Contract No. DE-AC05-06OR23177 with the U.S. Department of Energy In this work we address the effect of beam jitter on emittance growth as caused by the beam-beam effect on the Jefferson Lab Electron Ion Collider (JLEIC). This proposed collider would collide up to 100 GeV proton beams with up to 10 GeV electron beams. Due to the asymmetric rigidities of the beams and their non-linear lensing action on each other during a collision, collective effects can limit beam storage times. Using simulations we determined that one of JLEIC's synchronization concepts would require a new set of software tools to accurately understand phase space evolution.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB082
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Paper

Title

Page

Investigation on the Ion Motion Towards Clearing Electrodes in an Accelerator

3723

G. Pöplau
COMPAEC e.G., Rostock, Germany
A. Meseck
HZB, Berlin, Germany

High brightness beams provided by linac-based accelerators require several measures to preserve their high quality and to avoid instabilities, where the mitigation of the impact of residual ions is one of these measures, in particular if high repetition rates are aimed for. Over the last decade three ion-clearing strategies: clearing electrodes, bunch gaps and beam shaking have been applied to counteract the degrading impact of the ions on the electron beam. Currently, their merit as clearing strategies for next generation high brightness accelerators such as energy recovery linacs (ERLs) are under intensive investigations with both simulations and measurements. In this paper, we present numerical studies for the behavior of ions generated by electron bunch passages within the field of electrodes. The objective is to investigate the ion motion towards the electrodes and to study under which circumstances and up to which ratio, equilibrium between ion generation and ion-clearing is established. Hereby several ion species and shapes of electrodes are considered with typical parameters of future high current linacs.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB016

Export •

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

THPAB021

Wake Field and Head-Tail Instability in Beam-Beam Collision with a Large Crossing Angle

3738

K. Ohmi, D. Zhou
KEK, Ibaraki, Japan
N. Kuroo
UTTAC, Tsukuba, Ibaraki, Japan
K. Oide, F. Zimmermann
CERN, Geneva, Switzerland

Head-tail type of coherent beam-beam instability has been seen in a strong-strong beam-beam simulation for collision with a large Piwinski angle σ_zθ/σ_x>>1, where θ is a half crossing angle. Beta x* is key parameter for the instability. The instability is not serious for SuperKEKB, but can be seen in phase II commissioning stage. It has a large impact for design of FCC-ee. We introduce wake field due to the beam-beam collision. The wake field gives turn-by-turn correlation of head-tail mode. Head-tail instability caused by the wake field explains that seen in the strong-strong beam-beam simulation.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB021

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

THPAB042

Long-Range Beam-Beam Orbit Effects in LHC, Simulations and Observations From Machine Operation in 2016

3799

A.A. Gorzawski, K. Fuchsberger, M. Hostettler, T. Pieloni, J. Wenninger
CERN, Geneva, Switzerland

To limit the number of head on collisions to only one at the interaction point in the Large Hadron Collider (LHC), two beams are colliding with a non zero crossing angle. Under the presence of such angle the closed orbits of the individual bunches in the bunch train varies due to the long-range beam-beam effects. These variations leave a signature as a non zero transverse offset at the collision points visible in the front and trail of the bunch train. When operation team aims for the optimised beam orbit and therefore maximised luminosity, those front and tail bunches due to the overall offset experience reduced luminosity. This paper describes an overview of the existing tool for simulating these effects and compares to operational data. The effects of different operational scenarios (i.e. beam brightness, reduced or asymmetric crossing angles between the interaction points etc.) are simulated and discussed.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB042

Export •

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

THPAB050

Simulations of Beam-Beam Interactions With RF-Track for the AWAKE Primary Beam Lines

3823

J.S. Schmidt, A. Latina
CERN, Geneva, Switzerland

The AWAKE project at CERN will use a high-energy proton beam at 400 GeV/c to drive wake'elds in a plasma. The amplitude of these wake'elds will be probed by injecting into the plasma a low-energy electron beam (10-20 MeV/c), which will be accelerated to several GeV. Upstream of the plasma cell the two beams will either be transported coaxially or with an o'set of few millimetres for about 6 m. The interaction between the two beams in this beam line has been investigated in the past, with a dedicated simulation code tracking particles under the in'uence of direct space-charge e'ects. These simulations have recently been crosschecked with a new simulation code called RF-Track, developed at CERN to simulate low energy accelerators. RF-Track can track multiple-specie beams at arbitrary energies, taking into account the full electromagnetic particle-to-particle inter-action. For its characteristics RF-Track seems an ideal tool to study the AWAKE two-beam interaction. The results of these studies are presented in this paper and compared to the previous results. The implications for the facility performance are discussed.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB050

Export •

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

THPAB056

Dynamic Aperture Studies of the Long-Range Beam-Beam Interaction at the LHC

3840

M.P. Crouch, R.B. Appleby
UMAN, Manchester, United Kingdom
J. Barranco García, T. Pieloni, C. Tambasco
EPFL, Lausanne, Switzerland
X. Buffat, M. Giovannozzi, E.H. Maclean
CERN, Geneva, Switzerland
B.D. Muratori
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

Long-range beam-beam interactions dictate the choice of operational parameters for the LHC, such as the crossing angle and β^* and therefore the luminosity reach for the collider. These effects can lead to particle losses, closed orbit effects and emittance growth. Defining how these effects depend on the beam-beam separation will determine the minimum crossing angle and the β^* the LHC can operate. In this article, analysis from a dedicated machine study is presented in which the crossing angle was reduced in steps and the impact on beam intensity and luminosity lifetimes were observed. Based on the observations during the machine study, the intensity decays are compared to expectations from models. Estimates of the luminosity reach in the LHC are also computed.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB056

Export •

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

THPAB082

The Beam-Beam Effect and Its Consequences for the Modeling of the Jefferson Lab EIC

3909

E.W. Nissen
JLab, Newport News, Virginia, USA

Funding: Notice: This manuscript has been authored by Jefferson Science Associates, LLC under Contract No. DE-AC05-06OR23177 with the U.S. Department of Energy
In this work we address the effect of beam jitter on emittance growth as caused by the beam-beam effect on the Jefferson Lab Electron Ion Collider (JLEIC). This proposed collider would collide up to 100 GeV proton beams with up to 10 GeV electron beams. Due to the asymmetric rigidities of the beams and their non-linear lensing action on each other during a collision, collective effects can limit beam storage times. Using simulations we determined that one of JLEIC's synchronization concepts would require a new set of software tools to accurately understand phase space evolution.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB082

Export •

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