IPAC2017 - List of Authors (Li, K.S.B.)

Paper	Title	Page
MOZA1	Electron Cloud Effects at the LHC and LHC Injectors	30
	G. Rumolo, H. Bartosik, E. Belli, P. Dijkstal, G. Iadarola, K.S.B. Li, L. Mether, A. Romano, M. Schenk, F. Zimmermann CERN, Geneva, Switzerland E. Belli University of Rome La Sapienza, Rome, Italy P. Dijkstal TU Darmstadt, Darmstadt, Germany M. Schenk EPFL, Lausanne, Switzerland
	Electron cloud effects are one of the main limitations of the performance of the LHC and its injectors. Enormous progress has been done in the simulation of the electron cloud build-up and of the effects on beam stability while mitigation measures have been identified and implemented (scrubbing, low secondary electron yield coatings, etc.). The above has allowed reaching nominal beam parameters in the LHC during Run 2. A review of the studies and results obtained and the strategy and expected performance for the High Luminosity operation of the LHC will be presented.
	Slides MOZA1 [12.855 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOZA1
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MOPAB113	Usage of the Transverse Damper Observation Box for High Sampling Rate Transverse Position Data in the LHC	389
	L.R. Carver, X. Buffat, A.C. Butterworth, W. Höfle, G. Iadarola, G. Kotzian, K.S.B. Li, E. Métral, M. Ojeda Sandonís, M.E. Söderén, D. Valuch CERN, Geneva, Switzerland
	The transverse damper observation box (ADTObsBox) is a device that makes accessible the bunch-by-bunch turn-by-turn data recorded from the pickups of the LHC transverse damper. This device can provide online transient analysis of different beam dynamics effects (tunes and damping times at injection, for example), while also under development is an online coherent instability triggering system. This paper will provide an overview of the current setup and plans for future upgrades, as well as detailing how it deals with the large volume of data being generated. The results of some analysis that rely on the ADTObsBox will also be shown.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPAB113
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TUPIK091	Simulation Tools for the Design and Performance Evaluation of Transverse Feedback Systems	1912
	J. Komppula, W. Höfle, K.S.B. Li CERN, Geneva, Switzerland
	Transverse feedback systems are used in synchrotrons and storage rings to damp injection oscillations and suppress transverse instabilities. Especially instabilities driven by high intensity beams in future circular colliders such as the FCC set challenging requirements for transverse feedback systems. In order to develop a transverse feedback system able to meet those requirements, sophisticated simulation tools are required. For this purpose, a new modular framework for modeling a transverse feedback system has been developed in Python. The framework can be used as a transverse feedback module in the macro-particle beam dynamics simulation code PyHEADTAIL or as a separate tool for studying a feedback model from a control theory point of view by using a simple signal models for the beam. The main principle of the code is presented and simulation methods used for the conceptual design of the FCC are discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPIK091
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TUPIK119	Control of Intra-Bunch Vertical Instabilities at the SPS - Measurements and Technology Demonstration	2005
	J.D. Fox, J.E. Dusatko, C.H. Rivetta, O. Turgut SLAC, Menlo Park, California, USA H. Bartosik, W. Höfle, K.S.B. Li, E. Métral, B. Salvant, U. Wehrle CERN, Geneva, Switzerland S. De Santis LBNL, Berkeley, California, USA
	Funding: Work supported by the U.S. Department of Energy under contract # DOE-AC02-76SF00515, the US LHC Accelerator Research Program ( LARP), the FP7 High Luminosity LHC Project and the US-Japan Cooperative Program in High Energy Physics We present recent measurements demonstrating control of unstable beam motion in single bunch and bunch train configurations at the SPS. The work is motivated by anticipated intensity increases from the LIU and HL-LHC upgrade programs, and has included the development of a GHz bandwidth reconfigurable 4 GS/S signal processor with wideband kickers and associated amplifiers. The system was operated at 3.2GS/s with 16 samples across a 5 ns RF bucket (4.2 ns bunch at injection). The experimental results confirm damping of intra-bunch instabilities in both Q20 and Q26 optics configurations for intensities of 2x10¹¹ P/bunch. Instabilities with growth times of 200 turns are well-controlled from injection, consistent with the achievable gains for the 2 installed stripline kickers with 1 kW broadband power. Measurements from multiple studies in single-bunch and bunch train configurations show achieved damping rates, control of multiple intra-bunch modes, behavior of the system at injection and final damped noise floor. We present an analysis method to study the relative phase of slice motion during a transient to discriminate between TMCI and other types of Head-Tail instabilities.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPIK119
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TUPVA018	Macroparticle Simulation Studies of the LHC Beam Dynamics in the Presence of Electron Cloud	2081
SUSPSIK003	use link to see paper's listing under its alternate paper code
	A. Romano, G. Iadarola, K.S.B. Li, G. Rumolo CERN, Geneva, Switzerland
	Beam quality degradation caused by the Electron Cloud (EC) effects has been identified as one of the main performance limitations for the high intensity 25 ns beams in the Large Hadron Collider (LHC). When a proton bunch passes through an EC, electrons are attracted towards the transverse center of the beam resulting into an increasing electron density within the bunch. The effects driven by the interaction of the electrons with the bunch have been studied with macroparticle simulations in order to evaluate, in different operational scenarios, the threshold for the coherent instabilities as well as the incoherent tune spread. This contribution will summarize the main findings of the simulation study and compare them with the available experimental observations.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPVA018
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WEOAB3	RF Quadrupole Structures for Transverse Landau Damping in Circular Accelerators	2516
	M. Schenk, X. Buffat, L.R. Carver, A. Grudiev, K.S.B. Li, E. Métral, K. Papke CERN, Geneva, Switzerland A. Maillard ENS, Paris, France
	The beams required for the high luminosity upgrade of the Large Hadron Collider (HL-LHC) and other potential future circular colliders (FCC) call for efficient mechanisms to suppress transverse collective instabilities. In addition to octupole magnets installed for the purpose of Landau damping in the transverse planes, we propose to use radio frequency (rf) quadrupole structures to considerably enhance the aforementioned stabilising effect. By means of the PyHEADTAIL macroparticle tracking code as well as analytical studies, the stabilising mechanism introduced by an rf quadrupole is studied and explained. It is, furthermore, compared to the influence of the second order chromaticity on transverse beam stability.
	Slides WEOAB3 [2.537 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEOAB3
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THPAB005	Improvement of the Analytic Vlasov Solver DELPHI	3688
	D. Amorim Université Grenoble Alpes, Grenoble, France N. Biancacci, K.S.B. Li, E. Métral CERN, Geneva, Switzerland
	The simulation code DELPHI is an analytic Vlasov solver which allows to evaluate the beam transverse stability with respect to impedance effects. It allows to perform fast scans over parameters such as chromaticity, damper gain or beam intensity for a given impedance model and particle distribution. In order to improve the simulation code, new longitudinal particle distributions have been implemented. The simulations results obtained with these distributions are compared to theoretical predictions. An additional post-processing of DELPHI's output has also been implemented, allowing to reconstruct the signal seen by head-tail stripline monitors, in particular in presence of bunch-by-bunch damper. The results are compared to theoretical models, to pyHEADTAIL simulations and to measurements performed in the LHC.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB005
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THPAB040	Destabilising Effect of Linear Coupling in the LHC	3791
	L.R. Carver, D. Amorim, N. Biancacci, X. Buffat, K.S.B. Li, E. Métral, B. Salvant, M. Schenk CERN, Geneva, Switzerland
	During operation in 2015 and 2016, some transverse instabilities were observed when either the coupling (or closest tune approach) C- was large, or when the tunes were moved closer together. This motivated a campaign of simulations on the effect of linear coupling on the transverse stability. Measurements made during operation and with dedicated beam time have been found to confirm the predictions. This paper will detail the results of the linear coupling studies and relate them to operation of the LHC in the future.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB040
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THPAB043	Evolution of Python Tools for the Simulation of Electron Cloud Effects	3803
	G. Iadarola, E. Belli, K.S.B. Li, L. Mether, A. Romano, G. Rumolo CERN, Geneva, Switzerland
	PyECLOUD was originally developed as a tool for the simulation of electron cloud build-up in particle accelerators. Over the last five years the code has become part of a wider set of modular and scriptable python tools that can be combined to study different effects of the e-cloud in increasingly complex scenarios. The Particle In Cell solver originally included in PyECLOUD later developed into a stand-alone general purpose library (PyPIC) that now includes advanced features like a refined modeling of curved boundaries and optimized resolution based on the usage of nested grids. The effects of the e-cloud on the beam dynamics can be simulated interfacing PyECLOUD with the PyHEADTAIL code. These simulations can be computationally very demanding due to the multi-scale nature of this kind of problems. Hence, a dedicated parallelization layer (PyPARIS) has been recently developed to profit of parallel computing resources in order to significantly speed-up the computation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB043
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THPVA026	Practical Stabilisation of Transverse Collective Instabilities with Second Order Chromaticity in the LHC	4477
SUSPSIK059	use link to see paper's listing under its alternate paper code
	M. Schenk, D. Amorim, N. Biancacci, X. Buffat, L.R. Carver, R. De Maria, K.S.B. Li, E. Métral, B. Salvant CERN, Geneva, Switzerland
	The study reports on dedicated measurements made with a single nominal bunch in the LHC at 6.5 TeV. First, we show that a significant amount of second order chromaticity Q'' can be introduced in the machine in a well-controlled manner. Second, we demonstrate that the incoherent betatron tune spread from Q'' can provide beam stability through the Landau damping mechanism. This is a first step in the development of a Q'' knob to be potentially applied during regular physics operation in the LHC.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPVA026
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

Electron Cloud Effects at the LHC and LHC Injectors

30

G. Rumolo, H. Bartosik, E. Belli, P. Dijkstal, G. Iadarola, K.S.B. Li, L. Mether, A. Romano, M. Schenk, F. Zimmermann
CERN, Geneva, Switzerland
E. Belli
University of Rome La Sapienza, Rome, Italy
P. Dijkstal
TU Darmstadt, Darmstadt, Germany
M. Schenk
EPFL, Lausanne, Switzerland

Electron cloud effects are one of the main limitations of the performance of the LHC and its injectors. Enormous progress has been done in the simulation of the electron cloud build-up and of the effects on beam stability while mitigation measures have been identified and implemented (scrubbing, low secondary electron yield coatings, etc.). The above has allowed reaching nominal beam parameters in the LHC during Run 2. A review of the studies and results obtained and the strategy and expected performance for the High Luminosity operation of the LHC will be presented.

Slides MOZA1 [12.855 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOZA1

Export •

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

MOPAB113

Usage of the Transverse Damper Observation Box for High Sampling Rate Transverse Position Data in the LHC

389

L.R. Carver, X. Buffat, A.C. Butterworth, W. Höfle, G. Iadarola, G. Kotzian, K.S.B. Li, E. Métral, M. Ojeda Sandonís, M.E. Söderén, D. Valuch
CERN, Geneva, Switzerland

The transverse damper observation box (ADTObsBox) is a device that makes accessible the bunch-by-bunch turn-by-turn data recorded from the pickups of the LHC transverse damper. This device can provide online transient analysis of different beam dynamics effects (tunes and damping times at injection, for example), while also under development is an online coherent instability triggering system. This paper will provide an overview of the current setup and plans for future upgrades, as well as detailing how it deals with the large volume of data being generated. The results of some analysis that rely on the ADTObsBox will also be shown.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPAB113

Export •

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

TUPIK091

Simulation Tools for the Design and Performance Evaluation of Transverse Feedback Systems

1912

J. Komppula, W. Höfle, K.S.B. Li
CERN, Geneva, Switzerland

Transverse feedback systems are used in synchrotrons and storage rings to damp injection oscillations and suppress transverse instabilities. Especially instabilities driven by high intensity beams in future circular colliders such as the FCC set challenging requirements for transverse feedback systems. In order to develop a transverse feedback system able to meet those requirements, sophisticated simulation tools are required. For this purpose, a new modular framework for modeling a transverse feedback system has been developed in Python. The framework can be used as a transverse feedback module in the macro-particle beam dynamics simulation code PyHEADTAIL or as a separate tool for studying a feedback model from a control theory point of view by using a simple signal models for the beam. The main principle of the code is presented and simulation methods used for the conceptual design of the FCC are discussed.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPIK091

Export •

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TUPIK119

Control of Intra-Bunch Vertical Instabilities at the SPS - Measurements and Technology Demonstration

2005

J.D. Fox, J.E. Dusatko, C.H. Rivetta, O. Turgut
SLAC, Menlo Park, California, USA
H. Bartosik, W. Höfle, K.S.B. Li, E. Métral, B. Salvant, U. Wehrle
CERN, Geneva, Switzerland
S. De Santis
LBNL, Berkeley, California, USA

Funding: Work supported by the U.S. Department of Energy under contract # DOE-AC02-76SF00515, the US LHC Accelerator Research Program ( LARP), the FP7 High Luminosity LHC Project and the US-Japan Cooperative Program in High Energy Physics
We present recent measurements demonstrating control of unstable beam motion in single bunch and bunch train configurations at the SPS. The work is motivated by anticipated intensity increases from the LIU and HL-LHC upgrade programs, and has included the development of a GHz bandwidth reconfigurable 4 GS/S signal processor with wideband kickers and associated amplifiers. The system was operated at 3.2GS/s with 16 samples across a 5 ns RF bucket (4.2 ns bunch at injection). The experimental results confirm damping of intra-bunch instabilities in both Q20 and Q26 optics configurations for intensities of 2x10¹¹ P/bunch. Instabilities with growth times of 200 turns are well-controlled from injection, consistent with the achievable gains for the 2 installed stripline kickers with 1 kW broadband power. Measurements from multiple studies in single-bunch and bunch train configurations show achieved damping rates, control of multiple intra-bunch modes, behavior of the system at injection and final damped noise floor. We present an analysis method to study the relative phase of slice motion during a transient to discriminate between TMCI and other types of Head-Tail instabilities.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPIK119

Export •

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TUPVA018

Macroparticle Simulation Studies of the LHC Beam Dynamics in the Presence of Electron Cloud

2081

SUSPSIK003

use link to see paper's listing under its alternate paper code

A. Romano, G. Iadarola, K.S.B. Li, G. Rumolo
CERN, Geneva, Switzerland

Beam quality degradation caused by the Electron Cloud (EC) effects has been identified as one of the main performance limitations for the high intensity 25 ns beams in the Large Hadron Collider (LHC). When a proton bunch passes through an EC, electrons are attracted towards the transverse center of the beam resulting into an increasing electron density within the bunch. The effects driven by the interaction of the electrons with the bunch have been studied with macroparticle simulations in order to evaluate, in different operational scenarios, the threshold for the coherent instabilities as well as the incoherent tune spread. This contribution will summarize the main findings of the simulation study and compare them with the available experimental observations.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPVA018

Export •

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

WEOAB3

RF Quadrupole Structures for Transverse Landau Damping in Circular Accelerators

2516

M. Schenk, X. Buffat, L.R. Carver, A. Grudiev, K.S.B. Li, E. Métral, K. Papke
CERN, Geneva, Switzerland
A. Maillard
ENS, Paris, France

The beams required for the high luminosity upgrade of the Large Hadron Collider (HL-LHC) and other potential future circular colliders (FCC) call for efficient mechanisms to suppress transverse collective instabilities. In addition to octupole magnets installed for the purpose of Landau damping in the transverse planes, we propose to use radio frequency (rf) quadrupole structures to considerably enhance the aforementioned stabilising effect. By means of the PyHEADTAIL macroparticle tracking code as well as analytical studies, the stabilising mechanism introduced by an rf quadrupole is studied and explained. It is, furthermore, compared to the influence of the second order chromaticity on transverse beam stability.

Slides WEOAB3 [2.537 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEOAB3

Export •

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

THPAB005

Improvement of the Analytic Vlasov Solver DELPHI

3688

D. Amorim
Université Grenoble Alpes, Grenoble, France
N. Biancacci, K.S.B. Li, E. Métral
CERN, Geneva, Switzerland

The simulation code DELPHI is an analytic Vlasov solver which allows to evaluate the beam transverse stability with respect to impedance effects. It allows to perform fast scans over parameters such as chromaticity, damper gain or beam intensity for a given impedance model and particle distribution. In order to improve the simulation code, new longitudinal particle distributions have been implemented. The simulations results obtained with these distributions are compared to theoretical predictions. An additional post-processing of DELPHI's output has also been implemented, allowing to reconstruct the signal seen by head-tail stripline monitors, in particular in presence of bunch-by-bunch damper. The results are compared to theoretical models, to pyHEADTAIL simulations and to measurements performed in the LHC.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB005

Export •

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

THPAB040

Destabilising Effect of Linear Coupling in the LHC

3791

L.R. Carver, D. Amorim, N. Biancacci, X. Buffat, K.S.B. Li, E. Métral, B. Salvant, M. Schenk
CERN, Geneva, Switzerland

During operation in 2015 and 2016, some transverse instabilities were observed when either the coupling (or closest tune approach) C- was large, or when the tunes were moved closer together. This motivated a campaign of simulations on the effect of linear coupling on the transverse stability. Measurements made during operation and with dedicated beam time have been found to confirm the predictions. This paper will detail the results of the linear coupling studies and relate them to operation of the LHC in the future.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB040

Export •

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

THPAB043

Evolution of Python Tools for the Simulation of Electron Cloud Effects

3803

G. Iadarola, E. Belli, K.S.B. Li, L. Mether, A. Romano, G. Rumolo
CERN, Geneva, Switzerland

PyECLOUD was originally developed as a tool for the simulation of electron cloud build-up in particle accelerators. Over the last five years the code has become part of a wider set of modular and scriptable python tools that can be combined to study different effects of the e-cloud in increasingly complex scenarios. The Particle In Cell solver originally included in PyECLOUD later developed into a stand-alone general purpose library (PyPIC) that now includes advanced features like a refined modeling of curved boundaries and optimized resolution based on the usage of nested grids. The effects of the e-cloud on the beam dynamics can be simulated interfacing PyECLOUD with the PyHEADTAIL code. These simulations can be computationally very demanding due to the multi-scale nature of this kind of problems. Hence, a dedicated parallelization layer (PyPARIS) has been recently developed to profit of parallel computing resources in order to significantly speed-up the computation.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB043

Export •

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

THPVA026

Practical Stabilisation of Transverse Collective Instabilities with Second Order Chromaticity in the LHC

4477

SUSPSIK059

use link to see paper's listing under its alternate paper code

M. Schenk, D. Amorim, N. Biancacci, X. Buffat, L.R. Carver, R. De Maria, K.S.B. Li, E. Métral, B. Salvant
CERN, Geneva, Switzerland

The study reports on dedicated measurements made with a single nominal bunch in the LHC at 6.5 TeV. First, we show that a significant amount of second order chromaticity Q'' can be introduced in the machine in a well-controlled manner. Second, we demonstrate that the incoherent betatron tune spread from Q'' can provide beam stability through the Landau damping mechanism. This is a first step in the development of a Q'' knob to be potentially applied during regular physics operation in the LHC.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPVA026

Export •

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