IPAC2021 - Classification: MC5: Beam Dynamics and EM Fields / D06 Coherent and Incoherent Instabilities

Paper	Title	Page
TUPAB222	Application and Development of the Streak Camera Measurement System at HLS-II	1942
	Y.K. Zhao, S.S. Jin, P. Lu, B.G. Sun, J.G. Wang, F.F. Wu, T.Y. Zhou USTC/NSRL, Hefei, Anhui, People’s Republic of China
	The dual-axial scan streak camera plays an important role in the super-fast optical measurement and the beam diagnosis of the accelerators. Indeed, the development of the synchrotron light measurement system by virtue of the streak camera provides an effective tool and research platform for accelerator physics and super-fast optical phenomenon. In this paper, the configuration of the streak camera measurement system is roughly described. And the experimental researches are simultaneously performed, including the bunch lengthening, the potential-well distortion, the longitudinal bunch oscillations, and the beam evolution during the single bunch operation mode in the HLS-II storage ring. Moreover, the effects of the RF modulation on the beam lifetime and longitudinal bunch beam dynamics are carried out.
	Poster TUPAB222 [1.713 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB222
About •	paper received ※ 10 May 2021 paper accepted ※ 16 June 2021 issue date ※ 14 August 2021
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TUPAB262	The Characteristic of the Beam Position Growth in CSNS/RCS	2073
	L. Huang, S. Wang IHEP, Beijing, People’s Republic of China S.Y. Xu DNSC, Dongguan, People’s Republic of China
	Funding: Work supported by NNSF of China: N0. U1832210 An instability of the beam position growth is observed in the beam commissioning of the Rapid Cycling Synchrotron of the China Spallation Neutron Source. To simplify the study, a series of measurements have been performed to characterize the instability in the DC mode with consistent energy of 80 MeV. The measurement campaign is introduced in the paper and it conforms to the characteristics of the coupled bunch instability.
	Poster TUPAB262 [3.748 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB262
About •	paper received ※ 13 May 2021 paper accepted ※ 02 June 2021 issue date ※ 22 August 2021
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WEPAB239	Effect of Chromaticity and Feedback on Transverse Head-Tail Instability	3189
	V.V. Smaluk, G. Bassi, A. Blednykh, A. Khan BNL, Upton, New York, USA
	Funding: This work was supported by the US Department of Energy under contract DE-SC0012704. The head-tail instability caused by the beam interaction with short-range wakefields is a major limitation for the single-bunch beam intensity in circular accelerators. The combined effect of the transverse feedback systems and chromaticity suppressing the instability is discussed. Theoretical and experimental studies of the head-tail instability and methods of its mitigation are reviewed. Results of experimental studies of the transverse mode coupling carried out at NSLS-II are compared with the theoretical model and numerical simulations.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB239
About •	paper received ※ 19 May 2021 paper accepted ※ 24 June 2021 issue date ※ 12 August 2021
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WEPAB240	Increasing the Single-Bunch Instability Threshold by Bunch Splitting Due to RF Phase Modulation	3193
	J.L. Steinmann, E. Blomley, M. Brosi, E. Bründermann, A. Mochihashi, A.-S. Müller, M. Schuh, P. Schönfeldt KIT, Karlsruhe, Germany
	Funding: This work is funded by the BMBF contract number: 05K16VKA. RF phase modulation at twice the synchrotron frequency can be used to split a stored electron bunch into two or more bunchlets orbiting each other. We report on time-resolved measurements at the Karlsruhe Research Accelerator (KARA), where this bunch splitting was used to increase the threshold current of the microbunching instability, happening in the short-bunch operation mode. Turning the modulation on and off reproducibly affects the sawtooth behavior of the emitted coherent synchrotron radiation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB240
About •	paper received ※ 19 May 2021 paper accepted ※ 08 July 2021 issue date ※ 18 August 2021
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WEPAB243	Longitudinal Microwave Instability Study at Transition Crossing with Ion Beams in the CERN PS	3197
	A. Lasheen, H. Damerau, A. Huschauer, B.K. Popovic CERN, Meyrin, Switzerland
	The luminosity of lead ion collisions in the Large Hadron Collider (LHC) was significantly increased during the 2018 ion run by reducing the bunch spacing from 100 ns to 75 ns, allowing to increase the total number of bunches. With the new 75 ns variant, three instead of four bunches are generated each cycle in the Low Energy Ion Ring (LEIR) and the Proton Synchrotron (PS) with up to 30% larger intensity per bunch. The beam was produced with satisfactory quality but at the limit of stability in the injectors. In particular, the minimum longitudinal emittance in the PS is limited by a strong longitudinal microwave instability occurring just after transition crossing. The uncontrolled blow-up generates tails, which translate into an unacceptably large satellite population following the RF manipulations prior to extraction from the PS. In this paper, instability measurements are compared to particle simulations using the latest PS impedance model to identify the driving impedance sources. Moreover, means to mitigate the instability are discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB243
About •	paper received ※ 19 May 2021 paper accepted ※ 06 July 2021 issue date ※ 29 August 2021
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WEPAB245	A Possible Modification of Ceramic Chambers in the Injection Area at the RCS in J-PARC	3205
	Y. Shobuda, K. Horino, J. Kamiya, K. Kotoku, T. Takayanagi, T. Ueno, T. Yanagibashi JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
	The J-PARC RCS is composed of ceramic chambers covered over copper stripes to suppress the eddy current on the chamber. The inductance, comprising the copper stripes and flanges, in combination with the capacitors makes an LCR electric circuit with the chamber and can cause field modulation in the chamber. Though most chambers are not harmful at the RCS, the chambers at the injection area excite beam losses, because a trapezoid field pattern is excited to accumulate LINAC beam during the injection period. In this report, we consider several types of ceramic chambers to suppress the field modulation. One type is a ceramic chamber covered over copper stripes in parallel with damping resistors. Another is that covered over spiral copper stripes with only capacitors.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB245
About •	paper received ※ 19 May 2021 paper accepted ※ 01 July 2021 issue date ※ 18 August 2021
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WEPAB246	Influence of Different Beam Energies on the Micro-Bunching Instability	3209
	M. Brosi, A.-S. Müller, P. Schreiber, M. Schuh KIT, Karlsruhe, Germany
	During the operation of an electron synchrotron with short electron bunches, the beam dynamics are influenced by the occurrence of the micro-bunching instability. This collective instability is caused by the self-interaction of a short electron bunch with its own emitted coherent synchrotron radiation (CSR). Above a certain threshold bunch current dynamic micro-structures start to occur on the longitudinal phase space density. The resulting dynamics depend on various parameters and were previously investigated in relation to, amongst others, the momentum compaction factor and the acceleration voltage. In this contribution, the influence of the energy of the electrons on the dynamics of the micro-bunching instability is studied based on measurements at the KIT storage ring KARA (Karlsruhe Research Accelerator).
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB246
About •	paper received ※ 19 May 2021 paper accepted ※ 08 July 2021 issue date ※ 11 August 2021
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THXA02	Overview of the Micro-Bunching Instability in Electron Storage Rings and Evolving Diagnostics	3686
	M. Brosi KIT, Karlsruhe, Germany
	The micro-bunching instability is a longitudinal instability that leads to dynamical deformations of the charge distribution in the longitudinal phase space. It affects the longitudinal charge distribution, and thus the emitted coherent synchrotron radiation spectra, as well as the energy distribution of the electron bunch. Not only the threshold in the bunch current above which the instability occurs, but also the dynamics above the instability threshold strongly depends on machine parameters, e.g., natural bunch length, accelerating voltage, momentum compaction factor, and beam energy. All this makes the understanding and potential mitigation or control of the micro-bunching instability an important topic for the next generation of light sources and circular e⁺/e⁻ colliders. This presentation will give a review on the micro-bunching instability and discuss how technological advances in the turn-by-turn and bunch-by-bunch diagnostics are leading to a deeper understanding of this intriguing phenomenon.
	Slides THXA02 [23.626 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THXA02
About •	paper received ※ 19 May 2021 paper accepted ※ 23 July 2021 issue date ※ 31 August 2021
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

Application and Development of the Streak Camera Measurement System at HLS-II

1942

Y.K. Zhao, S.S. Jin, P. Lu, B.G. Sun, J.G. Wang, F.F. Wu, T.Y. Zhou
USTC/NSRL, Hefei, Anhui, People’s Republic of China

The dual-axial scan streak camera plays an important role in the super-fast optical measurement and the beam diagnosis of the accelerators. Indeed, the development of the synchrotron light measurement system by virtue of the streak camera provides an effective tool and research platform for accelerator physics and super-fast optical phenomenon. In this paper, the configuration of the streak camera measurement system is roughly described. And the experimental researches are simultaneously performed, including the bunch lengthening, the potential-well distortion, the longitudinal bunch oscillations, and the beam evolution during the single bunch operation mode in the HLS-II storage ring. Moreover, the effects of the RF modulation on the beam lifetime and longitudinal bunch beam dynamics are carried out.

Poster TUPAB222 [1.713 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB222

About •

paper received ※ 10 May 2021 paper accepted ※ 16 June 2021 issue date ※ 14 August 2021

Export •

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

TUPAB262

The Characteristic of the Beam Position Growth in CSNS/RCS

2073

L. Huang, S. Wang
IHEP, Beijing, People’s Republic of China
S.Y. Xu
DNSC, Dongguan, People’s Republic of China

Funding: Work supported by NNSF of China: N0. U1832210
An instability of the beam position growth is observed in the beam commissioning of the Rapid Cycling Synchrotron of the China Spallation Neutron Source. To simplify the study, a series of measurements have been performed to characterize the instability in the DC mode with consistent energy of 80 MeV. The measurement campaign is introduced in the paper and it conforms to the characteristics of the coupled bunch instability.

Poster TUPAB262 [3.748 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB262

About •

paper received ※ 13 May 2021 paper accepted ※ 02 June 2021 issue date ※ 22 August 2021

Export •

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

WEPAB239

Effect of Chromaticity and Feedback on Transverse Head-Tail Instability

3189

V.V. Smaluk, G. Bassi, A. Blednykh, A. Khan
BNL, Upton, New York, USA

Funding: This work was supported by the US Department of Energy under contract DE-SC0012704.
The head-tail instability caused by the beam interaction with short-range wakefields is a major limitation for the single-bunch beam intensity in circular accelerators. The combined effect of the transverse feedback systems and chromaticity suppressing the instability is discussed. Theoretical and experimental studies of the head-tail instability and methods of its mitigation are reviewed. Results of experimental studies of the transverse mode coupling carried out at NSLS-II are compared with the theoretical model and numerical simulations.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB239

About •

paper received ※ 19 May 2021 paper accepted ※ 24 June 2021 issue date ※ 12 August 2021

Export •

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

WEPAB240

Increasing the Single-Bunch Instability Threshold by Bunch Splitting Due to RF Phase Modulation

3193

J.L. Steinmann, E. Blomley, M. Brosi, E. Bründermann, A. Mochihashi, A.-S. Müller, M. Schuh, P. Schönfeldt
KIT, Karlsruhe, Germany

Funding: This work is funded by the BMBF contract number: 05K16VKA.
RF phase modulation at twice the synchrotron frequency can be used to split a stored electron bunch into two or more bunchlets orbiting each other. We report on time-resolved measurements at the Karlsruhe Research Accelerator (KARA), where this bunch splitting was used to increase the threshold current of the microbunching instability, happening in the short-bunch operation mode. Turning the modulation on and off reproducibly affects the sawtooth behavior of the emitted coherent synchrotron radiation.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB240

About •

paper received ※ 19 May 2021 paper accepted ※ 08 July 2021 issue date ※ 18 August 2021

Export •

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

WEPAB243

Longitudinal Microwave Instability Study at Transition Crossing with Ion Beams in the CERN PS

3197

A. Lasheen, H. Damerau, A. Huschauer, B.K. Popovic
CERN, Meyrin, Switzerland

The luminosity of lead ion collisions in the Large Hadron Collider (LHC) was significantly increased during the 2018 ion run by reducing the bunch spacing from 100 ns to 75 ns, allowing to increase the total number of bunches. With the new 75 ns variant, three instead of four bunches are generated each cycle in the Low Energy Ion Ring (LEIR) and the Proton Synchrotron (PS) with up to 30% larger intensity per bunch. The beam was produced with satisfactory quality but at the limit of stability in the injectors. In particular, the minimum longitudinal emittance in the PS is limited by a strong longitudinal microwave instability occurring just after transition crossing. The uncontrolled blow-up generates tails, which translate into an unacceptably large satellite population following the RF manipulations prior to extraction from the PS. In this paper, instability measurements are compared to particle simulations using the latest PS impedance model to identify the driving impedance sources. Moreover, means to mitigate the instability are discussed.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB243

About •

paper received ※ 19 May 2021 paper accepted ※ 06 July 2021 issue date ※ 29 August 2021

Export •

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

WEPAB245

A Possible Modification of Ceramic Chambers in the Injection Area at the RCS in J-PARC

3205

Y. Shobuda, K. Horino, J. Kamiya, K. Kotoku, T. Takayanagi, T. Ueno, T. Yanagibashi
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan

The J-PARC RCS is composed of ceramic chambers covered over copper stripes to suppress the eddy current on the chamber. The inductance, comprising the copper stripes and flanges, in combination with the capacitors makes an LCR electric circuit with the chamber and can cause field modulation in the chamber. Though most chambers are not harmful at the RCS, the chambers at the injection area excite beam losses, because a trapezoid field pattern is excited to accumulate LINAC beam during the injection period. In this report, we consider several types of ceramic chambers to suppress the field modulation. One type is a ceramic chamber covered over copper stripes in parallel with damping resistors. Another is that covered over spiral copper stripes with only capacitors.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB245

About •

paper received ※ 19 May 2021 paper accepted ※ 01 July 2021 issue date ※ 18 August 2021

Export •

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

WEPAB246

Influence of Different Beam Energies on the Micro-Bunching Instability

3209

M. Brosi, A.-S. Müller, P. Schreiber, M. Schuh
KIT, Karlsruhe, Germany

During the operation of an electron synchrotron with short electron bunches, the beam dynamics are influenced by the occurrence of the micro-bunching instability. This collective instability is caused by the self-interaction of a short electron bunch with its own emitted coherent synchrotron radiation (CSR). Above a certain threshold bunch current dynamic micro-structures start to occur on the longitudinal phase space density. The resulting dynamics depend on various parameters and were previously investigated in relation to, amongst others, the momentum compaction factor and the acceleration voltage. In this contribution, the influence of the energy of the electrons on the dynamics of the micro-bunching instability is studied based on measurements at the KIT storage ring KARA (Karlsruhe Research Accelerator).

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB246

About •

paper received ※ 19 May 2021 paper accepted ※ 08 July 2021 issue date ※ 11 August 2021

Export •

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

THXA02

Overview of the Micro-Bunching Instability in Electron Storage Rings and Evolving Diagnostics

3686

M. Brosi
KIT, Karlsruhe, Germany

The micro-bunching instability is a longitudinal instability that leads to dynamical deformations of the charge distribution in the longitudinal phase space. It affects the longitudinal charge distribution, and thus the emitted coherent synchrotron radiation spectra, as well as the energy distribution of the electron bunch. Not only the threshold in the bunch current above which the instability occurs, but also the dynamics above the instability threshold strongly depends on machine parameters, e.g., natural bunch length, accelerating voltage, momentum compaction factor, and beam energy. All this makes the understanding and potential mitigation or control of the micro-bunching instability an important topic for the next generation of light sources and circular e⁺/e⁻ colliders. This presentation will give a review on the micro-bunching instability and discuss how technological advances in the turn-by-turn and bunch-by-bunch diagnostics are leading to a deeper understanding of this intriguing phenomenon.

Slides THXA02 [23.626 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THXA02

About •

paper received ※ 19 May 2021 paper accepted ※ 23 July 2021 issue date ※ 31 August 2021

Export •

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