IPAC2022 - Classification: MC5: Beam Dynamics and EM Fields / D06: Coherent and Incoherent Instabilities

Paper	Title	Page
MOOYSP2	Measurements of Collective Effects Related to Beam Coupling Impedance at SIRIUS	34
	F.H. de Sá, M.B. Alves, L. Liu LNLS, Campinas, Brazil
	Sirius is the new storage-ring-based 4th generation synchrotron light source built and operated by the Brazilian Synchrotron Light Laboratory (LNLS) at the Brazilian Center for Research in Energy and Materials (CNPEM). In ultralow emittance storage rings such as Sirius, the small radius of the vacuum chamber gives rise to strong beam coupling impedances which significantly alter the stored beam dynamics. In this work, we present the single-bunch measurements made so far to characterize such effects and compare the results with those simulated using the impedance budget built during the storage ring design.
	Slides MOOYSP2 [2.496 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOOYSP2
About •	Received ※ 08 June 2022 — Accepted ※ 15 June 2022 — Issue date ※ 20 June 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPOTK046	Improved Longitudinal Performance of the LHC Beam in the CERN PS	2165
	H. Damerau, V.D. Desquiens, A. Huschauer, A. Jibar, A. Lasheen, B. Mikulec, M. Morvillo, C. Rossi, B.J. Woolley CERN, Meyrin, Switzerland
	At the end of the 2018 run the intensity target for the High-Luminosity LHC (HL-LHC) had just been reached at extraction from the Proton Synchrotron (PS). In the framework of the LHC Injectors Upgrade (LIU) project additional RF improvements have been implemented during the 2019/2020 long shutdown (LS2), mainly impacting the impedance of the 10 MHz, 40 MHz, and 80 MHz RF systems. With the upgraded injection energy of 2 GeV (kinetic), also the intermediate plateau energy for RF manipulations has been increased. Following a campaign of beam studies throughout the 2021 run, a bunch intensity of up to 2.9·10¹¹ p/b in trains of 72 bunches is achieved with the required longitudinal beam quality, surpassing the LIU target of 2.6·10¹¹ p/b. The threshold of longitudinal quadrupolar coupled-bunch instabilities is increased during acceleration, but they are again observed at the flat-top. While dipolar coupled-bunch oscillations are well damped by a dedicated feedback system, the quadrupolar modes are suppressed by operating a 40 MHz system as an active higher-harmonic Landau cavity. The main commissioning steps are outlined, together with the key contributions to the improved beam performance.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOTK046
About •	Received ※ 07 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 16 June 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPOTK055	Beam Lifetime Measurements in Sirius Storage Ring	2186
SUSPMF072	use link to see paper's listing under its alternate paper code
	M.B. Alves, L. Liu, X.R. Resende, F.H. de Sá LNLS, Campinas, Brazil
	SIRIUS is the new storage ring-based 4th generation synchrotron light source built and operated by the Brazilian Synchrotron Light Laboratory (LNLS) at the Brazilian Center for Research in Energy and Materials (CNPEM). In ultralow emittance storage rings such as SIRIUS, the dominant contribution to the beam lifetime is due to large angle scattering between electrons within the same bunch, namely the Touschek effect. We used the strategy of storing two bunches simultaneously with different currents to measure their Touschek lifetime independently of other contributions, such as gas scattering. The measurements were carried out in different conditions of bunch current and RF voltage to compare the experimental results with those expected from theory and simulations for SIRIUS.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOTK055
About •	Received ※ 08 June 2022 — Accepted ※ 15 June 2022 — Issue date ※ 24 June 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPOTK057	Towards Direct Detection of the Shape of CSR Pulses with Fast THz Detectors	2190
	J.L. Steinmann, M. Brosi, E. Bründermann, A. Mochihashi, A.-S. Müller, P. Schreiber KIT, Karlsruhe, Germany
	Funding: We acknowledge in part support by the Helmholtz President’s strategic fund IVF "Plasma accelerators". This work is funded in part by the BMBF contract number: 05K19VKD. Coherent synchrotron radiation (CSR) is emitted when the emitting structure is equal to or smaller than the observed wavelength. Consequently, these pulses are very short and most detectors respond with their impulse response, regardless of the pulse length and shape. Here we present single-shot measurements performed at the Karlsruhe Research Accelerator (KARA) using a fast real-time oscilloscope and Schottky barrier detectors sensitive in the sub-THz range. The time response of this setup to CSR pulses emitted by electron bunches during the microbunching instability is shown to be sensitive to the shape of the electron bunch. Our results show how, in the future, the shape of electron bunches can be directly measured using a straightforward setup.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOTK057
About •	Received ※ 08 June 2022 — Revised ※ 14 June 2022 — Accepted ※ 22 June 2022 — Issue date ※ 09 July 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPOTK058	Experimental Study of the Transverse Mode Coupling Instability with Space-Charge at the CERN SPS	2193
	X. Buffat, H. Bartosik CERN, Meyrin, Switzerland
	Past studies on the Transverse Mode Coupling Instability (TMCI) suggested that it can be suppressed in the presence of space-charge forces. Recent developments in this field show that for higher strength, space-charge forces leads to other types of instabilities. We investigate the characteristics of these instabilities by means of stability threshold measurements at the CERN SPS for various intensities, longitudinal and transverse emittances. These observations are compared to numerical tracking simulations.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOTK058
About •	Received ※ 03 June 2022 — Accepted ※ 15 June 2022 — Issue date ※ 18 June 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

Measurements of Collective Effects Related to Beam Coupling Impedance at SIRIUS

34

F.H. de Sá, M.B. Alves, L. Liu
LNLS, Campinas, Brazil

Sirius is the new storage-ring-based 4th generation synchrotron light source built and operated by the Brazilian Synchrotron Light Laboratory (LNLS) at the Brazilian Center for Research in Energy and Materials (CNPEM). In ultralow emittance storage rings such as Sirius, the small radius of the vacuum chamber gives rise to strong beam coupling impedances which significantly alter the stored beam dynamics. In this work, we present the single-bunch measurements made so far to characterize such effects and compare the results with those simulated using the impedance budget built during the storage ring design.

Slides MOOYSP2 [2.496 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOOYSP2

About •

Received ※ 08 June 2022 — Accepted ※ 15 June 2022 — Issue date ※ 20 June 2022

Cite •

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

WEPOTK046

Improved Longitudinal Performance of the LHC Beam in the CERN PS

2165

H. Damerau, V.D. Desquiens, A. Huschauer, A. Jibar, A. Lasheen, B. Mikulec, M. Morvillo, C. Rossi, B.J. Woolley
CERN, Meyrin, Switzerland

At the end of the 2018 run the intensity target for the High-Luminosity LHC (HL-LHC) had just been reached at extraction from the Proton Synchrotron (PS). In the framework of the LHC Injectors Upgrade (LIU) project additional RF improvements have been implemented during the 2019/2020 long shutdown (LS2), mainly impacting the impedance of the 10 MHz, 40 MHz, and 80 MHz RF systems. With the upgraded injection energy of 2 GeV (kinetic), also the intermediate plateau energy for RF manipulations has been increased. Following a campaign of beam studies throughout the 2021 run, a bunch intensity of up to 2.9·10¹¹ p/b in trains of 72 bunches is achieved with the required longitudinal beam quality, surpassing the LIU target of 2.6·10¹¹ p/b. The threshold of longitudinal quadrupolar coupled-bunch instabilities is increased during acceleration, but they are again observed at the flat-top. While dipolar coupled-bunch oscillations are well damped by a dedicated feedback system, the quadrupolar modes are suppressed by operating a 40 MHz system as an active higher-harmonic Landau cavity. The main commissioning steps are outlined, together with the key contributions to the improved beam performance.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOTK046

About •

Received ※ 07 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 16 June 2022

Cite •

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

WEPOTK055

Beam Lifetime Measurements in Sirius Storage Ring

2186

SUSPMF072

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

M.B. Alves, L. Liu, X.R. Resende, F.H. de Sá
LNLS, Campinas, Brazil

SIRIUS is the new storage ring-based 4th generation synchrotron light source built and operated by the Brazilian Synchrotron Light Laboratory (LNLS) at the Brazilian Center for Research in Energy and Materials (CNPEM). In ultralow emittance storage rings such as SIRIUS, the dominant contribution to the beam lifetime is due to large angle scattering between electrons within the same bunch, namely the Touschek effect. We used the strategy of storing two bunches simultaneously with different currents to measure their Touschek lifetime independently of other contributions, such as gas scattering. The measurements were carried out in different conditions of bunch current and RF voltage to compare the experimental results with those expected from theory and simulations for SIRIUS.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOTK055

About •

Received ※ 08 June 2022 — Accepted ※ 15 June 2022 — Issue date ※ 24 June 2022

Cite •

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

WEPOTK057

Towards Direct Detection of the Shape of CSR Pulses with Fast THz Detectors

2190

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

Funding: We acknowledge in part support by the Helmholtz President’s strategic fund IVF "Plasma accelerators". This work is funded in part by the BMBF contract number: 05K19VKD.
Coherent synchrotron radiation (CSR) is emitted when the emitting structure is equal to or smaller than the observed wavelength. Consequently, these pulses are very short and most detectors respond with their impulse response, regardless of the pulse length and shape. Here we present single-shot measurements performed at the Karlsruhe Research Accelerator (KARA) using a fast real-time oscilloscope and Schottky barrier detectors sensitive in the sub-THz range. The time response of this setup to CSR pulses emitted by electron bunches during the microbunching instability is shown to be sensitive to the shape of the electron bunch. Our results show how, in the future, the shape of electron bunches can be directly measured using a straightforward setup.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOTK057

About •

Received ※ 08 June 2022 — Revised ※ 14 June 2022 — Accepted ※ 22 June 2022 — Issue date ※ 09 July 2022

Cite •

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

WEPOTK058

Experimental Study of the Transverse Mode Coupling Instability with Space-Charge at the CERN SPS

2193

X. Buffat, H. Bartosik
CERN, Meyrin, Switzerland

Past studies on the Transverse Mode Coupling Instability (TMCI) suggested that it can be suppressed in the presence of space-charge forces. Recent developments in this field show that for higher strength, space-charge forces leads to other types of instabilities. We investigate the characteristics of these instabilities by means of stability threshold measurements at the CERN SPS for various intensities, longitudinal and transverse emittances. These observations are compared to numerical tracking simulations.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOTK058

About •

Received ※ 03 June 2022 — Accepted ※ 15 June 2022 — Issue date ※ 18 June 2022

Cite •

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