IPAC2022 - Classification: MC5: Beam Dynamics and EM Fields / D04: Beam Coupling Impedance - Theory, Simulations, Measurements, Code Developments

Paper	Title	Page
WEOZSP2	Suppression of Crab Cavity Noise Induced Emittance Growth by Transverse Beam Coupling Impedance	1659
SUSPMF068	use link to see paper's listing under its alternate paper code
	N. Triantafyllou, A. Wolski The University of Liverpool, Liverpool, United Kingdom F. Antoniou, H. Bartosik, P. Baudrenghien, X. Buffat, R. Calaga, Y. Papaphilippou CERN, Meyrin, Switzerland T. Mastoridis CalPoly, San Luis Obispo, California, USA
	Crab Cavities are a key component of the High Luminosity LHC (HL-LHC) upgrade, as they aim to minimize the luminosity reduction caused by the crossing angle. Two superconducting crab cavities were installed in the Super Proton Synchrotron (SPS) at CERN in 2018 to test their operation in a proton machine for the first time. An important point to consider is the increase in transverse emittance induced by noise in the Low-Level RF (LLRF) system. During the first experimental campaign in 2018, the measured emittance growth was found to be a factor of 4 lower than predicted by the available analytical models. In this report, the effects of transverse beam impedance in the presence of CC LLRF noise on transverse emittance growth are presented and the results of the second experimental campaign, which took place in the SPS in 2021, are discussed.
	Slides WEOZSP2 [2.694 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEOZSP2
About •	Received ※ 08 June 2022 — Revised ※ 12 June 2022 — Accepted ※ 14 June 2022 — Issue date ※ 15 June 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEOZSP3	Measurements of Radiation Fields From a Ceramic Break	1663
	Y. Shobuda, S. Hatakeyama, M. Yoshimoto JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan T. Toyama KEK, Tokai, Ibaraki, Japan
	Ceramic breaks are used in synchrotrons for many purposes. For example, they are inserted between the Multi-Wire Profile Monitor (MWPM) on the injection line at the Rapid Cycling Synchrotron (RCS) in J-PARC to completely prevent the wall currents accompanying beams from affecting the MWPM. On the other hand, from the viewpoint of suppressing beam impedances and the radiation fields from the ceramic breaks, it would be preferable that the inner surface of the ceramic break is coated with Titanium Nitride (TiN), or covered over capacitors. In this report, we measure the radiation fields from the ceramic break with and without capacitors as well as the beam profile and investigate the effect of the ceramic breaks on the measurements.
	Slides WEOZSP3 [35.441 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEOZSP3
About •	Received ※ 12 May 2022 — Revised ※ 14 June 2022 — Accepted ※ 24 June 2022 — Issue date ※ 05 July 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPOPT012	MAD-X for Future Accelerators	1858
	T.H.B. Persson, H. Burkhardt, R. De Maria, L. Deniau, E.J. Høydalsvik, A. Latina, P.K. Skowroński, R. Tomás García, L. van Riesen-Haupt CERN, Meyrin, Switzerland
	The development of MAD-X was started more than 20 years ago and it still remains the main tool for single particle dynamics for both optics design, error studies as well as for operational model-based software at CERN. In this article, we outline some of the recent development of MAD-X and plans for the future. In particular, we focus on the development of the twiss module used to calculate optics functions in MAD-X which is based on first and second order matrices. These have traditionally been calculated as an expansion around the ideal orbit. In this paper, we describe explicitly how an expansion around the closed orbit can be employed instead, in order to get more precise results. We also describe the latest development of the beam-beam long range wire compensator in MAD-X, an element that has been implemented using the aforementioned approach.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOPT012
About •	Received ※ 08 June 2022 — Revised ※ 14 June 2022 — Accepted ※ 23 June 2022 — Issue date ※ 01 July 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPOTK013	Direct Impedance Measurement of the CERN PS Booster Finemet Cavities	2064
	S.C.P. Albright, M.E. Angoletta, D. Barrientos, A. Findlay, M. Jaussi, J.C. Molendijk CERN, Meyrin, Switzerland
	Over CERN’s Long Shutdown 2, the conventional ferrite-loaded cavities of the PS Booster were replaced with wide-band Finemet-loaded cavities. The Finemet cavities bring many operational advantages, but also represent a significant broadband impedance source. The impedance is mitigated by servo loops, which suppress the induced voltage, reducing the impedance as seen by the beam. Accurately including the impedance of the cavity and the effect of the servoloops in longitudinal tracking simulations is essential to predict the performance with beam. This paper discusses the results of a measurement campaign, which is intended to give a direct measurement of the cavity impedance. Using the detected voltage and the measured beam profile, the cavity impedance can be inferred and used to improve beam dynamics modelling.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOTK013
About •	Received ※ 26 May 2022 — Revised ※ 14 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 03 July 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPOTK037	Radiation of a Particle Moving Along a Helical Trajectory in a Resistive-Wall Cylindrical Waveguide	2150
	M. Ivanyan, A. Grigoryan, B. Grigoryan, B.K. Sargsyan CANDLE SRI, Yerevan, Armenia K. Flöttmann, F. Lemery DESY, Hamburg, Germany A. Grigoryan YSU, Yerevan, Armenia
	Funding: The work was supported by the Science Committee of RA, in the frames of the research project 21T-1C239 The radiation field of a particle moving on a helical trajectory in a cylindrical waveguide with resistive walls is calculated. The deformation of the energy spectrum of radiation, as a result of the finite conductivity of the walls, is investigated.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOTK037
About •	Received ※ 31 May 2022 — Revised ※ 11 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 30 June 2022
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WEPOTK039	Radiation of a Particle Moving Along a Helical Trajectory in a Semi-Infinite Cylindrical Waveguide	2154
	M. Ivanyan, A. Grigoryan, B. Grigoryan, V.G. Khachatryan, B.K. Sargsyan CANDLE SRI, Yerevan, Armenia K. Flöttmann, F. Lemery DESY, Hamburg, Germany A. Grigoryan YSU, Yerevan, Armenia
	Funding: The work was supported by the Science Committee of RA, in the frames of the research project 21T-1C239 The radiation field of a particle which suddenly appears in an ideal waveguide and moves on a helical trajectory under the influence ofexternal magnetic fields is calculated. The shape and character of the front of the propagating wave is determined. The time dependence of radiation energy accumulated in the waveguide is investigated.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOTK039
About •	Received ※ 31 May 2022 — Revised ※ 10 June 2022 — Accepted ※ 05 July 2022 — Issue date ※ 06 July 2022
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WEPOTK050	The Report of Machine Studies Related to the Vertical Beam Size Blow-Up in SuperKEKB LER	2169
	S. Terui, H. Fukuma, Y. Funakoshi, T. Ishibashi, T. Nakamura, K. Ohmi, Y. Ohnishi, M. Tobiyama, R. Ueki KEK, Ibaraki, Japan
	In the Low Energy Ring (LER) for positrons in the SuperKEKB, a vertical beam size blow-up was observed when the bunch current was approximately 1 mA. If a beam size blow-up occurs, the design luminosity cannot be achieved. Therefore, beam size blow-ups must be pre-vented. According to calculations, the bunch current threshold of the Transverse Mode Coupling instability (TMCI) is 2 mA or more, and the observed value is 50% or smaller. This vertical beam size blow-up cannot be explained by ordinary TMCI. This paper shows that by analyzing factors such as beam oscillation, the cause of the vertical beam size blow-up was determined. The study results showed that the vertical beam size blow-up in the LER was caused by the oscillations of the -1 mode.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOTK050
About •	Received ※ 17 May 2022 — Accepted ※ 22 June 2022 — Issue date ※ 25 June 2022
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WEPOTK051	Beam Induced Power Loss Estimation of a Movable Synchrotron Light Extraction Mirror for the LHC	2173
	M. Wendt, W. Andreazza, E. Bravin, F. Guillot-Vignot CERN, Meyrin, Switzerland
	Beam instruments based on synchrotron light are an important part of the beam monitoring diagnostics suite in the Large Hadron Collider (LHC) at CERN. In frame of the high luminosity upgrade (HL-LHC) additional synchrotron light diagnostics are demanded, too many to be covered by the present Beam Synchrotron-light Radiation Telescope (BSRT), which utilizes a fixed light extraction mirror. Therefore, an additional synchrotron light diagnostics setup is under development, now with a movable mirror to extract the synchrotron light emitted solely by a superconducting LHC dipole magnet. With higher bunch intensities anticipated in the HL-LHC, the beam induced power losses, and therefore local heat dissipation, play a critical role in the design of the extraction mirror. This paper summarizes the estimation of the bunched-beam induced power losses based on numerical simulations and RF measurements on a prototype light extraction mirror.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOTK051
About •	Received ※ 06 June 2022 — Accepted ※ 14 June 2022 — Issue date ※ 15 June 2022
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WEPOTK052	Beam Coupling Impedance Study and Its Database of Siam Photon Source Storage Ring	2177
	N. Juntong, T. Chanwattana, S. Jummunt, K. Kittimanapun, T. Phimsen, W. Promdee, T. Pulampong SLRI, Nakhon Ratchasima, Thailand
	Since the Siam Photon Source (SPS) had an electron beam energy upgraded from 1.0 GeV to 1.2 GeV in 2005, the storage ring impedance measurements were done once in 2007. Two insertion magnet devices have been installed in the SPS storage ring during June to August 2013. There are several vacuum components added to the storage ring; these affect the ring impedance. Quantitative understanding of instabilities requires detailed knowledge of the impedance of the ring. For this purpose, the development of an impedance database is a necessity, where the wake potentials of each vacuum component are kept and maintained in a standard format. The self-describing data sets (SDDS) file format will be utilized to record components wake potentials. The wake potentials of each vacuum component can be obtained from a particle tracking simulation; a CST particle studio program will be used in the simulation process. The wake potentials can also be included in a beam dynamic tracking program such as ELEGANT to observe beam behaviors with these instabilities and find a curing means. The study results will be presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOTK052
About •	Received ※ 19 May 2022 — Revised ※ 13 June 2022 — Accepted ※ 14 June 2022 — Issue date ※ 25 June 2022
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WEPOTK053	Simulation of Bunch Formation for the Mu2e Experiment	2180
	K.P. Harrig, E. Prebys UCD, Davis, California, USA V.P. Nagaslaev, S.J. Werkema Fermilab, Batavia, Illinois, USA
	Funding: Grant DE-SC0019254, The U.S. Department of Energy, Office of Science and Fermi Research Alliance, LLC Contract No. DE-AC02-07CH11359 The Fermilab Recycler is an 8 GeV storage ring composed of permanent magnets that was crucial to the success of the Fermilab Tevatron Collider program. It is currently being used to slip-stack protons for the high energy neutrino program and to re-bunch protons for use in the Muon g-2 and Mu2e experiments. For the latter applications, the Recycler re-bunches each 1.6 µs "batch" from the Fermilab Booster into four 2.5 MHz bunches. For the Mu2e experiment, it is crucial that beam more than 125 ns from the nominal bunch center be suppressed by at least a factor of 1E-5. While bunch formation is currently in operation for the g-2 experiment, this out of time requirement has not been met, and the reason is not understood. This work presents a simulation of bunch formation in the Recycler, in an effort to understand the reason for this excessive out of time beam and to search for a way to reduce it.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOTK053
About •	Received ※ 30 May 2022 — Revised ※ 16 June 2022 — Accepted ※ 23 June 2022 — Issue date ※ 11 July 2022
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WEPOTK059	Suppression of Emittance Growth by a Collective Force: Van Kampen Approach	2197
	X. Buffat CERN, Meyrin, Switzerland
	In hadron synchrotrons, external sources of noise affecting the beam induce emittance growth through the mechanism of decoherence. Active feedbacks are often used to suppress this emittance growth. In the presence of beam-beam interactions, it was shown that coherent modes of oscillations with frequencies shifted outside of the incoherent spectrum significantly enhances the efficiency of the emittance growth suppression by active feedbacks. We show that the same enhancement of the emittance growth suppression may be driven by a beam coupling impedance generating a real tune shift larger than the detuning.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOTK059
About •	Received ※ 03 June 2022 — Accepted ※ 13 June 2022 — Issue date ※ 15 June 2022
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WEPOTK063	A Wireless Method to Obtain the Impedance From Scattering Parameters	2213
	C. Antuono, M. Migliorati, E. Métral, C. Zannini CERN, Meyrin, Switzerland M. Migliorati, A. Mostacci LNF-INFN, Frascati, Italy A. Mostacci Sapienza University of Rome, Rome, Italy
	The coaxial wire method is a common and appreciated choice to assess the beam coupling impedance of an accelerator element from scattering parameters. Nevertheless, the results obtained from wire measurements could be inaccurate due to the presence of the stretched conductive wire that artificially creates the conditions for the propagation of a Transverse ElectroMagnetic (TEM) mode. The aim of this work is to establish a solid technique to obtain the beam coupling impedance from electromagnetic simulations, without modifications of the device under test. In this framework, we identified a new relation to get the resistive wall beam coupling impedance of a circular chamber directly from the scattering parameters and demonstrated that it reduces to the exact theoretical expression. Furthermore, a possible generalization of the method to arbitrary cross section geometries has been studied and validated with numerical simulations.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOTK063
About •	Received ※ 07 June 2022 — Accepted ※ 13 June 2022 — Issue date ※ 20 June 2022
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WEPOMS004	Investigation of RF Heating for the Multipole Injection Kicker Installed at SOLEIL	2233
	A. Gamelin, P. Alexandre, R. Ben El Fekih, J. Da Silva Castro, M. El Ajjouri, A. Letresor, L.S. Nadolski, R. Ollier, T.S. Thoraud SOLEIL, Gif-sur-Yvette, France M. Sacko, S. Taurines Avantis Concept, SAINT-CERE, France
	During the commissioning of the new Multipole Injection Kicker (MIK) pulsed magnet at SOLEIL synchrotron, an anomalously high heating of the MIK chamber and flanges was found. To better manage the heat load, fans directed toward the MIK were added to improve the air-cooling flow. This allowed the nominal current to be reached in all operation modes while keeping reasonable temperatures on the MIK. Post-installation investigations subsequently showed that the initial estimate of the maximal heat load was in agreement with the measured temperature in several operation modes both with and without the additional fans. In this article, we present the complete study, starting from the impedance calculation to thermal simulations, and comparison with the measured data with beam.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOMS004
About •	Received ※ 18 May 2022 — Accepted ※ 16 June 2022 — Issue date ※ 24 June 2022
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WEPOMS006	Simulation of the Effect of Corrugated Structures on the Longitudinal Beam Dynamics at KARA	2241
	S. Maier, M. Brosi, A. Mochihashi, A.-S. Müller, M.J. Nasse, P. Schreiber, M. Schwarz KIT, Karlsruhe, Germany
	Funding: Supported by the DFG project 431704792 in the ANR-DFG collaboration project ULTRASYNC. S. M. acknowledge the support by the Doctoral School "Karlsruhe School of Elementary and Astroparticle Physics: Science and Technology" (KSETA). Two parallel corrugated plates will be installed at the KIT storage ring KARA (KArlsruhe Research Accelerator). This impedance manipulation structure will be used to study and eventually control the beam dynamics and the emitted coherent synchrotron radiation (CSR). In this contribution, we present the results obtained with the Vlasov-Fokker-Planck solver Inovesa showing the impedance impact of different corrugated structures on the bunch and its emitted CSR power.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOMS006
About •	Received ※ 20 May 2022 — Revised ※ 13 June 2022 — Accepted ※ 23 June 2022 — Issue date ※ 02 July 2022
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Paper

Title

Page

WEOZSP2

Suppression of Crab Cavity Noise Induced Emittance Growth by Transverse Beam Coupling Impedance

1659

SUSPMF068

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

N. Triantafyllou, A. Wolski
The University of Liverpool, Liverpool, United Kingdom
F. Antoniou, H. Bartosik, P. Baudrenghien, X. Buffat, R. Calaga, Y. Papaphilippou
CERN, Meyrin, Switzerland
T. Mastoridis
CalPoly, San Luis Obispo, California, USA

Crab Cavities are a key component of the High Luminosity LHC (HL-LHC) upgrade, as they aim to minimize the luminosity reduction caused by the crossing angle. Two superconducting crab cavities were installed in the Super Proton Synchrotron (SPS) at CERN in 2018 to test their operation in a proton machine for the first time. An important point to consider is the increase in transverse emittance induced by noise in the Low-Level RF (LLRF) system. During the first experimental campaign in 2018, the measured emittance growth was found to be a factor of 4 lower than predicted by the available analytical models. In this report, the effects of transverse beam impedance in the presence of CC LLRF noise on transverse emittance growth are presented and the results of the second experimental campaign, which took place in the SPS in 2021, are discussed.

Slides WEOZSP2 [2.694 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEOZSP2

About •

Received ※ 08 June 2022 — Revised ※ 12 June 2022 — Accepted ※ 14 June 2022 — Issue date ※ 15 June 2022

Cite •

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

WEOZSP3

Measurements of Radiation Fields From a Ceramic Break

1663

Y. Shobuda, S. Hatakeyama, M. Yoshimoto
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
T. Toyama
KEK, Tokai, Ibaraki, Japan

Ceramic breaks are used in synchrotrons for many purposes. For example, they are inserted between the Multi-Wire Profile Monitor (MWPM) on the injection line at the Rapid Cycling Synchrotron (RCS) in J-PARC to completely prevent the wall currents accompanying beams from affecting the MWPM. On the other hand, from the viewpoint of suppressing beam impedances and the radiation fields from the ceramic breaks, it would be preferable that the inner surface of the ceramic break is coated with Titanium Nitride (TiN), or covered over capacitors. In this report, we measure the radiation fields from the ceramic break with and without capacitors as well as the beam profile and investigate the effect of the ceramic breaks on the measurements.

Slides WEOZSP3 [35.441 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEOZSP3

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Received ※ 12 May 2022 — Revised ※ 14 June 2022 — Accepted ※ 24 June 2022 — Issue date ※ 05 July 2022

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

WEPOPT012

MAD-X for Future Accelerators

1858

T.H.B. Persson, H. Burkhardt, R. De Maria, L. Deniau, E.J. Høydalsvik, A. Latina, P.K. Skowroński, R. Tomás García, L. van Riesen-Haupt
CERN, Meyrin, Switzerland

The development of MAD-X was started more than 20 years ago and it still remains the main tool for single particle dynamics for both optics design, error studies as well as for operational model-based software at CERN. In this article, we outline some of the recent development of MAD-X and plans for the future. In particular, we focus on the development of the twiss module used to calculate optics functions in MAD-X which is based on first and second order matrices. These have traditionally been calculated as an expansion around the ideal orbit. In this paper, we describe explicitly how an expansion around the closed orbit can be employed instead, in order to get more precise results. We also describe the latest development of the beam-beam long range wire compensator in MAD-X, an element that has been implemented using the aforementioned approach.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOPT012

About •

Received ※ 08 June 2022 — Revised ※ 14 June 2022 — Accepted ※ 23 June 2022 — Issue date ※ 01 July 2022

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WEPOTK013

Direct Impedance Measurement of the CERN PS Booster Finemet Cavities

2064

S.C.P. Albright, M.E. Angoletta, D. Barrientos, A. Findlay, M. Jaussi, J.C. Molendijk
CERN, Meyrin, Switzerland

Over CERN’s Long Shutdown 2, the conventional ferrite-loaded cavities of the PS Booster were replaced with wide-band Finemet-loaded cavities. The Finemet cavities bring many operational advantages, but also represent a significant broadband impedance source. The impedance is mitigated by servo loops, which suppress the induced voltage, reducing the impedance as seen by the beam. Accurately including the impedance of the cavity and the effect of the servoloops in longitudinal tracking simulations is essential to predict the performance with beam. This paper discusses the results of a measurement campaign, which is intended to give a direct measurement of the cavity impedance. Using the detected voltage and the measured beam profile, the cavity impedance can be inferred and used to improve beam dynamics modelling.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOTK013

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Received ※ 26 May 2022 — Revised ※ 14 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 03 July 2022

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WEPOTK037

Radiation of a Particle Moving Along a Helical Trajectory in a Resistive-Wall Cylindrical Waveguide

2150

M. Ivanyan, A. Grigoryan, B. Grigoryan, B.K. Sargsyan
CANDLE SRI, Yerevan, Armenia
K. Flöttmann, F. Lemery
DESY, Hamburg, Germany
A. Grigoryan
YSU, Yerevan, Armenia

Funding: The work was supported by the Science Committee of RA, in the frames of the research project 21T-1C239
The radiation field of a particle moving on a helical trajectory in a cylindrical waveguide with resistive walls is calculated. The deformation of the energy spectrum of radiation, as a result of the finite conductivity of the walls, is investigated.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOTK037

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Received ※ 31 May 2022 — Revised ※ 11 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 30 June 2022

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WEPOTK039

Radiation of a Particle Moving Along a Helical Trajectory in a Semi-Infinite Cylindrical Waveguide

2154

M. Ivanyan, A. Grigoryan, B. Grigoryan, V.G. Khachatryan, B.K. Sargsyan
CANDLE SRI, Yerevan, Armenia
K. Flöttmann, F. Lemery
DESY, Hamburg, Germany
A. Grigoryan
YSU, Yerevan, Armenia

Funding: The work was supported by the Science Committee of RA, in the frames of the research project 21T-1C239
The radiation field of a particle which suddenly appears in an ideal waveguide and moves on a helical trajectory under the influence ofexternal magnetic fields is calculated. The shape and character of the front of the propagating wave is determined. The time dependence of radiation energy accumulated in the waveguide is investigated.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOTK039

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Received ※ 31 May 2022 — Revised ※ 10 June 2022 — Accepted ※ 05 July 2022 — Issue date ※ 06 July 2022

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WEPOTK050

The Report of Machine Studies Related to the Vertical Beam Size Blow-Up in SuperKEKB LER

2169

S. Terui, H. Fukuma, Y. Funakoshi, T. Ishibashi, T. Nakamura, K. Ohmi, Y. Ohnishi, M. Tobiyama, R. Ueki
KEK, Ibaraki, Japan

In the Low Energy Ring (LER) for positrons in the SuperKEKB, a vertical beam size blow-up was observed when the bunch current was approximately 1 mA. If a beam size blow-up occurs, the design luminosity cannot be achieved. Therefore, beam size blow-ups must be pre-vented. According to calculations, the bunch current threshold of the Transverse Mode Coupling instability (TMCI) is 2 mA or more, and the observed value is 50% or smaller. This vertical beam size blow-up cannot be explained by ordinary TMCI. This paper shows that by analyzing factors such as beam oscillation, the cause of the vertical beam size blow-up was determined. The study results showed that the vertical beam size blow-up in the LER was caused by the oscillations of the -1 mode.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOTK050

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Received ※ 17 May 2022 — Accepted ※ 22 June 2022 — Issue date ※ 25 June 2022

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WEPOTK051

Beam Induced Power Loss Estimation of a Movable Synchrotron Light Extraction Mirror for the LHC

2173

M. Wendt, W. Andreazza, E. Bravin, F. Guillot-Vignot
CERN, Meyrin, Switzerland

Beam instruments based on synchrotron light are an important part of the beam monitoring diagnostics suite in the Large Hadron Collider (LHC) at CERN. In frame of the high luminosity upgrade (HL-LHC) additional synchrotron light diagnostics are demanded, too many to be covered by the present Beam Synchrotron-light Radiation Telescope (BSRT), which utilizes a fixed light extraction mirror. Therefore, an additional synchrotron light diagnostics setup is under development, now with a movable mirror to extract the synchrotron light emitted solely by a superconducting LHC dipole magnet. With higher bunch intensities anticipated in the HL-LHC, the beam induced power losses, and therefore local heat dissipation, play a critical role in the design of the extraction mirror. This paper summarizes the estimation of the bunched-beam induced power losses based on numerical simulations and RF measurements on a prototype light extraction mirror.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOTK051

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Received ※ 06 June 2022 — Accepted ※ 14 June 2022 — Issue date ※ 15 June 2022

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WEPOTK052

Beam Coupling Impedance Study and Its Database of Siam Photon Source Storage Ring

2177

N. Juntong, T. Chanwattana, S. Jummunt, K. Kittimanapun, T. Phimsen, W. Promdee, T. Pulampong
SLRI, Nakhon Ratchasima, Thailand

Since the Siam Photon Source (SPS) had an electron beam energy upgraded from 1.0 GeV to 1.2 GeV in 2005, the storage ring impedance measurements were done once in 2007. Two insertion magnet devices have been installed in the SPS storage ring during June to August 2013. There are several vacuum components added to the storage ring; these affect the ring impedance. Quantitative understanding of instabilities requires detailed knowledge of the impedance of the ring. For this purpose, the development of an impedance database is a necessity, where the wake potentials of each vacuum component are kept and maintained in a standard format. The self-describing data sets (SDDS) file format will be utilized to record components wake potentials. The wake potentials of each vacuum component can be obtained from a particle tracking simulation; a CST particle studio program will be used in the simulation process. The wake potentials can also be included in a beam dynamic tracking program such as ELEGANT to observe beam behaviors with these instabilities and find a curing means. The study results will be presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOTK052

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Received ※ 19 May 2022 — Revised ※ 13 June 2022 — Accepted ※ 14 June 2022 — Issue date ※ 25 June 2022

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WEPOTK053

Simulation of Bunch Formation for the Mu2e Experiment

2180

K.P. Harrig, E. Prebys
UCD, Davis, California, USA
V.P. Nagaslaev, S.J. Werkema
Fermilab, Batavia, Illinois, USA

Funding: Grant DE-SC0019254, The U.S. Department of Energy, Office of Science and Fermi Research Alliance, LLC Contract No. DE-AC02-07CH11359
The Fermilab Recycler is an 8 GeV storage ring composed of permanent magnets that was crucial to the success of the Fermilab Tevatron Collider program. It is currently being used to slip-stack protons for the high energy neutrino program and to re-bunch protons for use in the Muon g-2 and Mu2e experiments. For the latter applications, the Recycler re-bunches each 1.6 µs "batch" from the Fermilab Booster into four 2.5 MHz bunches. For the Mu2e experiment, it is crucial that beam more than 125 ns from the nominal bunch center be suppressed by at least a factor of 1E-5. While bunch formation is currently in operation for the g-2 experiment, this out of time requirement has not been met, and the reason is not understood. This work presents a simulation of bunch formation in the Recycler, in an effort to understand the reason for this excessive out of time beam and to search for a way to reduce it.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOTK053

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Received ※ 30 May 2022 — Revised ※ 16 June 2022 — Accepted ※ 23 June 2022 — Issue date ※ 11 July 2022

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WEPOTK059

Suppression of Emittance Growth by a Collective Force: Van Kampen Approach

2197

X. Buffat
CERN, Meyrin, Switzerland

In hadron synchrotrons, external sources of noise affecting the beam induce emittance growth through the mechanism of decoherence. Active feedbacks are often used to suppress this emittance growth. In the presence of beam-beam interactions, it was shown that coherent modes of oscillations with frequencies shifted outside of the incoherent spectrum significantly enhances the efficiency of the emittance growth suppression by active feedbacks. We show that the same enhancement of the emittance growth suppression may be driven by a beam coupling impedance generating a real tune shift larger than the detuning.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOTK059

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Received ※ 03 June 2022 — Accepted ※ 13 June 2022 — Issue date ※ 15 June 2022

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WEPOTK063

A Wireless Method to Obtain the Impedance From Scattering Parameters

2213

C. Antuono, M. Migliorati, E. Métral, C. Zannini
CERN, Meyrin, Switzerland
M. Migliorati, A. Mostacci
LNF-INFN, Frascati, Italy
A. Mostacci
Sapienza University of Rome, Rome, Italy

The coaxial wire method is a common and appreciated choice to assess the beam coupling impedance of an accelerator element from scattering parameters. Nevertheless, the results obtained from wire measurements could be inaccurate due to the presence of the stretched conductive wire that artificially creates the conditions for the propagation of a Transverse ElectroMagnetic (TEM) mode. The aim of this work is to establish a solid technique to obtain the beam coupling impedance from electromagnetic simulations, without modifications of the device under test. In this framework, we identified a new relation to get the resistive wall beam coupling impedance of a circular chamber directly from the scattering parameters and demonstrated that it reduces to the exact theoretical expression. Furthermore, a possible generalization of the method to arbitrary cross section geometries has been studied and validated with numerical simulations.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOTK063

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Received ※ 07 June 2022 — Accepted ※ 13 June 2022 — Issue date ※ 20 June 2022

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WEPOMS004

Investigation of RF Heating for the Multipole Injection Kicker Installed at SOLEIL

2233

A. Gamelin, P. Alexandre, R. Ben El Fekih, J. Da Silva Castro, M. El Ajjouri, A. Letresor, L.S. Nadolski, R. Ollier, T.S. Thoraud
SOLEIL, Gif-sur-Yvette, France
M. Sacko, S. Taurines
Avantis Concept, SAINT-CERE, France

During the commissioning of the new Multipole Injection Kicker (MIK) pulsed magnet at SOLEIL synchrotron, an anomalously high heating of the MIK chamber and flanges was found. To better manage the heat load, fans directed toward the MIK were added to improve the air-cooling flow. This allowed the nominal current to be reached in all operation modes while keeping reasonable temperatures on the MIK. Post-installation investigations subsequently showed that the initial estimate of the maximal heat load was in agreement with the measured temperature in several operation modes both with and without the additional fans. In this article, we present the complete study, starting from the impedance calculation to thermal simulations, and comparison with the measured data with beam.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOMS004

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Received ※ 18 May 2022 — Accepted ※ 16 June 2022 — Issue date ※ 24 June 2022

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WEPOMS006

Simulation of the Effect of Corrugated Structures on the Longitudinal Beam Dynamics at KARA

2241

S. Maier, M. Brosi, A. Mochihashi, A.-S. Müller, M.J. Nasse, P. Schreiber, M. Schwarz
KIT, Karlsruhe, Germany

Funding: Supported by the DFG project 431704792 in the ANR-DFG collaboration project ULTRASYNC. S. M. acknowledge the support by the Doctoral School "Karlsruhe School of Elementary and Astroparticle Physics: Science and Technology" (KSETA).
Two parallel corrugated plates will be installed at the KIT storage ring KARA (KArlsruhe Research Accelerator). This impedance manipulation structure will be used to study and eventually control the beam dynamics and the emitted coherent synchrotron radiation (CSR). In this contribution, we present the results obtained with the Vlasov-Fokker-Planck solver Inovesa showing the impedance impact of different corrugated structures on the bunch and its emitted CSR power.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOMS006

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Received ※ 20 May 2022 — Revised ※ 13 June 2022 — Accepted ※ 23 June 2022 — Issue date ※ 02 July 2022

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