HB2023 - List of Keywords (impedance)

Paper	Title	Other Keywords	Page
TUA1I2	New Understanding of Longitudinal Beam Instabilities and Comparison with Measurements	synchrotron, coupling, damping, proton	45
	I. Karpov CERN, Meyrin, Switzerland
	Beam instabilities driven by broad- and narrowband impedance sources have been treated separately so far. In this contribution, we present the generalised beam stability analysis based on the concept of van Kampen modes. In the presence of broadband impedance, the loss of Landau damping (LLD) in the longitudinal plane can occur above a certain single-bunch intensity. For significantly higher intensities, the broad-band impedance can drive violent radial or azimuthal mode-coupling instabilities. We have shown that the synchrotron frequency spread due to RF field non-linearity, counter-intuitively, reduces the single-bunch instability threshold. We have also demonstrated that a multi-bunch instability driven by a narrow-band impedance source can be significantly affected by LLD when adding broad-band impedance. These findings are supported by macroparticle simulations and beam observations in the Super Proton Synchrotron and the Large Hadron Collider at CERN.
	Slides TUA1I2 [1.517 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-HB2023-TUA1I2
About •	Received ※ 01 October 2023 — Revised ※ 06 October 2023 — Accepted ※ 13 October 2023 — Issued ※ 13 October 2023
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TUA1C1	Major Longitudinal Impedance Sources in the J-PARC Main Ring	septum, cavity, operation, kicker	53
	A. Kobayashi KEK, Tokai, Ibaraki, Japan
	Beam intensity upgrade is ongoing at the J-PARC main ring. The beam instability is controlled by feedback systems in both longitudinal and transverse directions respectively. However, in recent years, microbunch structures have been observed during debunching, inducing electron cloud and transverse beam instability, which has become a problem. It is essential to identify the cause and take countermeasures. A summary of model and measurement comparisons will be reported for the major impedances RF-cavities, FX-septa, and FX-kickers. Of the five septa, two have been subjected to impedance reduction measures. The remaining three septa are of different types, but similar measures are planning.
	Slides TUA1C1 [26.758 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-HB2023-TUA1C1
About •	Received ※ 29 September 2023 — Revised ※ 06 October 2023 — Accepted ※ 11 October 2023 — Issued ※ 18 October 2023
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TUA2C2	Recent Advances in the CERN PS Impedance Model and Instability Simulations	kicker, simulation, proton, synchrotron	86
	S. Joly La Sapienza University of Rome, Rome, Italy G. Iadarola, N. Mounet, B. Salvant, C. Zannini CERN, Meyrin, Switzerland M. Migliorati INFN-Roma1, Rome, Italy
	Transverse instability growth rates in the CERN Proton Synchrotron are studied thanks to the recently updated impedance model of the machine. Using this model, macroparticle tracking simulations were performed with a new method well-suited for the slicing of short wakes, which achieves comparable performance to the originally implemented method while reducing the required number of slices by a factor of 5 to 10. Dedicated beam-based measurement campaigns were carried out to benchmark the impedance model. Until now, the model underestimated instability growth rates at injection energy. Thanks to a recent addition to the impedance model, namely the kicker magnets¿ connecting cables and their external circuits, the simulated instability growth rates are now comparable to the measured ones.
	Slides TUA2C2 [0.736 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-HB2023-TUA2C2
About •	Received ※ 28 September 2023 — Revised ※ 07 October 2023 — Accepted ※ 09 October 2023 — Issued ※ 21 October 2023
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TUC4I1	A Kicker Impedance Reduction Scheme with Diode Stack and Resistor at the RCS in J-PARC	kicker, simulation, emittance, extraction	162
	Y. Shobuda, H. Harada, P.K. Saha, T. Takayanagi, F. Tamura, T. Togashi, Y. Watanabe, K. Yamamoto, M. Yamamoto JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
	At the 3-GeV Rapid Cycling Synchrotron (RCS) within the Japan Proton Accelerator Research Complex (J-PARC), kicker impedance causes beam instability. A 1-MW beam with a large emittance can be delivered to the Material and Life Science Experimental Facility (MLF) by suppressing beam instabilities without the need for a transverse feedback system¿simply by turning off the sextuple magnets. However, we require other high-intensity and high-quality beams with smaller emittances for the Main Ring (MR). To address this, we proposed a scheme for suppressing the kicker impedance using a diode stack and resistors, which effectively reduces beam instability. Importantly, these devices have a negligible effect on the extracted beam from the RCS.
	Slides TUC4I1 [2.713 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-HB2023-TUC4I1
About •	Received ※ 26 September 2023 — Revised ※ 07 October 2023 — Accepted ※ 10 October 2023 — Issued ※ 10 October 2023
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TUC4I2	Development of an Impedance Model for the ISIS Synchrotron and Predictions for the Head-Tail Instability	kicker, simulation, synchrotron, coupling	170
	D.W. Posthuma de Boer, B.A. Orton, C.M. Warsop, R.E. Williamson STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
	ISIS is a pulsed, spallation neutron and muon source at the Rutherford Appleton Laboratory in the UK. The rapid cycling synchrotron which drives the facility accelerates 3·10¹³ protons-per-pulse from 70 to 800 MeV at 50 Hz, and delivers a mean beam power of 0.2 MW to two target stations. Beam-loss mechanisms must be understood to optimise performance and minimise equipment activation; and to develop mitigation methods for future operations and new accelerators. Substantial beam-losses are driven by a vertical head-tail instability, which has also limited beam intensity. Beam-based impedance measurements suggest the instability is driven by a low-frequency narrowband impedance, but its physical origin remains unknown. More generally, research into the nature of the instability is hindered without a detailed transverse impedance model. This paper presents a survey of vertical impedance estimates for ISIS equipment, using analytical methods, low frequency CST simulations and lab-based coil measurements. The final impedance estimate is then used as an input to a new linearised Vlasov solver, and predicted growth rates compared with previously obtained experimental results.
	Slides TUC4I2 [4.374 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-HB2023-TUC4I2
About •	Received ※ 01 October 2023 — Revised ※ 08 October 2023 — Accepted ※ 10 October 2023 — Issued ※ 31 October 2023
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TUC4C1	Beam Coupling Impedance of the Main Extraction Kickers in the CERN PS	kicker, coupling, simulation, extraction	178
	M. Neroni, M.J. Barnes, A. Lasheen, C. Vollinger CERN, Meyrin, Switzerland A. Mostacci Sapienza University of Rome, Rome, Italy B.K. Popovic ANL, Lemont, Illinois, USA
	In view of the High Luminosity (HL) upgrade of the LHC, the beam intensity must be doubled in the injector chain. To perform reliable beam dynamics simulations, the beam coupling impedance in the injectors, such as the Proton Synchrotron (PS), must be followed closely by including all contributing elements into the impedance model. The existing kicker magnets of the PS had been optimized for large kick strength and short rise/fall times, but not necessarily to minimise beam coupling impedance. Hence, unwanted beam induced voltage can build up in their electrical circuits, with an impact on the beam. The beam coupling impedances of the two main kicker magnets used for the fast extraction from PS, the KFA71 and KFA79, are extensively characterized in this study. In particular, electromagnetic simulation results for the longitudinal and transverse coupling impedance are shown. The critical impedance contributions are identified, and their effect on beam stability is discussed. Moreover, the impact of the cable terminations on the electromagnetic field pattern and possible mitigation techniques are presented, providing a complete impedance evaluation of the entire kicker installation.
	Slides TUC4C1 [2.715 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-HB2023-TUC4C1
About •	Received ※ 30 September 2023 — Revised ※ 06 October 2023 — Accepted ※ 10 October 2023 — Issued ※ 15 October 2023
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TUC4C2	Mitigating Collimation Impedance and Improving Halo Cleaning with New Optics and Settings Strategy of the HL-LHC Betatron Collimation System	optics, collimation, simulation, experiment	183
	B. Lindström, R. Bruce, X. Buffat, R. De Maria, L. Giacomel, P.D. Hermes, D. Mirarchi, N. Mounet, T.H.B. Persson, S. Redaelli, R. Tomás García, F.F. Van der Veken, A. Wegscheider CERN, Meyrin, Switzerland
	Funding: Work supported by the HL-LHC project With High Luminosity Large Hadron Collider (HL-LHC) beam intensities, there are concerns that the beam losses in the dispersion suppressors around the betatron cleaning insertion might exceed the quench limits. Furthermore, to maximize the beam lifetime it is important to reduce the impedance as much as possible. The collimators constitute one of the main sources of impedance in HL-LHC, given the need to operate with small collimator gaps. To improve this, a new optics was developed which increases the beta function in the collimation area, as well as the single pass dispersion from the primary collimators to the downstream shower absorbers. Other possible improvements from orbit bumps, to further enhance the locally generated dispersion, and from asymmetric collimator settings were also studied. The new solutions were partially tested with 6.8 TeV beams at the LHC in a dedicated machine experiment in 2022. In this paper, the new performance is reviewed and prospects for future operational deployment are discussed.
	Slides TUC4C2 [2.222 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-HB2023-TUC4C2
About •	Received ※ 01 October 2023 — Revised ※ 08 October 2023 — Accepted ※ 11 October 2023 — Issued ※ 28 October 2023
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WEA1C1	Bunch-by-bunch Tune Shift Studies for LHC-type Beams in the CERN SPS	simulation, injection, wakefield, operation	194
	I. Mases Solé, H. Bartosik, K. Paraschou, M. Schenk, C. Zannini CERN, Meyrin, Switzerland
	After the implementation of major upgrades as part of the LHC Injector Upgrade Project (LIU), the Super Proton Synchrotron (SPS) delivers high intensity bunch trains with 25 ns bunch spacing to the Large Hadron Collider (LHC). These beams are exposed to several collective effects in the SPS, such as beam coupling impedance, space charge and electron cloud, leading to relatively large bunch-by-bunch coherent and incoherent tune shifts. Tune correction to the nominal values at injection is crucial to ensure beam stability and good beam transmission. Measurements of the bunch-by-bunch coherent tune shifts have been performed under different beam conditions. In this paper, we present the measurements of the bunch-by-bunch tune shift as function of bunch intensity for trains of 72 bunches. The experimental data are compared to multiparticle tracking simulations (including other beam variants such as 8b4e beam and hybrid beams) using the SPS impedance model.
	Slides WEA1C1 [2.613 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-HB2023-WEA1C1
About •	Received ※ 29 September 2023 — Revised ※ 08 October 2023 — Accepted ※ 09 October 2023 — Issued ※ 09 October 2023
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WEC4I2	Development of Dual-harmonic RF System for CSNS-II	cavity, controls, LLRF, feedback	312
	X. Li, X. Li, W. Long, W.J. Wu, C.L. Zhang IHEP, Beijing, People’s Republic of China Y. Liu DNSC, Dongguan, People’s Republic of China B. Wu IHEP CSNS, Guangdong Province, People’s Republic of China
	The upgrade of the China Spallation Neutron Source (CSNS-II) encompasses the development of a dual har-monic RF system for the Rapid Cycling Synchrotron (RCS). The objective of this system is to achieve a maxi-mum second harmonic voltage of 100 kV. To meet this requirement, a high gradient cavity is being used in place of the traditional ferrite loaded cavity. Magnetic alloy (MA) loaded cavities, which can attain very high field gradients, have demonstrated their suitability for high-intensity proton synchrotrons. As a result, designing an RF system with MA-loaded cavities has emerged as a primary focus. Over the past decade, substantial ad-vancements have been made in the development of MA-loaded cavities at CSNS. This paper provides an overview of the RF system that incorporates the MA-loaded cavity and presents the high-power test results of the system.
	Slides WEC4I2 [6.449 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-HB2023-WEC4I2
About •	Received ※ 28 September 2023 — Revised ※ 07 October 2023 — Accepted ※ 10 October 2023 — Issued ※ 22 October 2023
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THA1I2	High-Intensity Studies on the ISIS RCS and Their Impact on the Design of ISIS-II	simulation, space-charge, operation, controls	331
	R.E. Williamson, D.J. Adams, H.V. Cavanagh, B.S. Kyle, D.W. Posthuma de Boer, H. Rafique, C.M. Warsop STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
	ISIS is the pulsed spallation neutron and muon source at the Rutherford Appleton Laboratory in the UK. Operation centres on a rapid cycling proton synchrotron (RCS) that accelerates 3·10¹³ protons per pulse from 70 MeV to 800 MeV at 50 Hz, delivering a mean beam power of 0.2 MW. As a high-intensity machine, research at ISIS is predominantly focused on understanding, minimising and controlling beam-loss, which is central to sustainable machine operation. Knowledge of beam-loss mechanisms then informs the design of future high power accelerators such as ISIS-II. This paper provides an overview of the R&D studies currently underway on the ISIS RCS and how these relate to ongoing work understanding and optimising designs for ISIS-II. In particular, recent extensive investigations into observed head-tail instabilities are summarised.
	Slides THA1I2 [10.825 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-HB2023-THA1I2
About •	Received ※ 01 October 2023 — Revised ※ 07 October 2023 — Accepted ※ 10 October 2023 — Issued ※ 18 October 2023
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THA1C1	High Intensity Beam Dynamics Challenges for HL-LHC	electron, cavity, luminosity, octupole	344
	N. Mounet, H. Bartosik, P. Baudrenghien, R. Bruce, X. Buffat, R. Calaga, R. De Maria, C.N. Droin, L. Giacomel, M. Giovannozzi, G. Iadarola, S. Kostoglou, B. Lindström, L. Mether, E. Métral, Y. Papaphilippou, K. Paraschou, S. Redaelli, G. Rumolo, B. Salvant, G. Sterbini, R. Tomás García CERN, Meyrin, Switzerland
	The High Luminosity (HL-LHC) project aims to increase the integrated luminosity of CERN’s Large Hadron Collider (LHC) by an order of magnitude compared to its initial design. This requires a large increase in bunch intensity and beam brightness compared to the first LHC runs, and hence poses serious collective-effects challenges, related in particular to electron cloud, instabilities from beam-coupling impedance, and beam-beam effects. Here we present the associated constraints and the proposed mitigation measures to achieve the baseline performance of the upgraded LHC machine. We also discuss the interplay of these mitigation measures with other aspects of the accelerator, such as the physical and dynamic aperture, machine protection, magnet imperfections, optics, and the collimation system.
	Slides THA1C1 [3.385 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-HB2023-THA1C1
About •	Received ※ 01 October 2023 — Revised ※ 10 October 2023 — Accepted ※ 12 October 2023 — Issued ※ 15 October 2023
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THAFP01	Probing Transverse Impedances in the High Frequency Range at the CERN SPS	simulation, betatron, optics, coupling	393
	E. de la Fuente, H. Bartosik, I. Mases Solé, G. Rumolo, C. Zannini CERN, Meyrin, Switzerland
	Funding: CERN The SPS transverse impedance model, which includes the major impedance contributions in the machine, can be benchmarked through measurements of the Head-Tail mode zero instability. Since the SPS works above transition energy, the head tail mode zero is unstable for negative values of chromaticity. The measured instability growth rate is proportional to the real part of the transverse impedance. Studies performed after the LHC Injectors Upgrade (LIU) showed a relevant impedance around 2 GHz with high-gamma transition optics (Q26). This paper presents the follow-up studies to probe the behavior of this beam coupling impedance contribution.
	Slides THAFP01 [2.262 MB]
	Poster THAFP01 [1.149 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-HB2023-THAFP01
About •	Received ※ 29 September 2023 — Revised ※ 05 October 2023 — Accepted ※ 10 October 2023 — Issued ※ 10 October 2023
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THAFP03	Measurement of Stability Diagram at IOTA at Fermilab	experiment, kicker, damping, pick-up	400
	M.K. Bossard, Y.K. Kim University of Chicago, Chicago, Illinois, USA R. Ainsworth, N. Eddy Fermilab, Batavia, Illinois, USA
	Funding: Fermilab Nonlinear focusing elements can enhance the stability of particle beams in high-energy colliders by means of Landau Damping, through the tune spread which is introduced. We propose an experiment at Fermilab’s Integrable Optics Test Accelerator (IOTA) to investigate the influence of nonlinear focusing elements on the transverse stability of the beam. In this experiment, we employ an anti-damper, an active transverse feedback system, as a controlled mechanism to induce coherent beam instability. By utilizing the anti-damper, we can examine the impact of the nonlinear focusing element on the beam’s transverse stability. The stability diagram, a tool used to determine the system’s stability, will be measured using a recently demonstrated method at the LHC. This measurement is carried out experimentally by selecting specific threshold gains and measuring them for a range of phases. The stability diagram is represented by gei¿ on the complex plane. The experiment at IOTA adds insight towards the stability diagram measurement method by supplying a reduced machine impedance, to investigate the impedance’s effect on the stability diagram, as well as a larger range of phase measurements.
	Slides THAFP03 [1.331 MB]
	Poster THAFP03 [1.692 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-HB2023-THAFP03
About •	Received ※ 06 October 2023 — Revised ※ 09 October 2023 — Accepted ※ 10 October 2023 — Issued ※ 12 October 2023
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THAFP05	A Wireless Method for Beam Coupling Impedance Measurements of the LHC Goniometer	cavity, coupling, simulation, scattering	407
	C. Antuono, C. Zannini CERN, Meyrin, Switzerland M. Migliorati, A. Mostacci LNF-INFN, Frascati, Italy
	The beam coupling impedance (BCI) of an accelerator component should be ideally evaluated exciting the device with the beam itself. However, this scenario is not always attainable and alternative methods must be exploited, such as the bench measurements techniques. The stretched Wire Method (WM) is a well established technique for BCI evaluations, although nowadays its limitations are well known. In particular, the stretched wire perturbs the electromagnetic boundary conditions. Therefore, the results obtained could be inaccurate, especially below the cut-off frequency of the beam pipe in the case of cavity-like structures. To overcome these limitations, efforts are being made to investigate alternative bench measurement techniques that will not require the modification of the device under test (DUT). In this framework, a wireless method has been identified and tested for a pillbox cavity. Its potential for more complex structures, such as the LHC crystal goniometer is explored.
	Slides THAFP05 [1.088 MB]
	Poster THAFP05 [1.151 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-HB2023-THAFP05
About •	Received ※ 29 September 2023 — Revised ※ 05 October 2023 — Accepted ※ 10 October 2023 — Issued ※ 11 October 2023
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THAFP10	Stripline Design of a Fast Faraday Cup for the Bunch Length Measurement at ISOLDE-ISRS	ISOL, scattering, electron, operation	426
	S. Varnasseri, I. Bustinduy, P.J. González, R. Miracoli, J.L. Muñoz ESS Bilbao, Zamudio, Spain
	In order to measure the bunch length of the beam after Multi Harmonic Buncher (MHB) of ISOLDE Superconducting Recoil Separator (ISRS) and characterize the longitudinal structure of bunches of MHB, installation of a Fast Faraday Cup (FFC) is foreseen. Several possible structures of the fast faraday cup are studied and due to timing characteristics of the beam, a microstrip design is selected as the first option. The beam is collected on the biased collector of the microstrip with a matched impedance and transferred to the RF wideband amplification system. The amplified signal then can be analyzed on the wideband oscilloscope or acquisition system to extract the bunch length and bunch timing structure with precision. The design of the microstrip FFC and primary RF measurement of the prototype are discussed in this paper.
	Slides THAFP10 [2.832 MB]
	Poster THAFP10 [0.642 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-HB2023-THAFP10
About •	Received ※ 28 September 2023 — Revised ※ 05 October 2023 — Accepted ※ 11 October 2023 — Issued ※ 11 October 2023
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THBP11	MKP-L Impedance Mitigation and Expectations for MKP-S in the CERN-SPS	kicker, coupling, shielding, extraction	466
	C. Zannini, M.J. Barnes, M.S. Beck, M. Díaz Zumel, L. Ducimetière, G. Rumolo, D. Standen, P. Trubacova CERN, Meyrin, Switzerland
	Beam coupling impedance mitigation is key in preventing intensity limitations due to beam stability issues, heating and sparking. In this framework, a very good example is the optimization of the SPS kickers beam-coupling impedance for beam-induced heating mitigation. After the optimization of the SPS extraction kickers, the SPS injection kickers became the next bottleneck for high intensity operation. This system is composed of three MKP-S tanks and one MKP-L. To accommodate LIU beam intensities, it was necessary to mitigate the beam induced heating of the MKP-L, using a shielding concept briefly reviewed in this paper. Moreover, temperature data from the 2023 run are analyzed to qualify the accuracy of the models and assess the effectiveness of the impedance mitigation. Finally, the expected limitations from the MKP-S, expected to become the new bottleneck in terms of beam induced heating, are discussed.
	Poster THBP11 [1.655 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-HB2023-THBP11
About •	Received ※ 29 September 2023 — Revised ※ 07 October 2023 — Accepted ※ 10 October 2023 — Issued ※ 24 October 2023
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THBP17	Transverse Coherent Instability Studies for the High-Energy Part of the Muon Collider Complex	collider, cavity, synchrotron, simulation	491
	D. Amorim, F. Batsch, L. Bottura, D. Calzolari, C. Carli, H. Damerau, A. Grudiev, A. Lechner, E. Métral, D. Schulte, K. Skoufaris CERN, Geneva, Switzerland A. Chancé CEA-DRF-IRFU, France T. Pieloni EPFL, Lausanne, Switzerland
	Funding: This project has received funding from the European Union¿s Research and Innovation programme under GA No 101094300 and the Swiss Accelerator Research and Technology (CHART) program (www.chart.ch). The International Muon Collider Collaboration (IMCC) is studying a 3 TeV center-of-mass muon collider ring, as well as a possible next stage at 10 TeV. Muons being 200 times heavier than electrons, limitations from synchrotron radiation are mostly suppressed, but the muon decay drives the accelerator chain design. After the muon and anti-muon bunches are produced and 6D cooled, a series of Linac, recirculating Linac and Rapid Cycling Synchrotron (RCS) quickly accelerate the bunches before the collider ring. A large number of RF cavities are required in the RCS to ensure that over 90% of the muons survive in each ring. The effects of cavities higher-order modes on transverse coherent stability have been looked at in detail, including the one of a bunch offset in the cavities, along with possible mitigation measures. In the collider ring, the decay of high-energy muons is a challenge for heat load management and radiation shielding. A tungsten liner would protect the superconducting magnet from decay products. Impedance and related beam stability have been investigated to identify the minimum vacuum chamber radius and transverse damper properties required for stable beams.
DOI •	reference for this paper ※ doi:10.18429/JACoW-HB2023-THBP17
About •	Received ※ 29 September 2023 — Revised ※ 06 October 2023 — Accepted ※ 10 October 2023 — Issued ※ 01 November 2023
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THBP37	Refining the LHC Longitudinal Impedance Model	cavity, simulation, injection, damping	559
	M. Zampetakis, T. Argyropoulos, Y. Brischetto, R. Calaga, L. Giacomel, B.E. Karlsen-Bæck, I. Karpov, I. Karpov, N. Mounet, B. Salvant, H. Timko CERN, GENEVA, Switzerland B.E. Karlsen-Bæck INFN-Roma, Roma, Italy
	Modelling the longitudinal impedance for the Large Hadron Collider (LHC) has been a long-standing effort, especially in view of its High-Luminosity (HL) upgrade. The resulting impedance model is an essential input for beam dynamics studies. Increased beam intensities in the HL-LHC era will pose new challenges like RF power limitations, beam losses at injection and coupled-bunch instabilities throughout the acceleration cycle. Starting from the existing longitudinal impedance model, effort has been made to identify the main contributing devices and improve their modelling. Loss of Landau damping (LLD) simulations are performed to investigate the dependence of the stability threshold on the completeness of the impedance model and its broad-band cut-off frequency. Plans to perform beam measurements to estimate the cut-off frequency, by investigating the LLD threshold in operation, are also discussed.
	Poster THBP37 [5.606 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-HB2023-THBP37
About •	Received ※ 01 October 2023 — Revised ※ 06 October 2023 — Accepted ※ 10 October 2023 — Issued ※ 14 October 2023
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THBP40	Mitigation Strategies for the Instabilities Induced by the Fundamental Mode of the HL-LHC Crab Cavities	cavity, feedback, betatron, optics	571
	L. Giacomel, P. Baudrenghien, X. Buffat, R. Calaga, N. Mounet CERN, Meyrin, Switzerland
	The transverse impedance is one of the potentially limiting effects for the performance of the High-Luminosity Large Hadron Collider (HL-LHC). In the current LHC, the impedance is dominated by the resistive-wall contribution of the collimators at typical bunch-spectrum frequencies, and is of broad-band nature. Nevertheless, the fundamental mode of the crab cavities, that are a vital part of the HL-LHC baseline, adds a strong and narrow-band contribution. The resulting coupled-bunch instability, which contains a strong head-tail component, requires dedicated mitigation measures, since the efficiency of the transverse damper is limited against such instabilities, and Landau damping from octupoles would not be sufficient. The efficiency and implications of various mitigation strategies, based on RF feedbacks and optics changes, are discussed, along with first measurements using crab cavity prototypes at the Super Proton Synchrotron (SPS).
	Poster THBP40 [0.461 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-HB2023-THBP40
About •	Received ※ 30 September 2023 — Revised ※ 08 October 2023 — Accepted ※ 11 October 2023 — Issued ※ 19 October 2023
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THBP42	Longitudinal Loss of Landau Damping in Double Harmonic RF Systems below Transition Energy	synchrotron, damping, space-charge, proton	575
	L. Intelisano, H. Damerau, I. Karpov CERN, Meyrin, Switzerland
	Landau damping plays a crucial role in ensuring single-bunch stability in hadron synchrotrons. In the longitudinal plane, loss of Landau damping (LLD) occurs when a coherent mode of oscillation moves out of the incoherent synchrotron frequency band. The LLD threshold is studied for a purely inductive impedance below transition energy, specifically considering the common case of double harmonic RF systems operating in counter-phase at the bunch position. The additional focusing force due to beam-induced voltage distorts the potential well, ultimately collapsing the bucket. The limiting conditions for a binomial particle distribution are calculated. Furthermore, the contribution focuses on the configuration of the higher-harmonic RF system at four times the fundamental RF frequency operating in phase. In this case, the LLD threshold shows a non-monotonic behavior with a zero threshold where the derivative of the synchrotron frequency distribution is positive. The findings are obtained employing semi-analytical calculations using the MELODY code.
	Poster THBP42 [1.710 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-HB2023-THBP42
About •	Received ※ 30 September 2023 — Revised ※ 08 October 2023 — Accepted ※ 10 October 2023 — Issued ※ 14 October 2023
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THBP45	Longitudinal Collective Effects at Beam Transfer from PS to SPS at CERN	simulation, beam-loading, injection, cavity	587
	A. Lasheen, H. Damerau, I. Karpov, G. Papotti, E.T. Vinten CERN, Meyrin, Switzerland
	The hardware upgrades of the LHC Injectors Upgrade (LIU) project at CERN were completed during the Long Shutdown 2 (2019-2021) to prepare the injectors for the beams required by the High Luminosity (HL) LHC. Doubling the bunch intensity leads to new challenges due to collective effects. Although many bottlenecks were already solved, a remaining limitation is the important loss of particles at transfer from the Proton Synchrotron (PS) to the Super Proton Synchrotron (SPS). The maximum transmission achieved since the restart in 2021 is in the order of 90%, yet leading to unnecessary activation of the SPS. The losses are distributed at various instants of the SPS cycle: fast intensity decay right after injection, slow losses along the injection plateau while waiting for multiple injections from the PS, and uncaptured beam removed at start of acceleration. In this contribution, the focus is on longitudinal aspects of transfer losses and more specifically on intensity effects during the non-adiabatic bunch shorting performed in the PS prior to extraction, as well as on the longitudinal mismatch at injection due to misaligned bunch phases in the SPS caused by transient beam loading.
DOI •	reference for this paper ※ doi:10.18429/JACoW-HB2023-THBP45
About •	Received ※ 01 October 2023 — Revised ※ 08 October 2023 — Accepted ※ 10 October 2023 — Issued ※ 15 October 2023
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THBP47	Studies on the Effect of Beam-Coupling Impedance on Schottky Spectra of Bunched Beams	simulation, synchrotron, coupling, diagnostics	595
	C. Lannoy, D. Alves, K. Łasocha, N. Mounet CERN, Meyrin, Switzerland C. Lannoy, T. Pieloni EPFL, Lausanne, Switzerland
	Schottky monitors can be used for non-invasive beam diagnostics to estimate various bunch characteristics, such as tune, chromaticity, bunch profile or synchrotron frequency distribution. However, collective effects, in particular beam-coupling impedance, can significantly affect Schottky spectra when large bunch charges are involved. In such conditions, the available interpretation methods are difficult to apply directly to the measured spectra, thus preventing the extraction of beam and machine parameters, which is possible for lower bunch charges. To study the impact of impedance on such spectra, we perform here time-domain, macro-particle simulations and apply a semi-analytical method to compute the Schottky signal for various machine and beam conditions, including those corresponding to typical physics operation at the Large Hadron Collider. This study provides preliminary interpretations of the impact of beam-coupling impedance on Schottky spectra by incorporating longitudinal and transverse resonator-like impedance models into the simulations.
	Poster THBP47 [1.133 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-HB2023-THBP47
About •	Received ※ 01 October 2023 — Revised ※ 08 October 2023 — Accepted ※ 09 October 2023 — Issued ※ 21 October 2023
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THBP49	Collimation of 400 MJ Beams at the LHC: The First Step Towards the HL-LHC Era	collimation, proton, luminosity, operation	603
	S. Redaelli, A. Abramov, D.B. Baillard, R. Bruce, R. Cai, F. Carra, M. D’Andrea, M. Di Castro, L. Giacomel, P.D. Hermes, B. Lindström, D. Mirarchi, N. Mounet, F.-X. Nuiry, A. Perillo Marcone, F.F. Van der Veken CERN, Meyrin, Switzerland R. Cai EPFL, Lausanne, Switzerland A. Vella University of Malta, Information and Communication Technology, Msida, Malta
	Funding: Work supported by the HL-LHC project. An important upgrade programme is planned for the collimation system of the CERN Large Hadron Collider (LHC) in order to meet the challenges of the upcoming High-Luminosity LHC (HL-LHC) project. A first stage of the HL-LHC upgrade was already deployed during the last LHC Long Shutdown, offering important improvements of the collimation cleaning, a significant reduction of the impedance contribution and better cleaning of collisional debris, in particular for ion-ion collisions. This upgrade provides a critical opportunity to explore the LHC intensity limits during the LHC Run 3 and can provide crucial feedback to refine upgrade plans and operational scenarios in the HL-LHC era. This paper describes the performance of the upgraded LHC collimation system that has already enabled stored-beam energies larger than 400 MJ at the unprecedented beam energy of 6.8 TeV, and reviews further upgrade plans envisaged to reach 700 MJ beams at the HL-LHC.
DOI •	reference for this paper ※ doi:10.18429/JACoW-HB2023-THBP49
About •	Received ※ 03 October 2023 — Revised ※ 08 October 2023 — Accepted ※ 09 October 2023 — Issued ※ 10 October 2023
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THBP52	A Python Package to Compute Beam-Induced Heating in Particle Accelerators and Applications	vacuum, coupling, site, wakefield	611
	L. Sito, F. Giordano, G. Rumolo, B. Salvant, C. Zannini, E. de la Fuente CERN, Meyrin, Switzerland
	High-energy particle beams interact electromagnetically with their surroundings when they travel inside an accelerator. These interactions may cause beam-induced heating of the accelerator’s components, which could eventually lead to outgassing, equipment degradation and physical damage. The expected beam-induced heating can be related to the beam coupling impedance, an electromagnetic property of every accelerator device. Accounting for beam-induced heating is crucial both at the design phase of an accelerator component and for gaining an understanding of devices¿ failures. In this paper, an in-house developed Python tool to compute beam-induced heating due to impedance is introduced. The different features and capabilities will be showcased and applied to real devices in the LHC and the injector chain.
	Poster THBP52 [0.544 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-HB2023-THBP52
About •	Received ※ 29 September 2023 — Revised ※ 06 October 2023 — Accepted ※ 09 October 2023 — Issued ※ 11 October 2023
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FRA2I1	Summary of the Working Group A: Beam Dynamics in Rings	space-charge, resonance, experiment, simulation	662
	H. Bartosik, G. Rumolo CERN, Meyrin, Switzerland J.-L. Vay LBNL, Berkeley, California, USA N. Wang IHEP, Beijing, People’s Republic of China
	The HB-2023 workshop at CERN from October 9 to 13, 2023 is the continuation of the series of workshops, which started in 2002 at FNAL and rotates every two years between America, Europe and Asia. This contribution summarises the main highlights from Working Group A, Beam Dynamics in Rings, in terms of progress and challenges in the achievement of ever higher intensity and brightness hadron beams in accelerator rings around the world.
	Slides FRA2I1 [4.325 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-HB2023-FRA2I1
About •	Received ※ 04 December 2023 — Accepted ※ 05 December 2023 — Issued ※ 01 January 2024
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FRA2I3	Summary of the Working Group C on Accelerator Systems	injection, cavity, target, laser	670
	S. Machida STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom H. Huang BNL, Upton, New York, USA P.K. Saha JAEA/J-PARC, Tokai-mura, Japan
	This is a summary of the presentations and discussions of the Accelerator System working group at the 68th ICFA Advanced Beam Dynamics Workshop on High-Intensity and High-Brightness Hadron Beams.
	Slides FRA2I3 [0.262 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-HB2023-FRA2I3
About •	Received ※ 22 November 2023 — Accepted ※ 29 November 2023 — Issued ※ 15 December 2023
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Paper

Title

Other Keywords

Page

TUA1I2

New Understanding of Longitudinal Beam Instabilities and Comparison with Measurements

synchrotron, coupling, damping, proton

45

I. Karpov
CERN, Meyrin, Switzerland

Beam instabilities driven by broad- and narrowband impedance sources have been treated separately so far. In this contribution, we present the generalised beam stability analysis based on the concept of van Kampen modes. In the presence of broadband impedance, the loss of Landau damping (LLD) in the longitudinal plane can occur above a certain single-bunch intensity. For significantly higher intensities, the broad-band impedance can drive violent radial or azimuthal mode-coupling instabilities. We have shown that the synchrotron frequency spread due to RF field non-linearity, counter-intuitively, reduces the single-bunch instability threshold. We have also demonstrated that a multi-bunch instability driven by a narrow-band impedance source can be significantly affected by LLD when adding broad-band impedance. These findings are supported by macroparticle simulations and beam observations in the Super Proton Synchrotron and the Large Hadron Collider at CERN.

Slides TUA1I2 [1.517 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-HB2023-TUA1I2

About •

Received ※ 01 October 2023 — Revised ※ 06 October 2023 — Accepted ※ 13 October 2023 — Issued ※ 13 October 2023

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TUA1C1

Major Longitudinal Impedance Sources in the J-PARC Main Ring

septum, cavity, operation, kicker

53

A. Kobayashi
KEK, Tokai, Ibaraki, Japan

Beam intensity upgrade is ongoing at the J-PARC main ring. The beam instability is controlled by feedback systems in both longitudinal and transverse directions respectively. However, in recent years, microbunch structures have been observed during debunching, inducing electron cloud and transverse beam instability, which has become a problem. It is essential to identify the cause and take countermeasures. A summary of model and measurement comparisons will be reported for the major impedances RF-cavities, FX-septa, and FX-kickers. Of the five septa, two have been subjected to impedance reduction measures. The remaining three septa are of different types, but similar measures are planning.

Slides TUA1C1 [26.758 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-HB2023-TUA1C1

About •

Received ※ 29 September 2023 — Revised ※ 06 October 2023 — Accepted ※ 11 October 2023 — Issued ※ 18 October 2023

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TUA2C2

Recent Advances in the CERN PS Impedance Model and Instability Simulations

kicker, simulation, proton, synchrotron

86

S. Joly
La Sapienza University of Rome, Rome, Italy
G. Iadarola, N. Mounet, B. Salvant, C. Zannini
CERN, Meyrin, Switzerland
M. Migliorati
INFN-Roma1, Rome, Italy

Transverse instability growth rates in the CERN Proton Synchrotron are studied thanks to the recently updated impedance model of the machine. Using this model, macroparticle tracking simulations were performed with a new method well-suited for the slicing of short wakes, which achieves comparable performance to the originally implemented method while reducing the required number of slices by a factor of 5 to 10. Dedicated beam-based measurement campaigns were carried out to benchmark the impedance model. Until now, the model underestimated instability growth rates at injection energy. Thanks to a recent addition to the impedance model, namely the kicker magnets¿ connecting cables and their external circuits, the simulated instability growth rates are now comparable to the measured ones.

Slides TUA2C2 [0.736 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-HB2023-TUA2C2

About •

Received ※ 28 September 2023 — Revised ※ 07 October 2023 — Accepted ※ 09 October 2023 — Issued ※ 21 October 2023

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TUC4I1

A Kicker Impedance Reduction Scheme with Diode Stack and Resistor at the RCS in J-PARC

kicker, simulation, emittance, extraction

162

Y. Shobuda, H. Harada, P.K. Saha, T. Takayanagi, F. Tamura, T. Togashi, Y. Watanabe, K. Yamamoto, M. Yamamoto
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan

At the 3-GeV Rapid Cycling Synchrotron (RCS) within the Japan Proton Accelerator Research Complex (J-PARC), kicker impedance causes beam instability. A 1-MW beam with a large emittance can be delivered to the Material and Life Science Experimental Facility (MLF) by suppressing beam instabilities without the need for a transverse feedback system¿simply by turning off the sextuple magnets. However, we require other high-intensity and high-quality beams with smaller emittances for the Main Ring (MR). To address this, we proposed a scheme for suppressing the kicker impedance using a diode stack and resistors, which effectively reduces beam instability. Importantly, these devices have a negligible effect on the extracted beam from the RCS.

Slides TUC4I1 [2.713 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-HB2023-TUC4I1

About •

Received ※ 26 September 2023 — Revised ※ 07 October 2023 — Accepted ※ 10 October 2023 — Issued ※ 10 October 2023

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TUC4I2

Development of an Impedance Model for the ISIS Synchrotron and Predictions for the Head-Tail Instability

kicker, simulation, synchrotron, coupling

170

D.W. Posthuma de Boer, B.A. Orton, C.M. Warsop, R.E. Williamson
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom

ISIS is a pulsed, spallation neutron and muon source at the Rutherford Appleton Laboratory in the UK. The rapid cycling synchrotron which drives the facility accelerates 3·10¹³ protons-per-pulse from 70 to 800 MeV at 50 Hz, and delivers a mean beam power of 0.2 MW to two target stations. Beam-loss mechanisms must be understood to optimise performance and minimise equipment activation; and to develop mitigation methods for future operations and new accelerators. Substantial beam-losses are driven by a vertical head-tail instability, which has also limited beam intensity. Beam-based impedance measurements suggest the instability is driven by a low-frequency narrowband impedance, but its physical origin remains unknown. More generally, research into the nature of the instability is hindered without a detailed transverse impedance model. This paper presents a survey of vertical impedance estimates for ISIS equipment, using analytical methods, low frequency CST simulations and lab-based coil measurements. The final impedance estimate is then used as an input to a new linearised Vlasov solver, and predicted growth rates compared with previously obtained experimental results.

Slides TUC4I2 [4.374 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-HB2023-TUC4I2

About •

Received ※ 01 October 2023 — Revised ※ 08 October 2023 — Accepted ※ 10 October 2023 — Issued ※ 31 October 2023

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TUC4C1

Beam Coupling Impedance of the Main Extraction Kickers in the CERN PS

kicker, coupling, simulation, extraction

178

M. Neroni, M.J. Barnes, A. Lasheen, C. Vollinger
CERN, Meyrin, Switzerland
A. Mostacci
Sapienza University of Rome, Rome, Italy
B.K. Popovic
ANL, Lemont, Illinois, USA

In view of the High Luminosity (HL) upgrade of the LHC, the beam intensity must be doubled in the injector chain. To perform reliable beam dynamics simulations, the beam coupling impedance in the injectors, such as the Proton Synchrotron (PS), must be followed closely by including all contributing elements into the impedance model. The existing kicker magnets of the PS had been optimized for large kick strength and short rise/fall times, but not necessarily to minimise beam coupling impedance. Hence, unwanted beam induced voltage can build up in their electrical circuits, with an impact on the beam. The beam coupling impedances of the two main kicker magnets used for the fast extraction from PS, the KFA71 and KFA79, are extensively characterized in this study. In particular, electromagnetic simulation results for the longitudinal and transverse coupling impedance are shown. The critical impedance contributions are identified, and their effect on beam stability is discussed. Moreover, the impact of the cable terminations on the electromagnetic field pattern and possible mitigation techniques are presented, providing a complete impedance evaluation of the entire kicker installation.

Slides TUC4C1 [2.715 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-HB2023-TUC4C1

About •

Received ※ 30 September 2023 — Revised ※ 06 October 2023 — Accepted ※ 10 October 2023 — Issued ※ 15 October 2023

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TUC4C2

Mitigating Collimation Impedance and Improving Halo Cleaning with New Optics and Settings Strategy of the HL-LHC Betatron Collimation System

optics, collimation, simulation, experiment

183

B. Lindström, R. Bruce, X. Buffat, R. De Maria, L. Giacomel, P.D. Hermes, D. Mirarchi, N. Mounet, T.H.B. Persson, S. Redaelli, R. Tomás García, F.F. Van der Veken, A. Wegscheider
CERN, Meyrin, Switzerland

Funding: Work supported by the HL-LHC project
With High Luminosity Large Hadron Collider (HL-LHC) beam intensities, there are concerns that the beam losses in the dispersion suppressors around the betatron cleaning insertion might exceed the quench limits. Furthermore, to maximize the beam lifetime it is important to reduce the impedance as much as possible. The collimators constitute one of the main sources of impedance in HL-LHC, given the need to operate with small collimator gaps. To improve this, a new optics was developed which increases the beta function in the collimation area, as well as the single pass dispersion from the primary collimators to the downstream shower absorbers. Other possible improvements from orbit bumps, to further enhance the locally generated dispersion, and from asymmetric collimator settings were also studied. The new solutions were partially tested with 6.8 TeV beams at the LHC in a dedicated machine experiment in 2022. In this paper, the new performance is reviewed and prospects for future operational deployment are discussed.

Slides TUC4C2 [2.222 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-HB2023-TUC4C2

About •

Received ※ 01 October 2023 — Revised ※ 08 October 2023 — Accepted ※ 11 October 2023 — Issued ※ 28 October 2023

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WEA1C1

Bunch-by-bunch Tune Shift Studies for LHC-type Beams in the CERN SPS

simulation, injection, wakefield, operation

194

I. Mases Solé, H. Bartosik, K. Paraschou, M. Schenk, C. Zannini
CERN, Meyrin, Switzerland

After the implementation of major upgrades as part of the LHC Injector Upgrade Project (LIU), the Super Proton Synchrotron (SPS) delivers high intensity bunch trains with 25 ns bunch spacing to the Large Hadron Collider (LHC). These beams are exposed to several collective effects in the SPS, such as beam coupling impedance, space charge and electron cloud, leading to relatively large bunch-by-bunch coherent and incoherent tune shifts. Tune correction to the nominal values at injection is crucial to ensure beam stability and good beam transmission. Measurements of the bunch-by-bunch coherent tune shifts have been performed under different beam conditions. In this paper, we present the measurements of the bunch-by-bunch tune shift as function of bunch intensity for trains of 72 bunches. The experimental data are compared to multiparticle tracking simulations (including other beam variants such as 8b4e beam and hybrid beams) using the SPS impedance model.

Slides WEA1C1 [2.613 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-HB2023-WEA1C1

About •

Received ※ 29 September 2023 — Revised ※ 08 October 2023 — Accepted ※ 09 October 2023 — Issued ※ 09 October 2023

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WEC4I2

Development of Dual-harmonic RF System for CSNS-II

cavity, controls, LLRF, feedback

312

X. Li, X. Li, W. Long, W.J. Wu, C.L. Zhang
IHEP, Beijing, People’s Republic of China
Y. Liu
DNSC, Dongguan, People’s Republic of China
B. Wu
IHEP CSNS, Guangdong Province, People’s Republic of China

The upgrade of the China Spallation Neutron Source (CSNS-II) encompasses the development of a dual har-monic RF system for the Rapid Cycling Synchrotron (RCS). The objective of this system is to achieve a maxi-mum second harmonic voltage of 100 kV. To meet this requirement, a high gradient cavity is being used in place of the traditional ferrite loaded cavity. Magnetic alloy (MA) loaded cavities, which can attain very high field gradients, have demonstrated their suitability for high-intensity proton synchrotrons. As a result, designing an RF system with MA-loaded cavities has emerged as a primary focus. Over the past decade, substantial ad-vancements have been made in the development of MA-loaded cavities at CSNS. This paper provides an overview of the RF system that incorporates the MA-loaded cavity and presents the high-power test results of the system.

Slides WEC4I2 [6.449 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-HB2023-WEC4I2

About •

Received ※ 28 September 2023 — Revised ※ 07 October 2023 — Accepted ※ 10 October 2023 — Issued ※ 22 October 2023

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THA1I2

High-Intensity Studies on the ISIS RCS and Their Impact on the Design of ISIS-II

simulation, space-charge, operation, controls

331

R.E. Williamson, D.J. Adams, H.V. Cavanagh, B.S. Kyle, D.W. Posthuma de Boer, H. Rafique, C.M. Warsop
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom

ISIS is the pulsed spallation neutron and muon source at the Rutherford Appleton Laboratory in the UK. Operation centres on a rapid cycling proton synchrotron (RCS) that accelerates 3·10¹³ protons per pulse from 70 MeV to 800 MeV at 50 Hz, delivering a mean beam power of 0.2 MW. As a high-intensity machine, research at ISIS is predominantly focused on understanding, minimising and controlling beam-loss, which is central to sustainable machine operation. Knowledge of beam-loss mechanisms then informs the design of future high power accelerators such as ISIS-II. This paper provides an overview of the R&D studies currently underway on the ISIS RCS and how these relate to ongoing work understanding and optimising designs for ISIS-II. In particular, recent extensive investigations into observed head-tail instabilities are summarised.

Slides THA1I2 [10.825 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-HB2023-THA1I2

About •

Received ※ 01 October 2023 — Revised ※ 07 October 2023 — Accepted ※ 10 October 2023 — Issued ※ 18 October 2023

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THA1C1

High Intensity Beam Dynamics Challenges for HL-LHC

electron, cavity, luminosity, octupole

344

N. Mounet, H. Bartosik, P. Baudrenghien, R. Bruce, X. Buffat, R. Calaga, R. De Maria, C.N. Droin, L. Giacomel, M. Giovannozzi, G. Iadarola, S. Kostoglou, B. Lindström, L. Mether, E. Métral, Y. Papaphilippou, K. Paraschou, S. Redaelli, G. Rumolo, B. Salvant, G. Sterbini, R. Tomás García
CERN, Meyrin, Switzerland

The High Luminosity (HL-LHC) project aims to increase the integrated luminosity of CERN’s Large Hadron Collider (LHC) by an order of magnitude compared to its initial design. This requires a large increase in bunch intensity and beam brightness compared to the first LHC runs, and hence poses serious collective-effects challenges, related in particular to electron cloud, instabilities from beam-coupling impedance, and beam-beam effects. Here we present the associated constraints and the proposed mitigation measures to achieve the baseline performance of the upgraded LHC machine. We also discuss the interplay of these mitigation measures with other aspects of the accelerator, such as the physical and dynamic aperture, machine protection, magnet imperfections, optics, and the collimation system.

Slides THA1C1 [3.385 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-HB2023-THA1C1

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Received ※ 01 October 2023 — Revised ※ 10 October 2023 — Accepted ※ 12 October 2023 — Issued ※ 15 October 2023

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THAFP01

Probing Transverse Impedances in the High Frequency Range at the CERN SPS

simulation, betatron, optics, coupling

393

E. de la Fuente, H. Bartosik, I. Mases Solé, G. Rumolo, C. Zannini
CERN, Meyrin, Switzerland

Funding: CERN
The SPS transverse impedance model, which includes the major impedance contributions in the machine, can be benchmarked through measurements of the Head-Tail mode zero instability. Since the SPS works above transition energy, the head tail mode zero is unstable for negative values of chromaticity. The measured instability growth rate is proportional to the real part of the transverse impedance. Studies performed after the LHC Injectors Upgrade (LIU) showed a relevant impedance around 2 GHz with high-gamma transition optics (Q26). This paper presents the follow-up studies to probe the behavior of this beam coupling impedance contribution.

Slides THAFP01 [2.262 MB]

Poster THAFP01 [1.149 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-HB2023-THAFP01

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Received ※ 29 September 2023 — Revised ※ 05 October 2023 — Accepted ※ 10 October 2023 — Issued ※ 10 October 2023

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THAFP03

Measurement of Stability Diagram at IOTA at Fermilab

experiment, kicker, damping, pick-up

400

M.K. Bossard, Y.K. Kim
University of Chicago, Chicago, Illinois, USA
R. Ainsworth, N. Eddy
Fermilab, Batavia, Illinois, USA

Funding: Fermilab
Nonlinear focusing elements can enhance the stability of particle beams in high-energy colliders by means of Landau Damping, through the tune spread which is introduced. We propose an experiment at Fermilab’s Integrable Optics Test Accelerator (IOTA) to investigate the influence of nonlinear focusing elements on the transverse stability of the beam. In this experiment, we employ an anti-damper, an active transverse feedback system, as a controlled mechanism to induce coherent beam instability. By utilizing the anti-damper, we can examine the impact of the nonlinear focusing element on the beam’s transverse stability. The stability diagram, a tool used to determine the system’s stability, will be measured using a recently demonstrated method at the LHC. This measurement is carried out experimentally by selecting specific threshold gains and measuring them for a range of phases. The stability diagram is represented by gei¿ on the complex plane. The experiment at IOTA adds insight towards the stability diagram measurement method by supplying a reduced machine impedance, to investigate the impedance’s effect on the stability diagram, as well as a larger range of phase measurements.

Slides THAFP03 [1.331 MB]

Poster THAFP03 [1.692 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-HB2023-THAFP03

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Received ※ 06 October 2023 — Revised ※ 09 October 2023 — Accepted ※ 10 October 2023 — Issued ※ 12 October 2023

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THAFP05

A Wireless Method for Beam Coupling Impedance Measurements of the LHC Goniometer

cavity, coupling, simulation, scattering

407

C. Antuono, C. Zannini
CERN, Meyrin, Switzerland
M. Migliorati, A. Mostacci
LNF-INFN, Frascati, Italy

The beam coupling impedance (BCI) of an accelerator component should be ideally evaluated exciting the device with the beam itself. However, this scenario is not always attainable and alternative methods must be exploited, such as the bench measurements techniques. The stretched Wire Method (WM) is a well established technique for BCI evaluations, although nowadays its limitations are well known. In particular, the stretched wire perturbs the electromagnetic boundary conditions. Therefore, the results obtained could be inaccurate, especially below the cut-off frequency of the beam pipe in the case of cavity-like structures. To overcome these limitations, efforts are being made to investigate alternative bench measurement techniques that will not require the modification of the device under test (DUT). In this framework, a wireless method has been identified and tested for a pillbox cavity. Its potential for more complex structures, such as the LHC crystal goniometer is explored.

Slides THAFP05 [1.088 MB]

Poster THAFP05 [1.151 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-HB2023-THAFP05

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Received ※ 29 September 2023 — Revised ※ 05 October 2023 — Accepted ※ 10 October 2023 — Issued ※ 11 October 2023

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THAFP10

Stripline Design of a Fast Faraday Cup for the Bunch Length Measurement at ISOLDE-ISRS

ISOL, scattering, electron, operation

426

S. Varnasseri, I. Bustinduy, P.J. González, R. Miracoli, J.L. Muñoz
ESS Bilbao, Zamudio, Spain

In order to measure the bunch length of the beam after Multi Harmonic Buncher (MHB) of ISOLDE Superconducting Recoil Separator (ISRS) and characterize the longitudinal structure of bunches of MHB, installation of a Fast Faraday Cup (FFC) is foreseen. Several possible structures of the fast faraday cup are studied and due to timing characteristics of the beam, a microstrip design is selected as the first option. The beam is collected on the biased collector of the microstrip with a matched impedance and transferred to the RF wideband amplification system. The amplified signal then can be analyzed on the wideband oscilloscope or acquisition system to extract the bunch length and bunch timing structure with precision. The design of the microstrip FFC and primary RF measurement of the prototype are discussed in this paper.

Slides THAFP10 [2.832 MB]

Poster THAFP10 [0.642 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-HB2023-THAFP10

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Received ※ 28 September 2023 — Revised ※ 05 October 2023 — Accepted ※ 11 October 2023 — Issued ※ 11 October 2023

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THBP11

MKP-L Impedance Mitigation and Expectations for MKP-S in the CERN-SPS

kicker, coupling, shielding, extraction

466

C. Zannini, M.J. Barnes, M.S. Beck, M. Díaz Zumel, L. Ducimetière, G. Rumolo, D. Standen, P. Trubacova
CERN, Meyrin, Switzerland

Beam coupling impedance mitigation is key in preventing intensity limitations due to beam stability issues, heating and sparking. In this framework, a very good example is the optimization of the SPS kickers beam-coupling impedance for beam-induced heating mitigation. After the optimization of the SPS extraction kickers, the SPS injection kickers became the next bottleneck for high intensity operation. This system is composed of three MKP-S tanks and one MKP-L. To accommodate LIU beam intensities, it was necessary to mitigate the beam induced heating of the MKP-L, using a shielding concept briefly reviewed in this paper. Moreover, temperature data from the 2023 run are analyzed to qualify the accuracy of the models and assess the effectiveness of the impedance mitigation. Finally, the expected limitations from the MKP-S, expected to become the new bottleneck in terms of beam induced heating, are discussed.

Poster THBP11 [1.655 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-HB2023-THBP11

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Received ※ 29 September 2023 — Revised ※ 07 October 2023 — Accepted ※ 10 October 2023 — Issued ※ 24 October 2023

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THBP17

Transverse Coherent Instability Studies for the High-Energy Part of the Muon Collider Complex

collider, cavity, synchrotron, simulation

491

D. Amorim, F. Batsch, L. Bottura, D. Calzolari, C. Carli, H. Damerau, A. Grudiev, A. Lechner, E. Métral, D. Schulte, K. Skoufaris
CERN, Geneva, Switzerland
A. Chancé
CEA-DRF-IRFU, France
T. Pieloni
EPFL, Lausanne, Switzerland

Funding: This project has received funding from the European Union¿s Research and Innovation programme under GA No 101094300 and the Swiss Accelerator Research and Technology (CHART) program (www.chart.ch).
The International Muon Collider Collaboration (IMCC) is studying a 3 TeV center-of-mass muon collider ring, as well as a possible next stage at 10 TeV. Muons being 200 times heavier than electrons, limitations from synchrotron radiation are mostly suppressed, but the muon decay drives the accelerator chain design. After the muon and anti-muon bunches are produced and 6D cooled, a series of Linac, recirculating Linac and Rapid Cycling Synchrotron (RCS) quickly accelerate the bunches before the collider ring. A large number of RF cavities are required in the RCS to ensure that over 90% of the muons survive in each ring. The effects of cavities higher-order modes on transverse coherent stability have been looked at in detail, including the one of a bunch offset in the cavities, along with possible mitigation measures. In the collider ring, the decay of high-energy muons is a challenge for heat load management and radiation shielding. A tungsten liner would protect the superconducting magnet from decay products. Impedance and related beam stability have been investigated to identify the minimum vacuum chamber radius and transverse damper properties required for stable beams.

DOI •

reference for this paper ※ doi:10.18429/JACoW-HB2023-THBP17

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Received ※ 29 September 2023 — Revised ※ 06 October 2023 — Accepted ※ 10 October 2023 — Issued ※ 01 November 2023

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THBP37

Refining the LHC Longitudinal Impedance Model

cavity, simulation, injection, damping

559

M. Zampetakis, T. Argyropoulos, Y. Brischetto, R. Calaga, L. Giacomel, B.E. Karlsen-Bæck, I. Karpov, I. Karpov, N. Mounet, B. Salvant, H. Timko
CERN, GENEVA, Switzerland
B.E. Karlsen-Bæck
INFN-Roma, Roma, Italy

Modelling the longitudinal impedance for the Large Hadron Collider (LHC) has been a long-standing effort, especially in view of its High-Luminosity (HL) upgrade. The resulting impedance model is an essential input for beam dynamics studies. Increased beam intensities in the HL-LHC era will pose new challenges like RF power limitations, beam losses at injection and coupled-bunch instabilities throughout the acceleration cycle. Starting from the existing longitudinal impedance model, effort has been made to identify the main contributing devices and improve their modelling. Loss of Landau damping (LLD) simulations are performed to investigate the dependence of the stability threshold on the completeness of the impedance model and its broad-band cut-off frequency. Plans to perform beam measurements to estimate the cut-off frequency, by investigating the LLD threshold in operation, are also discussed.

Poster THBP37 [5.606 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-HB2023-THBP37

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Received ※ 01 October 2023 — Revised ※ 06 October 2023 — Accepted ※ 10 October 2023 — Issued ※ 14 October 2023

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THBP40

Mitigation Strategies for the Instabilities Induced by the Fundamental Mode of the HL-LHC Crab Cavities

cavity, feedback, betatron, optics

571

L. Giacomel, P. Baudrenghien, X. Buffat, R. Calaga, N. Mounet
CERN, Meyrin, Switzerland

The transverse impedance is one of the potentially limiting effects for the performance of the High-Luminosity Large Hadron Collider (HL-LHC). In the current LHC, the impedance is dominated by the resistive-wall contribution of the collimators at typical bunch-spectrum frequencies, and is of broad-band nature. Nevertheless, the fundamental mode of the crab cavities, that are a vital part of the HL-LHC baseline, adds a strong and narrow-band contribution. The resulting coupled-bunch instability, which contains a strong head-tail component, requires dedicated mitigation measures, since the efficiency of the transverse damper is limited against such instabilities, and Landau damping from octupoles would not be sufficient. The efficiency and implications of various mitigation strategies, based on RF feedbacks and optics changes, are discussed, along with first measurements using crab cavity prototypes at the Super Proton Synchrotron (SPS).

Poster THBP40 [0.461 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-HB2023-THBP40

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Received ※ 30 September 2023 — Revised ※ 08 October 2023 — Accepted ※ 11 October 2023 — Issued ※ 19 October 2023

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THBP42

Longitudinal Loss of Landau Damping in Double Harmonic RF Systems below Transition Energy

synchrotron, damping, space-charge, proton

575

L. Intelisano, H. Damerau, I. Karpov
CERN, Meyrin, Switzerland

Landau damping plays a crucial role in ensuring single-bunch stability in hadron synchrotrons. In the longitudinal plane, loss of Landau damping (LLD) occurs when a coherent mode of oscillation moves out of the incoherent synchrotron frequency band. The LLD threshold is studied for a purely inductive impedance below transition energy, specifically considering the common case of double harmonic RF systems operating in counter-phase at the bunch position. The additional focusing force due to beam-induced voltage distorts the potential well, ultimately collapsing the bucket. The limiting conditions for a binomial particle distribution are calculated. Furthermore, the contribution focuses on the configuration of the higher-harmonic RF system at four times the fundamental RF frequency operating in phase. In this case, the LLD threshold shows a non-monotonic behavior with a zero threshold where the derivative of the synchrotron frequency distribution is positive. The findings are obtained employing semi-analytical calculations using the MELODY code.

Poster THBP42 [1.710 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-HB2023-THBP42

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Received ※ 30 September 2023 — Revised ※ 08 October 2023 — Accepted ※ 10 October 2023 — Issued ※ 14 October 2023

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THBP45

Longitudinal Collective Effects at Beam Transfer from PS to SPS at CERN

simulation, beam-loading, injection, cavity

587

A. Lasheen, H. Damerau, I. Karpov, G. Papotti, E.T. Vinten
CERN, Meyrin, Switzerland

The hardware upgrades of the LHC Injectors Upgrade (LIU) project at CERN were completed during the Long Shutdown 2 (2019-2021) to prepare the injectors for the beams required by the High Luminosity (HL) LHC. Doubling the bunch intensity leads to new challenges due to collective effects. Although many bottlenecks were already solved, a remaining limitation is the important loss of particles at transfer from the Proton Synchrotron (PS) to the Super Proton Synchrotron (SPS). The maximum transmission achieved since the restart in 2021 is in the order of 90%, yet leading to unnecessary activation of the SPS. The losses are distributed at various instants of the SPS cycle: fast intensity decay right after injection, slow losses along the injection plateau while waiting for multiple injections from the PS, and uncaptured beam removed at start of acceleration. In this contribution, the focus is on longitudinal aspects of transfer losses and more specifically on intensity effects during the non-adiabatic bunch shorting performed in the PS prior to extraction, as well as on the longitudinal mismatch at injection due to misaligned bunch phases in the SPS caused by transient beam loading.

DOI •

reference for this paper ※ doi:10.18429/JACoW-HB2023-THBP45

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Received ※ 01 October 2023 — Revised ※ 08 October 2023 — Accepted ※ 10 October 2023 — Issued ※ 15 October 2023

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THBP47

Studies on the Effect of Beam-Coupling Impedance on Schottky Spectra of Bunched Beams

simulation, synchrotron, coupling, diagnostics

595

C. Lannoy, D. Alves, K. Łasocha, N. Mounet
CERN, Meyrin, Switzerland
C. Lannoy, T. Pieloni
EPFL, Lausanne, Switzerland

Schottky monitors can be used for non-invasive beam diagnostics to estimate various bunch characteristics, such as tune, chromaticity, bunch profile or synchrotron frequency distribution. However, collective effects, in particular beam-coupling impedance, can significantly affect Schottky spectra when large bunch charges are involved. In such conditions, the available interpretation methods are difficult to apply directly to the measured spectra, thus preventing the extraction of beam and machine parameters, which is possible for lower bunch charges. To study the impact of impedance on such spectra, we perform here time-domain, macro-particle simulations and apply a semi-analytical method to compute the Schottky signal for various machine and beam conditions, including those corresponding to typical physics operation at the Large Hadron Collider. This study provides preliminary interpretations of the impact of beam-coupling impedance on Schottky spectra by incorporating longitudinal and transverse resonator-like impedance models into the simulations.

Poster THBP47 [1.133 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-HB2023-THBP47

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Received ※ 01 October 2023 — Revised ※ 08 October 2023 — Accepted ※ 09 October 2023 — Issued ※ 21 October 2023

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THBP49

Collimation of 400 MJ Beams at the LHC: The First Step Towards the HL-LHC Era

collimation, proton, luminosity, operation

603

S. Redaelli, A. Abramov, D.B. Baillard, R. Bruce, R. Cai, F. Carra, M. D’Andrea, M. Di Castro, L. Giacomel, P.D. Hermes, B. Lindström, D. Mirarchi, N. Mounet, F.-X. Nuiry, A. Perillo Marcone, F.F. Van der Veken
CERN, Meyrin, Switzerland
R. Cai
EPFL, Lausanne, Switzerland
A. Vella
University of Malta, Information and Communication Technology, Msida, Malta

Funding: Work supported by the HL-LHC project.
An important upgrade programme is planned for the collimation system of the CERN Large Hadron Collider (LHC) in order to meet the challenges of the upcoming High-Luminosity LHC (HL-LHC) project. A first stage of the HL-LHC upgrade was already deployed during the last LHC Long Shutdown, offering important improvements of the collimation cleaning, a significant reduction of the impedance contribution and better cleaning of collisional debris, in particular for ion-ion collisions. This upgrade provides a critical opportunity to explore the LHC intensity limits during the LHC Run 3 and can provide crucial feedback to refine upgrade plans and operational scenarios in the HL-LHC era. This paper describes the performance of the upgraded LHC collimation system that has already enabled stored-beam energies larger than 400 MJ at the unprecedented beam energy of 6.8 TeV, and reviews further upgrade plans envisaged to reach 700 MJ beams at the HL-LHC.

DOI •

reference for this paper ※ doi:10.18429/JACoW-HB2023-THBP49

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Received ※ 03 October 2023 — Revised ※ 08 October 2023 — Accepted ※ 09 October 2023 — Issued ※ 10 October 2023

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THBP52

A Python Package to Compute Beam-Induced Heating in Particle Accelerators and Applications

vacuum, coupling, site, wakefield

611

L. Sito, F. Giordano, G. Rumolo, B. Salvant, C. Zannini, E. de la Fuente
CERN, Meyrin, Switzerland

High-energy particle beams interact electromagnetically with their surroundings when they travel inside an accelerator. These interactions may cause beam-induced heating of the accelerator’s components, which could eventually lead to outgassing, equipment degradation and physical damage. The expected beam-induced heating can be related to the beam coupling impedance, an electromagnetic property of every accelerator device. Accounting for beam-induced heating is crucial both at the design phase of an accelerator component and for gaining an understanding of devices¿ failures. In this paper, an in-house developed Python tool to compute beam-induced heating due to impedance is introduced. The different features and capabilities will be showcased and applied to real devices in the LHC and the injector chain.

Poster THBP52 [0.544 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-HB2023-THBP52

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Received ※ 29 September 2023 — Revised ※ 06 October 2023 — Accepted ※ 09 October 2023 — Issued ※ 11 October 2023

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FRA2I1

Summary of the Working Group A: Beam Dynamics in Rings

space-charge, resonance, experiment, simulation

662

H. Bartosik, G. Rumolo
CERN, Meyrin, Switzerland
J.-L. Vay
LBNL, Berkeley, California, USA
N. Wang
IHEP, Beijing, People’s Republic of China

The HB-2023 workshop at CERN from October 9 to 13, 2023 is the continuation of the series of workshops, which started in 2002 at FNAL and rotates every two years between America, Europe and Asia. This contribution summarises the main highlights from Working Group A, Beam Dynamics in Rings, in terms of progress and challenges in the achievement of ever higher intensity and brightness hadron beams in accelerator rings around the world.

Slides FRA2I1 [4.325 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-HB2023-FRA2I1

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Received ※ 04 December 2023 — Accepted ※ 05 December 2023 — Issued ※ 01 January 2024

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FRA2I3

Summary of the Working Group C on Accelerator Systems

injection, cavity, target, laser

670

S. Machida
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
H. Huang
BNL, Upton, New York, USA
P.K. Saha
JAEA/J-PARC, Tokai-mura, Japan

This is a summary of the presentations and discussions of the Accelerator System working group at the 68th ICFA Advanced Beam Dynamics Workshop on High-Intensity and High-Brightness Hadron Beams.

Slides FRA2I3 [0.262 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-HB2023-FRA2I3

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Received ※ 22 November 2023 — Accepted ※ 29 November 2023 — Issued ※ 15 December 2023

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