HB2023 - List of Keywords (cavity)

Paper	Title	Other Keywords	Page
MOA1I3	Intense Beam Issues in CSNS Accelerator Beam Commissioning	space-charge, MMI, sextupole, injection	16
	L. Huang, H.Y. Liu, X.H. Lu, X.B. Luo, J. Peng, L. Rao IHEP CSNS, Guangdong Province, People’s Republic of China Y.W. An, J. Chen, M.Y. Huang, Y. Li, Z.P. Li, S. Wang IHEP, Beijing, People’s Republic of China S.Y. Xu DNSC, Dongguan, People’s Republic of China
	The China Spallation Neutron Source (CSNS) consists of an 80 MeV H⁻ Linac, a 1.6 GeV Rapid Cycling Synchrotron (RCS), beam transport lines, a target station, and three spectrometers. The CSNS design beam power is 100 kW, with the capability to upgrade to 500 kW. In August 2018, CSNS was officially opened to domestic and international users. By February 2020, the beam power had reached 100 kW, and through improvements such as adding harmonic cavities, the beam power was increased to 140 kW. During the beam commissioning process, the beam loss caused by space charge effects was the most significant factor limiting the increase in beam power. Additionally, unexpected collective effects were observed, including coherent oscillations of the bunches, after the beam power reached 50 kW. Through a series of measures, the space charge effects and collective instabilities causing beam loss were effectively controlled. This paper mainly introduces the strong beam effects discovered during the beam commissioning at CSNS and their suppression methods. It also briefly discusses the research on beam space charge effects and collective effects in the beam dynamics design of CSNS-II project.
	Slides MOA1I3 [8.597 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-HB2023-MOA1I3
About •	Received ※ 01 October 2023 — Revised ※ 05 October 2023 — Accepted ※ 10 October 2023 — Issued ※ 24 October 2023
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TUA1C1	Major Longitudinal Impedance Sources in the J-PARC Main Ring	impedance, septum, 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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TUC2I2	SNS Linac Beam Dynamics: What We Understand, and What We Don’t	linac, MEBT, DTL, operation	91
	A.P. Shishlo ORNL, Oak Ridge, Tennessee, USA
	Funding: This manuscript has been authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. At this moment, the Spallation Neutron Source linac accelerates H⁻ ions to 1.05 GeV before they injected into the ring. The beam power on the target is 1.7 MW. The linac includes three main parts - a front-end with ion source, RFQ, and Medium Energy Beam Transport (MEBT) section; a normal temperature linac with Drift Tube Linac (DTL) and Coupled Cavities Linac (CCL); and superconducting linac (SCL). The linac has been in operation since it was commissioned in 2005. This talk discusses the results of beam dynamics studies, existing diagnostic devices, simulation codes and models used in analysis, development and results of linac tuning procedures, and beam loss reduction efforts performed at the SNS linac for 18 years. Considerations about future beam physics experiments and simulations software improvements are presented.
	Slides TUC2I2 [1.814 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-HB2023-TUC2I2
About •	Received ※ 29 September 2023 — Revised ※ 06 October 2023 — Accepted ※ 09 October 2023 — Issued ※ 25 October 2023
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TUA3I1	SPIRAL2 Commissioning and Operations	linac, MMI, operation, experiment	106
	A.K. Orduz, M. Di Giacomo, J.-M. Lagniel, G. Normand GANIL, Caen, France D.U. Uriot CEA-DRF-IRFU, France
	The SPIRAL2 linac is now successfully commissioned; H⁺, 4He2+, D⁺ and 18O6+ have been accelerated up to nominal parameters and 18O7+ and 40Ar14+ beams have been also accelerated up to 7 MeV/A. The main steps with 5 mA H⁺, D⁺ beams and with 0.6 mA 18O6+ are described. The general results of the commissioning of the RF, cryogenic and diagnostics systems, as well as the preliminary results of the first experiments on NFS are presented. In addition of an improvement of the matching to the linac, the tuning procedures of the 3 Medium Energy Beam Transport (MEBT) rebunchers and 26 linac SC cavities were progressively improved to reach the nominal parameters in operation, starting from the classical ¿signature matching method¿. The different cavity tuning methods developed to take into account our particular situation (very low energy and large phase extension) are described. The tools developed for an efficient linac tuning in operation, e.g. beam energy and intensity changes are also discussed.
	Slides TUA3I1 [9.358 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-HB2023-TUA3I1
About •	Received ※ 01 October 2023 — Revised ※ 06 October 2023 — Accepted ※ 10 October 2023 — Issued ※ 24 October 2023
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WEC1C1	Improvement Design of a Beam Current Monitor Based on a Passive Cavity Under Heavy Heat Load and Radiation	pick-up, target, proton, radiation	205
	P.-A. Duperrex, J.E. Bachmann, M. Rohrer, J.L. Sun PSI, Villigen PSI, Switzerland
	The High Intensity Proton Accelerator at PSI delivers a continuous proton beam of up to 2.4 mA with a maximum energy of 590 MeV to two meson production targets, M and E, and then to the spallation target. Eight meters downstream from the target E located a beam current monitor MHC5, which endure intensive scattered particles from Target E and cause large temperature variation, further induce operation and calibration problems. To address these issues, a graphite monitor was designed to replace the older aluminum one. Based on years of operation experiences of this graphite cavity, improvement design has been also considered, including beam positon pickups refinement, on-line calibration methods implementation, as well as manipulation maintenance issues. Detailed aspects of the performance of the monitor and its improvement design will be presented in this paper.
	Slides WEC1C1 [4.024 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-HB2023-WEC1C1
About •	Received ※ 01 October 2023 — Revised ※ 04 October 2023 — Accepted ※ 09 October 2023 — Issued ※ 16 October 2023
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WEA3I1	Synchronous Phases and Transit Time Factor	linac, accelerating-gradient, focusing, acceleration	241
	J.-M. Lagniel GANIL, Caen, France
	Synchronous phases (¿s) and transit time factors (T) are THE key parameters for linac designs and operations. While the couple (¿s, T) is still our way of thinking the longitudinal beam dynamics, it is important to have in mind that the original ¿Panofsky¿ definition of these parameters is no longer valid in the case of high accelerating gradients leading to high particle velocity changes and in the case of multi-gap cavities. In this case, a new (¿s, T) definition allowing to keep both acceleration and longitudinal focusing properties is proposed. Examples are given in the SPIRAL2 linac case.
	Slides WEA3I1 [2.369 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-HB2023-WEA3I1
About •	Received ※ 27 September 2023 — Revised ※ 12 October 2023 — Accepted ※ 13 October 2023 — Issued ※ 17 October 2023
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WEC3C1	Beyond 1-MW Scenario in J-Parc Rapid-Cycling Synchrotron	acceleration, operation, linac, injection	270
	K. Yamamoto, T. Morishita, K. Moriya, H. Okita, P.K. Saha, Y. Shobuda, F. Tamura, I. Yamada, M. Yamamoto JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
	The 3-GeV rapid cycling synchrotron at the Ja-pan Pro-ton Accelerator Research Complex was designed to provid 1-MW proton beams to the Material and Life Sci-ence Experimental Facility and Main Ring. Thanks to the improvement works of the accelerator system, we success-fully accelerate 1-MW beam with quite small beam loss. Currently, the beam power of RCS is limited by the lack of anode current in the RF cavity system rather than the beam loss. Recently we developed a new acceleration cavity that can accelerate a beam with less anode current. This new cavity enables us not only to reduce require-ment of the anode power supply but also to accelerate more than 1-MW beam. We have started to consider the way to achieve beyond 1-MW beam acceleration. So far, it is expected that up to 1.5-MW beam can be accelerated after replacement of the RF cavity. We have also contin-ued study to achieve more than 2 MW beam in J-PARC RCS.
	Slides WEC3C1 [2.787 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-HB2023-WEC3C1
About •	Received ※ 25 September 2023 — Revised ※ 06 October 2023 — Accepted ※ 11 October 2023 — Issued ※ 26 October 2023
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WEA4I1	Development of Non-Destructive Beam Envelope Measurements Using BPMs for Low Beta Heavy Ion Beams in SRF Cavities	simulation, emittance, quadrupole, heavy-ion	284
	T. Nishi, O. Kamigaito, N. Sakamoto, T. Watanabe, K. Yamada RIKEN Nishina Center, Wako, Japan T. Adachi RIKEN, Saitama, Japan
	Accurate measurement and control of the beam envelope are crucial issues, particularly in high-power accelerator facilities. However, the use of destructive monitors is limited to low-intensity beams. Furthermore, in the case of beam transport between superconducting cavities, these destructive monitors are avoided to prevent the generation of dust particles and outgassing. In the Superconducting RIKEN LINAC, or SRILAC [1], we utilize 8 non-destructive Beam Energy Position Monitors (BEPMs)[2] to measure beam positions and energies. Recently we are developing a method for estimating the beam envelope by combining the quadrupole moments from BEPMs, which consist of four cosine-shape electrodes, with transfer matrix[3]. While this method has been applied to electron and proton beams, it has not been practically demonstrated for heavy ion beams in beta ¿0.1 regions. By combining BEPM simulations, we are making progress toward the reproduction of experimental results, overcoming specific issues associated with low beta. This development will present the possibility of a new method for beam envelope measurement in LEBT and MEBT, especially for hadron beam facilities. [1] K. Yamada et al., in Proc. SRF2021, paper MOOFAV01(2021). [2] T. Watanabe et al., in Proc. IBIC2020, paper FRAO04 (2020). [3] R. H. Miller et al., in Proc. HEAC¿83, pp. 603¿605 (1983).
	Slides WEA4I1 [10.867 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-HB2023-WEA4I1
About •	Received ※ 12 October 2023 — Revised ※ 13 October 2023 — Accepted ※ 18 October 2023 — Issued ※ 01 November 2023
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WEC4I1	RF Systems of J-PARC Proton Synchrotrons for High-Intensity Longitudinal Beam Optimization and Handling	feedback, operation, controls, acceleration	305
	F. Tamura, R. Miyakoshi, M. Nomura, H. Okita, T. Shimada, M. Yamamoto JAEA/J-PARC, Tokai-mura, Japan K. Hara, K. Hasegawa, C. Ohmori, K. Seiya, Y. Sugiyama, M. Yoshii KEK, Tokai, Ibaraki, Japan
	The application of magnetic alloy (MA) cores to the accelerating rf cavities in high intensity proton synchrotrons was pioneered for the J-PARC synchrotrons, the RCS and MR. The MA loaded cavities can generate high accelerating voltages. The wideband frequency response of the MA cavity enables the frequency sweep to follow the velocity change of protons without the tuning loop. The dual harmonic operation, where a single cavity is driven by the superposition of the fundamental and second harmonic rf voltages, is indispensable for the longitudinal bunch shaping to alleviate the space charge effects in the RCS. These advantages of the MA cavity are also disadvantages when looking at them from a different perspective. Since the wake voltage consists of several harmonics, which can cause bucket distortion or coupled-bunch instabilities, the beam loading compensation must be multiharmonic. The operation of tubes in the final stage amplifier is not trivial when accelerating very high intensity beams; the output current is high and the anode voltageis also multiharmonic. We summarize our effort against these issues in the operation of the RCS and MR for more than 10 years.
	Slides WEC4I1 [6.932 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-HB2023-WEC4I1
About •	Received ※ 29 September 2023 — Revised ※ 07 October 2023 — Accepted ※ 10 October 2023 — Issued ※ 29 October 2023
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WEC4I2	Development of Dual-harmonic RF System for CSNS-II	controls, LLRF, feedback, impedance	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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WEC4C1	Magnetic Alloy Loaded Cavities in J-PARC and CERN	booster, synchrotron, proton, operation	316
	C. Ohmori KEK, Ibaraki, Japan M.M. Paoluzzi CERN, Meyrin, Switzerland
	Funding: This work was supported by JSPS KAKENHI Grant Number 19KK0078 and 18K11930. Magnetic Alloy loaded cavities have been used in seven synchrotrons in J-PARC and CERN. In this paper, we will review variety of the cavity technologies to satisfy the requirements for the beam acceleration, deceleration, manipulation and instability damping. This paper also contains improvements of cavity cores by magnetic annealing scheme, quality control of cores during production, the cooling methods of magnetic alloy cores: direct water cooling and indirect one using copper discs, control of cavity bandwidths from broad to narrow bands, and the ways to drive RF cavities by tube and rad-hard solid-state amplifiers.
	Slides WEC4C1 [3.371 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-HB2023-WEC4C1
About •	Received ※ 04 October 2023 — Revised ※ 07 October 2023 — Accepted ※ 10 October 2023 — Issued ※ 10 October 2023
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WEC4C2	Multiharmonic Buncher for the Isolde Superconducting Recoil Separator Project	ISOL, bunching, linac, simulation	321
	J.L. Muñoz, I. Bustinduy, P.J. González, A. Kaftoosian, L.C. Medina, S. Varnasseri ESS Bilbao, Zamudio, Spain I. Martel University of Huelva, Huelva, Spain
	Funding: This work has been supported by the European Union ¿NextGenerationEU program The ISOLDE Superconducting Recoil Separator (ISRS) is a proposal of building a very compact separator ring as an instrument in the HIE-ISOLDE facility. The injection of the HIE-ISOLDE beam into this ring requires a more compact bunch structure, so a Multi-Harmonic Buncher device is proposed for this task. The MHB will operate at a frequency of 10.128 MHz, which is a 10% of the linac frequency, and would be installed before the RFQ. The MHB is desgined as a two electrodes system, and the MHB signal, composed for the first four harmonics of the fundamental frequency, is fed into the electrodes that are connected to the central conductor of a coaxial waveguides. The full design of the MHB is presented, including electromagnetic optimization of the electrode shape, optimization of the weights of each of the harmonic contribution, mechanical and thermal design of the structure. The RF generation and electronics to power up the device are also presented. A solution that generates directly the composed signal andis then amplified by a solid state power amplifier is also presented in this contribution.
	Slides WEC4C2 [4.165 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-HB2023-WEC4C2
About •	Received ※ 29 September 2023 — Revised ※ 08 October 2023 — Accepted ※ 09 October 2023 — Issued ※ 27 October 2023
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THA1C1	High Intensity Beam Dynamics Challenges for HL-LHC	impedance, electron, 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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THA2C4	Alternating Phase Focusing Under Influence of Space Charge Defocusing	linac, focusing, heavy-ion, software	377
	S. Lauber, W.A. Barth, R. Kalleicher, M. Miski-Oglu HIM, Mainz, Germany W.A. Barth, M. Miski-Oglu, S. Yaramyshev GSI, Darmstadt, Germany W.A. Barth KPH, Mainz, Germany
	Alternating phase focusing (APF) recently emerged as a promising beam dynamics concept for accelerating bunched proton or ion beams in drift tube linear accelerators, eliminating the need for additional transverse and longitudinal focusing lenses. The performance of APF systems, similar to radio frequency quadrupoles, heavily relies on the employed focusing lattice, including the particle synchronous phase in each gap, as well as various hyperparameters such as the number of gaps, the focusing gradient, and the required beam acceptance. However, to fully utilize the cost advantages and mechanical simplicity of APF drift tube linacs, specialized software tools are necessary to streamline the accelerator development process. After successful developement of the HELIAC-APF-IH-DTL for low current and continuous wave duty cycle, this paper presents the design concepts for APF cavities tailored for high-current applications, aiming to facilitate the design and implementation of APF-based accelerators.
	Slides THA2C4 [4.986 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-HB2023-THA2C4
About •	Received ※ 06 October 2023 — Revised ※ 08 October 2023 — Accepted ※ 11 October 2023 — Issued ※ 18 October 2023
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THAFP05	A Wireless Method for Beam Coupling Impedance Measurements of the LHC Goniometer	impedance, 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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THBP01	ESS-Bilbao RFQ Power Coupler: Design, Simulations and Tests	rfq, vacuum, linac, multipactoring	433
	I. Bustinduy, A. Conde, D. Fernández-Cañoto, N. Garmendia, P.J. González, G. Harper, A. Kaftoosian, J. Martin, J.L. Muñoz ESS Bilbao, Zamudio, Spain A.P. Letchford STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
	ESS-Bilbao RFQ power coupler is presented. The RFQ operates at 352.2 MHz and will accelerate the 32 mA proton beam extracted from the ion source up to 3.0MeV. The RFQ will complete the ESS-Bilbao injector, that can be used by the ARGITU neutron source or as a stand-alone facility. The machining of the RFQ is finished, and vacuum tests as well as low power RF measurements have been carried out. The presented power coupler is a first iteration of the device, designed to be of easier and faster manufacturing than what might be needed for future upgrades of the linac. The coupler does not have active cooling and no brazing has been needed to assemble it. It can operate at the RF power required by the RFQ but at lower duty cycles. The dielectric window is made of polymeric material, so it can withhold the assembly using vacuum seals and bolts. Design and manufacturing issues are reported in the paper, as well as the RF tests that have been carried out at medium power. Multipacting calculations compared to measured values during conditioning are also reported. High power tests of the coupler have also been performed in the ISIS-FETS RFQ and are also described here.
DOI •	reference for this paper ※ doi:10.18429/JACoW-HB2023-THBP01
About •	Received ※ 29 September 2023 — Revised ※ 08 October 2023 — Accepted ※ 11 October 2023 — Issued ※ 28 October 2023
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THBP03	ESS-Bilbao RFQ Static Tuning Algorithm and Simulation	rfq, simulation, operation, neutron	440
	J.L. Muñoz, I. Bustinduy, A. Conde, N. Garmendia, P.J. González, J. Martin, V. Toyos ESS Bilbao, Zamudio, Spain
	The ESS-Bilbao RFQ operates at 352.2 MHz. The machining of the four RFQ segments has finished and the assembly and tuning operations will follow shorly. The static tuning and field flatness are provided by an array of 60 plunger tuners, distributed along the 3.2 meters length of the structure. There are four tuners per segment per quadrant, except for one of the segments where the ports are used by the power couplers. A bead-pull setup will provide the measurements of the field profiles, that will be collected in a matrix built up with the contributions of individual tuners. The conventional approach of inverting the matrix to get the optimum tuners distribution is explored, as well as additional optimization method. Particularly, a genetic optimization algorithm provides a very succesful tuning of the RFQ. The solution provided by this approach will be used as the initial configuration of the tuners before the bead-pull measurements are carried out. Additionally, static and dynamic tuning of the RFQ is studied by high performance computing simulations of the RFQ. The analysis of the in-house computational electromagnetics suite used for these tasks is also discussed in this paper.
	Poster THBP03 [2.285 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-HB2023-THBP03
About •	Received ※ 29 September 2023 — Revised ※ 08 October 2023 — Accepted ※ 10 October 2023 — Issued ※ 28 October 2023
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THBP17	Transverse Coherent Instability Studies for the High-Energy Part of the Muon Collider Complex	collider, impedance, 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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THBP29	Effects of Cavity Pre-Detuning on RF Power Transients at Injection into the LHC	simulation, injection, operation, controls	530
	B.E. Karlsen-Bæck, T. Argyropoulos, A.C. Butterworth, R. Calaga, I. Karpov, H. Timko, M. Zampetakis CERN, Meyrin, Switzerland
	At injection into the LHC, the RF system is perturbed by beam-induced voltage resulting in strong RF power transients and the instant detuning of the cavities. The automatic tuning system, however, needs time for the mechanical compensation of the resonance frequency to take place. Acting back on the beam, the transients in RF power are expected to limit the maximum injected intensity by generating unacceptable beam loss. Reducing them is therefore essential to reach the target intensity during the High Luminosity (HL) LHC era. At LHC flat bottom, the cavities are operated using the half-detuning beam-loading compensation scheme. As implemented today, the tuner control algorithm starts acting only after the injection of the first longer bunch train which causes the bunches for this injection to experience the largest power spikes. This contribution presents an adapted detuning scheme for the RF cavities before injection. It was proposed as a path to decrease the transients, hence increasing the available intensity margin for the available RF power. The expected gain is evaluated in particle tracking simulations and measurements acquired during operation.
	Poster THBP29 [3.711 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-HB2023-THBP29
About •	Received ※ 30 September 2023 — Revised ※ 08 October 2023 — Accepted ※ 10 October 2023 — Issued ※ 22 October 2023
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THBP37	Refining the LHC Longitudinal Impedance Model	impedance, 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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THBP39	Advances on LHC RF Power Limitation Studies at Injection	injection, operation, klystron, controls	567
	H. Timko, T. Argyropoulos, R. Calaga, N. Catalán Lasheras, K. Iliakis, B.E. Karlsen-Bæck, I. Karpov, M. Zampetakis CERN, Meyrin, Switzerland
	The average power consumption of the main RF system during beam injection in the High-Luminosity Large Hadron Collider is expected to be close to the maximum available klystron power. Power transients due to the mismatch of the beam and the action of control loops will exceed the available power. This paper presents the most recent estimations of the injection voltage and steady-state power needed for HL-LHC intensities, taking also beam stability into account. It summarises measurement and simulation efforts ongoing to better understand power transients and beam losses, and describes the operational margin to be taken into account for different equipment.
	Poster THBP39 [0.861 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-HB2023-THBP39
About •	Received ※ 29 September 2023 — Revised ※ 08 October 2023 — Accepted ※ 11 October 2023 — Issued ※ 20 October 2023
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THBP40	Mitigation Strategies for the Instabilities Induced by the Fundamental Mode of the HL-LHC Crab Cavities	impedance, 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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THBP43	Intensity Effects in a Chain of Muon RCSs	HOM, acceleration, wakefield, collider	579
	F. Batsch, D. Amorim, H. Damerau, A. Grudiev, I. Karpov, E. Métral, D. Schulte CERN, Meyrin, Switzerland A. Chancé CEA, Gif-sur-Yvette, France S. Udongwo Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany
	Funding: Funded by the European Union under Grant Agreement n.101094300 The muon collider offers an attractive path to a compact, multi-TeV lepton collider. However, the short muon lifetime leads to stringent requirements on the fast energy increase. While extreme energy gains in the order of several GeV per turn are crucial for a high elevated muon survival rate, ultra-short and intense bunches are needed to achieve large luminosity. The longitudinal beam dynamics of a chain of rapid cycling synchrotrons (RCS) for acceleration from around 60 GeV to several TeV is being investigated in the framework of the International Muon Collider Collaboration. Each RCS must have a distributed radio-frequency (RF) system with several hundred RF stations to establish stable synchrotron motion. In this contribution, the beam-induced voltage in each RCS is studied, assuming a single high-intensity bunch per beam in each direction and ILC-like 1.3 GHz accelerating structures. The impact of single- and multi-turn wakefields on longitudinal stability and RF power requirements is analysed with particle tracking simulations. Special attention is moreover paid to the beam power deposited into the higher-order modes of the RF cavities.
	Poster THBP43 [1.345 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-HB2023-THBP43
About •	Received ※ 29 September 2023 — Revised ※ 05 October 2023 — Accepted ※ 10 October 2023 — Issued ※ 10 October 2023
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THBP44	ImpactX Modeling of Benchmark Tests for Space Charge Validation	space-charge, focusing, emittance, proton	583
	C.E. Mitchell, M. Garten, A. Huebl, R. Lehé, J. Qiang, R.T. Sandberg, J.-L. Vay LBNL, Berkeley, California, USA
	The code ImpactX represents the next generation of the particle-in-cell code IMPACT-Z, featuring s-based symplectic tracking with 3D space charge, parallelism with GPU acceleration, adaptive mesh-refinement, and modernized language features. With such a code comes a renewed need for space charge validation using well-defined benchmarks. For this purpose, the code is continuously checked against a test suite of exactly-solvable problems. The suite includes field calculation tests, dynamical tests involving coasting or stationary beams, and beams matched to periodic focusing channels. To study the long-time multi-turn performance of the code in a more complex setting, we investigate problems involving high-intensity storage rings, such as the GSI benchmark problem for space charge induced trapping. Comparisons against existing codes are made where possible.
	Poster THBP44 [1.020 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-HB2023-THBP44
About •	Received ※ 01 October 2023 — Revised ※ 08 October 2023 — Accepted ※ 11 October 2023 — Issued ※ 26 October 2023
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THBP45	Longitudinal Collective Effects at Beam Transfer from PS to SPS at CERN	simulation, beam-loading, impedance, injection	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
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FRA1I2	Design and Beam Commissioning of Dual Harmonic RF System in CSNS RCS	injection, bunching, MMI, space-charge	633
	H.Y. Liu, L. Huang IHEP CSNS, Guangdong Province, People’s Republic of China Y. Liu DNSC, Dongguan, People’s Republic of China S. Wang, S.Y. Xu IHEP, Beijing, People’s Republic of China
	The CSNS accelerator achieved an average beam power on target of 100 kW in February 2020 and subsequently increased it to 125 kW in March 2022. Building upon this success, CSNS plans to further enhance the average beam power to 200 kW by doubling the particle number of the circulating beam in the RCS, while keeping the injection energy same. The space charge effect is a main limit for the beam intensity increase in high-power particle accelerators. By providing a second harmonic RF cavity with a harmonic number of 4, in combination with the ferrite cavity with a harmonic number of 2, the dual harmonic RF system aims to mitigate emittance increase and beam loss caused by space charge effects, thereby optimizing the longitudinal beam distribution. This paper will concentrate on the beam commissioning for the 140 kW operation subsequent to the installation of the magnetic alloy (MA) cavity. The commissioning process includes the optimization of RF parameters, beam studies, and evaluation of the beam quality and instability.
	Slides FRA1I2 [4.086 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-HB2023-FRA1I2
About •	Received ※ 30 September 2023 — Revised ※ 09 October 2023 — Accepted ※ 14 October 2023 — Issued ※ 27 October 2023
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FRA1C1	New Techniques Method for Improving the Performance of the ALPI Linac	linac, controls, dipole, quadrupole	638
	L. Bellan, C.O. Carletto, M. Comunian, E. Fagotti, M.G. Giacchini, F. Grespan, M. Montis, Y.K.F. Ong, A. Pisent INFN/LNL, Legnaro (PD), Italy
	The superconductive quarter wave cavities hadron Linac ALPI is the final acceleration stage at the Legnaro National Laboratories. It can accelerate heavy ions from carbon to uranium up to 10 MeV/u for nuclear and applied physics experiments. It is also planned to use it for re-acceleration of the radioactive ion beams for the SPES (Selective Production of Exotic Species) project. In this article we will present the innovative results obtained with swarm intelligence algorithms, in simulations and measurements. In particular, the increment of the longitudinal acceptance for RIB (Radioactive Ion Beams) acceleration, and beam orbit correction without the beam first order measurements will be discussed.
	Slides FRA1C1 [1.540 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-HB2023-FRA1C1
About •	Received ※ 01 October 2023 — Revised ※ 06 October 2023 — Accepted ※ 10 October 2023 — Issued ※ 11 October 2023
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FRA2I3	Summary of the Working Group C on Accelerator Systems	impedance, injection, 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

MOA1I3

Intense Beam Issues in CSNS Accelerator Beam Commissioning

space-charge, MMI, sextupole, injection

16

L. Huang, H.Y. Liu, X.H. Lu, X.B. Luo, J. Peng, L. Rao
IHEP CSNS, Guangdong Province, People’s Republic of China
Y.W. An, J. Chen, M.Y. Huang, Y. Li, Z.P. Li, S. Wang
IHEP, Beijing, People’s Republic of China
S.Y. Xu
DNSC, Dongguan, People’s Republic of China

The China Spallation Neutron Source (CSNS) consists of an 80 MeV H⁻ Linac, a 1.6 GeV Rapid Cycling Synchrotron (RCS), beam transport lines, a target station, and three spectrometers. The CSNS design beam power is 100 kW, with the capability to upgrade to 500 kW. In August 2018, CSNS was officially opened to domestic and international users. By February 2020, the beam power had reached 100 kW, and through improvements such as adding harmonic cavities, the beam power was increased to 140 kW. During the beam commissioning process, the beam loss caused by space charge effects was the most significant factor limiting the increase in beam power. Additionally, unexpected collective effects were observed, including coherent oscillations of the bunches, after the beam power reached 50 kW. Through a series of measures, the space charge effects and collective instabilities causing beam loss were effectively controlled. This paper mainly introduces the strong beam effects discovered during the beam commissioning at CSNS and their suppression methods. It also briefly discusses the research on beam space charge effects and collective effects in the beam dynamics design of CSNS-II project.

Slides MOA1I3 [8.597 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-HB2023-MOA1I3

About •

Received ※ 01 October 2023 — Revised ※ 05 October 2023 — Accepted ※ 10 October 2023 — Issued ※ 24 October 2023

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TUA1C1

Major Longitudinal Impedance Sources in the J-PARC Main Ring

impedance, septum, 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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TUC2I2

SNS Linac Beam Dynamics: What We Understand, and What We Don’t

linac, MEBT, DTL, operation

91

A.P. Shishlo
ORNL, Oak Ridge, Tennessee, USA

Funding: This manuscript has been authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy.
At this moment, the Spallation Neutron Source linac accelerates H⁻ ions to 1.05 GeV before they injected into the ring. The beam power on the target is 1.7 MW. The linac includes three main parts - a front-end with ion source, RFQ, and Medium Energy Beam Transport (MEBT) section; a normal temperature linac with Drift Tube Linac (DTL) and Coupled Cavities Linac (CCL); and superconducting linac (SCL). The linac has been in operation since it was commissioned in 2005. This talk discusses the results of beam dynamics studies, existing diagnostic devices, simulation codes and models used in analysis, development and results of linac tuning procedures, and beam loss reduction efforts performed at the SNS linac for 18 years. Considerations about future beam physics experiments and simulations software improvements are presented.

Slides TUC2I2 [1.814 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-HB2023-TUC2I2

About •

Received ※ 29 September 2023 — Revised ※ 06 October 2023 — Accepted ※ 09 October 2023 — Issued ※ 25 October 2023

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TUA3I1

SPIRAL2 Commissioning and Operations

linac, MMI, operation, experiment

106

A.K. Orduz, M. Di Giacomo, J.-M. Lagniel, G. Normand
GANIL, Caen, France
D.U. Uriot
CEA-DRF-IRFU, France

The SPIRAL2 linac is now successfully commissioned; H⁺, 4He2+, D⁺ and 18O6+ have been accelerated up to nominal parameters and 18O7+ and 40Ar14+ beams have been also accelerated up to 7 MeV/A. The main steps with 5 mA H⁺, D⁺ beams and with 0.6 mA 18O6+ are described. The general results of the commissioning of the RF, cryogenic and diagnostics systems, as well as the preliminary results of the first experiments on NFS are presented. In addition of an improvement of the matching to the linac, the tuning procedures of the 3 Medium Energy Beam Transport (MEBT) rebunchers and 26 linac SC cavities were progressively improved to reach the nominal parameters in operation, starting from the classical ¿signature matching method¿. The different cavity tuning methods developed to take into account our particular situation (very low energy and large phase extension) are described. The tools developed for an efficient linac tuning in operation, e.g. beam energy and intensity changes are also discussed.

Slides TUA3I1 [9.358 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-HB2023-TUA3I1

About •

Received ※ 01 October 2023 — Revised ※ 06 October 2023 — Accepted ※ 10 October 2023 — Issued ※ 24 October 2023

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WEC1C1

Improvement Design of a Beam Current Monitor Based on a Passive Cavity Under Heavy Heat Load and Radiation

pick-up, target, proton, radiation

205

P.-A. Duperrex, J.E. Bachmann, M. Rohrer, J.L. Sun
PSI, Villigen PSI, Switzerland

The High Intensity Proton Accelerator at PSI delivers a continuous proton beam of up to 2.4 mA with a maximum energy of 590 MeV to two meson production targets, M and E, and then to the spallation target. Eight meters downstream from the target E located a beam current monitor MHC5, which endure intensive scattered particles from Target E and cause large temperature variation, further induce operation and calibration problems. To address these issues, a graphite monitor was designed to replace the older aluminum one. Based on years of operation experiences of this graphite cavity, improvement design has been also considered, including beam positon pickups refinement, on-line calibration methods implementation, as well as manipulation maintenance issues. Detailed aspects of the performance of the monitor and its improvement design will be presented in this paper.

Slides WEC1C1 [4.024 MB]

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reference for this paper ※ doi:10.18429/JACoW-HB2023-WEC1C1

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Received ※ 01 October 2023 — Revised ※ 04 October 2023 — Accepted ※ 09 October 2023 — Issued ※ 16 October 2023

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WEA3I1

Synchronous Phases and Transit Time Factor

linac, accelerating-gradient, focusing, acceleration

241

J.-M. Lagniel
GANIL, Caen, France

Synchronous phases (¿s) and transit time factors (T) are THE key parameters for linac designs and operations. While the couple (¿s, T) is still our way of thinking the longitudinal beam dynamics, it is important to have in mind that the original ¿Panofsky¿ definition of these parameters is no longer valid in the case of high accelerating gradients leading to high particle velocity changes and in the case of multi-gap cavities. In this case, a new (¿s, T) definition allowing to keep both acceleration and longitudinal focusing properties is proposed. Examples are given in the SPIRAL2 linac case.

Slides WEA3I1 [2.369 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-HB2023-WEA3I1

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Received ※ 27 September 2023 — Revised ※ 12 October 2023 — Accepted ※ 13 October 2023 — Issued ※ 17 October 2023

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WEC3C1

Beyond 1-MW Scenario in J-Parc Rapid-Cycling Synchrotron

acceleration, operation, linac, injection

270

K. Yamamoto, T. Morishita, K. Moriya, H. Okita, P.K. Saha, Y. Shobuda, F. Tamura, I. Yamada, M. Yamamoto
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan

The 3-GeV rapid cycling synchrotron at the Ja-pan Pro-ton Accelerator Research Complex was designed to provid 1-MW proton beams to the Material and Life Sci-ence Experimental Facility and Main Ring. Thanks to the improvement works of the accelerator system, we success-fully accelerate 1-MW beam with quite small beam loss. Currently, the beam power of RCS is limited by the lack of anode current in the RF cavity system rather than the beam loss. Recently we developed a new acceleration cavity that can accelerate a beam with less anode current. This new cavity enables us not only to reduce require-ment of the anode power supply but also to accelerate more than 1-MW beam. We have started to consider the way to achieve beyond 1-MW beam acceleration. So far, it is expected that up to 1.5-MW beam can be accelerated after replacement of the RF cavity. We have also contin-ued study to achieve more than 2 MW beam in J-PARC RCS.

Slides WEC3C1 [2.787 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-HB2023-WEC3C1

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Received ※ 25 September 2023 — Revised ※ 06 October 2023 — Accepted ※ 11 October 2023 — Issued ※ 26 October 2023

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WEA4I1

Development of Non-Destructive Beam Envelope Measurements Using BPMs for Low Beta Heavy Ion Beams in SRF Cavities

simulation, emittance, quadrupole, heavy-ion

284

T. Nishi, O. Kamigaito, N. Sakamoto, T. Watanabe, K. Yamada
RIKEN Nishina Center, Wako, Japan
T. Adachi
RIKEN, Saitama, Japan

Accurate measurement and control of the beam envelope are crucial issues, particularly in high-power accelerator facilities. However, the use of destructive monitors is limited to low-intensity beams. Furthermore, in the case of beam transport between superconducting cavities, these destructive monitors are avoided to prevent the generation of dust particles and outgassing. In the Superconducting RIKEN LINAC, or SRILAC [1], we utilize 8 non-destructive Beam Energy Position Monitors (BEPMs)[2] to measure beam positions and energies. Recently we are developing a method for estimating the beam envelope by combining the quadrupole moments from BEPMs, which consist of four cosine-shape electrodes, with transfer matrix[3]. While this method has been applied to electron and proton beams, it has not been practically demonstrated for heavy ion beams in beta ¿0.1 regions. By combining BEPM simulations, we are making progress toward the reproduction of experimental results, overcoming specific issues associated with low beta. This development will present the possibility of a new method for beam envelope measurement in LEBT and MEBT, especially for hadron beam facilities.
[1] K. Yamada et al., in Proc. SRF2021, paper MOOFAV01(2021).
[2] T. Watanabe et al., in Proc. IBIC2020, paper FRAO04 (2020).
[3] R. H. Miller et al., in Proc. HEAC¿83, pp. 603¿605 (1983).

Slides WEA4I1 [10.867 MB]

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reference for this paper ※ doi:10.18429/JACoW-HB2023-WEA4I1

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Received ※ 12 October 2023 — Revised ※ 13 October 2023 — Accepted ※ 18 October 2023 — Issued ※ 01 November 2023

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WEC4I1

RF Systems of J-PARC Proton Synchrotrons for High-Intensity Longitudinal Beam Optimization and Handling

feedback, operation, controls, acceleration

305

F. Tamura, R. Miyakoshi, M. Nomura, H. Okita, T. Shimada, M. Yamamoto
JAEA/J-PARC, Tokai-mura, Japan
K. Hara, K. Hasegawa, C. Ohmori, K. Seiya, Y. Sugiyama, M. Yoshii
KEK, Tokai, Ibaraki, Japan

The application of magnetic alloy (MA) cores to the accelerating rf cavities in high intensity proton synchrotrons was pioneered for the J-PARC synchrotrons, the RCS and MR. The MA loaded cavities can generate high accelerating voltages. The wideband frequency response of the MA cavity enables the frequency sweep to follow the velocity change of protons without the tuning loop. The dual harmonic operation, where a single cavity is driven by the superposition of the fundamental and second harmonic rf voltages, is indispensable for the longitudinal bunch shaping to alleviate the space charge effects in the RCS. These advantages of the MA cavity are also disadvantages when looking at them from a different perspective. Since the wake voltage consists of several harmonics, which can cause bucket distortion or coupled-bunch instabilities, the beam loading compensation must be multiharmonic. The operation of tubes in the final stage amplifier is not trivial when accelerating very high intensity beams; the output current is high and the anode voltageis also multiharmonic. We summarize our effort against these issues in the operation of the RCS and MR for more than 10 years.

Slides WEC4I1 [6.932 MB]

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reference for this paper ※ doi:10.18429/JACoW-HB2023-WEC4I1

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

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WEC4I2

Development of Dual-harmonic RF System for CSNS-II

controls, LLRF, feedback, impedance

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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WEC4C1

Magnetic Alloy Loaded Cavities in J-PARC and CERN

booster, synchrotron, proton, operation

316

C. Ohmori
KEK, Ibaraki, Japan
M.M. Paoluzzi
CERN, Meyrin, Switzerland

Funding: This work was supported by JSPS KAKENHI Grant Number 19KK0078 and 18K11930.
Magnetic Alloy loaded cavities have been used in seven synchrotrons in J-PARC and CERN. In this paper, we will review variety of the cavity technologies to satisfy the requirements for the beam acceleration, deceleration, manipulation and instability damping. This paper also contains improvements of cavity cores by magnetic annealing scheme, quality control of cores during production, the cooling methods of magnetic alloy cores: direct water cooling and indirect one using copper discs, control of cavity bandwidths from broad to narrow bands, and the ways to drive RF cavities by tube and rad-hard solid-state amplifiers.

Slides WEC4C1 [3.371 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-HB2023-WEC4C1

About •

Received ※ 04 October 2023 — Revised ※ 07 October 2023 — Accepted ※ 10 October 2023 — Issued ※ 10 October 2023

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WEC4C2

Multiharmonic Buncher for the Isolde Superconducting Recoil Separator Project

ISOL, bunching, linac, simulation

321

J.L. Muñoz, I. Bustinduy, P.J. González, A. Kaftoosian, L.C. Medina, S. Varnasseri
ESS Bilbao, Zamudio, Spain
I. Martel
University of Huelva, Huelva, Spain

Funding: This work has been supported by the European Union ¿NextGenerationEU program
The ISOLDE Superconducting Recoil Separator (ISRS) is a proposal of building a very compact separator ring as an instrument in the HIE-ISOLDE facility. The injection of the HIE-ISOLDE beam into this ring requires a more compact bunch structure, so a Multi-Harmonic Buncher device is proposed for this task. The MHB will operate at a frequency of 10.128 MHz, which is a 10% of the linac frequency, and would be installed before the RFQ. The MHB is desgined as a two electrodes system, and the MHB signal, composed for the first four harmonics of the fundamental frequency, is fed into the electrodes that are connected to the central conductor of a coaxial waveguides. The full design of the MHB is presented, including electromagnetic optimization of the electrode shape, optimization of the weights of each of the harmonic contribution, mechanical and thermal design of the structure. The RF generation and electronics to power up the device are also presented. A solution that generates directly the composed signal andis then amplified by a solid state power amplifier is also presented in this contribution.

Slides WEC4C2 [4.165 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-HB2023-WEC4C2

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Received ※ 29 September 2023 — Revised ※ 08 October 2023 — Accepted ※ 09 October 2023 — Issued ※ 27 October 2023

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THA1C1

High Intensity Beam Dynamics Challenges for HL-LHC

impedance, electron, 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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THA2C4

Alternating Phase Focusing Under Influence of Space Charge Defocusing

linac, focusing, heavy-ion, software

377

S. Lauber, W.A. Barth, R. Kalleicher, M. Miski-Oglu
HIM, Mainz, Germany
W.A. Barth, M. Miski-Oglu, S. Yaramyshev
GSI, Darmstadt, Germany
W.A. Barth
KPH, Mainz, Germany

Alternating phase focusing (APF) recently emerged as a promising beam dynamics concept for accelerating bunched proton or ion beams in drift tube linear accelerators, eliminating the need for additional transverse and longitudinal focusing lenses. The performance of APF systems, similar to radio frequency quadrupoles, heavily relies on the employed focusing lattice, including the particle synchronous phase in each gap, as well as various hyperparameters such as the number of gaps, the focusing gradient, and the required beam acceptance. However, to fully utilize the cost advantages and mechanical simplicity of APF drift tube linacs, specialized software tools are necessary to streamline the accelerator development process. After successful developement of the HELIAC-APF-IH-DTL for low current and continuous wave duty cycle, this paper presents the design concepts for APF cavities tailored for high-current applications, aiming to facilitate the design and implementation of APF-based accelerators.

Slides THA2C4 [4.986 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-HB2023-THA2C4

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Received ※ 06 October 2023 — Revised ※ 08 October 2023 — Accepted ※ 11 October 2023 — Issued ※ 18 October 2023

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THAFP05

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

impedance, 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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THBP01

ESS-Bilbao RFQ Power Coupler: Design, Simulations and Tests

rfq, vacuum, linac, multipactoring

433

I. Bustinduy, A. Conde, D. Fernández-Cañoto, N. Garmendia, P.J. González, G. Harper, A. Kaftoosian, J. Martin, J.L. Muñoz
ESS Bilbao, Zamudio, Spain
A.P. Letchford
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom

ESS-Bilbao RFQ power coupler is presented. The RFQ operates at 352.2 MHz and will accelerate the 32 mA proton beam extracted from the ion source up to 3.0MeV. The RFQ will complete the ESS-Bilbao injector, that can be used by the ARGITU neutron source or as a stand-alone facility. The machining of the RFQ is finished, and vacuum tests as well as low power RF measurements have been carried out. The presented power coupler is a first iteration of the device, designed to be of easier and faster manufacturing than what might be needed for future upgrades of the linac. The coupler does not have active cooling and no brazing has been needed to assemble it. It can operate at the RF power required by the RFQ but at lower duty cycles. The dielectric window is made of polymeric material, so it can withhold the assembly using vacuum seals and bolts. Design and manufacturing issues are reported in the paper, as well as the RF tests that have been carried out at medium power. Multipacting calculations compared to measured values during conditioning are also reported. High power tests of the coupler have also been performed in the ISIS-FETS RFQ and are also described here.

DOI •

reference for this paper ※ doi:10.18429/JACoW-HB2023-THBP01

About •

Received ※ 29 September 2023 — Revised ※ 08 October 2023 — Accepted ※ 11 October 2023 — Issued ※ 28 October 2023

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THBP03

ESS-Bilbao RFQ Static Tuning Algorithm and Simulation

rfq, simulation, operation, neutron

440

J.L. Muñoz, I. Bustinduy, A. Conde, N. Garmendia, P.J. González, J. Martin, V. Toyos
ESS Bilbao, Zamudio, Spain

The ESS-Bilbao RFQ operates at 352.2 MHz. The machining of the four RFQ segments has finished and the assembly and tuning operations will follow shorly. The static tuning and field flatness are provided by an array of 60 plunger tuners, distributed along the 3.2 meters length of the structure. There are four tuners per segment per quadrant, except for one of the segments where the ports are used by the power couplers. A bead-pull setup will provide the measurements of the field profiles, that will be collected in a matrix built up with the contributions of individual tuners. The conventional approach of inverting the matrix to get the optimum tuners distribution is explored, as well as additional optimization method. Particularly, a genetic optimization algorithm provides a very succesful tuning of the RFQ. The solution provided by this approach will be used as the initial configuration of the tuners before the bead-pull measurements are carried out. Additionally, static and dynamic tuning of the RFQ is studied by high performance computing simulations of the RFQ. The analysis of the in-house computational electromagnetics suite used for these tasks is also discussed in this paper.

Poster THBP03 [2.285 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-HB2023-THBP03

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Received ※ 29 September 2023 — Revised ※ 08 October 2023 — Accepted ※ 10 October 2023 — Issued ※ 28 October 2023

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THBP17

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

collider, impedance, 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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THBP29

Effects of Cavity Pre-Detuning on RF Power Transients at Injection into the LHC

simulation, injection, operation, controls

530

B.E. Karlsen-Bæck, T. Argyropoulos, A.C. Butterworth, R. Calaga, I. Karpov, H. Timko, M. Zampetakis
CERN, Meyrin, Switzerland

At injection into the LHC, the RF system is perturbed by beam-induced voltage resulting in strong RF power transients and the instant detuning of the cavities. The automatic tuning system, however, needs time for the mechanical compensation of the resonance frequency to take place. Acting back on the beam, the transients in RF power are expected to limit the maximum injected intensity by generating unacceptable beam loss. Reducing them is therefore essential to reach the target intensity during the High Luminosity (HL) LHC era. At LHC flat bottom, the cavities are operated using the half-detuning beam-loading compensation scheme. As implemented today, the tuner control algorithm starts acting only after the injection of the first longer bunch train which causes the bunches for this injection to experience the largest power spikes. This contribution presents an adapted detuning scheme for the RF cavities before injection. It was proposed as a path to decrease the transients, hence increasing the available intensity margin for the available RF power. The expected gain is evaluated in particle tracking simulations and measurements acquired during operation.

Poster THBP29 [3.711 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-HB2023-THBP29

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Received ※ 30 September 2023 — Revised ※ 08 October 2023 — Accepted ※ 10 October 2023 — Issued ※ 22 October 2023

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THBP37

Refining the LHC Longitudinal Impedance Model

impedance, 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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THBP39

Advances on LHC RF Power Limitation Studies at Injection

injection, operation, klystron, controls

567

H. Timko, T. Argyropoulos, R. Calaga, N. Catalán Lasheras, K. Iliakis, B.E. Karlsen-Bæck, I. Karpov, M. Zampetakis
CERN, Meyrin, Switzerland

The average power consumption of the main RF system during beam injection in the High-Luminosity Large Hadron Collider is expected to be close to the maximum available klystron power. Power transients due to the mismatch of the beam and the action of control loops will exceed the available power. This paper presents the most recent estimations of the injection voltage and steady-state power needed for HL-LHC intensities, taking also beam stability into account. It summarises measurement and simulation efforts ongoing to better understand power transients and beam losses, and describes the operational margin to be taken into account for different equipment.

Poster THBP39 [0.861 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-HB2023-THBP39

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Received ※ 29 September 2023 — Revised ※ 08 October 2023 — Accepted ※ 11 October 2023 — Issued ※ 20 October 2023

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THBP40

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

impedance, 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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THBP43

Intensity Effects in a Chain of Muon RCSs

HOM, acceleration, wakefield, collider

579

F. Batsch, D. Amorim, H. Damerau, A. Grudiev, I. Karpov, E. Métral, D. Schulte
CERN, Meyrin, Switzerland
A. Chancé
CEA, Gif-sur-Yvette, France
S. Udongwo
Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany

Funding: Funded by the European Union under Grant Agreement n.101094300
The muon collider offers an attractive path to a compact, multi-TeV lepton collider. However, the short muon lifetime leads to stringent requirements on the fast energy increase. While extreme energy gains in the order of several GeV per turn are crucial for a high elevated muon survival rate, ultra-short and intense bunches are needed to achieve large luminosity. The longitudinal beam dynamics of a chain of rapid cycling synchrotrons (RCS) for acceleration from around 60 GeV to several TeV is being investigated in the framework of the International Muon Collider Collaboration. Each RCS must have a distributed radio-frequency (RF) system with several hundred RF stations to establish stable synchrotron motion. In this contribution, the beam-induced voltage in each RCS is studied, assuming a single high-intensity bunch per beam in each direction and ILC-like 1.3 GHz accelerating structures. The impact of single- and multi-turn wakefields on longitudinal stability and RF power requirements is analysed with particle tracking simulations. Special attention is moreover paid to the beam power deposited into the higher-order modes of the RF cavities.

Poster THBP43 [1.345 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-HB2023-THBP43

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

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THBP44

ImpactX Modeling of Benchmark Tests for Space Charge Validation

space-charge, focusing, emittance, proton

583

C.E. Mitchell, M. Garten, A. Huebl, R. Lehé, J. Qiang, R.T. Sandberg, J.-L. Vay
LBNL, Berkeley, California, USA

The code ImpactX represents the next generation of the particle-in-cell code IMPACT-Z, featuring s-based symplectic tracking with 3D space charge, parallelism with GPU acceleration, adaptive mesh-refinement, and modernized language features. With such a code comes a renewed need for space charge validation using well-defined benchmarks. For this purpose, the code is continuously checked against a test suite of exactly-solvable problems. The suite includes field calculation tests, dynamical tests involving coasting or stationary beams, and beams matched to periodic focusing channels. To study the long-time multi-turn performance of the code in a more complex setting, we investigate problems involving high-intensity storage rings, such as the GSI benchmark problem for space charge induced trapping. Comparisons against existing codes are made where possible.

Poster THBP44 [1.020 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-HB2023-THBP44

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Received ※ 01 October 2023 — Revised ※ 08 October 2023 — Accepted ※ 11 October 2023 — Issued ※ 26 October 2023

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THBP45

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

simulation, beam-loading, impedance, injection

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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FRA1I2

Design and Beam Commissioning of Dual Harmonic RF System in CSNS RCS

injection, bunching, MMI, space-charge

633

H.Y. Liu, L. Huang
IHEP CSNS, Guangdong Province, People’s Republic of China
Y. Liu
DNSC, Dongguan, People’s Republic of China
S. Wang, S.Y. Xu
IHEP, Beijing, People’s Republic of China

The CSNS accelerator achieved an average beam power on target of 100 kW in February 2020 and subsequently increased it to 125 kW in March 2022. Building upon this success, CSNS plans to further enhance the average beam power to 200 kW by doubling the particle number of the circulating beam in the RCS, while keeping the injection energy same. The space charge effect is a main limit for the beam intensity increase in high-power particle accelerators. By providing a second harmonic RF cavity with a harmonic number of 4, in combination with the ferrite cavity with a harmonic number of 2, the dual harmonic RF system aims to mitigate emittance increase and beam loss caused by space charge effects, thereby optimizing the longitudinal beam distribution. This paper will concentrate on the beam commissioning for the 140 kW operation subsequent to the installation of the magnetic alloy (MA) cavity. The commissioning process includes the optimization of RF parameters, beam studies, and evaluation of the beam quality and instability.

Slides FRA1I2 [4.086 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-HB2023-FRA1I2

About •

Received ※ 30 September 2023 — Revised ※ 09 October 2023 — Accepted ※ 14 October 2023 — Issued ※ 27 October 2023

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FRA1C1

New Techniques Method for Improving the Performance of the ALPI Linac

linac, controls, dipole, quadrupole

638

L. Bellan, C.O. Carletto, M. Comunian, E. Fagotti, M.G. Giacchini, F. Grespan, M. Montis, Y.K.F. Ong, A. Pisent
INFN/LNL, Legnaro (PD), Italy

The superconductive quarter wave cavities hadron Linac ALPI is the final acceleration stage at the Legnaro National Laboratories. It can accelerate heavy ions from carbon to uranium up to 10 MeV/u for nuclear and applied physics experiments. It is also planned to use it for re-acceleration of the radioactive ion beams for the SPES (Selective Production of Exotic Species) project. In this article we will present the innovative results obtained with swarm intelligence algorithms, in simulations and measurements. In particular, the increment of the longitudinal acceptance for RIB (Radioactive Ion Beams) acceleration, and beam orbit correction without the beam first order measurements will be discussed.

Slides FRA1C1 [1.540 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-HB2023-FRA1C1

About •

Received ※ 01 October 2023 — Revised ※ 06 October 2023 — Accepted ※ 10 October 2023 — Issued ※ 11 October 2023

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FRA2I3

Summary of the Working Group C on Accelerator Systems

impedance, injection, 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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