IPAC2021 - List of Keywords (feedback)

Paper	Title	Other Keywords	Page
MOPAB068	Collective Effects Studies for the SOLEIL Upgrade	impedance, synchrotron, storage-ring, cavity	274
	A. Gamelin, D. Amorim, P. Brunelle, W. Foosang, A. Loulergue, L.S. Nadolski, R. Nagaoka, R. Ollier, M.-A. Tordeux SOLEIL, Gif-sur-Yvette, France
	The SOLEIL upgrade project aims to replace the actual SOLEIL storage ring by a 4th generation light source. The project has just finished its conceptual design report (CDR) phase. Compared to the SOLEIL storage ring, the upgraded storage ring design includes many new features of 4th generation light sources that will impact collective effects, such as reduced beam pipe apertures, a smaller momentum compaction factor and the presence of harmonic cavities (HC). To mitigate them, we rely on several damping mechanisms provided by the synchrotron radiation, the transverse feedback system, and the HC (Landau damping and bunch lengthening). This article presents a first estimate of the collective effects impact of the upgraded design. Conceptual Design Report: Synchrotron SOLEIL Upgrade, 2021, in press.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB068
About •	paper received ※ 17 May 2021 paper accepted ※ 02 June 2021 issue date ※ 12 August 2021
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MOPAB079	Experience of the First Six Years Operations and Plans in NSlS-II	operation, cavity, MMI, vacuum	308
	G.M. Wang BNL, Upton, New York, USA
	NSLS-II is a 3 GeV third-generation synchrotron light source at BNL. The storage ring was commissioned in 2014 and began its routine operations in the December of the same year. Since then, we have been continuously installing and commissioning new insertion devices, their front-ends, and beamlines. At this point, the facility hosts 28 operating beamlines from various radiation sources, including damping wiggler, IVU, EPU, 3PW, and bending magnets for infrared beamlines. Over the past six years, the storage ring performance continuously improved, including 500 mA with limited insertion devices close due to RF power limitation and routinely 400 mA top off operation, >95% operation reliability, maintenance of beam motion short- and long-term stability. In this paper, we report NSLS-II accelerator operations experience and plans for future facility developments.
	Poster MOPAB079 [2.064 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB079
About •	paper received ※ 17 May 2021 paper accepted ※ 21 June 2021 issue date ※ 25 August 2021
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MOPAB087	Design of a Multi-Bunch Feedback Kicker in SPEAR3	kicker, impedance, simulation, coupling	327
	K. Tian, J.B. Langton, NL. Parry, J.A. Safranek, J.J. Sebek SLAC, Menlo Park, California, USA
	The new Multi-bunch feedback kickers have been designed to replace the current device loaned from ALS. In this paper, we first present the specification of the kickers based on the beam physics requirements. Then the mechanical design of the kicker is elaborated. Numerical simulations, both in time domain and in frequency domain, are conducted for evaluating the shunt impedance and beam coupling impedance of the kicker. Surface heating induced from the beam or the external source is estimated from the numerical results as well.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB087
About •	paper received ※ 19 May 2021 paper accepted ※ 11 June 2021 issue date ※ 01 September 2021
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MOPAB088	Beam-Based Measurement on the Performance of Ferrite Dampers in an In-Vacuum Undulator	damping, HOM, radiation, vacuum	331
	K. Tian, A. Ringwall, J.J. Sebek SLAC, Menlo Park, California, USA
	In this paper, we first present the tracking studies for SPEAR3 with the new BL17 ID and estimate its impact on the dynamic aperture of the low emittance lattice. Then the ferrite dampers installations in the device is briefly reviewed. After that, we will show that, based on beam-based measurements, the performance of the dampers is as being expected from earlier numerical studies.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB088
About •	paper received ※ 19 May 2021 paper accepted ※ 18 June 2021 issue date ※ 24 August 2021
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MOPAB275	Study on Supports of BPM Displacement Measurement System for HLS	simulation, acceleration, factory, storage-ring	870
	C.H. Wang, P. Lu, B.G. Sun, T.Y. Zhou USTC/NSRL, Hefei, Anhui, People’s Republic of China
	Funding: National Synchrotron Radiation Laboratory HLS is the second-generation light source with energy of 800 MeV and emittance of less than 40 nm-rad. In order to improve the beam orbit stability and correct the errors introduced in the orbital feedback system due to movement of the vacuum chamber and BPM, a system for measuring BPM displacement will be built. It requires a high degree of mechanical and thermal stability for its supports. The support should have a higher eigen-frequency to minimize the amplification of ground vibration. In this paper, a series of simulation, including finite element analysis (FEA), measurement and analysis have been done upon the support to make sure it can meet the requirements of the stability of the BPM displacement measurement system.
	Poster MOPAB275 [1.025 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB275
About •	paper received ※ 18 May 2021 paper accepted ※ 21 May 2021 issue date ※ 26 August 2021
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MOPAB362	Atomistic Modeling of the Coupling Between Electric Fields and Bulk Plastic Deformation in Rf Structures	simulation, experiment, coupling, framework	1125
	S. Bagchi, D. Perez LANL, Los Alamos, New Mexico, USA
	Funding: LANL-LDRD A notable bottleneck in achieving high-gradient RF technology is dictated by the onset of RF breakdown. While bulk mechanical properties are known to significantly affect breakdown propensity, the underlying mechanisms coupling RF fields to bulk plastic deformation in experimentally relevant thermo-electrical loading conditions remain to be identified at the atomic scale. Here, we present results of large-scale molecular dynamics simulations (MD) to investigate possible modes of coupling. We consider the activation of Frank-Read (FR) sources, which leads to dislocation multiplication, under the action of bi-axial thermal stresses and surface electric-field. With a charge-equilibration formalism incorporated in a classical MD model, we show that a surface electric field acting on an either preexisting or dislocation-induced surface step, can generate a long-range resolved shear stress field inside the bulk of the sample. We investigate the feedback between step growth following dislocation emission and subsequent activations of FR sources and discuss the regimes of critical length-scales and densities of dislocations, where such a mechanism could promote RF breakdown precursors.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB362
About •	paper received ※ 19 May 2021 paper accepted ※ 10 June 2021 issue date ※ 19 August 2021
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TUXA06	Loss of Transverse Landau Damping by Diffusion in High-Energy Hadron Colliders	wakefield, damping, hadron, collider	1286
	S.V. Furuseth, X. Buffat CERN, Geneva, Switzerland S.V. Furuseth EPFL, Lausanne, Switzerland
	Circular hadron colliders rely on Landau damping to stabilize the beams. Landau damping depends strongly on the bunch distribution, which is often assumed to be Gaussian in the transverse planes. In this paper, we introduce and explain an instability mechanism observed in the LHC, where Landau damping is eventually lost due to a diffusion that modifies the transverse bunch distribution. The mechanism is caused by a wide-spectrum noise that excites the transverse motion of the beam, which consequently produces wakefields that drive a narrow-spectrum diffusion. It is shown that this diffusion efficiently lowers the stability diagram at the frequency of the least stable coherent mode, leading to a loss of Landau damping after a latency. A semi-analytical model agrees with measurements in dedicated latency experiments performed in the LHC. This instability mechanism explains the need for a stability margin in octupole current in the LHC, relative to the amount needed to stabilize a Gaussian beam. We detail the impact of this mechanism and possible mitigations for the LHC and HL-LHC.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUXA06
About •	paper received ※ 19 May 2021 paper accepted ※ 25 June 2021 issue date ※ 10 August 2021
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TUPAB001	DAΦNE Commissioning for SIDDHARTA-2 Experiment	luminosity, optics, collider, positron	1322
	C. Milardi, D. Alesini, O.R. Blanco-García, M. Boscolo, B. Buonomo, S. Cantarella, A. D’Uffizi, A. De Santis, C. Di Giulio, G. Di Pirro, A. Drago, L.G. Foggetta, G. Franzini, A. Gallo, S. Incremona, A. Michelotti, L. Pellegrino, L. Piersanti, R. Ricci, U. Rotundo, L. Sabbatini, A. Stecchi, A. Stella, A. Vannozzi, M. Zobov INFN/LNF, Frascati, Italy J. Chavanne, G. Le Bec, P. Raimondi ESRF, Grenoble, France
	DAΦNE, the Frascati lepton collider, has completed the preparatory phase in order to deliver luminosity to the SIDDHARTA-2 detector. DAΦNE colliding rings rely on a new interaction region, which implements the well-established Crab-Waist collision scheme, and includes a low-beta section equipped with newly designed permanent magnet quadrupoles, and vacuum components. Diagnostics tools have been improved, especially the ones used to keep under control the beam-beam interaction. The horizontal feedback in the positron ring has been potentiated in order to achieve a higher positron current. Luminosity diagnostics have been also updated so to be compatible with the new detector design. The commissioning was initially focused on recovering the optimal dynamical vacuum conditions, outlining alignment errors, and optimizing ring optics. For this reason, a detuned optics, featured by relaxed low-b condition at the interaction point and Crab-Waist Sestupoles off, has been applied. In a second stage a low-b optics has been implemented to test collisions with a preliminary setup of the experiment detector. Machine preparation and the first luminosity results are presented and discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB001
About •	paper received ※ 19 May 2021 paper accepted ※ 09 June 2021 issue date ※ 10 August 2021
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TUPAB019	A High-Resolution, Low-Latency, Bunch-by-Bunch Feedback System for Nano-Beam Stabilization	cavity, dipole, kicker, collider	1378
	R.L. Ramjiawan, D.R. Bett, N. Blaskovic Kraljevic, T. Bromwich, P. Burrows, G.B. Christian, C. Perry JAI, Oxford, United Kingdom D.R. Bett CERN, Geneva, Switzerland N. Blaskovic Kraljevic ESS, Lund, Sweden G.B. Christian DLS, Oxfordshire, United Kingdom
	A low-latency, bunch-by-bunch feedback system employing high-resolution cavity Beam Position Monitors (BPMs) has been developed and tested at the Accelerator Test Facility (ATF2) at the High Energy Accelerator Research Organization (KEK), Japan. The feedback system was designed to demonstrate nanometer-level vertical stabilization at the focal point of the ATF2 and can be operated using either a single BPM to provide local beam stabilization, or by using two BPMs to stabilize the beam at an intermediate location. The feedback correction is implemented using a stripline kicker and the feedback calculations are performed on a digital board constructed around a Field Programmable Gate Array (FPGA). The feedback performance was tested with trains of two bunches, separated by 280ns, at a charge of ~1nC, where the vertical offset of the first bunch was measured and used to calculate the correction to be applied to the second bunch. The BPMs have been demonstrated to achieve an operational resolution of ~20nm. With the application of single-BPM and two-BPM feedback, beam stabilization of below 50nm and 41nm respectively has been achieved with a latency of 232ns.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB019
About •	paper received ※ 18 May 2021 paper accepted ※ 09 June 2021 issue date ※ 14 August 2021
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TUPAB020	A Sub-Micron Resolution, Bunch-by-Bunch Beam Trajectory Feedback System and Its Application to Reducing Wakefield Effects in Single-Pass Beamlines	wakefield, electron, cavity, kicker	1382
	D.R. Bett, P. Burrows, C. Perry, R.L. Ramjiawan JAI, Oxford, United Kingdom D.R. Bett CERN, Geneva, Switzerland K. Kubo, T. Okugi, N. Terunuma KEK, Ibaraki, Japan
	A high-precision intra-bunch-train beam orbit feedback correction system has been developed and tested at the KEK Accelerator Test Facility, ATF2. The system uses the vertical position of the bunch measured at two beam position monitors to calculate a pair of kicks which are applied to the next bunch using two upstream kickers, thereby correcting both the vertical position and trajectory angle. Using trains of two electron bunches separated in time by 187.6ns, the system was optimised so as to stabilize the beam offset at the feedback BPMs to better than 350nm, yielding a local trajectory angle correction to within 250nrad. The quality of the correction was verified using three downstream witness BPMs and the results were found to be in agreement with the predictions of a linear lattice model used to propagate the beam trajectory from the feedback region. This same model predicts a corrected be am jitter of c.1nm at the focal point of the accelerator. Measurements with a beam size monitor at this location demonstrate that reducing the trajectory jitter of the beam by a factor of 4 also reduces the increase in the measured beam size as a function of beam charge by a factor of ~1.6.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB020
About •	paper received ※ 13 May 2021 paper accepted ※ 01 July 2021 issue date ※ 11 August 2021
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TUPAB083	Dual Energies in the LCLS Copper Linac	linac, quadrupole, klystron, betatron	1570
	F.-J. Decker, C. Bianchini Mattison, D.K. Bohler, A. Brachmann, W.S. Colocho, S. Condamoor, M.L. Gibbs, K.H. Kim, A.A. Lutman, T.J. Maxwell, J.A. Mock, H.-D. Nuhn, J.C. Sheppard, H. Smith, T.J. Smith, M. Stanek, S. Zelazny, Z. Zhang, C.M. Zimmer SLAC, Menlo Park, California, USA
	For LCLS-II two undulators were installed at SLAC, one for soft and one for hard x-rays. Before the superconducting linac gets turned on the copper linac is providing beams at 120 Hz to these two beam destinations. The 120 Hz can be split in many different ratios between soft and hard via a pulsed magnet. To get an optimized beam for the quite different photon energies the pulsed linac components like modulators and RF can provide many different beam parameters, mainly energies and bunch lengths for the two undulator lines. How this was implemented with timing setups of triggers and finally after the split the necessary matching of the transverse phase space will be discussed.
	Poster TUPAB083 [0.479 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB083
About •	paper received ※ 19 May 2021 paper accepted ※ 27 May 2021 issue date ※ 21 August 2021
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TUPAB254	Limiting Coherent Longitudinal Beam Oscillations in the EIC Electron Storage Ring	electron, cavity, emittance, hadron	2046
	B. Podobedov Brookhaven National Laboratory (BNL), Electron-Ion Collider, Upton, New York, USA M. Blaskiewicz BNL, Upton, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy. We study coherent longitudinal beam oscillations in the EIC electron storage ring (ESR). We show that to avoid unacceptable hadron emittance growth due to finite crossing angle, the amplitude of these oscillations needs to be limited to a fraction of a millimeter. Using an analytical model we estimate the amplitude of these oscillations under the two scenarios: 1) the beam is passively stable and the oscillations are driven by RF phase noise only; 2) a coupled-bunch instability, presently expected in the ESR, is damped by a longitudinal feedback system. We show that, for the 2nd scenario, comfortable specifications for RF phase noise and feedback sensor noise will be sufficient to maintain the oscillation amplitude within the required limits.
	Poster TUPAB254 [1.347 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB254
About •	paper received ※ 12 May 2021 paper accepted ※ 18 June 2021 issue date ※ 26 August 2021
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TUPAB263	The Phase Loop Status of the RF System in CSNS/RCS	proton, cavity, space-charge, MMI	2076
	L. Huang, X. Li, S. Wang IHEP, Beijing, People’s Republic of China M.T. Li, H.Y. Liu IHEP CSNS, Guangdong Province, People’s Republic of China Y. Liu DNSC, Dongguan, People’s Republic of China
	The Rapid Cycling Synchrotron (RCS) of the China Spallation Neutron Source (CSNS) is a high intensity proton accelerator. The acceleration system consists of eight ferrite loaded cavities. The RCS is the space charge dominant machine and it is mitigated through the bunch factor optimization in the beam commissioning, so the injected beam will occupy a larger bucket size and unavoidable mismatch with the bucket, thus the dipole oscillation is excited. The phase loop scheme is designed to restrict the oscillation in the RF system, but the transmission efficiency is reduced by the phase loop and the bunch factor also increases, so the phase loop scheme is studied. To keep the phase loop but also maintain the transmission efficiency, we optimized the original phase loop scheme, but the beam loss still increases small when the loop on.
	Poster TUPAB263 [1.548 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB263
About •	paper received ※ 13 May 2021 paper accepted ※ 02 June 2021 issue date ※ 21 August 2021
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TUPAB302	Arrival Time Stabilization at Flash Using the Bunch Arrival Corrector Cavity (BACCA)	cavity, electron, laser, SRF	2194
	B. Lautenschlager, L. Butkowski, M.K. Czwalinna, B. Dursun, M. Hierholzer, S. Pfeiffer, H. Schlarb, Ch. Schmidt DESY, Hamburg, Germany
	For pump-probe and seeding experiments at free electron lasers, a femtosecond precise bunch arrival time stability is mandatory. To stabilize the arrival times a fast longitudinal intra bunch-train feedback (L-IBFB) using bunch arrival time monitors is applied. The electron bunch energy prior to a bunch compression chicane is modulated by superconducting radio frequency (SRF) cavities to compensate fast arrival time fluctuations of the subsequent bunches. A broadband normal conducting RF cavity was installed in front of the first bunch compression chicane at FLASH. The L-IBFB uses the normal conducting cavity for small but fast energy corrections together with the SRF cavities for larger and slower corrections. Current measurements show arrival time stabilities of the electron bunches towards 5 fs (rms) at the end of the linac, if the normal conducting cavity acts together with the SRF cavities in the L-IBFB system.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB302
About •	paper received ※ 19 May 2021 paper accepted ※ 23 June 2021 issue date ※ 26 August 2021
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TUPAB306	Status of Beam-Based Feedback Research and Development for Continuous Wave SRF Linac ELBE	controls, electron, cavity, LLRF	2200
	A. Maalberg, M. Kuntzsch HZDR, Dresden, Germany E. Petlenkov TalTech, Tallinn, Estonia
	The superconducting electron linear accelerator ELBE at Helmholtz-Zentrum Dresden-Rossendorf is a versatile light source operated in continuous wave mode. As the demand on the beam stability increases, the improvement of the beam control schemes currently installed at ELBE becomes highly relevant. This improvement can be achieved by an upgrade of the existing digital MicroTCA.4-based LLRF control scheme by beam-based feedback. By presenting both the design and implementation details of the new control scheme this contribution reports the status of the work in progress.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB306
About •	paper received ※ 19 May 2021 paper accepted ※ 21 June 2021 issue date ※ 30 August 2021
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WEPAB117	Injection Feedback for a Storage Ring	injection, HOM, kicker, simulation	2870
	A. Moutardier, C. Bruni, I. Chaikovska, S. Chancé, N. Delerue, E.E. Ergenlik, V. Kubytskyi, H. Monard Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
	Funding: Research Agency under the Equipex convention ANR-10-EQPX-0051. We report on an injection feedback scheme for the ThomX storage ring project. ThomX is a 50-MeV-electron accelerator prototype which will use Compton backscattering in a storage ring to generate a high flux of hard X-rays. Given the slow beam damping (in the ring), the injection must be performed with high accuracy to avoid large betatron oscillations. A homemade analytic code is used to compute the corrections that need to be applied before the beam injection to achieve a beam position accuracy of a few hundred micrometers in the first beam position monitors (BPMs). In order to do so the code needs the information provided by the ring’s diagnostic devices. The iterative feedback system has been tested using MadX simulations. Our simulations show that a performance that matches the BPMs’ accuracy can be achieved in less than 50 iterations in all cases. Details of this feedback algorithm, its efficiency and the simulations are discussed.
	Poster WEPAB117 [2.422 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB117
About •	paper received ※ 28 May 2021 paper accepted ※ 01 July 2021 issue date ※ 25 August 2021
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WEPAB123	Multi-Bunch Resistive Wall Wake Field Tracking via Pseudomodes in the ALS-U Accumulator Ring	injection, damping, simulation, kicker	2893
	M.P. Ehrlichman, S. De Santis, T. Hellert, S.C. Leemann, G. Penn, C. Steier, C. Sun, M. Venturini, D. Wang LBNL, Berkeley, USA
	For the ALS-U project, particles will be injected from the booster to the accumulator ring utilizing an injection scheme that leaves the stored and injected particles with a non-trivial transient. This transient requires that multibunch feedback be masked for those buckets into which charge is injected. The masking significantly diminishes the damping capability of the multibunch feedback system. This problem is exacerbated by the large injection transient. The higher order resistive wall wake fields in the accumulator ring exceed the radiation damping time. To study whether the beam will remain multibunch stable during an injection cycle, a multibunch tracking simulation is used that simulates the multibunch feedback system and also pseudomode representation of resistive wall wake fields.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB123
About •	paper received ※ 20 May 2021 paper accepted ※ 01 September 2021 issue date ※ 23 August 2021
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WEPAB134	Experimental Studies of the In-Vacuum-Cryogenic Undulator Effect on Beam Instabilities at BESSY II	undulator, vacuum, damping, impedance	2929
	M. Huck, J. Bahrdt, A. Meseck, G. Rehm, M. Ries, A. Schälicke HZB, Berlin, Germany
	A new in-vacuum cryogenic permanent magnet undulator (CPMU17) has been installed in summer 2018 in the BESSY II storage ring at HZB. Such a small gap in-vacuum undulator device increases the impedance of the storage ring and can contribute to the instabilities that adversely affect the beam quality and the device itself. To identify and explore the effects of CPMU17 on the instabilities at BESSY II, grow-damp and drive-damp experiments have been conducted using the installed bunch-by-bunch feedback system. In this paper, the first results of the mode and gap analysis of these studies with a brief overview of other impedance studies will be presented.
	Poster WEPAB134 [1.079 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB134
About •	paper received ※ 17 May 2021 paper accepted ※ 02 July 2021 issue date ※ 23 August 2021
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WEPAB239	Effect of Chromaticity and Feedback on Transverse Head-Tail Instability	impedance, coupling, damping, storage-ring	3189
	V.V. Smaluk, G. Bassi, A. Blednykh, A. Khan BNL, Upton, New York, USA
	Funding: This work was supported by the US Department of Energy under contract DE-SC0012704. The head-tail instability caused by the beam interaction with short-range wakefields is a major limitation for the single-bunch beam intensity in circular accelerators. The combined effect of the transverse feedback systems and chromaticity suppressing the instability is discussed. Theoretical and experimental studies of the head-tail instability and methods of its mitigation are reviewed. Results of experimental studies of the transverse mode coupling carried out at NSLS-II are compared with the theoretical model and numerical simulations.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB239
About •	paper received ※ 19 May 2021 paper accepted ※ 24 June 2021 issue date ※ 12 August 2021
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WEPAB290	Pointing Stabilization Algorithms Explored and Implemented with the Low Energy RHIC Electron Cooling Laser	laser, operation, electron, cathode	3336
	L.K. Nguyen BNL, Upton, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy. The electron beam for the Low Energy RHIC electron Cooler (LEReC) at Brookhaven National Laboratory (BNL) is generated by a high-power fiber laser illuminating a photocathode, with a total propagation distance of 34 m separating the laser output and the photocathode. This propagation is facilitated by three independent laser tables that have varying responses to changes in time of day, weather, and season. Alignment drifts induced by these environmental changes are mitigated by an active "slow" pointing stabilization system found along the length of the transport, and this in-house system was commissioned as part of the full laser transport in 2019, as previously reported. In 2020, the system became fully operational alongside LEReC, the world’s first electron cooler in a collider, and helped establish the transverse stability of the electron beam required for cooling. A summary of the different slow stabilization algorithms, which were continually refined during the run in order to achieve long-term center-of-mass stability of the laser spot on the photocathode to within 10 microns RMS, is provided. L. K. Nguyen et al., "Active Pointing Stabilization Techniques Applied to the Low Energy RHIC Electron Cooling Laser Transport at BNL", presented at NAPAC’19, paper THYBA6.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB290
About •	paper received ※ 19 May 2021 paper accepted ※ 02 July 2021 issue date ※ 24 August 2021
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WEPAB330	A Multirange Low Noise Transimpedance Amplifier for Sirius Beamlines	impedance, operation, FEM, synchrotron	3447
	L.Y. Tanio, F.H. Cardoso, M.M. Donatti LNLS, Campinas, Brazil
	In a typical synchrotron beamline, the interaction of photon beams with different materials generates free electric charges in devices such as ionization chambers, photodiodes, or even isolated metallic structures (e.g., blades, blocks, foils, wires). These free charges can be measured as electric current to diagnose the photon beam intensity, profile, position, or stability. Sirius, the new 3GeV fourth-generation Brazilian light source, may accommodate up to 38 beamlines, which combined will make use of hundreds of instruments to measure such low-intensity signals. This work reports on the design and test results of a transimpedance amplifier developed for low current measurements at Sirius’ beamlines. The device presents low noise, high accuracy, and good temperature stability providing 5 selectable ranges (from 500pA to 7.3mA) to measure bipolar currents achieving femtoampere resolution under certain conditions. Considering low bandwidth applications, the results suggest noise performance comparable to commercial bench instruments. Additionally, the project definitions and plans for the development of a family of low current ammeters will be discussed.
	Poster WEPAB330 [2.642 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB330
About •	paper received ※ 19 May 2021 paper accepted ※ 16 June 2021 issue date ※ 21 August 2021
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THXB02	Beam Arrival Stability at the European XFEL	FEL, laser, timing, electron	3714
	M.K. Czwalinna, J. Kral, B. Lautenschlager, J. Müller, H. Schlarb, S. Schulz, B. Steffen DESY, Hamburg, Germany R. Boll, H. Kirkwood, J. Koliyadu, R. Letrun, J. Liu, F. Pallas, D.E. Rivas, T. Sato EuXFEL, Schenefeld, Germany
	Free electron laser facilities, such as the European XFEL, make increasingly high demands on the longterm temporal stability and uniformity of the electron bunches, as pump-probe experiments meanwhile aim for timing stabilities of few femtoseconds residual jitter only. For a beam-based feedback control of the linear accelerator, electro-optical bunch arrival-time monitors are deployed, achieving a time resolution better than 3 fs. In a first attempt, we recently demonstrated a beam-based feedback system, reducing the arrival time jitter of the electron bunches to the 10 fs level with stable operation over hours. For pump-probe experiments it is crucial to equally verify this new level of precision in the FEL pulse arrival time with independent methods. In this work, we are discussing first results from examining the facility-wide temporal stability at the European XFEL, with attention to the contributions of various sub-systems and on the different time scales.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THXB02
About •	paper received ※ 19 May 2021 paper accepted ※ 20 July 2021 issue date ※ 23 August 2021
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THPAB063	Laser Transport System of Shanghai Laser Electron Gamma Source (SLEGS)	laser, detector, controls, scattering	3897
	H.H. Xu, G.T. Fan SSRF, Shanghai, People’s Republic of China
	Shanghai Laser Electron Gamma Source (SLEGS) , based on laser Compton scattering (LCS), as one of beamlines of Shanghai Synchrotron Radiation Facility (SSRF) in phase II, is under construction now. The technical design of its laser injection system has been implemented and optimized consecutively over the last few years. In order to inject the 10640 nm CO₂ laser into the interaction point from the laser hutch outside the storage ring’s shielding, a laser transport system longer than 20 m using relay-imaging telescopes is designed. There are two operation mode in SLEGS. One is backscattering mode, which will make the laser and electron bunch collide at 180° with flux higher than 10⁷ gamma/s. The other mode is slanting mode, which mainly inherits the design used in the prototype. In this paper, a brief summary of the laser transport system is given. The system contains several modules to perform beam expansion, combining, monitoring and real-time adjustment. The design models, simulation study of the laser quality through the transporta-tion, and the experimental results are presented. Y. Xu, W. Xu, et al., NIM A, 578, 457 (2007). ** H.H. Xu, J.H. Chen, et al., Transaction on Nuclear Science, IEEE, 63, 906 (2016).
	Poster THPAB063 [2.508 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB063
About •	paper received ※ 19 May 2021 paper accepted ※ 24 June 2021 issue date ※ 27 August 2021
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THPAB257	Fast Orbit Corrector Power Supply in MTCA.4 Form Factor for Sirius Light Source	controls, power-supply, hardware, target	4307
	A.F. Giachero, G.B.M. Bruno, L.M. Russo, D.O. Tavares LNLS, Campinas, Brazil
	A new fast orbit feedback (FOFB) hardware architecture has been pursued at Sirius. The fast corrector magnets’ are fed by power supply modules which are placed in the same MicroTCA.4 crates where the BPM digitizers and FOFB controllers are located. Each channel is made of a 3-Watt linear amplifier whose output currents are digitally controlled by the same FPGA where the distributed orbit feedback controller is processed. The amplifier is specified to reach up to 10 kHz small-signal bandwidth on a 3.5 mH inductance magnet and ±1 A full scale, which translates to 30 urad deflection on Sirius’ 3 GeV beam. Such a high level of integration aims at minimizing the overall latency of the FOFB loop while leveraging the crate infrastructure, namely electronics enclosure, DC power, cooling, and hardware management support already provided by the MTCA.4 crates. The fast corrector power supply channels are placed on Rear Transition Modules (RTMs) which are attached to the front AMC FPGA module where the FOFB controller is implemented. This paper will describe the main design concepts and report on the experimental results of the first prototypes.
	Poster THPAB257 [48.881 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB257
About •	paper received ※ 22 May 2021 paper accepted ※ 27 July 2021 issue date ※ 20 August 2021
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THPAB258	Status of Time-Domain Simulation for the Fast Orbit Feedback System at the HEPS	simulation, vacuum, power-supply, emittance	4311
	Y. Wei, Z. Duan, X.Y. Huang, Y. Jiao IHEP, Beijing, People’s Republic of China
	High Energy Photon Source (HEPS) is a complex designed at ultra-low emittance. A fast orbit feedback system is proposed to meet the requirement of beam orbit stability at the sub-micron level. In this paper, we present our work on setting up an orbit feedback process combined with noise model, system modeling, and particle tracking in the time domain. RF phase parameter is adjusted together with fast correctors to mitigate the orbit fluctuation due to energy vibration. The preliminary results are shown here. By the following optimization, we hope to provide an effective tool to specify and configure the FOFB system with the simulation.
	Poster THPAB258 [1.334 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB258
About •	paper received ※ 19 May 2021 paper accepted ※ 27 July 2021 issue date ※ 31 August 2021
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THPAB309	New Working Tune Feedback System for TLS	quadrupole, insertion, insertion-device, radiation	4394
	S.J. Huang, Y.K. Lin, Y.C. Lin NSRRC, Hsinchu, Taiwan
	TLS storage ring has two sets of working tuning feedback systems: one is used to correct the working tune deviation caused by insertion device U90; another system uses a local trim coil to correct the working tune deviation caused by all insertion devices. This article describes a new working tune feedback system in TLS that can correct the working tune effectively back to the required conditions for operation; the two existing feedback systems do not cause problems. We can both avoid increasing the local radiation dose and decreasing the injection efficiency.
	Poster THPAB309 [0.831 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB309
About •	paper received ※ 15 May 2021 paper accepted ※ 02 July 2021 issue date ※ 23 August 2021
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THPAB311	Using Linear Regression to Model the Parameters of the Flat Wires in TLS-EPU56	injection, undulator, hardware, electron	4399
	S.J. Huang, Y.H. Chang, T.Y. Chung NSRRC, Hsinchu, Taiwan Y.W. Chen Academia Sinica, Taipei, Taiwan
	Although a theoretical calculation might predict the set currents of the flat wires, which are used to compensate the deviation in the Betatron tune caused by the elliptically polarized undulator (EPU), those set currents must still be tuned in reality. To approach this reality, a strategy of Machine Learning was adopted, which included collecting real-condition data and using a linear-regression model to adjust the parameters of the flat wires. After training the model, the predictions in variables tune x, tune y and beam size x were compared with the required amount of correction of the EPU at various gaps and phases. To prove the feasibility of this method, a test was performed under the real conditions of accelerator Taiwan Light Source (TLS).
	Poster THPAB311 [1.226 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB311
About •	paper received ※ 13 May 2021 paper accepted ※ 28 June 2021 issue date ※ 30 August 2021
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THPAB337	Resonance Control System for the PIP-II IT HWR Cryomodule	cavity, controls, cryomodule, resonance	4446
	P. Varghese, B.E. Chase, P.M. Hanlet, H. Maniar, D.J. Nicklaus, S. Sankar Raman Fermilab, Batavia, Illinois, USA L.R. Doolittle, S. Paiagua, C. Serrano LBNL, Berkeley, California, USA
	The HWR (half-wave-resonator) cryomodule is the first one in the superconducting section of the PIP-II LINAC project at Fermilab. PIP-II IT is a test facility for the project where the injector, warm front-end, and the first two superconducting cryomodules are being tested. The HWR cryomodule comprises 8 cavities operating at a frequency of 162.5 MHz and accelerating beam up to 10 MeV. Resonance control of the cavities is performed with a pneumatically operated slow tuner which compresses the cavity at the beam ports. Helium gas pressure in a bellows mounted to an end wall of the cavity is controlled by two solenoid valves, one on the pressure side and one on the vacuum side. The resonant frequency of the cavity can be controlled in one of two modes. A pressure feedback control loop can hold the cavity tuner pressure at a fixed value for the desired resonant frequency. Alternately, the feedback loop can regulate the cavity tuner pressure to bring the RF detuning error to zero. The resonance controller is integrated into the LLRF control system for the cryomodule. The control system design and performance of the resonance control system are described in this paper.
	Poster THPAB337 [4.426 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB337
About •	paper received ※ 12 May 2021 paper accepted ※ 26 July 2021 issue date ※ 27 August 2021
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Paper

Title

Other Keywords

Page

MOPAB068

Collective Effects Studies for the SOLEIL Upgrade

impedance, synchrotron, storage-ring, cavity

274

A. Gamelin, D. Amorim, P. Brunelle, W. Foosang, A. Loulergue, L.S. Nadolski, R. Nagaoka, R. Ollier, M.-A. Tordeux
SOLEIL, Gif-sur-Yvette, France

The SOLEIL upgrade project aims to replace the actual SOLEIL storage ring by a 4th generation light source. The project has just finished its conceptual design report (CDR) phase*. Compared to the SOLEIL storage ring, the upgraded storage ring design includes many new features of 4th generation light sources that will impact collective effects, such as reduced beam pipe apertures, a smaller momentum compaction factor and the presence of harmonic cavities (HC). To mitigate them, we rely on several damping mechanisms provided by the synchrotron radiation, the transverse feedback system, and the HC (Landau damping and bunch lengthening). This article presents a first estimate of the collective effects impact of the upgraded design.
* Conceptual Design Report: Synchrotron SOLEIL Upgrade, 2021, in press.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB068

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paper received ※ 17 May 2021 paper accepted ※ 02 June 2021 issue date ※ 12 August 2021

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MOPAB079

Experience of the First Six Years Operations and Plans in NSlS-II

operation, cavity, MMI, vacuum

308

G.M. Wang
BNL, Upton, New York, USA

NSLS-II is a 3 GeV third-generation synchrotron light source at BNL. The storage ring was commissioned in 2014 and began its routine operations in the December of the same year. Since then, we have been continuously installing and commissioning new insertion devices, their front-ends, and beamlines. At this point, the facility hosts 28 operating beamlines from various radiation sources, including damping wiggler, IVU, EPU, 3PW, and bending magnets for infrared beamlines. Over the past six years, the storage ring performance continuously improved, including 500 mA with limited insertion devices close due to RF power limitation and routinely 400 mA top off operation, >95% operation reliability, maintenance of beam motion short- and long-term stability. In this paper, we report NSLS-II accelerator operations experience and plans for future facility developments.

Poster MOPAB079 [2.064 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB079

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paper received ※ 17 May 2021 paper accepted ※ 21 June 2021 issue date ※ 25 August 2021

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MOPAB087

Design of a Multi-Bunch Feedback Kicker in SPEAR3

kicker, impedance, simulation, coupling

327

K. Tian, J.B. Langton, NL. Parry, J.A. Safranek, J.J. Sebek
SLAC, Menlo Park, California, USA

The new Multi-bunch feedback kickers have been designed to replace the current device loaned from ALS. In this paper, we first present the specification of the kickers based on the beam physics requirements. Then the mechanical design of the kicker is elaborated. Numerical simulations, both in time domain and in frequency domain, are conducted for evaluating the shunt impedance and beam coupling impedance of the kicker. Surface heating induced from the beam or the external source is estimated from the numerical results as well.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB087

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paper received ※ 19 May 2021 paper accepted ※ 11 June 2021 issue date ※ 01 September 2021

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MOPAB088

Beam-Based Measurement on the Performance of Ferrite Dampers in an In-Vacuum Undulator

damping, HOM, radiation, vacuum

331

K. Tian, A. Ringwall, J.J. Sebek
SLAC, Menlo Park, California, USA

In this paper, we first present the tracking studies for SPEAR3 with the new BL17 ID and estimate its impact on the dynamic aperture of the low emittance lattice. Then the ferrite dampers installations in the device is briefly reviewed. After that, we will show that, based on beam-based measurements, the performance of the dampers is as being expected from earlier numerical studies.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB088

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paper received ※ 19 May 2021 paper accepted ※ 18 June 2021 issue date ※ 24 August 2021

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MOPAB275

Study on Supports of BPM Displacement Measurement System for HLS

simulation, acceleration, factory, storage-ring

870

C.H. Wang, P. Lu, B.G. Sun, T.Y. Zhou
USTC/NSRL, Hefei, Anhui, People’s Republic of China

Funding: National Synchrotron Radiation Laboratory
HLS is the second-generation light source with energy of 800 MeV and emittance of less than 40 nm-rad. In order to improve the beam orbit stability and correct the errors introduced in the orbital feedback system due to movement of the vacuum chamber and BPM, a system for measuring BPM displacement will be built. It requires a high degree of mechanical and thermal stability for its supports. The support should have a higher eigen-frequency to minimize the amplification of ground vibration. In this paper, a series of simulation, including finite element analysis (FEA), measurement and analysis have been done upon the support to make sure it can meet the requirements of the stability of the BPM displacement measurement system.

Poster MOPAB275 [1.025 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB275

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paper received ※ 18 May 2021 paper accepted ※ 21 May 2021 issue date ※ 26 August 2021

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MOPAB362

Atomistic Modeling of the Coupling Between Electric Fields and Bulk Plastic Deformation in Rf Structures

simulation, experiment, coupling, framework

1125

S. Bagchi, D. Perez
LANL, Los Alamos, New Mexico, USA

Funding: LANL-LDRD
A notable bottleneck in achieving high-gradient RF technology is dictated by the onset of RF breakdown. While bulk mechanical properties are known to significantly affect breakdown propensity, the underlying mechanisms coupling RF fields to bulk plastic deformation in experimentally relevant thermo-electrical loading conditions remain to be identified at the atomic scale. Here, we present results of large-scale molecular dynamics simulations (MD) to investigate possible modes of coupling. We consider the activation of Frank-Read (FR) sources, which leads to dislocation multiplication, under the action of bi-axial thermal stresses and surface electric-field. With a charge-equilibration formalism incorporated in a classical MD model, we show that a surface electric field acting on an either preexisting or dislocation-induced surface step, can generate a long-range resolved shear stress field inside the bulk of the sample. We investigate the feedback between step growth following dislocation emission and subsequent activations of FR sources and discuss the regimes of critical length-scales and densities of dislocations, where such a mechanism could promote RF breakdown precursors.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB362

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paper received ※ 19 May 2021 paper accepted ※ 10 June 2021 issue date ※ 19 August 2021

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TUXA06

Loss of Transverse Landau Damping by Diffusion in High-Energy Hadron Colliders

wakefield, damping, hadron, collider

1286

S.V. Furuseth, X. Buffat
CERN, Geneva, Switzerland
S.V. Furuseth
EPFL, Lausanne, Switzerland

Circular hadron colliders rely on Landau damping to stabilize the beams. Landau damping depends strongly on the bunch distribution, which is often assumed to be Gaussian in the transverse planes. In this paper, we introduce and explain an instability mechanism observed in the LHC, where Landau damping is eventually lost due to a diffusion that modifies the transverse bunch distribution. The mechanism is caused by a wide-spectrum noise that excites the transverse motion of the beam, which consequently produces wakefields that drive a narrow-spectrum diffusion. It is shown that this diffusion efficiently lowers the stability diagram at the frequency of the least stable coherent mode, leading to a loss of Landau damping after a latency. A semi-analytical model agrees with measurements in dedicated latency experiments performed in the LHC. This instability mechanism explains the need for a stability margin in octupole current in the LHC, relative to the amount needed to stabilize a Gaussian beam. We detail the impact of this mechanism and possible mitigations for the LHC and HL-LHC.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUXA06

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paper received ※ 19 May 2021 paper accepted ※ 25 June 2021 issue date ※ 10 August 2021

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TUPAB001

DAΦNE Commissioning for SIDDHARTA-2 Experiment

luminosity, optics, collider, positron

1322

C. Milardi, D. Alesini, O.R. Blanco-García, M. Boscolo, B. Buonomo, S. Cantarella, A. D’Uffizi, A. De Santis, C. Di Giulio, G. Di Pirro, A. Drago, L.G. Foggetta, G. Franzini, A. Gallo, S. Incremona, A. Michelotti, L. Pellegrino, L. Piersanti, R. Ricci, U. Rotundo, L. Sabbatini, A. Stecchi, A. Stella, A. Vannozzi, M. Zobov
INFN/LNF, Frascati, Italy
J. Chavanne, G. Le Bec, P. Raimondi
ESRF, Grenoble, France

DAΦNE, the Frascati lepton collider, has completed the preparatory phase in order to deliver luminosity to the SIDDHARTA-2 detector. DAΦNE colliding rings rely on a new interaction region, which implements the well-established Crab-Waist collision scheme, and includes a low-beta section equipped with newly designed permanent magnet quadrupoles, and vacuum components. Diagnostics tools have been improved, especially the ones used to keep under control the beam-beam interaction. The horizontal feedback in the positron ring has been potentiated in order to achieve a higher positron current. Luminosity diagnostics have been also updated so to be compatible with the new detector design. The commissioning was initially focused on recovering the optimal dynamical vacuum conditions, outlining alignment errors, and optimizing ring optics. For this reason, a detuned optics, featured by relaxed low-b condition at the interaction point and Crab-Waist Sestupoles off, has been applied. In a second stage a low-b optics has been implemented to test collisions with a preliminary setup of the experiment detector. Machine preparation and the first luminosity results are presented and discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB001

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paper received ※ 19 May 2021 paper accepted ※ 09 June 2021 issue date ※ 10 August 2021

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TUPAB019

A High-Resolution, Low-Latency, Bunch-by-Bunch Feedback System for Nano-Beam Stabilization

cavity, dipole, kicker, collider

1378

R.L. Ramjiawan, D.R. Bett, N. Blaskovic Kraljevic, T. Bromwich, P. Burrows, G.B. Christian, C. Perry
JAI, Oxford, United Kingdom
D.R. Bett
CERN, Geneva, Switzerland
N. Blaskovic Kraljevic
ESS, Lund, Sweden
G.B. Christian
DLS, Oxfordshire, United Kingdom

A low-latency, bunch-by-bunch feedback system employing high-resolution cavity Beam Position Monitors (BPMs) has been developed and tested at the Accelerator Test Facility (ATF2) at the High Energy Accelerator Research Organization (KEK), Japan. The feedback system was designed to demonstrate nanometer-level vertical stabilization at the focal point of the ATF2 and can be operated using either a single BPM to provide local beam stabilization, or by using two BPMs to stabilize the beam at an intermediate location. The feedback correction is implemented using a stripline kicker and the feedback calculations are performed on a digital board constructed around a Field Programmable Gate Array (FPGA). The feedback performance was tested with trains of two bunches, separated by 280ns, at a charge of ~1nC, where the vertical offset of the first bunch was measured and used to calculate the correction to be applied to the second bunch. The BPMs have been demonstrated to achieve an operational resolution of ~20nm. With the application of single-BPM and two-BPM feedback, beam stabilization of below 50nm and 41nm respectively has been achieved with a latency of 232ns.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB019

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paper received ※ 18 May 2021 paper accepted ※ 09 June 2021 issue date ※ 14 August 2021

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TUPAB020

A Sub-Micron Resolution, Bunch-by-Bunch Beam Trajectory Feedback System and Its Application to Reducing Wakefield Effects in Single-Pass Beamlines

wakefield, electron, cavity, kicker

1382

D.R. Bett, P. Burrows, C. Perry, R.L. Ramjiawan
JAI, Oxford, United Kingdom
D.R. Bett
CERN, Geneva, Switzerland
K. Kubo, T. Okugi, N. Terunuma
KEK, Ibaraki, Japan

A high-precision intra-bunch-train beam orbit feedback correction system has been developed and tested at the KEK Accelerator Test Facility, ATF2. The system uses the vertical position of the bunch measured at two beam position monitors to calculate a pair of kicks which are applied to the next bunch using two upstream kickers, thereby correcting both the vertical position and trajectory angle. Using trains of two electron bunches separated in time by 187.6ns, the system was optimised so as to stabilize the beam offset at the feedback BPMs to better than 350nm, yielding a local trajectory angle correction to within 250nrad. The quality of the correction was verified using three downstream witness BPMs and the results were found to be in agreement with the predictions of a linear lattice model used to propagate the beam trajectory from the feedback region. This same model predicts a corrected be am jitter of c.1nm at the focal point of the accelerator. Measurements with a beam size monitor at this location demonstrate that reducing the trajectory jitter of the beam by a factor of 4 also reduces the increase in the measured beam size as a function of beam charge by a factor of ~1.6.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB020

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paper received ※ 13 May 2021 paper accepted ※ 01 July 2021 issue date ※ 11 August 2021

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TUPAB083

Dual Energies in the LCLS Copper Linac

linac, quadrupole, klystron, betatron

1570

F.-J. Decker, C. Bianchini Mattison, D.K. Bohler, A. Brachmann, W.S. Colocho, S. Condamoor, M.L. Gibbs, K.H. Kim, A.A. Lutman, T.J. Maxwell, J.A. Mock, H.-D. Nuhn, J.C. Sheppard, H. Smith, T.J. Smith, M. Stanek, S. Zelazny, Z. Zhang, C.M. Zimmer
SLAC, Menlo Park, California, USA

For LCLS-II two undulators were installed at SLAC, one for soft and one for hard x-rays. Before the superconducting linac gets turned on the copper linac is providing beams at 120 Hz to these two beam destinations. The 120 Hz can be split in many different ratios between soft and hard via a pulsed magnet. To get an optimized beam for the quite different photon energies the pulsed linac components like modulators and RF can provide many different beam parameters, mainly energies and bunch lengths for the two undulator lines. How this was implemented with timing setups of triggers and finally after the split the necessary matching of the transverse phase space will be discussed.

Poster TUPAB083 [0.479 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB083

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paper received ※ 19 May 2021 paper accepted ※ 27 May 2021 issue date ※ 21 August 2021

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TUPAB254

Limiting Coherent Longitudinal Beam Oscillations in the EIC Electron Storage Ring

electron, cavity, emittance, hadron

2046

B. Podobedov
Brookhaven National Laboratory (BNL), Electron-Ion Collider, Upton, New York, USA
M. Blaskiewicz
BNL, Upton, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy.
We study coherent longitudinal beam oscillations in the EIC electron storage ring (ESR). We show that to avoid unacceptable hadron emittance growth due to finite crossing angle, the amplitude of these oscillations needs to be limited to a fraction of a millimeter. Using an analytical model we estimate the amplitude of these oscillations under the two scenarios: 1) the beam is passively stable and the oscillations are driven by RF phase noise only; 2) a coupled-bunch instability, presently expected in the ESR, is damped by a longitudinal feedback system. We show that, for the 2nd scenario, comfortable specifications for RF phase noise and feedback sensor noise will be sufficient to maintain the oscillation amplitude within the required limits.

Poster TUPAB254 [1.347 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB254

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paper received ※ 12 May 2021 paper accepted ※ 18 June 2021 issue date ※ 26 August 2021

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TUPAB263

The Phase Loop Status of the RF System in CSNS/RCS

proton, cavity, space-charge, MMI

2076

L. Huang, X. Li, S. Wang
IHEP, Beijing, People’s Republic of China
M.T. Li, H.Y. Liu
IHEP CSNS, Guangdong Province, People’s Republic of China
Y. Liu
DNSC, Dongguan, People’s Republic of China

The Rapid Cycling Synchrotron (RCS) of the China Spallation Neutron Source (CSNS) is a high intensity proton accelerator. The acceleration system consists of eight ferrite loaded cavities. The RCS is the space charge dominant machine and it is mitigated through the bunch factor optimization in the beam commissioning, so the injected beam will occupy a larger bucket size and unavoidable mismatch with the bucket, thus the dipole oscillation is excited. The phase loop scheme is designed to restrict the oscillation in the RF system, but the transmission efficiency is reduced by the phase loop and the bunch factor also increases, so the phase loop scheme is studied. To keep the phase loop but also maintain the transmission efficiency, we optimized the original phase loop scheme, but the beam loss still increases small when the loop on.

Poster TUPAB263 [1.548 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB263

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paper received ※ 13 May 2021 paper accepted ※ 02 June 2021 issue date ※ 21 August 2021

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TUPAB302

Arrival Time Stabilization at Flash Using the Bunch Arrival Corrector Cavity (BACCA)

cavity, electron, laser, SRF

2194

B. Lautenschlager, L. Butkowski, M.K. Czwalinna, B. Dursun, M. Hierholzer, S. Pfeiffer, H. Schlarb, Ch. Schmidt
DESY, Hamburg, Germany

For pump-probe and seeding experiments at free electron lasers, a femtosecond precise bunch arrival time stability is mandatory. To stabilize the arrival times a fast longitudinal intra bunch-train feedback (L-IBFB) using bunch arrival time monitors is applied. The electron bunch energy prior to a bunch compression chicane is modulated by superconducting radio frequency (SRF) cavities to compensate fast arrival time fluctuations of the subsequent bunches. A broadband normal conducting RF cavity was installed in front of the first bunch compression chicane at FLASH. The L-IBFB uses the normal conducting cavity for small but fast energy corrections together with the SRF cavities for larger and slower corrections. Current measurements show arrival time stabilities of the electron bunches towards 5 fs (rms) at the end of the linac, if the normal conducting cavity acts together with the SRF cavities in the L-IBFB system.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB302

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paper received ※ 19 May 2021 paper accepted ※ 23 June 2021 issue date ※ 26 August 2021

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TUPAB306

Status of Beam-Based Feedback Research and Development for Continuous Wave SRF Linac ELBE

controls, electron, cavity, LLRF

2200

A. Maalberg, M. Kuntzsch
HZDR, Dresden, Germany
E. Petlenkov
TalTech, Tallinn, Estonia

The superconducting electron linear accelerator ELBE at Helmholtz-Zentrum Dresden-Rossendorf is a versatile light source operated in continuous wave mode. As the demand on the beam stability increases, the improvement of the beam control schemes currently installed at ELBE becomes highly relevant. This improvement can be achieved by an upgrade of the existing digital MicroTCA.4-based LLRF control scheme by beam-based feedback. By presenting both the design and implementation details of the new control scheme this contribution reports the status of the work in progress.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB306

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paper received ※ 19 May 2021 paper accepted ※ 21 June 2021 issue date ※ 30 August 2021

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WEPAB117

Injection Feedback for a Storage Ring

injection, HOM, kicker, simulation

2870

A. Moutardier, C. Bruni, I. Chaikovska, S. Chancé, N. Delerue, E.E. Ergenlik, V. Kubytskyi, H. Monard
Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France

Funding: Research Agency under the Equipex convention ANR-10-EQPX-0051.
We report on an injection feedback scheme for the ThomX storage ring project. ThomX is a 50-MeV-electron accelerator prototype which will use Compton backscattering in a storage ring to generate a high flux of hard X-rays. Given the slow beam damping (in the ring), the injection must be performed with high accuracy to avoid large betatron oscillations. A homemade analytic code is used to compute the corrections that need to be applied before the beam injection to achieve a beam position accuracy of a few hundred micrometers in the first beam position monitors (BPMs). In order to do so the code needs the information provided by the ring’s diagnostic devices. The iterative feedback system has been tested using MadX simulations. Our simulations show that a performance that matches the BPMs’ accuracy can be achieved in less than 50 iterations in all cases. Details of this feedback algorithm, its efficiency and the simulations are discussed.

Poster WEPAB117 [2.422 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB117

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paper received ※ 28 May 2021 paper accepted ※ 01 July 2021 issue date ※ 25 August 2021

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WEPAB123

Multi-Bunch Resistive Wall Wake Field Tracking via Pseudomodes in the ALS-U Accumulator Ring

injection, damping, simulation, kicker

2893

M.P. Ehrlichman, S. De Santis, T. Hellert, S.C. Leemann, G. Penn, C. Steier, C. Sun, M. Venturini, D. Wang
LBNL, Berkeley, USA

For the ALS-U project, particles will be injected from the booster to the accumulator ring utilizing an injection scheme that leaves the stored and injected particles with a non-trivial transient. This transient requires that multibunch feedback be masked for those buckets into which charge is injected. The masking significantly diminishes the damping capability of the multibunch feedback system. This problem is exacerbated by the large injection transient. The higher order resistive wall wake fields in the accumulator ring exceed the radiation damping time. To study whether the beam will remain multibunch stable during an injection cycle, a multibunch tracking simulation is used that simulates the multibunch feedback system and also pseudomode representation of resistive wall wake fields.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB123

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paper received ※ 20 May 2021 paper accepted ※ 01 September 2021 issue date ※ 23 August 2021

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WEPAB134

Experimental Studies of the In-Vacuum-Cryogenic Undulator Effect on Beam Instabilities at BESSY II

undulator, vacuum, damping, impedance

2929

M. Huck, J. Bahrdt, A. Meseck, G. Rehm, M. Ries, A. Schälicke
HZB, Berlin, Germany

A new in-vacuum cryogenic permanent magnet undulator (CPMU17) has been installed in summer 2018 in the BESSY II storage ring at HZB. Such a small gap in-vacuum undulator device increases the impedance of the storage ring and can contribute to the instabilities that adversely affect the beam quality and the device itself. To identify and explore the effects of CPMU17 on the instabilities at BESSY II, grow-damp and drive-damp experiments have been conducted using the installed bunch-by-bunch feedback system. In this paper, the first results of the mode and gap analysis of these studies with a brief overview of other impedance studies will be presented.

Poster WEPAB134 [1.079 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB134

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paper received ※ 17 May 2021 paper accepted ※ 02 July 2021 issue date ※ 23 August 2021

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WEPAB239

Effect of Chromaticity and Feedback on Transverse Head-Tail Instability

impedance, coupling, damping, storage-ring

3189

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

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

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

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

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WEPAB290

Pointing Stabilization Algorithms Explored and Implemented with the Low Energy RHIC Electron Cooling Laser

laser, operation, electron, cathode

3336

L.K. Nguyen
BNL, Upton, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy.
The electron beam for the Low Energy RHIC electron Cooler (LEReC) at Brookhaven National Laboratory (BNL) is generated by a high-power fiber laser illuminating a photocathode, with a total propagation distance of 34 m separating the laser output and the photocathode. This propagation is facilitated by three independent laser tables that have varying responses to changes in time of day, weather, and season. Alignment drifts induced by these environmental changes are mitigated by an active "slow" pointing stabilization system found along the length of the transport, and this in-house system was commissioned as part of the full laser transport in 2019, as previously reported*. In 2020, the system became fully operational alongside LEReC, the world’s first electron cooler in a collider, and helped establish the transverse stability of the electron beam required for cooling. A summary of the different slow stabilization algorithms, which were continually refined during the run in order to achieve long-term center-of-mass stability of the laser spot on the photocathode to within 10 microns RMS, is provided.
* L. K. Nguyen et al., "Active Pointing Stabilization Techniques Applied to the Low Energy RHIC Electron Cooling Laser Transport at BNL", presented at NAPAC’19, paper THYBA6.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB290

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paper received ※ 19 May 2021 paper accepted ※ 02 July 2021 issue date ※ 24 August 2021

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WEPAB330

A Multirange Low Noise Transimpedance Amplifier for Sirius Beamlines

impedance, operation, FEM, synchrotron

3447

L.Y. Tanio, F.H. Cardoso, M.M. Donatti
LNLS, Campinas, Brazil

In a typical synchrotron beamline, the interaction of photon beams with different materials generates free electric charges in devices such as ionization chambers, photodiodes, or even isolated metallic structures (e.g., blades, blocks, foils, wires). These free charges can be measured as electric current to diagnose the photon beam intensity, profile, position, or stability. Sirius, the new 3GeV fourth-generation Brazilian light source, may accommodate up to 38 beamlines, which combined will make use of hundreds of instruments to measure such low-intensity signals. This work reports on the design and test results of a transimpedance amplifier developed for low current measurements at Sirius’ beamlines. The device presents low noise, high accuracy, and good temperature stability providing 5 selectable ranges (from 500pA to 7.3mA) to measure bipolar currents achieving femtoampere resolution under certain conditions. Considering low bandwidth applications, the results suggest noise performance comparable to commercial bench instruments. Additionally, the project definitions and plans for the development of a family of low current ammeters will be discussed.

Poster WEPAB330 [2.642 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB330

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paper received ※ 19 May 2021 paper accepted ※ 16 June 2021 issue date ※ 21 August 2021

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THXB02

Beam Arrival Stability at the European XFEL

FEL, laser, timing, electron

3714

M.K. Czwalinna, J. Kral, B. Lautenschlager, J. Müller, H. Schlarb, S. Schulz, B. Steffen
DESY, Hamburg, Germany
R. Boll, H. Kirkwood, J. Koliyadu, R. Letrun, J. Liu, F. Pallas, D.E. Rivas, T. Sato
EuXFEL, Schenefeld, Germany

Free electron laser facilities, such as the European XFEL, make increasingly high demands on the longterm temporal stability and uniformity of the electron bunches, as pump-probe experiments meanwhile aim for timing stabilities of few femtoseconds residual jitter only. For a beam-based feedback control of the linear accelerator, electro-optical bunch arrival-time monitors are deployed, achieving a time resolution better than 3 fs. In a first attempt, we recently demonstrated a beam-based feedback system, reducing the arrival time jitter of the electron bunches to the 10 fs level with stable operation over hours. For pump-probe experiments it is crucial to equally verify this new level of precision in the FEL pulse arrival time with independent methods. In this work, we are discussing first results from examining the facility-wide temporal stability at the European XFEL, with attention to the contributions of various sub-systems and on the different time scales.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THXB02

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paper received ※ 19 May 2021 paper accepted ※ 20 July 2021 issue date ※ 23 August 2021

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THPAB063

Laser Transport System of Shanghai Laser Electron Gamma Source (SLEGS)

laser, detector, controls, scattering

3897

H.H. Xu, G.T. Fan
SSRF, Shanghai, People’s Republic of China

Shanghai Laser Electron Gamma Source (SLEGS) *, based on laser Compton scattering (LCS), as one of beamlines of Shanghai Synchrotron Radiation Facility (SSRF) in phase II, is under construction now. The technical design of its laser injection system has been implemented and optimized consecutively over the last few years. In order to inject the 10640 nm CO₂ laser into the interaction point from the laser hutch outside the storage ring’s shielding, a laser transport system longer than 20 m using relay-imaging telescopes is designed. There are two operation mode in SLEGS. One is backscattering mode, which will make the laser and electron bunch collide at 180° with flux higher than 10⁷ gamma/s. The other mode is slanting mode, which mainly inherits the design used in the prototype**. In this paper, a brief summary of the laser transport system is given. The system contains several modules to perform beam expansion, combining, monitoring and real-time adjustment. The design models, simulation study of the laser quality through the transporta-tion, and the experimental results are presented.
* Y. Xu, W. Xu, et al., NIM A, 578, 457 (2007).
** H.H. Xu, J.H. Chen, et al., Transaction on Nuclear Science, IEEE, 63, 906 (2016).

Poster THPAB063 [2.508 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB063

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paper received ※ 19 May 2021 paper accepted ※ 24 June 2021 issue date ※ 27 August 2021

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THPAB257

Fast Orbit Corrector Power Supply in MTCA.4 Form Factor for Sirius Light Source

controls, power-supply, hardware, target

4307

A.F. Giachero, G.B.M. Bruno, L.M. Russo, D.O. Tavares
LNLS, Campinas, Brazil

A new fast orbit feedback (FOFB) hardware architecture has been pursued at Sirius. The fast corrector magnets’ are fed by power supply modules which are placed in the same MicroTCA.4 crates where the BPM digitizers and FOFB controllers are located. Each channel is made of a 3-Watt linear amplifier whose output currents are digitally controlled by the same FPGA where the distributed orbit feedback controller is processed. The amplifier is specified to reach up to 10 kHz small-signal bandwidth on a 3.5 mH inductance magnet and ±1 A full scale, which translates to 30 urad deflection on Sirius’ 3 GeV beam. Such a high level of integration aims at minimizing the overall latency of the FOFB loop while leveraging the crate infrastructure, namely electronics enclosure, DC power, cooling, and hardware management support already provided by the MTCA.4 crates. The fast corrector power supply channels are placed on Rear Transition Modules (RTMs) which are attached to the front AMC FPGA module where the FOFB controller is implemented. This paper will describe the main design concepts and report on the experimental results of the first prototypes.

Poster THPAB257 [48.881 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB257

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paper received ※ 22 May 2021 paper accepted ※ 27 July 2021 issue date ※ 20 August 2021

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THPAB258

Status of Time-Domain Simulation for the Fast Orbit Feedback System at the HEPS

simulation, vacuum, power-supply, emittance

4311

Y. Wei, Z. Duan, X.Y. Huang, Y. Jiao
IHEP, Beijing, People’s Republic of China

High Energy Photon Source (HEPS) is a complex designed at ultra-low emittance. A fast orbit feedback system is proposed to meet the requirement of beam orbit stability at the sub-micron level. In this paper, we present our work on setting up an orbit feedback process combined with noise model, system modeling, and particle tracking in the time domain. RF phase parameter is adjusted together with fast correctors to mitigate the orbit fluctuation due to energy vibration. The preliminary results are shown here. By the following optimization, we hope to provide an effective tool to specify and configure the FOFB system with the simulation.

Poster THPAB258 [1.334 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB258

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paper received ※ 19 May 2021 paper accepted ※ 27 July 2021 issue date ※ 31 August 2021

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THPAB309

New Working Tune Feedback System for TLS

quadrupole, insertion, insertion-device, radiation

4394

S.J. Huang, Y.K. Lin, Y.C. Lin
NSRRC, Hsinchu, Taiwan

TLS storage ring has two sets of working tuning feedback systems: one is used to correct the working tune deviation caused by insertion device U90; another system uses a local trim coil to correct the working tune deviation caused by all insertion devices. This article describes a new working tune feedback system in TLS that can correct the working tune effectively back to the required conditions for operation; the two existing feedback systems do not cause problems. We can both avoid increasing the local radiation dose and decreasing the injection efficiency.

Poster THPAB309 [0.831 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB309

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paper received ※ 15 May 2021 paper accepted ※ 02 July 2021 issue date ※ 23 August 2021

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THPAB311

Using Linear Regression to Model the Parameters of the Flat Wires in TLS-EPU56

injection, undulator, hardware, electron

4399

S.J. Huang, Y.H. Chang, T.Y. Chung
NSRRC, Hsinchu, Taiwan
Y.W. Chen
Academia Sinica, Taipei, Taiwan

Although a theoretical calculation might predict the set currents of the flat wires, which are used to compensate the deviation in the Betatron tune caused by the elliptically polarized undulator (EPU), those set currents must still be tuned in reality. To approach this reality, a strategy of Machine Learning was adopted, which included collecting real-condition data and using a linear-regression model to adjust the parameters of the flat wires. After training the model, the predictions in variables tune x, tune y and beam size x were compared with the required amount of correction of the EPU at various gaps and phases. To prove the feasibility of this method, a test was performed under the real conditions of accelerator Taiwan Light Source (TLS).

Poster THPAB311 [1.226 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB311

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paper received ※ 13 May 2021 paper accepted ※ 28 June 2021 issue date ※ 30 August 2021

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THPAB337

Resonance Control System for the PIP-II IT HWR Cryomodule

cavity, controls, cryomodule, resonance

4446

P. Varghese, B.E. Chase, P.M. Hanlet, H. Maniar, D.J. Nicklaus, S. Sankar Raman
Fermilab, Batavia, Illinois, USA
L.R. Doolittle, S. Paiagua, C. Serrano
LBNL, Berkeley, California, USA

The HWR (half-wave-resonator) cryomodule is the first one in the superconducting section of the PIP-II LINAC project at Fermilab. PIP-II IT is a test facility for the project where the injector, warm front-end, and the first two superconducting cryomodules are being tested. The HWR cryomodule comprises 8 cavities operating at a frequency of 162.5 MHz and accelerating beam up to 10 MeV. Resonance control of the cavities is performed with a pneumatically operated slow tuner which compresses the cavity at the beam ports. Helium gas pressure in a bellows mounted to an end wall of the cavity is controlled by two solenoid valves, one on the pressure side and one on the vacuum side. The resonant frequency of the cavity can be controlled in one of two modes. A pressure feedback control loop can hold the cavity tuner pressure at a fixed value for the desired resonant frequency. Alternately, the feedback loop can regulate the cavity tuner pressure to bring the RF detuning error to zero. The resonance controller is integrated into the LLRF control system for the cryomodule. The control system design and performance of the resonance control system are described in this paper.

Poster THPAB337 [4.426 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB337

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paper received ※ 12 May 2021 paper accepted ※ 26 July 2021 issue date ※ 27 August 2021

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