Keyword: feedback
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MOPGW002 Longitudinal Kicker Design for Sirius Light Source cavity, kicker, HOM, GUI 57
 
  • H.O.C. Duarte, A. Barros
    LNLS, Campinas, Brazil
  
  An overloaded cavity kicker for the Sirius longitudinal bunch-by-bunch feedback system will be presented in this contribution. 4th generation light sources’ lower aperture of vacuum chambers lead to higher cutoff frequencies, jeopardizing the electromagnetic performance of cavities by trapping higher order modes (HOMs) inside the structure. With the objective of damping longitudinal and transverse HOMs without compromising the kicker shunt impedance, solutions as cavity radius reduction, tapered transitions and other geometry changes are discussed herein.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW002  
About • paper received ※ 15 May 2019       paper accepted ※ 17 May 2019       issue date ※ 21 June 2019  
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MOPGW017 Feedback Design for Control of the Micro-Bunching Instability based on Reinforcement Learning bunching, storage-ring, electron, controls 104
 
  • T. Boltz, T. Asfour, M. Brosi, E. Bründermann, B. Härer, P. Kaiser, A.-S. Müller, C. Pohl, P. Schreiber, M. Yan
    KIT, Karlsruhe, Germany
  
  The operation of ring-based synchrotron light sources with short electron bunches increases the emission of coherent synchrotron radiation (CSR) in the THz frequency range. However, the micro-bunching instability resulting from self-interaction of the bunch with its own radiation field limits stable operation with constant intensity of CSR emission to a particular threshold current. Above this threshold, the longitudinal charge distribution and thus the emitted radiation vary rapidly and continuously. Therefore, a fast and adaptive feedback system is the appropriate approach to stabilize the dynamics and to overcome the limitations given by the instability. In this contribution, we discuss first efforts towards a longitudinal feedback design that acts on the RF system of the KIT storage ring KARA (Karlsruhe Research Accelerator) and aims for stabilization of the emitted THz radiation. Our approach is based on methods of adaptive control that were developed in the field of reinforcement learning and have seen great success in other fields of research over the past decade. We motivate this particular approach and comment on different aspects of its implementation.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW017  
About • paper received ※ 15 May 2019       paper accepted ※ 21 May 2019       issue date ※ 21 June 2019  
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MOPGW058 Towards a Sextupole-Free Electron Storage Ring electron, vacuum, impedance, storage-ring 217
 
  • T.-Y. Lee, T. Ha
    PAL, Pohang, Kyungbuk, Republic of Korea
  
  This paper studies if it is possible to build an electron storage ring with no or a small number of sextupole mag-nets. If it is possible, the electron storage ring will be great-ly simplified. For the purpose, two methods are presented in the paper to handle head-tail instability: One is to use dielectric vacuum chamber made of such materials as ceramic or glass to reduce broadband impedance signifi-cantly. Then head-tail instability would be extremely weak. The other method is to install a bunch-by-bunch feedback system to suppress the already weak head-tail instability due to the dielectric vacuum chamber.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW058  
About • paper received ※ 15 May 2019       paper accepted ※ 20 May 2019       issue date ※ 21 June 2019  
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MOPGW071 Resistive Wall Effects in the CLIC Beam Delivery System luminosity, wakefield, collider, vacuum 258
 
  • D. Arominski, A. Latina, D. Schulte
    CERN, Meyrin, Switzerland
  
  Resistive wall wakefields are an important issue to study for future linear colliders. Wakefields in the Beam Delivery System (BDS) might cause severe multi-bunch effects, leading to beam quality and luminosity losses. The resistive wall effects depend on the beam pipe apertures and materials, which are optimised to limit the impact on the beam. This paper presents a study of this problem for the 380 GeV and 3 TeV beam parameters and optics of the Compact Linear Collider’s BDS. First, the optimisation of the beam pipe apertures to limit the impact of resistive wall effect on the beam quality is shown, then the luminosity and its quality are presented. Finally, the proposed design parameters are discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW071  
About • paper received ※ 16 May 2019       paper accepted ※ 20 May 2019       issue date ※ 21 June 2019  
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MOPGW078 Change of Beam Distribution Due to Decoherence in the Presence of Transverse Feedback simulation, octupole, damping, emittance 281
 
  • S.V. Furuseth, X. Buffat
    CERN, Geneva, Switzerland
  • S.V. Furuseth
    EPFL, Lausanne, Switzerland
  
  The effect of Landau damping is often calculated based on a Gaussian beam distribution in all degrees of freedom. The stability of the beam is however strongly dependent on the details of the distribution. The present study focuses on the change of bunch distributions caused by the decoherence of the excitation driven by an external source of noise, in the presence of both amplitude detuning and a transverse feedback. Both multiparticle tracking simulations and theoretical models show a similar change of the distribution. The possible loss of Landau damping driven by this change is discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW078  
About • paper received ※ 08 April 2019       paper accepted ※ 19 May 2019       issue date ※ 21 June 2019  
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MOPGW082 Mitigation of Stray Magnetic Field Effects in CLIC with Passive Shielding shielding, collider, simulation, hadron 293
 
  • C. Gohil, N. Blaskovic Kraljevic, D. Schulte
    CERN, Meyrin, Switzerland
  • P. Burrows
    JAI, Oxford, United Kingdom
  
  Simulations have shown the Compact Linear Collider (CLIC) is sensitive to external dynamic magnetic fields (stray fields) to the nT level. Due to these extremely tight tolerances, mitigation techniques will be required to prevent performance loss. A passive shielding technique is envisaged as a potential solution. A model for passive shielding is presented along with calculations of its transfer function. Measurements of the transfer function of a promising material (mu-metal) that can be used for passive shielding are presented. The validity of passive shielding models in small amplitude magnetic fields is also discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW082  
About • paper received ※ 01 May 2019       paper accepted ※ 20 May 2019       issue date ※ 21 June 2019  
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MOPGW091 Capture and Flat-Bottom Losses in the CERN SPS beam-loading, injection, emittance, impedance 327
 
  • M. Schwarz, A. Lasheen, G. Papotti, J. Repond, E.N. Shaposhnikova, H. Timko
    CERN, Meyrin, Switzerland
  
  Particle losses on the flat bottom of the SPS, the last accelerator in the injector chain of the LHC at CERN, are a strong limitation for reaching the high intensities required by the high luminosity upgrade of the LHC. Two contributions to these losses are investigated in this paper. The first losses occur during the PS-to-SPS bunch-to-bucket transfer, since the bunch rotation in the PS creates halo particles and the bunch does not completely fit into the SPS RF-bucket. The effect of longitudinal shaving in the PS on the beam transmission was recently tested. At high intensities, further capture losses are caused by beam loading in the traveling wave RF system of the SPS, which is partially compensated by the LLRF system, in particular by one-turn delay feedback. While the feedforward system reduces the capture losses, it also increases the losses along the flat bottom due to the RF noise.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW091  
About • paper received ※ 09 May 2019       paper accepted ※ 19 May 2019       issue date ※ 21 June 2019  
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MOPGW098 Iterative Trajectory-Correction Scheme for the Early Commissioning of Diffraction-Limited Light Sources MMI, lattice, simulation, storage-ring 353
 
  • Ph. Amstutz, T. Hellert
    LBNL, Berkeley, USA
  
  The commissioning of diffraction-limited light sources will be significantly affected by the fact that typical lattice designs rely on very strong focussing elements in order to achieve the small emittance goals. Especially in the early-commissioning phase this can render procedures successfully used in the commissioning of existing third-generation light sources ill-suited for the application to these new machines. In this contribution we discuss an iterative approach to the early trajectory correction, based on the well-known pseudo-inversion of a trajectory-response matrix. Measuring this matrix during early commissioning can be cumbersome, so that an algorithm working with the model response matrix of the lattice is desirable. We discuss the stability of the iteration in the presence of lattice errors, resulting in differences between the actual and the model response matrix. Further, Tikhonov regularization is investigated as a means to trade off the RMS trajectory variation against the strength of the required corrector kicks.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW098  
About • paper received ※ 14 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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MOPMP045 RHIC Heavy Ion Operation With Near-Integer Working Point acceleration, controls, operation, power-supply 544
 
  • C. Liu, G.J. Marr, A. Marusic, M.G. Minty, V. Schoefer
    BNL, Upton, Long Island, New York, USA
  
  Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
The interplay of space charge and beam-beam effects limits the beam lifetime at low energies at the Relativistic Heavy Ion Collider (RHIC). To improve the beam lifetime, a near-integer working point (0.096/0.094) was tested at fixed energy and during acceleration. In the demonstration experiments, we observed the benefit of the near-integer working point on beam lifetime, however, did not achieve the desired level of orbit correction. This article will present the experimental results of operation with a near-integer working point, and analyze the causes of the orbit control problem. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPMP045  
About • paper received ※ 14 May 2019       paper accepted ※ 21 May 2019       issue date ※ 21 June 2019  
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MOPRB057 An Approach to Alleviating Heavy Beam Loading Effect on the Synchrotron Machine Through the Existed Low Level RF Feedback System cavity, beam-loading, impedance, simulation 697
 
  • L.-H. Chang, F.Y. Chang, M.H. Chang, S.W. Chang, L.J. Chen, F.-T. Chung, Y.T. Li, M.-C. Lin, Z.K. Liu, C.H. Lo, Ch. Wang, M.-S. Yeh, T.-C. Yu
    NSRRC, Hsinchu, Taiwan
  
  To pursue the highest brightness and intensity of the synchrotron light, the synchrotron machines are pushed to operate with as high as possible of the beam current. To suppress the heavy beam loading effects, the direct RF feedback is currently widely used. This paper provides an another approach to alleviating the heavy beam loading effects on machine operation. Different from the direct RF feedback technique, this approach need not add additional feedback loop to the existed RF feedback system. Applying a proper angle rotation to the I-Q error signals of the cavity voltage, before entering the existed feedback loop, is the only action required in this approach. The paper will explain the working mechanism and investigate the behaviour of this approach, through an example case, with numerical simulation.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB057  
About • paper received ※ 16 April 2019       paper accepted ※ 18 May 2019       issue date ※ 21 June 2019  
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MOPTS085 Commissioning of a New Digital Transverse Damper System at the PSB proton, operation, MMI, hardware 1050
 
  • G.P. Di Giovanni, F. Antoniou, A. Blas, Y. Brischetto, A. Findlay, G. Kotzian, B. Mikulec, G. Sterbini
    CERN, Geneva, Switzerland
  
  At the CERN Proton Synchrotron Booster, PSB, an analog transverse damper system has been in operation since 1999, providing satisfactory operational results with the proton beam supplied by Linac2. As a consequence of the LHC Injectors Upgrade, the PSB will face new challenges imposed by higher intensity, injection and extraction energy. In this framework, the transverse feedback system is subject to an upgrade to adapt to the expected Linac4 beam and to the demands for new features including transverse blow-up, beam excitation for optics measurements and new remote control and monitoring capabilities. The replacement of the aging electronic hardware is also recommended to improve the system maintainability for future years. During 2018 a new digital transverse feedback electronics was installed in the PSB, in parallel with the current operational one, offering for the first time the occasion to demonstrate its performance with beam. Encouraging results were obtained such as the suppression of beam instabilities at all PSB energies and intensities. In this paper we describe the steps undertaken in 2018 in order to commission the system with the main goal to accelerate and extract the highest intensity beams produced at the PSB.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS085  
About • paper received ※ 06 May 2019       paper accepted ※ 18 May 2019       issue date ※ 21 June 2019  
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TUZZPLM2 Status of Automated Optimization Procedures at the European XFEL Accelerator FEL, electron, undulator, status 1212
 
  • S. Tomin
    EuXFEL, Schenefeld, Germany
  • L. Fröhlich, M. Scholz
    DESY, Hamburg, Germany
  
  The European XFEL is in the operational stage since fall 2017. Since then, tuning of the FEL performance (e.g. of the photon pulse energy) has become increasingly important. Due to a large number of parameters to which FEL facilities are highly sensitive and their complex correlations, controlling and optimizing them in a speedy manner is becoming a very important and challenging task. Several automated optimization procedures were developed to optimize the FEL beam quality. In this work, we present the status and the results of these activities, as well as the optimization statistics.  
slides icon Slides TUZZPLM2 [5.882 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUZZPLM2  
About • paper received ※ 13 May 2019       paper accepted ※ 21 May 2019       issue date ※ 21 June 2019  
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TUPMP014 Digital Control System of High Precision Magnet Power Supply for SPring-8-II controls, power-supply, FPGA, synchrotron-radiation 1259
 
  • C. Kondo, K. Fukami, S. Takano, T. Watanabe
    Japan Synchrotron Radiation Research Institute (JASRI), RIKEN SPring-8 Center, Hyogo, Japan
  • T. Fukui, H. Tanaka
    RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
  • S. Nakazawa
    SES, Hyogo-pref., Japan
  • N. Nishimori
    QST, Tokai, Japan
  • C. Saji
    JASRI/SPring-8, Hyogo-ken, Japan
  
  For the SPring-8 upgrade plan, SPring-8-II, a variety of magnet power supplies (PS) from 10 W to larger than 100 kW with a high current stability of about 10 ppm (pk-pk, typ.) are required. In order to develop the PSs within a given time and budget, we plan to use a common control system based on a digital control technology that can be adopted for the variety and the high precision PSs. The system consists of a high-precision analog-digital converter (ADC) circuit and a field programmable gate array (FPGA). Since the precision of the ADC circuit determines the current stability of the PS, we first developed the ADC circuit of high accuracy of less than 10 ppm (pk-pk). A proportional-integral (PI) control logic and a digital pulse width modulation (PWM) function was implemented in the FPGA firmware. These functions can be easily modified for each power supply by a desktop computer. We prototyped a DC power supply equipped with the newly developed digital feedback control system and confirmed that the current fluctuation was suppressed to less than 10 ppm (pk-pk). In the presentation, we will report the current status and future perspective of our power supply development including the evaluation results of the new circuits and the power supply we have developed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPMP014  
About • paper received ※ 16 May 2019       paper accepted ※ 21 May 2019       issue date ※ 21 June 2019  
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TUPMP015 Magnet Power Supply Calibration with a Portable Current Measuring Unit at the J-PARC Main Ring power-supply, operation, timing, controls 1263
 
  • K. Miura, Y. Kurimoto, Y. Morita, D. Naito, T. Oogoe, T. Shimogawa
    KEK, Ibaraki, Japan
  • Y. Kuniyasu
    Mitsubishi Electric System & Service Co., Ltd, Tsukuba, Japan
  • K. Ooya
    SANKYU PLANT TECHNO CO., LTD., 6-5-3, Kachidoki, Japan
  • R. Sagawa
    Universal Engineering, Ibaraki-ken, Japan
  
  In the J-PARC MR, 96 bending magnets (BMs) are used in total. They are divided into 6 groups of 16 BMs. The 16 BMs in each group are connected in series and driven by a single power supply. Since all 96 BMs are symmetrically located in the ring, the magnet currents regulated by the 6 power supplies need to be same. Each power supply performs output current feedback control using electronic circuits including analog amplifications and AD / DA conversions. Due to individual differences of the electronic circuits, output current is generally expected to be different for each power supply. Therefore, we developed a current measurement unit with the portable DCCT as an independent reference. Further, we measured the magnet currents regulated by the 6 BM power supplies using the unit. We report the details of the unit as well as the results of the current measurements.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPMP015  
About • paper received ※ 14 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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TUPMP046 Improvement the Bending Magnet Power Supply Performance for TPS Storage Ring power-supply, storage-ring, controls, photon 1353
 
  • B.S. Wang, C.H. Huang, J.C. Huang, C.Y. Liu, K.-B. Liu, Y.S. Wong
    NSRRC, Hsinchu, Taiwan
  
  In the TPS (Taiwan Photon Source) facility, current stability of the electron beam depends on the bending magnet power supply and an orbit FOFB system to compensate the magnetic field. Due to the output current stability of the bending magnet power supply drifts with temperature so the orbit FOFB system should be applied to fine tune magnetic field and the photon beam should circulate in storage ring. In this paper, to stabilize the temperature of regulation circuit’s temperature box of the bending magnet power supply, the long-term output current stability is improve from ± 50ppm to ± 10ppm, and orbit FOFB system substantially reduce the tune X of beam position, effectively increasing the beam current stability and quality.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPMP046  
About • paper received ※ 12 April 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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TUPGW014 Characterization and Implementation of the Cryogenic Permanent Magnet Undulator CPMU17 at Bessy II undulator, vacuum, laser, operation 1415
 
  • J. Bahrdt, W. Frentrup, S. Gottschlich, S. Grimmer, M. Huck, C. Kuhn, A. Meseck, C. Rethfeldt, M. Scheer, B. Schulz
    HZB, Berlin, Germany
  • E.C.M. Rial
    DLS, Oxfordshire, United Kingdom
  
  In fall 2018, the cryogenic undulator CPMU17 was installed in BESSY II. Before installation, the undulator was characterized with an in-vacuum Hallprobe bench and an in-vacuum moving wire. Both systems were developed at HZB. The commissioning of the device included the orbit and tune corrections, optimization of the injection, characterization of the heat dissipation, tuning the Landau cavities for a reduction of the heat dissipation in the taper sections (temperatures below 60°C) and testing of the machine protection system. The undulator is ready to deliver light for beamline commissioning. Spectral tuning on a high undulator harmonic (longitudinal taper and alignment of e-beam orbit and undulator axis) will be done as soon as the DCM is operational.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPGW014  
About • paper received ※ 14 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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TUPGW032 Mode-Locked Pulse Oscillation of a Self-Resonating Enhancement Optical Cavity cavity, laser, resonance, controls 1471
 
  • Y. Hosaka
    QST/Takasaki, Takasaki, Japan
  • Y. Honda, T. Omori, J. Urakawa
    KEK, Ibaraki, Japan
  • A. Kosuge
    ISSP, Kashiwa-shi, Japan
  • K. Sakaue
    The University of Tokyo, The School of Engineering, Tokyo, Japan
  • T. Takahashi
    Hiroshima University, Graduate School of Science, Higashi-Hiroshima, Japan
  • Y. Uesugi
    Tohoku University, Institute of Multidisciplinary Research for Advanced Materials, Sendai, Japan
  • M. Washio
    Waseda University, Tokyo, Japan
  
  A power enhancement optical cavity is a compelling means of realizing a pulsed laser with a high peak power and high repetition frequency, which is not feasible using a simple amplifier scheme. However, a precise feedback system is necessary for maintaining the narrow resonance condition of the optical cavity; this has become a major technical issue in developing such cavities. We have developed a new approach that does not require any active feedback system, by placing the cavity in the outer loop of a laser amplifier. We report on the first demonstra-tion of a mode-locked pulse oscillation using the new system.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPGW032  
About • paper received ※ 15 April 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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TUPGW053 Simulations of the Injection Transient Instabilities for the High Energy Photon Source injection, simulation, lattice, storage-ring 1524
 
  • Z. Duan, N. Wang, H.S. Xu
    IHEP, Beijing, People’s Republic of China
  
  Funding: Work supported by Natural Science Foundation of China (No.11605212).
A "charge recovery in booster" scheme* was proposed to deliver the full charge bunches for the swap-out injection of the High Energy Photon Source. In this scheme, the booster is employed also as a full energy accumulator ring to capture the high charge bunch extracted from the storage ring via merging with the small charge bunch accelerated in the booster, after enough damping in the booster for about 20 ms, the recovered full charge bunch is re-injected into the storage ring. This scheme avoids the challenges to accelerate a bunch charge of ~ 15 nC, and is cost effective compared to building a dedicated 6 GeV accumulator ring. However, there will be a period of time during injection that one bunch is missing in the storage ring, which inevitably introduces some injection transients. Since "transparency" to the user experiments is a desired feature of injection schemes for next generation diffraction-limited storage rings, the injection transient effects are simulated for the proposed injection scheme, and how it would affect the user experiments are carefully evaluated.
* Z. Duan, et al., "The swap-out injection scheme for the High Energy Photon Source", Proc. IPAC’18, THPMF052 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPGW053  
About • paper received ※ 15 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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TUPGW092 Working Impedance Model and Its Effect on the Intensity Limitation of Petra-IV Storage Ring impedance, cavity, emittance, storage-ring 1623
 
  • Y.-C. Chae
    DESY, Hamburg, Germany
  
  We made sufficient progress in modeling the imped-ance of the PETRA-IV storage ring. The result was ap-plied to estimate the impedance-based single and multi-bunch intensity limit. Due to the extremely small emit-tance of the beam the intrabeam scattering (IBS) effects will be significant unless they are reduced by bunch lengthening. The 3rd harmonic cavity was proposed to dilute the bunch density which resulted in the small syn-chrotron frequency with a large spread. Because of the complexity introduced by impedance and harmonic cavity we used broadband impedance up to 200 GHz to compute the parameters such as bunch length and energy spread at different currents. We found that the microwave instability started very early in current less than 0.5 mA. Even if it is small, the prediction by tracking simulation was consistent with another diffraction-limited storage ring (DLSR) when the Keil-Schnell criterion was used to predict one from the other. Then, we present the single-bunch current limit which had included the effect of geometric and resistive wall impedances of the NEG-coated chamber. Finally, we present the emittance and lifetime which can be realistically achieved in the ring with the above collective effects included.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPGW092  
About • paper received ※ 14 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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TUPRB053 Injector Physics Design at SHINE laser, electron, FEL, emittance 1801
 
  • Z. Wang, M.H. Zhao
    SINAP, Shanghai, People’s Republic of China
  • Q. Gu
    SSRF, Shanghai, People’s Republic of China
  • G.L. Wang
    DICP, Dalian, People’s Republic of China
  
  As a CW x-ray free electron laser facility, SHINE has a high requirement on the electron beam quality in the linac, as well as in the injector. SHINE injector consists of a 162.5 MHz normal conducting VHF gun, a NC 1.3 GHz RF buncher, a one cavity SC cryomodule, an eight cavity SC cryomodule and 3 solenoids along the injector layout. Some beam diagnostic element are inserted in the layout as well. In this paper, we try to introduce the injector physics design at shine.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPRB053  
About • paper received ※ 15 May 2019       paper accepted ※ 20 May 2019       issue date ※ 21 June 2019  
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TUPTS029 The New Eddy Current type Septum Magnets for Upgrading of Fast Extraction in Main Ring of J-PARC operation, septum, extraction, experiment 1997
 
  • T. Shibata, K. Ishii, H. Matsumoto, T. Sugimoto
    KEK, Ibaraki, Japan
  • K. Fan
    HUST, Wuhan, People’s Republic of China
  • K. Hamano
    Nichicon (Kusatsu) Corporation, Shiga, Japan
  
  The J-PARC Main Ring (MR) is working on imporved beam to 750 kW by shorting the repetition period from 2.48 s to 1.3 s which we call 1Hz operation. The septum magnets for fast extraction in MR will be improved to the new septum magnets which can operate 1Hz. The new magnets will be installed to MR in 2021. In this poster we will report about the new low field septum magnet for the fast extraction. The present septum magnets are conventional type. Therefore, we have problem in durability of thin septum coil by its magnetic vibration, and large leakage field at the exit of the circulating beam duct. The new septum magnets are eddy current type. The eddy current type does not have septum coil, but has a thin septum plate. We can expect that there is no problem in durability of septum coil, and leakage field can be reduced. The output of the present power supply are pattern current which of flat top is 10 ms width, the new one is short pulse which of one is 10 us. The short pulse consists of fundamental and 3rd harmonic sin-wave pulse. We can expect that the flatness and reproducibility of flat top current can be improved. We confirmed that 1Hz operation and high accuracy of its output current and magnetic field with the new septum magnet system. We had some problem in unexpected instability of output current. In this report we also summarize the measure against the instabillity.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS029  
About • paper received ※ 26 April 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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TUPTS045 Simulation Analysis of LLRF Feedforward Compensation to Beam Loading for CiADS LINAC cavity, simulation, beam-loading, controls 2027
 
  • X.C. Xu, J.Y. Ma
    IMP/CAS, Lanzhou, People’s Republic of China
  
  A simulation is coded to calculate the beam loading in the cavity of CiADS and the response of the LLRF system. In the pulse operating mode, the fluctuation of amplitude and phase of the cavity field contributed by the transient beam loading is traced. During the simulation the effect of beam current fluctuation, and timing jitter were determined. The deviation margin of relational parameters is lined out to meet the requirement for cavity stability with amplitude 0.1% and phase 0.1°.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS045  
About • paper received ※ 15 May 2019       paper accepted ※ 21 May 2019       issue date ※ 21 June 2019  
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WEPMP008 A Consideration on the Transfer Function Between RQ Field and Slow Extraction Spill in the Main Ring of J-Parc extraction, experiment, operation, controls 2315
 
  • K. Okamura, Y. Arakaki, S. Murasugi, R. Muto, Y. Shirakabe, M. Tomizawa, E. Yanaoka
    KEK, Ibaraki, Japan
  • T. Kimura
    J-PARC, KEK & JAEA, Ibaraki-ken, Japan
  
  A 30 GeV proton beam accelerated in the J-PARC Main Ring (MR) is slowly extracted by the third integer reso-nant extraction and delivered to the hadron experimental facility. Increasing the duty of beam spill is one of the important issues in the slow extraction system. In the MR, the spill feedback system utilizing a digital signal processor (DSP) combined with EQ and RQ magnet is used to smooth the spill, where EQ defines a rough out-line of the slow extraction shape and RQ is used for the ripple cancelling. In this study, frequency domain charac-teristics between the current of RQ magnet and the beam spill was investigated by driving the RQ magnet with sinusoidal current, so that the transfer function from the current of RQ magnet to the spill signal is delivered.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPMP008  
About • paper received ※ 15 May 2019       paper accepted ※ 20 May 2019       issue date ※ 21 June 2019  
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WEPGW092 Nanosecond-Latency Sub-Micron Resolution Stripline Beam Position Monitor Signal Processor for CLIC detector, extraction, kicker, luminosity 2705
 
  • R.L. Ramjiawan, D.R. Bett, P. Burrows, G.B. Christian, C. Perry
    JAI, Oxford, United Kingdom
  
  A high-resolution, low-latency stripline beam position monitor (BPM) signal processor has been developed for use in an intra-train feedback system for the Compact Linear Collider (CLIC). The processor was designed to have extremely low latency of order nanoseconds and a target position resolution of order 1 micron. The processor consists of a pair of diodes to form the difference and sum of a pair of stripline BPM inputs with microstrip filters to reduce out-of-band noise. The assembled prototype was optimized for use with the electron beam in the extraction line of the Accelerator Test Facility at the High Energy Accelerator Research Organization (KEK) in Japan but the underlying design is readily scaleable to a higher frequency response relevant for CLIC. A latency of 3 ns was measured in a testbench setup. We report the results of performance tests with beam in which the position resolution was measured to be c. 325 nm.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPGW092  
About • paper received ※ 15 May 2019       paper accepted ※ 21 May 2019       issue date ※ 21 June 2019  
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WEPRB003 Parametric Pumped Oscillation by Lorentz Force in Superconducting Rf Cavity cavity, controls, acceleration, klystron 2798
 
  • K. Fong, R. Leewe
    TRIUMF, Vancouver, Canada
  
  Mechanical instabilities have been observed in superconducting RF cavities, when multiple cavities are driven by a single klystron and these cavities are regulated by vector-summing the outputs from these cavities. A nonlinear theory has been developed to study the source of this mechanical instability, which is due to the coupling between Lorentz force detuning and mechanical oscillation by parametric pumping. Analytical and numerical analysis of this model show regions of stability, limit cycles and instabilities. These results are in agreement with the observed oscillations by TRIUMF eLinac Acceleration Module.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB003  
About • paper received ※ 13 May 2019       paper accepted ※ 20 May 2019       issue date ※ 21 June 2019  
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WEPRB026 Simulations of Beam Loading Compensation in a Wideband Accelerating Cavity Using a Circuit Simulator Including a LLRF Feedback Control controls, cavity, simulation, vacuum 2863
 
  • F. Tamura, M. Nomura, T. Shimada, M. Yamamoto
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
  • M. Furusawa, K. Hara, K. Hasegawa, C. Ohmori, Y. Sugiyama, M. Yoshii
    KEK, Tokai, Ibaraki, Japan
  
  Magnetic alloy cavities are employed in the J-PARC RCS to generate high accelerating voltages. The cavity, which is driven by a vacuum tube amplifier, has a wideband frequency response and the beam loading in the cavity is multiharmonic. Therefore, the tube must generate a multiharmonic output current. An LTspice circuit model is developed to analyze the vacuum tube operation and the compensation of the multiharmonic beam loading. The model includes the cavity, tube amplifier, beam current, and LLRF feedback control. The feedback control consists of the I/Q demodulator including low pass filters, PI control, and I/Q modulator. In this presentation, we present the implementation of the LLRF functions in the LTspice simulations. The preliminary simulation results are also presented. The simulations fairly agree with the beam test results.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB026  
About • paper received ※ 23 April 2019       paper accepted ※ 20 May 2019       issue date ※ 21 June 2019  
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WEPTS044 Instability Latency in the LHC octupole, experiment, damping, simulation 3204
 
  • S.V. Furuseth, D. Amorim, S.A. Antipov, X. Buffat, N. Mounet, E. Métral, B. Salvant
    CERN, Geneva, Switzerland
  • S.V. Furuseth, T. Pieloni, C. Tambasco
    EPFL, Lausanne, Switzerland
  
  The Large Hadron Collider (LHC) has experienced multiple instabilities that occur between minutes and hours after the last modification of the machine settings. The existence of instabilities with high latency has been reproduced also in simulations. Dedicated experiments, injecting a controlled noise into the beam, have now been performed to discover the dependence of this latency on key parameters. The results seem compatible with a mechanism linked to a steady and slow modification of the transverse beam distribution leading to a loss of Landau damping.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS044  
About • paper received ※ 30 April 2019       paper accepted ※ 21 May 2019       issue date ※ 21 June 2019  
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WEPTS049 Flat-Bottom Instabilities in the CERN SPS simulation, impedance, HOM, LLRF 3224
 
  • M. Schwarz, K. Iliakis, A. Lasheen, G. Papotti, J. Repond, E.N. Shaposhnikova, H. Timko
    CERN, Meyrin, Switzerland
  
  At beam intensities of 2.6·1011 protons per bunch, required at SPS injection for the High Luminosity LHC beam, longitudinal instabilities can degrade the beam quality delivered by the SPS, the LHC injector at CERN. In this paper, we concentrate on beam instability at flat bottom. The dependence of the instability threshold on longitudinal emittance and LLRF system settings was measured, to help identify the impedance driving this instability. While reducing the longitudinal emittance reduces the losses at injection, it can drive the beam unstable. The LLRF system of the SPS (partially) compensates beam loading, but also affects the instability. The effect of the different LLRF systems (feedback, feedforward, phase loop and longitudinal damper) and fourth harmonic RF system on the instability was investigated. The measurements are compared with simulations performed with the longitudinal tracking code BLonD.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS049  
About • paper received ※ 10 May 2019       paper accepted ※ 19 May 2019       issue date ※ 21 June 2019  
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THPGW084 Corrections of Klystron Output Pulse in SW Accelerator Testing klystron, controls, linac, ISOL 3772
 
  • M.H. Nasr, S.G. Tantawi
    SLAC, Menlo Park, California, USA
  
  Accelerator testing requires a good control over the shape of the used pulse. Usually, flat or stepped square pulses are used for testing. Producing a perfectly flat output pulse from the klystron can be challenging especially for testing standing wave (SW) accelerators. SW accelerator structures reflect high power back to the klystron and no isolator can withstand the reflected power level for high gradient operation. This results in a distorted output pulse from the Klystron. We developed a modulation technique that solves this problem using a negative feedback loop. This technique can also overcome a poor modulator performance and other system errors. The pulse correction feedback was successfully implemented for high gradient SW accelerator testing at SLAC and KEK.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPGW084  
About • paper received ※ 24 May 2019       paper accepted ※ 24 May 2019       issue date ※ 21 June 2019  
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THPRB004 Hardware and Firmware Development for Enhanced Orbit Diagnostics at the Australian Synchrotron controls, EPICS, FPGA, diagnostics 3802
 
  • S. Chen, R.B. Hogan, A. Michalczyk, A.C. Starritt, Y.E. Tan
    AS - ANSTO, Clayton, Australia
  
  The Enhanced Orbit Diagnostic (EOD) features will be an expansion to the existing Fast Orbit Feedback (FOFB) system that is currently in operation. The new system will add the capability of online cor-rector-to-position response matrix calculation; this will significantly reduce the required measurement time. The new features will allow the injection of PRBS noise or sinusoidal signals into correctors, to characterise and monitor the FOFB system’s parameters and performance and track it over time. The system will be built based on a Xilinx ZYNQ Sys-tem-on-Module (SOM) mounted on an in-house designed motherboard to which the existing FOFB daughter board is plugged into.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB004  
About • paper received ※ 15 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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THPRB005 Orbit Feedback and Beam Stability at the Australian Synchrotron FPGA, controls, operation, EPICS 3805
 
  • A.C. Starritt, A. Pozar, Y.E. Tan
    AS - ANSTO, Clayton, Australia
  
  The Australian Synchrotron (AS) is a 3rd generation light source which has been in operation since 2006. Measurement of the storage ring’s beam position is provided by 98 beam position monitors, and corrections can be applied using 42 horizontal and 56 vertical slow corrector magnets, and 42 horizontal and 42 vertical fast corrector magnets. This paper provides a background describing the feedback strategies adopted at the AS leading to the current integrated orbit feedback system, together with a description of the beam position analyse techniques currently in use. It will also highlight some of the issues encountered with the system and how they were overcome. The paper also describes planned improvements, including the enhanced orbit diagnostics functionality we are intending to introduce in the next 12 months.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB005  
About • paper received ※ 14 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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THPRB007 Ponderomotive Instability of Self-Excited Cavity cavity, resonance, SRF, controls 3808
 
  • S.R. Koscielniak
    TRIUMF, Vancouver, Canada
  
  The electro-magnetic fields within a super-conducting radio frequency (SRF) cavity can be sufficiently strong to deform the cavity shape, which may lead to a ponderomotive instability. Stability criteria for the self-excited mode of cavity operation were given in 1978 by Delayen. The treatment was based on the Routh-Hurwitz analysis of the characteristic polynomial. With the Wolfram modern analytical tool, "Mathematica", we revisit the criteria for an SRF cavity equipped with amplitude and phase loops and a single microphonic mechanical mode.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB007  
About • paper received ※ 14 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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THPRB010 Ponderomotive Instability of Generator-Driven Cavity cavity, resonance, controls, SRF 3820
 
  • S.R. Koscielniak
    TRIUMF, Vancouver, Canada
  
  The electro-magnetic fields within a super-conducting radio frequency (SRF) cavity can be sufficiently strong to deform the cavity shape, which may lead to a ponderomotive instability. Stability criteria for the generator-driven mode of cavity operation were given in 1971 by Schulze. The treatment side-stepped the Routh-Hurwitz analysis of the characteristic polynomial. With the Wolfram modern analytical tool, ’Mathematica’, we revisit the criteria for an SRF cavity equipped with amplitude and phase loops and a single microphonic mechanical mode.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB010  
About • paper received ※ 14 May 2019       paper accepted ※ 18 May 2019       issue date ※ 21 June 2019  
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THPRB011 Norm-optimal Iterative Learning Control to Cancel Beam Loading Effect on the Accelerating Field controls, beam-loading, cavity, simulation 3824
 
  • Z. Shahriari, K. Fong
    TRIUMF, Vancouver, Canada
  • G.A. Dumont
    UBC, Vancouver, Canada
  
  Iterative learning control (ILC) is an open loop control strategy that improves the performance of a repetitive system through learning from previous iterations. ILC can be used to compensate for a repetitive disturbance like the beam loading effect in resonators. In this work, we aim to use norm-optimal ILC to cancel beam loading effect. Norm-optimal ILC updates the control signal with the goal of minimizing a performance index, which results in monotonic convergence. Simulation results show that this controller improves beam loading compensation compared to a PI controller.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB011  
About • paper received ※ 14 May 2019       paper accepted ※ 19 May 2019       issue date ※ 21 June 2019  
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THPRB020 A Feedback System to Minimize the Electron Bunch Arrival-Time Jitter Between Femtosecond Laser Pulses and Electron Bunches for Laser-Driven Plasma Wakefield Accelerators laser, plasma, electron, optics 3843
 
  • S. Mattiello, A. Penirschke
    THM, Friedberg, Germany
  • H. Schlarb
    DESY, Hamburg, Germany
  
  Funding: The work of S. Mattiello is supported by the German Federal Ministry of Education and Research (BMBF) within the Project MAKE-PWA.
In a laser driven plasma based particle accelerator a stable synchronization of the electron bunch and of the plasma wake field in the range of less than 2 fs is necessary in order to optimize the acceleration. For this purpose we are developing a new shot to shot feedback system with a time resolution of less than 1 fs*. We plane to generate stable THz pulses by optical rectification of a fraction of the plasma generating high energy laser pulses in a nonlinear lithium niobate crystal. With these pulses we will energy modulate the electron bunches shot to shot before the plasma to achieve the time resolution. In this contribution we will focus on realization aspects of the shot to shot feedback system and the lithium niobate crystal itself. Here we compare different approximations for the modeling of the generation dynamics (second order or first order calculation) and of the dielectric function (influence of the dispersion relation, of the free carries generated by the pump adsorption and their saturation, depletion of the pump) in order to investigate the importance of a detailed description of the optical properties for the THz generation.
*The feedback system will be tested at the Accelerator R&D facility SINBAD (Short Innovative Bunches and Accelerators at DESY). 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB020  
About • paper received ※ 15 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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THPRB023 An MTCA.4 Based Position Feedback Application Using Laserinterferometers laser, experiment, controls, interface 3853
 
  • K.P. Przygoda, L. Butkowski, S. Pfeiffer, H. Schlarb, P. Wiljes
    DESY, Hamburg, Germany
  
  To perform experiments on the nanometer scale at high brilliant x-ray light sources, it is highly recommended to have the mechanical components of the experiment, like lenses, mirrors and samples, as stable as possible. Since these components need to move from nanometer up to millimeter range they cannot be stabilized by only using rigid structures. For that reason an active stabilization system with fast and precise sensors needs to be developed. Here a Laserinterferometer is used, which provides picometer resolution at several MHz sample rate. In this paper we will present a laboratory setup which consists of a 6-slot Micro Telecommunication Computing Architecture generation 4 (MTCA.4) crate with standard components such MicroTCA carrier hub (MCH), central processing unit (CPU), power supply (PS) and cooling unit (CU). The Interferometer application has been setup with Deutsches Elektronen-Synchrotron (DESY) advanced mezzanine card (DAMC-FMC20) data processing unit, DESY Field Programmable Gate Array (FPGA) mezzanine card (DFMC-UNIO) universal input and output extension and DESY rear transition module (DRTM-PZT4) piezo driver. The encoder signals given by the interferometer controller are processed within the FPGA and then forwarded to the piezo amplifier RTM-board. The signal processing application includes decoding the digital feedback signal, calculating the coordinate transform for specific experimental setups and closed-loop operation based on a proportional integral derivative (PID) controller. The first results of the laboratory setup are demonstrated and briefly discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB023  
About • paper received ※ 12 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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THPRB033 Development Status of RF Reference Phase Stabilization System for SuperKEKB Injector LINAC linac, controls, photon, distributed 3879
 
  • N. Liu, B. Du
    Sokendai - Hayama, Hayama, Japan
  • D.A. Arakawa, H. Katagiri, T. Kobayashi, T. Matsumoto, S. Michizono, T. Miura, F. Qiu, Y. Yano
    KEK, Ibaraki, Japan
  • T. Matsumoto, T. Miura, F. Qiu
    Sokendai, Ibaraki, Japan
  
  SuperKEKB injector linear accelerator (LINAC) has 600 m beam lines which consist of 8 sectors. The 2856 MHz RF reference signals are distributed to each sector with long phase stabilized optical fiber (PSOF). The RF reference phase stability requirement is estimated to be 0.2°(RMS) corresponding to 200 fs. The prototype of RF reference phase stabilization system with single mode optical circulator was implemented and demonstrated in the laboratory. The returned phase drift is compensated by a piezo-driven fiber stretcher. The transmitted phase through 120 m PSOF is stabilized to 41 fs (pk-pk), which fulfilled the requirement. This paper introduces the RF reference phase stabilization system and reports the preliminary feedback result.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB033  
About • paper received ※ 15 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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THPRB037 Improved Frequency Characteristics Using Multiple Stripline Kickers kicker, controls, pick-up, extraction 3893
 
  • T. Toyama, A. Kobayashi, H. Kuboki, M. Okada
    KEK, Tokai, Ibaraki, Japan
  
  One of the important ingredient in the intra-bunch transverse feedback is a kicker. The frequency characteristics of the kicker suffers from the transit-time factor, sin(kl)/kl. We examine the frequency characteristics of multiple kickers system. Relation between the excitation patterns of the multiple kickers and the frequency characteristics are presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB037  
About • paper received ※ 23 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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THPRB042 Stability Research Progress on High-power Pulse Modulator for SXFEL-UF controls, FEL, FPGA, network 3904
 
  • Q. Yuan, M. Gu, Y.F. Liu, J. Tong, Y. Wu
    SINAP, Shanghai, People’s Republic of China
  
  Funding: Supported by the National Natural Science Foundation of China(11675250)
Abstract: SXFEL-UF(Shanghai Soft X-ray Free Electron Laser User Facility) under construction presently demands higher energy stability. Stability of pulse modulator feeding power for klystron plays an utmost important role in energy stability and occupy dominant factors in bringing influences in stability of RF power. Presently, stability of high-power pulse modulator of LINAC (Linear Accelerator) is on the level of 0.1% to 0.05% usually. In order to meet the higher stability requirements, it is very necessary for close-loop feedback control techniques instead of traditional open-loop to be applied in the modulator design. The stability controller adopts double control-loops techniques which feedback signals are respectively from PFN(Pulse Forming Network) and pulse transformer in oil tank. In addition, the paper also introduces recent progress on high stability CCPS research(Capacitor Charging Power Supply), which brings direct impact on the stability of modulator. In comparison with the former close-loop design, high stability CCPS design takes the overall modulator stability into full consideration. And the feedback control algorithm utilized to adjust PWMs for full bridge switch is implemented in the CCPS controller directly rather than modulator controller independent of CCPS. It is expected to obtain 0.01% stability by taking the above measures. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB042  
About • paper received ※ 06 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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THPRB054 Design of a Ultrafast Stripline Kicker for Bunch-by-Bunch Feedback kicker, FEL, impedance, HOM 3931
 
  • J. Wang, P. Li, D. Wu, D.X. Xiao, L.G. Yan
    CAEP/IAE, Mianyang, Sichuan, People’s Republic of China
  
  Lorentz force detuning and beam loading effect of the rf cavities will induce a slope of the cavity gradient. Combed with the cavity misalignments, transverse position of subsequent bunches will differ from each other. The CAEP THz Free Electron Laser facility(CTFEL) will have a fast transverse bunch-by-bunch feedback system on its test beamline, which is used to correct the beam position differences of individual bunches in the macro-pulses. The time response of the kicker is rigid for the interval of the micro-pulses is 18.5ns and will upgrade to about 2 ns, requiring impedance matching of the kicker with the power source and transmission system in a high bandwidth. Also, the electromagnetic field must reach the requirements of the beam parameters. In this paper, the structure design and the optimization of the geometric parameters of the ultrafast stripline kicker is presented. The characteristic impedance, transmission characteristics, field consistency are analyzed and optimized. And the feedback signal generation scheme for continuous bunch trains was proposed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB054  
About • paper received ※ 14 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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THPRB062 New Orbit Correction Method Based on SVDC Algorithm for Ring Based Light Sources lattice, controls, simulation, photon 3943
 
  • X.Y. Huang, J.S. Cao, Y.Y. Du, Y.H. Lu, H.Z. Ma, Y.F. Ma, Y.F. Sui, S.J. Wei, Y. Wei, Q. Ye, X.E. Zhang, D.C. Zhu
    IHEP, Beijing, People’s Republic of China
  
  Funding: Union Foundation of excellent post-doctoral of China
Orbit feedback system is essential for realizing the exceeding beam stability in modern ring based light sources. Most advanced light sources adopt the global correction scheme by using singular value decomposition (SVD) algorithm. In this paper, a new SVD with constraints method (SVDC) is proposed to correct the global and local orbit simultaneously. Numerical simulations are presented with the case of High Energy Light Source (HEPS) by comparing classic algorithms. The results show that SVDC is very effective for orbit correction and very easy to implement. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB062  
About • paper received ※ 09 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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THPRB082 The CERN SPS Low Level RF upgrade Project cavity, LLRF, controls, acceleration 4005
 
  • G. Hagmann, P. Baudrenghien, J.D. Betz, J. Egli, G. Kotzian, M. Rizzi, L. Schmid, A. Spierer, T. Włostowski
    CERN, Meyrin, Switzerland
  • F.J. Galindo Guarch
    Universitat Politécnica de Catalunya, Barcelona, Spain
  
  The High Luminosity LHC project (HL-LHC) calls for the doubling of the beam intensity injected from the Super Proton Synchrotron (SPS). This is not possible with the present RF system consisting of four 200 MHz cavities. An upgrade was therefore launched, consisting of the installation of two more cavities during the machine shutdown in 2019-2020 (LS2). Installation of more cavities requires the installation of extra Low Level RF (LLRF) electronics. The present LLRF system consists of the original equipment installed in the 1970s, plus some additions dating from the late 1990s when the SPS was commissioned as LHC injector. The High-Power RF up-grade has motivated a complete renovation of the LLRF during LS2; use of a MicroTCA platform, use of a digital deterministic link for synchronization (the so-called White Rabbit), use of an absolute clock for the processing, new algorithms for reducing the cavity impedance, and a complete re-design of the beam control loops and slip-stacking.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB082  
About • paper received ※ 13 May 2019       paper accepted ※ 19 May 2019       issue date ※ 21 June 2019  
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THPRB092 Reduction of Beam Induced RF-Heating in the Horizontal Stripline Kicker at the TPS kicker, impedance, storage-ring, damping 4035
 
  • P.J. Chou, C.K. Chan, C.-C. Chang, K.T. Hsu, K.H. Hu, C.K. Kuan, I.C. Sheng
    NSRRC, Hsinchu, Taiwan
  
  In preparation for 500 mA operation at the Taiwan Pho-ton Source (TPS), we redesigned the horizontal stripline kicker for the beam feedback system to gain a smaller loss factor with higher shunt impedance. We introduced ground fenders (see Fig. 1) to this new design which resulted in the reduction of the loss factor and substantial increase of the kicker shunt impedance. The transverse profile of the kicker electrodes was matched to the race-track beam pipe in the straight sections to minimize broadband impedance. The ground fenders can reduce the leakage of image currents through the gaps between the two strip line electrodes and also help to achieve a better impedance matching for the TEM modes in the transmission lines formed by the stripline electrodes and beam pipe in the kicker. The RF design and analysis of trapped resonant modes in the kicker were simulated by the 3-D electromagnetic code GdfidL [1]. Results of the RF design and analysis of trapped resonant modes will be discussed together with analytical estimates of coupled bunch instabilities at a beam current of 500 mA.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB092  
About • paper received ※ 17 April 2019       paper accepted ※ 19 May 2019       issue date ※ 21 June 2019  
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THPRB094 Study of the System Stability for the Digital Low Level RF System Operated at High Beam Currents cavity, LLRF, controls, simulation 4042
 
  • Z.K. Liu, F.Y. Chang, L.-H. Chang, M.H. Chang, S.W. Chang, L.J. Chen, F.-T. Chung, Y.T. Li, M.-C. Lin, C.H. Lo, Ch. Wang, M.-S. Yeh, T.-C. Yu
    NSRRC, Hsinchu, Taiwan
  
  The purpose of a Low-Level Radio Frequency (LLRF) system is to control the amplitude and phase of the field in the accelerating cavity. A digital LLRF (DLLRF) system will be installed in the Taiwan Photon Source (TPS) storage ring in 2019. The system stability depends much on the feedback parameters. An instability of the cavity voltage controlled by a DLLRF was observed during machine tests with high beam current and low feedback gain. A simulation model for the digital LLRF system with beam-cavity interaction was developed to investigate this instability and simulations and machine test results will be presented here.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB094  
About • paper received ※ 07 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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THPRB096 Real-Time Beam Orbit Stabilisation to 200 Nanometres in Single-Pass Mode Using a High-Precision Dual-Phase Feedback System extraction, collider, electron, real-time 4049
 
  • D.R. Bett, P. Burrows, G.B. Christian, C. Perry, R.L. Ramjiawan
    JAI, Oxford, United Kingdom
  
  A high-resolution, low-latency, stripline beam position monitor (BPM) system has been developed for use at particle accelerators and beamlines that operate with trains of particle bunches with bunch separations as low as several tens of nanoseconds, such as future linear electron-positron colliders and free-electron lasers. The system consists of fast analogue stripline BPM signal processors input to a custom FPGA-based digital feedback board which drives a pair of kickers local to the BPMs and nominally orthogonal in phase in closed-loop feedback mode, thus achieving both beam position and angle stabilisation. The feedback system was tested with the electron beam in the extraction line of the Accelerator Test Facility at the High Energy Accelerator Research Organization (KEK) in Japan. Recent upgrades to the BPMs have increased the single-shot, real-time position resolution of the system to ~150 nm for a beam charge of 1.3 nC. We report the latest results which demonstrate the feedback system operating at this resolution limit and a beam stabilisation performance of 200 nm.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB096  
About • paper received ※ 13 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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THPRB104 Improvements in Long-Term Orbit Stability at NSLS-II operation, photon, controls, storage-ring 4070
 
  • Y. Hidaka, A. Caracappa, Y. Hu, B. Podobedov, R.M. Smith, Y. Tian, G.M. Wang
    BNL, Upton, Long Island, New York, USA
  
  Funding: The study is supported by U.S. DOE under Contract No. DE-SC0012704.
We report our latest efforts to further improve long-term orbit stability at NSLS-II, on top of what is already provided by fast orbit feedback (FOFB) system. A DC local bump generation program, only utilizing RF beam position monitors (BPM) and compatible with FOFB, was first implemented and deployed in operation successfully, allowing on-demand fine adjustments of beamline source positions and angles. Then we introduced a simple feedback version that performs these bump corrections automatically as needed to maintain the sources within in 1 um/urad for select beamlines. In addition, an RF frequency feedback was also implemented to improve stability for 3-pole wigglers and bending magnet users. As a parallel effort, X-ray BPMs were included in a local feedback system to stabilize photon beam motion for several ID beamlines. However, this feedback scheme is not transparent to FOFB, and suspected to be the source of occasional saturation of fast corrector strength. As an alternative solution, the local bump program and its feedback version has been recently upgraded to include bumps with X-ray BPMs and in operation since April 2019. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB104  
About • paper received ※ 19 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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THPRB107 A Novel Design of a Laser Phase Monitor for AWA RF Photocathode Electron Gun laser, LLRF, electron, controls 4076
 
  • W. Liu, M.E. Conde, D.S. Doran, G. Ha, J.G. Power, J.H. Shao, C. Whiteford, E.E. Wisniewski
    ANL, Argonne, Illinois, USA
  
  It is critical to maintain a stable laser phase for RF photocathode electron gun to achieve high beam stability. In order to achieve a higher beam stability for AWA(Argonne Wakefield Accelerator) beamline, a novel laser phase monitor has been designed to allow us to monitor and feedback on. Both the design and its applications at AWA are presented in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB107  
About • paper received ※ 13 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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THPRB112 Commission of the Transverse Bunch-by-Bunch Feedback at SPEAR3 kicker, injection, vacuum, GUI 4081
 
  • K. Tian, W.J. Corbett, X. Huang, N. Kurita, D.J. Martin, J.A. Safranek, J.J. Sebek
    SLAC, Menlo Park, California, USA
  • D. Teytelman
    Dimtel, San Jose, USA
  
  Funding: Work supported by US Department of Energy Contract DE-AC03-76SF00515.
Driven by the demand of suppressing transverse beam instabilities and developing novel short pulse operation modes in SPEAR3 storage ring, a wide-band transverse bunch-by-bunch feedback system has been recently commissioned for SPEAR3 storage ring. The system was demonstrated to be sufficient to suppress the transverse coupled bunch instabilities caused by trapped RF modes in one of the in vacuum insertion devices. A new function of beam instability interlock has been developed and is part of machine protection system for the in vacuum insertion device. In addition, the bunch-by-bunch feedback system serves as a indispensable diagnostic tool that enables us to measure machine parameters, beam impedance, and characteristics of the beam instability modes. In this paper, we describe the scheme and performance of the bunch-by-bunch feedback system at SPEAR3. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB112  
About • paper received ※ 14 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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