IPAC2019 - Classification: MC6: Beam Instrumentation, Controls, Feedback and Operational Aspects / T27 Low Level RF

Paper	Title	Page
THYPLS1	RF Controls Towards Femtosecond and Attosecond Precision	3414
	F. Ludwig, J. Branlard, Ł. Butkowski, M.K. Czwalinna, M. Hierholzer, M. Hoffmann, M. Killenberg, T. Lamb, J. Marjanovic, U. Mavrič, J.M. Müller, S. Pfeiffer, H. Schlarb, Ch. Schmidt, L. Springer DESY, Hamburg, Germany M. Kuntzsch, K. Zenker HZDR, Dresden, Germany
	In the past two decades, RF controls have improved by two orders in magnitude achieving meanwhile sub-10 fs phase stabilities and 10^-4 amplitude precision. Advances are through improved field detection methods and massive usage of digital signal procession on very powerful field programmable gate arrays (FPGAs). The question rise, what can be achieved in the next 10 years? In this talk, a review is given of existing systems and strategies, current stability limitations of RF control system and new technologies with the potential to achieve attosecond resolutions.
	Slides THYPLS1 [10.328 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THYPLS1
About •	paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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THYYPLS1	On-Demand Beam Route and RF Parameter Switching System for Time-Sharing of a Linac for X-ray Free-Electron Laser as an Injector to a 4th-Generation Synchrotron Radiation Source	3427
	H. Maesaka, T. Fukui, T. Hara, T. Inagaki, H. Tanaka RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan T. Hasegawa, O. Morimoto, Y. Tajiri, S. Tanaka, M. Yoshioka SES, Hyogo-pref., Japan N. Hosoda, S. Matsubara, T. Ohshima JASRI/SPring-8, Hyogo-ken, Japan C. Kondo, K. Okada, M. Yamaga JASRI, Hyogo, Japan
	We have an upgrade plan of the SPring-8 storage ring to provide much more brilliant X-rays with a low-emittance electron beam. Since the upgraded ring requires a low-emittance injection beam, we are planning to timeshare the linac of the X-ray free electron laser (XFEL) facility, SACLA, as an injector for the upgraded ring. The SACLA linac delivers low-emittance and short-bunch electron beams to two XFEL beamlines with a 60 Hz repetition rate. The beam route is right now equally changed by a kicker magnet at a switchyard. The beam parameter is also optimized for each XFEL beamline by changing RF parameters pulse-by-pulse with simple software at this moment. Since the number of beam injection shots to the storage ring is much less frequent than XFEL shots, one of the XFEL shots must be overridden by an injection with on-demand basis. In addition, the beam quality, such as 1 mm mrad normalized emittance, 10 fs bunch length and 10 kA peak current, must be maintained not to deteriorate the XFEL performance. Therefore, we have developed an on-demand beam route and RF parameter switching system with sufficient speed, precision and reliability. A beam route data is transmitted to each accelerator unit by a reflective memory network, and special software changes the parameters of each accelerator unit pulse-by-pulse according to the received data. We tested the on-demand switching system at a test bench and the SACLA linac. The beam parameters were appropriately controlled with a negligible failure rate. The user service of the beam injection from SACLA to SPring-8 is scheduled in 2020 and the on-demand switching system is almost ready for the time-sharing operation of multiple XFEL beamlines and a SPring-8 injection. T. Hara et al., Phys. Rev. Accel. Beams 21, 040701 (2018).
	Slides THYYPLS1 [8.519 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THYYPLS1
About •	paper received ※ 16 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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THPRB007	Ponderomotive Instability of Self-Excited Cavity	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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THPRB008	Ponderomotive Instability of Two Self-Excited Cavities	3812
	S.R. Koscielniak TRIUMF, Vancouver, Canada
	We consider the ponderomotive instability of two superconducting RF cavities self-driven from a single RF source with vector-sum control.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB008
About •	paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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THPRB009	Vector Sum & Diffference Control of SRF Cavities	3816
	S.R. Koscielniak TRIUMF, Vancouver, Canada
	We consider the ponderomotive instability of multiple superconducting RF cavities driven from a single RF source. We add vector difference control to the usual the technique of vector sum control, in order to increase the accelerating gradient threshold for ponderomotive instability.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB009
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	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	3824
SUSPFO005	use link to see paper's listing under its alternate paper code
	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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THPRB021	Automatic Loop for Carrier Suppression in Attosecond RF Receivers	3847
	U. Mavrič, M. Hoffmann, F. Ludwig, H. Schlarb, L. Springer DESY, Hamburg, Germany
	The carrier suppression interferometer method can be used as a radio receiver architecture which allows for detection of RF signals in the attosecond range. The carrier suppression scheme requires an automatic carrier suppression circuit which provides stable operation of the RF receiver in the best operating point. In the poster we investigate the requirements for such an algorithm, evaluate the achievable closed loop bandwidth and the side effects on the overall-performance. In addition we apply the carrier tracking to simplify and automate the characterization of various electronic phase shifters and attenuators in the as-range
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB021
About •	paper received ※ 13 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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THPRB022	Sensitivity Analysis of Feedforward Beam Current Compensation for Improved Beam Loading Robustness	3850
	D. Mihailescu Stoica, D. Domont-Yankulova RMR, TU Darmstadt, Darmstadt, Germany D. Domont-Yankulova, H. Klingbeil TEMF, TU Darmstadt, Darmstadt, Germany H. Klingbeil, D.E.M. Lens GSI, Darmstadt, Germany
	The planned SIS100 heavy ion synchrotron at the Facility for Antiproton and Ion Research (FAIR) in Darmstadt, Germany will possess twenty ferrite accelerating cavities in its final stage of extension. During the intended acceleration cycles, the cavities will encounter significant beam loading effects, which have to be handled by the control systems. As both the generator- and beam-current act on the same system input, a feedforward disturbance compensation can be a promising approach to improve beam qualities and suppress instabilities induced by the beam current. Particle tracking simulations, incorporating twenty ferrite cavities and their attached LLRF control systems, are performed to analyse the sensitivity of the beam quality with respect to errors in the feedforward beam current compensation. The main focus lies on the time after injection from a pre-accelerator, where most cavities in the SIS100 do not provide any gap voltage and thus are particularly sensitive to induced voltages by beam currents if the cavities are not or only partly short-circuited.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB022
About •	paper received ※ 10 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019
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THPRB024	Piezo Controls For The European XFEL	3856
	K.P. Przygoda, J. Branlard, Ł. Butkowski, M.K. Grecki, M. Hierholzer, M. Omet, H. Schlarb DESY, Hamburg, Germany
	The European X-Ray Free Electron Laser (E-XFEL) accelerator is a pulse machine. The typical time duration of a radio frequency (RF) pulse is about 1.3 ms. The RF power transmitted to the superconducting RF (SCRF) cavity as a set of successive pulses (10 Hz repetition rate), causes strong mechanical stresses inside the cavity. The mechanical deformations of the RF cavity are typically caused by the Lorentz force detuning (LFD). The cavity can be tuned to a 1.3 GHz resonance frequency during the RF pulse using fast piezo tuners. Since the E-XFEL will use around 800 cavities (each cavity with double piezos), a distributed architecture with multi-channel digital and analog control circuits seems to be essential. The most sought-after issue is high-voltage, high-current piezo driving circuit dedicated to multi-channel configuration. The driving electronics should allow a maximum piezo protection against any kind of failure. The careful automation of the piezo tuners control and its demonstration for the high gradient conditions a real challenge. The first demonstration of piezo controls applied for chosen RF stations of the E-XFEL linear accelerator (linac) are presented and obtained results are briefly discussed within this paper.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB024
About •	paper received ※ 30 April 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019
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THPRB025	New MicroTCA Piezo Driver (PZT4)	3860
	K.P. Przygoda, Ł. Butkowski, M. Fenner, M. Hierholzer, R. Rybaniec, H. Schlarb, Ch. Schmidt DESY, Hamburg, Germany R. Rybaniec PSI, Villigen PSI, Switzerland
	In the paper we would like to present a new Micro Telecommunication Computing Architecture (MicroTCA) piezo driver (PZT4). The piezo driver module is capable of driving of 4 piezo actuators with high voltages up to 160 Vpp. It is also possible to measure cavity mechanical vibrations using 4 analog to digital converters (ADC) ported to the driver electronics. The new piezo driver can be supplied using internal 12 V payload power provided by the MicroTCA standard. For the applications that need more than 30 W of the input power, the external power supply module can be provided. In order to protect the piezo driver electronics against output short condition a dedicated supervision circuit is designed. The piezo driver module has been setup at Cryo Module Test Bench (CMTB) facility in Deutsches-Elektronen Synchrotron (DESY) as a part of the single cavity low-level radio frequency (LLRF) controls. The LLRF control system has been used to demonstrate the radio frequency (RF) field stabilization and cavity tuning capabilities for continuous (CW) and pulse modes of operation of 1.3 GHz superconducting resonant RF (SCRF) cavity. The preliminary results are demonstrated and briefly discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB025
About •	paper received ※ 08 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019
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THPRB044	LLRF Control System for RF GUN at SXFEL Test Facility	3912
	L. Li, Q. Gu, Y.J. Liu, C.C. Xiao, J.Q. Zhang SINAP, Shanghai, People’s Republic of China Y.F. Liu, Z. Wang SARI-CAS, Pudong, Shanghai, People’s Republic of China
	A Soft X-ray Free Electron Laser Test Facility (SXFEL-TF) based on normal conducting linear accelerator was constructed at the Shanghai Synchrotron Radiation Facility (SSRF) campus by a joint team of Shanghai Institute of Applied Physics and Tsinghua University. It consists of multiple Radio Frequency (RF) stations with standing wave cavity (RF Gun) and traveling wave accelerating structures working at different frequencies. Low Level Radio Frequency (LLRF) system is used to measure the RF field in the cavities or structures and correct the fluctuation in RF fields with pulse-to-pulse feedback controllers. This paper describes the hardware and architecture of the LLRF system for electromagnetic filed stabilization inside the radio frequency electron gun, in the SXFEL-TF. A complete control path has be presented, including RF front-end board, I/Q detector and feedback controller. Algorithms used to stabilize the RF field have been presented as well as the software environment used to provide remote access to the control device. Finally, the performance of the LLRF system that was realized in the beam commissioning is presented and meets the high accuracy requirements.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB044
About •	paper received ※ 23 April 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019
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THPRB049	MODELING AND SIMULATION FOR MULTI-FEEDING CAVITY WITHOUT BEAM LOADING	3921
	K. Liu, Q. Gu, L. Li, Ch. Wang, M.H. Zhao SINAP, Shanghai, People’s Republic of China Q. Gu SSRF, Shanghai, People’s Republic of China
	The Multi-feeding cavity usually be applied in super-conducting and normal-conducting RF cavity. The differences between multiple input couplers in coupler coefficient, incident power and phase will cause the cavity field stabilities can not meet the requirements. For explore the influences of these differences and develop equations for measurement, a multi-feeding LCR transient model was developed. As two-feeding cavity, the VHF photocathode electron gun was model and simulated in this paper.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB049
About •	paper received ※ 06 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019
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THPRB050	LLRF System Modelling and Controller Design in UED	3924
	Y.Q. Li, K. Fan, Y. Song HUST, Wuhan, People’s Republic of China
	In the Ultrafast Electron Diffraction (UED) facility for investigating material structure, drifts of amplitude and phase in cavity have different effects on beam quality. So it is critical for pump-probe experiments in the UED to keep accurate synchronization between the laser and electron. To achieve the desired 50fs resolution, the Low Level Radio Frequency (LLRF) controller in S-band normal conducting cavity needs to satisfy the stability: ±0.01% (rms) for the amplitude and ±0.01° (rms) for the phase, respectively. Then we can study the performance of the RF control system by simulating the LLRF system. In the simulation program, feedback, feed-forward algorithms, and beam current variations can be simulated in a Matlab/Simulink environment. This paper shows that a model-based controller design can meet the necessary requirements of the field regulation and implement the algorithms.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB050
About •	paper received ※ 20 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019
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THPRB063	Field Control Challenges for Different LINAC Types	3946
SUSPFO095	use link to see paper's listing under its alternate paper code
	O. Troeng, A.J. Johansson Lund University, Lund, Sweden M. Eshraqi ESS, Lund, Sweden S. Pfeiffer DESY, Hamburg, Germany
	Linacs for free-electron lasers typically require cavity field stabilities of 0.01\% and 0.01 degree, while the requirements for high-intensity proton linacs are on the order of 0.1–1\% and 0.1–1 degrees. From these numbers it is easy to believe that the field control problem for proton linacs is many times easier than for free-electron lasers linacs. In this contribution we explain why this is not necessarily the case, and discuss the factors that make field control challenging. We also discuss the drivers for field stability, and how high-level decisions on the linac design affect the difficulty of the field control problem.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB063
About •	paper received ※ 15 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019
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THPRB066	Beam Based Measurements of Relative RF Phase	3950
	S.C.P. Albright CERN, Geneva, Switzerland M.D. Kuczynski LPCT, Vandoeuvre-lès-Nancy Cedex, France
	The ferrite loaded RF cavities of the CERN Proton Synchrotron Booster will be replaced with FinemetTM loaded cavities during Long Shutdown 2 2019-2020). To fully realise the potential of the new cavities, the relative RF phases must be aligned along the acceleration ramp, where the revolution frequency changes by nearly a factor of 2. A beam based method of measuring the relative phase between the cavities is desired to give the best possible compensation for the frequency dependent phase shift. In this paper we present an operationally viable method to measure the phase shift as a function of RF frequency. The relative phase of the RF cavities can be aligned to within a few degrees, giving an error on the voltage seen by the beam of less than 1%.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB066
About •	paper received ※ 08 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019
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THPRB067	Time Varying RF Phase Noise for Longitudinal Emittance Blow-Up	3954
	S.C.P. Albright CERN, Geneva, Switzerland D. Quartullo Sapienza University of Rome, Rome, Italy
	RF phase noise was shown to be effective for controlled longitudinal emittance blow-up in the Proton Synchrotron Booster (PSB) at CERN during beam tests in 2017, with further developments in 2018. At CERN, RF phase noise is used operationally in the Super Proton Synchrotron (SPS) and Large Hadron Collider (LHC). In this paper we show that it is suitable for operation with a variety of beam types in the PSB. In the PSB the synchrotron frequency changes by approximately a factor 4 during the 500 ms acceleration ramp, requiring large changes in the frequency band of the noise. During 2018, a new method of calculating the noise parameters has been demonstrated, which gives upper and lower bounds to the noise frequency band that are smoothly varying through the ramp. The new calculation method has been applied to operational beams accelerated in both single and double RF harmonics, the final results are presented here.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB067
About •	paper received ※ 29 April 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019
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THPRB068	Upgrade of CERN’s PSB Digital Low-Level RF System	3958
	M.E. Angoletta, S.C.P. Albright, A. Findlay, M. Jaussi, J.C. Molendijk, N. Pittet CERN, Geneva, Switzerland
	The CERN PS Booster (PSB) is the first circular accelerator in the LHC proton injector chain. The upgrade of this four-ring machine is underway within the framework of the LHC Injectors Upgrade project. The existing digital Low-Level RF (LLRF) system will also be upgraded. This paper outlines the LLRF capabilities required, their implementation and the challenges involved. Results of tests carried out to prepare for the LLRF upgrade are given.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB068
About •	paper received ※ 13 May 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019
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THPRB069	The New Digital Low-Level RF System for CERN’s Extra Low Energy Antiproton Machine	3962
	M.E. Angoletta, M. Jaussi, J.C. Molendijk CERN, Geneva, Switzerland
	CERN’s new Extra Low ENergy Antiproton accelerator/decelerator (ELENA) completed its initial commissioning in 2018. This machine is equipped with a new digital Low-Level RF (LLRF) system that implements beam and cavity loops as well as longitudinal diagnostics. ELENA’s LLRF was instrumental for machine commissioning by decelerating some 1 E7 antiprotons from 5.3 MeV to 100 keV. Commissioning with H⁻ ions took also place. Challenges faced included coping with low beam intensity and the wide frequency swing. This paper gives an overview of the LLRF system capabilities and operation. Beam results achieved with both H⁻ ions and antiprotons are also shown.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB069
About •	paper received ※ 13 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019
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THPRB070	A New Digital Low-Level RF and Longitudinal Diagnostic System for CERN’s AD	3966
	M.E. Angoletta, S.C.P. Albright, A. Findlay, M. Jaussi, J.C. Molendijk, V.R. Myklebust CERN, Geneva, Switzerland
	The Antiproton Decelerator (AD) has been routinely providing 3 E7 antiprotons since July 2000 at 100 MeV/c from 3.5 GeV/c. It will be refurbished during the Long Shutdown 2 (LS2) to provide reliable operation for the new Extra Low ENergy Antiproton (ELENA) ring. AD will be equipped with a new digital Low-Level RF (LLRF) system before its restart in 2021. Diagnostics to measure beam intensity, Δp/p and Schottky spectra will also be developed. This paper is an overview of the planned capabilities and implementations, as well as of the challenges to overcome.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB070
About •	paper received ※ 13 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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THPRB082	The CERN SPS Low Level RF upgrade Project	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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THPRB094	Study of the System Stability for the Digital Low Level RF System Operated at High Beam Currents	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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THPRB097	Analysis of RF System Stability on CLARA	4053
	N.Y. Joshi, J.K. Jones, A.J. Moss, E.W. Snedden, A.E. Wheelhouse STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom A.C. Dexter, J. Henderson Cockcroft Institute, Lancaster University, Lancaster, United Kingdom J.K. Jones Cockcroft Institute, Warrington, Cheshire, United Kingdom
	The Compact Linear Accelerator for Research and Applications (CLARA) facility at STFC Daresbury Laboratory will test underpinning concepts and technology for a next generation X-ray free electron laser (FEL). CLARA will use four S-band normal conducting traveling wave linacs to accelerate electron bunches to a maximum energy of 250 MeV. The amplitude and phase stability of the collected RF systems is critical in enabling CLARA to achieve low (10 fs) shot-to-shot timing jitter of the photon output. Here we present initial measurements and model of the amplitude and phase jitter of the CLARA RF systems, achieved by experimentally correlating the klystron output with controls from modulator, driver, and other environment parameters. The effect of the RF jitter on the CLARA beam momentum is also integrated in the model.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB097
About •	paper received ※ 10 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019
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THPTS022	The Realization of Iterative Learning Control for J-PARC LINAC LLRF Control System	4155
	S. Li J-PARC, KEK & JAEA, Ibaraki-ken, Japan Z. Fang, Y. Fukui, K. Futatsukawa, F. Qiu KEK, Ibaraki, Japan Y. Sato, S. Shinozaki JAEA/J-PARC, Tokai-mura, Japan
	The beam current of j-parc linac was planned to increase to 60 mA. The stronger beam current will lead to higher beam loading effect. Due to the low Q factor of cavity in high β section of linac, the traditional PID feedback & feedforward control method may have to face huge challenges. In order to make the system run better at 60 mA, the iterative learning control (ILC) method was put forward to use in LLRF control system. All the ILC operations are done in EPICS-PC. By installing the PyEpics module, we can use python programs to realize the data interaction between EPICS system and PC and further realize the ILC algorithm. In this paper, the architecture of ILC methods will be introduced. The performance of ILC method will be reported.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS022
About •	paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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THPTS060	Sirius Digital LLRF	4244
	A. Salom, F. Pérez ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain R.H.A. Farias, F.K.G. Hoshino, A.P.B. Lima LNLS, Campinas, Brazil
	Sirius is a Synchrotron Light Source Facility based on a 4th generation low emittance storage ring. The facility is presently under construction in Campinas, Brazil, and comprises a 3 GeV electron storage ring, a full energy booster synchrotron and a 120 MeV linac. The booster RF system is based on a single 5-cell cavity driven by a 50 kW amplifier at 500MHz and is designed to operate at 2 Hz rate. The storage ring RF system will start with 1 normal conducting 7-cell cavity. In the final configuration, the system will comprise 2 superconducting cavities, each one driven by a 240 kW RF amplifier. A digital LLRF system based on ALBA LLRF has been designed and commissioned to control 3 different types of cavities: 2 normal conducting single cell cavities, one multi-cell cavity driven by 2 amplifiers and one superconducting cavity driven by 4 amplifiers. The first LLRF System was installed and commissioned in the Sirius Booster in 2019. The performance of the control loops with beam, together with other utilities of the system like automatic start-up, conditioning, fast interlocks and post-mortem analysis will be presented in this paper, as well as possible upgrades for the future
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS060
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THPTS075	Performance Tests of a Digital Low-Level Rf-System at the TPS	4292
	F.Y. Chang, L.-H. 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
	A digital low-level RF (DLLRF) control system for the cavity gap voltage is now common throughout the world. At the Taiwan Photon Source (TPS) we installed and operated a DLLRF in the booster ring in 2018 successfully and plan to install it also in the storage ring in 2019. Operational and beam loading tests of the DLLRF at the storage ring are ongoing. The performance of the DLLRF in the presence of a large number of 60 Hz harmonics and its stability for gap voltage and phase will be discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS075
About •	paper received ※ 10 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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Paper

Title

Page

RF Controls Towards Femtosecond and Attosecond Precision

3414

F. Ludwig, J. Branlard, Ł. Butkowski, M.K. Czwalinna, M. Hierholzer, M. Hoffmann, M. Killenberg, T. Lamb, J. Marjanovic, U. Mavrič, J.M. Müller, S. Pfeiffer, H. Schlarb, Ch. Schmidt, L. Springer
DESY, Hamburg, Germany
M. Kuntzsch, K. Zenker
HZDR, Dresden, Germany

In the past two decades, RF controls have improved by two orders in magnitude achieving meanwhile sub-10 fs phase stabilities and 10^-4 amplitude precision. Advances are through improved field detection methods and massive usage of digital signal procession on very powerful field programmable gate arrays (FPGAs). The question rise, what can be achieved in the next 10 years? In this talk, a review is given of existing systems and strategies, current stability limitations of RF control system and new technologies with the potential to achieve attosecond resolutions.

Slides THYPLS1 [10.328 MB]

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THYYPLS1

On-Demand Beam Route and RF Parameter Switching System for Time-Sharing of a Linac for X-ray Free-Electron Laser as an Injector to a 4th-Generation Synchrotron Radiation Source

3427

H. Maesaka, T. Fukui, T. Hara, T. Inagaki, H. Tanaka
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
T. Hasegawa, O. Morimoto, Y. Tajiri, S. Tanaka, M. Yoshioka
SES, Hyogo-pref., Japan
N. Hosoda, S. Matsubara, T. Ohshima
JASRI/SPring-8, Hyogo-ken, Japan
C. Kondo, K. Okada, M. Yamaga
JASRI, Hyogo, Japan

We have an upgrade plan of the SPring-8 storage ring to provide much more brilliant X-rays with a low-emittance electron beam. Since the upgraded ring requires a low-emittance injection beam, we are planning to timeshare the linac of the X-ray free electron laser (XFEL) facility, SACLA, as an injector for the upgraded ring. The SACLA linac delivers low-emittance and short-bunch electron beams to two XFEL beamlines with a 60 Hz repetition rate. The beam route is right now equally changed by a kicker magnet at a switchyard. The beam parameter is also optimized for each XFEL beamline by changing RF parameters pulse-by-pulse with simple software at this moment*. Since the number of beam injection shots to the storage ring is much less frequent than XFEL shots, one of the XFEL shots must be overridden by an injection with on-demand basis. In addition, the beam quality, such as 1 mm mrad normalized emittance, 10 fs bunch length and 10 kA peak current, must be maintained not to deteriorate the XFEL performance. Therefore, we have developed an on-demand beam route and RF parameter switching system with sufficient speed, precision and reliability. A beam route data is transmitted to each accelerator unit by a reflective memory network, and special software changes the parameters of each accelerator unit pulse-by-pulse according to the received data. We tested the on-demand switching system at a test bench and the SACLA linac. The beam parameters were appropriately controlled with a negligible failure rate. The user service of the beam injection from SACLA to SPring-8 is scheduled in 2020 and the on-demand switching system is almost ready for the time-sharing operation of multiple XFEL beamlines and a SPring-8 injection.
* T. Hara et al., Phys. Rev. Accel. Beams 21, 040701 (2018).

Slides THYYPLS1 [8.519 MB]

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paper received ※ 16 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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THPRB007

Ponderomotive Instability of Self-Excited Cavity

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.

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paper received ※ 14 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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THPRB008

Ponderomotive Instability of Two Self-Excited Cavities

3812

S.R. Koscielniak
TRIUMF, Vancouver, Canada

We consider the ponderomotive instability of two superconducting RF cavities self-driven from a single RF source with vector-sum control.

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paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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THPRB009

Vector Sum & Diffference Control of SRF Cavities

3816

S.R. Koscielniak
TRIUMF, Vancouver, Canada

We consider the ponderomotive instability of multiple superconducting RF cavities driven from a single RF source. We add vector difference control to the usual the technique of vector sum control, in order to increase the accelerating gradient threshold for ponderomotive instability.

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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

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.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB010

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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

3824

SUSPFO005

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

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.

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paper received ※ 14 May 2019 paper accepted ※ 19 May 2019 issue date ※ 21 June 2019

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THPRB021

Automatic Loop for Carrier Suppression in Attosecond RF Receivers

3847

U. Mavrič, M. Hoffmann, F. Ludwig, H. Schlarb, L. Springer
DESY, Hamburg, Germany

The carrier suppression interferometer method can be used as a radio receiver architecture which allows for detection of RF signals in the attosecond range. The carrier suppression scheme requires an automatic carrier suppression circuit which provides stable operation of the RF receiver in the best operating point. In the poster we investigate the requirements for such an algorithm, evaluate the achievable closed loop bandwidth and the side effects on the overall-performance. In addition we apply the carrier tracking to simplify and automate the characterization of various electronic phase shifters and attenuators in the as-range

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paper received ※ 13 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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THPRB022

Sensitivity Analysis of Feedforward Beam Current Compensation for Improved Beam Loading Robustness

3850

D. Mihailescu Stoica, D. Domont-Yankulova
RMR, TU Darmstadt, Darmstadt, Germany
D. Domont-Yankulova, H. Klingbeil
TEMF, TU Darmstadt, Darmstadt, Germany
H. Klingbeil, D.E.M. Lens
GSI, Darmstadt, Germany

The planned SIS100 heavy ion synchrotron at the Facility for Antiproton and Ion Research (FAIR) in Darmstadt, Germany will possess twenty ferrite accelerating cavities in its final stage of extension. During the intended acceleration cycles, the cavities will encounter significant beam loading effects, which have to be handled by the control systems. As both the generator- and beam-current act on the same system input, a feedforward disturbance compensation can be a promising approach to improve beam qualities and suppress instabilities induced by the beam current. Particle tracking simulations, incorporating twenty ferrite cavities and their attached LLRF control systems, are performed to analyse the sensitivity of the beam quality with respect to errors in the feedforward beam current compensation. The main focus lies on the time after injection from a pre-accelerator, where most cavities in the SIS100 do not provide any gap voltage and thus are particularly sensitive to induced voltages by beam currents if the cavities are not or only partly short-circuited.

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paper received ※ 10 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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THPRB024

Piezo Controls For The European XFEL

3856

K.P. Przygoda, J. Branlard, Ł. Butkowski, M.K. Grecki, M. Hierholzer, M. Omet, H. Schlarb
DESY, Hamburg, Germany

The European X-Ray Free Electron Laser (E-XFEL) accelerator is a pulse machine. The typical time duration of a radio frequency (RF) pulse is about 1.3 ms. The RF power transmitted to the superconducting RF (SCRF) cavity as a set of successive pulses (10 Hz repetition rate), causes strong mechanical stresses inside the cavity. The mechanical deformations of the RF cavity are typically caused by the Lorentz force detuning (LFD). The cavity can be tuned to a 1.3 GHz resonance frequency during the RF pulse using fast piezo tuners. Since the E-XFEL will use around 800 cavities (each cavity with double piezos), a distributed architecture with multi-channel digital and analog control circuits seems to be essential. The most sought-after issue is high-voltage, high-current piezo driving circuit dedicated to multi-channel configuration. The driving electronics should allow a maximum piezo protection against any kind of failure. The careful automation of the piezo tuners control and its demonstration for the high gradient conditions a real challenge. The first demonstration of piezo controls applied for chosen RF stations of the E-XFEL linear accelerator (linac) are presented and obtained results are briefly discussed within this paper.

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paper received ※ 30 April 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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THPRB025

New MicroTCA Piezo Driver (PZT4)

3860

K.P. Przygoda, Ł. Butkowski, M. Fenner, M. Hierholzer, R. Rybaniec, H. Schlarb, Ch. Schmidt
DESY, Hamburg, Germany
R. Rybaniec
PSI, Villigen PSI, Switzerland

In the paper we would like to present a new Micro Telecommunication Computing Architecture (MicroTCA) piezo driver (PZT4). The piezo driver module is capable of driving of 4 piezo actuators with high voltages up to 160 Vpp. It is also possible to measure cavity mechanical vibrations using 4 analog to digital converters (ADC) ported to the driver electronics. The new piezo driver can be supplied using internal 12 V payload power provided by the MicroTCA standard. For the applications that need more than 30 W of the input power, the external power supply module can be provided. In order to protect the piezo driver electronics against output short condition a dedicated supervision circuit is designed. The piezo driver module has been setup at Cryo Module Test Bench (CMTB) facility in Deutsches-Elektronen Synchrotron (DESY) as a part of the single cavity low-level radio frequency (LLRF) controls. The LLRF control system has been used to demonstrate the radio frequency (RF) field stabilization and cavity tuning capabilities for continuous (CW) and pulse modes of operation of 1.3 GHz superconducting resonant RF (SCRF) cavity. The preliminary results are demonstrated and briefly discussed.

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paper received ※ 08 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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THPRB044

LLRF Control System for RF GUN at SXFEL Test Facility

3912

L. Li, Q. Gu, Y.J. Liu, C.C. Xiao, J.Q. Zhang
SINAP, Shanghai, People’s Republic of China
Y.F. Liu, Z. Wang
SARI-CAS, Pudong, Shanghai, People’s Republic of China

A Soft X-ray Free Electron Laser Test Facility (SXFEL-TF) based on normal conducting linear accelerator was constructed at the Shanghai Synchrotron Radiation Facility (SSRF) campus by a joint team of Shanghai Institute of Applied Physics and Tsinghua University. It consists of multiple Radio Frequency (RF) stations with standing wave cavity (RF Gun) and traveling wave accelerating structures working at different frequencies. Low Level Radio Frequency (LLRF) system is used to measure the RF field in the cavities or structures and correct the fluctuation in RF fields with pulse-to-pulse feedback controllers. This paper describes the hardware and architecture of the LLRF system for electromagnetic filed stabilization inside the radio frequency electron gun, in the SXFEL-TF. A complete control path has be presented, including RF front-end board, I/Q detector and feedback controller. Algorithms used to stabilize the RF field have been presented as well as the software environment used to provide remote access to the control device. Finally, the performance of the LLRF system that was realized in the beam commissioning is presented and meets the high accuracy requirements.

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paper received ※ 23 April 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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THPRB049

MODELING AND SIMULATION FOR MULTI-FEEDING CAVITY WITHOUT BEAM LOADING

3921

K. Liu, Q. Gu, L. Li, Ch. Wang, M.H. Zhao
SINAP, Shanghai, People’s Republic of China
Q. Gu
SSRF, Shanghai, People’s Republic of China

The Multi-feeding cavity usually be applied in super-conducting and normal-conducting RF cavity. The differences between multiple input couplers in coupler coefficient, incident power and phase will cause the cavity field stabilities can not meet the requirements. For explore the influences of these differences and develop equations for measurement, a multi-feeding LCR transient model was developed. As two-feeding cavity, the VHF photocathode electron gun was model and simulated in this paper.

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paper received ※ 06 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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THPRB050

LLRF System Modelling and Controller Design in UED

3924

Y.Q. Li, K. Fan, Y. Song
HUST, Wuhan, People’s Republic of China

In the Ultrafast Electron Diffraction (UED) facility for investigating material structure, drifts of amplitude and phase in cavity have different effects on beam quality. So it is critical for pump-probe experiments in the UED to keep accurate synchronization between the laser and electron. To achieve the desired 50fs resolution, the Low Level Radio Frequency (LLRF) controller in S-band normal conducting cavity needs to satisfy the stability: ±0.01% (rms) for the amplitude and ±0.01° (rms) for the phase, respectively. Then we can study the performance of the RF control system by simulating the LLRF system. In the simulation program, feedback, feed-forward algorithms, and beam current variations can be simulated in a Matlab/Simulink environment. This paper shows that a model-based controller design can meet the necessary requirements of the field regulation and implement the algorithms.

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paper received ※ 20 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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THPRB063

Field Control Challenges for Different LINAC Types

3946

SUSPFO095

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

O. Troeng, A.J. Johansson
Lund University, Lund, Sweden
M. Eshraqi
ESS, Lund, Sweden
S. Pfeiffer
DESY, Hamburg, Germany

Linacs for free-electron lasers typically require cavity field stabilities of 0.01\% and 0.01 degree, while the requirements for high-intensity proton linacs are on the order of 0.1–1\% and 0.1–1 degrees. From these numbers it is easy to believe that the field control problem for proton linacs is many times easier than for free-electron lasers linacs. In this contribution we explain why this is not necessarily the case, and discuss the factors that make field control challenging. We also discuss the drivers for field stability, and how high-level decisions on the linac design affect the difficulty of the field control problem.

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paper received ※ 15 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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THPRB066

Beam Based Measurements of Relative RF Phase

3950

S.C.P. Albright
CERN, Geneva, Switzerland
M.D. Kuczynski
LPCT, Vandoeuvre-lès-Nancy Cedex, France

The ferrite loaded RF cavities of the CERN Proton Synchrotron Booster will be replaced with FinemetTM loaded cavities during Long Shutdown 2 2019-2020). To fully realise the potential of the new cavities, the relative RF phases must be aligned along the acceleration ramp, where the revolution frequency changes by nearly a factor of 2. A beam based method of measuring the relative phase between the cavities is desired to give the best possible compensation for the frequency dependent phase shift. In this paper we present an operationally viable method to measure the phase shift as a function of RF frequency. The relative phase of the RF cavities can be aligned to within a few degrees, giving an error on the voltage seen by the beam of less than 1%.

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paper received ※ 08 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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THPRB067

Time Varying RF Phase Noise for Longitudinal Emittance Blow-Up

3954

S.C.P. Albright
CERN, Geneva, Switzerland
D. Quartullo
Sapienza University of Rome, Rome, Italy

RF phase noise was shown to be effective for controlled longitudinal emittance blow-up in the Proton Synchrotron Booster (PSB) at CERN during beam tests in 2017, with further developments in 2018. At CERN, RF phase noise is used operationally in the Super Proton Synchrotron (SPS) and Large Hadron Collider (LHC). In this paper we show that it is suitable for operation with a variety of beam types in the PSB. In the PSB the synchrotron frequency changes by approximately a factor 4 during the 500 ms acceleration ramp, requiring large changes in the frequency band of the noise. During 2018, a new method of calculating the noise parameters has been demonstrated, which gives upper and lower bounds to the noise frequency band that are smoothly varying through the ramp. The new calculation method has been applied to operational beams accelerated in both single and double RF harmonics, the final results are presented here.

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paper received ※ 29 April 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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THPRB068

Upgrade of CERN’s PSB Digital Low-Level RF System

3958

M.E. Angoletta, S.C.P. Albright, A. Findlay, M. Jaussi, J.C. Molendijk, N. Pittet
CERN, Geneva, Switzerland

The CERN PS Booster (PSB) is the first circular accelerator in the LHC proton injector chain. The upgrade of this four-ring machine is underway within the framework of the LHC Injectors Upgrade project. The existing digital Low-Level RF (LLRF) system will also be upgraded. This paper outlines the LLRF capabilities required, their implementation and the challenges involved. Results of tests carried out to prepare for the LLRF upgrade are given.

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paper received ※ 13 May 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019

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THPRB069

The New Digital Low-Level RF System for CERN’s Extra Low Energy Antiproton Machine

3962

M.E. Angoletta, M. Jaussi, J.C. Molendijk
CERN, Geneva, Switzerland

CERN’s new Extra Low ENergy Antiproton accelerator/decelerator (ELENA) completed its initial commissioning in 2018. This machine is equipped with a new digital Low-Level RF (LLRF) system that implements beam and cavity loops as well as longitudinal diagnostics. ELENA’s LLRF was instrumental for machine commissioning by decelerating some 1 E7 antiprotons from 5.3 MeV to 100 keV. Commissioning with H⁻ ions took also place. Challenges faced included coping with low beam intensity and the wide frequency swing. This paper gives an overview of the LLRF system capabilities and operation. Beam results achieved with both H⁻ ions and antiprotons are also shown.

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paper received ※ 13 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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THPRB070

A New Digital Low-Level RF and Longitudinal Diagnostic System for CERN’s AD

3966

M.E. Angoletta, S.C.P. Albright, A. Findlay, M. Jaussi, J.C. Molendijk, V.R. Myklebust
CERN, Geneva, Switzerland

The Antiproton Decelerator (AD) has been routinely providing 3 E7 antiprotons since July 2000 at 100 MeV/c from 3.5 GeV/c. It will be refurbished during the Long Shutdown 2 (LS2) to provide reliable operation for the new Extra Low ENergy Antiproton (ELENA) ring. AD will be equipped with a new digital Low-Level RF (LLRF) system before its restart in 2021. Diagnostics to measure beam intensity, Δp/p and Schottky spectra will also be developed. This paper is an overview of the planned capabilities and implementations, as well as of the challenges to overcome.

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paper received ※ 13 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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THPRB082

The CERN SPS Low Level RF upgrade Project

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

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paper received ※ 13 May 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

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.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB094

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paper received ※ 07 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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THPRB097

Analysis of RF System Stability on CLARA

4053

N.Y. Joshi, J.K. Jones, A.J. Moss, E.W. Snedden, A.E. Wheelhouse
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
A.C. Dexter, J. Henderson
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
J.K. Jones
Cockcroft Institute, Warrington, Cheshire, United Kingdom

The Compact Linear Accelerator for Research and Applications (CLARA) facility at STFC Daresbury Laboratory will test underpinning concepts and technology for a next generation X-ray free electron laser (FEL). CLARA will use four S-band normal conducting traveling wave linacs to accelerate electron bunches to a maximum energy of 250 MeV. The amplitude and phase stability of the collected RF systems is critical in enabling CLARA to achieve low (10 fs) shot-to-shot timing jitter of the photon output. Here we present initial measurements and model of the amplitude and phase jitter of the CLARA RF systems, achieved by experimentally correlating the klystron output with controls from modulator, driver, and other environment parameters. The effect of the RF jitter on the CLARA beam momentum is also integrated in the model.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPRB097

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paper received ※ 10 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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THPTS022

The Realization of Iterative Learning Control for J-PARC LINAC LLRF Control System

4155

S. Li
J-PARC, KEK & JAEA, Ibaraki-ken, Japan
Z. Fang, Y. Fukui, K. Futatsukawa, F. Qiu
KEK, Ibaraki, Japan
Y. Sato, S. Shinozaki
JAEA/J-PARC, Tokai-mura, Japan

The beam current of j-parc linac was planned to increase to 60 mA. The stronger beam current will lead to higher beam loading effect. Due to the low Q factor of cavity in high β section of linac, the traditional PID feedback & feedforward control method may have to face huge challenges. In order to make the system run better at 60 mA, the iterative learning control (ILC) method was put forward to use in LLRF control system. All the ILC operations are done in EPICS-PC. By installing the PyEpics module, we can use python programs to realize the data interaction between EPICS system and PC and further realize the ILC algorithm. In this paper, the architecture of ILC methods will be introduced. The performance of ILC method will be reported.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS022

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paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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THPTS060

Sirius Digital LLRF

4244

A. Salom, F. Pérez
ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain
R.H.A. Farias, F.K.G. Hoshino, A.P.B. Lima
LNLS, Campinas, Brazil

Sirius is a Synchrotron Light Source Facility based on a 4th generation low emittance storage ring. The facility is presently under construction in Campinas, Brazil, and comprises a 3 GeV electron storage ring, a full energy booster synchrotron and a 120 MeV linac. The booster RF system is based on a single 5-cell cavity driven by a 50 kW amplifier at 500MHz and is designed to operate at 2 Hz rate. The storage ring RF system will start with 1 normal conducting 7-cell cavity. In the final configuration, the system will comprise 2 superconducting cavities, each one driven by a 240 kW RF amplifier. A digital LLRF system based on ALBA LLRF has been designed and commissioned to control 3 different types of cavities: 2 normal conducting single cell cavities, one multi-cell cavity driven by 2 amplifiers and one superconducting cavity driven by 4 amplifiers. The first LLRF System was installed and commissioned in the Sirius Booster in 2019. The performance of the control loops with beam, together with other utilities of the system like automatic start-up, conditioning, fast interlocks and post-mortem analysis will be presented in this paper, as well as possible upgrades for the future

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS060

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paper received ※ 15 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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THPTS075

Performance Tests of a Digital Low-Level Rf-System at the TPS

4292

F.Y. Chang, L.-H. 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

A digital low-level RF (DLLRF) control system for the cavity gap voltage is now common throughout the world. At the Taiwan Photon Source (TPS) we installed and operated a DLLRF in the booster ring in 2018 successfully and plan to install it also in the storage ring in 2019. Operational and beam loading tests of the DLLRF at the storage ring are ongoing. The performance of the DLLRF in the presence of a large number of 60 Hz harmonics and its stability for gap voltage and phase will be discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS075

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paper received ※ 10 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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