IPAC2016 - Classification: 06 Beam Instrumentation, Controls, Feedback and Operational Aspects / T05 Beam Feedback Systems

Paper	Title	Page
WEPOR001	Beam Studies with a New Longitudinal Feedback System at the ANKA Storage Ring	2658
	E. Blomley, A.-S. Müller, M. Schedler KIT, Karlsruhe, Germany
	With the now fully commissioned longitudinal feedback system at the ANKA Storage Ring - in addition to the already operational transverse feedback system - the stability throughout the injection process was increased considerably. This opened up the possibility to investigate beam dynamics and limitations during injection more systematically. This paper presents the results of these studies, an overview of the limiting parameters and discusses possible approaches to increase the efficiency of the injection.
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WEPOR002	Orbit Stabilization for the HLS-II Storage Ring	2661
	W. Xu, J.Y. Li, K. Xuan, H.Y. Zhang USTC/NSRL, Hefei, Anhui, People's Republic of China
	Hefei Light Source has successfully completed a major upgrade project, which greatly improves the light source performance. As one of the most important criteria, the stability of the beam orbit in the storage ring can greatly influence the overall performance of the light source. In this paper we present our efforts on stabilizing the beam orbit during the commissioning of the HLS-II storage ring. We optimized the performance of the power supplies of the ring corrector magnets. The target beam orbit is obtained by measuring the center of the quadrupole magnets using the beam-based alignment method. We also developed a multi-functional orbit feedback system to keep the beam moving on the golden orbit. With these measures, the beam orbit gets more stable than ten percent of the beam size at the light source points.
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WEPOR003	Voltage Control for the 4-Th Harmonic Cavity in Hls Storage Ring	2664
	K. Xuan, C. Li, J.Y. Li, G. Liu, W. Xu USTC/NSRL, Hefei, Anhui, People's Republic of China
	In order to increase the beam lifetime, a 4th harmonic RF cavity was installed in the HLS-II storage ring. The electrical fields in the principle cavity and high harmonic cavity stretch the beam in the longitudinal direction, and increase the beam volume in phase space, leading to a longer Touschek lifetime. Stable electrical voltage in the high harmonic cavity is essential for steady beam stretching and better beam lifetime. To get a stable high voltage in the high harmonic cavity, we develop a method to maintain steady resonance condition in the cavity using a PID scheme. This paper presents the details of this method. The feedback result is also reported.
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WEPOR004	Fast Orbit Feedback System at the Pls-Ii Storage Ring	2667
	S.-C. Kim, W.S. Cho, C. Kim, J.M. Kim, K.R. Kim, E.H. Lee, J. Lee, J.W. Lee, T.-Y. Lee, C.D. Park, G.S. Park, S. Shin, J.C. Yoon PAL, Pohang, Kyungbuk, Republic of Korea
	Funding: This work is supported by the Ministry of science, ICT and Future Planning, Korea. The transverse position of the electron beam in the Pohang Light Source-II (PLS-II) is stabilized by the global orbit feedback system. Currently, 2 Hz slow orbit feedback (SOFB) system is operating, and 1 kHz fast orbit feedback (FOFB) system is installed recently. This FOFB system is consists of 96 electron beam position monitors (BPMs), 48 horizontal fast correctors, 48 vertical fast correctors and VME control system. We present the design and implementation of the FOFB system and its test result. Analysis through the simulation is presented and future improvement is discussed
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WEPOR005	Ground Motion Compensation using Feed-forward Control at ATF2	2670
	D.R. Bett, C. Charrondière, M. Patecki, J. Pfingstner, D. Schulte, R. Tomás CERN, Geneva, Switzerland A. Jeremie IN2P3-LAPP, Annecy-le-Vieux, France K. Kubo, S. Kuroda, T. Naito, T. Okugi, T. Tauchi, N. Terunuma KEK, Ibaraki, Japan
	Ground motion compensation using feed-forward control is a novel technique being developed to combat beam imperfections resulting from the vibration-induced misalignment of beamline components. The method is being evaluated experimentally at the KEK Accelerator Test Facility 2 (ATF2). It has already been demonstrated that the beam position correlates with the readings from a set of seismometers located along the beamline. To compensate for this contribution to the beam jitter, the fully operational system will use realtime measurement and processing in order to calculate and apply the feed-forward correction on a useful time scale. The progress towards a working system is presented in this paper.
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WEPOR006	Demonstration of CLIC Level Phase Stability using a High Bandwidth, Low Latency Drive Beam Phase Feedforward System at the CLIC Test Facility CTF3	2673
	J. Roberts, P. Burrows, G.B. Christian, C. Perry JAI, Oxford, United Kingdom A. Andersson, R. Corsini, P.K. Skowroński CERN, Geneva, Switzerland A. Ghigo, F. Marcellini INFN/LNF, Frascati (Roma), Italy
	Funding: Work supported by the European Commission under the FP7 Research Infrastructures project Eu-CARD, grant agreement no.~227579. The CLIC acceleration scheme, in which the RF power used to accelerate the main high energy beam is extracted from a second high intensity but low energy beam, places strict requirements on the phase stability of the power producing drive beam. To limit luminosity loss caused by energy jitter leading to emittance growth in the final focus to below 1%, 0.2 degrees of 12 GHz, or 50 fs, drive beam phase stability is needed. A low-latency phase feedforward correction with bandwidth above 17.5 MHz will be used to reduce the drive beam phase jitter to this level. The proposed scheme corrects the phase using fast electromagnetic kickers to vary the path length in a chicane prior to the drive beam power extraction. A prototype of this system has been installed at the CLIC test facility CTF3 to prove its feasibility. The latest results from the system are presented, demonstrating phase stabilisation in agreement with simulations given the beam conditions and power of the kicker amplifiers. Necessary improvements in the phase monitor performance and optics corrections made to remove the phase-energy dependence via R56 in order to achieve this level of stability are also discussed.
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WEPOR007	Recent Improvements in Drive Beam Stability in CTF3	2677
	L. Malina, R. Corsini, D. Gamba, T. Persson, P.K. Skowroński CERN, Geneva, Switzerland
	The proposed Compact Linear Collider (CLIC) uses a high intensity, low energy drive beam producing the RF power to accelerate the low intensity main beam with 100 MeV/m gradient. This scheme puts stringent requirements on drive beam stability in terms of phase, energy and current. Finding and understanding the sources of jitter plays a key role in their mitigation. In this paper, we report on the recent studies in the CLIC Test Facility (CTF3). New jitter and drift sources were identified and adequate beam-based feed-backs were implemented and commissioned. Finally, we present the resulting improvement of drive beam stability.
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WEPOR008	Development of a High Resolution Beam Position Monitor for NSRRC VUV/THz FEL	2680
	P.J. Kung, K.C. Leou NTHU, Hsinchu, Taiwan W.K. Lau, A.P. Lee NSRRC, Hsinchu, Taiwan
	Beam position monitors (BPM) have been widely used on linear colliders and free electron lasers for beam-based alignment and feedback systems. A laser driven photo-injector system has been constructed in NSRRC. This injector has the capability to deliver short relativistic electron beam at high peak current for novel light source R&D. A 2.4 GHz BPM that can be used for high precision beam position measurement has been designed. The BPM were modified to separate frequency between the horizontal and vertical dipole signals, as well as a reduction of the monopole signal. The design has been simulated by CST. A prototype has been built for verification of theoretical predictions. Microwave bench measurement has been made to compare with the computer simulation results. The progress of our work will be presented in this paper.
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WEPOR009	Intra-beam IP Feedback Studies for the 380 GeV CLIC Beam Delivery System	2683
	R.M. Bodenstein, P. Burrows, J. Snuverink JAI, Oxford, United Kingdom F. Plassard CERN, Geneva, Switzerland
	In its currently-envisaged initial stage, the Compact Linear Collider (CLIC) will collide beams with a 380 GeV center of mass energy. To maintain the luminosity within a few percent of the design value, beam stability at the interaction point (IP) must be controlled at the sub-nanometer level. To help achieve such control, use of an intra-pulse IP feedback system is planned. With CLIC's very short bunch spacing of 0.5 ns, and nominal pulse duration of 176 ns, this feedback system presents a significant technical challenge. Furthermore, as part of a study to optimize the design of the beam delivery system (BDS), several L* configurations have been studied. In this paper, we will review the IP feedback simulations for the 380 GeV machine for two L* configurations, and compare luminosity recovery performance with that of the original L* configuration in the 3 TeV machine.
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WEPOR010	Recent Upgrades to the CERN SPS Wideband Intra-bunch Transverse Feedback Processor	2687
	J.E. Dusatko, J.D. Fox, C.H. Rivetta SLAC, Menlo Park, California, USA W. Höfle CERN, Geneva, Switzerland O. Turgut Stanford University, Stanford, California, USA
	In support of the CERN High Luminosity LHC (HL-LHC) upgrade program, a research and development effort has been underway to understand and develop feedback control techniques for mitigating transverse intra-bunch instabilities in the SPS driven by electron cloud and TMCI effects. These effects could be a limiting factor to overall machine performance. A result of this effort has been the development of a very wide band transverse feedback demonstration system. This system has been used for the last several years in machine development studies where we have demonstrated single-bunch stability control of low order intra-bunch modes. In continuation of these efforts, recent upgrades have been performed in all stages of the system, including the feedback processor itself. This paper discusses the upgrades specific to it, including the ability to process multiple proton bunches in the SPS; and also highlights future directions in the development effort.
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WEPOR060	MTCA.4-based Beam Line Stabilization Application	2808
	K.P. Przygoda TUL-DMCS, Łódź, Poland C. Gerth, H. Schlarb, B. Steffen DESY, Hamburg, Germany
	We want to summarize the beam line stabilization application with MTCA.4 electronics. Presented solution is based on the compact 2U MTCA.4 crate integrating sensor and actuator cards. The optical beam position sensor is based on quadrupole SI PIN photodiode connected to low cost AMC based FMC carrier equipped with ADC card. The optical beam position correction is done using picomotorized stages equipped with active piezo elements and high voltage RTM piezo driver. The data processing and digital feedback units are implemented using Spartan 6 FPGA. The control algorithm has been optimized for low latency and high precision computations. The control electronics performance has been tested using single beam line test stand consisted of commercial laser diode drivers, supported optics and motorized stages. The first results are demonstrated and future possible applications are briefly discussed.
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WEPOW040	Preliminary Beam Test for TPS Fast Orbit Feedback System	2930
	P.C. Chiu, K.T. Hsu, K.H. Hu, C.H. Huang, C.Y. Liao NSRRC, Hsinchu, Taiwan
	TPS (Taiwan Photon Source) is a 3 GeV synchrotron light source which had be successfully commissioning with SRF up to 500 Amp in 2015 and scheduled to open user operation in 2016. As most of the 3rd generation light source, the fast orbit feedback system would be adopted to eliminate various disturbances and improve orbit stability. Due to the vacuum chamber material made of aluminum with higher conductivity and lower bandwidth, extra fast correctors mounted on bellows will be used for FOFB correction loop and DC correction of fast correctors would be transferred to slow ones and avoid fast corrector saturation. This report summarizes the infrastructure of the FOFB and the preliminary beam test is also presented.
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WEPOW052	Multimodal Interaction in the ALS Longitudinal Feedback Kicker RF Cavity	2965
	S. De Santis, K.M. Baptiste, J.M. Byrd, S. Kwiatkowski, T.H. Luo, E.R. Sanmateo, C. Steier, C.A. Swenson LBNL, Berkeley, California, USA F. Marcellini PSI, Villigen PSI, Switzerland
	Funding: The Advanced Light Source is supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. RF cavities are essential components in particle accelerators not only for beam acceleration, but also for control purposes (bunch lengthening/shortening, deflecting and crabbing, transverse and longitudinal kickers) and for beam diagnostics (BPM). Normally, only a single resonating mode is actively used, although other modes can be excited by the circulating beam. Cavities used as feedback longitudinal kickers are designed with an axial mode which, appropriately excited, provides a kick to the circulating bunches for maintaining beam stability. To provide the necessary bandwidth this mode has to be strongly damped resulting in quality factors of just a few units. In the longitudinal feedback kicker cavity just installed on the ALS we have detected a second axial mode which, although a few hundreds of MHz below the 1.4 GHz design mode, is also strongly damped and has a shunt impedance high enough to be appreciably excited by the feedback amplifier coupling to the first mode. In this paper we show bench measurements on the cavity and with beam during its commissioning and discuss the interaction of the two modes resulting in a modulation of shunt impedance and phase response.
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THOAA01	Identification of Intra-bunch Transverse Dynamics for Model-Based Control Purposes at CERN Super Proton Synchrotron	3145
SUPSS077	use link to see paper's listing under its alternate paper code
	O. Turgut, J.E. Dusatko, J.D. Fox, C.H. Rivetta SLAC, Menlo Park, California, USA S.M. Rock Stanford University, Stanford, California, USA
	Funding: Work supported by the U.S. Department of Energy under contract DE-AC02-76SF00515 and the US LHC Accelerator Research program (LARP). Research supported by FP7 HiLumi LHC http://hilumilhc.web.cern.ch The high luminosity upgrade plan for the LHC (HiLumi-LHC) increases the bunch intensity and the ultimate intensities require mitigation of possible intra-bunch instabilities in the SPS. Feedback systems can stabilize intra-bunch dynamics. Model based control has promise to stabilize intra-bunch dynamics but it requires a reduced order model which captures the most significant intra-bunch dynamics. We present methods for the estimation of a multi-input multi-output (MIMO) reduced order model of intra-bunch dynamics based on data generated by nonlinear macro particle simulations (CMAD, HeadTail). These linear models are used to design optimal model-based controllers. We evaluate the effectiveness of the MIMO model-based controllers for future high intensity beam conditions within the nonlinear macro particle simulations. We highlight the use of these techniques to stabilize intra-bunch motion and as an important beam dynamics measurement technique.
	Slides THOAA01 [10.146 MB]
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Paper

Title

Page

Beam Studies with a New Longitudinal Feedback System at the ANKA Storage Ring

2658

E. Blomley, A.-S. Müller, M. Schedler
KIT, Karlsruhe, Germany

With the now fully commissioned longitudinal feedback system at the ANKA Storage Ring - in addition to the already operational transverse feedback system - the stability throughout the injection process was increased considerably. This opened up the possibility to investigate beam dynamics and limitations during injection more systematically. This paper presents the results of these studies, an overview of the limiting parameters and discusses possible approaches to increase the efficiency of the injection.

Export •

reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPOR002

Orbit Stabilization for the HLS-II Storage Ring

2661

W. Xu, J.Y. Li, K. Xuan, H.Y. Zhang
USTC/NSRL, Hefei, Anhui, People's Republic of China

Hefei Light Source has successfully completed a major upgrade project, which greatly improves the light source performance. As one of the most important criteria, the stability of the beam orbit in the storage ring can greatly influence the overall performance of the light source. In this paper we present our efforts on stabilizing the beam orbit during the commissioning of the HLS-II storage ring. We optimized the performance of the power supplies of the ring corrector magnets. The target beam orbit is obtained by measuring the center of the quadrupole magnets using the beam-based alignment method. We also developed a multi-functional orbit feedback system to keep the beam moving on the golden orbit. With these measures, the beam orbit gets more stable than ten percent of the beam size at the light source points.

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WEPOR003

Voltage Control for the 4-Th Harmonic Cavity in Hls Storage Ring

2664

K. Xuan, C. Li, J.Y. Li, G. Liu, W. Xu
USTC/NSRL, Hefei, Anhui, People's Republic of China

In order to increase the beam lifetime, a 4th harmonic RF cavity was installed in the HLS-II storage ring. The electrical fields in the principle cavity and high harmonic cavity stretch the beam in the longitudinal direction, and increase the beam volume in phase space, leading to a longer Touschek lifetime. Stable electrical voltage in the high harmonic cavity is essential for steady beam stretching and better beam lifetime. To get a stable high voltage in the high harmonic cavity, we develop a method to maintain steady resonance condition in the cavity using a PID scheme. This paper presents the details of this method. The feedback result is also reported.

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WEPOR004

Fast Orbit Feedback System at the Pls-Ii Storage Ring

2667

S.-C. Kim, W.S. Cho, C. Kim, J.M. Kim, K.R. Kim, E.H. Lee, J. Lee, J.W. Lee, T.-Y. Lee, C.D. Park, G.S. Park, S. Shin, J.C. Yoon
PAL, Pohang, Kyungbuk, Republic of Korea

Funding: This work is supported by the Ministry of science, ICT and Future Planning, Korea.
The transverse position of the electron beam in the Pohang Light Source-II (PLS-II) is stabilized by the global orbit feedback system. Currently, 2 Hz slow orbit feedback (SOFB) system is operating, and 1 kHz fast orbit feedback (FOFB) system is installed recently. This FOFB system is consists of 96 electron beam position monitors (BPMs), 48 horizontal fast correctors, 48 vertical fast correctors and VME control system. We present the design and implementation of the FOFB system and its test result. Analysis through the simulation is presented and future improvement is discussed

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WEPOR005

Ground Motion Compensation using Feed-forward Control at ATF2

2670

D.R. Bett, C. Charrondière, M. Patecki, J. Pfingstner, D. Schulte, R. Tomás
CERN, Geneva, Switzerland
A. Jeremie
IN2P3-LAPP, Annecy-le-Vieux, France
K. Kubo, S. Kuroda, T. Naito, T. Okugi, T. Tauchi, N. Terunuma
KEK, Ibaraki, Japan

Ground motion compensation using feed-forward control is a novel technique being developed to combat beam imperfections resulting from the vibration-induced misalignment of beamline components. The method is being evaluated experimentally at the KEK Accelerator Test Facility 2 (ATF2). It has already been demonstrated that the beam position correlates with the readings from a set of seismometers located along the beamline. To compensate for this contribution to the beam jitter, the fully operational system will use realtime measurement and processing in order to calculate and apply the feed-forward correction on a useful time scale. The progress towards a working system is presented in this paper.

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WEPOR006

Demonstration of CLIC Level Phase Stability using a High Bandwidth, Low Latency Drive Beam Phase Feedforward System at the CLIC Test Facility CTF3

2673

J. Roberts, P. Burrows, G.B. Christian, C. Perry
JAI, Oxford, United Kingdom
A. Andersson, R. Corsini, P.K. Skowroński
CERN, Geneva, Switzerland
A. Ghigo, F. Marcellini
INFN/LNF, Frascati (Roma), Italy

Funding: Work supported by the European Commission under the FP7 Research Infrastructures project Eu-CARD, grant agreement no.~227579.
The CLIC acceleration scheme, in which the RF power used to accelerate the main high energy beam is extracted from a second high intensity but low energy beam, places strict requirements on the phase stability of the power producing drive beam. To limit luminosity loss caused by energy jitter leading to emittance growth in the final focus to below 1%, 0.2 degrees of 12 GHz, or 50 fs, drive beam phase stability is needed. A low-latency phase feedforward correction with bandwidth above 17.5 MHz will be used to reduce the drive beam phase jitter to this level. The proposed scheme corrects the phase using fast electromagnetic kickers to vary the path length in a chicane prior to the drive beam power extraction. A prototype of this system has been installed at the CLIC test facility CTF3 to prove its feasibility. The latest results from the system are presented, demonstrating phase stabilisation in agreement with simulations given the beam conditions and power of the kicker amplifiers. Necessary improvements in the phase monitor performance and optics corrections made to remove the phase-energy dependence via R56 in order to achieve this level of stability are also discussed.

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WEPOR007

Recent Improvements in Drive Beam Stability in CTF3

2677

L. Malina, R. Corsini, D. Gamba, T. Persson, P.K. Skowroński
CERN, Geneva, Switzerland

The proposed Compact Linear Collider (CLIC) uses a high intensity, low energy drive beam producing the RF power to accelerate the low intensity main beam with 100 MeV/m gradient. This scheme puts stringent requirements on drive beam stability in terms of phase, energy and current. Finding and understanding the sources of jitter plays a key role in their mitigation. In this paper, we report on the recent studies in the CLIC Test Facility (CTF3). New jitter and drift sources were identified and adequate beam-based feed-backs were implemented and commissioned. Finally, we present the resulting improvement of drive beam stability.

Export •

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WEPOR008

Development of a High Resolution Beam Position Monitor for NSRRC VUV/THz FEL

2680

P.J. Kung, K.C. Leou
NTHU, Hsinchu, Taiwan
W.K. Lau, A.P. Lee
NSRRC, Hsinchu, Taiwan

Beam position monitors (BPM) have been widely used on linear colliders and free electron lasers for beam-based alignment and feedback systems. A laser driven photo-injector system has been constructed in NSRRC. This injector has the capability to deliver short relativistic electron beam at high peak current for novel light source R&D. A 2.4 GHz BPM that can be used for high precision beam position measurement has been designed. The BPM were modified to separate frequency between the horizontal and vertical dipole signals, as well as a reduction of the monopole signal. The design has been simulated by CST. A prototype has been built for verification of theoretical predictions. Microwave bench measurement has been made to compare with the computer simulation results. The progress of our work will be presented in this paper.

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WEPOR009

Intra-beam IP Feedback Studies for the 380 GeV CLIC Beam Delivery System

2683

R.M. Bodenstein, P. Burrows, J. Snuverink
JAI, Oxford, United Kingdom
F. Plassard
CERN, Geneva, Switzerland

In its currently-envisaged initial stage, the Compact Linear Collider (CLIC) will collide beams with a 380 GeV center of mass energy. To maintain the luminosity within a few percent of the design value, beam stability at the interaction point (IP) must be controlled at the sub-nanometer level. To help achieve such control, use of an intra-pulse IP feedback system is planned. With CLIC's very short bunch spacing of 0.5 ns, and nominal pulse duration of 176 ns, this feedback system presents a significant technical challenge. Furthermore, as part of a study to optimize the design of the beam delivery system (BDS), several L* configurations have been studied. In this paper, we will review the IP feedback simulations for the 380 GeV machine for two L* configurations, and compare luminosity recovery performance with that of the original L* configuration in the 3 TeV machine.

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WEPOR010

Recent Upgrades to the CERN SPS Wideband Intra-bunch Transverse Feedback Processor

2687

J.E. Dusatko, J.D. Fox, C.H. Rivetta
SLAC, Menlo Park, California, USA
W. Höfle
CERN, Geneva, Switzerland
O. Turgut
Stanford University, Stanford, California, USA

In support of the CERN High Luminosity LHC (HL-LHC) upgrade program, a research and development effort has been underway to understand and develop feedback control techniques for mitigating transverse intra-bunch instabilities in the SPS driven by electron cloud and TMCI effects. These effects could be a limiting factor to overall machine performance. A result of this effort has been the development of a very wide band transverse feedback demonstration system. This system has been used for the last several years in machine development studies where we have demonstrated single-bunch stability control of low order intra-bunch modes. In continuation of these efforts, recent upgrades have been performed in all stages of the system, including the feedback processor itself. This paper discusses the upgrades specific to it, including the ability to process multiple proton bunches in the SPS; and also highlights future directions in the development effort.

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WEPOR060

MTCA.4-based Beam Line Stabilization Application

2808

K.P. Przygoda
TUL-DMCS, Łódź, Poland
C. Gerth, H. Schlarb, B. Steffen
DESY, Hamburg, Germany

We want to summarize the beam line stabilization application with MTCA.4 electronics. Presented solution is based on the compact 2U MTCA.4 crate integrating sensor and actuator cards. The optical beam position sensor is based on quadrupole SI PIN photodiode connected to low cost AMC based FMC carrier equipped with ADC card. The optical beam position correction is done using picomotorized stages equipped with active piezo elements and high voltage RTM piezo driver. The data processing and digital feedback units are implemented using Spartan 6 FPGA. The control algorithm has been optimized for low latency and high precision computations. The control electronics performance has been tested using single beam line test stand consisted of commercial laser diode drivers, supported optics and motorized stages. The first results are demonstrated and future possible applications are briefly discussed.

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WEPOW040

Preliminary Beam Test for TPS Fast Orbit Feedback System

2930

P.C. Chiu, K.T. Hsu, K.H. Hu, C.H. Huang, C.Y. Liao
NSRRC, Hsinchu, Taiwan

TPS (Taiwan Photon Source) is a 3 GeV synchrotron light source which had be successfully commissioning with SRF up to 500 Amp in 2015 and scheduled to open user operation in 2016. As most of the 3rd generation light source, the fast orbit feedback system would be adopted to eliminate various disturbances and improve orbit stability. Due to the vacuum chamber material made of aluminum with higher conductivity and lower bandwidth, extra fast correctors mounted on bellows will be used for FOFB correction loop and DC correction of fast correctors would be transferred to slow ones and avoid fast corrector saturation. This report summarizes the infrastructure of the FOFB and the preliminary beam test is also presented.

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WEPOW052

Multimodal Interaction in the ALS Longitudinal Feedback Kicker RF Cavity

2965

S. De Santis, K.M. Baptiste, J.M. Byrd, S. Kwiatkowski, T.H. Luo, E.R. Sanmateo, C. Steier, C.A. Swenson
LBNL, Berkeley, California, USA
F. Marcellini
PSI, Villigen PSI, Switzerland

Funding: The Advanced Light Source is supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
RF cavities are essential components in particle accelerators not only for beam acceleration, but also for control purposes (bunch lengthening/shortening, deflecting and crabbing, transverse and longitudinal kickers) and for beam diagnostics (BPM). Normally, only a single resonating mode is actively used, although other modes can be excited by the circulating beam. Cavities used as feedback longitudinal kickers are designed with an axial mode which, appropriately excited, provides a kick to the circulating bunches for maintaining beam stability. To provide the necessary bandwidth this mode has to be strongly damped resulting in quality factors of just a few units. In the longitudinal feedback kicker cavity just installed on the ALS we have detected a second axial mode which, although a few hundreds of MHz below the 1.4 GHz design mode, is also strongly damped and has a shunt impedance high enough to be appreciably excited by the feedback amplifier coupling to the first mode. In this paper we show bench measurements on the cavity and with beam during its commissioning and discuss the interaction of the two modes resulting in a modulation of shunt impedance and phase response.

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THOAA01

Identification of Intra-bunch Transverse Dynamics for Model-Based Control Purposes at CERN Super Proton Synchrotron

3145

SUPSS077

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

O. Turgut, J.E. Dusatko, J.D. Fox, C.H. Rivetta
SLAC, Menlo Park, California, USA
S.M. Rock
Stanford University, Stanford, California, USA

Funding: Work supported by the U.S. Department of Energy under contract DE-AC02-76SF00515 and the US LHC Accelerator Research program (LARP). Research supported by FP7 HiLumi LHC http://hilumilhc.web.cern.ch
The high luminosity upgrade plan for the LHC (HiLumi-LHC) increases the bunch intensity and the ultimate intensities require mitigation of possible intra-bunch instabilities in the SPS. Feedback systems can stabilize intra-bunch dynamics. Model based control has promise to stabilize intra-bunch dynamics but it requires a reduced order model which captures the most significant intra-bunch dynamics. We present methods for the estimation of a multi-input multi-output (MIMO) reduced order model of intra-bunch dynamics based on data generated by nonlinear macro particle simulations (CMAD, HeadTail). These linear models are used to design optimal model-based controllers. We evaluate the effectiveness of the MIMO model-based controllers for future high intensity beam conditions within the nonlinear macro particle simulations. We highlight the use of these techniques to stabilize intra-bunch motion and as an important beam dynamics measurement technique.

Slides THOAA01 [10.146 MB]

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