NAPAC2016 - List of Keywords (feedback)

Paper	Title	Other Keywords	Page
MOA2IO02	The BNL EBPM Electronics, High Performance for Next Generation Storage Rings	ion, storage-ring, operation, experiment	1
	K. Vetter ORNL, Oak Ridge, Tennessee, USA W.X. Cheng, J. Mead, B. Podobedov, Y. Tian BNL, Upton, Long Island, New York, USA
	Funding: DOE contract DE-AC02-98CH10886 A custom state-of-the-art RF BPM (EBPM) has been developed and commissioned at the Brookhaven National Laboratory (BNL) National Synchrotron Light Source II (NSLS-II). A collaboration between Lawrence Berkeley National Laboratory (LBNL) Advanced Light Source (ALS) and BNL has proven to be a key element in the success of the NSLS-II EBPM. High stability coherent signal processing has allowed for demonstrated 200nm RMS spatial resolution and true turn-by-turn position measurement capability. Sub-micron 24 hr. stability has been demonstrated at NSLS-II by use of 0.01C RMS thermal regulation of the electronics racks without the need of active pilot tone correction.
	Slides MOA2IO02 [4.334 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-MOA2IO02
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MOA2CO03	Measurement of Tune Shift with Amplitude from BPM Data with a Single Kicker Pulse	ion, kicker, lattice, experiment	6
	Y. Hidaka, W.X. Cheng, B. Podobedov BNL, Upton, Long Island, New York, USA
	Funding: The study is supported by U.S. DOE under Contract No. DE-AC02-98CH10886. Measurements of amplitude-dependent tune shift are critical for understanding of nonlinear single particle dynamics in storage rings. The conventional method involves scanning of the kicker amplitude while having a short bunch train at the top of the kicker pulse. In this paper we present a novel, alternative technique that uses a long continuous bunch train, or a sequence of bunch trains, that are spread along the ring, such that different bunches experience different kick amplitudes with a single shot of a kicker pulse. With these beams, a curve of tune shift with amplitude can be extracted from the recently added new NSLS-II BPM feature called gated turn-by-turn (TbT) BPM data that can resolve bunches within a turn, either alone or together with a bunch-by-bunch BPM data. This technique is immune to pulse-to-pulse jitters and long-term machine drift.
	Slides MOA2CO03 [1.961 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-MOA2CO03
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TUPOA17	A Longitudinal Digital Mode Damper System for the Fermilab Booster	ion, booster, cavity, damping	320
	N. Eddy, W. Pellico, A. Semenov, D.C. Voy, A.M. Waller Fermilab, Batavia, Illinois, USA
	Funding: This work was supported by the U.S. Department of Energy under contract No. DE-AC02-07CH11359. The Fermilab Booster accelerates bunches and accelerates proton beams from 400 MeV to 8 GeV. During the acceleration the Radio Frequency (RF) cavities are swept from 38MHz to 52.8MHz and requires crossing through transition where accelerating phase is shifted 90 degrees. In order to keep the beam stable and minimize losses and emittance growth a longitudinal damping system is required. This has traditionally been done by dedicated analog electronics designed to operate on specific beam modes for frequencies of instabilities. A complete digital implementation has been developed for this same purpose. The new digital system features and performance are detailed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-TUPOA17
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TUPOA41	FPGA Control of Coherent Pulse Stacking	ion, cavity, controls, FPGA	367
	Y.L. Xu, J.M. Byrd, L.R. Doolittle, Q. Du, G. Huang, W. Leemans, R.B. Wilcox, Y. Yang LBNL, Berkeley, California, USA J. Dawson LLNL, Livermore, California, USA A. Galvanauskas, J.M. Ruppe University of Michigan, Ann Arbor, Michigan, USA
	Coherent pulse stacking (CPS) is a new time-domain coherent addition technique that stacks several optical pulses into a single output pulse, enabling high pulse energy from fiber lasers. Due to advantages of precise timing and fast processing, we use an FPGA to process digital signals and do feedback control so as to realize stacking-cavity stabilization. We develop a hardware and firmware design platform to support the coherent pulse stacking application. A firmware bias control module stabilizes the amplitude modulator at the minimum of its transfer function. A cavity control module ensures that each optical cavity is kept at a certain individually-prescribed and stable round-trip phase with 2.5 deg rms phase error.
	Poster TUPOA41 [5.546 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-TUPOA41
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TUPOA67	Helium Pressure Vessel Jacketing of the Fermilab SSR1 Single Spoke SC Cavities	ion, cavity, real-time, cryomodule	418
	E.C. Bonnema, E.K. Cunningham Meyer Tool & MFG, Oak Lawn, Illinois, USA
	Meyer Tool recently completed the welding of the liquid helium pressure vessel jackets around ten (10) superconducting single spoke niobium cavities for Fermilab. The SSR1 cavities are intended for use in the PIP-II Injector Experiment Cryomodule. Meyer Tool's scope of supply included review of the Fermilab Pressure Rating Analysis Document and the development of fabrication details and a fabrication sequence to meet that document's requirements, while minimizing the effects of jacketing cavity frequency, and the actual jacketing of the cavities. This paper will focus on the development of the fabrication details and sequence and how the details and sequence evolved over the course of welding and final machining of the ten (10) jackets. As the frequency of these cavities is critical the fabrication sequence accommodated numerous in process frequency checks, a frequency tuning step prior to the final weld, the use of thermal cameras to monitor weld heat input into the cavity, and post welding final machining of critical features. Lessons learned from this fabrication will be discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-TUPOA67
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TUPOA71	Beam Stability During Top Off Operation at NSLS-II Storage Ring	ion, injection, operation, storage-ring	425
	W.X. Cheng, B. Bacha, Y. Li, O. Singh, Y. Tian BNL, Upton, Long Island, New York, USA
	NSLS-II storage ring started top off operation since Oct 2015. User operation current has been gradually increased to 250mA. Observations of beam stabilities during top-off operations will be presented. Total beam current was typically maintained within ±0.5% and bunch to bunch current variation was less than 20%. Injection transition during top-off was measured bunch by bunch digitizer, and BPM to analyze the orbit motion at various bandwidths (turn by turn, 10kHz and 10Hz rate). Coupled bunch unstable motions were monitored. As the vacuum pressure improves, fast-ion instability is not as severe compared to early stage of commissioning/operation, but still observed as the dominant instability. Resistive wall instability is noticed as more in-vacuum-undulator (IVU) gaps closed. xBPM measured photon stability and electron beam stability at top off injection have been evaluated. Short term and long term orbit stabilities will be reported.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-TUPOA71
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TUPOB02	Development of the Method for Evaluation of a Super-Conducting Traveling Wave Cavity With a Feedback Waveguide	ion, cavity, GUI, simulation	480
	R.A. Kostin LETI, Saint-Petersburg, Russia P.V. Avrakhov, A. Kanareykin Euclid TechLabs, LLC, Solon, Ohio, USA N. Solyak, V.P. Yakovlev Fermilab, Batavia, Illinois, USA
	Funding: DOE SBIR # DE-SC0006300 Euclid Techlabs is developing a superconducting traveling wave (SCWT) cavity with a feedback waveguide [1] and has demonstrated a traveling wave at room temperature [2] in a 3-cell SCTW cavity [3]. A special method described in this paper was developed for cavity evaluation. It is based on an S-matrix approach. The cavity tuning procedure based on this method is described.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-TUPOB02
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TUPOB45	A Model to Simulate the Effect of a Transverse Feedback System on Single Bunch Instability Thresholds	ion, simulation, kicker, damping	596
	G. Bassi, A. Blednykh, V.V. Smaluk BNL, Upton, Long Island, New York, USA Z. Yang Auburn University, Auburn, USA
	Funding: DOE Contract No. DE-AC02-98CH10886 A model to simulate the effect of a transverse feedback system is implemented in SPACE, a parallel, self-consistent code for collective effects. As an application, we discuss single bunch instability thresholds in the NSLS-II storage ring and compare the numerical results with measurements.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-TUPOB45
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TUPOB55	Optimize the Algorithm for the Global Orbit Feedback at Fixed Energies and During Acceleration in RHIC	ion, acceleration, proton, lattice	612
	C. Liu, R.L. Hulsart, K. Mernick, R.J. Michnoff, M.G. Minty BNL, Upton, Long Island, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy. To combat triplets vibration, the global orbit feedback system with frequency about 10 Hz was developed and en- gaged in operation at injection and top energy in 2010, dur- ing beam acceleration in 2012 at RHIC. The system has performed well with keeping 6 out of 12 eigenvalues for the orbit response matrix. However, we observed correc- tor current transients with the lattice for polarized proton program in 2015 which resulted in corrector power supply trips. In this report, we will present the observation, an- alyze the cause and also optimize the feedback algorithm to overcome the newly emerged problem with the feedback system.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-TUPOB55
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WEA3CO04	Impedance Characterization and Collective Effects in the MAX IV 3 GeV Ring	ion, impedance, synchrotron, experiment	843
	G. Skripka, Å. Andersson, P.F. Tavares MAX IV Laboratory, Lund University, Lund, Sweden F.J. Cullinan, R. Nagaoka SOLEIL, Gif-sur-Yvette, France
	Collective instabilities in the MAX IV 3 GeV storage ring are enhanced by the combination of high beam current, ultralow emittance and small vacuum chamber aperture. To mitigate instabilities by Landau damping and improve lifetime three passive harmonic cavities are installed to introduce synchrotron tune spread and bunch lengthening respectively. We present the results of studies of collective effects driven by the machine impedance. Bunch lengthening and detuning were measured to characterize the effective impedance and estimate the effect of the harmonic cavity potential. Investigations of collective effects as a function of parameters such as beam current and chromaticity are discussed.
	Slides WEA3CO04 [3.845 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-WEA3CO04
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WEPOB04	Beamline-Controlled Steering of Source-Point Angle at the Advanced Photon Source	ion, EPICS, controls, operation	887
	L. Emery, G.I. Fystro, H. Shang, M.L. Smith ANL, Argonne, Illinois, USA
	Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357 An EPICS-based steering software system has been implemented for beamline personnel to directly steer the angle of the synchrotron radiation sources at the Advanced Photon Source. A script running on a workstation monitors "start steering" beamline EPICS records, and effects a steering by the value of "angle request" EPICS records that beamlines have set. The new system effectively bypasses floor coordinators and MCR operators, and makes the steering process much faster than before, although these older protocols can still be used. As with the original steering there are EPICS alarm limits that prevent large steering from occurring and avoid other problems. Error messages and statuses, OPI windows and alarm configurations are provided to the beamlines and the accelerator operators. Underpinning this new steering protocol is the recent refinement of the global orbit feedback process whereby feedforward of dipole corrector set points and orbit set points are used to create a local steering bump in a rapid and seamless way. In principle and in practice, many simultaneous steering commands from many beamlines are possible. We report on a complete 3-month run of experience.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-WEPOB04
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WEPOB08	Collective Effects at Injection for the APS-U MBA Lattice	ion, injection, collective-effects, lattice	901
	R.R. Lindberg, M. Borland ANL, Argonne, Illinois, USA A. Blednykh BNL, Upton, Long Island, New York, USA
	Funding: U.S. Dept. of Energy Office of Sciences under Contract No. DE-AC02-06CH11357 The Advanced Photon Source has proposed an upgrade to a multi-bend achromat (MBA) with a proposed timing mode calls for 48 bunches of 15 nC each. In this mode of operation we find that phase space mismatch from the booster can drive large wakefields that in turn may limit the current below that of the nominal collective instability threshold. We show that collective effects at injection lead to emittance growth that makes usual off-axis accumulation very challenging. On-axis injection ameliorates many of these issues, but we find that transverse feedback is still required. We explore the role of impedance, feedback, and phase-space mismatch on transverse instabilities at injection.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-WEPOB08
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THPOA30	SCHARGEV 1.0 - Strong Space Charge Vlasov Solver	ion, space-charge, impedance, dipole	1164
	T. Zolkin, A.V. Burov Fermilab, Batavia, Illinois, USA
	The space charge (SC) is known to be one of the major limitations for the collective transverse beam stability. When space charge is strong, i.e. SC tune shift much greater than synchrotron tune, the problem allows an exact analytical solution. For that practically important case we present a fast and effective Vlasov solver SCHARGEV (Space CHARGE Vlasov) which calculates a complete eigensystem (spatial shapes of modes and frequency spectra) and therefore provides the growth rates and the thresholds of instabilities. SCHARGEV 1.0 includes driving and detuning wake forces, and, any feedback system (damper). In the next version we will include coupled bunch interaction and Landau damping. Numerical examples for FermiLab Recycler and CERN SPS are presented.
	Poster THPOA30 [1.493 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-THPOA30
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FRA2IO02	High Precision RF Control for the LCLS-II	ion, cavity, controls, LLRF	1292
	G. Huang, K. Campbell, L.R. Doolittle, J.A. Jones, C. Serrano, V.K. Vytla LBNL, Berkeley, California, USA S. Babel, M. Boyes, G.W. Brown, D. Cha, B. Hong, A. Ratti, C.H. Rivetta SLAC, Menlo Park, California, USA R. Bachimanchi, C. Hovater, D.J. Seidman JLab, Newport News, Virginia, USA B.E. Chase, E. Cullerton, Q. Du, J. Einstein, D.W. Klepec Fermilab, Batavia, Illinois, USA
	Funding: Work supported by the LCLS-II Project and the U.S. Department of Energy, Contract DE-AC02-76SF00515 The LCLS-II is a CW superconducting linac under construction to drive an X-ray FEL. The energy and timing stability requirements of the FEL drive the need for very high precision RF control. This paper summarize the design considerations and early demonstration of the performance of the components and system we developed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-FRA2IO02
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Paper

Title

Other Keywords

Page

MOA2IO02

The BNL EBPM Electronics, High Performance for Next Generation Storage Rings

ion, storage-ring, operation, experiment

1

K. Vetter
ORNL, Oak Ridge, Tennessee, USA
W.X. Cheng, J. Mead, B. Podobedov, Y. Tian
BNL, Upton, Long Island, New York, USA

Funding: DOE contract DE-AC02-98CH10886
A custom state-of-the-art RF BPM (EBPM) has been developed and commissioned at the Brookhaven National Laboratory (BNL) National Synchrotron Light Source II (NSLS-II). A collaboration between Lawrence Berkeley National Laboratory (LBNL) Advanced Light Source (ALS) and BNL has proven to be a key element in the success of the NSLS-II EBPM. High stability coherent signal processing has allowed for demonstrated 200nm RMS spatial resolution and true turn-by-turn position measurement capability. Sub-micron 24 hr. stability has been demonstrated at NSLS-II by use of 0.01C RMS thermal regulation of the electronics racks without the need of active pilot tone correction.

Slides MOA2IO02 [4.334 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-MOA2IO02

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MOA2CO03

Measurement of Tune Shift with Amplitude from BPM Data with a Single Kicker Pulse

ion, kicker, lattice, experiment

6

Y. Hidaka, W.X. Cheng, B. Podobedov
BNL, Upton, Long Island, New York, USA

Funding: The study is supported by U.S. DOE under Contract No. DE-AC02-98CH10886.
Measurements of amplitude-dependent tune shift are critical for understanding of nonlinear single particle dynamics in storage rings. The conventional method involves scanning of the kicker amplitude while having a short bunch train at the top of the kicker pulse. In this paper we present a novel, alternative technique that uses a long continuous bunch train, or a sequence of bunch trains, that are spread along the ring, such that different bunches experience different kick amplitudes with a single shot of a kicker pulse. With these beams, a curve of tune shift with amplitude can be extracted from the recently added new NSLS-II BPM feature called gated turn-by-turn (TbT) BPM data that can resolve bunches within a turn, either alone or together with a bunch-by-bunch BPM data. This technique is immune to pulse-to-pulse jitters and long-term machine drift.

Slides MOA2CO03 [1.961 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-MOA2CO03

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TUPOA17

A Longitudinal Digital Mode Damper System for the Fermilab Booster

ion, booster, cavity, damping

320

N. Eddy, W. Pellico, A. Semenov, D.C. Voy, A.M. Waller
Fermilab, Batavia, Illinois, USA

Funding: This work was supported by the U.S. Department of Energy under contract No. DE-AC02-07CH11359.
The Fermilab Booster accelerates bunches and accelerates proton beams from 400 MeV to 8 GeV. During the acceleration the Radio Frequency (RF) cavities are swept from 38MHz to 52.8MHz and requires crossing through transition where accelerating phase is shifted 90 degrees. In order to keep the beam stable and minimize losses and emittance growth a longitudinal damping system is required. This has traditionally been done by dedicated analog electronics designed to operate on specific beam modes for frequencies of instabilities. A complete digital implementation has been developed for this same purpose. The new digital system features and performance are detailed.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-TUPOA17

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TUPOA41

FPGA Control of Coherent Pulse Stacking

ion, cavity, controls, FPGA

367

Y.L. Xu, J.M. Byrd, L.R. Doolittle, Q. Du, G. Huang, W. Leemans, R.B. Wilcox, Y. Yang
LBNL, Berkeley, California, USA
J. Dawson
LLNL, Livermore, California, USA
A. Galvanauskas, J.M. Ruppe
University of Michigan, Ann Arbor, Michigan, USA

Coherent pulse stacking (CPS) is a new time-domain coherent addition technique that stacks several optical pulses into a single output pulse, enabling high pulse energy from fiber lasers. Due to advantages of precise timing and fast processing, we use an FPGA to process digital signals and do feedback control so as to realize stacking-cavity stabilization. We develop a hardware and firmware design platform to support the coherent pulse stacking application. A firmware bias control module stabilizes the amplitude modulator at the minimum of its transfer function. A cavity control module ensures that each optical cavity is kept at a certain individually-prescribed and stable round-trip phase with 2.5 deg rms phase error.

Poster TUPOA41 [5.546 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-TUPOA41

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TUPOA67

Helium Pressure Vessel Jacketing of the Fermilab SSR1 Single Spoke SC Cavities

ion, cavity, real-time, cryomodule

418

E.C. Bonnema, E.K. Cunningham
Meyer Tool & MFG, Oak Lawn, Illinois, USA

Meyer Tool recently completed the welding of the liquid helium pressure vessel jackets around ten (10) superconducting single spoke niobium cavities for Fermilab. The SSR1 cavities are intended for use in the PIP-II Injector Experiment Cryomodule. Meyer Tool's scope of supply included review of the Fermilab Pressure Rating Analysis Document and the development of fabrication details and a fabrication sequence to meet that document's requirements, while minimizing the effects of jacketing cavity frequency, and the actual jacketing of the cavities. This paper will focus on the development of the fabrication details and sequence and how the details and sequence evolved over the course of welding and final machining of the ten (10) jackets. As the frequency of these cavities is critical the fabrication sequence accommodated numerous in process frequency checks, a frequency tuning step prior to the final weld, the use of thermal cameras to monitor weld heat input into the cavity, and post welding final machining of critical features. Lessons learned from this fabrication will be discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-TUPOA67

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TUPOA71

Beam Stability During Top Off Operation at NSLS-II Storage Ring

ion, injection, operation, storage-ring

425

W.X. Cheng, B. Bacha, Y. Li, O. Singh, Y. Tian
BNL, Upton, Long Island, New York, USA

NSLS-II storage ring started top off operation since Oct 2015. User operation current has been gradually increased to 250mA. Observations of beam stabilities during top-off operations will be presented. Total beam current was typically maintained within ±0.5% and bunch to bunch current variation was less than 20%. Injection transition during top-off was measured bunch by bunch digitizer, and BPM to analyze the orbit motion at various bandwidths (turn by turn, 10kHz and 10Hz rate). Coupled bunch unstable motions were monitored. As the vacuum pressure improves, fast-ion instability is not as severe compared to early stage of commissioning/operation, but still observed as the dominant instability. Resistive wall instability is noticed as more in-vacuum-undulator (IVU) gaps closed. xBPM measured photon stability and electron beam stability at top off injection have been evaluated. Short term and long term orbit stabilities will be reported.

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TUPOB02

Development of the Method for Evaluation of a Super-Conducting Traveling Wave Cavity With a Feedback Waveguide

ion, cavity, GUI, simulation

480

R.A. Kostin
LETI, Saint-Petersburg, Russia
P.V. Avrakhov, A. Kanareykin
Euclid TechLabs, LLC, Solon, Ohio, USA
N. Solyak, V.P. Yakovlev
Fermilab, Batavia, Illinois, USA

Funding: DOE SBIR # DE-SC0006300
Euclid Techlabs is developing a superconducting traveling wave (SCWT) cavity with a feedback waveguide [1] and has demonstrated a traveling wave at room temperature [2] in a 3-cell SCTW cavity [3]. A special method described in this paper was developed for cavity evaluation. It is based on an S-matrix approach. The cavity tuning procedure based on this method is described.

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TUPOB45

A Model to Simulate the Effect of a Transverse Feedback System on Single Bunch Instability Thresholds

ion, simulation, kicker, damping

596

G. Bassi, A. Blednykh, V.V. Smaluk
BNL, Upton, Long Island, New York, USA
Z. Yang
Auburn University, Auburn, USA

Funding: DOE Contract No. DE-AC02-98CH10886
A model to simulate the effect of a transverse feedback system is implemented in SPACE, a parallel, self-consistent code for collective effects. As an application, we discuss single bunch instability thresholds in the NSLS-II storage ring and compare the numerical results with measurements.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-TUPOB45

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TUPOB55

Optimize the Algorithm for the Global Orbit Feedback at Fixed Energies and During Acceleration in RHIC

ion, acceleration, proton, lattice

612

C. Liu, R.L. Hulsart, K. Mernick, R.J. Michnoff, M.G. Minty
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy.
To combat triplets vibration, the global orbit feedback system with frequency about 10 Hz was developed and en- gaged in operation at injection and top energy in 2010, dur- ing beam acceleration in 2012 at RHIC. The system has performed well with keeping 6 out of 12 eigenvalues for the orbit response matrix. However, we observed correc- tor current transients with the lattice for polarized proton program in 2015 which resulted in corrector power supply trips. In this report, we will present the observation, an- alyze the cause and also optimize the feedback algorithm to overcome the newly emerged problem with the feedback system.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-TUPOB55

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WEA3CO04

Impedance Characterization and Collective Effects in the MAX IV 3 GeV Ring

ion, impedance, synchrotron, experiment

843

G. Skripka, Å. Andersson, P.F. Tavares
MAX IV Laboratory, Lund University, Lund, Sweden
F.J. Cullinan, R. Nagaoka
SOLEIL, Gif-sur-Yvette, France

Collective instabilities in the MAX IV 3 GeV storage ring are enhanced by the combination of high beam current, ultralow emittance and small vacuum chamber aperture. To mitigate instabilities by Landau damping and improve lifetime three passive harmonic cavities are installed to introduce synchrotron tune spread and bunch lengthening respectively. We present the results of studies of collective effects driven by the machine impedance. Bunch lengthening and detuning were measured to characterize the effective impedance and estimate the effect of the harmonic cavity potential. Investigations of collective effects as a function of parameters such as beam current and chromaticity are discussed.

Slides WEA3CO04 [3.845 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-WEA3CO04

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WEPOB04

Beamline-Controlled Steering of Source-Point Angle at the Advanced Photon Source

ion, EPICS, controls, operation

887

L. Emery, G.I. Fystro, H. Shang, M.L. Smith
ANL, Argonne, Illinois, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357
An EPICS-based steering software system has been implemented for beamline personnel to directly steer the angle of the synchrotron radiation sources at the Advanced Photon Source. A script running on a workstation monitors "start steering" beamline EPICS records, and effects a steering by the value of "angle request" EPICS records that beamlines have set. The new system effectively bypasses floor coordinators and MCR operators, and makes the steering process much faster than before, although these older protocols can still be used. As with the original steering there are EPICS alarm limits that prevent large steering from occurring and avoid other problems. Error messages and statuses, OPI windows and alarm configurations are provided to the beamlines and the accelerator operators. Underpinning this new steering protocol is the recent refinement of the global orbit feedback process whereby feedforward of dipole corrector set points and orbit set points are used to create a local steering bump in a rapid and seamless way. In principle and in practice, many simultaneous steering commands from many beamlines are possible. We report on a complete 3-month run of experience.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-WEPOB04

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WEPOB08

Collective Effects at Injection for the APS-U MBA Lattice

ion, injection, collective-effects, lattice

901

R.R. Lindberg, M. Borland
ANL, Argonne, Illinois, USA
A. Blednykh
BNL, Upton, Long Island, New York, USA

Funding: U.S. Dept. of Energy Office of Sciences under Contract No. DE-AC02-06CH11357
The Advanced Photon Source has proposed an upgrade to a multi-bend achromat (MBA) with a proposed timing mode calls for 48 bunches of 15 nC each. In this mode of operation we find that phase space mismatch from the booster can drive large wakefields that in turn may limit the current below that of the nominal collective instability threshold. We show that collective effects at injection lead to emittance growth that makes usual off-axis accumulation very challenging. On-axis injection ameliorates many of these issues, but we find that transverse feedback is still required. We explore the role of impedance, feedback, and phase-space mismatch on transverse instabilities at injection.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-WEPOB08

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THPOA30

SCHARGEV 1.0 - Strong Space Charge Vlasov Solver

ion, space-charge, impedance, dipole

1164

T. Zolkin, A.V. Burov
Fermilab, Batavia, Illinois, USA

The space charge (SC) is known to be one of the major limitations for the collective transverse beam stability. When space charge is strong, i.e. SC tune shift much greater than synchrotron tune, the problem allows an exact analytical solution. For that practically important case we present a fast and effective Vlasov solver SCHARGEV (Space CHARGE Vlasov) which calculates a complete eigensystem (spatial shapes of modes and frequency spectra) and therefore provides the growth rates and the thresholds of instabilities. SCHARGEV 1.0 includes driving and detuning wake forces, and, any feedback system (damper). In the next version we will include coupled bunch interaction and Landau damping. Numerical examples for FermiLab Recycler and CERN SPS are presented.

Poster THPOA30 [1.493 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-THPOA30

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FRA2IO02

High Precision RF Control for the LCLS-II

ion, cavity, controls, LLRF

1292

G. Huang, K. Campbell, L.R. Doolittle, J.A. Jones, C. Serrano, V.K. Vytla
LBNL, Berkeley, California, USA
S. Babel, M. Boyes, G.W. Brown, D. Cha, B. Hong, A. Ratti, C.H. Rivetta
SLAC, Menlo Park, California, USA
R. Bachimanchi, C. Hovater, D.J. Seidman
JLab, Newport News, Virginia, USA
B.E. Chase, E. Cullerton, Q. Du, J. Einstein, D.W. Klepec
Fermilab, Batavia, Illinois, USA

Funding: Work supported by the LCLS-II Project and the U.S. Department of Energy, Contract DE-AC02-76SF00515
The LCLS-II is a CW superconducting linac under construction to drive an X-ray FEL. The energy and timing stability requirements of the FEL drive the need for very high precision RF control. This paper summarize the design considerations and early demonstration of the performance of the components and system we developed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-FRA2IO02

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