IPAC2017 - List of Keywords (beam-loading)

Paper	Title	Other Keywords	Page
TUZB1	Final Results From the Clic Test Facility (CTF3)	linac, operation, acceleration, emittance	1269
	R. Corsini CERN, Geneva, Switzerland
	The unique CLIC TEST Facility (CTF3) has been built more than a decade ago to demonstrate the feasibility of the CLIC two beam acceleration scheme. The emphasis was one the high current drive beam generation using a fully loaded highly efficient linac and a complex combination scheme to increase beam current and bunch repetition frequency. This drive beam has been used for deceleration experiments and two beam acceleration. A wealth of relevant results for accelerator physics even beyond CLIC has been obtained and will be presented. The rf to beam efficiency of the linac exceeds 95%, after combination the 28 A drive beam with 12 GHz bunch repetition rate has been used to extract more than 50% of its energy producing 1.3 GW of 12 GHz power as well as performing two beam acceleration at 12 GHz with gradients up to 150 MV/m.
	Slides TUZB1 [23.702 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUZB1
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TUPAB011	Beam Dynamics Simulation in Two Versions of New Photogun for FCC-ee Electron Injector Linac	linac, injection, simulation, electron	1326
	S.M. Polozov, T.V. Bondarenko MEPhI, Moscow, Russia
	New high-energy frontier project FCC is now under development at CERN. The project includes three modes: ee, hh and eh interactions for FCC. New injection system for FCC-ee is planned to consist of new ~ 2-14 GeV electron linac and electron-positron converter. Injector linac should provide two regimes: ~250 pC bunches for injection and ~6 nC bunches for e⁻/e⁺ conversion. Two possible schemes of photogun are comprised and results of beam dynamics simulation in both FCC-ee injection linac photoguns are discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPAB011
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TUPAB017	Results of the Beam-Loading Breakdown Rate Experiment at the CLIC Test Facility CTF3	experiment, operation, klystron, linac	1348
	E. Senes, T. Argyropoulos, N. Catalán Lasheras, R. Corsini, D. Gamba, J. Giner Navarro, A. Grudiev, G. McMonagle, R. Rajamaki, X.F.D. Stragier, I. Syratchev, F. Tecker, W. Wuensch CERN, Geneva, Switzerland J. Giner Navarro IFIC, Valencia, Spain R. Rajamaki Aalto University, School of Science and Technology, Aalto, Finland E. Senes Torino University, Torino, Italy
	The RF breakdown rate is crucial for the luminosity performance of the CLIC linear collider. The required breakdown rate at the design gradient of 100 MV/m has been demonstrated, without beam presence, in a number of 12 GHz CLIC prototype structures. Nevertheless, the beam-loading at CLIC significantly changes the field profile inside the structures, and the behaviour with beam needs to be understood. A dedicated experiment in the CLIC Test Facility CTF3 to determine the effect of beam on the breakdown rate has been collecting breakdown data throughout the year 2016. The complete results of the experiment and the effect of the beam-loading on the breakdown rate are presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPAB017
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TUPVA091	Batch Compression Scheme for Multi-MW J-PARC	injection, booster, cavity, proton	2294
	C. Ohmori, M. Furusawa, K. Hara, K. Hasegawa, Y. Sugiyama, M. Yoshii KEK, Tokai, Ibaraki, Japan M. Nomura, T. Shimada, F. Tamura, M. Yamamoto JAEA/J-PARC, Tokai-mura, Japan
	Replacement of all J-PARC MR cavities has completed in this summer to increase the RF voltage. Nine sets of new high-gradient FT3L cavities will generate the required RF voltage for the 1.16 second cycle operation. Upgrade of magnet power supplies is planned and the cycle time becomes 1.3 seconds from the present 2.48 seconds in FY2018 to achieve the beam power of 750 kW-1 MW. For the further improvement of beam power, a new rapid-cycling booster is considered to increase the injection energy of the MR from 3 GeV to 6-8 GeV. By the reduction of the space charge effects, the injection time can be extended and a batch compression scheme becomes possible. It will increase the number of bunches from 8 to 11 or 12 during the beam injection. And, recent beam study of the 3 GeV RCS shows the potential capability of 6.6·10¹³ proton per bunch. Combining these improvements with the booster, the beam power of 3 MW will be manageable.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPVA091
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WEPIK056	Compensation of Transient Beam Loading with Detuned Cavities at BESSY II	cavity, operation, experiment, synchrotron	3056
	M. Ruprecht, P. Goslawski, F. Kramer, M. Ries HZB, Berlin, Germany
	This paper presents operational experience and use cases of cavity operation in the synchrotron light source BESSY II, where an active or passive cavity is detuned by a small fraction of the harmonic number. If the detuning is an integer multiple of the fundamental RF harmonic, the distortion of the longitudinal phase space is periodic with the revolution, which allows for the compensation of fill pattern induced transients. Measurements at BESSY II are presented, where a fundamental cavity is detuned to decrease the effects of transient beam loading. Thus, reducing the phase transient and increasing the beam life time. Calculations depicting the application of this scheme for the future project BESSY VSR[] are presented. A. Jankowiak, J. Knobloch, P. Goslawski, and N. Neumann, eds., BESSY VSR - Technical Design Study, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, 2015.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK056
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WEPIK118	Synchronous Phase Shift from Beam Loading Analysis	cavity, storage-ring, operation, resonance	3227
	G. Bassi, A. Blednykh, J. Rose, V.V. Smaluk, J. Tagger BNL, Upton, Long Island, New York, USA
	We discuss measurements, performed in the NSLS-II storage ring, of the synchronous phase shift as a function of single bunch current from beam loading parameters. The synchronous phase is calculated from the forward and reflected power measured in the RF cavities. The comparison with direct synchronous phase measurements shows good agreement.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK118
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THPAB003	Harmonic RF System for the ESRF EBS	cavity, impedance, simulation, synchrotron	3684
	N. Carmignani, J. Jacob, B. Nash, S.M. White ESRF, Grenoble, France
	A harmonic RF system for bunch lengthening to increase the Touschek lifetime of the ESRF Extemely Brilliant Source (EBS) is under study. Multiparticle simulations have been performed to study the bunch lengthening and the bunch shape with impedance effect and with third or fourth harmonic cavities. The effect of a harmonic RF system on the microwave instability is studied, finding an increase in the threshold. The AC Robinson instability threshold with a superconducting harmonic cavity has been studied with multiparticle simulations.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB003
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THPAB099	Challenges of a Stable ERL Operation Concerning the Digital RF Control System of the S-DALINAC	controls, operation, HOM, linac	3951
	M. Steinhorst, M. Arnold, U. Bonnes, C. Burandt, N. Pietralla TU Darmstadt, Darmstadt, Germany T. Kürzeder HIM, Mainz, Germany
	Funding: Supported by the DFG through RTG 2128. The superconducting recirculating electron linear accelerator S-DALINAC is the central large-scale research device of the institute for nuclear physics at the TU Darmstadt in Germany. In 2015/2016 the S-DALINAC received an upgrade to three recirculations. The new beam line enables in addition to higher maximum energies the possibility to operate the S-DALINAC as an Energy Recovery Linac (ERL). Therefore the current rf control system encounters new requirements for ERL operation. Since 2010 a digital rf control system is successfully used for the control of the superconducting cavities. This system was not built and optimized for the control of an ERL. This contribution is discussing the expected challenges of an ERL operation regarding the existing digital rf control system.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB099
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THPAB100	On the Impact of Empty Buckets on the Ferrite Cavity Control Loop Dynamics in High Intensity Hadron Synchrotrons	controls, cavity, resonance, simulation	3954
	D. Mihailescu Stoica, D. Domont-Yankulova Technische Universität Darmstadt (TU Darmstadt, RMR), Darmstadt, Germany D. Domont-Yankulova, H. Klingbeil TEMF, TU Darmstadt, Darmstadt, Germany H. Klingbeil, D.E.M. Lens GSI, Darmstadt, Germany
	Funding: Supported by the Helmholtz Graduate School for Hadron and Ion Research Due to technical reasons two of ten buckets have to stay empty in the planned SIS100 synchrotron at the GSI Helmholtzzentrum für Schwerionenforschung. The planned low level RF control systems consist of linear P and PI type controllers. These are responsible to maintain a desired phase and amplitude of the gap voltage. In addition the cavity is controlled to follow a prescribed resonance frequency ramp. In SIS100 the acceleration will be performed by ferrite cavities with comparatively small quality factors. Therefore, effects resulting from transient beam loading have to be expected. Influences due to empty buckets are analysed in the frequency domain and particle tracking simulations are carried out to estimate the effect on the overall system with particular consideration of emittance growth and particle loss.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB100
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THPAB103	On-Line RF Amplitude and Phase Calibration	cavity, controls, operation, LLRF	3957
	M.K. Grecki, V. Ayvazyan, J. Branlard, M. Hoffmann, M. Omet, H. Schlarb, Ch. Schmidt DESY, Hamburg, Germany
	The accelerating RF field has crucial importance on the beam properties. It is not only used just to accelerate particles but also to shape the bunches at bunch compressors. It is really important to control and measure the field as seen by the beam while usually only indirect (not using the beam) field measurements are available*. Since they are affected by many contributions the measurements must be always calibrated to the beam. Usually this calibration is performed at special operating conditions that prevents normal operation of the accelerator. During normal operation the calibrations is assumed to not drift which is certainly not perfectly true and introduce some control errors. The paper shows how to extract the RF-beam calibration from RF signals during normal operating condition (when RF feed-back, beam loading compensation, learning feed-forward etc. are active). All the algorithms and computations were performed on signals recorded at FLASH accelerator but the main idea is general and can be used at other locations as well.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB103
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THPAB134	Latest Development of the ALBA DLLRF	cavity, LLRF, interlocks, rf-amplifier	4034
	A. Salom, B. Bravo, M. Broseta, E. Morales, J.R. Ocampo, F. Pérez, P. Solans ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain
	The Digital LLRF of ALBA has been implemented using commercial cPCI boards with Virtex-4 FPGA, fast ADCs and fast DACs. The firmware of the FPGA is based on IQ demodulation technique and the main feed-back loops adjust the phase and amplitude of the cavity voltage and also the resonance frequency of the cavity. This paper summarizes the latest LLRF developments done to improve performance of the RF systems and beam stability, including feed-forward loops based on phase modulation to compensate disturbances due to RF trip, beam loading compensation and Power Unbalance Compensation Loop for RF amplifiers Combination.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB134
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THPIK037	Simulation Study of Normal-Conducting Double RF System for the 3-GeV KEK Light Source Project	cavity, storage-ring, emittance, simulation	4176
	N. Yamamoto, S. Sakanaka, T. Takahashi KEK, Ibaraki, Japan
	For the proposed 3-GeV KEK Light Source (KEK-LS) project, a double RF system using 500-MHz accelerating and 1.5-GHz third-harmonic cavities is under consideration. To mitigate intrabeam scattering due to ultra-low emittance, the bunch length will be elongated using the harmonic cavities which is based on the TM020 resonant mode. An accelerating cavity based on this mode was first proposed by Ego et al., and we found it very suitable for the harmonic cavities due to the following reasons: 1) it has high unloaded-Q and high stored electromagnetic energy which result in the reduction of transient beam-loading effect due to bunch gaps, and 2) efficient damping of higher (or lower) order modes is possible. Our investigations based on numerical simulations predicted the bunch elongation by a factor of 3.1 when realistic bunch-gaps were assumed. To improve the bunch elongation further, we also proposed to compensate the transient beam loading with two realistic measures: 1) compensation of rf voltages due to feedforward technique, and 2) compensation using a separate rf cavity. We will present our study on the double rf system based on numerical simulations. K. Harada et al., IPAC2016, THPMB012. ** H. Ego et al., Proceedings of the 11-th Annual Meeting of Particle Accelerator Society of Japan, Aug. 9-11, 2014, MOOL14 [in Japanese].
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPIK037
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THPIK043	Design and Optimization of a 2MeV X-Band Side Coupled Accelerating Structure	coupling, impedance, simulation, linac	4193
	H. Yuan IHEP, Beijing, People's Republic of China
	An X-band bi-period side-coupled accelerating structure has been designed in this paper. The structure's working frequency is 9.3GHz. '/2 mode is chosen for the structure's stability. There are 11 accelerating cells, the first 5 work as non-light velocity part while the other 6 work as light velocity part. After CST simulation, the coupling constant between accelerating cells and coupling cells is 5%, efficient shunt impedance is 142M'/m. For the beam dynamic analysis, the particle energy is selected to be 2 MeV and the peak current is 60 mA for the radiation dosage limits by national standard. After Pamela optimization, the particle's capture efficiency is more than 30%. To feed power into the structure, a coupler is designed in the middle of the structure and the coupling coefficient is 1.4. The structure is manufactured and the measurement result accords well with designing value.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPIK043
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THPIK048	Design of Rapid Tuning System for a Ferrite-Loaded Cavity with Heavy Beam Loading	cavity, controls, feedback, LLRF	4203
	X. Li, H. Sun, F.C. Zhao, J.Y. Zhu IHEP, Beijing, People's Republic of China
	A high power, broadband and rapid frequency sweeping RF system was developed to satisfy the demand of China Spallation Neutron source (CSNS)/ Rapid Cycling Synchrotron (RCS). The cavity tuning is the key issue which has great impact on the performance of the whole RF system. In order to satisfy the requirement of cavity dynamic tuning caused by the nonlinear characteristics of the ferrite material, some new technologies were developed and applied. In this paper, the overall design of the tuning system will be introduced. The ensuing discussion will be focused on the choice of different types bias current supplies, the control algorithm of LLRF system and the beam loading compensation issues.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPIK048
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Paper

Title

Other Keywords

Page

TUZB1

Final Results From the Clic Test Facility (CTF3)

linac, operation, acceleration, emittance

1269

R. Corsini
CERN, Geneva, Switzerland

The unique CLIC TEST Facility (CTF3) has been built more than a decade ago to demonstrate the feasibility of the CLIC two beam acceleration scheme. The emphasis was one the high current drive beam generation using a fully loaded highly efficient linac and a complex combination scheme to increase beam current and bunch repetition frequency. This drive beam has been used for deceleration experiments and two beam acceleration. A wealth of relevant results for accelerator physics even beyond CLIC has been obtained and will be presented. The rf to beam efficiency of the linac exceeds 95%, after combination the 28 A drive beam with 12 GHz bunch repetition rate has been used to extract more than 50% of its energy producing 1.3 GW of 12 GHz power as well as performing two beam acceleration at 12 GHz with gradients up to 150 MV/m.

Slides TUZB1 [23.702 MB]

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TUPAB011

Beam Dynamics Simulation in Two Versions of New Photogun for FCC-ee Electron Injector Linac

linac, injection, simulation, electron

1326

S.M. Polozov, T.V. Bondarenko
MEPhI, Moscow, Russia

New high-energy frontier project FCC is now under development at CERN. The project includes three modes: ee, hh and eh interactions for FCC. New injection system for FCC-ee is planned to consist of new ~ 2-14 GeV electron linac and electron-positron converter. Injector linac should provide two regimes: ~250 pC bunches for injection and ~6 nC bunches for e⁻/e⁺ conversion. Two possible schemes of photogun are comprised and results of beam dynamics simulation in both FCC-ee injection linac photoguns are discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPAB011

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TUPAB017

Results of the Beam-Loading Breakdown Rate Experiment at the CLIC Test Facility CTF3

experiment, operation, klystron, linac

1348

E. Senes, T. Argyropoulos, N. Catalán Lasheras, R. Corsini, D. Gamba, J. Giner Navarro, A. Grudiev, G. McMonagle, R. Rajamaki, X.F.D. Stragier, I. Syratchev, F. Tecker, W. Wuensch
CERN, Geneva, Switzerland
J. Giner Navarro
IFIC, Valencia, Spain
R. Rajamaki
Aalto University, School of Science and Technology, Aalto, Finland
E. Senes
Torino University, Torino, Italy

The RF breakdown rate is crucial for the luminosity performance of the CLIC linear collider. The required breakdown rate at the design gradient of 100 MV/m has been demonstrated, without beam presence, in a number of 12 GHz CLIC prototype structures. Nevertheless, the beam-loading at CLIC significantly changes the field profile inside the structures, and the behaviour with beam needs to be understood. A dedicated experiment in the CLIC Test Facility CTF3 to determine the effect of beam on the breakdown rate has been collecting breakdown data throughout the year 2016. The complete results of the experiment and the effect of the beam-loading on the breakdown rate are presented.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPAB017

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TUPVA091

Batch Compression Scheme for Multi-MW J-PARC

injection, booster, cavity, proton

2294

C. Ohmori, M. Furusawa, K. Hara, K. Hasegawa, Y. Sugiyama, M. Yoshii
KEK, Tokai, Ibaraki, Japan
M. Nomura, T. Shimada, F. Tamura, M. Yamamoto
JAEA/J-PARC, Tokai-mura, Japan

Replacement of all J-PARC MR cavities has completed in this summer to increase the RF voltage. Nine sets of new high-gradient FT3L cavities will generate the required RF voltage for the 1.16 second cycle operation. Upgrade of magnet power supplies is planned and the cycle time becomes 1.3 seconds from the present 2.48 seconds in FY2018 to achieve the beam power of 750 kW-1 MW. For the further improvement of beam power, a new rapid-cycling booster is considered to increase the injection energy of the MR from 3 GeV to 6-8 GeV. By the reduction of the space charge effects, the injection time can be extended and a batch compression scheme becomes possible. It will increase the number of bunches from 8 to 11 or 12 during the beam injection. And, recent beam study of the 3 GeV RCS shows the potential capability of 6.6·10¹³ proton per bunch. Combining these improvements with the booster, the beam power of 3 MW will be manageable.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPVA091

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WEPIK056

Compensation of Transient Beam Loading with Detuned Cavities at BESSY II

cavity, operation, experiment, synchrotron

3056

M. Ruprecht, P. Goslawski, F. Kramer, M. Ries
HZB, Berlin, Germany

This paper presents operational experience and use cases of cavity operation in the synchrotron light source BESSY II, where an active or passive cavity is detuned by a small fraction of the harmonic number. If the detuning is an integer multiple of the fundamental RF harmonic, the distortion of the longitudinal phase space is periodic with the revolution, which allows for the compensation of fill pattern induced transients. Measurements at BESSY II are presented, where a fundamental cavity is detuned to decrease the effects of transient beam loading. Thus, reducing the phase transient and increasing the beam life time. Calculations depicting the application of this scheme for the future project BESSY VSR[*] are presented.
* A. Jankowiak, J. Knobloch, P. Goslawski, and N. Neumann, eds., BESSY VSR - Technical Design Study, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, 2015.

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WEPIK118

Synchronous Phase Shift from Beam Loading Analysis

cavity, storage-ring, operation, resonance

3227

G. Bassi, A. Blednykh, J. Rose, V.V. Smaluk, J. Tagger
BNL, Upton, Long Island, New York, USA

We discuss measurements, performed in the NSLS-II storage ring, of the synchronous phase shift as a function of single bunch current from beam loading parameters. The synchronous phase is calculated from the forward and reflected power measured in the RF cavities. The comparison with direct synchronous phase measurements shows good agreement.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK118

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THPAB003

Harmonic RF System for the ESRF EBS

cavity, impedance, simulation, synchrotron

3684

N. Carmignani, J. Jacob, B. Nash, S.M. White
ESRF, Grenoble, France

A harmonic RF system for bunch lengthening to increase the Touschek lifetime of the ESRF Extemely Brilliant Source (EBS) is under study. Multiparticle simulations have been performed to study the bunch lengthening and the bunch shape with impedance effect and with third or fourth harmonic cavities. The effect of a harmonic RF system on the microwave instability is studied, finding an increase in the threshold. The AC Robinson instability threshold with a superconducting harmonic cavity has been studied with multiparticle simulations.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB003

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THPAB099

Challenges of a Stable ERL Operation Concerning the Digital RF Control System of the S-DALINAC

controls, operation, HOM, linac

3951

M. Steinhorst, M. Arnold, U. Bonnes, C. Burandt, N. Pietralla
TU Darmstadt, Darmstadt, Germany
T. Kürzeder
HIM, Mainz, Germany

Funding: Supported by the DFG through RTG 2128.
The superconducting recirculating electron linear accelerator S-DALINAC is the central large-scale research device of the institute for nuclear physics at the TU Darmstadt in Germany. In 2015/2016 the S-DALINAC received an upgrade to three recirculations. The new beam line enables in addition to higher maximum energies the possibility to operate the S-DALINAC as an Energy Recovery Linac (ERL). Therefore the current rf control system encounters new requirements for ERL operation. Since 2010 a digital rf control system is successfully used for the control of the superconducting cavities. This system was not built and optimized for the control of an ERL. This contribution is discussing the expected challenges of an ERL operation regarding the existing digital rf control system.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB099

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THPAB100

On the Impact of Empty Buckets on the Ferrite Cavity Control Loop Dynamics in High Intensity Hadron Synchrotrons

controls, cavity, resonance, simulation

3954

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

Funding: Supported by the Helmholtz Graduate School for Hadron and Ion Research
Due to technical reasons two of ten buckets have to stay empty in the planned SIS100 synchrotron at the GSI Helmholtzzentrum für Schwerionenforschung. The planned low level RF control systems consist of linear P and PI type controllers. These are responsible to maintain a desired phase and amplitude of the gap voltage. In addition the cavity is controlled to follow a prescribed resonance frequency ramp. In SIS100 the acceleration will be performed by ferrite cavities with comparatively small quality factors. Therefore, effects resulting from transient beam loading have to be expected. Influences due to empty buckets are analysed in the frequency domain and particle tracking simulations are carried out to estimate the effect on the overall system with particular consideration of emittance growth and particle loss.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB100

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THPAB103

On-Line RF Amplitude and Phase Calibration

cavity, controls, operation, LLRF

3957

M.K. Grecki, V. Ayvazyan, J. Branlard, M. Hoffmann, M. Omet, H. Schlarb, Ch. Schmidt
DESY, Hamburg, Germany

The accelerating RF field has crucial importance on the beam properties. It is not only used just to accelerate particles but also to shape the bunches at bunch compressors. It is really important to control and measure the field as seen by the beam while usually only indirect (not using the beam) field measurements are available*. Since they are affected by many contributions the measurements must be always calibrated to the beam. Usually this calibration is performed at special operating conditions that prevents normal operation of the accelerator. During normal operation the calibrations is assumed to not drift which is certainly not perfectly true and introduce some control errors. The paper shows how to extract the RF-beam calibration from RF signals during normal operating condition (when RF feed-back, beam loading compensation, learning feed-forward etc. are active). All the algorithms and computations were performed on signals recorded at FLASH accelerator but the main idea is general and can be used at other locations as well.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB103

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THPAB134

Latest Development of the ALBA DLLRF

cavity, LLRF, interlocks, rf-amplifier

4034

A. Salom, B. Bravo, M. Broseta, E. Morales, J.R. Ocampo, F. Pérez, P. Solans
ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain

The Digital LLRF of ALBA has been implemented using commercial cPCI boards with Virtex-4 FPGA, fast ADCs and fast DACs. The firmware of the FPGA is based on IQ demodulation technique and the main feed-back loops adjust the phase and amplitude of the cavity voltage and also the resonance frequency of the cavity. This paper summarizes the latest LLRF developments done to improve performance of the RF systems and beam stability, including feed-forward loops based on phase modulation to compensate disturbances due to RF trip, beam loading compensation and Power Unbalance Compensation Loop for RF amplifiers Combination.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB134

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THPIK037

Simulation Study of Normal-Conducting Double RF System for the 3-GeV KEK Light Source Project

cavity, storage-ring, emittance, simulation

4176

N. Yamamoto, S. Sakanaka, T. Takahashi
KEK, Ibaraki, Japan

For the proposed 3-GeV KEK Light Source (KEK-LS) project*, a double RF system using 500-MHz accelerating and 1.5-GHz third-harmonic cavities is under consideration. To mitigate intrabeam scattering due to ultra-low emittance, the bunch length will be elongated using the harmonic cavities which is based on the TM020 resonant mode. An accelerating cavity based on this mode was first proposed by Ego et al.**, and we found it very suitable for the harmonic cavities due to the following reasons: 1) it has high unloaded-Q and high stored electromagnetic energy which result in the reduction of transient beam-loading effect due to bunch gaps, and 2) efficient damping of higher (or lower) order modes is possible. Our investigations based on numerical simulations predicted the bunch elongation by a factor of 3.1 when realistic bunch-gaps were assumed. To improve the bunch elongation further, we also proposed to compensate the transient beam loading with two realistic measures: 1) compensation of rf voltages due to feedforward technique, and 2) compensation using a separate rf cavity. We will present our study on the double rf system based on numerical simulations.
* K. Harada et al., IPAC2016, THPMB012.
** H. Ego et al., Proceedings of the 11-th Annual Meeting of Particle Accelerator Society of Japan, Aug. 9-11, 2014, MOOL14 [in Japanese].

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPIK037

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THPIK043

Design and Optimization of a 2MeV X-Band Side Coupled Accelerating Structure

coupling, impedance, simulation, linac

4193

H. Yuan
IHEP, Beijing, People's Republic of China

An X-band bi-period side-coupled accelerating structure has been designed in this paper. The structure's working frequency is 9.3GHz. '/2 mode is chosen for the structure's stability. There are 11 accelerating cells, the first 5 work as non-light velocity part while the other 6 work as light velocity part. After CST simulation, the coupling constant between accelerating cells and coupling cells is 5%, efficient shunt impedance is 142M'/m. For the beam dynamic analysis, the particle energy is selected to be 2 MeV and the peak current is 60 mA for the radiation dosage limits by national standard. After Pamela optimization, the particle's capture efficiency is more than 30%. To feed power into the structure, a coupler is designed in the middle of the structure and the coupling coefficient is 1.4. The structure is manufactured and the measurement result accords well with designing value.

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THPIK048

Design of Rapid Tuning System for a Ferrite-Loaded Cavity with Heavy Beam Loading

cavity, controls, feedback, LLRF

4203

X. Li, H. Sun, F.C. Zhao, J.Y. Zhu
IHEP, Beijing, People's Republic of China

A high power, broadband and rapid frequency sweeping RF system was developed to satisfy the demand of China Spallation Neutron source (CSNS)/ Rapid Cycling Synchrotron (RCS). The cavity tuning is the key issue which has great impact on the performance of the whole RF system. In order to satisfy the requirement of cavity dynamic tuning caused by the nonlinear characteristics of the ferrite material, some new technologies were developed and applied. In this paper, the overall design of the tuning system will be introduced. The ensuing discussion will be focused on the choice of different types bias current supplies, the control algorithm of LLRF system and the beam loading compensation issues.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPIK048

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