IPAC2021 - List of Keywords (beam-loading)

Paper	Title	Other Keywords	Page
MOPAB069	Equilibrium Bunch Density Distribution with Multiple Active and Passive RF Cavities	cavity, impedance, synchrotron, storage-ring	278
	A. Gamelin SOLEIL, Gif-sur-Yvette, France N. Yamamoto KEK, Ibaraki, Japan
	This paper describes a method to get the equilibrium bunch density distribution with an arbitrary number of active or passive RF cavities in uniform filling. This method is an extension of the one presented by M. Venturini which assumes a passive harmonic cavity and no beam loading in the main RF cavity. M. Venturini, "Passive higher-harmonic rf cavities with general settings and multibunch instabilities in electron storage rings," Physical Review Accelerators and Beams, 2018.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB069
About •	paper received ※ 17 May 2021 paper accepted ※ 23 June 2021 issue date ※ 23 August 2021
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MOPAB072	Single-Bunch Thresholds for the Diamond-II Storage Ring	impedance, cavity, simulation, storage-ring	290
	T. Olsson, R.T. Fielder DLS, Oxfordshire, United Kingdom
	The proposed Diamond Light Source upgrade will see the storage ring replaced with a multibend achromat lattice, increasing the capacity of the facility whilst reducing the emittance and providing higher brightness for the users. As part of the design work, tracking studies have been performed to determine the single-bunch thresholds including both the resistive-wall and geometric contributions to the impedance. As the machine design also foresees a third order harmonic cavity, the paper also provides an initial assessment of the effects of bunch lengthening on the single-bunch thresholds.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB072
About •	paper received ※ 18 May 2021 paper accepted ※ 01 June 2021 issue date ※ 23 August 2021
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TUXC03	Ferro-Electric Fast Reactive Tuner Applications for SRF Cavities	cavity, SRF, operation, controls	1305
	N.C. Shipman, A. Castilla, M.R. Coly, F. Gerigk, A. Macpherson, N. Stapley, H. Timko CERN, Geneva, Switzerland I. Ben-Zvi BNL, Upton, New York, USA G. Burt, A. Castilla Cockcroft Institute, Lancaster University, Lancaster, United Kingdom C.-J. Jing, A. Kanareykin Euclid TechLabs, Solon, Ohio, USA
	A Ferro-Electric fast Reactive Tuner (FE-FRT) is a novel type of RF cavity tuner containing a low loss ferroelectric material. FE-FRTs have no moving parts and allow cavity frequencies to be changed extremely quickly (on the timescale of 100s of ns or less). They are of particular interest for SRF cavities as they can be placed outside the liquid helium environment and without an FE-FRT it’s typically very difficult to tune SRF cavities quickly. FE-FRTs can be used for a wide variety of use cases including microphonics suppression, RF switching, and transient beam loading compensation. This promises entirely new operational capabilities, increased performance and cost savings for a variety of existing and proposed accelerators. An overview of the theory and potential applications will be discussed in detail.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUXC03
About •	paper received ※ 19 May 2021 paper accepted ※ 02 August 2021 issue date ※ 25 August 2021
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TUPAB015	Beam Loading Compensation of APS Cavity with Off-Crest Acceleration in ILC e-Driven Positron Source	positron, linac, electron, target	1368
	M. Kuriki, S. Konno, H. Nagoshi HU/AdSM, Higashi-Hiroshima, Japan T. Omori, J. Urakawa, K. Yokoya KEK, Ibaraki, Japan T. Takahashi Hiroshima University, Graduate School of Science, Higashi-Hiroshima, Japan
	In E-Driven positron source of ILC, the generated positron is captured by RF accelerator by APS cavity. The positron is initially placed at the deceleration phase and gradually slipped down to acceleration phase. Because the beam-loading is expected to be more than 1A with a multi-bunch format, the compensation is essential to obtain uniform intensity over the pulse. A conventional method for the compensation is controlling the timing, but it doesn’t work in off-crest case. In this manuscript, we discuss the compensation with the phase and amplitude modulation on the input RF.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB015
About •	paper received ※ 19 May 2021 paper accepted ※ 27 July 2021 issue date ※ 26 August 2021
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TUPAB220	Longitudinal Dynamics with Harmonic Cavities under the Over-stretching Conditions	cavity, detector, longitudinal-dynamics, bunching	1939
	J.Y. Xu, H.S. Xu IHEP, Beijing, People’s Republic of China
	Higher harmonic cavities (HHCs) are often used to lengthen the bunches, mainly for increasing the Touschek lifetime or for suppressing the coupled-bunch instabilities in electron storage rings. There have been quite many studies on the beam dynamics with the consideration of HHCs. We revisited the basic longitudinal dynamics with HHCs. The derivation of the longitudinal equations of motion with HHCs will be presented in this paper. The difference in the number of fixed points at different HHC settings (mainly under the over-stretching conditions) is also discussed.
	Poster TUPAB220 [1.082 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB220
About •	paper received ※ 19 May 2021 paper accepted ※ 02 August 2021 issue date ※ 29 August 2021
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TUPAB266	Periodic Transient Beam Loading Effects Predicted by a Semi-Analytical Method	cavity, storage-ring, wakefield, simulation	2086
	T.L. He, Z.H. Bai, G. Feng, W. Li, W.W. Li, G. Liu, L. Wang, H. Xu, S.C. Zhang USTC/NSRL, Hefei, Anhui, People’s Republic of China
	In this paper, we improve a semi-analytical method, which can be not only used for bunch lengthening under equilibrium conditions, but also applied to the prediction of a periodic transient beam loading effect. This periodic transient is induced by the presence of the passive harmonic cavity and might be encountered under specific conditions for a ultra-low emittance storage ring with a higher beam current.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB266
About •	paper received ※ 16 May 2021 paper accepted ※ 21 June 2021 issue date ※ 24 August 2021
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WEPAB244	Optimization and Machine Learning Applied to the RF Manipulations of Proton Beams in the CERN PS	operation, extraction, simulation, cavity	3201
	A. Lasheen, H. Damerau, S.C. Johnston CERN, Meyrin, Switzerland
	The 25 ns bunch spacing in the LHC is defined by a sequence of RF manipulations in the Proton Synchrotron (PS). Multiple RF systems covering a large range of revolution harmonics (7 to 21, 42, 84, 168) allow performing RF manipulations such as beam splitting, and non-adiabatic bunch shortening. For the nominal beam sent to LHC, each bunch is split in 12 in the PS. The relative amplitude and phase settings of the RF systems need to be precisely adjusted to minimize the bunch-by-bunch variations in intensity, longitudinal emittance, and bunch shape. However, due to transient beam-loading, the ideal settings, as well as the best achievable beam quality, vary with beam intensity. Slow drifts of the hardware may also affect beam quality. In this paper, automatized optimization routines based on particle simulations with intensity effects are presented, together with the first considerations of machine learning. The optimization routines are used to assess the best achievable longitudinal beam quality expected with the PS RF systems upgrades, in the framework of the LHC Injector Upgrade project.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB244
About •	paper received ※ 19 May 2021 paper accepted ※ 01 July 2021 issue date ※ 24 August 2021
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THPAB200	Cavity Control Modelling for SPS-to-LHC Beam Transfer Studies	cavity, controls, simulation, injection	4168
	L.E. Medina Medrano, T. Argyropoulos, P. Baudrenghien, H. Timko CERN, Geneva, Switzerland
	Funding: Research supported by the HL-LHC project. To accurately simulate injection losses in the LHC and the High-Luminosity LHC era, a realistic beam distribution model at SPS extraction is needed. To achieve this, the beam-loading compensation by the SPS cavity controller has to be included, as it modulates the bunch positions with respect to the rf buckets. This dynamic cavity control model also allows generating a more realistic beam halo, from which the LHC injection losses will mainly originate. In this paper, the implementation of the present SPS cavity controller in CERN’s Beam Longitudinal Dynamics particle tracking code is described. Just like in the machine, the feedback and feedforward controls are included in the simulation model, as well as the generator-beam-cavity interaction. Benchmarking against measurements of the generated beam distributions at SPS extraction are presented.
	Poster THPAB200 [4.164 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB200
About •	paper received ※ 18 May 2021 paper accepted ※ 27 July 2021 issue date ※ 26 August 2021
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THPAB272	Validation of Two Re-Buncher Cavities under High Beam Loading for LIPAc	cavity, LLRF, operation, MEBT	4343
	D. Gavela, I. Podadera, F. Toral CIEMAT, Madrid, Spain I. Moya Fusion for Energy, Garching, Germany F. Scantamburlo IFMIF/EVEDA, Rokkasho, Japan
	Funding: Work partially supported by the Spanish Ministry of Science and Innovation under project AIC-A-2011-0654 and FIS2013-40860-R Two re-buncher cavities were installed at the Medium Energy Beam Transport line of the LIPAc accelerator, presently being commissioned at Rokkasho (Japan). They are IH-type cavities with five gaps providing an effective voltage of 350 kV at 175 MHz for a nominal operation of 125 mA CW deuterons at 5 MeV. After full conditioning and beamline integration in Europe, the cavities were installed in the accelerator with special care given to the alignment with respect to the rest of the components. The RF line, cooling circuits, and instrumentation were also mounted. The cavities were operated with an FPGA-based LLRF system. A re-conditioning of the cavities was performed in the first place, followed by tests with a pulsed beam with increasing currents. A maximum pulsed beam current of 100 mA was reached while operating the buncher cavities, under which they reached voltages up to 340 kV and 260 kV respectively. As expected, the beam loading was significant, leading to a series of difficulties and required strategies for a good operation that are discussed in this paper. The effect on the beam dynamics, measured by beam position monitors downstream of the bunchers is also discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB272
About •	paper received ※ 19 May 2021 paper accepted ※ 02 September 2021 issue date ※ 18 August 2021
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THPAB322	Transient Beam Loading in the CBETA Multi-Turn ERL	cavity, linac, operation, SRF	4422
	N. Banerjee Enrico Fermi Institute, University of Chicago, Chicago, Illinois, USA G.H. Hoffstaetter Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: This work was supported by NSF Grant No. DMR0807731, DOE Award No. DE-SC0012704, and NYSERDA Agreement No. 102192. The Cornell-BNL ERL Test Accelerator (CBETA) is the first superconducting multi-turn ERL that has been commissioned at Cornell University in a low current mode. In this paper, we first discuss a new model of beam loading which is valid for the low injection energies used in CBETA. Using this model, we explore the effect of bunch patterns, beam turn-on, and turn-off transients on the fundamental mode of the 7-cell SRF cavities used in the main linac. In particular, we examine the operational constraints on the rf system at the design current of 40 mA.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB322
About •	paper received ※ 20 May 2021 paper accepted ※ 29 July 2021 issue date ※ 16 August 2021
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Paper

Title

Other Keywords

Page

MOPAB069

Equilibrium Bunch Density Distribution with Multiple Active and Passive RF Cavities

cavity, impedance, synchrotron, storage-ring

278

A. Gamelin
SOLEIL, Gif-sur-Yvette, France
N. Yamamoto
KEK, Ibaraki, Japan

This paper describes a method to get the equilibrium bunch density distribution with an arbitrary number of active or passive RF cavities in uniform filling. This method is an extension of the one presented by M. Venturini which assumes a passive harmonic cavity and no beam loading in the main RF cavity*.
*M. Venturini, "Passive higher-harmonic rf cavities with general settings and multibunch instabilities in electron storage rings," Physical Review Accelerators and Beams, 2018.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB069

About •

paper received ※ 17 May 2021 paper accepted ※ 23 June 2021 issue date ※ 23 August 2021

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MOPAB072

Single-Bunch Thresholds for the Diamond-II Storage Ring

impedance, cavity, simulation, storage-ring

290

T. Olsson, R.T. Fielder
DLS, Oxfordshire, United Kingdom

The proposed Diamond Light Source upgrade will see the storage ring replaced with a multibend achromat lattice, increasing the capacity of the facility whilst reducing the emittance and providing higher brightness for the users. As part of the design work, tracking studies have been performed to determine the single-bunch thresholds including both the resistive-wall and geometric contributions to the impedance. As the machine design also foresees a third order harmonic cavity, the paper also provides an initial assessment of the effects of bunch lengthening on the single-bunch thresholds.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB072

About •

paper received ※ 18 May 2021 paper accepted ※ 01 June 2021 issue date ※ 23 August 2021

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TUXC03

Ferro-Electric Fast Reactive Tuner Applications for SRF Cavities

cavity, SRF, operation, controls

1305

N.C. Shipman, A. Castilla, M.R. Coly, F. Gerigk, A. Macpherson, N. Stapley, H. Timko
CERN, Geneva, Switzerland
I. Ben-Zvi
BNL, Upton, New York, USA
G. Burt, A. Castilla
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
C.-J. Jing, A. Kanareykin
Euclid TechLabs, Solon, Ohio, USA

A Ferro-Electric fast Reactive Tuner (FE-FRT) is a novel type of RF cavity tuner containing a low loss ferroelectric material. FE-FRTs have no moving parts and allow cavity frequencies to be changed extremely quickly (on the timescale of 100s of ns or less). They are of particular interest for SRF cavities as they can be placed outside the liquid helium environment and without an FE-FRT it’s typically very difficult to tune SRF cavities quickly. FE-FRTs can be used for a wide variety of use cases including microphonics suppression, RF switching, and transient beam loading compensation. This promises entirely new operational capabilities, increased performance and cost savings for a variety of existing and proposed accelerators. An overview of the theory and potential applications will be discussed in detail.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUXC03

About •

paper received ※ 19 May 2021 paper accepted ※ 02 August 2021 issue date ※ 25 August 2021

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

TUPAB015

Beam Loading Compensation of APS Cavity with Off-Crest Acceleration in ILC e-Driven Positron Source

positron, linac, electron, target

1368

M. Kuriki, S. Konno, H. Nagoshi
HU/AdSM, Higashi-Hiroshima, Japan
T. Omori, J. Urakawa, K. Yokoya
KEK, Ibaraki, Japan
T. Takahashi
Hiroshima University, Graduate School of Science, Higashi-Hiroshima, Japan

In E-Driven positron source of ILC, the generated positron is captured by RF accelerator by APS cavity. The positron is initially placed at the deceleration phase and gradually slipped down to acceleration phase. Because the beam-loading is expected to be more than 1A with a multi-bunch format, the compensation is essential to obtain uniform intensity over the pulse. A conventional method for the compensation is controlling the timing, but it doesn’t work in off-crest case. In this manuscript, we discuss the compensation with the phase and amplitude modulation on the input RF.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB015

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paper received ※ 19 May 2021 paper accepted ※ 27 July 2021 issue date ※ 26 August 2021

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TUPAB220

Longitudinal Dynamics with Harmonic Cavities under the Over-stretching Conditions

cavity, detector, longitudinal-dynamics, bunching

1939

J.Y. Xu, H.S. Xu
IHEP, Beijing, People’s Republic of China

Higher harmonic cavities (HHCs) are often used to lengthen the bunches, mainly for increasing the Touschek lifetime or for suppressing the coupled-bunch instabilities in electron storage rings. There have been quite many studies on the beam dynamics with the consideration of HHCs. We revisited the basic longitudinal dynamics with HHCs. The derivation of the longitudinal equations of motion with HHCs will be presented in this paper. The difference in the number of fixed points at different HHC settings (mainly under the over-stretching conditions) is also discussed.

Poster TUPAB220 [1.082 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB220

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paper received ※ 19 May 2021 paper accepted ※ 02 August 2021 issue date ※ 29 August 2021

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TUPAB266

Periodic Transient Beam Loading Effects Predicted by a Semi-Analytical Method

cavity, storage-ring, wakefield, simulation

2086

T.L. He, Z.H. Bai, G. Feng, W. Li, W.W. Li, G. Liu, L. Wang, H. Xu, S.C. Zhang
USTC/NSRL, Hefei, Anhui, People’s Republic of China

In this paper, we improve a semi-analytical method, which can be not only used for bunch lengthening under equilibrium conditions, but also applied to the prediction of a periodic transient beam loading effect. This periodic transient is induced by the presence of the passive harmonic cavity and might be encountered under specific conditions for a ultra-low emittance storage ring with a higher beam current.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB266

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paper received ※ 16 May 2021 paper accepted ※ 21 June 2021 issue date ※ 24 August 2021

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WEPAB244

Optimization and Machine Learning Applied to the RF Manipulations of Proton Beams in the CERN PS

operation, extraction, simulation, cavity

3201

A. Lasheen, H. Damerau, S.C. Johnston
CERN, Meyrin, Switzerland

The 25 ns bunch spacing in the LHC is defined by a sequence of RF manipulations in the Proton Synchrotron (PS). Multiple RF systems covering a large range of revolution harmonics (7 to 21, 42, 84, 168) allow performing RF manipulations such as beam splitting, and non-adiabatic bunch shortening. For the nominal beam sent to LHC, each bunch is split in 12 in the PS. The relative amplitude and phase settings of the RF systems need to be precisely adjusted to minimize the bunch-by-bunch variations in intensity, longitudinal emittance, and bunch shape. However, due to transient beam-loading, the ideal settings, as well as the best achievable beam quality, vary with beam intensity. Slow drifts of the hardware may also affect beam quality. In this paper, automatized optimization routines based on particle simulations with intensity effects are presented, together with the first considerations of machine learning. The optimization routines are used to assess the best achievable longitudinal beam quality expected with the PS RF systems upgrades, in the framework of the LHC Injector Upgrade project.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB244

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paper received ※ 19 May 2021 paper accepted ※ 01 July 2021 issue date ※ 24 August 2021

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THPAB200

Cavity Control Modelling for SPS-to-LHC Beam Transfer Studies

cavity, controls, simulation, injection

4168

L.E. Medina Medrano, T. Argyropoulos, P. Baudrenghien, H. Timko
CERN, Geneva, Switzerland

Funding: Research supported by the HL-LHC project.
To accurately simulate injection losses in the LHC and the High-Luminosity LHC era, a realistic beam distribution model at SPS extraction is needed. To achieve this, the beam-loading compensation by the SPS cavity controller has to be included, as it modulates the bunch positions with respect to the rf buckets. This dynamic cavity control model also allows generating a more realistic beam halo, from which the LHC injection losses will mainly originate. In this paper, the implementation of the present SPS cavity controller in CERN’s Beam Longitudinal Dynamics particle tracking code is described. Just like in the machine, the feedback and feedforward controls are included in the simulation model, as well as the generator-beam-cavity interaction. Benchmarking against measurements of the generated beam distributions at SPS extraction are presented.

Poster THPAB200 [4.164 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB200

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paper received ※ 18 May 2021 paper accepted ※ 27 July 2021 issue date ※ 26 August 2021

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THPAB272

Validation of Two Re-Buncher Cavities under High Beam Loading for LIPAc

cavity, LLRF, operation, MEBT

4343

D. Gavela, I. Podadera, F. Toral
CIEMAT, Madrid, Spain
I. Moya
Fusion for Energy, Garching, Germany
F. Scantamburlo
IFMIF/EVEDA, Rokkasho, Japan

Funding: Work partially supported by the Spanish Ministry of Science and Innovation under project AIC-A-2011-0654 and FIS2013-40860-R
Two re-buncher cavities were installed at the Medium Energy Beam Transport line of the LIPAc accelerator, presently being commissioned at Rokkasho (Japan). They are IH-type cavities with five gaps providing an effective voltage of 350 kV at 175 MHz for a nominal operation of 125 mA CW deuterons at 5 MeV. After full conditioning and beamline integration in Europe, the cavities were installed in the accelerator with special care given to the alignment with respect to the rest of the components. The RF line, cooling circuits, and instrumentation were also mounted. The cavities were operated with an FPGA-based LLRF system. A re-conditioning of the cavities was performed in the first place, followed by tests with a pulsed beam with increasing currents. A maximum pulsed beam current of 100 mA was reached while operating the buncher cavities, under which they reached voltages up to 340 kV and 260 kV respectively. As expected, the beam loading was significant, leading to a series of difficulties and required strategies for a good operation that are discussed in this paper. The effect on the beam dynamics, measured by beam position monitors downstream of the bunchers is also discussed.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB272

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paper received ※ 19 May 2021 paper accepted ※ 02 September 2021 issue date ※ 18 August 2021

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THPAB322

Transient Beam Loading in the CBETA Multi-Turn ERL

cavity, linac, operation, SRF

4422

N. Banerjee
Enrico Fermi Institute, University of Chicago, Chicago, Illinois, USA
G.H. Hoffstaetter
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: This work was supported by NSF Grant No. DMR0807731, DOE Award No. DE-SC0012704, and NYSERDA Agreement No. 102192.
The Cornell-BNL ERL Test Accelerator (CBETA) is the first superconducting multi-turn ERL that has been commissioned at Cornell University in a low current mode. In this paper, we first discuss a new model of beam loading which is valid for the low injection energies used in CBETA. Using this model, we explore the effect of bunch patterns, beam turn-on, and turn-off transients on the fundamental mode of the 7-cell SRF cavities used in the main linac. In particular, we examine the operational constraints on the rf system at the design current of 40 mA.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB322

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paper received ※ 20 May 2021 paper accepted ※ 29 July 2021 issue date ※ 16 August 2021

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