IBIC2018 - List of Keywords (cavity)

Paper	Title	Other Keywords	Page
MOOB03	Upgrade and Status of Standard Diagnostic-Systems at FLASH and FLASHForward	FEL, electron, diagnostics, electronics	13
	N. Baboi, H.T. Duhme, O. Hensler, G. Kube, T. Lensch, D. Lipka, B. Lorbeer, Re. Neumann, P.A. Smirnov, T. Wamsat, M. Werner DESY, Hamburg, Germany
	Electron beam diagnostics plays a crucial role in the precise and reliable generation of ultra-short high bril-liance XUV and soft X-ray beams at the Free Electron Laser in Hamburg (FLASH). Most diagnostic systems monitor each of up to typically 600 bunches per beam, with a frequency of up to 1 MHz, a typical charge be-tween 0.1 and 1 nC and an energy of 350 to 1250 MeV. The diagnostic monitors have recently undergone a major upgrade. This process started several years ago with the development of monitors fulfilling the requirements of the European XFEL and of the FLASH2 undulator beamline and it continued with their installation and commissioning. Later they have been further improved and an upgrade was made in the old part of the linac. Also the FLASHForward plasma-wakefield acceleration experiment has been installed in the third beamline. This paper will give an overview of the upgrade of the BPM, Toroid and BLM systems, pointing out to their improved performance. Other systems underwent a partial upgrade, mainly by having their VME-based ADCs replaced with MTCA type. The overall status of the diagnostic will be reviewed.
	Slides MOOB03 [2.728 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-MOOB03
About •	paper received ※ 05 September 2018 paper accepted ※ 12 September 2018 issue date ※ 29 January 2019
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MOPB10	A Study on the Influence of Bunch Longitudinal Distribution on the Cavity Bunch Length Measurement	electron, FEL, quadrupole, flattop	97
	Q. Wang, Q. Luo, B.G. Sun, F.F. Wu USTC/NSRL, Hefei, Anhui, People’s Republic of China
	Funding: Supported by National Key R&D Program of China (2016YFA0401900, 2016YFA0401903), NSFC (11375178, 11575181) and the Fundamental Research Funds for the Central Universities (WK2310000046) Cavity bunch length measurement is used to obtain the bunch length depending on the eigenmodes exciting in-side the cavity. For today’s FELs, the longitudinal distribution of particles in electron bunch (bunch shape) may be non-Gaussian, sometimes very novel. In this paper, the influence of bunch shape on the cavity bunch length measurement is analyzed, and some examples are given to verify the theoretical results. The analysis shows that the longitudinal distribution of particles in electron bunch has little influence on the cavity bunch length measure-ment when the bunch length is less than 1 ps and the eigenmodes used in measurement are below 10GHz.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-MOPB10
About •	paper received ※ 09 September 2018 paper accepted ※ 10 September 2018 issue date ※ 29 January 2019
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MOPB13	Active Magnetic Field Compensation System for SRF Cavities	SRF, controls, electron, electronics	101
	L.H. Ding Laboratory GREYC, Caen, France J. Liang, H. Liu, Z.P. Xie Hohai University, Nanjing, People’s Republic of China Z.P. Xie IMP/CAS, Lanzhou, People’s Republic of China
	Abstract: Superconducting Radio Frequency (SRF) cavities are becoming popular in modern particle accelerators. When the SRF cavity is transitioning from the non-conducting to the Superconducting state at the critical temperature (Tc), the ambient magnetic field can be trapped. This trapped flux may lead to an increase in the surface resistance of the cavity wall, which can reduce the Q-factor and efficiency of the cavity. In order to increase the Q-factor, it is important to lower the surface resistance by reducing the amount of magnetic flux trapped in the cavity wall to sub 10mG range during the Tc transition. In this paper, we present a 3-axis automatic active magnetic field compensation system that is capable of reducing the earth magnetic field and any local disturbance field. Design techniques are described to enhance the system stability while utilizing the flexibility of embedded electronics. This paper describes the system implementation and concludes with initial results of tests. Experimental results demonstrate that the proposed magnetic field compensation system can reduce the earth magnetic field to around 2.5 mG even without shielding.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-MOPB13
About •	paper received ※ 05 September 2018 paper accepted ※ 12 September 2018 issue date ※ 29 January 2019
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MOPB17	Using a TE011 Cavity as a Magnetic Momentum Monitor	electron, GUI, impedance, coupling	111
	J. Guo, J. Henry, M. Poelker, R.A. Rimmer, R. Suleiman, H. Wang JLab, Newport News, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC with Laboratory Directed Research and Development funding, under U.S. DOE Contract No. DE-AC05-06OR23177. The Jefferson Lab Electron-Ion Collider (JLEIC) design relies on cooling of the ion beam with bunched electron beam constrained in a pair of long solenoids. The high current cooling electron beam needs to be generated in a magnetized electron source, and the beam’s magnetization needs to be maintained during the acceleration and transport to the cooling channel. A non-invasive real time monitoring system is highly desired to quantify electron beam magnetization. The authors propose to use a passive copper RF cavity in TE011 mode as such a monitor. In this paper, we present the mechanism and scaling law of this device, as well as the design and preliminary test results of the prototype cavity.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-MOPB17
About •	paper received ※ 11 September 2018 paper accepted ※ 12 September 2018 issue date ※ 29 January 2019
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MOPC17	On-line Crosstalk Measurement and Compensation Algorithm Study of SXFEL Digital BPM System	FEL, experiment, undulator, background	150
	F.Z. Chen, L.W. Lai, Y.B. Leng, T. Wu, L.Y. Yu SSRF, Shanghai, People’s Republic of China J. Chen, R.X. Yuan SINAP, Shanghai, People’s Republic of China
	Shanghai soft X-ray Free Electron Laser (SXFEL) has acquired the custom designed Digital BPM processor used for signal processing of cavity BPMs and stripline BPMs. In order to realize monitor the beam position accurately, it has high demand for DBPM system performance. Considering the crosstalk may introduce distortion and influence beam position resolution, it is important to analyze and compensate the crosstalk to improve the resolution. We choose the CBPM signal to study the crosstalk for its narrowband and sensitive for phase. The main experiment concept is successive accessing four channels to form a signal transfer matrix, which including amplitude frequency response and phase response information. And the compensation algorithm is acquire four channel readouts, then using the signal transfer matrix to reverse the true signal to ensure the accurate beam position measurement. This concept has already been tested at SXFEL and hopeful to compensate the crosstalk sufficiently.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-MOPC17
About •	paper received ※ 05 September 2018 paper accepted ※ 13 September 2018 issue date ※ 29 January 2019
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TUPA08	Arc Discharge Detectors for the CiADS Superconducting RF Cavities	detector, hardware, software, electron	228
	Z.P. Xie, Y.K. Ding, J. Liang, H. Liu Hohai University, Nanjing, People’s Republic of China Y. He, Y.M. Li IMP/CAS, Lanzhou, People’s Republic of China
	Funding: Work supported by the National Natural Science Foundation of China (Grant No.11505255, No.91026001) and the Fundamental Research Funds for the Chinese Central Universities(2015B29714) Arc discharge due to the electron emission is one of the key issues in the CW superconducting RF(SRF) for the CiADS particle accelerator. Arc discharges can deteriorate the SRF cavities and damage the facility. Monitoring arc discharges is important for the purpose of machine protection. In this paper, an arc discharge detector has been designed to provide fast response upon events of arc discharge using open-source hardware and LabVIEW software. Electronic design techniques are described to enhance the system stability while utilizing the flexibility of embedded electronics. The proposed detector system gives about 700 ns of response time and it employs a LabVIEW based graphic user interface. The system has the capability of detecting the instantaneous arc discharge events in real time. Timestamps of the event will be recorded to assist beam diagnostics. This paper describes the hardware/software implementation and concludes with initial results of tests at CiADS.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-TUPA08
About •	paper received ※ 04 September 2018 paper accepted ※ 11 September 2018 issue date ※ 29 January 2019
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TUPB05	Design of a Cavity Beam Position Monitor for the ARES Accelerator at DESY	dipole, resonance, FEL, impedance	269
	D. Lipka, M. Dohlus, M. Marx, S. Vilcins, M. Werner DESY, Hamburg, Germany
	The SINBAD facility (Short and INnovative Bunches and Accelerators at DESY) is foreseen to host various experiments in the field of production of ultra-short electron bunches and novel high gradient acceleration techniques. The SINBAD linac, also called ARES (Accelerator Research Experiment at SINBAD), will be a conventional S-band linear RF accelerator allowing the production of low charge (within a range between 0.5 pC and 1000 pC) ultra-short electron bunches. To detect the low charge bunches a cavity beam position monitor is designed based on the experience from the EU-XFEL. It will consist of a stainless steel body with low Q factor of 70, a resonance frequency of 3.3 GHz and a relative wide gap of 15 mm to reach a high peak position sensitivity of 4.25 V/(nC mm). The design considerations and simulation results will be presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-TUPB05
About •	paper received ※ 04 September 2018 paper accepted ※ 13 September 2018 issue date ※ 29 January 2019
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TUPB07	Stability Study of Beam Position Measurement Based on Higher Order Mode Signals at FLASH	HOM, dipole, electron, higher-order-mode	273
	J.H. Wei USTC/NSRL, Hefei, Anhui, People’s Republic of China N. Baboi DESY, Hamburg, Germany L. Shi PSI, Villigen PSI, Switzerland
	FLASH is a free-electron laser driven by a supercon-ducting linac at DESY in Hamburg. It generates high-brilliance XUV and soft X-ray pulses by SASE (Self Amplified Spontaneous Emission). Many accelerating cavities are equipped with HOMBPMs (Higher Order Mode based Beam Position Monitors) to align the beam and monitor the transverse beam position. However, these lose their position prediction ability over time. In this paper, we applied an efficient measurement and signal analysis with various data process methods including PLS (Partial Least Square) and SVD (Singular Value Decomposition) to determine the transverse beam position. By fitting the HOM signals with a genetic algorithm, we implemented a new HOMBPM calibration procedure and obtained reliable beam prediction positions over a long time. A stable RMS error of about 0.2 mm by using the spectra of signals and 0.15 mm by using the new method over two months has been observed.
	Poster TUPB07 [1.816 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-TUPB07
About •	paper received ※ 05 September 2018 paper accepted ※ 13 September 2018 issue date ※ 29 January 2019
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TUPB09	The Evaluation of Beam Inclination Angle on the Cavity BPM Position Measurement	FEL, simulation, experiment, electron	278
	J. Chen, L.W. Lai, Y.B. Leng, L.Y. Yu, R.X. Yuan SINAP, Shanghai, People’s Republic of China
	Cavity beam position monitor (CBPM) is widely used to measure the transverse position in free-electron laser (FEL) and international linear collider (ILC) facilities due to the characteristic of high sensitive. In order to study the limiting factors of the position resolution of cavity BPM, the influence of beam inclination angle on the measure-ment of CBPM position and the direction of beam deflec-tion was analyzed. The simulation results show that the beam inclination angle is an important factor limiting the superiority of CBPM with extremely high position resolu-tion. The relative beam experiments to change the relative inclination angle between the cavity and the electron beam based on a 4-dimension moveable platform were performed in Shanghai Soft X-ray FEL (SXFEL) facility, the experiment results will also be mentioned as well.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-TUPB09
About •	paper received ※ 05 September 2018 paper accepted ※ 11 September 2018 issue date ※ 29 January 2019
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WEOA04	The Application of Beam Arrival Time Measurement at SXFEL	FEL, experiment, electron, laser	342
	S.S. Cao, J. Chen, Y.B. Leng, R.X. Yuan SINAP, Shanghai, People’s Republic of China
	Shanghai soft X-ray free electron laser (SXFEL) is able to generate high brightness and ultra-short light pulses. The generation of the light sources relies on the synchronization between seeded laser and electron bunch. Beam arrival time play an important role to keep the synchronization. For the SXFEL, a beam arrival time resolution under 100 fs is required. In this paper, the application of beam arrival time measurement scheme on SXFEL has been presented. The whole BAM system consists of four parts: beam arrival time monitor, electronic front-end, signal acquisition system, and high-level signal processing and presentation. Currently, four sets of beam arrival time monitors (BAMs) have been installed in the SXFEL and distributed in four different locations. The relevant beam arrival time experiment and beam flight time experiment based on the dual-cavities mixing method have also been performed so as to evaluate and analyze the beam status.
	Slides WEOA04 [4.588 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-WEOA04
About •	paper received ※ 05 September 2018 paper accepted ※ 11 September 2018 issue date ※ 29 January 2019
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WEPA02	Recent Progress of Bunch Resolved Beam Diagnostics for BESSY VSR	diagnostics, photon, beam-diagnostic, storage-ring	379
	J.G. Hwang, T. Atkinson, P. Goslawski, A. Jankowiak, M. Koopmans, T. Mertens, M. Ries, A. Schälicke, G. Schiwietz HZB, Berlin, Germany
	BESSY VSR is an upgrade project of the existing storage ring BESSY II to create long and short photon pulses simultaneously for all beam lines by installing additional superconducting cavities with harmonic frequencies of 1.5 GHz and 1.75 GHz. The storage-ring operation will be influenced by a transient beam-loading effect of all cavities and by the complex filling pattern due to the disparity in the current of long and short bunches. This, in turn, could introduce a variation of beam trajectory, transverse profile, and length for the different bunches. This stimulates the development of bunch-resolved monitors for bunch length, beam size, filling pattern and beam trajectory displacement. In this paper, we show new developments of crucial beam diagnostics including measurements of the bunch-resolved temporal profile with a resolution of less than 1 ps FWHM and bunch-resolved profile with a resolution of less than 10 um rms. The upgrade of the booster beam-diagnostics will be discussed as well.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-WEPA02
About •	paper received ※ 04 September 2018 paper accepted ※ 13 September 2018 issue date ※ 29 January 2019
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WEPA09	Long Term Beam Phase Monitoring Based on HOM Signals in SC Cavities at FLASH	HOM, controls, electron, FEL	388
	J.H. Wei USTC/NSRL, Hefei, Anhui, People’s Republic of China N. Baboi DESY, Hamburg, Germany L. Shi PSI, Villigen PSI, Switzerland
	The accelerating RF fields in superconducting cavities must be controlled precisely in FEL (Free Electron Laser) facilities to avoid beam energy spread and arrival time jitter. Otherwise the beam quality is degraded. The LLRF (Low Level Radio Frequency) system controls the RF field and provides a highly stable RF reference. A new type of beam phase determination technique based on beam-excited HOMs (Higher Order Modes) in cavities has been implemented. The two special couplers installed at both ends of each cavity, pick up the signals containing both the leakage of the accelerating field and the HOM signals. Therefore the signals can be used to calculate the beam phase directly with respect to the RF phase. We analysed the factors which may affect the result of the beam phase on a long-term based on an experimental platform at FLASH. Some phase drifts between the HOM-BPhM (Beam Phase Monitor) and the LLRF system phase measurement were observed and the reason will be further studied.
	Poster WEPA09 [1.720 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-WEPA09
About •	paper received ※ 05 September 2018 paper accepted ※ 13 September 2018 issue date ※ 29 January 2019
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WEPA19	Results from the CERN LINAC4 Longitudinal Bunch Shape Monitor	linac, MMI, electron, emittance	415
	J. Tan, G. Bellodi CERN, Geneva, Switzerland A. Feschenko, S.A. Gavrilov RAS/INR, Moscow, Russia
	The CERN Linac4 has been successfully commissioned to its nominal energy and will provide 160 MeV H⁻ ions for charge-exchange injection into the Proton Synchrotron Booster (PSB) from 2020. A complete set of beam diagnostic devices has been installed along the accelerating structures and the transfer line for safe and efficient operation. This includes two longitudinal Bunch Shape Monitors (BSM) developed by the Institute for Nuclear Research (INR, Moscow). Setting-up the RF cavities of Linac4 involves beam loading observations, time-of-flight measurements and reconstruction of the longitudinal emittance from phase profile measurements. In this paper the BSM is presented along with some results obtained during accelerator commissioning, including a comparison with phase measurements performed using the Beam Position Monitor system.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-WEPA19
About •	paper received ※ 07 September 2018 paper accepted ※ 12 September 2018 issue date ※ 29 January 2019
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WEPB03	First Prototype of a Coronagraph-based Halo Monitor for BERLinPro	diagnostics, SRF, operation, linac	434
	J.G. Hwang, J. Kuszynski HZB, Berlin, Germany
	Since particle losses by beam halo induced by space charge force and scattering of trapped ions are critical issues for superconducting-linac based high power machines such as BERLinPro, a halo monitor is demanded to monitor and control particle distribution at the level of 10^-4 ~ 10^-5 of the core intensity. A coronagraph-based halo monitor was adopted and the first prototype has been designed as a demonstrator system aimed at resolving a halo-core contrast in the 10^-3 to 10^-4 range. This monitor was tested at BESSY II with various operation modes such as Transverse Resonance Island Buckets (TRIBs) and Pulse-Picking by Resonant Excitation (PPRE). We show our design parameters, experimental criterion, and experimental results.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-WEPB03
About •	paper received ※ 04 September 2018 paper accepted ※ 12 September 2018 issue date ※ 29 January 2019
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WEPB21	Transverse Beam Emittance Measurements with Multi-Slit and Moving-Slit Devices for LEReC	emittance, electron, optics, solenoid	486
	C. Liu, A.V. Fedotov, D.M. Gassner, X. Gu, D. Kayran, J. Kewisch, T.A. Miller, M.G. Minty, V. Ptitsyn, S. Seletskiy, A. Sukhanov, D. Weiss BNL, Upton, Long Island, New York, USA A. Fuchs Ward Melville High School, Setauket- East Setauket, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. Low Energy RHIC electron cooling (LEReC) [1] is the first bunched electron cooler, designed to cool low energy ion beams at RHIC. The beam quality, including the transverse beam emittance, is critical for the success of cooling. The transverse electron beam emittance was characterized with a multi-slit and moving-slit device at various locations in the beamline. The beam emittance measurement and analysis are presented in this report.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-WEPB21
About •	paper received ※ 01 September 2018 paper accepted ※ 12 September 2018 issue date ※ 29 January 2019
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Paper

Title

Other Keywords

Page

MOOB03

Upgrade and Status of Standard Diagnostic-Systems at FLASH and FLASHForward

FEL, electron, diagnostics, electronics

13

N. Baboi, H.T. Duhme, O. Hensler, G. Kube, T. Lensch, D. Lipka, B. Lorbeer, Re. Neumann, P.A. Smirnov, T. Wamsat, M. Werner
DESY, Hamburg, Germany

Electron beam diagnostics plays a crucial role in the precise and reliable generation of ultra-short high bril-liance XUV and soft X-ray beams at the Free Electron Laser in Hamburg (FLASH). Most diagnostic systems monitor each of up to typically 600 bunches per beam, with a frequency of up to 1 MHz, a typical charge be-tween 0.1 and 1 nC and an energy of 350 to 1250 MeV. The diagnostic monitors have recently undergone a major upgrade. This process started several years ago with the development of monitors fulfilling the requirements of the European XFEL and of the FLASH2 undulator beamline and it continued with their installation and commissioning. Later they have been further improved and an upgrade was made in the old part of the linac. Also the FLASHForward plasma-wakefield acceleration experiment has been installed in the third beamline. This paper will give an overview of the upgrade of the BPM, Toroid and BLM systems, pointing out to their improved performance. Other systems underwent a partial upgrade, mainly by having their VME-based ADCs replaced with MTCA type. The overall status of the diagnostic will be reviewed.

Slides MOOB03 [2.728 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-MOOB03

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paper received ※ 05 September 2018 paper accepted ※ 12 September 2018 issue date ※ 29 January 2019

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MOPB10

A Study on the Influence of Bunch Longitudinal Distribution on the Cavity Bunch Length Measurement

electron, FEL, quadrupole, flattop

97

Q. Wang, Q. Luo, B.G. Sun, F.F. Wu
USTC/NSRL, Hefei, Anhui, People’s Republic of China

Funding: Supported by National Key R&D Program of China (2016YFA0401900, 2016YFA0401903), NSFC (11375178, 11575181) and the Fundamental Research Funds for the Central Universities (WK2310000046)
Cavity bunch length measurement is used to obtain the bunch length depending on the eigenmodes exciting in-side the cavity. For today’s FELs, the longitudinal distribution of particles in electron bunch (bunch shape) may be non-Gaussian, sometimes very novel. In this paper, the influence of bunch shape on the cavity bunch length measurement is analyzed, and some examples are given to verify the theoretical results. The analysis shows that the longitudinal distribution of particles in electron bunch has little influence on the cavity bunch length measure-ment when the bunch length is less than 1 ps and the eigenmodes used in measurement are below 10GHz.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-MOPB10

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paper received ※ 09 September 2018 paper accepted ※ 10 September 2018 issue date ※ 29 January 2019

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MOPB13

Active Magnetic Field Compensation System for SRF Cavities

SRF, controls, electron, electronics

101

L.H. Ding
Laboratory GREYC, Caen, France
J. Liang, H. Liu, Z.P. Xie
Hohai University, Nanjing, People’s Republic of China
Z.P. Xie
IMP/CAS, Lanzhou, People’s Republic of China

Abstract: Superconducting Radio Frequency (SRF) cavities are becoming popular in modern particle accelerators. When the SRF cavity is transitioning from the non-conducting to the Superconducting state at the critical temperature (Tc), the ambient magnetic field can be trapped. This trapped flux may lead to an increase in the surface resistance of the cavity wall, which can reduce the Q-factor and efficiency of the cavity. In order to increase the Q-factor, it is important to lower the surface resistance by reducing the amount of magnetic flux trapped in the cavity wall to sub 10mG range during the Tc transition. In this paper, we present a 3-axis automatic active magnetic field compensation system that is capable of reducing the earth magnetic field and any local disturbance field. Design techniques are described to enhance the system stability while utilizing the flexibility of embedded electronics. This paper describes the system implementation and concludes with initial results of tests. Experimental results demonstrate that the proposed magnetic field compensation system can reduce the earth magnetic field to around 2.5 mG even without shielding.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-MOPB13

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paper received ※ 05 September 2018 paper accepted ※ 12 September 2018 issue date ※ 29 January 2019

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MOPB17

Using a TE011 Cavity as a Magnetic Momentum Monitor

electron, GUI, impedance, coupling

111

J. Guo, J. Henry, M. Poelker, R.A. Rimmer, R. Suleiman, H. Wang
JLab, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC with Laboratory Directed Research and Development funding, under U.S. DOE Contract No. DE-AC05-06OR23177.
The Jefferson Lab Electron-Ion Collider (JLEIC) design relies on cooling of the ion beam with bunched electron beam constrained in a pair of long solenoids. The high current cooling electron beam needs to be generated in a magnetized electron source, and the beam’s magnetization needs to be maintained during the acceleration and transport to the cooling channel. A non-invasive real time monitoring system is highly desired to quantify electron beam magnetization. The authors propose to use a passive copper RF cavity in TE011 mode as such a monitor. In this paper, we present the mechanism and scaling law of this device, as well as the design and preliminary test results of the prototype cavity.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-MOPB17

About •

paper received ※ 11 September 2018 paper accepted ※ 12 September 2018 issue date ※ 29 January 2019

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MOPC17

On-line Crosstalk Measurement and Compensation Algorithm Study of SXFEL Digital BPM System

FEL, experiment, undulator, background

150

F.Z. Chen, L.W. Lai, Y.B. Leng, T. Wu, L.Y. Yu
SSRF, Shanghai, People’s Republic of China
J. Chen, R.X. Yuan
SINAP, Shanghai, People’s Republic of China

Shanghai soft X-ray Free Electron Laser (SXFEL) has acquired the custom designed Digital BPM processor used for signal processing of cavity BPMs and stripline BPMs. In order to realize monitor the beam position accurately, it has high demand for DBPM system performance. Considering the crosstalk may introduce distortion and influence beam position resolution, it is important to analyze and compensate the crosstalk to improve the resolution. We choose the CBPM signal to study the crosstalk for its narrowband and sensitive for phase. The main experiment concept is successive accessing four channels to form a signal transfer matrix, which including amplitude frequency response and phase response information. And the compensation algorithm is acquire four channel readouts, then using the signal transfer matrix to reverse the true signal to ensure the accurate beam position measurement. This concept has already been tested at SXFEL and hopeful to compensate the crosstalk sufficiently.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-MOPC17

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paper received ※ 05 September 2018 paper accepted ※ 13 September 2018 issue date ※ 29 January 2019

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TUPA08

Arc Discharge Detectors for the CiADS Superconducting RF Cavities

detector, hardware, software, electron

228

Z.P. Xie, Y.K. Ding, J. Liang, H. Liu
Hohai University, Nanjing, People’s Republic of China
Y. He, Y.M. Li
IMP/CAS, Lanzhou, People’s Republic of China

Funding: Work supported by the National Natural Science Foundation of China (Grant No.11505255, No.91026001) and the Fundamental Research Funds for the Chinese Central Universities(2015B29714)
Arc discharge due to the electron emission is one of the key issues in the CW superconducting RF(SRF) for the CiADS particle accelerator. Arc discharges can deteriorate the SRF cavities and damage the facility. Monitoring arc discharges is important for the purpose of machine protection. In this paper, an arc discharge detector has been designed to provide fast response upon events of arc discharge using open-source hardware and LabVIEW software. Electronic design techniques are described to enhance the system stability while utilizing the flexibility of embedded electronics. The proposed detector system gives about 700 ns of response time and it employs a LabVIEW based graphic user interface. The system has the capability of detecting the instantaneous arc discharge events in real time. Timestamps of the event will be recorded to assist beam diagnostics. This paper describes the hardware/software implementation and concludes with initial results of tests at CiADS.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-TUPA08

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paper received ※ 04 September 2018 paper accepted ※ 11 September 2018 issue date ※ 29 January 2019

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TUPB05

Design of a Cavity Beam Position Monitor for the ARES Accelerator at DESY

dipole, resonance, FEL, impedance

269

D. Lipka, M. Dohlus, M. Marx, S. Vilcins, M. Werner
DESY, Hamburg, Germany

The SINBAD facility (Short and INnovative Bunches and Accelerators at DESY) is foreseen to host various experiments in the field of production of ultra-short electron bunches and novel high gradient acceleration techniques. The SINBAD linac, also called ARES (Accelerator Research Experiment at SINBAD), will be a conventional S-band linear RF accelerator allowing the production of low charge (within a range between 0.5 pC and 1000 pC) ultra-short electron bunches. To detect the low charge bunches a cavity beam position monitor is designed based on the experience from the EU-XFEL. It will consist of a stainless steel body with low Q factor of 70, a resonance frequency of 3.3 GHz and a relative wide gap of 15 mm to reach a high peak position sensitivity of 4.25 V/(nC mm). The design considerations and simulation results will be presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-TUPB05

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paper received ※ 04 September 2018 paper accepted ※ 13 September 2018 issue date ※ 29 January 2019

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TUPB07

Stability Study of Beam Position Measurement Based on Higher Order Mode Signals at FLASH

HOM, dipole, electron, higher-order-mode

273

J.H. Wei
USTC/NSRL, Hefei, Anhui, People’s Republic of China
N. Baboi
DESY, Hamburg, Germany
L. Shi
PSI, Villigen PSI, Switzerland

FLASH is a free-electron laser driven by a supercon-ducting linac at DESY in Hamburg. It generates high-brilliance XUV and soft X-ray pulses by SASE (Self Amplified Spontaneous Emission). Many accelerating cavities are equipped with HOMBPMs (Higher Order Mode based Beam Position Monitors) to align the beam and monitor the transverse beam position. However, these lose their position prediction ability over time. In this paper, we applied an efficient measurement and signal analysis with various data process methods including PLS (Partial Least Square) and SVD (Singular Value Decomposition) to determine the transverse beam position. By fitting the HOM signals with a genetic algorithm, we implemented a new HOMBPM calibration procedure and obtained reliable beam prediction positions over a long time. A stable RMS error of about 0.2 mm by using the spectra of signals and 0.15 mm by using the new method over two months has been observed.

Poster TUPB07 [1.816 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-TUPB07

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paper received ※ 05 September 2018 paper accepted ※ 13 September 2018 issue date ※ 29 January 2019

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TUPB09

The Evaluation of Beam Inclination Angle on the Cavity BPM Position Measurement

FEL, simulation, experiment, electron

278

J. Chen, L.W. Lai, Y.B. Leng, L.Y. Yu, R.X. Yuan
SINAP, Shanghai, People’s Republic of China

Cavity beam position monitor (CBPM) is widely used to measure the transverse position in free-electron laser (FEL) and international linear collider (ILC) facilities due to the characteristic of high sensitive. In order to study the limiting factors of the position resolution of cavity BPM, the influence of beam inclination angle on the measure-ment of CBPM position and the direction of beam deflec-tion was analyzed. The simulation results show that the beam inclination angle is an important factor limiting the superiority of CBPM with extremely high position resolu-tion. The relative beam experiments to change the relative inclination angle between the cavity and the electron beam based on a 4-dimension moveable platform were performed in Shanghai Soft X-ray FEL (SXFEL) facility, the experiment results will also be mentioned as well.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-TUPB09

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paper received ※ 05 September 2018 paper accepted ※ 11 September 2018 issue date ※ 29 January 2019

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WEOA04

The Application of Beam Arrival Time Measurement at SXFEL

FEL, experiment, electron, laser

342

S.S. Cao, J. Chen, Y.B. Leng, R.X. Yuan
SINAP, Shanghai, People’s Republic of China

Shanghai soft X-ray free electron laser (SXFEL) is able to generate high brightness and ultra-short light pulses. The generation of the light sources relies on the synchronization between seeded laser and electron bunch. Beam arrival time play an important role to keep the synchronization. For the SXFEL, a beam arrival time resolution under 100 fs is required. In this paper, the application of beam arrival time measurement scheme on SXFEL has been presented. The whole BAM system consists of four parts: beam arrival time monitor, electronic front-end, signal acquisition system, and high-level signal processing and presentation. Currently, four sets of beam arrival time monitors (BAMs) have been installed in the SXFEL and distributed in four different locations. The relevant beam arrival time experiment and beam flight time experiment based on the dual-cavities mixing method have also been performed so as to evaluate and analyze the beam status.

Slides WEOA04 [4.588 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-WEOA04

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paper received ※ 05 September 2018 paper accepted ※ 11 September 2018 issue date ※ 29 January 2019

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WEPA02

Recent Progress of Bunch Resolved Beam Diagnostics for BESSY VSR

diagnostics, photon, beam-diagnostic, storage-ring

379

J.G. Hwang, T. Atkinson, P. Goslawski, A. Jankowiak, M. Koopmans, T. Mertens, M. Ries, A. Schälicke, G. Schiwietz
HZB, Berlin, Germany

BESSY VSR is an upgrade project of the existing storage ring BESSY II to create long and short photon pulses simultaneously for all beam lines by installing additional superconducting cavities with harmonic frequencies of 1.5 GHz and 1.75 GHz. The storage-ring operation will be influenced by a transient beam-loading effect of all cavities and by the complex filling pattern due to the disparity in the current of long and short bunches. This, in turn, could introduce a variation of beam trajectory, transverse profile, and length for the different bunches. This stimulates the development of bunch-resolved monitors for bunch length, beam size, filling pattern and beam trajectory displacement. In this paper, we show new developments of crucial beam diagnostics including measurements of the bunch-resolved temporal profile with a resolution of less than 1 ps FWHM and bunch-resolved profile with a resolution of less than 10 um rms. The upgrade of the booster beam-diagnostics will be discussed as well.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-WEPA02

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paper received ※ 04 September 2018 paper accepted ※ 13 September 2018 issue date ※ 29 January 2019

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WEPA09

Long Term Beam Phase Monitoring Based on HOM Signals in SC Cavities at FLASH

HOM, controls, electron, FEL

388

J.H. Wei
USTC/NSRL, Hefei, Anhui, People’s Republic of China
N. Baboi
DESY, Hamburg, Germany
L. Shi
PSI, Villigen PSI, Switzerland

The accelerating RF fields in superconducting cavities must be controlled precisely in FEL (Free Electron Laser) facilities to avoid beam energy spread and arrival time jitter. Otherwise the beam quality is degraded. The LLRF (Low Level Radio Frequency) system controls the RF field and provides a highly stable RF reference. A new type of beam phase determination technique based on beam-excited HOMs (Higher Order Modes) in cavities has been implemented. The two special couplers installed at both ends of each cavity, pick up the signals containing both the leakage of the accelerating field and the HOM signals. Therefore the signals can be used to calculate the beam phase directly with respect to the RF phase. We analysed the factors which may affect the result of the beam phase on a long-term based on an experimental platform at FLASH. Some phase drifts between the HOM-BPhM (Beam Phase Monitor) and the LLRF system phase measurement were observed and the reason will be further studied.

Poster WEPA09 [1.720 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-WEPA09

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paper received ※ 05 September 2018 paper accepted ※ 13 September 2018 issue date ※ 29 January 2019

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WEPA19

Results from the CERN LINAC4 Longitudinal Bunch Shape Monitor

linac, MMI, electron, emittance

415

J. Tan, G. Bellodi
CERN, Geneva, Switzerland
A. Feschenko, S.A. Gavrilov
RAS/INR, Moscow, Russia

The CERN Linac4 has been successfully commissioned to its nominal energy and will provide 160 MeV H⁻ ions for charge-exchange injection into the Proton Synchrotron Booster (PSB) from 2020. A complete set of beam diagnostic devices has been installed along the accelerating structures and the transfer line for safe and efficient operation. This includes two longitudinal Bunch Shape Monitors (BSM) developed by the Institute for Nuclear Research (INR, Moscow). Setting-up the RF cavities of Linac4 involves beam loading observations, time-of-flight measurements and reconstruction of the longitudinal emittance from phase profile measurements. In this paper the BSM is presented along with some results obtained during accelerator commissioning, including a comparison with phase measurements performed using the Beam Position Monitor system.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-WEPA19

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paper received ※ 07 September 2018 paper accepted ※ 12 September 2018 issue date ※ 29 January 2019

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WEPB03

First Prototype of a Coronagraph-based Halo Monitor for BERLinPro

diagnostics, SRF, operation, linac

434

J.G. Hwang, J. Kuszynski
HZB, Berlin, Germany

Since particle losses by beam halo induced by space charge force and scattering of trapped ions are critical issues for superconducting-linac based high power machines such as BERLinPro, a halo monitor is demanded to monitor and control particle distribution at the level of 10^-4 ~ 10^-5 of the core intensity. A coronagraph-based halo monitor was adopted and the first prototype has been designed as a demonstrator system aimed at resolving a halo-core contrast in the 10^-3 to 10^-4 range. This monitor was tested at BESSY II with various operation modes such as Transverse Resonance Island Buckets (TRIBs) and Pulse-Picking by Resonant Excitation (PPRE). We show our design parameters, experimental criterion, and experimental results.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-WEPB03

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paper received ※ 04 September 2018 paper accepted ※ 12 September 2018 issue date ※ 29 January 2019

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WEPB21

Transverse Beam Emittance Measurements with Multi-Slit and Moving-Slit Devices for LEReC

emittance, electron, optics, solenoid

486

C. Liu, A.V. Fedotov, D.M. Gassner, X. Gu, D. Kayran, J. Kewisch, T.A. Miller, M.G. Minty, V. Ptitsyn, S. Seletskiy, A. Sukhanov, D. Weiss
BNL, Upton, Long Island, New York, USA
A. Fuchs
Ward Melville High School, Setauket- East Setauket, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Low Energy RHIC electron cooling (LEReC) [1] is the first bunched electron cooler, designed to cool low energy ion beams at RHIC. The beam quality, including the transverse beam emittance, is critical for the success of cooling. The transverse electron beam emittance was characterized with a multi-slit and moving-slit device at various locations in the beamline. The beam emittance measurement and analysis are presented in this report.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-WEPB21

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paper received ※ 01 September 2018 paper accepted ※ 12 September 2018 issue date ※ 29 January 2019

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