IBIC2018 - Classification: 5. Longitudinal diagnostic and synchronization

Paper	Title	Page
WEOA01	Femtosecond Synchronization of PAL-XFEL
	C. Kim, H.-S. Kang, I.S. Ko, C.-K. Min PAL, Pohang, Kyungbuk, Republic of Korea
	The PAL-XFEL achieved a 20 fs jitter in the bunch arrival time at the end of undulators and its pump-probe system, which is extremely useful for maintaining a high stability of machine and time-resolved experiments with high time resolution. A low phase noise timing system and high stability high power RF system enable this low jitter. The measurement result shows 10 fs jitter of bunch arrival time at the injector and it increased ~ 20 fs due to the bunch energy variation. The possibility of improving the final jitter is described based on the optimization of bunch compressors and a longitudinal feedback.
	Slides WEOA01 [9.603 MB]
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WEOA02	Optical Investigation to Minimize the Electron Bunch Arrival-time Jitter Between Femtosecond Laser Pulses and Electron Bunches for Laser-Driven Plasma Wakefield Accelerators	332
	S. Mattiello, A. Penirschke THM, Friedberg, Germany H. Schlarb DESY, Hamburg, Germany
	Funding: The work of S. Mattiello is supported by the German Federal Ministry of Education and Research (BMBF) within the Project ’ MAKE-PWA. In a laser driven plasma based particle accelerators a stable synchronization of the electron bunch and of the plasma wakefield in the range of less than 2 fs is necessary in order to optimize the acceleration. For this purpose we are developing a new shot to shot feedback system with a time resolution of less than 1 fs. As a first step, stable THz pulses are generated by optical rectification of a fraction of the plasma generating high energy laser pulses in a nonlinear lithium niobate crystal. It is planed that the generated THz pulses will energy modulate the electron bunches shot to shot before the plasma to achieve the time resolution of 1 fs. In this contribution we systematically investigate the influence of the optical properties as well as the theoretical description of the THz generation on the conversion efficiency of the generation of short THz pulses in undepleted approximation. We compare different approximations for the modeling of the generation dynamics and of the dielectric function in order to investigate the importance of a detailed description of the optical properties. First results by considering intensity decreasing of the laser pump will be presented. *The feedback system will be tested at the Accelerator R&D facility SINBAD (Short Innovative Bunches and Accelerators at DESY).
	Slides WEOA02 [1.605 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-WEOA02
About •	paper received ※ 04 September 2018 paper accepted ※ 10 September 2018 issue date ※ 29 January 2019
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WEOA03	First Electro-Optical Bunch Length Measurements from the European XFEL	338
	B. Steffen, M.K. Czwalinna, C. Gerth, P. Peier DESY, Hamburg, Germany
	Three electro-optical bunch length detection systems based on spectral decoding have been installed and are being commissioned at the European XFEL. The systems are capable of recording individual longitudinal bunch profiles with sub-picosecond resolution at a bunch repetition rate 1.13 MHz. Bunch lengths and arrival times of entire bunch trains with single-bunch resolution have been measured as well as jitter and drifts for consecutive bunch trains. In this paper, we present first measurement results for the electro-optical detection system located after the second bunch compressor. A preliminary comparison with data from the bunch arrival-time monitor shows good agreement.
	Slides WEOA03 [4.496 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-WEOA03
About •	paper received ※ 05 September 2018 paper accepted ※ 12 September 2018 issue date ※ 29 January 2019
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WEOA04	The Application of Beam Arrival Time Measurement at SXFEL	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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WEPA01	A MicroTCA.4 Timing Receiver for the Sirius Timing System	375
	J.L. Brito Neto, G.B.M. Bruno, S.R. Marques, L.M. Russo, D.O. Tavares LNLS, Campinas, Brazil
	The AMC FMC carrier (AFC) is a MicroTCA.4 AMC board which has a very flexible clock circuit that enables any clock source to be connected to any clock input, including telecom clock, FMC clocks, programmable VCXO oscillator and FPGA. This paper presents the use of the AFC board as an event receiver connected to the Sirius timing system to provide low jitter synchronized clocks and triggers for Sirius BPM electronics and other devices.
	Poster WEPA01 [3.299 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-WEPA01
About •	paper received ※ 04 September 2018 paper accepted ※ 12 September 2018 issue date ※ 29 January 2019
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WEPA02	Recent Progress of Bunch Resolved Beam Diagnostics for BESSY VSR	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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WEPA06	Thermal Coefficient of Delay Measurement of the New Phase Stable Optical Fiber	383
	L. Liu, X. Ma, G. Pei IHEP, Beijing, People’s Republic of China
	The Thermal Coefficient of Delay (TCD) is an essen-tial parameter of optical fiber which determines a fiber’s phase transfer stability due to temperature variation. The TCD of a new phase stable single mode optical fiber (YPSOC) from Yangtze Optical Fibre and Cable Compa-ny (YOFC) is measured. The radio frequency (RF) signal is modulated to optical wave by a laser module which is transmitted through the 400-meter long YPSOC to be measured. The returned optical wave is demodulated to RF signal by the photodetector. A phase detector and a data acquisition module (DAQ) are used to acquire the phase difference between the forward and returned sig-nals. Two temperature-stabilized cabinets are designed to maintain and control the ambient temperature of the measurement system. The TCD of less than 10ps/km/K at room temperature is obtained. YPSOC and the meas-urement platform can be applied on signal transmission or measurement system that need to compensate the temperature drift.
	Poster WEPA06 [0.653 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-WEPA06
About •	paper received ※ 03 September 2018 paper accepted ※ 12 September 2018 issue date ※ 29 January 2019
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WEPA07	Beam Phase Measurement System in CSNS Linac	386
	P. Li, J. Peng IHEP CSNS, Guangdong Province, People’s Republic of China F. Li, T.G. Xu IHEP, Beijing, People’s Republic of China M. Meng DNSC, Dongguan, People’s Republic of China W. Peng CETC, Shushan, People’s Republic of China
	We developed beam phase measurement system ourselves in CSNS (China Spallation Neutron Source). The resolution of the system is less than 0.1° and the accuracy is less than 1°. It played a key role in CSNS Linac commissioning especially in RFQ and DTL commissioning. Further we measured the beam energy by TOF (Time of Flight) method base on this system. The energy accuracy is less than 0.1 MeV.
	Poster WEPA07 [1.070 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-WEPA07
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	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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WEPA12	Differential Evolution Genetic Algorithm for Beam Bunch Temporal Reconstruction	392
	D. Wu, T.H. He, C.L. Lao, P. Li, J. Liu, X. Luo, Q. Pan, L.J. Shan, X. Shen, J. Wang, D.X. Xiao, L.G. Yan, P. Zhang, K. Zhou CAEP/IAE, Mianyang, Sichuan, People’s Republic of China Y. Liu CAEP/IFP, Mainyang, Sichuan, People’s Republic of China
	Funding: Work supported by China National Natural Science Foundation of China with grant (11475159, 11505173, 11505174, 11575264, 11605190 and 11105019) Coherent radiation, such as coherent transition radiation, coherent diffraction radiation, coherent synchrotron radiation, etc, can be used to measure the longitudinal distribution of the electron beam bunch of any length, as long as the coherent radiation spectrum can be measured. In many cases, the Kramers-Krönig relationship is used to reconstruct the temporal distribution of the beam from the coherent radiation spectrum. However, the extrapolation of the low frequency will introduce the uncertainty of the reconstruction. In this paper, an algorithm of differential evolution (DE) for temporal reconstruction is discussed. The DE reconstruction works well for the complex and ultrashort distribution. It will be an effectIve tool to accurately measure the femtosecond bunch temporal structure.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-WEPA12
About •	paper received ※ 07 September 2018 paper accepted ※ 13 September 2018 issue date ※ 29 January 2019
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WEPA13	Electro-Optic Modulator Based Beam Arrival Time Monitor for SXFEL	396
	X.Q. Liu, L.F. Hua, L.W. Lai, Y.B. Leng, R.X. Yuan SINAP, Shanghai, People’s Republic of China N. Zhang SSRF, Shanghai, People’s Republic of China
	Beam arrival time monitor (BAM) is an important tool to investigate the temporal characteristic of elec-tron bunch in free electron laser (FEL) like Shanghai soft X-ray Free Electron Laser (SXFEL). Since the timing jitter of electron bunch will affect the FEL’s stability and the resolution of time-resolved experi-ment at FELs, it is necessary to precisely measure the electron bunch arrival time so as to reduce the timing jitter of the electron bunch with beam based feedback. The beam arrival time monitor based on electro-optic modulator (EOM) is already planned and will be de-veloped and tested at SXFEL in the next three years. Here the design and preliminary results of the EOM based beam arrival time monitor will be introduced in this paper.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-WEPA13
About •	paper received ※ 04 September 2018 paper accepted ※ 11 September 2018 issue date ※ 29 January 2019
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WEPA15	Development of BAM Electronics in PAL-XFEL	400
	D.C. Shin, J.H. Hong, H.-S. Kang, C. Kim, G. Kim, C.-K. Min PAL, Pohang, Republic of Korea
	We describe an electronics for electron bunch arrival time monitor (BAM) with a less than 10 femtosecond resolution, which was developed in 2017 and is currently in use at PAL-XFEL. When electron bunches go through an S-band monopole cavity, about 1 us long RF signal can be obtained to compare with a low phase noise RF reference. The differential phase jitter corresponds to the arrival time jitter of electron bunches. RF front-end (F/E) which converts the S-band pickup signal to intermediate frequency (IF) signal, is the essential part of a good time resolution. The digitizer and the signal processor of the BAM electronics are installed in an MTCA platform. This paper presents the design scheme, test results of the BAM electronics and future improvement plans.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-WEPA15
About •	paper received ※ 05 September 2018 paper accepted ※ 11 September 2018 issue date ※ 29 January 2019
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WEPA16	Micro-Bunching Instability Monitor for X-ray Free Electron Laser	404
	C. Kim, H.-S. Kang, G. Kim, I.S. Ko PAL, Pohang, Kyungbuk, Republic of Korea J.H. Ko POSTECH, Pohang, Kyungbuk, Republic of Korea
	A direct method was developed to measure the micro-bunching instability in the X-ray Free Electron Laser (XFEL). The micro-bunching instability comes from the interaction between the electron beam and the coherent synchrotron radiation (CSR), and the FEL intensity can be affected significantly by the micro-bunching instability. However, no effective method had been introduced to monitor the micro-bunching instability, so that we installed a CCD camera to measure the micro-bunching instability after the bunch compressor. The CCD camera showed the micro-bunching instability successfully, and more interesting features of the micro-bunching instability were revealed from it.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-WEPA16
About •	paper received ※ 09 September 2018 paper accepted ※ 11 September 2018 issue date ※ 29 January 2019
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WEPA17	Development, Fabrication and Laboratory Tests of Bunch Shape Monitors for ESS Linac	407
	S.A. Gavrilov, D.A. Chermoshentsev, A. Feschenko RAS/INR, Moscow, Russia
	Two Bunch Shape Monitors have been developed and fabricated in INR RAS for European Spallation Source linac. To fulfil the requirements of a 4 ps phase resolution the symmetric λ-type RF-deflector based on the parallel wire line with capacitive plates has been selected. Additional steering magnet to correct incline of the focused electron beam is also used. Limitations due to space charge of the analysed beam and due to external magnetic fields are discussed. The results of the laboratory tests of the monitors are presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-WEPA17
About •	paper received ※ 04 September 2018 paper accepted ※ 11 September 2018 issue date ※ 29 January 2019
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WEPA18	Development of Longitudinal Beam Profile Diagnostics for Beam-beam Effects Study at VEPP-2000	410
	M.V. Timoshenko, V.M. Borin, O.I. Meshkov, Yu. A. Rogovsky, D.B. Shwartz, Yu.M. Zharinov BINP SB RAS, Novosibirsk, Russia V.L. Dorokhov BINP, Novosibirsk, Russia
	The comprehensive development of beam longitudinal profile measurement systems based on stroboscopic optical dissector has started at VEPP-2000 electron-positron collider complex. The dissector was setted and commissioned at booster ring BEP that was deeply upgraded (2013-2015) to achieve top energy of 1 GeV. Bunch lengthening with current was studied at BEP with its new RF-cavity. In addition the method of synchrotron frequency measurement by dissector was applied. After dissector checkouts at BEP the similar studies were carried out with a single beam at VEPP-2000 storage ring in parallel with streak-camera measurements. Good agreement of results was observed. Series of single-turn longitudinal and vertical bunch profiles snapshots was made by streak-camera with respect to delay after counter beam injection. The unexpected longitudinal beam dynamics was observed for intensities above the beam-beam threshold. These studies together with beam-beam coherent oscillations spectra seen by pickups are of a great interest for understanding of flip-flop phenomenon which establish a fundamental luminosity limit at VEPP-2000 operating with round beams.
	Poster WEPA18 [2.269 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-WEPA18
About •	paper received ※ 05 September 2018 paper accepted ※ 11 September 2018 issue date ※ 29 January 2019
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WEPA19	Results from the CERN LINAC4 Longitudinal Bunch Shape Monitor	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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WEPA20	First Results From the Bunch Arrival-Time Monitors at SwissFEL	420
	V.R. Arsov, P. Chevtsov, S. Hunziker, M.G. Kaiser, D. Llorente Sancho, A. Romann, V. Schlott, M. Stadler, D.M. Treyer PSI, Villigen PSI, Switzerland M. Dach Dach Consulting GmbH, Brugg, Switzerland
	Two Bunch Arrival-Time Monitors (BAM), based on fiber optical Mach-Zehnder intensity modulators, which encode the arrival-time information in the amplitude of the laser pulses delivered through a highly stable pulsed optical reference distribution system, have been commissioned and are operational at SwissFEL. The first BAM is at the RF-Gun, the second one is downstream the first bunch compressor. Both BAMs operate simultaneously and measure the arrival-time drift and jitter with less than 5 fs resolution. For the first time we have experimentally verified the excellent SwissFEL bunch stability. We have developed concepts and tested hardware, which enhance the commissioning and user operation. In particular we have successfully tested a tool for fast timing overlap between the electron bunch and the reference laser pulse, which allows fast system set-up and characterization. We have verified the capability for 2-bunch and 100 Hz operation. In comparison to the prototype detectors, which were operational at the SwissFEL test injector, we have achieved an improved BAM resolution in the range 10 pC - 200 pC.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-WEPA20
About •	paper received ※ 05 September 2018 paper accepted ※ 11 September 2018 issue date ※ 29 January 2019
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THOA04	Temporal Diagnostics of Femtosecond Electron Bunches via X-ray Intensity Interferometry
	I. Inoue, T. Hara, Y. Inubushi, H. Tanaka, M. Yabashi RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
	Optical pulses and particle beams with ultrashort temporal duration have been powerful probes for capturing ultrafast processes. An X-ray free-electron laser (XFEL) based on the self-amplified spontaneous emission scheme is a newly developed ultrafast light source with femtosecond duration. The ultrafast XFEL pulses are generated from the electron bunches (e-bunches) that are accelerated to a relativistic speed with strong compression to a femtosecond regime. Evaluation of the temporal profile of the e-bunch is therefore essential for optimizing accelerator parameters for achieving XFEL amplification, as well as for characterizing the XFEL pulse duration. As a new temporal diagnostic scheme for e-bunches, we recently propose an X-ray intensity interferometry using spontaneous X-ray beam generated by the e-bunch [1]. In this presentation, I will talk about the concept of the X-ray intensity interferometry for determination of ultrashort e-bunch duration. Also, I will report on the temporal diagnostics of 8.1-GeV e-bunch at SPring-8 Angstrom compact free-electron LAser (SACLA) using the X-ray intensity interferometry. [1] I. Inoue, T. Hara, Y. Inubushi, K. Tono, T. Inagaki, T. Katayama, Y. Amemiya, H. Tanaka, and M. Yabashi, Phys. Rev. Acc. Beams, in press.
	Slides THOA04 [6.281 MB]
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Paper

Title

Page

WEOA01

Femtosecond Synchronization of PAL-XFEL

C. Kim, H.-S. Kang, I.S. Ko, C.-K. Min
PAL, Pohang, Kyungbuk, Republic of Korea

The PAL-XFEL achieved a 20 fs jitter in the bunch arrival time at the end of undulators and its pump-probe system, which is extremely useful for maintaining a high stability of machine and time-resolved experiments with high time resolution. A low phase noise timing system and high stability high power RF system enable this low jitter. The measurement result shows 10 fs jitter of bunch arrival time at the injector and it increased ~ 20 fs due to the bunch energy variation. The possibility of improving the final jitter is described based on the optimization of bunch compressors and a longitudinal feedback.

Slides WEOA01 [9.603 MB]

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WEOA02

Optical Investigation to Minimize the Electron Bunch Arrival-time Jitter Between Femtosecond Laser Pulses and Electron Bunches for Laser-Driven Plasma Wakefield Accelerators

332

S. Mattiello, A. Penirschke
THM, Friedberg, Germany
H. Schlarb
DESY, Hamburg, Germany

Funding: The work of S. Mattiello is supported by the German Federal Ministry of Education and Research (BMBF) within the Project ’ MAKE-PWA.
In a laser driven plasma based particle accelerators a stable synchronization of the electron bunch and of the plasma wakefield in the range of less than 2 fs is necessary in order to optimize the acceleration. For this purpose we are developing a new shot to shot feedback system with a time resolution of less than 1 fs. As a first step, stable THz pulses are generated by optical rectification of a fraction of the plasma generating high energy laser pulses in a nonlinear lithium niobate crystal. It is planed that the generated THz pulses will energy modulate the electron bunches shot to shot before the plasma to achieve the time resolution of 1 fs. In this contribution we systematically investigate the influence of the optical properties as well as the theoretical description of the THz generation on the conversion efficiency of the generation of short THz pulses in undepleted approximation. We compare different approximations for the modeling of the generation dynamics and of the dielectric function in order to investigate the importance of a detailed description of the optical properties. First results by considering intensity decreasing of the laser pump will be presented.
*The feedback system will be tested at the Accelerator R&D facility SINBAD (Short Innovative Bunches and Accelerators at DESY).

Slides WEOA02 [1.605 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-WEOA02

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paper received ※ 04 September 2018 paper accepted ※ 10 September 2018 issue date ※ 29 January 2019

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WEOA03

First Electro-Optical Bunch Length Measurements from the European XFEL

338

B. Steffen, M.K. Czwalinna, C. Gerth, P. Peier
DESY, Hamburg, Germany

Three electro-optical bunch length detection systems based on spectral decoding have been installed and are being commissioned at the European XFEL. The systems are capable of recording individual longitudinal bunch profiles with sub-picosecond resolution at a bunch repetition rate 1.13 MHz. Bunch lengths and arrival times of entire bunch trains with single-bunch resolution have been measured as well as jitter and drifts for consecutive bunch trains. In this paper, we present first measurement results for the electro-optical detection system located after the second bunch compressor. A preliminary comparison with data from the bunch arrival-time monitor shows good agreement.

Slides WEOA03 [4.496 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-WEOA03

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

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WEOA04

The Application of Beam Arrival Time Measurement at SXFEL

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

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

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WEPA01

A MicroTCA.4 Timing Receiver for the Sirius Timing System

375

J.L. Brito Neto, G.B.M. Bruno, S.R. Marques, L.M. Russo, D.O. Tavares
LNLS, Campinas, Brazil

The AMC FMC carrier (AFC) is a MicroTCA.4 AMC board which has a very flexible clock circuit that enables any clock source to be connected to any clock input, including telecom clock, FMC clocks, programmable VCXO oscillator and FPGA. This paper presents the use of the AFC board as an event receiver connected to the Sirius timing system to provide low jitter synchronized clocks and triggers for Sirius BPM electronics and other devices.

Poster WEPA01 [3.299 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-WEPA01

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

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WEPA02

Recent Progress of Bunch Resolved Beam Diagnostics for BESSY VSR

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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WEPA06

Thermal Coefficient of Delay Measurement of the New Phase Stable Optical Fiber

383

L. Liu, X. Ma, G. Pei
IHEP, Beijing, People’s Republic of China

The Thermal Coefficient of Delay (TCD) is an essen-tial parameter of optical fiber which determines a fiber’s phase transfer stability due to temperature variation. The TCD of a new phase stable single mode optical fiber (YPSOC) from Yangtze Optical Fibre and Cable Compa-ny (YOFC) is measured. The radio frequency (RF) signal is modulated to optical wave by a laser module which is transmitted through the 400-meter long YPSOC to be measured. The returned optical wave is demodulated to RF signal by the photodetector. A phase detector and a data acquisition module (DAQ) are used to acquire the phase difference between the forward and returned sig-nals. Two temperature-stabilized cabinets are designed to maintain and control the ambient temperature of the measurement system. The TCD of less than 10ps/km/K at room temperature is obtained. YPSOC and the meas-urement platform can be applied on signal transmission or measurement system that need to compensate the temperature drift.

Poster WEPA06 [0.653 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-WEPA06

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paper received ※ 03 September 2018 paper accepted ※ 12 September 2018 issue date ※ 29 January 2019

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WEPA07

Beam Phase Measurement System in CSNS Linac

386

P. Li, J. Peng
IHEP CSNS, Guangdong Province, People’s Republic of China
F. Li, T.G. Xu
IHEP, Beijing, People’s Republic of China
M. Meng
DNSC, Dongguan, People’s Republic of China
W. Peng
CETC, Shushan, People’s Republic of China

We developed beam phase measurement system ourselves in CSNS (China Spallation Neutron Source). The resolution of the system is less than 0.1° and the accuracy is less than 1°. It played a key role in CSNS Linac commissioning especially in RFQ and DTL commissioning. Further we measured the beam energy by TOF (Time of Flight) method base on this system. The energy accuracy is less than 0.1 MeV.

Poster WEPA07 [1.070 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-WEPA07

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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

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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WEPA12

Differential Evolution Genetic Algorithm for Beam Bunch Temporal Reconstruction

392

D. Wu, T.H. He, C.L. Lao, P. Li, J. Liu, X. Luo, Q. Pan, L.J. Shan, X. Shen, J. Wang, D.X. Xiao, L.G. Yan, P. Zhang, K. Zhou
CAEP/IAE, Mianyang, Sichuan, People’s Republic of China
Y. Liu
CAEP/IFP, Mainyang, Sichuan, People’s Republic of China

Funding: Work supported by China National Natural Science Foundation of China with grant (11475159, 11505173, 11505174, 11575264, 11605190 and 11105019)
Coherent radiation, such as coherent transition radiation, coherent diffraction radiation, coherent synchrotron radiation, etc, can be used to measure the longitudinal distribution of the electron beam bunch of any length, as long as the coherent radiation spectrum can be measured. In many cases, the Kramers-Krönig relationship is used to reconstruct the temporal distribution of the beam from the coherent radiation spectrum. However, the extrapolation of the low frequency will introduce the uncertainty of the reconstruction. In this paper, an algorithm of differential evolution (DE) for temporal reconstruction is discussed. The DE reconstruction works well for the complex and ultrashort distribution. It will be an effectIve tool to accurately measure the femtosecond bunch temporal structure.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-WEPA12

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paper received ※ 07 September 2018 paper accepted ※ 13 September 2018 issue date ※ 29 January 2019

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WEPA13

Electro-Optic Modulator Based Beam Arrival Time Monitor for SXFEL

396

X.Q. Liu, L.F. Hua, L.W. Lai, Y.B. Leng, R.X. Yuan
SINAP, Shanghai, People’s Republic of China
N. Zhang
SSRF, Shanghai, People’s Republic of China

Beam arrival time monitor (BAM) is an important tool to investigate the temporal characteristic of elec-tron bunch in free electron laser (FEL) like Shanghai soft X-ray Free Electron Laser (SXFEL). Since the timing jitter of electron bunch will affect the FEL’s stability and the resolution of time-resolved experi-ment at FELs, it is necessary to precisely measure the electron bunch arrival time so as to reduce the timing jitter of the electron bunch with beam based feedback. The beam arrival time monitor based on electro-optic modulator (EOM) is already planned and will be de-veloped and tested at SXFEL in the next three years. Here the design and preliminary results of the EOM based beam arrival time monitor will be introduced in this paper.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-WEPA13

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

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WEPA15

Development of BAM Electronics in PAL-XFEL

400

D.C. Shin, J.H. Hong, H.-S. Kang, C. Kim, G. Kim, C.-K. Min
PAL, Pohang, Republic of Korea

We describe an electronics for electron bunch arrival time monitor (BAM) with a less than 10 femtosecond resolution, which was developed in 2017 and is currently in use at PAL-XFEL. When electron bunches go through an S-band monopole cavity, about 1 us long RF signal can be obtained to compare with a low phase noise RF reference. The differential phase jitter corresponds to the arrival time jitter of electron bunches. RF front-end (F/E) which converts the S-band pickup signal to intermediate frequency (IF) signal, is the essential part of a good time resolution. The digitizer and the signal processor of the BAM electronics are installed in an MTCA platform. This paper presents the design scheme, test results of the BAM electronics and future improvement plans.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-WEPA15

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

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WEPA16

Micro-Bunching Instability Monitor for X-ray Free Electron Laser

404

C. Kim, H.-S. Kang, G. Kim, I.S. Ko
PAL, Pohang, Kyungbuk, Republic of Korea
J.H. Ko
POSTECH, Pohang, Kyungbuk, Republic of Korea

A direct method was developed to measure the micro-bunching instability in the X-ray Free Electron Laser (XFEL). The micro-bunching instability comes from the interaction between the electron beam and the coherent synchrotron radiation (CSR), and the FEL intensity can be affected significantly by the micro-bunching instability. However, no effective method had been introduced to monitor the micro-bunching instability, so that we installed a CCD camera to measure the micro-bunching instability after the bunch compressor. The CCD camera showed the micro-bunching instability successfully, and more interesting features of the micro-bunching instability were revealed from it.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-WEPA16

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paper received ※ 09 September 2018 paper accepted ※ 11 September 2018 issue date ※ 29 January 2019

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WEPA17

Development, Fabrication and Laboratory Tests of Bunch Shape Monitors for ESS Linac

407

S.A. Gavrilov, D.A. Chermoshentsev, A. Feschenko
RAS/INR, Moscow, Russia

Two Bunch Shape Monitors have been developed and fabricated in INR RAS for European Spallation Source linac. To fulfil the requirements of a 4 ps phase resolution the symmetric λ-type RF-deflector based on the parallel wire line with capacitive plates has been selected. Additional steering magnet to correct incline of the focused electron beam is also used. Limitations due to space charge of the analysed beam and due to external magnetic fields are discussed. The results of the laboratory tests of the monitors are presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-WEPA17

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

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WEPA18

Development of Longitudinal Beam Profile Diagnostics for Beam-beam Effects Study at VEPP-2000

410

M.V. Timoshenko, V.M. Borin, O.I. Meshkov, Yu. A. Rogovsky, D.B. Shwartz, Yu.M. Zharinov
BINP SB RAS, Novosibirsk, Russia
V.L. Dorokhov
BINP, Novosibirsk, Russia

The comprehensive development of beam longitudinal profile measurement systems based on stroboscopic optical dissector has started at VEPP-2000 electron-positron collider complex. The dissector was setted and commissioned at booster ring BEP that was deeply upgraded (2013-2015) to achieve top energy of 1 GeV. Bunch lengthening with current was studied at BEP with its new RF-cavity. In addition the method of synchrotron frequency measurement by dissector was applied. After dissector checkouts at BEP the similar studies were carried out with a single beam at VEPP-2000 storage ring in parallel with streak-camera measurements. Good agreement of results was observed. Series of single-turn longitudinal and vertical bunch profiles snapshots was made by streak-camera with respect to delay after counter beam injection. The unexpected longitudinal beam dynamics was observed for intensities above the beam-beam threshold. These studies together with beam-beam coherent oscillations spectra seen by pickups are of a great interest for understanding of flip-flop phenomenon which establish a fundamental luminosity limit at VEPP-2000 operating with round beams.

Poster WEPA18 [2.269 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-WEPA18

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

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WEPA19

Results from the CERN LINAC4 Longitudinal Bunch Shape Monitor

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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WEPA20

First Results From the Bunch Arrival-Time Monitors at SwissFEL

420

V.R. Arsov, P. Chevtsov, S. Hunziker, M.G. Kaiser, D. Llorente Sancho, A. Romann, V. Schlott, M. Stadler, D.M. Treyer
PSI, Villigen PSI, Switzerland
M. Dach
Dach Consulting GmbH, Brugg, Switzerland

Two Bunch Arrival-Time Monitors (BAM), based on fiber optical Mach-Zehnder intensity modulators, which encode the arrival-time information in the amplitude of the laser pulses delivered through a highly stable pulsed optical reference distribution system, have been commissioned and are operational at SwissFEL. The first BAM is at the RF-Gun, the second one is downstream the first bunch compressor. Both BAMs operate simultaneously and measure the arrival-time drift and jitter with less than 5 fs resolution. For the first time we have experimentally verified the excellent SwissFEL bunch stability. We have developed concepts and tested hardware, which enhance the commissioning and user operation. In particular we have successfully tested a tool for fast timing overlap between the electron bunch and the reference laser pulse, which allows fast system set-up and characterization. We have verified the capability for 2-bunch and 100 Hz operation. In comparison to the prototype detectors, which were operational at the SwissFEL test injector, we have achieved an improved BAM resolution in the range 10 pC - 200 pC.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-WEPA20

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

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THOA04

Temporal Diagnostics of Femtosecond Electron Bunches via X-ray Intensity Interferometry

I. Inoue, T. Hara, Y. Inubushi, H. Tanaka, M. Yabashi
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan

Optical pulses and particle beams with ultrashort temporal duration have been powerful probes for capturing ultrafast processes. An X-ray free-electron laser (XFEL) based on the self-amplified spontaneous emission scheme is a newly developed ultrafast light source with femtosecond duration. The ultrafast XFEL pulses are generated from the electron bunches (e-bunches) that are accelerated to a relativistic speed with strong compression to a femtosecond regime. Evaluation of the temporal profile of the e-bunch is therefore essential for optimizing accelerator parameters for achieving XFEL amplification, as well as for characterizing the XFEL pulse duration. As a new temporal diagnostic scheme for e-bunches, we recently propose an X-ray intensity interferometry using spontaneous X-ray beam generated by the e-bunch [1]. In this presentation, I will talk about the concept of the X-ray intensity interferometry for determination of ultrashort e-bunch duration. Also, I will report on the temporal diagnostics of 8.1-GeV e-bunch at SPring-8 Angstrom compact free-electron LAser (SACLA) using the X-ray intensity interferometry.
[1] I. Inoue, T. Hara, Y. Inubushi, K. Tono, T. Inagaki, T. Katayama, Y. Amemiya, H. Tanaka, and M. Yabashi, Phys. Rev. Acc. Beams, in press.

Slides THOA04 [6.281 MB]

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