WEP2PT —  Poster Session   (07-Mar-18   16:00—18:00)
Paper Title Page
WEP2PT003 Undulator Phase Matching for the the European XFEL 103

• Y. Li, J. Pflüger
XFEL. EU, Hamburg, Germany

The undulator system in the European XFEL is mainly comprised 5-m long undulator segments and 1.1 m long intersections in between. In intersections the electron velocity is faster than it inside an undulator and the optical phase is detuned. The detune effect is also from the undulator fringe field where electron longitudinal speed also deviates from the oscillation condition. The total detune effect is compensated by a magnetic device called phase shifter, which is correspondingly set for a specific undulator gap. In this paper we introduce the method to set the phase shifter gap for each K parameter according to the measured magnetic field.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FLS2018-WEP2PT003
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WEP2PT008 Microbunching Instability Study in the Linac-Driven FERMI FEL Spreader Beam Line 108

• S. Di Mitri, S. Spampinati
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy

Suppression of microbunching instability (MBI) along high brightness electron beam delivery systems is a priority for Free Electron lasers (FELs) aiming at very narrow bandwidth. The impact of MBI on FEL spectral brilliance is aggravated by the growing demand for multi-user FEL facilities, which adopt multi-bend switchyard lines traversed by high charge density electron beams. This study provides practical guidelines to switchyards design largely immune to MBI, by focusing on the FERMI FEL Spreader line. First, two MBI analytical models [1, 2] are successfully benchmarked along the accelerator. Being the second model flexible enough to describe an arbitrary multi-bend line, and found it in agreement with particle tracking and experimental results, it was used to demonstrate that a newly proposed Spreader optics provides unitary MBI gain while preserving the electron beam brightness.
[1] Z. Huang and K.-J. Kim, Phys. Rev. Special Topics - Accel. Beams 5, 074401 (2002)
[2] R.A. Bosch, K.J. Kleman, and J. Wu, Phys. Rev. Special Topics - Accel. Beams 11, 090702 (2008)

DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FLS2018-WEP2PT008
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WEP2PT014 Strong Focusing Lattice Design for SSMB 113

• T. Rui, X.J. Deng, W.-H. Huang, C.-X. Tang
TUB, Beijing, People's Republic of China
• A. Chao
SLAC, Menlo Park, California, USA

A storage ring applicable for SSMB operation is a critical part of a high average power SSMB EUV light source. A lattice for SSMB based on longitudinal strong focusing is under design in Tsinghua University. To generate and maintain micro-bunching in a storage ring in this scenario, the momentum compaction has to be small. A lattice with low momentum compaction factor is presented in this work. The lattice of the current design consists of two MBA cells with isochronous unit cells to minimize local and global momentum compaction, and two straight sections for insertion devices. The design energy of the ring is 400MeV and the circumference is 94 meters. Nonlinear effects such as higher order momentum compactions will continue to be optimized.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FLS2018-WEP2PT014
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WEP2PT021 The Design and Test of a Stripline Kicker for HEPS 117

• H. Shi, J. Chen, L. Huo, P. Liu, X.L. Shi, G. Wang, L. Wang, N. Wang
IHEP, Beijing, People's Republic of China

A fast stripline kicker is adopted for High Energy Photon Source (HEPS) on-axis injection. The optimization of a prototype 750 mm long kicker has been finished. The 3D simulation results show the final design of wide vane with end cover lowers the beam loss about 31% than the original design does. We develop a feedthrough model with machinable glass ceramic and achieve a VSWR under 1.3 in 0~2 GHz. The assembly of kicker and commercial feedthroughs has been tested with Keysight E5071C. The testing results of S parameters and TDR value show a good agreement with simulation ones.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FLS2018-WEP2PT021
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WEP2PT022 PHASE SHIFTER APPLICATION IN DOUBLE UNDULATOR CONFIGURATION OF HEPS 120

• X.Y. Li, Y. Jiao, S.K. Tian
IHEP, Beijing, People's Republic of China

For over 6 meters long straight-section of HEPS, collinear double-cryogenic permanent magnet undulator(CPMU) is designed for high energy photon users to achieve higher brightness. Angular and spatial profiles of radiation produced by the double undulator configuration have been derived analytically. The efficiency of phase shifter on improving the brightness of double-CPMU is therefore evaluated with the beam energy spread and emittance are taken into account. Optimized beta-functions of electron beam are obtained.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FLS2018-WEP2PT022
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WEP2PT023 Preparation and Characterization of Non-Evaporable Ti-Zr-V Getter Films for HEPS 125

• Y. Ma, D.Z. Guo, , B. Liu, Y.C. Yang
IHEP, Beijing, People's Republic of China

For the low activation temperature and high pumping speed, surface pumping capacity, the TiZrV coatings were chosen to high energy photo source (HEPS). Films of TiZrV alloy have been deposited on 1.5 meter long, cylindrical vacuum chambers of 22mm diameter copper substrates in krypton ambient using DC magnetron sputtering system. Film composition, the activation temperature and pumping properties have been investigated in order to optimize the deposition parameters for vacuum applications. The films were also studied using the X-ray photo-emission electron spectroscopy (XPS) after annealing them at different temperatures ranging from 120°C to 300°C for two hours in ultra-high vacuum environment. Pumping speed and surface pumping capacity testing facilities were also being constructed to investigate the characterization of TiZrV.
Poster WEP2PT023 [1.037 MB]
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FLS2018-WEP2PT023
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WEP2PT024 Influences of Harmonic Cavities on the Single-Bunch Instabilities in Electron Storage Rings 128

• H.S. Xu, N. Wang
IHEP, Beijing, People's Republic of China

Single-bunch instabilities usually determine the bunch performance at high charges as well as the highest single- bunch currents in storage rings. It has been demonstrated that the passive harmonic cavities, which have been widely used in electron storage rings of the third-generation synchrotron light sources, can generally make the beam more stable. However, the influences of the harmonic cavities on the single-bunch instabilities are still not fully understood. We hereby present our study of both longitudinal and transverse single-bunch instabilities when using different settings of the harmonic cavities.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FLS2018-WEP2PT024
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WEP2PT030 Undulator Development Activities at DAVV-Indore 133

• M. Gehlot, R. Khullar, G. Mishra
Devi Ahilya University, Indore, India
• H. Jeevakhan
NITTTR, Bhopal, India
• G. Sharma
RI Research Instruments GmbH, Bergisch Gladbach, Germany

Insertion Device Design Laboratory, DAVV has development activities on in-house design, fabrication and measurement of prototype undulators for synchrotron radiation and free electron laser application. The first prototype U50 was built with six periods, 50mm each period. It was PPM type. The next prototype U20 hybrid device based on NdFeB-Cobalt steel was built with aim to produce 0.24T to 0.05T in 10-20mm gap. The undulator is a 20mm period and there are 25 periods. The next one is U50-II PPM structure with 20 periods. In this paper we review the designs of all these undulators and briefly outline the user facilities of Hall probe bench, Pulsed wire bench and stretched wire magnetic measurement systems at IDDL.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FLS2018-WEP2PT030
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WEP2PT032 Feasibility Study of High Energy X-Ray Source at PLS-II 138

• J.H. Han, J. Lee, S.B. Lee, S.J. Lee, T.-Y. Lee
PAL, Pohang, Kyungbuk, Republic of Korea

PLS-II operates for user service with the 34 beamlines since 2012. For engineering applications, especially for thick metal samples, a high energy X-ray beamline is under consideration to cover a photon energy up to §I{100}{keV} or beyond. By comparing the radiation spectra from various insertion devices types, superconducting wiggler was found to be a most promising candidate. A feasibility study to install the high field wiggler in the PLS-II ring is presented in this paper. Electron beam dynamics studies for a minimum impact on the electron beam parameters and engineering consideration to add more magnets are carried out.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FLS2018-WEP2PT032
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WEP2PT033 Conceptual Design of Superconducting Transverse Gradient Undulator for PAL-XFEL Beamline 142

• S.J. Lee, J.H. Han
PAL, Pohang, Kyungbuk, Republic of Korea

Funding: This research was supported by Basic Science Research Program through the National Research Foundation of Korea(NRF) funded by the Ministry of Science, ICT \& Future Planning(2017R1C1B1012852)
Recently, the transverse gradient undulator (TGU) applications are suggested from the laser plasma wake-field accelerator (LPWA) to ultimate storage ring (USR). Especially for X-ray FEL, TGU can be used to generate the large bandwidth radiation (up to §I10{\percent}). In this proceeding, the review of PAL-XFEL beam parameters and TGU requirements was done to apply a variable large bandwidth operation to the PAL-XFEL beamlines. Also, the conceptual design of TGU, based on superconducting undulator (SCU) was proposed, and B-field calculation results were introduced for PAL-XFEL large bandwidth operation mode.

Poster WEP2PT033 [0.927 MB]
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FLS2018-WEP2PT033
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WEP2PT034 Beyond Uniform Ellipsoidal Laser Shaping for Beam Brightness Improvements at PITZ 146

• H.J. Qian, J.D. Good, C. Koschitzki, M. Krasilnikov, F. Stephan
DESY Zeuthen, Zeuthen, Germany

In the last decades, photoinjector brightness has improved significantly, driven by the needs of free electron lasers and many other applications. One of the key elements is photocathode laser shaping for reducing emittance growth from nonlinear space charge forces. At the photoinjector test facility at DESY in Zeuthen (PITZ), a uniform flattop laser was used to achieve record low emittance for a bunch charge from 20 pC to 1 nC. Due to the ideal 3D space charge force linearization in ellipsoidal electron bunches, uniform ellipsoidal photocathode laser shaping were proposed to improve beam emittance up to 33% for 1 nC beam at PITZ. In this paper, we will show even further transverse emittance improvements in simulations for both flattop and ellipsoidal laser pulses with parabolic radial distribution, versus uniform distributions. The laser shaping effects on longitudinal phase space are also discussed.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FLS2018-WEP2PT034
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WEP2PT038 Conceptual Design for SLS-2 150

• M.M. Dehler, A. Citterio, T. Garvey, M. Hahn, M. Negrazus, L. Schulz, A. Streun, V. Vranković
PSI, Villigen PSI, Switzerland

After 17 years of user operation, we plan to do an upgrade of the Swiss Light Source (SLS) for the period of 2021-2024. The entire storage ring will be replaced with a new layout allowing operation at emittances lowered by factors of 40-50. This is made possible to one part by small aperture magnets allowing for a multi bend achromat design and to the other - a special feature for SLS-2 - reverse bends combined with longitudinal gradient bends (LGB) leading to zero dispersion at the maximum magnetic field, thus minimizing the quantum excitation of the beam due to synchrotron radiation. The compact magnet layout makes use of offset quadrupoles, combined function magnets and longitudinal gradient bends. The chamber with a cross section of 20 mm will be fully NEG coated to ensure good pumping and a quick vacuum conditioning. Numerical simulation of instability thresholds has been performed, we expect values in the order of 2 mA for the single bunch current.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FLS2018-WEP2PT038
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WEP2PT050 Status of CAEP THz Free Electron Laser Oscillator 154

• M. Li, T.H. He, C.L. Lao, P. Li, S.F. Lin, X. Luo, Q. Pan, L.J. Shan, X. Shen, H. Wang, J. Wang, , D.X. Xiao, Y. Xu, X. Yang, P. Zhang, K. Zhou
CAEP/IAE, Mianyang, Sichuan, People's Republic of China

China Academy of Engineering Physics tera-hertz free electron laser (CAEP THz FEL, CTFEL) is the first THz FEL oscillator in China, which was jointly built by CAEP, Peking university and Tsinghua university. The stimulated saturation of the CTFEL was reached in August, 2017. This THz FEL facility consists of a GaAs photocathode high-voltage DC gun, a superconducting RF linac, a planar undulator and a quasi-concentric optical resonator. The terahertz laser's frequency is continuous adjustable from 2 THz to 3 THz. The average power is more than 10 W and the micro-pulse power is more than 0.1 MW.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FLS2018-WEP2PT050
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