FLS2018 - Classification: B - Ring-based Light Sources

Paper	Title	Page
MOA2PL01	Trends and Challenges in the Future Storage Ring Light Sources
	H. Tanaka RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
	Recent innovative design concepts have greatly improved ring-based SR source performance beyond the limitations experienced in the past few decades [1,2] and this movement activates upgrades of operational SR facilities and new facility constructions. This talk gives a landscape of ring-based light source development and then, presents expected challenges in each development branch, beyond the current performance limit. [1] L. Farvacque et al., Proceedings of IPAC2013, Shanghai, China (2013) pp. 79-81. [2] M. Eriksson et al., Proceedings of IPAC2016, Busan, Korea (2016) pp.11-15.
	Slides MOA2PL01 [6.223 MB]
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MOA2PL02	Round Beam Related Challenges in Storage Ring Light Sources
	P. Kuske HZB, Berlin, Germany
	In future low emittance storage ring based light sources round beams are desired for reducing Touschek scattering losses, mitigating emittance growth from IBS, and, last but not least, round beams offer more suitable and better photon beam parameters at the end of beam lines and finally at the user's samples. Various schemes have been proposed to make the naturally flat electron beam in storage rings round. These schemes are more or less challenging and their pros and cons will be presented in this contribution.
	Slides MOA2PL02 [4.103 MB]
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MOP1WB01	Lattice Design for PETRA IV: Towards a Diffraction-Limited Storage Ring	12
	I.V. Agapov, R. Brinkmann, Y.-C. Chae, X.N. Gavaldà, J. Keil, R. Wanzenberg DESY, Hamburg, Germany
	Machine design for the PETRA III storage ring upgrade – PETRA IV – aiming at a 10-30 pm emittance range has been ongoing at DESY. We present the design challenges and approaches for this machine, the baseline lattice and the alternative lattice concepts currently under consideration.
	Slides MOP1WB01 [3.259 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FLS2018-MOP1WB01
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MOP1WB02	Overview of the APS-U Project
	R.R. Lindberg, A. Xiao ANL, Argonne, Illinois, USA
	This talk is about the overview of the APS-U Project.
	Slides MOP1WB02 [3.755 MB]
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MOP1WB03	Current and Future of Storage Ring Based Light Sources in KEK	17
	N. Higashi, K. Harada, T. Honda, Y. Kobayashi, N. Nakamura KEK, Ibaraki, Japan K. Hirano Hiroshima University, Graduate School of Science, Higashi-Hiroshima, Japan
	KEK has two storage-ring light sources. One is Photon Factory (PF). This is the first storage-ring light source in X-ray region in Japan, and the user-run started in 1983. The ring energy is 2.5 GeV, and the emittance has been reduced to 36 nm·rad from 460 nm·rad through some improvements. Another is Photon Factory Advanced Ring (PF-AR). The ring energy is 6.5 GeV, and the single-bunch operation and hard X-ray are featured. The user-run started in 1987, and the emittance is 293 nm·rad. The magnetic lattice is almost the same as the original one. Now we consider the future plans of KEK light sources. One is the fully new facility applying DQBA lattice, named KEK-LS. The circumstance is 571 m, and the emittance is 315 pm·rad @ 3 GeV and 500 mA. In parallel with that, two plans of the only replacements of the lattices reusing existing tunnels of PF and PF-AR are considered. For the PF upgrade, only the arc lattice will be replaced with a new lattice employing combined bends, and the emittance will be improved to 8 nm·rad from 35 nm·rad. For the PF-AR update, fully replacement will be carried out with a new HMBA lattice, and the expected emittance is 520 pm·rad @ 3 GeV and 500 mA.
	Slides MOP1WB03 [7.488 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FLS2018-MOP1WB03
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MOP2WB01	Accelerator Physics Studies for the High Energy Photon Source (HEPS) in Beijing	22
	Y. Jiao, X. Cui, Z. Duan, Y.Y. Guo, D. Ji, J.Y. Li, X.Y. Li, Y.M. Peng, Q. Qin, S.K. Tian, J.Q. Wang, N. Wang, Y. Wei, G. Xu, H.S. Xu, F. Yan, C.H. Yu, Y.L. Zhao IHEP, Beijing, People's Republic of China
	The High Energy Photon Source (HEPS) is the next ring-based light source with an emittance of tens of picometers, and a circumference of about 1.3 km to be built in China soon in a few years. After 10 years' evolution, the design for the High Energy Photon Source is recently bascially determined. We will report the lattice design and physics studies on HEPS, covering issues of storage lattice design and optimization, booster design, injection design, collective effects, error study, insertion device effects, longitudinal dynamics, etc.
	Slides MOP2WB01 [7.280 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FLS2018-MOP2WB01
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MOP2WB02	Status of Construction for ESRF EBS
	T.P. Perron ESRF, Grenoble, France
	The ESRF ' the European Synchrotron Radiation Facility ' is a user facility in Grenoble, France, and the source of the most intense high-energy (6 GeV) X-rays in the world. In 2019, the existing storage ring will be removed and a first-of-a-kind new lattice, based on an innovative arrangement of magnets, will be installed in its place, dramatically reducing the horizontal equilibrium emittance. This ‘fourth-generation' synchrotron will produce an X-ray beam 100 times more brilliant and coherent than the ESRF source today. Coupled with upgraded beamlines and beamline support it will provid previously unimaginable opportunities for applications as varied as nanoscopy, science at extreme conditions and structural biology. The ESRF — Extremely Brilliant Source (EBS) project was launched in 2015 and its current status will be presented, alongside the expected performance of the accelerator, the technical challenges confronted and its future potential fields of applications. A special attention will be put in this paper to the beam dynamics issues (lattice, injection efficiency, lifetime, beam losses,…).
	Slides MOP2WB02 [27.437 MB]
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MOP2WB03	Baseline Lattice for the Upgrade of SOLEIL
	A. Loulergue, P. Brunelle, A. Nadji, L.S. Nadolski, R. Nagaoka, M.-A. Tordeux SOLEIL, Gif-sur-Yvette, France
	Previous MBA studies converged to a lattice composed of 7BA-6BA with a natural emittance value of 200-250 pm·rad range. Due to the difficulties of non-linear optimization in targeting lower emittance values, a decision was made to symmetrize totally the ring with 20 identical cells having long free straight sections longer than 4 m. A 7BA solution elaborated by adopting the sextupole paring scheme with dispersion bumps originally developed at the ESRF-EBS, including reverse-bends, enabling an emittance of 72 pm·rad has been defined as the baseline lattice. The sufficient on-momentum dynamic aperture obtained allows to consider off-axis injection. The linear and nonlinear dynamic properties of the lattice along with the expected performance in terms of brilliance and transverse coherence are presented. In particular, the beta functions tuned down to 1 m in both transverse planes at the center of straight sections allow matching diffraction limited photons up to 3 keV. In addition, a 9BA solution reaching 32 pm·rad and a novel longitudinal on-axis injection scheme involving rapidly decaying RF kicks developed at SOLEIL shall also be presented.
	Slides MOP2WB03 [4.432 MB]
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MOP2WB04	Study of Multi-bend Achromat Lattices for the HALS Diffraction-limited Storage Ring	25
	Z.H. Bai, L. Wang USTC/NSRL, Hefei, Anhui, People's Republic of China
	In this paper, two multi-bend achromat (MBA) lattice concepts, the locally symmetric MBA and MBA with interleaved dispersion bumps, are described, which have been used to design the Hefei Advanced Light Source (HALS), a soft X-ray diffraction-limited storage ring proposed at NSRL. In these two MBA concepts, most of the nonlinear effects caused by sextupoles can be cancelled out within one lattice cell as in the hybrid MBA proposed by ESRF EBS, but the available family number of sextupoles in one cell can be more than that in the hybrid MBA so that, for example, the tune shift with momentum can be better controlled to increase the dynamic momentum aperture (MA). Using the two MBA concepts, three kinds of lattices, 8BA, 6BA and 7BA, have been studied for the HALS, showing large on- and off-momentum dynamic apertures and large enough dynamic MA.
	Slides MOP2WB04 [2.261 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FLS2018-MOP2WB04
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TUA1WB01	Survey of Injection Schemes for Next-generation Light Source Rings
	Z. Duan IHEP, Beijing, People's Republic of China
	Next-generation storage ring-based light sources will be based on the multi-bend achromat (MBA) lattice, as successfully demonstrated in MAX-IV. Such designs promise substantial brightness improvements compared to third-generation light sources, while there is likely to be a trade-off between the optimized brightness, available dynamic aperture for injection and local momentum acceptance related to beam lifetime. Different injection schemes have been proposed for these designs with different requirements on the ring dynamic aperture. In fact, the choice of injection schemes will significantly affect the figure of merit in the lattice optimisation and even the overall design of the facility. This talk will survey these injection schemes, their merits and challenges, and the R&D efforts involved.
	Slides TUA1WB01 [3.490 MB]
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TUA1WB02	Compensation of Transient RF Voltage in a Double RF System Using a Kicker Cavity
	N. Yamamoto, S. Sakanaka, T. Takahashi KEK, Ibaraki, Japan
	In quasi diffraction-limited synchrotron light sources especially in the low-to-medium energy range, emittance growth due to intrabeam scattering (IBS) is a serious concern. To mitigate the IBS, a double rf system is used to lengthen the beam bunches. In the double RF system, the performance of bunch lengthening is limited by the transient beam-loading effect which is induced by bunch gaps in the fill pattern. Even if the superconducting (SC) harmonic cavities (HCs) are used, the performance of bunch lengthening is limited when the bunch gap is large. To improve their performances, we propose the use of a single "kicker" cavity having low loaded Q. The "kicker" cavity provides an rf voltage that is comparable to the fluctuating rf voltages in the main and harmonic cavities, and mitigates the phase shift of beam bunches over the bunch train, while keeping its required generator power modest. As a results of our numerical investigation, the significantly improvement of the bunch lengthening performance can be expected. We will present the concept of this technique and show expected bunch-lengthening performances.
	Slides TUA1WB02 [11.854 MB]
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TUA1WB03	Injection Transient Observation via Bunch-by-bunch Beam Size Measurement System
	H.J. Chen, J. Chen, B. Gao, Y.B. Leng SINAP, Shanghai, People's Republic of China
	A bunch-by-bunch beam size measurement system has been developed at SSRF as a sub-system of 6-dimension bunch-by-bunch diagnostic system, which is an attempt for global bunch information capturing during instabilities by SSRF BI group. The system is composed of direct-imaging optical front-end, high-speed photomultiplier array detector, signal amplifiers and high sampling rate oscilloscope as signal acquisition method. An injection transient process has been successfully captured based on 4-channels signal with strongly bunch position and horizontal beam size oscillation after injection point as betatron oscillation of SSRF storage ring. It demonstrates the bunch-by-bunch measurement capability of the system, which will be used for other fast instabilities monitoring and analysis. Further 16 channels detection using synchronized digitizers and other optimizations is also under developing for high size resolution.
	Slides TUA1WB03 [8.636 MB]
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TUA2WB01	Future Synchrotron Light Source in Thailand
	T. Chanwattana, N. Juntong, K. Kittimanapun, P. Klysubun, T. Pulampong, P. Sudmuang SLRI, Nakhon Ratchasima, Thailand
	A 3-GeV synchrotron light source has been designed as a future light source in Thailand. The storage ring is designed utilising Double Triple Bend Achromat (DTBA) lattice to achieve beam emittance below 1 nm·mrad, maximum beam current of 300 mA and two straight sections per cell. A full energy linac is a promising choice as the storage ring injector due to its potential to be operated as the storage ring injector and an injector for a short pulse facility. The linac can be upgraded to a soft X-ray Free Electron Laser (FEL) facility by extending an undulator section. The design of the linac injector consists of a pre-injector based on a photocathode RF gun, two main linacs based on high gradient S-band structures, and two bunch compressors. The high gradient S-band structure with the accelerating gradient of 35-40 MV/m is suitable to achieve the beam energy of 3 GeV within the injector length of about 150 m. The bunch compressors are included for generating 100-fs electron bunches for the short pulse facility. This paper presents designs and simulation results of the storage ring and the linac injector of Thailand new light source.
	Slides TUA2WB01 [7.487 MB]
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TUA2WB02	Multi-Bend Lattice Analysis Towards a Diffraction Limited Ring Based Light Source	28
	E. Karantzoulis Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
	An analysis of lattice configurations up to 10 bend achromat is presented aiming towards diffraction limited ring based light source. The described analysis can apply to any type of a ring based light source however for practical reasons we consider Elettra that has been operating for users for 24 years; to stay competitive for world-class photon science in the future a massive upgrade of the storage ring is needed. The optimum solution is based on certain design criteria, constraints regarding certain accelerator components and their implications on beam dynamics and user requirements. The space available for insertion devices as well as the impact of anti-bends on the design is also addressed. Two proposed realistic lattices are further discussed taking into account different criteria and user requirements. Those lattices reduce the emittance of the present machine by more than one order of magnitude but at the same time respect many other criteria such as realistic magnet gradients, magnets with magnetic length equal to the physical length, drift space enough for radiation extraction, large available space for insertion devices, minimal shift of the beam lines etc.
	Slides TUA2WB02 [12.781 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FLS2018-TUA2WB02
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TUA2WB03	Modeling Ion Effects for the APS-U
	J.R. Calvey, M. Borland ANL, Argonne, Illinois, USA
	Ions are produced in an accelerator when the beam ionizes residual gas inside the vacuum chamber. If the beam is negatively charged, ions can become trapped in the beam's potential, and their density will increase over time. Trapped ions can cause a variety of undesirable effects, including instability and emittance growth. Typically, simulation of ion effects is done using a "weak-strong" model, in which the ions are modeled using macroparticles, but the beam is assumed to be a fixed Gaussian distribution, with only centroid motion allowed. This type of model necessarily neglects incoherent beam effects, such as decoherence, emittance growth, and tune spread. Recently, an IONEFFECTS element has been incorporated into the particle tracking code ELEGANT. The code has been parallelized, and allows for modeling intra-bunch effects, in combination with other elements. Ion effects have been modeled for the APS-U storage ring and Particle Accumulator Ring, using both a weak-strong code and ELEGANT. Some of the questions investigated include ion instability in the presence of train gaps, ion-induced emittance growth, and multiple ionization.
	Slides TUA2WB03 [1.133 MB]
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TUA2WB04	Ion Instability in the HEPS Storage Ring	34
	S.K. Tian, N. Wang IHEP, Beijing, People's Republic of China
	The High Energy Photon Source (HEPS), a kilometre scale storage ring light source, with a beam energy of 6 GeV and transverse emittances of a few tens of pm.rad, is to be built in Beijing and now is under design. We investigate the ion instability in the storage ring with high beam intensity and low-emittance. We performe a weak-strong simulation to show characteristic phenomena of the instability in the storage ring.
	Slides TUA2WB04 [3.446 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FLS2018-TUA2WB04
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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, P. He, 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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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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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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THP1WB01	Survey of Collective Effects in Next-Generation Light Source Rings
	R. Nagaoka SOLEIL, Gif-sur-Yvette, France
	In this talk we shall attempt to make an overview the general trend in storage rings optimized for the next-generation light sources, in the context of having as a result an important impact on beam collective effects. Reduction of the beam chamber cross section to attain strong magnetic fields for the ultra-low emittance optics is particularly highlighted. A series of collective effects and beam instabilities that are likely to get enhanced shall be reviewed. Some of the recent related theoretical, numerical and experimental studies shall be introduced, along with methods that are considered to be effective in mitigating the former undesirable effects.
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THP1WB02	Impedance Evaluation of PF In-Vacuum Undulator (IVU) with Theories and Simulations and Experimental Confirmation of them by the Tune Measurement	160
	O. Tanaka, N. Nakamura, T. Obina, K. Tsuchiya KEK, Ibaraki, Japan
	Four In-Vacuum Undulators (IVU) were recently installed to Photon Factory (PF) at KEK. The estimate of their impedance and kick factors is a very important issue, because they could considerably increase the total impedance of PF. Moreover, the coupling impedance of the IVUs could lead to the beam energy loss, changes in the bunch shape, betatron tune shifts and, finally, to the various beam instabilities. Using the simulation tool (CST Particle Studio), longitudinal and transverse impedances of the IVUs were evaluated and compared to analytical formulas and measurement results. The study provides guidelines for mitigation of unwanted impedance, for an accurate estimate of its effects on the beam quality and beam instabilities and for the impedance budget of a newly designed next-generation machine which has many IVUs and small-aperture beam pipes.
	Slides THP1WB02 [2.942 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FLS2018-THP1WB02
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THP1WB03	Theory of Longitudinal Multibunch Instabilities Including a Higher-Harmonic (Bunch-Lengthening) Cavity
	R.R. Lindberg ANL, Argonne, Illinois, USA
	Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. The next generation of high-brightness storage rings typically require a higher-harmonic rf system to increase the bunch length and improve lifetime. The modified longitudinal dynamics has important implications for multi-bunch stability, since bunch lengthening also changes the synchrotron frequency both by lowering its mean (which reduces stability), and by increasing its variation with amplitude (which gives rise to Landau damping). To understand these competing effects, we present an analytic theory of longitudinal multi-bunch instabilities in the presence of a higher-harmonic cavity tuned to lengthen the bunch. The theory results in a relatively straightforward extension to the usual matrix-based multi-bunch analysis, and we show how the numerically determined growth rates can be used to understand the role of Landau damping. Finally, we compare predictions of the theoretical growth rates to those extracted from tracking simulations of the proposed APS Upgrade lattice.
	Slides THP1WB03 [1.899 MB]
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THP2WB01	Survey and Outlook for Short-Pulse Schemes in Storage Rings
	A. Jankowiak HZB, Berlin, Germany
	Whereas the generation of photon pulses in the fs or even sub-fs regime is governed by single pass accelerators, the usage of short photon pulses in the ps to sub-ps regime with high repetition rates up to the MHz level and the very high stability provided by storage rings is still of growing interest. In this talk an overview of schemes to generate adequate phase space distributions of the electron bunches for the generation of short photon pulses is given. In particular electron-laser and electron-electron interactions for slicing , as well as manipulation schemes of the transversal and longitudinal beam dynamics, as low alpha-operation, the variable pulse length storage ring scheme, or two-frequency crab cavities, are addressed.
	Slides THP2WB01 [10.554 MB]
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THP2WB02	An Overview of the Progress on SSMB	166
	C.-X. Tang, X.J. Deng, W.-H. Huang, T. Rui TUB, Beijing, People's Republic of China A. Chao, D.F. Ratner SLAC, Menlo Park, California, USA J. Feikes, J. Li, M. Ries HZB, Berlin, Germany C. Feng, B.C. Jiang, X.F. Wang SINAP, Shanghai, People's Republic of China E. Granados MIT, Cambridge, Massachusetts, USA A. Hoehl PTB, Berlin, Germany
	Steady State Microbunching (SSMB) is an electron stor- age ring based scheme proposed by Ratner and Chao to generate high average power coherent radiation and is one of the promising candidates to address the need of kW level EUV source for lithography. After the idea of SSMB was put forward, it has attracted much attention. Recently, with the promote of Chao, in collaboration with colleagues from other institutes, a SSMB task force has been established in Tsinghua University. The experimental proof of the SSMB principle and a feasible lattice design for EUV SSMB are the two main tasks at this moment. SSMB related physics for the formation and maintenance of microbunches will be explored in the first optical proof-of-principle experiment at the MLS storage ring in Berlin. For EUV SSMB lattice design, longitudinal strong focusing and reversible seeding are the two schemes on which the team focuses. The pro- gresses made as well as some challenges from physical and technological aspects for EUV SSMB will be presented in this paper. on behalf of the SSMB team: C. Tang, Alex Chao, X. Deng, W. Huang, and T. Rui of THU; D. Ratner of SLAC; J. Feikes and M. Ries of Helmholtz-Zentrum Berlin; C. Feng, B. Jiang, and X. Wang of SINAP
	Slides THP2WB02 [7.924 MB]
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THP2WB03	Transparent Lattice Characterization with Gated Turn-by-Turn Data of Diagnostic Bunch-Train	171
	Y. Li, W.X. Cheng, K. Ha, R.S. Rainer BNL, Upton, Long Island, New York, USA
	Funding: This work was supported by Depart- ment of Energy Contract No. DE-SC0012704. Methods of characterization of a storage ring's lattice have traditionally been intrusive to routine operations. More importantly, the lattice seen by particles can drift with the beam current due to collective effects. To circumvent this, we have developed a novel approach for dynamically characterizing a storage ring's lattice that is transparent to operations. Our approach adopts a dedicated filling pattern which has a short, separate Diagnostic Bunch-Train (DBT). Gated functionality of a beam position monitor system is capable of collecting turn-by-turn data of the DBT, from which the lattice can then be characterized after excitation. As the DBT comprises only about one percent of the total operational bunches, the effects of its excitation are negligible to users. This approach allows us to localize the distributed quadrupolar wake fields generated in the storage ring vacuum chamber during beam accumulation. While effectively transparent to operations, our approach enables us to dynamically control the beta-beat and phase-beat, and unobtrusively optimize performance of National Synchrotron Light Source-II accelerator during routine operations.
	Slides THP2WB03 [0.711 MB]
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THP2WB04	Laser Seeding of Electron Bunches for Future Ring-Based Light Sources	177
	S. Khan, B. Büsing, N.M. Lockmann, C. Mai, A. Meyer auf der Heide, B. Riemann, B. Sawadski, M. Schmutzler, P. Ungelenk DELTA, Dortmund, Germany
	Funding: Funded by BMBF (05K16PEA, 05K16PEB), MERCUR (Pr-2014-0047), DFG (INST 212/236-1 FUGG) and the Land NRW. In contrast to free-electron lasers (FELs), ring-based light sources are limited in intensity by incoherent emission and in pulse duration by the bunch length. However, FEL seeding schemes can be adopted to generate intense and ultrashort radiation pulses in storage rings by creating laser-induced microbunches within a short slice of the electron bunch. Microbunching gives rise to coherent emission at harmonics of the seed wavelength. In addition, terahertz (THz) radiation is coherently emitted over many turns. At DELTA, a storage ring operated by the TU Dortmund University, coherent harmonic generation (CHG) with single and double 40-fs pulses is routinely performed at seed wavelengths of 800 and 400 nm. Seeding with intensity-modulated pulses to generate tunable narrowband THz radiation is also studied. As a preparation for echo-enabled harmonic generation (EEHG), simultaneous seeding with 800/400-nm pulses in two undulators has been demonstrated. The DELTA storage ring is an excellent testbed to study many aspects of laser seeding and related diagnostics. In addition to short-pulse generation, steady-state microbunching at ring-based light sources will be discussed in the paper.
	Slides THP2WB04 [5.103 MB]
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FRA1PL02	Summary of Working Group B: Ring-Based Light Sources	202
	R.P. Walker DLS, Oxfordshire, United Kingdom Y. Li BNL, Upton, Long Island, New York, USA Q. Qin IHEP, Beijing, People's Republic of China
	This is the summary report of the ring-based light sources working group.
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Paper

Title

Page

MOA2PL01

Trends and Challenges in the Future Storage Ring Light Sources

H. Tanaka
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan

Recent innovative design concepts have greatly improved ring-based SR source performance beyond the limitations experienced in the past few decades [1,2] and this movement activates upgrades of operational SR facilities and new facility constructions. This talk gives a landscape of ring-based light source development and then, presents expected challenges in each development branch, beyond the current performance limit.
[1] L. Farvacque et al., Proceedings of IPAC2013, Shanghai, China (2013) pp. 79-81.
[2] M. Eriksson et al., Proceedings of IPAC2016, Busan, Korea (2016) pp.11-15.

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MOA2PL02

Round Beam Related Challenges in Storage Ring Light Sources

P. Kuske
HZB, Berlin, Germany

In future low emittance storage ring based light sources round beams are desired for reducing Touschek scattering losses, mitigating emittance growth from IBS, and, last but not least, round beams offer more suitable and better photon beam parameters at the end of beam lines and finally at the user's samples. Various schemes have been proposed to make the naturally flat electron beam in storage rings round. These schemes are more or less challenging and their pros and cons will be presented in this contribution.

Slides MOA2PL02 [4.103 MB]

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MOP1WB01

Lattice Design for PETRA IV: Towards a Diffraction-Limited Storage Ring

12

I.V. Agapov, R. Brinkmann, Y.-C. Chae, X.N. Gavaldà, J. Keil, R. Wanzenberg
DESY, Hamburg, Germany

Machine design for the PETRA III storage ring upgrade – PETRA IV – aiming at a 10-30 pm emittance range has been ongoing at DESY. We present the design challenges and approaches for this machine, the baseline lattice and the alternative lattice concepts currently under consideration.

Slides MOP1WB01 [3.259 MB]

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MOP1WB02

Overview of the APS-U Project

R.R. Lindberg, A. Xiao
ANL, Argonne, Illinois, USA

This talk is about the overview of the APS-U Project.

Slides MOP1WB02 [3.755 MB]

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MOP1WB03

Current and Future of Storage Ring Based Light Sources in KEK

17

N. Higashi, K. Harada, T. Honda, Y. Kobayashi, N. Nakamura
KEK, Ibaraki, Japan
K. Hirano
Hiroshima University, Graduate School of Science, Higashi-Hiroshima, Japan

KEK has two storage-ring light sources. One is Photon Factory (PF). This is the first storage-ring light source in X-ray region in Japan, and the user-run started in 1983. The ring energy is 2.5 GeV, and the emittance has been reduced to 36 nm·rad from 460 nm·rad through some improvements. Another is Photon Factory Advanced Ring (PF-AR). The ring energy is 6.5 GeV, and the single-bunch operation and hard X-ray are featured. The user-run started in 1987, and the emittance is 293 nm·rad. The magnetic lattice is almost the same as the original one. Now we consider the future plans of KEK light sources. One is the fully new facility applying DQBA lattice, named KEK-LS. The circumstance is 571 m, and the emittance is 315 pm·rad @ 3 GeV and 500 mA. In parallel with that, two plans of the only replacements of the lattices reusing existing tunnels of PF and PF-AR are considered. For the PF upgrade, only the arc lattice will be replaced with a new lattice employing combined bends, and the emittance will be improved to 8 nm·rad from 35 nm·rad. For the PF-AR update, fully replacement will be carried out with a new HMBA lattice, and the expected emittance is 520 pm·rad @ 3 GeV and 500 mA.

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MOP2WB01

Accelerator Physics Studies for the High Energy Photon Source (HEPS) in Beijing

22

Y. Jiao, X. Cui, Z. Duan, Y.Y. Guo, D. Ji, J.Y. Li, X.Y. Li, Y.M. Peng, Q. Qin, S.K. Tian, J.Q. Wang, N. Wang, Y. Wei, G. Xu, H.S. Xu, F. Yan, C.H. Yu, Y.L. Zhao
IHEP, Beijing, People's Republic of China

The High Energy Photon Source (HEPS) is the next ring-based light source with an emittance of tens of picometers, and a circumference of about 1.3 km to be built in China soon in a few years. After 10 years' evolution, the design for the High Energy Photon Source is recently bascially determined. We will report the lattice design and physics studies on HEPS, covering issues of storage lattice design and optimization, booster design, injection design, collective effects, error study, insertion device effects, longitudinal dynamics, etc.

Slides MOP2WB01 [7.280 MB]

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MOP2WB02

Status of Construction for ESRF EBS

T.P. Perron
ESRF, Grenoble, France

The ESRF ' the European Synchrotron Radiation Facility ' is a user facility in Grenoble, France, and the source of the most intense high-energy (6 GeV) X-rays in the world. In 2019, the existing storage ring will be removed and a first-of-a-kind new lattice, based on an innovative arrangement of magnets, will be installed in its place, dramatically reducing the horizontal equilibrium emittance. This ‘fourth-generation' synchrotron will produce an X-ray beam 100 times more brilliant and coherent than the ESRF source today. Coupled with upgraded beamlines and beamline support it will provid previously unimaginable opportunities for applications as varied as nanoscopy, science at extreme conditions and structural biology. The ESRF — Extremely Brilliant Source (EBS) project was launched in 2015 and its current status will be presented, alongside the expected performance of the accelerator, the technical challenges confronted and its future potential fields of applications. A special attention will be put in this paper to the beam dynamics issues (lattice, injection efficiency, lifetime, beam losses,…).

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MOP2WB03

Baseline Lattice for the Upgrade of SOLEIL

A. Loulergue, P. Brunelle, A. Nadji, L.S. Nadolski, R. Nagaoka, M.-A. Tordeux
SOLEIL, Gif-sur-Yvette, France

Previous MBA studies converged to a lattice composed of 7BA-6BA with a natural emittance value of 200-250 pm·rad range. Due to the difficulties of non-linear optimization in targeting lower emittance values, a decision was made to symmetrize totally the ring with 20 identical cells having long free straight sections longer than 4 m. A 7BA solution elaborated by adopting the sextupole paring scheme with dispersion bumps originally developed at the ESRF-EBS, including reverse-bends, enabling an emittance of 72 pm·rad has been defined as the baseline lattice. The sufficient on-momentum dynamic aperture obtained allows to consider off-axis injection. The linear and nonlinear dynamic properties of the lattice along with the expected performance in terms of brilliance and transverse coherence are presented. In particular, the beta functions tuned down to 1 m in both transverse planes at the center of straight sections allow matching diffraction limited photons up to 3 keV. In addition, a 9BA solution reaching 32 pm·rad and a novel longitudinal on-axis injection scheme involving rapidly decaying RF kicks developed at SOLEIL shall also be presented.

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MOP2WB04

Study of Multi-bend Achromat Lattices for the HALS Diffraction-limited Storage Ring

25

Z.H. Bai, L. Wang
USTC/NSRL, Hefei, Anhui, People's Republic of China

In this paper, two multi-bend achromat (MBA) lattice concepts, the locally symmetric MBA and MBA with interleaved dispersion bumps, are described, which have been used to design the Hefei Advanced Light Source (HALS), a soft X-ray diffraction-limited storage ring proposed at NSRL. In these two MBA concepts, most of the nonlinear effects caused by sextupoles can be cancelled out within one lattice cell as in the hybrid MBA proposed by ESRF EBS, but the available family number of sextupoles in one cell can be more than that in the hybrid MBA so that, for example, the tune shift with momentum can be better controlled to increase the dynamic momentum aperture (MA). Using the two MBA concepts, three kinds of lattices, 8BA, 6BA and 7BA, have been studied for the HALS, showing large on- and off-momentum dynamic apertures and large enough dynamic MA.

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TUA1WB01

Survey of Injection Schemes for Next-generation Light Source Rings

Z. Duan
IHEP, Beijing, People's Republic of China

Next-generation storage ring-based light sources will be based on the multi-bend achromat (MBA) lattice, as successfully demonstrated in MAX-IV. Such designs promise substantial brightness improvements compared to third-generation light sources, while there is likely to be a trade-off between the optimized brightness, available dynamic aperture for injection and local momentum acceptance related to beam lifetime. Different injection schemes have been proposed for these designs with different requirements on the ring dynamic aperture. In fact, the choice of injection schemes will significantly affect the figure of merit in the lattice optimisation and even the overall design of the facility. This talk will survey these injection schemes, their merits and challenges, and the R&D efforts involved.

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TUA1WB02

Compensation of Transient RF Voltage in a Double RF System Using a Kicker Cavity

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

In quasi diffraction-limited synchrotron light sources especially in the low-to-medium energy range, emittance growth due to intrabeam scattering (IBS) is a serious concern. To mitigate the IBS, a double rf system is used to lengthen the beam bunches. In the double RF system, the performance of bunch lengthening is limited by the transient beam-loading effect which is induced by bunch gaps in the fill pattern. Even if the superconducting (SC) harmonic cavities (HCs) are used, the performance of bunch lengthening is limited when the bunch gap is large. To improve their performances, we propose the use of a single "kicker" cavity having low loaded Q. The "kicker" cavity provides an rf voltage that is comparable to the fluctuating rf voltages in the main and harmonic cavities, and mitigates the phase shift of beam bunches over the bunch train, while keeping its required generator power modest. As a results of our numerical investigation, the significantly improvement of the bunch lengthening performance can be expected. We will present the concept of this technique and show expected bunch-lengthening performances.

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TUA1WB03

Injection Transient Observation via Bunch-by-bunch Beam Size Measurement System

H.J. Chen, J. Chen, B. Gao, Y.B. Leng
SINAP, Shanghai, People's Republic of China

A bunch-by-bunch beam size measurement system has been developed at SSRF as a sub-system of 6-dimension bunch-by-bunch diagnostic system, which is an attempt for global bunch information capturing during instabilities by SSRF BI group. The system is composed of direct-imaging optical front-end, high-speed photomultiplier array detector, signal amplifiers and high sampling rate oscilloscope as signal acquisition method. An injection transient process has been successfully captured based on 4-channels signal with strongly bunch position and horizontal beam size oscillation after injection point as betatron oscillation of SSRF storage ring. It demonstrates the bunch-by-bunch measurement capability of the system, which will be used for other fast instabilities monitoring and analysis. Further 16 channels detection using synchronized digitizers and other optimizations is also under developing for high size resolution.

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TUA2WB01

Future Synchrotron Light Source in Thailand

T. Chanwattana, N. Juntong, K. Kittimanapun, P. Klysubun, T. Pulampong, P. Sudmuang
SLRI, Nakhon Ratchasima, Thailand

A 3-GeV synchrotron light source has been designed as a future light source in Thailand. The storage ring is designed utilising Double Triple Bend Achromat (DTBA) lattice to achieve beam emittance below 1 nm·mrad, maximum beam current of 300 mA and two straight sections per cell. A full energy linac is a promising choice as the storage ring injector due to its potential to be operated as the storage ring injector and an injector for a short pulse facility. The linac can be upgraded to a soft X-ray Free Electron Laser (FEL) facility by extending an undulator section. The design of the linac injector consists of a pre-injector based on a photocathode RF gun, two main linacs based on high gradient S-band structures, and two bunch compressors. The high gradient S-band structure with the accelerating gradient of 35-40 MV/m is suitable to achieve the beam energy of 3 GeV within the injector length of about 150 m. The bunch compressors are included for generating 100-fs electron bunches for the short pulse facility. This paper presents designs and simulation results of the storage ring and the linac injector of Thailand new light source.

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TUA2WB02

Multi-Bend Lattice Analysis Towards a Diffraction Limited Ring Based Light Source

28

E. Karantzoulis
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy

An analysis of lattice configurations up to 10 bend achromat is presented aiming towards diffraction limited ring based light source. The described analysis can apply to any type of a ring based light source however for practical reasons we consider Elettra that has been operating for users for 24 years; to stay competitive for world-class photon science in the future a massive upgrade of the storage ring is needed. The optimum solution is based on certain design criteria, constraints regarding certain accelerator components and their implications on beam dynamics and user requirements. The space available for insertion devices as well as the impact of anti-bends on the design is also addressed. Two proposed realistic lattices are further discussed taking into account different criteria and user requirements. Those lattices reduce the emittance of the present machine by more than one order of magnitude but at the same time respect many other criteria such as realistic magnet gradients, magnets with magnetic length equal to the physical length, drift space enough for radiation extraction, large available space for insertion devices, minimal shift of the beam lines etc.

Slides TUA2WB02 [12.781 MB]

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TUA2WB03

Modeling Ion Effects for the APS-U

J.R. Calvey, M. Borland
ANL, Argonne, Illinois, USA

Ions are produced in an accelerator when the beam ionizes residual gas inside the vacuum chamber. If the beam is negatively charged, ions can become trapped in the beam's potential, and their density will increase over time. Trapped ions can cause a variety of undesirable effects, including instability and emittance growth. Typically, simulation of ion effects is done using a "weak-strong" model, in which the ions are modeled using macroparticles, but the beam is assumed to be a fixed Gaussian distribution, with only centroid motion allowed. This type of model necessarily neglects incoherent beam effects, such as decoherence, emittance growth, and tune spread. Recently, an IONEFFECTS element has been incorporated into the particle tracking code ELEGANT. The code has been parallelized, and allows for modeling intra-bunch effects, in combination with other elements. Ion effects have been modeled for the APS-U storage ring and Particle Accumulator Ring, using both a weak-strong code and ELEGANT. Some of the questions investigated include ion instability in the presence of train gaps, ion-induced emittance growth, and multiple ionization.

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TUA2WB04

Ion Instability in the HEPS Storage Ring

34

S.K. Tian, N. Wang
IHEP, Beijing, People's Republic of China

The High Energy Photon Source (HEPS), a kilometre scale storage ring light source, with a beam energy of 6 GeV and transverse emittances of a few tens of pm.rad, is to be built in Beijing and now is under design. We investigate the ion instability in the storage ring with high beam intensity and low-emittance. We performe a weak-strong simulation to show characteristic phenomena of the instability in the storage ring.

Slides TUA2WB04 [3.446 MB]

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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.

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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.

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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.

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WEP2PT023

Preparation and Characterization of Non-Evaporable Ti-Zr-V Getter Films for HEPS

125

Y. Ma, D.Z. Guo, P. He, 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]

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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.

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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.

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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.

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reference for this paper ※ https://doi.org/10.18429/JACoW-FLS2018-WEP2PT038

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THP1WB01

Survey of Collective Effects in Next-Generation Light Source Rings

R. Nagaoka
SOLEIL, Gif-sur-Yvette, France

In this talk we shall attempt to make an overview the general trend in storage rings optimized for the next-generation light sources, in the context of having as a result an important impact on beam collective effects. Reduction of the beam chamber cross section to attain strong magnetic fields for the ultra-low emittance optics is particularly highlighted. A series of collective effects and beam instabilities that are likely to get enhanced shall be reviewed. Some of the recent related theoretical, numerical and experimental studies shall be introduced, along with methods that are considered to be effective in mitigating the former undesirable effects.

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THP1WB02

Impedance Evaluation of PF In-Vacuum Undulator (IVU) with Theories and Simulations and Experimental Confirmation of them by the Tune Measurement

160

O. Tanaka, N. Nakamura, T. Obina, K. Tsuchiya
KEK, Ibaraki, Japan

Four In-Vacuum Undulators (IVU) were recently installed to Photon Factory (PF) at KEK. The estimate of their impedance and kick factors is a very important issue, because they could considerably increase the total impedance of PF. Moreover, the coupling impedance of the IVUs could lead to the beam energy loss, changes in the bunch shape, betatron tune shifts and, finally, to the various beam instabilities. Using the simulation tool (CST Particle Studio), longitudinal and transverse impedances of the IVUs were evaluated and compared to analytical formulas and measurement results. The study provides guidelines for mitigation of unwanted impedance, for an accurate estimate of its effects on the beam quality and beam instabilities and for the impedance budget of a newly designed next-generation machine which has many IVUs and small-aperture beam pipes.

Slides THP1WB02 [2.942 MB]

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THP1WB03

Theory of Longitudinal Multibunch Instabilities Including a Higher-Harmonic (Bunch-Lengthening) Cavity

R.R. Lindberg
ANL, Argonne, Illinois, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
The next generation of high-brightness storage rings typically require a higher-harmonic rf system to increase the bunch length and improve lifetime. The modified longitudinal dynamics has important implications for multi-bunch stability, since bunch lengthening also changes the synchrotron frequency both by lowering its mean (which reduces stability), and by increasing its variation with amplitude (which gives rise to Landau damping). To understand these competing effects, we present an analytic theory of longitudinal multi-bunch instabilities in the presence of a higher-harmonic cavity tuned to lengthen the bunch. The theory results in a relatively straightforward extension to the usual matrix-based multi-bunch analysis, and we show how the numerically determined growth rates can be used to understand the role of Landau damping. Finally, we compare predictions of the theoretical growth rates to those extracted from tracking simulations of the proposed APS Upgrade lattice.

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THP2WB01

Survey and Outlook for Short-Pulse Schemes in Storage Rings

A. Jankowiak
HZB, Berlin, Germany

Whereas the generation of photon pulses in the fs or even sub-fs regime is governed by single pass accelerators, the usage of short photon pulses in the ps to sub-ps regime with high repetition rates up to the MHz level and the very high stability provided by storage rings is still of growing interest. In this talk an overview of schemes to generate adequate phase space distributions of the electron bunches for the generation of short photon pulses is given. In particular electron-laser and electron-electron interactions for slicing , as well as manipulation schemes of the transversal and longitudinal beam dynamics, as low alpha-operation, the variable pulse length storage ring scheme, or two-frequency crab cavities, are addressed.

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THP2WB02

An Overview of the Progress on SSMB

166

C.-X. Tang, X.J. Deng, W.-H. Huang, T. Rui
TUB, Beijing, People's Republic of China
A. Chao, D.F. Ratner
SLAC, Menlo Park, California, USA
J. Feikes, J. Li, M. Ries
HZB, Berlin, Germany
C. Feng, B.C. Jiang, X.F. Wang
SINAP, Shanghai, People's Republic of China
E. Granados
MIT, Cambridge, Massachusetts, USA
A. Hoehl
PTB, Berlin, Germany

Steady State Microbunching (SSMB) is an electron stor- age ring based scheme proposed by Ratner and Chao to generate high average power coherent radiation and is one of the promising candidates to address the need of kW level EUV source for lithography. After the idea of SSMB was put forward, it has attracted much attention. Recently, with the promote of Chao, in collaboration with colleagues from other institutes, a SSMB task force has been established in Tsinghua University. The experimental proof of the SSMB principle and a feasible lattice design for EUV SSMB are the two main tasks at this moment. SSMB related physics for the formation and maintenance of microbunches will be explored in the first optical proof-of-principle experiment at the MLS storage ring in Berlin. For EUV SSMB lattice design, longitudinal strong focusing and reversible seeding are the two schemes on which the team focuses. The pro- gresses made as well as some challenges from physical and technological aspects for EUV SSMB will be presented in this paper.
on behalf of the SSMB team: C. Tang, Alex Chao, X. Deng, W. Huang, and T. Rui of THU; D. Ratner of SLAC; J. Feikes and M. Ries of Helmholtz-Zentrum Berlin; C. Feng, B. Jiang, and X. Wang of SINAP

Slides THP2WB02 [7.924 MB]

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THP2WB03

Transparent Lattice Characterization with Gated Turn-by-Turn Data of Diagnostic Bunch-Train

171

Y. Li, W.X. Cheng, K. Ha, R.S. Rainer
BNL, Upton, Long Island, New York, USA

Funding: This work was supported by Depart- ment of Energy Contract No. DE-SC0012704.
Methods of characterization of a storage ring's lattice have traditionally been intrusive to routine operations. More importantly, the lattice seen by particles can drift with the beam current due to collective effects. To circumvent this, we have developed a novel approach for dynamically characterizing a storage ring's lattice that is transparent to operations. Our approach adopts a dedicated filling pattern which has a short, separate Diagnostic Bunch-Train (DBT). Gated functionality of a beam position monitor system is capable of collecting turn-by-turn data of the DBT, from which the lattice can then be characterized after excitation. As the DBT comprises only about one percent of the total operational bunches, the effects of its excitation are negligible to users. This approach allows us to localize the distributed quadrupolar wake fields generated in the storage ring vacuum chamber during beam accumulation. While effectively transparent to operations, our approach enables us to dynamically control the beta-beat and phase-beat, and unobtrusively optimize performance of National Synchrotron Light Source-II accelerator during routine operations.

Slides THP2WB03 [0.711 MB]

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THP2WB04

Laser Seeding of Electron Bunches for Future Ring-Based Light Sources

177

S. Khan, B. Büsing, N.M. Lockmann, C. Mai, A. Meyer auf der Heide, B. Riemann, B. Sawadski, M. Schmutzler, P. Ungelenk
DELTA, Dortmund, Germany

Funding: Funded by BMBF (05K16PEA, 05K16PEB), MERCUR (Pr-2014-0047), DFG (INST 212/236-1 FUGG) and the Land NRW.
In contrast to free-electron lasers (FELs), ring-based light sources are limited in intensity by incoherent emission and in pulse duration by the bunch length. However, FEL seeding schemes can be adopted to generate intense and ultrashort radiation pulses in storage rings by creating laser-induced microbunches within a short slice of the electron bunch. Microbunching gives rise to coherent emission at harmonics of the seed wavelength. In addition, terahertz (THz) radiation is coherently emitted over many turns. At DELTA, a storage ring operated by the TU Dortmund University, coherent harmonic generation (CHG) with single and double 40-fs pulses is routinely performed at seed wavelengths of 800 and 400 nm. Seeding with intensity-modulated pulses to generate tunable narrowband THz radiation is also studied. As a preparation for echo-enabled harmonic generation (EEHG), simultaneous seeding with 800/400-nm pulses in two undulators has been demonstrated. The DELTA storage ring is an excellent testbed to study many aspects of laser seeding and related diagnostics. In addition to short-pulse generation, steady-state microbunching at ring-based light sources will be discussed in the paper.

Slides THP2WB04 [5.103 MB]

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FRA1PL02

Summary of Working Group B: Ring-Based Light Sources

202

R.P. Walker
DLS, Oxfordshire, United Kingdom
Y. Li
BNL, Upton, Long Island, New York, USA
Q. Qin
IHEP, Beijing, People's Republic of China

This is the summary report of the ring-based light sources working group.

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