FLS2023 - Classification: D - Key Technologies

Paper	Title	Page
MO1L4	The Challenges and Benefits of Increased Application of Permanent Magnets to Future Light Sources
	J. Chavanne ESRF, Grenoble, France
	New storage ring based light sources have been recently constructed or are planned with the aim to reduce the horizontal emittance of the electron beam by about two orders of magnitude. It leads to a considerable increase of the brilliance of the photon beams produced at the sources installed around the storage ring. In many cases theses developments correspond to the upgrades of existing third generation facilities. The resulting accelerator lattice is a very compact arrangement of different types of magnets with demanding field properties. In addition, the need to provide energy saving solutions comes as an additional boundary condition. In this context, it looks obvious that Permanent Magnets (PMs) have been and are considered as an interesting alternative to conventional electromagnets. The ESRF Extremely Brilliant Source (EBS) in operation since beginning of 2020 is an example of the successful implantation of PM dipoles. For the majority of ongoing upgrades PMs corresponds to a large fraction of the storage ring magnets. They presently include dipole, quadrupole or combined dipole quadrupole structures. However, for PMs there is a number of specific difficulties to be addressed. These include for example the need to reach the absolute field strength for device which are not tuneable, the thermal stability or the long term stability. These different subjects will be discussed in the light of the EBS experience and the progresses made at several facilities with planned upgrades.
	Slides MO1L4 [3.932 MB]
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TU3D1	Developments in SRF Technology for Light Source Applications
	D. Gonnella SLAC, Menlo Park, California, USA
	Funding: US DoE Significant developments in SRF technology have occurred in the last 5 years motivated by interest in light sources and future colliders. Specifically, LCLS-II and LCLS-II-HE at SLAC have driven high gradient and high Q₀ R&D in SRF across the field. New understandings in doping protocols, cavity processing, and clean room procedures have enabled cryomodules to be constructed that reach previously unattainable performance. Further developments in novel cavity processing methods such as mid-temperature baking and alternate materials such as niobium-3-tin enable a new range of operations for future accelerators. Early operations from LCLS-II and EU-XFEL show that SRF technology is already being used to produce world class light source facilities. Here we present a review of the latest developments in SRF technology both in the R&D phase and in newly installed accelerators and their impact on future light source development and performance.
	Slides TU3D1 [5.769 MB]
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TU3D2	Highly Reliable RF Power Sources for Improvement of the Accelerator Availability
	M. Lau TRUMPF Huettinger GmbH, Freiburg, Germany
	The trend in exchanging established tube technolo-gy by solid-state based RF power amplifier for particle accelerators around the world is ongoing. Since the first installations* of such amplifier systems several concepts were developed and installed. As the RF sources are key for the accelerator availability their reliability plays a crucial role. This needs to be considered during the design phase of the overall amplifier system architecture in a new way compared to the tube technology. For tubes it is straight forward as usually one tube powers one or more cavities due to the high power provided. But this also bears the risk of a single point of failure despite the need of high voltage power supplies, continuous degradation and their availability, just to mention the most important aspects. For solid-state power amplifier many transistor units need to be combined for delivering the needed RF power to each cavity. The combining concepts and the overall system architecture finally determine the possibility of de-rating options and redundancy of transistors for compensation of failed units within the system, and thus the overall availability. Our concept for com-bining several transistors in amplifier units* and assembling these units into racks recently has proven an outstanding performance. For 8,419 hours of opera-tional time, we had a total of 13.9 hours for not being available due to incidents. This results in a total system availability of ~99.83% for more than 980 operational amplifier units at customer site. Here, we want to demonstrate our system architec-ture and the design aspects we considered for reaching this high performance. We think that this is a crucial contribution for bringing this technology one step further to maturity. * R. Lopes et al., CWRF08, CERN Geneva, March 2008 E. Montesinos, I.FAST Accelerator-Industry Workshop, CERN, May, 2022 * M. Lau et al., HIAT Conference, Darmstadt, Germany, 2022
	Slides TU3D2 [5.323 MB]
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TU3D3	Application of Cryo-copper Accelerating Structures Towards Future Light Sources
	E.A. Nanni SLAC, Menlo Park, California, USA
	Cryogenic operation of copper accelerating structures results in increase accelerating gradients and reduced rf power requirements. The combination of cryogenic operation with distributed coupling accelerator topologies further enhances the flexibility of the designer in optimizing the performance of the accelerator. The combination of these advances creates the possibility of generating high-brightness beams in compact footprints (up to 250 MeV/m accelerating gradients). To date this technology has been explored primarily in the context of a future high energy physics facility. In this talk we will present the study of a new concept for a high gradient, high power accelerator with beam characteristics suitable to study the Higgs boson, the Cool Copper Collider (C3). We will present the latest demonstrated performance of prototype accelerators and highlight the future development path for C3 accelerator technology. In particular, we will focus on benefits to future light source concepts to decrease machine size, increase repetition rate, enable multi-bunch operation and preserve high brightness beams. Possible use cases for future light sources will be presented.
	Slides TU3D3 [6.783 MB]
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TU3D4	Compact HOM-damped RF Cavity for a Next Generation Light Source	74
	H. Ego KEK, Ibaraki, Japan T. Asaka, N. Nishimori QST, Sendai, Miyagi, Japan T. Inagaki, H. Tanaka RIKEN SPring-8 Center, Hyogo, Japan T. Ohshima, T. Tomai, H. Yamaguchi JASRI, Hyogo, Japan
	A beam-accelerating RF cavity with a new HOM-damping structure was designed in order to suppress coupled-bunch instabilities in a next generation light source with an ultra-low emittance and supplying X-rays approaching their diffraction limits. The TM020 mode at 509 MHz is selected as a beam-accelerating mode because it has a high Q-value of 60,000 and a shunt impedance sufficient for beam acceleration and brings a compact HOM-damping structure to the cavity differently from massive types of cavities with waveguides or pipes extracting HOM power. Two shallow slots are cut on the cavity inner-wall and materials absorbing RF waves are directly fitted into them. They work as HOM dampers without affecting the RF properties of the beam-accelerating mode. A prototype cavity of OFHC copper was fabricated to demonstrate the HOM-damping and generating an accelerating voltage of 900 kV in the cavity. Since the cavity was successful in operation up to 135 kW, the feasibility of both the high-power operation and the damping structure was proved. Four actual cavities were produced and installed to the new 3-GeV synchrotron radiation facility, NanoTerasu in Japan.
	Slides TU3D4 [8.581 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-FLS2023-TU3D4
About •	Received ※ 22 August 2023 — Revised ※ 23 August 2023 — Accepted ※ 31 August 2023 — Issued ※ 02 December 2023
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TU3D5	Electron RF Injectors for Next Generation FELs
	B.L. Militsyn STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
	A modern trend in the next generation of X-ray Free Electron Lasers (FEL) is the development of tools for the investigation of dynamic processes on the (sub)atomic scale that requires photon beams with energies of 20-25 keV with a repetition rate of 1 MHz or higher. At reasonable energies of the drive linac of 8-10 GeV optimum FEL performance requires an electron beam with emittance of 0.1 mm.mrad or lower. Higher value of the emittance leads to essential degradation in FEL performance and significant increase in required undulator length. In this work we try to estimate the ultimate beam brightness and bunch repetition rate that may be achieved with existing electron injector technologies and outline possible ways of obtaining beams with the parameters required for future FELs. In particular, we will discuss possible injector designs for the ongoing UK XFEL project.
	Slides TU3D5 [3.260 MB]
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WE1L3	Enabling Technology Towards Multiline Compact XFELs
	J.M. Byrd ANL, Lemont, Illinois, USA
	After almost 15 years of openation, XFELs are well-established light sources for addressing many problems in science. However, most FEL facilities are relatively large to reach the beam energies and geometric emittancs needed to lase at higher photon energy. Furthermore, the XFEL can only serve one or a few users at at time. At Argonne National Laboratory, we have initiated a research program to address some of these issues. We report on our program develop independent undulator arrays to allow more simultaneous users. We are developing a compact Adjustable Phase Undulator that have a compact transverse footprint and a superconducting undulator design with multiple undulators per cryostat. In addition, we report on a new concept for an ultrolow emittance electron gun which reaches fields several times higher than existing guns. This is achieved by generating <10 nsec RF pulses similar to other two-beam accelerator concepts.
	Slides WE1L3 [3.183 MB]
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WE1L4	Operating Liquid MetalJet X-ray Sources for Materials Research	159
	M. Boin, D. Apel, F. García-Moreno, C. Genzel, P.H. Kamm, M. Klaus, R. Mainz, G. Wagener, R.C. Wimpory HZB, Berlin, Germany
	Even on the 100th anniversary of the death of Wilhelm Conrad Röntgen, the demand for applications of his discovery of X-rays is not diminishing. On the contrary, both academic and industrial research and development need X-ray generating devices with ever-improving properties more than ever to meet the current challenges of science and technology. For this reason, the development of next-generation synchrotrons is being driven forward and made available to users worldwide. Nevertheless, the availability of synchrotron beamtime will always remain limited, even with the most brilliant sources for ultra-fast and high-throughput experiments. That is why the operation of and research with decentralized laboratory equipment becomes just as important. This presentation will therefore focus on the latest developments in laboratory sources in the hard X-ray regime for materials research. In this context, Helmholtz-Zentrum Berlin (HZB) has commissioned EXCILLUM’s new high-flux MetalJet X-ray devices providing photon energies up to 70 keV and 160 keV, respectively. The presentation will give a summary of the technical specifications of these sources utilizing a liquid metal as anode material and the diffractometer lab installations operated with them at HZB. Selected experimental examples are shown providing an overview of applications performed at the MetalJet measuring stations - ranging from residual stress analysis on technical parts to real-time measurements on thin films for photovoltaics applying angle- and energy-dispersive diffraction as well as studies in the field of time-resolved imaging. A comparison to synchrotron measurements is made to benchmark the performance of the available setups. In conclusion, the effort and expenses required to operate such X-ray devices for in-house research and user service measurements are summarized.
	Slides WE1L4 [3.423 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-FLS2023-WE1L4
About •	Received ※ 23 August 2023 — Revised ※ 29 August 2023 — Accepted ※ 30 August 2023 — Issued ※ 02 December 2023
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WE3D1	Femtosecond Synchronization of Large Scale FELs - Achievements, Limitations and Mitigation Paths
	H. Schlarb, M.K. Czwalinna, S. Schulz DESY, Hamburg, Germany
	Over the past decade, synchronization of large-scale accelerators has advanced from picosecond stability reaching nowadays few femtoseconds only. Driver behind these developments are Free-Electron Lasers, requiring high electron beam compression factor for lasing and the production of ultra-short photon pulses for precision time-evolution experiments in pump-probe laser arrangements. The high control demand of FELs on their electron beam phase space and arrival time triggered a series of key technology development in the accelerator community. These developments span for state-of-the-art RF components, pushing the limits on precision RF cavity control, ultra-stable optical reference distributions to novel new beam diagnostic techniques, all aiming to reach femtosecond beam and pump-probe stabilities. In this presentation, an introduction to key elements causing beam arrival time instabilities and synchronization losses is given. Using EuXFEL and FLASH at example, achievable performance with currently available technologies are summarized. Limitations towards single digit femtosecond or even attosecond synchronization are discussed together with possible mitigation paths.
	Slides WE3D1 [7.362 MB]
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WE3D2	Advanced Electron Beam Diagnostics for FELs
	P. Krejcik SLAC, Menlo Park, California, USA
	The critical electron beam instrumentation needs for FELs are identified - high-resolution beam position and alignment, emittance and energy spread, and longitudinal profile measurements. The performance limitations for each are discussed and state-of-the-art techniques from several FEL light source facilities will be presented. New challenges for integrating instrumentation in SC undulators are also addressed. A survey of proposals for advanced techniques will be included, especially those focusing on sub-fs resolution for longitudinal measurements and synchronization for attosecond science.
	Slides WE3D2 [4.554 MB]
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WE3D3	Beam Diagnostics for Ultra-low Emittance Storage Rings
	V. Schlott PSI, Villigen PSI, Switzerland
	Multi-bend achromat (MBA) lattices have enabled the realization of ultra-low emittance storage rings as diffraction-limited synchrotron radiation sources providing much higher photon brilliance and coherence in the wavelength range of hard x-rays than third generation user facilities. While advances in technology and continuous upgrading of state-of-the-art diagnostics systems have already led to outstanding performance levels of beam instrumentation at the present generation of light sources, more stringent demands on beam stability and control induce a number of technical improvements and stimulate advanced concepts of combining electron and photon beam-based signals. Based on diagnostics requirements for diffraction-limited light sources, this talk will give an overview of new electron and photon beam instrumentation developments and highlight beam stabilization concepts aiming for the exploitation of the full capacity of fourth generation synchrotron radiation user facilities.
	Slides WE3D3 [3.746 MB]
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WE4P33	Design of a 166.6 MHz HOM Damped Copper Cavity for the Southern Advanced Photon Source	207
	J.Y. Zhu, X. Li, Z.J. Lu IHEP, Beijing, People’s Republic of China J.B. Yu IHEP CSNS, Guangdong Province, People’s Republic of China
	Funding: This work was supported by the National Natural Science Foundation of China (12205168). The Southern Advanced Photon Source (SAPS) aims to achieve ultra-low emittances and is expected to adopt low-frequency cavities (< 200 MHz) to accommodates on-axis injection. This paper focuses on the design of a 166.6 MHz HOM-damped normal conducting (NC) cavity for the SAPS. We propose a novel approach to achieve efficient HOM damping by optimizing the lowest frequency HOM and implementing a beam-line absorber in a coaxial resonant NC cavity. Notably, unlike beam-line absorbers for conventional NC cavities, the presence of a large beam tube in a coaxial resonant cavity does not affect the accelerating performance. This enables effective HOM damping while maintaining a high shunt impedance in a NC cavity. The numerical simulation results show that a compact copper cavity with effective HOM damping and excellent RF properties has been achieved.
DOI •	reference for this paper ※ doi:10.18429/JACoW-FLS2023-WE4P33
About •	Received ※ 23 August 2023 — Revised ※ 30 August 2023 — Accepted ※ 01 September 2023 — Issued ※ 02 December 2023
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WE4P36	The Cryogenic Undulator Upgrade Programme at Diamond Light Source	211
	Z. Patel, W. Cheng, A. George, S.H. Hale, R. Mercado, A. Ramezani Moghaddam, M. Reeves, G. Sharma, S. Tripathi DLS, Oxfordshire, United Kingdom M.V. Marziani University of Cape Town, Cape Town, South Africa
	Diamond Light Source has installed four 2 m long, 17.6 mm period Cryogenic Permanent Magnet Undulators (CPMUs) as upgrades for crystallography beamlines since 2020, with two more planned within the next year. The CPMUs provide 2 - 3 times more brightness and 2 - 4 times more flux than the pure permanent magnet (PPM) devices they are replacing. They have been designed, built, and measured in-house. All four have a 4 mm minimum operating gap and are almost identical in their construction: the main difference being an increase in the number of in-vacuum magnet beam support points from four to five, between CPMU-1 and CPMUs 2 - 4, to better facilitate shimming, particularly at cold temperatures. The ability to shim at cryogenic temperatures necessitated the development of an in-vacuum measurement system. The details of the measurement system will be presented alongside the mechanical and cryogenic design of the undulators; including issues with the magnet foils, and the shimming procedures and tools used to reach the tight magnetic specifications at room temperature and at 77 K.
	Poster WE4P36 [1.656 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-FLS2023-WE4P36
About •	Received ※ 23 August 2023 — Revised ※ 29 August 2023 — Accepted ※ 31 August 2023 — Issued ※ 02 December 2023
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WE4P37	Laser Interferometer for Hall Probe Alignment and Measurement of Undulator	215
	S.M. Khan, G. Mishra Devi Ahilya University, Indore, India M. Gehlot DESY, Hamburg, Germany S. Mishra Devi Ahilya Vishwa Vidyalaya, Institute of Engineering & Technology, Indore, India
	In the Hall probe Magnetic measurement method the field mapping is done along the length of the undulator. The field integral and phase error computed from the field mapping works as the figure of merit of the undulator. In this paper, we discuss the working of a laser interferometer for precise Hall probe alignment. A new user friendly software based on MATLAB has been developed. The phase error and magnetic field integrals are calculated for both taper and untaper U50 undulator of the Laser and Insertion Device Application (LIDA) Laboratory.
DOI •	reference for this paper ※ doi:10.18429/JACoW-FLS2023-WE4P37
About •	Received ※ 22 August 2023 — Revised ※ 22 August 2023 — Accepted ※ 31 August 2023 — Issued ※ 02 December 2023
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WE4P38	Pulsed Wire Measurement of 20 mm Period Hybrid Undulator and Effects of Dispersion	218
	S.M. Khan, G. Mishra Devi Ahilya University, Indore, India M. Gehlot DESY, Hamburg, Germany
	In the pulsed wire method, a thin wire is stretched along the undulator axis with a sensor located near the undulator end. When a current flows through the wire, the Lorentz force on the wire sets up a travelling wave that is picked up by a sensor. Sensor output v. time gives the field integral v. position along the undulator length. We investigate pulsed wire measurements of field integrals and phase error of a 20 mm-period, 500 mm-long undulator and discuss variation in performance with Hall probe data, without any dispersion correction algorithm. Dispersion in the wire introduces dispersion corrected pulse lengths for the field integral measurements. Two field integrals of the undulator were measured with an accuracy close to 2 Gcm and 2 Gcm² with the Hall probe result. The contributions of dispersion to the phase error of the undulator are analyzed. The dispersion assisted phase advance in the undulator in the pulsed wire is measured with a higher slope in comparison to the Hall probe data. Dispersion limited optical phase growth along the undulator length causes period length fluctuations and yields a discrepancy in the phase error computation in comparison to Hall probe data.
DOI •	reference for this paper ※ doi:10.18429/JACoW-FLS2023-WE4P38
About •	Received ※ 22 August 2023 — Revised ※ 22 August 2023 — Accepted ※ 31 August 2023 — Issued ※ 02 December 2023
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WE4P39	Larmor Radius Effect on IFEL Accelerator With Staggered Undulator	221
	R. Khullar, S.M. Khan, G. Mishra Devi Ahilya University, Indore, India
	In this paper, the theory of inverse free electron (IFEL) accelerator using staggered undulator has been discussed. The important contribution of staggered undulator parameter and the finite larmour radius effect on energy saturation, saturation length and accelerating gradient of the IFEL accelerator are included in the analysis. Considering the synchrotron radiation losses, the IFEL accelerator equations are derived. Key words- undulator, inverse free electron laser accelerator, accelerator
	Poster WE4P39 [0.786 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-FLS2023-WE4P39
About •	Received ※ 23 August 2023 — Revised ※ 30 August 2023 — Accepted ※ 01 September 2023 — Issued ※ 02 December 2023
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TH1D1	Application of Superconducting Undulator Technology for Hard X-ray Production at European XFEL
	B. Marchetti, S. Abeghyan, J.E. Baader, S. Casalbuoni, M. Di Felice, U. Englisch, G. Geloni, V. Grattoni, D. La Civita, C. Lechner, S. Serkez, H. Sinn, M. Vannoni, M. Yakopov, P.Z. Ziolkowski EuXFEL, Schenefeld, Germany S. Barbanotti, W. Decking, H.-J. Eckoldt, A. Hauberg, K. Jensch, S. Lederer, L. Lilje, S. Liu, R. Ramalingam, T. Schnautz, R. Wichmann, T. Wohlenberg, I. Zagorodnov, R. Zimmermann DESY, Hamburg, Germany A.W. Grau KIT, Karlsruhe, Germany A.T. Potter Cockcroft Institute, Warrington, Cheshire, United Kingdom A.T. Potter The University of Liverpool, Liverpool, United Kingdom
	The advancement of superconducting undulator (SCU) technology is of strategic importance for the future development of the European XFEL facility. To build the know-how to implement superconducting undulators for its future upgrades, several projects are ongoing: a prototype SCU module (S-PRESSO) for an afterburner in the hard X-ray undulator line SASE2 is being procured; two test stands (SUNDAE1 and SUNDAE2) for the characterization of SCU are being developed; advanced SCU coils are designed and manufactured in house. In this presentation, we describe the status and plans of those projects and highlight their expected performances.
	Slides TH1D1 [2.645 MB]
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TH1D2	A Bulk Superconductor and its Application to Insertion Devices	224
	T. Kii Kyoto University, Kyoto, Japan
	Funding: This work was supported by KAKENHI JP17H01127 and JP22H03870 High-field short-period undulator will be one of the key technologies for the future light sources. Various approaches have been continued under the limitation of materials for permanent/superconducting magnets. A use of bulk superconductor is attractive for its high current density under existence of high magnetic field. The critical current density for rare-earth barium copper oxide (REBCO) bulk superconductor exceeds 10 kA/mm2 even at 10 K in a field range below about 3 T and exceeds 20 kA/mm2 at 4.2 K. In order to utilize the quite high current density in the bulk REBCO and to generate periodic magnetic field we proposed bulk superconductor staggered array undulator in 2006. Recently we have developed the third undulaor prototype which consists of 6T solenoid and 6 period of bulk REBCO array, and successfully demonstrated periodic field amplitude of 2.22 T for period length of 10 mm and undulator gap of 4.0 mm at 7 K. In the presentation, we will summarize properties and performances of bulk REBCO superconductors and discuss on the performance of bulk superconductor staggered array undulator and potential as an insertion device for the future light sources. T. Kii et al.: Proc. FEL2006 (2006) p. 653.
	Slides TH1D2 [2.682 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-FLS2023-TH1D2
About •	Received ※ 22 August 2023 — Revised ※ 23 August 2023 — Accepted ※ 31 August 2023 — Issued ※ 02 December 2023
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TH1D3	SCU Development at the LCLS for Future FELs
	P. Krejcik, G.J. Bouchard, G.L. Gassner, Z. Huang, E.M. Kraft, B. Lam, M.A. Montironi, C.D. Nantista, D.C. Nguyen, H.-D. Nuhn, Z.R. Wolf, Z. Zhang SLAC, Menlo Park, California, USA J.M. Byrd, J.D. Fuerst, E. Gluskin, Y. Ivanyushenkov, M. Kasa, M.F. Qian, Y. Shiroyanagi ANL, Lemont, Illinois, USA X. Permanyer ESS, Lund, Sweden
	A joint SLAC/ANL development program is underway at the LCLS to demonstrate the advantages of SCUs for FEL beamlines. SCUs offer significant advantages for future FEL beam lines in gain length, wavelength reach, and tunability. The program leverages the storage ring SCUs developed at ANL and addresses the issues of integration in FELs and attaining the necessary micron precision for BBA. Our new modular cryomodule design is extendable to a full-length FEL and integrates the additional FEL components such as the phase shifter, quadrupole and RFBPM into the cold mass to achieve a high packing fraction and minimize the average gain length. Initially, 2 such cryomodules will be installed as afterburners at the end of the existing hard x-ray FEL beam line at the LCLS in order to measure the gain length and validate the beam based alignment procedure based on precision motion control of the cold mass internal to the cryomodule. We report on the status of the testing of these critical components on our precision alignment test stand, and discuss future plans for multiple FEL beamlines to be housed in a single cryomodule as part of the future LCLS expansion program for more user stations.
	Slides TH1D3 [2.384 MB]
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TH1D4	Bi-periodic Undulator: Innovative Insertion Device for SOLEIL II	228
	A. Potet, F. Blache, P. Brunelle, M.-E. Couprie, O. Marcouillé, A. Mary, T. Mutin, A. Nadji, K. Tavakoli, C. de Oliveira SOLEIL, Gif-sur-Yvette, France
	SOLEIL II project will lead to optimize the production of photons by a modification of the present facility. The storage ring will be redesigned to reduce electron beam emittance, increase photon beam flux and brightness, and improve beamline resolution. The number of magnetic elements will be increased and the space reserved for insertion devices will be decreased by 30%. SOLEIL magnetic group searches for solutions to generate different magnetic periods in a smaller space to maintain the full spectral domain. Bi-Periodic undulator is an innovative and compact device allowing the use of two selectable magnetic periodicities by superimposition of magnets. The magnetic period can be switched from one value to its triple value by mechanical shift of magnetic arrays. A magnetic design has been performed and the construction of a prototype, including magnetic measurements and corrections, is under progress. The prototype will be installed in the storage ring with the goal to verify the feasibility of the model and to characterize the system. The magnetic fields, the radiation produced and the electron beam dynamics will be considered to have a complete knowledge on this undulator.
	Slides TH1D4 [2.442 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-FLS2023-TH1D4
About •	Received ※ 23 August 2023 — Revised ※ 26 August 2023 — Accepted ※ 31 August 2023 — Issued ※ 02 December 2023
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TH3D2	Radiation Protection Issues in Undulator Upgrades for the European XFEL	245
	A.T. Potter, A. Wolski The University of Liverpool, Liverpool, United Kingdom S. Casalbuoni, S. Karabekyan, H. Sinn, F. Wolff-Fabris EuXFEL, Schenefeld, Germany W. Decking, A. Leuschner, S. Liu DESY, Hamburg, Germany F. Jackson STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
	European XFEL is the first free electron laser operating at MHz repetition rate with electron beam energy up to 17.5 GeV. The high repetition rate together with the high electron beam energy provides unique opportunities for users in different domains. To further extend the operation schemes, some upgrades have already been implemented and several more are planned. The advanced operation schemes may require devices inserted into the beam like slotted foil or narrow vacuum chambers such as for the corrugated structure, the Apple-X undulator, and the superconducting undulator. Due to the high beam power generated by the superconducting linac, there are concerns about increased radiation loads. Therefore, simulations and measurements have been carried out to study the radiation dose rates that may be generated. We give an overview of the simulations and measurements for the above mentioned schemes.
DOI •	reference for this paper ※ doi:10.18429/JACoW-FLS2023-TH3D2
About •	Received ※ 30 August 2023 — Revised ※ 31 August 2023 — Accepted ※ 01 September 2023 — Issued ※ 02 December 2023
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TH3D3	How Can Machine Learning Help Future Light Sources?	249
	A. Santamaria Garcia, E. Bründermann, M. Caselle, A.-S. Müller, L. Scomparin, C. Xu KIT, Karlsruhe, Germany G. De Carne Karlsruhe Institute of Technology (KIT), Eggenstein-Leopoldshafen, Germany
	Machine learning (ML) is one of the key technologies that can considerably extend and advance the capabilities of particle accelerators and needs to be included in their future design. Future light sources aim to reach unprecedented beam brightness and radiation coherence, which require challenging beam sizes and accelerating gradients. The sensitive designs and complex operation modes that arise from such demands will impact the beam availability and flexibility for the users, and can render future accelerators inefficient. ML brings a paradigm shift that can re-define how accelerators are operated. In this contribution we introduce the vision of ML-driven facilities for future accelerators, address some challenges of future light sources, and show an example of how such methods can be used to control beam instabilities.
	Slides TH3D3 [5.398 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-FLS2023-TH3D3
About •	Received ※ 23 August 2023 — Revised ※ 25 August 2023 — Accepted ※ 31 August 2023 — Issued ※ 02 December 2023
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TH3D4	DFCSR: A Fast Calculation of 2D/3D Coherent Synchrotron Radiation in Relativistic Beams
	J. Tang, Z. Huang, G. Stupakov SLAC, Menlo Park, California, USA
	Coherent Synchrotron Radiation (CSR) is regarded as one of the most important reasons that limits beam brightness in modern accelerators. Current numerical packages containing CSR wake fields generally use 1D models, which can become invalid in electron beams with very high brightness. On the other hand, the existing 2D or 3D codes are often slow. Here we report DFCSR, a novel particle tracking code that can simulate 2D/3D CSR and space charge wakes in relativistic electron beams 2 or 3 orders of magnitude faster than conventional models like CSRtrack. We performed benchmark simulations based on FACET-II beams, where electron beams are compressed to reach 300 kA peak current. The tracking code is written in Python and C programming languages with human-friendly input styles and is open-sourced on GitHub. It can serve as a powerful simulation tool for the design of next-generation accelerators.
	Slides TH3D4 [2.598 MB]
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TH3D5	Building Digital Models with thor_scsi: An Evolutionary Approach
	W. Sulaiman Khail, P. Goslawski, P. Schnizer HZB, Berlin, Germany
	Tracy is used as a computing core for digital models for synchrotron light sources since SLS. It inspired the accelerator toolbox, which is using (largely) Tracy’s Hamiltonian propagators. This Tracy code was refactored using modern software paradigms. It started with the Tracy III code base, reorganized its structure, and rebased it on a modern (cx+2a) coding style next to well-tested math libraries: but it is still using the tested Tracy propagators and code. This new code was renamed to thor-scsi, as its API was significantly reworked from the ones that Tracy II has established. Furthermore, a modern Python interfaces is provided, which is is based on pybind11. This new interface allows implementing beam line components using the Python language or tracking state spaces using truncated power series. Digital shadows or twins are essential ingredients for building 4th generation light sources. Based on the modernized thor_scsi code we built an EPICS IOC exporting required thor_scsi externals as EPICS variables. While it focuses on HZB’s current BESSY II and MLS, it is designed flexibly to extend to the BESSY III and MLS II project or similar light sources.
	Slides TH3D5 [1.038 MB]
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TH4D1	Overview and Challenges of the Vacuum Systems of Diffraction Limited Storage Rings
	M.J. Grabski, E. Al-Dmour MAX IV Laboratory, Lund University, Lund, Sweden
	Three diffraction limited storage rings are operational and over ten are in design or construction, several approaches were adapted for the design of their vacuum systems, with the majority have to manage common challenges to achieve the design parameters of those machines. Here we will present the various design approaches adapted by the various facilities together with the challenges and solutions deployed.
	Slides TH4D1 [4.682 MB]
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TH4D2	An Ultra-high Vacuum, High-gradient RF Gun and Advanced Photocathode Studies
	R.K. Li, H.B. Chen, Y.C. Du, P.W. Huang, W.-H. Huang, J.R. Shi, C.-X. Tang, X.-Y. Zhang, L.M. Zheng TUB, Beijing, People’s Republic of China
	Funding: Work supported by the National Key Research and Development Program of China No. 2022YFA1603400 and the Tsinghua University Initiative Scientific Research Program No. 20197050028, 20191081195. Photoinjectors are critical in defining the beam brightness and lasing performance of linac-based light sources. To further improve photoinjectors, one of the promising R&D opportunities is to combine high acceleration gradient with advanced photocathodes that feature low MTE, high QE, and visible light excitation, but unfortunately stringent vacuum conditions. Here we report on developing a new type of high-gradient S-band photocathode rf gun that can achieve one order of magnitude improvement of the vacuum level at the cathode and thus utilize various advanced semiconductor photocathodes. This gun serves as a testbed for exploring high-gradient-compatible photocathodes and new paradigms for optimizing and operating photoinjectors that enhance future light sources.
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TH4D3	Status of Advanced Photocathodes for SRF Guns
	R. Xiang HZDR, Dresden, Germany
	As well known, the quality of the photocathodes is critical for the stability and reliability of photo-injector operation. Especially for the superconducting rf guns, the photocathode is one of the most important parts. In last years, thanks to the developed photocathode technology, several SRF guns were successfully operated or tested for the beam generation at kHz-MHz repetition rate. In this review, the achievements as well as open questions for the cathode requirements of the reliable SRF gun operation will be reviewed, and the possible improvement from photocathodes point of view for the future application will be discussed.
	Slides TH4D3 [2.727 MB]
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FR2M1	Summary Report of Working Group D: Key Technologies
	J.A. Clarke STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom D.B. Bazyl DESY, Hamburg, Germany S. Casalbuoni EuXFEL, Schenefeld, Germany O. Marcouillé SOLEIL, Gif-sur-Yvette, France N. Nishimori QST, Tokai, Japan
	The paper highlights the key points arising from five insightful and instructive working group sessions.
	Slides FR2M1 [10.806 MB]
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Paper

Title

Page

MO1L4

The Challenges and Benefits of Increased Application of Permanent Magnets to Future Light Sources

J. Chavanne
ESRF, Grenoble, France

New storage ring based light sources have been recently constructed or are planned with the aim to reduce the horizontal emittance of the electron beam by about two orders of magnitude. It leads to a considerable increase of the brilliance of the photon beams produced at the sources installed around the storage ring. In many cases theses developments correspond to the upgrades of existing third generation facilities. The resulting accelerator lattice is a very compact arrangement of different types of magnets with demanding field properties. In addition, the need to provide energy saving solutions comes as an additional boundary condition. In this context, it looks obvious that Permanent Magnets (PMs) have been and are considered as an interesting alternative to conventional electromagnets. The ESRF Extremely Brilliant Source (EBS) in operation since beginning of 2020 is an example of the successful implantation of PM dipoles. For the majority of ongoing upgrades PMs corresponds to a large fraction of the storage ring magnets. They presently include dipole, quadrupole or combined dipole quadrupole structures. However, for PMs there is a number of specific difficulties to be addressed. These include for example the need to reach the absolute field strength for device which are not tuneable, the thermal stability or the long term stability. These different subjects will be discussed in the light of the EBS experience and the progresses made at several facilities with planned upgrades.

Slides MO1L4 [3.932 MB]

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TU3D1

Developments in SRF Technology for Light Source Applications

D. Gonnella
SLAC, Menlo Park, California, USA

Funding: US DoE
Significant developments in SRF technology have occurred in the last 5 years motivated by interest in light sources and future colliders. Specifically, LCLS-II and LCLS-II-HE at SLAC have driven high gradient and high Q₀ R&D in SRF across the field. New understandings in doping protocols, cavity processing, and clean room procedures have enabled cryomodules to be constructed that reach previously unattainable performance. Further developments in novel cavity processing methods such as mid-temperature baking and alternate materials such as niobium-3-tin enable a new range of operations for future accelerators. Early operations from LCLS-II and EU-XFEL show that SRF technology is already being used to produce world class light source facilities. Here we present a review of the latest developments in SRF technology both in the R&D phase and in newly installed accelerators and their impact on future light source development and performance.

Slides TU3D1 [5.769 MB]

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TU3D2

Highly Reliable RF Power Sources for Improvement of the Accelerator Availability

M. Lau
TRUMPF Huettinger GmbH, Freiburg, Germany

The trend in exchanging established tube technolo-gy by solid-state based RF power amplifier for particle accelerators around the world is ongoing. Since the first installations* of such amplifier systems several concepts were developed and installed**. As the RF sources are key for the accelerator availability their reliability plays a crucial role. This needs to be considered during the design phase of the overall amplifier system architecture in a new way compared to the tube technology. For tubes it is straight forward as usually one tube powers one or more cavities due to the high power provided. But this also bears the risk of a single point of failure despite the need of high voltage power supplies, continuous degradation and their availability, just to mention the most important aspects. For solid-state power amplifier many transistor units need to be combined for delivering the needed RF power to each cavity. The combining concepts and the overall system architecture finally determine the possibility of de-rating options and redundancy of transistors for compensation of failed units within the system, and thus the overall availability. Our concept for com-bining several transistors in amplifier units*** and assembling these units into racks recently has proven an outstanding performance. For 8,419 hours of opera-tional time, we had a total of 13.9 hours for not being available due to incidents. This results in a total system availability of ~99.83% for more than 980 operational amplifier units at customer site. Here, we want to demonstrate our system architec-ture and the design aspects we considered for reaching this high performance. We think that this is a crucial contribution for bringing this technology one step further to maturity.
* R. Lopes et al., CWRF08, CERN Geneva, March 2008
** E. Montesinos, I.FAST Accelerator-Industry Workshop, CERN, May, 2022
*** M. Lau et al., HIAT Conference, Darmstadt, Germany, 2022

Slides TU3D2 [5.323 MB]

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TU3D3

Application of Cryo-copper Accelerating Structures Towards Future Light Sources

E.A. Nanni
SLAC, Menlo Park, California, USA

Cryogenic operation of copper accelerating structures results in increase accelerating gradients and reduced rf power requirements. The combination of cryogenic operation with distributed coupling accelerator topologies further enhances the flexibility of the designer in optimizing the performance of the accelerator. The combination of these advances creates the possibility of generating high-brightness beams in compact footprints (up to 250 MeV/m accelerating gradients). To date this technology has been explored primarily in the context of a future high energy physics facility. In this talk we will present the study of a new concept for a high gradient, high power accelerator with beam characteristics suitable to study the Higgs boson, the Cool Copper Collider (C3). We will present the latest demonstrated performance of prototype accelerators and highlight the future development path for C3 accelerator technology. In particular, we will focus on benefits to future light source concepts to decrease machine size, increase repetition rate, enable multi-bunch operation and preserve high brightness beams. Possible use cases for future light sources will be presented.

Slides TU3D3 [6.783 MB]

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TU3D4

Compact HOM-damped RF Cavity for a Next Generation Light Source

74

H. Ego
KEK, Ibaraki, Japan
T. Asaka, N. Nishimori
QST, Sendai, Miyagi, Japan
T. Inagaki, H. Tanaka
RIKEN SPring-8 Center, Hyogo, Japan
T. Ohshima, T. Tomai, H. Yamaguchi
JASRI, Hyogo, Japan

A beam-accelerating RF cavity with a new HOM-damping structure was designed in order to suppress coupled-bunch instabilities in a next generation light source with an ultra-low emittance and supplying X-rays approaching their diffraction limits. The TM020 mode at 509 MHz is selected as a beam-accelerating mode because it has a high Q-value of 60,000 and a shunt impedance sufficient for beam acceleration and brings a compact HOM-damping structure to the cavity differently from massive types of cavities with waveguides or pipes extracting HOM power. Two shallow slots are cut on the cavity inner-wall and materials absorbing RF waves are directly fitted into them. They work as HOM dampers without affecting the RF properties of the beam-accelerating mode. A prototype cavity of OFHC copper was fabricated to demonstrate the HOM-damping and generating an accelerating voltage of 900 kV in the cavity. Since the cavity was successful in operation up to 135 kW, the feasibility of both the high-power operation and the damping structure was proved. Four actual cavities were produced and installed to the new 3-GeV synchrotron radiation facility, NanoTerasu in Japan.

Slides TU3D4 [8.581 MB]

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reference for this paper ※ doi:10.18429/JACoW-FLS2023-TU3D4

About •

Received ※ 22 August 2023 — Revised ※ 23 August 2023 — Accepted ※ 31 August 2023 — Issued ※ 02 December 2023

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TU3D5

Electron RF Injectors for Next Generation FELs

B.L. Militsyn
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

A modern trend in the next generation of X-ray Free Electron Lasers (FEL) is the development of tools for the investigation of dynamic processes on the (sub)atomic scale that requires photon beams with energies of 20-25 keV with a repetition rate of 1 MHz or higher. At reasonable energies of the drive linac of 8-10 GeV optimum FEL performance requires an electron beam with emittance of 0.1 mm.mrad or lower. Higher value of the emittance leads to essential degradation in FEL performance and significant increase in required undulator length. In this work we try to estimate the ultimate beam brightness and bunch repetition rate that may be achieved with existing electron injector technologies and outline possible ways of obtaining beams with the parameters required for future FELs. In particular, we will discuss possible injector designs for the ongoing UK XFEL project.

Slides TU3D5 [3.260 MB]

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WE1L3

Enabling Technology Towards Multiline Compact XFELs

J.M. Byrd
ANL, Lemont, Illinois, USA

After almost 15 years of openation, XFELs are well-established light sources for addressing many problems in science. However, most FEL facilities are relatively large to reach the beam energies and geometric emittancs needed to lase at higher photon energy. Furthermore, the XFEL can only serve one or a few users at at time. At Argonne National Laboratory, we have initiated a research program to address some of these issues. We report on our program develop independent undulator arrays to allow more simultaneous users. We are developing a compact Adjustable Phase Undulator that have a compact transverse footprint and a superconducting undulator design with multiple undulators per cryostat. In addition, we report on a new concept for an ultrolow emittance electron gun which reaches fields several times higher than existing guns. This is achieved by generating <10 nsec RF pulses similar to other two-beam accelerator concepts.

Slides WE1L3 [3.183 MB]

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WE1L4

Operating Liquid MetalJet X-ray Sources for Materials Research

159

M. Boin, D. Apel, F. García-Moreno, C. Genzel, P.H. Kamm, M. Klaus, R. Mainz, G. Wagener, R.C. Wimpory
HZB, Berlin, Germany

Even on the 100th anniversary of the death of Wilhelm Conrad Röntgen, the demand for applications of his discovery of X-rays is not diminishing. On the contrary, both academic and industrial research and development need X-ray generating devices with ever-improving properties more than ever to meet the current challenges of science and technology. For this reason, the development of next-generation synchrotrons is being driven forward and made available to users worldwide. Nevertheless, the availability of synchrotron beamtime will always remain limited, even with the most brilliant sources for ultra-fast and high-throughput experiments. That is why the operation of and research with decentralized laboratory equipment becomes just as important. This presentation will therefore focus on the latest developments in laboratory sources in the hard X-ray regime for materials research. In this context, Helmholtz-Zentrum Berlin (HZB) has commissioned EXCILLUM’s new high-flux MetalJet X-ray devices providing photon energies up to 70 keV and 160 keV, respectively. The presentation will give a summary of the technical specifications of these sources utilizing a liquid metal as anode material and the diffractometer lab installations operated with them at HZB. Selected experimental examples are shown providing an overview of applications performed at the MetalJet measuring stations - ranging from residual stress analysis on technical parts to real-time measurements on thin films for photovoltaics applying angle- and energy-dispersive diffraction as well as studies in the field of time-resolved imaging. A comparison to synchrotron measurements is made to benchmark the performance of the available setups. In conclusion, the effort and expenses required to operate such X-ray devices for in-house research and user service measurements are summarized.

Slides WE1L4 [3.423 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-FLS2023-WE1L4

About •

Received ※ 23 August 2023 — Revised ※ 29 August 2023 — Accepted ※ 30 August 2023 — Issued ※ 02 December 2023

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WE3D1

Femtosecond Synchronization of Large Scale FELs - Achievements, Limitations and Mitigation Paths

H. Schlarb, M.K. Czwalinna, S. Schulz
DESY, Hamburg, Germany

Over the past decade, synchronization of large-scale accelerators has advanced from picosecond stability reaching nowadays few femtoseconds only. Driver behind these developments are Free-Electron Lasers, requiring high electron beam compression factor for lasing and the production of ultra-short photon pulses for precision time-evolution experiments in pump-probe laser arrangements. The high control demand of FELs on their electron beam phase space and arrival time triggered a series of key technology development in the accelerator community. These developments span for state-of-the-art RF components, pushing the limits on precision RF cavity control, ultra-stable optical reference distributions to novel new beam diagnostic techniques, all aiming to reach femtosecond beam and pump-probe stabilities. In this presentation, an introduction to key elements causing beam arrival time instabilities and synchronization losses is given. Using EuXFEL and FLASH at example, achievable performance with currently available technologies are summarized. Limitations towards single digit femtosecond or even attosecond synchronization are discussed together with possible mitigation paths.

Slides WE3D1 [7.362 MB]

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WE3D2

Advanced Electron Beam Diagnostics for FELs

P. Krejcik
SLAC, Menlo Park, California, USA

The critical electron beam instrumentation needs for FELs are identified - high-resolution beam position and alignment, emittance and energy spread, and longitudinal profile measurements. The performance limitations for each are discussed and state-of-the-art techniques from several FEL light source facilities will be presented. New challenges for integrating instrumentation in SC undulators are also addressed. A survey of proposals for advanced techniques will be included, especially those focusing on sub-fs resolution for longitudinal measurements and synchronization for attosecond science.

Slides WE3D2 [4.554 MB]

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WE3D3

Beam Diagnostics for Ultra-low Emittance Storage Rings

V. Schlott
PSI, Villigen PSI, Switzerland

Multi-bend achromat (MBA) lattices have enabled the realization of ultra-low emittance storage rings as diffraction-limited synchrotron radiation sources providing much higher photon brilliance and coherence in the wavelength range of hard x-rays than third generation user facilities. While advances in technology and continuous upgrading of state-of-the-art diagnostics systems have already led to outstanding performance levels of beam instrumentation at the present generation of light sources, more stringent demands on beam stability and control induce a number of technical improvements and stimulate advanced concepts of combining electron and photon beam-based signals. Based on diagnostics requirements for diffraction-limited light sources, this talk will give an overview of new electron and photon beam instrumentation developments and highlight beam stabilization concepts aiming for the exploitation of the full capacity of fourth generation synchrotron radiation user facilities.

Slides WE3D3 [3.746 MB]

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WE4P33

Design of a 166.6 MHz HOM Damped Copper Cavity for the Southern Advanced Photon Source

207

J.Y. Zhu, X. Li, Z.J. Lu
IHEP, Beijing, People’s Republic of China
J.B. Yu
IHEP CSNS, Guangdong Province, People’s Republic of China

Funding: This work was supported by the National Natural Science Foundation of China (12205168).
The Southern Advanced Photon Source (SAPS) aims to achieve ultra-low emittances and is expected to adopt low-frequency cavities (< 200 MHz) to accommodates on-axis injection. This paper focuses on the design of a 166.6 MHz HOM-damped normal conducting (NC) cavity for the SAPS. We propose a novel approach to achieve efficient HOM damping by optimizing the lowest frequency HOM and implementing a beam-line absorber in a coaxial resonant NC cavity. Notably, unlike beam-line absorbers for conventional NC cavities, the presence of a large beam tube in a coaxial resonant cavity does not affect the accelerating performance. This enables effective HOM damping while maintaining a high shunt impedance in a NC cavity. The numerical simulation results show that a compact copper cavity with effective HOM damping and excellent RF properties has been achieved.

DOI •

reference for this paper ※ doi:10.18429/JACoW-FLS2023-WE4P33

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Received ※ 23 August 2023 — Revised ※ 30 August 2023 — Accepted ※ 01 September 2023 — Issued ※ 02 December 2023

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WE4P36

The Cryogenic Undulator Upgrade Programme at Diamond Light Source

211

Z. Patel, W. Cheng, A. George, S.H. Hale, R. Mercado, A. Ramezani Moghaddam, M. Reeves, G. Sharma, S. Tripathi
DLS, Oxfordshire, United Kingdom
M.V. Marziani
University of Cape Town, Cape Town, South Africa

Diamond Light Source has installed four 2 m long, 17.6 mm period Cryogenic Permanent Magnet Undulators (CPMUs) as upgrades for crystallography beamlines since 2020, with two more planned within the next year. The CPMUs provide 2 - 3 times more brightness and 2 - 4 times more flux than the pure permanent magnet (PPM) devices they are replacing. They have been designed, built, and measured in-house. All four have a 4 mm minimum operating gap and are almost identical in their construction: the main difference being an increase in the number of in-vacuum magnet beam support points from four to five, between CPMU-1 and CPMUs 2 - 4, to better facilitate shimming, particularly at cold temperatures. The ability to shim at cryogenic temperatures necessitated the development of an in-vacuum measurement system. The details of the measurement system will be presented alongside the mechanical and cryogenic design of the undulators; including issues with the magnet foils, and the shimming procedures and tools used to reach the tight magnetic specifications at room temperature and at 77 K.

Poster WE4P36 [1.656 MB]

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reference for this paper ※ doi:10.18429/JACoW-FLS2023-WE4P36

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Received ※ 23 August 2023 — Revised ※ 29 August 2023 — Accepted ※ 31 August 2023 — Issued ※ 02 December 2023

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WE4P37

Laser Interferometer for Hall Probe Alignment and Measurement of Undulator

215

S.M. Khan, G. Mishra
Devi Ahilya University, Indore, India
M. Gehlot
DESY, Hamburg, Germany
S. Mishra
Devi Ahilya Vishwa Vidyalaya, Institute of Engineering & Technology, Indore, India

In the Hall probe Magnetic measurement method the field mapping is done along the length of the undulator. The field integral and phase error computed from the field mapping works as the figure of merit of the undulator. In this paper, we discuss the working of a laser interferometer for precise Hall probe alignment. A new user friendly software based on MATLAB has been developed. The phase error and magnetic field integrals are calculated for both taper and untaper U50 undulator of the Laser and Insertion Device Application (LIDA) Laboratory.

DOI •

reference for this paper ※ doi:10.18429/JACoW-FLS2023-WE4P37

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Received ※ 22 August 2023 — Revised ※ 22 August 2023 — Accepted ※ 31 August 2023 — Issued ※ 02 December 2023

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WE4P38

Pulsed Wire Measurement of 20 mm Period Hybrid Undulator and Effects of Dispersion

218

S.M. Khan, G. Mishra
Devi Ahilya University, Indore, India
M. Gehlot
DESY, Hamburg, Germany

In the pulsed wire method, a thin wire is stretched along the undulator axis with a sensor located near the undulator end. When a current flows through the wire, the Lorentz force on the wire sets up a travelling wave that is picked up by a sensor. Sensor output v. time gives the field integral v. position along the undulator length. We investigate pulsed wire measurements of field integrals and phase error of a 20 mm-period, 500 mm-long undulator and discuss variation in performance with Hall probe data, without any dispersion correction algorithm. Dispersion in the wire introduces dispersion corrected pulse lengths for the field integral measurements. Two field integrals of the undulator were measured with an accuracy close to 2 Gcm and 2 Gcm² with the Hall probe result. The contributions of dispersion to the phase error of the undulator are analyzed. The dispersion assisted phase advance in the undulator in the pulsed wire is measured with a higher slope in comparison to the Hall probe data. Dispersion limited optical phase growth along the undulator length causes period length fluctuations and yields a discrepancy in the phase error computation in comparison to Hall probe data.

DOI •

reference for this paper ※ doi:10.18429/JACoW-FLS2023-WE4P38

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Received ※ 22 August 2023 — Revised ※ 22 August 2023 — Accepted ※ 31 August 2023 — Issued ※ 02 December 2023

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WE4P39

Larmor Radius Effect on IFEL Accelerator With Staggered Undulator

221

R. Khullar, S.M. Khan, G. Mishra
Devi Ahilya University, Indore, India

In this paper, the theory of inverse free electron (IFEL) accelerator using staggered undulator has been discussed. The important contribution of staggered undulator parameter and the finite larmour radius effect on energy saturation, saturation length and accelerating gradient of the IFEL accelerator are included in the analysis. Considering the synchrotron radiation losses, the IFEL accelerator equations are derived.
Key words- undulator, inverse free electron laser accelerator, accelerator

Poster WE4P39 [0.786 MB]

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reference for this paper ※ doi:10.18429/JACoW-FLS2023-WE4P39

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Received ※ 23 August 2023 — Revised ※ 30 August 2023 — Accepted ※ 01 September 2023 — Issued ※ 02 December 2023

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TH1D1

Application of Superconducting Undulator Technology for Hard X-ray Production at European XFEL

B. Marchetti, S. Abeghyan, J.E. Baader, S. Casalbuoni, M. Di Felice, U. Englisch, G. Geloni, V. Grattoni, D. La Civita, C. Lechner, S. Serkez, H. Sinn, M. Vannoni, M. Yakopov, P.Z. Ziolkowski
EuXFEL, Schenefeld, Germany
S. Barbanotti, W. Decking, H.-J. Eckoldt, A. Hauberg, K. Jensch, S. Lederer, L. Lilje, S. Liu, R. Ramalingam, T. Schnautz, R. Wichmann, T. Wohlenberg, I. Zagorodnov, R. Zimmermann
DESY, Hamburg, Germany
A.W. Grau
KIT, Karlsruhe, Germany
A.T. Potter
Cockcroft Institute, Warrington, Cheshire, United Kingdom
A.T. Potter
The University of Liverpool, Liverpool, United Kingdom

The advancement of superconducting undulator (SCU) technology is of strategic importance for the future development of the European XFEL facility. To build the know-how to implement superconducting undulators for its future upgrades, several projects are ongoing: a prototype SCU module (S-PRESSO) for an afterburner in the hard X-ray undulator line SASE2 is being procured; two test stands (SUNDAE1 and SUNDAE2) for the characterization of SCU are being developed; advanced SCU coils are designed and manufactured in house. In this presentation, we describe the status and plans of those projects and highlight their expected performances.

Slides TH1D1 [2.645 MB]

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TH1D2

A Bulk Superconductor and its Application to Insertion Devices

224

T. Kii
Kyoto University, Kyoto, Japan

Funding: This work was supported by KAKENHI JP17H01127 and JP22H03870
High-field short-period undulator will be one of the key technologies for the future light sources. Various approaches have been continued under the limitation of materials for permanent/superconducting magnets. A use of bulk superconductor is attractive for its high current density under existence of high magnetic field. The critical current density for rare-earth barium copper oxide (REBCO) bulk superconductor exceeds 10 kA/mm2 even at 10 K in a field range below about 3 T and exceeds 20 kA/mm2 at 4.2 K. In order to utilize the quite high current density in the bulk REBCO and to generate periodic magnetic field we proposed bulk superconductor staggered array undulator in 2006*. Recently we have developed the third undulaor prototype which consists of 6T solenoid and 6 period of bulk REBCO array, and successfully demonstrated periodic field amplitude of 2.22 T for period length of 10 mm and undulator gap of 4.0 mm at 7 K. In the presentation, we will summarize properties and performances of bulk REBCO superconductors and discuss on the performance of bulk superconductor staggered array undulator and potential as an insertion device for the future light sources.
* T. Kii et al.: Proc. FEL2006 (2006) p. 653.

Slides TH1D2 [2.682 MB]

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reference for this paper ※ doi:10.18429/JACoW-FLS2023-TH1D2

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Received ※ 22 August 2023 — Revised ※ 23 August 2023 — Accepted ※ 31 August 2023 — Issued ※ 02 December 2023

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TH1D3

SCU Development at the LCLS for Future FELs

P. Krejcik, G.J. Bouchard, G.L. Gassner, Z. Huang, E.M. Kraft, B. Lam, M.A. Montironi, C.D. Nantista, D.C. Nguyen, H.-D. Nuhn, Z.R. Wolf, Z. Zhang
SLAC, Menlo Park, California, USA
J.M. Byrd, J.D. Fuerst, E. Gluskin, Y. Ivanyushenkov, M. Kasa, M.F. Qian, Y. Shiroyanagi
ANL, Lemont, Illinois, USA
X. Permanyer
ESS, Lund, Sweden

A joint SLAC/ANL development program is underway at the LCLS to demonstrate the advantages of SCUs for FEL beamlines. SCUs offer significant advantages for future FEL beam lines in gain length, wavelength reach, and tunability. The program leverages the storage ring SCUs developed at ANL and addresses the issues of integration in FELs and attaining the necessary micron precision for BBA. Our new modular cryomodule design is extendable to a full-length FEL and integrates the additional FEL components such as the phase shifter, quadrupole and RFBPM into the cold mass to achieve a high packing fraction and minimize the average gain length. Initially, 2 such cryomodules will be installed as afterburners at the end of the existing hard x-ray FEL beam line at the LCLS in order to measure the gain length and validate the beam based alignment procedure based on precision motion control of the cold mass internal to the cryomodule. We report on the status of the testing of these critical components on our precision alignment test stand, and discuss future plans for multiple FEL beamlines to be housed in a single cryomodule as part of the future LCLS expansion program for more user stations.

Slides TH1D3 [2.384 MB]

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TH1D4

Bi-periodic Undulator: Innovative Insertion Device for SOLEIL II

228

A. Potet, F. Blache, P. Brunelle, M.-E. Couprie, O. Marcouillé, A. Mary, T. Mutin, A. Nadji, K. Tavakoli, C. de Oliveira
SOLEIL, Gif-sur-Yvette, France

SOLEIL II project will lead to optimize the production of photons by a modification of the present facility. The storage ring will be redesigned to reduce electron beam emittance, increase photon beam flux and brightness, and improve beamline resolution. The number of magnetic elements will be increased and the space reserved for insertion devices will be decreased by 30%. SOLEIL magnetic group searches for solutions to generate different magnetic periods in a smaller space to maintain the full spectral domain. Bi-Periodic undulator is an innovative and compact device allowing the use of two selectable magnetic periodicities by superimposition of magnets. The magnetic period can be switched from one value to its triple value by mechanical shift of magnetic arrays. A magnetic design has been performed and the construction of a prototype, including magnetic measurements and corrections, is under progress. The prototype will be installed in the storage ring with the goal to verify the feasibility of the model and to characterize the system. The magnetic fields, the radiation produced and the electron beam dynamics will be considered to have a complete knowledge on this undulator.

Slides TH1D4 [2.442 MB]

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reference for this paper ※ doi:10.18429/JACoW-FLS2023-TH1D4

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Received ※ 23 August 2023 — Revised ※ 26 August 2023 — Accepted ※ 31 August 2023 — Issued ※ 02 December 2023

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TH3D2

Radiation Protection Issues in Undulator Upgrades for the European XFEL

245

A.T. Potter, A. Wolski
The University of Liverpool, Liverpool, United Kingdom
S. Casalbuoni, S. Karabekyan, H. Sinn, F. Wolff-Fabris
EuXFEL, Schenefeld, Germany
W. Decking, A. Leuschner, S. Liu
DESY, Hamburg, Germany
F. Jackson
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

European XFEL is the first free electron laser operating at MHz repetition rate with electron beam energy up to 17.5 GeV. The high repetition rate together with the high electron beam energy provides unique opportunities for users in different domains. To further extend the operation schemes, some upgrades have already been implemented and several more are planned. The advanced operation schemes may require devices inserted into the beam like slotted foil or narrow vacuum chambers such as for the corrugated structure, the Apple-X undulator, and the superconducting undulator. Due to the high beam power generated by the superconducting linac, there are concerns about increased radiation loads. Therefore, simulations and measurements have been carried out to study the radiation dose rates that may be generated. We give an overview of the simulations and measurements for the above mentioned schemes.

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reference for this paper ※ doi:10.18429/JACoW-FLS2023-TH3D2

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Received ※ 30 August 2023 — Revised ※ 31 August 2023 — Accepted ※ 01 September 2023 — Issued ※ 02 December 2023

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TH3D3

How Can Machine Learning Help Future Light Sources?

249

A. Santamaria Garcia, E. Bründermann, M. Caselle, A.-S. Müller, L. Scomparin, C. Xu
KIT, Karlsruhe, Germany
G. De Carne
Karlsruhe Institute of Technology (KIT), Eggenstein-Leopoldshafen, Germany

Machine learning (ML) is one of the key technologies that can considerably extend and advance the capabilities of particle accelerators and needs to be included in their future design. Future light sources aim to reach unprecedented beam brightness and radiation coherence, which require challenging beam sizes and accelerating gradients. The sensitive designs and complex operation modes that arise from such demands will impact the beam availability and flexibility for the users, and can render future accelerators inefficient. ML brings a paradigm shift that can re-define how accelerators are operated. In this contribution we introduce the vision of ML-driven facilities for future accelerators, address some challenges of future light sources, and show an example of how such methods can be used to control beam instabilities.

Slides TH3D3 [5.398 MB]

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reference for this paper ※ doi:10.18429/JACoW-FLS2023-TH3D3

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Received ※ 23 August 2023 — Revised ※ 25 August 2023 — Accepted ※ 31 August 2023 — Issued ※ 02 December 2023

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TH3D4

DFCSR: A Fast Calculation of 2D/3D Coherent Synchrotron Radiation in Relativistic Beams

J. Tang, Z. Huang, G. Stupakov
SLAC, Menlo Park, California, USA

Coherent Synchrotron Radiation (CSR) is regarded as one of the most important reasons that limits beam brightness in modern accelerators. Current numerical packages containing CSR wake fields generally use 1D models, which can become invalid in electron beams with very high brightness. On the other hand, the existing 2D or 3D codes are often slow. Here we report DFCSR, a novel particle tracking code that can simulate 2D/3D CSR and space charge wakes in relativistic electron beams 2 or 3 orders of magnitude faster than conventional models like CSRtrack. We performed benchmark simulations based on FACET-II beams, where electron beams are compressed to reach 300 kA peak current. The tracking code is written in Python and C programming languages with human-friendly input styles and is open-sourced on GitHub. It can serve as a powerful simulation tool for the design of next-generation accelerators.

Slides TH3D4 [2.598 MB]

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TH3D5

Building Digital Models with thor_scsi: An Evolutionary Approach

W. Sulaiman Khail, P. Goslawski, P. Schnizer
HZB, Berlin, Germany

Tracy is used as a computing core for digital models for synchrotron light sources since SLS. It inspired the accelerator toolbox, which is using (largely) Tracy’s Hamiltonian propagators. This Tracy code was refactored using modern software paradigms. It started with the Tracy III code base, reorganized its structure, and rebased it on a modern (cx+2a) coding style next to well-tested math libraries: but it is still using the tested Tracy propagators and code. This new code was renamed to thor-scsi, as its API was significantly reworked from the ones that Tracy II has established. Furthermore, a modern Python interfaces is provided, which is is based on pybind11. This new interface allows implementing beam line components using the Python language or tracking state spaces using truncated power series. Digital shadows or twins are essential ingredients for building 4th generation light sources. Based on the modernized thor_scsi code we built an EPICS IOC exporting required thor_scsi externals as EPICS variables. While it focuses on HZB’s current BESSY II and MLS, it is designed flexibly to extend to the BESSY III and MLS II project or similar light sources.

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TH4D1

Overview and Challenges of the Vacuum Systems of Diffraction Limited Storage Rings

M.J. Grabski, E. Al-Dmour
MAX IV Laboratory, Lund University, Lund, Sweden

Three diffraction limited storage rings are operational and over ten are in design or construction, several approaches were adapted for the design of their vacuum systems, with the majority have to manage common challenges to achieve the design parameters of those machines. Here we will present the various design approaches adapted by the various facilities together with the challenges and solutions deployed.

Slides TH4D1 [4.682 MB]

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TH4D2

An Ultra-high Vacuum, High-gradient RF Gun and Advanced Photocathode Studies

R.K. Li, H.B. Chen, Y.C. Du, P.W. Huang, W.-H. Huang, J.R. Shi, C.-X. Tang, X.-Y. Zhang, L.M. Zheng
TUB, Beijing, People’s Republic of China

Funding: Work supported by the National Key Research and Development Program of China No. 2022YFA1603400 and the Tsinghua University Initiative Scientific Research Program No. 20197050028, 20191081195.
Photoinjectors are critical in defining the beam brightness and lasing performance of linac-based light sources. To further improve photoinjectors, one of the promising R&D opportunities is to combine high acceleration gradient with advanced photocathodes that feature low MTE, high QE, and visible light excitation, but unfortunately stringent vacuum conditions. Here we report on developing a new type of high-gradient S-band photocathode rf gun that can achieve one order of magnitude improvement of the vacuum level at the cathode and thus utilize various advanced semiconductor photocathodes. This gun serves as a testbed for exploring high-gradient-compatible photocathodes and new paradigms for optimizing and operating photoinjectors that enhance future light sources.

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TH4D3

Status of Advanced Photocathodes for SRF Guns

R. Xiang
HZDR, Dresden, Germany

As well known, the quality of the photocathodes is critical for the stability and reliability of photo-injector operation. Especially for the superconducting rf guns, the photocathode is one of the most important parts. In last years, thanks to the developed photocathode technology, several SRF guns were successfully operated or tested for the beam generation at kHz-MHz repetition rate. In this review, the achievements as well as open questions for the cathode requirements of the reliable SRF gun operation will be reviewed, and the possible improvement from photocathodes point of view for the future application will be discussed.

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FR2M1

Summary Report of Working Group D: Key Technologies

J.A. Clarke
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
D.B. Bazyl
DESY, Hamburg, Germany
S. Casalbuoni
EuXFEL, Schenefeld, Germany
O. Marcouillé
SOLEIL, Gif-sur-Yvette, France
N. Nishimori
QST, Tokai, Japan

The paper highlights the key points arising from five insightful and instructive working group sessions.

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