Author: Mueller, A.-S.    [Müller, A.-S.]
Paper Title Page
MOPAB035 Modified Lattice of the Compact Storage Ring in the cSTART Project at Karlsruhe Institute of Technology 159
 
  • A.I. Papash, E. Bründermann, B. Härer, A.-S. Müller, R. Ruprecht, J. Schäfer, M. Schuh
    KIT, Karlsruhe, Germany
 
  A very large acceptance compact storage ring (VLA-cSR) is under design at the Institute for Beam Physics and Technology (IBPT) of the Karlsruhe Institute of Technology (KIT, Germany). The combination of a compact storage ring and a laser wakefield accelerator (LWFA) might be the basis for future compact light sources and advancing user facilities. Meanwhile, the post-LWFA beam should be adapted for storage and accumulation in a dedicated storage ring. Modified geometry and lattice of a VLA-cSR operating at 50 MeV energy range have been studied in detailed simulations. The main features of a new model are described here. The new design, based on 45° bending magnets, is suitable to store the post-LWFA beam with a wide momentum spread (1% to 2%) as well as ultra-short electron bunches in the fs range from the Ferninfrarot Linac- Und Test- Experiment (FLUTE). The DBA-FDF lattice with relaxed settings, split elements, and higher-order optics of tolerable strength allows improving the dynamic aperture to an acceptable level. This contribution discusses the lattice features in detail and different possible operation schemes of a VLA-cSR.  
poster icon Poster MOPAB035 [1.405 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB035  
About • paper received ※ 10 May 2021       paper accepted ※ 27 May 2021       issue date ※ 24 August 2021  
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MOPAB036 Different Operation Regimes at the KIT Storage Ring KARA (Karlsruhe Research Accelerator) 163
 
  • A.I. Papash, M. Brosi, E. Huttel, A. Mochihashi, A.-S. Müller, R. Ruprecht, P. Schreiber, M. Schuh, N.J. Smale
    KIT, Eggenstein-Leopoldshafen, Germany
 
  The KIT storage ring KARA operates in a wide energy range from 0.5 to 2.5 GeV. Different operation modes have been implemented at KARA, so far, the double-bend achromat (DBA) lattice with non-dispersive straight sections, the theoretical minimum emittance (TME) lattice with distributed dispersion, different versions of low-compaction factor optics with highly stretched dispersion function. Short bunches of a few ps pulse width are available at KARA. Low-alpha optics has been simulated, tested and implemented in a wide operational range of the storage ring and is now routinely used at 1.3 GeV for studies of beam bursting effects caused by coherent synchrotron radiation in the THz frequency range. Different non-linear effects, in particular residual high-order components of the magnetic field, generated in high-field superconducting wigglers have been studied and cured. Based on good agreement between computer simulations and experiments, a new operation mode at high vertical tune was implemented. The beam performance during user operation as well as at low-alpha regimes has been improved. A specific optic with negative compaction factor was simulated, tested and is in operation.  
poster icon Poster MOPAB036 [1.477 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB036  
About • paper received ※ 13 May 2021       paper accepted ※ 08 June 2021       issue date ※ 29 August 2021  
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MOPAB037 On Possibility of Alpha-buckets Detecting at the KIT Storage Ring KARA (Karlsruhe Research Accelerator) 167
 
  • A.I. Papash, T. Boltz, M. Brosi, A.-S. Müller, R. Ruprecht, P. Schreiber, M. Schuh, N.J. Smale
    KIT, Karlsruhe, Germany
 
  Computer studies of longitudinal motion have been performed with the objective to estimate the possibility of detection of alpha-buckets at the KIT storage ring KARA (Karlsruhe Research Accelerator). The longitudinal equations of motion and the Hamiltonian were expanded to high order terms of the energy deviation of particles in a beam. Roots of third order equation for three leading terms of momentum compaction factor and free energy independent term were derived in a form suitable for analytical estimations. Averaged quadratic terms of closed orbit distortions caused by misalignment of magnetic elements in a ring lead to orbit lengthening independent of particle energy deviation. Particle transverse excursions were estimated and are taken into account. Simulations have been bench-marked on existing experiments at Metrology Light Source (MLS) in Berlin (Germany) and SOLEIL (France). Parameters of three simultaneous beams and alpha buckets at MLS and SOLEIL have been reproduced with high accuracy. A computer model of KARA was used to predict behavior and the dynamics of possible simultaneous beams in the ring.  
poster icon Poster MOPAB037 [1.269 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB037  
About • paper received ※ 11 May 2021       paper accepted ※ 28 May 2021       issue date ※ 29 August 2021  
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MOPAB164 Miniature, High Strength Transport Line Design for Laser Plasma Accelerator-Driven FELs 561
 
  • S. Fatehi, A. Bernhard, A.-S. Müller, M.S. Ning
    KIT, Karlsruhe, Germany
 
  Funding: This work is supported by the BMBF project 05K19VKA PlasmaFEL (Federal Ministry of Education and Research).
Laser-plasma acceleration is an outstanding candidate to drive the next-generation compact light sources and FELs. To compensate large chromatic effects using novel compact beam optic elements in the beam transport line is required. We aim at designing miniature, high strength, normal conducting and superconducting transport line magnets and optics for capturing and matching LPA-generated electron bunches to given applications. Our primary application case is a demonstration experiment for transverse gradient undulator (TGU) FELs, to be performed at the JETI laser facility, Jena, Germany. In this contribution, we present the current design of the beam transport line magnets and the beam optics calculations.
Laser Plasma Accelerators, FELs, Magnets, Beam Dynamics, Superconductivity, transverse gradient undulator
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB164  
About • paper received ※ 19 May 2021       paper accepted ※ 25 May 2021       issue date ※ 20 August 2021  
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MOPAB280 Split Ring Resonator Experiment - Simulation Results 888
 
  • J. Schäfer, B. Härer, A. Malygin, A.-S. Müller, M. Nabinger, M.J. Nasse, T. Schmelzer, M. Schuh, T. Windbichler
    KIT, Karlsruhe, Germany
 
  Funding: Supported by "Karlsruhe School of Elementary and Astroparticle Physics: Science and Technology (KSETA)" and European Union’s Horizon 2020 Research and Innovation programme.
FLUTE (Ferninfrarot Linac- Und Test-Experiment) is a compact linac-based test facility for accelerator and diagnostics R&D. An example for a new accelerator diagnostics tool currently studied at FLUTE is the split-ring-resonator (SRR) experiment, which aims to measure the longitudinal bunch profile of fs-scale electron bunches. Laser-generated THz radiation is used to excite a high frequency oscillating electromagnetic field in the SRR. Particles passing through the SRR gap are time-dependently deflected in the vertical plane, which allows a vertical streaking of an electron bunch. This principle allows a diagnosis of the longitudinal bunch profile in the femtosecond time domain and will be tested at FLUTE. This contribution presents an overview of the SRR experiment and the results of various tracking simulations for different scenarios as a function of laser pulse length and bunch charge. Based on these results possible working points for the experiments at FLUTE will be proposed.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB280  
About • paper received ※ 19 May 2021       paper accepted ※ 21 June 2021       issue date ※ 01 September 2021  
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MOPAB293 Electro-Optical Diagnostics at KARA and FLUTE - Results and Prospects 927
 
  • G. Niehues, E. Bründermann, M. Caselle, S. Funkner, A.-S. Müller, M.J. Nasse, M.M. Patil, R. Ruprecht, M. Schuh, M. Weber, C. Widmann
    KIT, Karlsruhe, Germany
 
  Funding: S.F. was funded by BMBF contract No. 05K16VKA, C. W. by BMBF contract number 05K19VKD. G.N. and E.B. acknowledge support by the Helmholtz President’s strategic fund IVF "Plasma Accelerators".
Electro-optical (EO) methods are nowadays well-proven diagnostic tools, which are utilized to detect THz fields in countless experiments. The world’s first near-field EO sampling monitor at an electron storage ring was developed and installed at the KIT storage ring KARA (Karlsruhe Research Accelerator) and optimized to detect longitudinal bunch profiles. This experiment with other diagnostic techniques builds a distributed, synchronized sensor network to gain comprehensive data about the phase-space of electron bunches as well as the produced coherent synchrotron radiation (CSR). These measurements facilitate studies of physical conditions to provide, at the end, intense and stable CSR in the THz range. At KIT, we also operate FLUTE (Ferninfrarot Linac- und Test-Experiment), a new compact versatile linear accelerator as a test facility for novel techniques and diagnostics. There, EO diagnostics will be implemented to open up possibilities to evaluate and compare new techniques for longitudinal bunch diagnostics. In this contribution, we will give an overview of results achieved, the current status of the EO diagnostic setups at KARA and FLUTE and discuss future prospects.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB293  
About • paper received ※ 19 May 2021       paper accepted ※ 07 July 2021       issue date ※ 17 August 2021  
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MOPAB294 Implementing Electro-Optical Diagnostics for Measuring the CSR Far-Field at KARA 931
 
  • C. Widmann, E. Bründermann, M. Caselle, S. Funkner, A.-S. Müller, M.J. Nasse, G. Niehues, M.M. Patil, C. Sax, J.L. Steinmann, M. Weber
    KIT, Karlsruhe, Germany
  • C. Mai
    DELTA, Dortmund, Germany
 
  Funding: This work was supported by BMBF ErUM-Pro project 05K19 STARTRAC, C.W. was funded under contract No. 05K19VDK, C.M. under contract No. 05K19PEC, S.F. under contract No. 05K16VKA.
For measuring the temporal profile of the coherent synchrotron radiation (CSR) at the KIT storage ring KARA (Karlsruhe Research Accelerator) an experimental setup based on electro-optical spectral decoding (EOSD) is currently being implemented. The EOSD technique allows single-shot, phase-sensitive measurements of the far-field radiation on a turn-by-turn basis at rates in the MHz range. Therefore, the resulting THz radiation from the dynamics of the bunch evolution, e.g. the microbunching, can be observed with high temporal resolution. This far-field setup is part of the distributed sensor network at KARA. Additionally to the information acquired from the near-field EOSD spectral decoding and the horizontal bunch profile monitor, it enables to monitor the longitudinal phase-space of the bunch. In this contribution, the characterization of the far-field setup is summarized and its implementation is discussed.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB294  
About • paper received ※ 19 May 2021       paper accepted ※ 07 June 2021       issue date ※ 18 August 2021  
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TUPAB087 Full Characterization of the Bunch-Compressor Dipoles for FLUTE 1585
 
  • Y. Nie, A. Bernhard, E. Bründermann, A.-S. Müller, M.J. Nasse, R. Ruprecht, J. Schäfer, M. Schuh, Y. Tong
    KIT, Karlsruhe, Germany
 
  Funding: This work is supported by the BMBF project 05H18VKRB1 HIRING (Federal Ministry of Education and Research).
The Ferninfrarot Linac- Und Test-Experiment (FLUTE) is a KIT-operated linac-based test facility for accelerator research and development as well as a compact, ultra-broadband and short-pulse terahertz (THz) source. As a key component of FLUTE, the bunch compressor (chicane) consisting of four specially designed dipoles will be used to compress the 40-50 MeV electron bunches after the linac down to single fs bunch length. The maximum vertical magnetic field of the dipoles reach 0.22 T, with an effective length of 200 mm. The good field region is ±40 mm and ±10.5 mm in the horizontal and vertical direction, respectively. The latest measurement results of the dipoles in terms of field homogeneity, excitation and field reproducibility within the good field regions will be reported, which meet the predefined specifications. The measured 3D magnetic field distributions have been used to perform beam dynamics simulations of the bunch compressor. Effects of the real field properties on the beam dynamics, which are different from that of the ASTRA built-in dipole field, will be discussed.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB087  
About • paper received ※ 10 May 2021       paper accepted ※ 27 May 2021       issue date ※ 01 September 2021  
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TUPAB163 Developing a 50 MeV LPA-Based Injector at ATHENA for a Compact Storage Ring 1765
 
  • E. Panofski, J. Dirkwinkel, T. Hülsenbusch, A.R. Maier, J. Osterhoff, G. Palmer, T. Parikh, P.A. Walker, P. Winkler
    DESY, Hamburg, Germany
  • C. Braun, T.F.J. Eichner, L. Hübner, S. Jalas, L. Jeppe, M. Kirchen, P. Messner, M. Schnepp, M. Trunk, C.M. Werle
    University of Hamburg, Hamburg, Germany
  • E. Bründermann, B. Härer, A.-S. Müller, C. Widmann
    KIT, Karlsruhe, Germany
  • M. Kaluza, A. Sävert
    HIJ, Jena, Germany
 
  The laser-driven generation of relativistic electron beams in plasma and their acceleration to high energies with GV/m-gradients has been successfully demonstrated. Now, it is time to focus on the application of laser-plasma accelerated (LPA) beams. The "Accelerator Technology HElmholtz iNfrAstructure" (ATHENA) of the Helmholtz Association fosters innovative particle accelerators and high-power laser technology. As part of the ATHENAe pillar several different applications driven by LPAs are to be developed, such as a compact FEL, medical imaging and the first realization of LPA-beam injection into a storage ring. The latter endeavor is conducted in close collaboration between Deutsche Elektronen-Synchrotron (DESY), Karlsruhe Institute of Technology (KIT) and Helmholtz Institute Jena. In the cSTART project at KIT, a compact storage ring optimized for short bunches and suitable to accept LPA-based electron bunches is in preparation. In this conference contribution we will introduce the 50 MeV LPA-based injector and give an overview about the project goals. The key parameters of the plasma injector will be presented. Finally, the current status of the project will be summarized.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB163  
About • paper received ※ 19 May 2021       paper accepted ※ 31 May 2021       issue date ※ 21 August 2021  
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TUPAB251 Impedance Studies of a Corrugated Pipe for KARA 2039
 
  • S. Maier, M. Brosi, A. Mochihashi, A.-S. Müller, M.J. Nasse, M. Schwarz
    KIT, Karlsruhe, Germany
 
  Funding: DFG project 431704792 in the ANR-DFG collaboration project ULTRASYNC and the DFG-funded Doctoral School "Karlsruhe School of Elementary and Astroparticle Physics: Science and Technology".
At the KIT storage ring KARA (KArlsruhe Research Accelerator) it is planned to install an impedance manipulation structure in a versatile chamber to study and eventually control the influence of an additional impedance on the beam dynamics and the emitted coherent synchrotron radiation. For this purpose the impedance of a corrugated pipe is under investigation. In this contribution, we present first results of simulations showing the impact of different structure parameters on its impedance and wake potential.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB251  
About • paper received ※ 19 May 2021       paper accepted ※ 17 June 2021       issue date ※ 26 August 2021  
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TUPAB255 Longitudinal Beam Dynamics and Coherent Synchrotron Radiation at cSTART 2050
 
  • M. Schwarz, E. Bründermann, D. El Khechen, B. Härer, A. Malygin, A.-S. Müller, M.J. Nasse, A.I. Papash, R. Ruprecht, J. Schäfer, M. Schuh, P. Wesolowski
    KIT, Karlsruhe, Germany
 
  The compact STorage ring for Accelerator Research and Technology (cSTART) project aims to store electron bunches of LWFA-like beams in a very large momentum acceptance storage ring. The project will be realized at the Karlsruhe Institute of Technology (KIT, Germany). Initially, the Ferninfrarot Linac- Und Test-Experiment (FLUTE), a source of ultra-short bunches, will serve as an injector for cSTART to benchmark and emulate laser-wakefield accelerator-like beams. In a second stage a laser-plasma accelerator will be used as an injector, which is being developed as part of the ATHENA project in collaboration with DESY and Helmholtz Institute Jena (HIJ). With an energy of 50 MeV and damping times of several seconds, the electron beam does not reach equilibrium emittance. Furthermore, the critical frequency of synchrotron radiation is 53 THz and in the same order as the bunch spectrum, which implies that the entire bunch radiates coherently. We perform longitudinal particle tracking simulations to investigate the evolution of the bunch length and spectrum as well as the emitted coherent synchrotron radiation. Finally, different options for the RF system are discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB255  
About • paper received ※ 17 May 2021       paper accepted ※ 21 June 2021       issue date ※ 29 August 2021  
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TUPAB267 Investigation of Beam Impedance and Heat Load in a High Temperature Superconducting Undulator 2089
 
  • D. Astapovych, H. De Gersem, E. Gjonaj
    TEMF, TU Darmstadt, Darmstadt, Germany
  • T.A. Arndt, E. Bründermann, N. Glamann, A.W. Grau, B. Krasch, A.-S. Müller, R. Nast, D. Saez de Jauregui, A. Will
    KIT, Karlsruhe, Germany
 
  The use of high temperature superconducting (HTS) materials can enhance the performance of superconducting undulators (SCU), which can later be implemented in free electron laser facilities, synchrotron storage rings and light sources. In particular, the short period < 10 mm undulators with narrow magnetic gap < 4 mm are relevant. One of the promising approaches considers a 10 cm meander-structured HTS tapes stacked one above the other. Then, the HTS tape is wound on the SCU. The idea of this jointless undulator has been proposed by, and is being further developed at KIT. Since minimizing the different sources of heat load is a critical issue for all SCUs, a detailed analysis of the impedance and heat load is required to meet the cryogenic system design. The dominant heat source is anticipated to be the resistive surface loss, which is one of the subjects of this study. Considering the complexity of the HTS tape, the impedance model includes the geometrical structure of the HTS tapes as well as the anomalous skin effect. The results of the numerical investigation performed by the help of the CST PS solver will be presented and discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB267  
About • paper received ※ 18 May 2021       paper accepted ※ 26 July 2021       issue date ※ 12 August 2021  
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TUPAB270 Thermal Transition Design and Beam Heat-load Estimation for the COLDDIAG Refurbishment 2097
 
  • H.J. Cha, N. Glamann, A.W. Grau, A.-S. Müller, D. Saez de Jauregui
    KIT, Eggenstein-Leopoldshafen, Germany
 
  Funding: This work is supported by the BMBF project 05H18VKRB1 HIRING (Federal Ministry of Education and Research).
The COLDDIAG (cold vacuum chamber for beam heat load diagnostics) developed at Karlsruhe Institute of Technology has been modified for more studies at cryogenic temperatures different from the previous operations at 4 K in a cold bore and at 50 K in a thermal shield. The key components in this campaign are two thermal transitions connecting both ends of the bore at 50 K with the shield at the same or higher temperature. In this paper, we present design efforts for the compact transitions, allowed heat intakes to the cooling power margin and mechanical robustness in the cryogenic environment. A manufacture scheme for the transition and its peripheral is also given. In addition, the beam heat loads in the refurbished COLDDIAG are estimated in terms of the accelerator beam parameters.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB270  
About • paper received ※ 12 May 2021       paper accepted ※ 02 June 2021       issue date ※ 12 August 2021  
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WEPAB083 Effect of Negative Momentum Compaction Operation on the Current-Dependent Bunch Length 2786
 
  • P. Schreiber, T. Boltz, M. Brosi, B. Härer, A. Mochihashi, A.-S. Müller, A.I. Papash, R. Ruprecht, M. Schuh
    KIT, Karlsruhe, Germany
 
  Funding: Funded by the European Union’s Horizon 2020 Research and Innovation programme, Grant Agreement No 730871. P.S, T.B are supported by DFG-funded Karlsruhe School of Elementary and Astroparticle Physics.
New operation modes are often considered during the development of new synchrotron light sources. An understanding of the effects involved is inevitable for a successful operation of these schemes. At the KIT storage ring KARA (Karlsruhe Research Accelerator), new modes can be implemented and tested at various energies, employing a variety of performant beam diagnostics devices. Negative momentum compaction optics at various energies have been established. Also, the influence of a negative momentum compaction factor on different effects has been investigated. This contribution comprises a short report on the status of the implementation of a negative momentum compaction optics at KARA. Additionally, first measurements of the changes to the current-dependent bunch length will be presented.
 
poster icon Poster WEPAB083 [1.129 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB083  
About • paper received ※ 19 May 2021       paper accepted ※ 01 July 2021       issue date ※ 26 August 2021  
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WEPAB103 Systematic Beam Parameter Studies at the Injector Section of FLUTE 2837
 
  • T. Schmelzer, E. Bründermann, D. Hoffmann, I. Križnar, S. Marsching, A.-S. Müller, M.J. Nasse, R. Ruprecht, J. Schäfer, M. Schuh, N.J. Smale, P. Wesolowski, T. Windbichler
    KIT, Karlsruhe, Germany
 
  Funding: This work is supported by the DFG-funded Doctoral School "Karlsruhe School of Elementary and Astroparticle Physics: Science and Technology (KSETA)"
FLUTE (Ferninfrarot Linac- und Test-Experiment) is a compact linac-based test facility for accelerator R&D and source of intense THz radiation for photon science. In preparation for the next experiments, the electron beam of the injector section of FLUTE has been characterized. In systematic studies the electron beam parameters, e.g., beam energy and emittance, are measured with several diagnostic systems. This knowledge allows the establishment of different operation settings and the optimization of electron beam parameters for future experiments.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB103  
About • paper received ※ 19 May 2021       paper accepted ※ 01 September 2021       issue date ※ 13 August 2021  
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WEPAB135 Progress of the Development of a Superconducting Undulator as a THz Source for FELs 2933
 
  • J. Gethmann, S. Casalbuoni, N. Glamann, A.W. Grau, A.-S. Müller, D. Saez de Jauregui
    KIT, Eggenstein-Leopoldshafen, Germany
  • D. Astapovych, H. De Gersem, E. Gjonaj
    TEMF, TU Darmstadt, Darmstadt, Germany
  • S. Casalbuoni
    EuXFEL, Schenefeld, Germany
 
  Funding: This work is supported by the BMBF project 05K19VK2 SCUXFEL (Federal Ministry of Education and Research) and by the DFG-funded Doctoral School KSETA: Science and Technology.
To produce radiation in the THz frequency range at X-ray Free Electron Lasers, undulators with large period length, high fields, and large gaps are required. These demands can be fulfilled by superconducting undulators. In this contribution, the actual requirements on the main parameters of such a superconducting undulator will be discussed and the progress of the design will be discussed. In addition, beam impedance and heat load results obtained analytically as well as by large-scale wakefield simulations will be presented.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB135  
About • paper received ※ 19 May 2021       paper accepted ※ 02 July 2021       issue date ※ 31 August 2021  
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WEPAB233 Excitation of Micro-Bunching in Short Electron Bunches Using RF Amplitude Modulation 3173
 
  • T. Boltz, E. Blomley, M. Brosi, E. Bründermann, B. Härer, A. Mochihashi, A.-S. Müller, P. Schreiber, M. Schuh, M. Yan
    KIT, Karlsruhe, Germany
 
  In its short-bunch operation mode, the KIT storage ring KARA provides picosecond-long electron bunches, which emit coherent synchrotron radiation (CSR) up to the terahertz frequency range. Due to the high spatial compression under these conditions, the self-interaction of the bunch with its own emitted CSR induces a wake-field, which significantly influences the longitudinal charge distribution. Above a given threshold current, this leads to the formation of dynamically evolving micro-structures within the bunch and is thus called micro-bunching instability. As CSR is emitted at wavelengths corresponding to the spatial dimension of the emitter, these small structures lead to an increased emission of CSR at higher frequencies. The instability is therefore deliberately induced at KARA to provide intense THz radiation to dedicated experiments. To further increase the emitted power in the desired frequency range, we consider the potential of RF amplitude modulations to intentionally excite this form of micro-bunching in short electron bunches. This work is supported by the BMBF project 05K19VKC TiMo (Federal Ministry of Education and Research).  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB233  
About • paper received ※ 19 May 2021       paper accepted ※ 01 July 2021       issue date ※ 17 August 2021  
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WEPAB240 Increasing the Single-Bunch Instability Threshold by Bunch Splitting Due to RF Phase Modulation 3193
 
  • J.L. Steinmann, E. Blomley, M. Brosi, E. Bründermann, A. Mochihashi, A.-S. Müller, M. Schuh, P. Schönfeldt
    KIT, Karlsruhe, Germany
 
  Funding: This work is funded by the BMBF contract number: 05K16VKA.
RF phase modulation at twice the synchrotron frequency can be used to split a stored electron bunch into two or more bunchlets orbiting each other. We report on time-resolved measurements at the Karlsruhe Research Accelerator (KARA), where this bunch splitting was used to increase the threshold current of the microbunching instability, happening in the short-bunch operation mode. Turning the modulation on and off reproducibly affects the sawtooth behavior of the emitted coherent synchrotron radiation.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB240  
About • paper received ※ 19 May 2021       paper accepted ※ 08 July 2021       issue date ※ 18 August 2021  
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WEPAB246 Influence of Different Beam Energies on the Micro-Bunching Instability 3209
 
  • M. Brosi, A.-S. Müller, P. Schreiber, M. Schuh
    KIT, Karlsruhe, Germany
 
  During the operation of an electron synchrotron with short electron bunches, the beam dynamics are influenced by the occurrence of the micro-bunching instability. This collective instability is caused by the self-interaction of a short electron bunch with its own emitted coherent synchrotron radiation (CSR). Above a certain threshold bunch current dynamic micro-structures start to occur on the longitudinal phase space density. The resulting dynamics depend on various parameters and were previously investigated in relation to, amongst others, the momentum compaction factor and the acceleration voltage. In this contribution, the influence of the energy of the electrons on the dynamics of the micro-bunching instability is studied based on measurements at the KIT storage ring KARA (Karlsruhe Research Accelerator).  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB246  
About • paper received ※ 19 May 2021       paper accepted ※ 08 July 2021       issue date ※ 11 August 2021  
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WEPAB289 Machine Learning Based Spatial Light Modulator Control for the Photoinjector Laser at FLUTE 3332
 
  • C. Xu, E. Bründermann, A.-S. Müller, M.J. Nasse, A. Santamaria Garcia, C. Sax, C. Widmann
    KIT, Karlsruhe, Germany
  • A. Eichler
    DESY, Hamburg, Germany
 
  Funding: C. Xu acknowledges the support by the DFG-funded Doctoral School "Karlsruhe School of Elementary and Astroparticle Physics: Science and Technology".
FLUTE (Ferninfrarot Linac- und Test-Experiment) at KIT is a compact linac-based test facility for novel accelerator technology and a source of intense THz radiation. FLUTE is designed to provide a wide range of electron bunch charges from the pC- to nC-range, high electric fields up to 1.2 GV/m, and ultra-short THz pulses down to the fs-timescale. The electrons are generated at the RF photoinjector, where the electron gun is driven by a commercial titanium sapphire laser. In this kind of setup the electron beam properties are determined by the photoinjector, but more importantly by the characteristics of the laser pulses. Spatial light modulators can be used to transversely and longitudinally shape the laser pulse, offering a flexible way to shape the laser beam and subsequently the electron beam, influencing the produced THz pulses. However, nonlinear effects inherent to the laser manipulation (transportation, compression, third harmonic generation) can distort the original pulse. In this paper we propose to use machine learning methods to manipulate the laser and electron bunch, aiming to generate tailor-made THz pulses. The method is demonstrated experimentally in a test setup.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB289  
About • paper received ※ 19 May 2021       paper accepted ※ 06 July 2021       issue date ※ 26 August 2021  
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WEPAB331 Application of KALYPSO as a Diagnostic Tool for Beam and Spectral Analysis 3451
 
  • M.M. Patil, E. Bründermann, M. Caselle, A. Ebersoldt, S. Funkner, B. Kehrer, A.-S. Müller, M.J. Nasse, G. Niehues, J.L. Steinmann, M. Weber, C. Widmann
    KIT, Karlsruhe, Germany
 
  Funding: This work is supported by the BMBF project 05K19VKD STARTRAC and DFG-funded Doctoral School ’Karlsruhe School of Elementary and Astroparticle Physics: Science and Technology’
KALYPSO is a novel detector capable of operating at frame rates up to 12 MHz developed and tested at the institute of data processing and electronics (IPE) and employed at Karlsruhe Research Accelerator (KARA) which is part of the Test Facility and Synchrotron Radiation Source KIT. This detector consists of silicon, InGaAs, PbS, or PbSe line array sensor with spectral sensitivity from 350 nm to 5000 nm. The unprecedented frame rate of this detector is achieved by a custom-designed ASIC readout chip. The FPGA-readout architecture enables continuous data acquisition and real-time data processing. Such a detector has various applications in the fields of beam diagnostics and spectral analysis. KALYPSO is currently employed at various synchrotron facilities for electro-optical spectral decoding (EOSD) to study the longitudinal profile of the electron beam, to study the energy spread of the electron beam, tuning of free-electron lasers (FELs), and also in characterizing laser spectra. This contribution will present an overview of the results from the mentioned applications.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB331  
About • paper received ※ 19 May 2021       paper accepted ※ 22 July 2021       issue date ※ 13 August 2021  
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THPAB042 Bending Radius Limits of Different Coated REBCO Conductor Tapes - An Experimental Investigation with Regard to HTS Undulators 3837
 
  • S.C. Richter, A. Bernhard, A. Drechsler, A.-S. Müller, B. Ringsdorf, S.I. Schlachter
    KIT, Karlsruhe, Germany
  • S.C. Richter, D. Schoerling
    CERN, Geneva, Switzerland
 
  Funding: This work has been sponsored by the Wolfgang Gentner Programme of the German Federal Ministry of Education and Research (grant no. 05E18CHA).
Compact FELs require short-period, high-field undulators in combination with compact accelerator structures to produce coherent light up to X-rays. Likewise, for the production of low emittance positron beams for future lepton colliders, like CLIC or FCC-ee, high-field damping wigglers are required. Applying high-temperature superconductors in form of coated REBCO tape conductors allows reaching higher magnetic fields and larger operating margins as compared to low-temperature superconductors like Nb-Ti or Nb3Sn. However, short undulator periods like 13 mm may require bending radii of the conductor smaller than 5 mm inducing significant bending strain on the superconducting layer and may harm its conducting properties. In this paper, we present our designed bending rig and experimental results for REBCO tape conductors from various manufacturers and with different properties. Investigated bending radii reach from 20 mm down to 1 mm and optionally include half of a helical twist. To represent magnet winding procedures, the samples were bent at room temperature and then cooled down to T = 77 K in the bent state to test for potential degradation of the superconducting properties.
 
poster icon Poster THPAB042 [1.871 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB042  
About • paper received ※ 19 May 2021       paper accepted ※ 18 June 2021       issue date ※ 25 August 2021  
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THPAB048 Design and Fabrication Concepts of a Compact Undulator with Laser-Structured 2G-HTS Tapes 3851
 
  • A. Will, T.A. Arndt, E. Bründermann, N. Glamann, A.W. Grau, B. Krasch, A.-S. Müller, R. Nast, D. Saez de Jauregui
    KIT, Eggenstein-Leopoldshafen, Germany
  • D. Astapovych, H. De Gersem, E. Gjonaj
    TEMF, TU Darmstadt, Darmstadt, Germany
 
  To produce small-scale high-field undulators for table-top free electron lasers (FELs), compact designs have been proposed using high temperature superconducting (HTS) tapes, which show both large critical current densities and high critical magnetic fields with a total tape thickness of about 50 μm and a width of up to 12 mm. Instead of winding coils, a meander structure can be laser-scribed directly into the superconductor layer, guiding the current path on a quasi-sinusoidal trajectory. Stacking pairs of such scribed tapes allows the generation of the desired sinusoidal magnetic fields above the tape plane, along the tape axis. Two practically feasible designs are presented, which are currently under construction at KIT: A coil concept wound from a single structured tape with a length of 15 m, which is a progression of a design that has been presented already in the past, as well as a novel stacked and soldered design, made from 25 cm long structured tapes, soldered in a zig-zag-pattern. In this contribution the designs are briefly recapped and the experimental progress is presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB048  
About • paper received ※ 19 May 2021       paper accepted ※ 12 July 2021       issue date ※ 15 August 2021  
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THPAB126 Operational Experience and Characterization of a Superconducting Transverse Gradient Undulator for Compact Laser Wakefield Accelerator-Driven FEL 4009
 
  • K. Damminsek, A. Bernhard, J. Gethmann, A.W. Grau, A.-S. Müller, Y. Nie, M.S. Ning, S.C. Richter, R. Rossmanith
    KIT, Karlsruhe, Germany
 
  A 40-period superconducting transverse gradient undulator (TGU) has been designed and fabricated at Karlsruhe Institute of Technology (KIT). Combining a TGU with a Laser Wakefield Accelerator (LWFA) is a potential key for realizing an extremely compact Free Electron Laser (FEL) radiation source. The TGU scheme is a viable option to compensate the challenging properties of the LWFA electron beam in terms of beam divergence and energy spread. In this contribution, we report on the operational experience of this TGU inside its own cryostat and show the current status of the TGU and the further plan for experiments. This work is supported by the BMBF project 05K19VKA PlasmaFEL (Federal Ministry of Education and Research).  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB126  
About • paper received ※ 19 May 2021       paper accepted ※ 25 August 2021       issue date ※ 02 September 2021  
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THPAB251 Efficient Terahertz Generation by Tilted-Pulse-Front Pumping in Lithium Niobate for the Split-Ring Resonator Experiment at FLUTE 4299
 
  • M. Nabinger, E. Bründermann, S. Funkner, B. Härer, A.-S. Müller, M.J. Nasse, G. Niehues, R. Ruprecht, J. Schäfer, T. Schmelzer, N.J. Smale
    KIT, Karlsruhe, Germany
  • M.M. Dehler, R. Ischebeck, M. Moser, V. Schlott
    PSI, Villigen PSI, Switzerland
  • T. Feurer, M. Hayati, Z. Ollmann
    Universität Bern, Institute of Applied Physics, Bern, Switzerland
 
  Funding: This work is co-funded via the European Union’s H2020 research and innovation program, GA No 730871, ARIES.
A compact, longitudinal diagnostics for fs-scale electron bunches using a THz electric-field transient in a split-ring resonator (SRR) for streaking will be tested at the Ferninfrarot Linac- Und Test- Experiment (FLUTE). For this new streaking technique, intensive THz pulses are required, which will be generated by laser-based optical rectification. We present a setup for generating THz pulses using tilted-pulse-front pumping in lithium niobate at room temperature. Excited by an 800 nm Ti:Sa pump laser with 35 fs bandwidth-limited pulse length, conversion efficiencies up to 0.027% were achieved. Furthermore, the status of the SRR experiment is shown.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB251  
About • paper received ※ 19 May 2021       paper accepted ※ 14 July 2021       issue date ※ 19 August 2021  
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FRXC03 Modern Ultra-Fast Detectors for Online Beam Diagnostics 4540
 
  • M.M. Patil, E. Bründermann, M. Caselle, A. Ebersoldt, S. Funkner, B. Kehrer, A.-S. Müller, M.J. Nasse, G. Niehues, J.L. Steinmann, W. Wang, M. Weber, C. Widmann
    KIT, Karlsruhe, Germany
 
  Funding: This work is supported by the BMBF project 05K19VKD STARTRAC and DFG-funded Doctoral School ’Karlsruhe School of Elementary and Astroparticle Physics: Science and Technology’
Synchrotron light sources operate with bunch repetition rates in the MHz regime. The longitudinal and transverse beam dynamics of these electron bunches can be investigated and characterized by experiments employing linear array detectors. To improve the performance of modern beam diagnostics and overcome the limitations of commercially available detectors, we have at KIT developed KALYPSO, a detector system operating with an unprecedented frame rate of up to 12 MHz. To facilitate the integration in different experiments, a modular architecture has been utilized. Different semiconductor microstrip sensors based on Si, InGaAs, PbS, and PbSe can be connected to the custom-designed low noise front-end ASIC to optimize the quantum efficiency at different photon energies, ranging from near-UV, visible, and up to near-IR. The front-end electronics are integrated within a heterogeneous DAQ consisting of FPGAs and GPUs, which allows the implementation of real-time data processing. This detector is currently installed at KARA, European XFEL, FLASH, Soleil, DELTA. In this contribution, we present the detector architecture, the performance results, and the ongoing technical developments.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-FRXC03  
About • paper received ※ 19 May 2021       paper accepted ※ 22 July 2021       issue date ※ 01 September 2021  
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