Author: Kaertner, F.X.    [Kärtner, F.X.]
Paper Title Page
MOPOMS001 Progress on Development of AXSIS: A Femtosecond THz-Driven MeV Accelerator and keV X-Ray Source 621
 
  • N.H. Matlis, M. Fakhari, F.X. Kärtner, T. Kroh, M. Pergament, T. Rohwer, M. Vahdani, D. Zhang
    CFEL, Hamburg, Germany
  • R. Bazrafshan, F.X. Kärtner, T. Rohwer
    Deutsches Elektronen Synchrotron (DESY) and Center for Free Electron Science (CFEL), Hamburg, Germany
  • R. Bazrafshan, M. Vahdani
    University of Hamburg, Hamburg, Germany
  • M. Fakhari, D. Zhang
    DESY, Hamburg, Germany
  • F.X. Kärtner, T. Kroh
    The Hamburg Center for Ultrafast Imaging, University of Hamburg, Hamburg, Germany
 
  Funding: This work was supported by KA908-12/1 of the Deutsche Forschungsgemeinschaft and by the ERC under the European Union’s Seventh Framework Program (FP7/2007-2013) through Synergy Grant AXSIS (609920).
We report on the design and progress in implementing a THz-driven relativistic electron accelerator and associated X-ray source, the AXSIS Facility at DESY. We have developed a full layout of the machine based on a THz gun followed by a multi-cycle dielectric loaded metal waveguide THz linear accelerator to generate 20 MeV level, 10 fs electron bunches. The required THz pulse energies are on the mJ-level for the gun and multi-10-mJ-level for the THz linac. Customized laser technologies have been developed allowing for the generation of these pulses up to 1 kHz repetition rate. The generated electron bunches are then focused into a counter propagating optical pulse ’optical undulator’ to generate X-rays in the 6-7 keV range. We will discuss the overall layout of the machine, status of its implementation and technical challenges in the different components as well as diagnostics of this new type of accelerator and X-ray source.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOMS001  
About • Received ※ 08 June 2022 — Revised ※ 11 June 2022 — Accepted ※ 13 June 2022 — Issue date ※ 21 June 2022
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MOPOMS032 Compact-Two-Octave-Spanning Perpendicular Kicker of MeV Electrons Based on a Cubic Magnet Dipole Array 706
 
  • T. Rohwer, R. Bazrafshan, F.X. Kärtner, N.H. Matlis
    Deutsches Elektronen Synchrotron (DESY) and Center for Free Electron Science (CFEL), Hamburg, Germany
  • R. Bazrafshan
    University of Hamburg, Hamburg, Germany
  • F.X. Kärtner
    The Hamburg Center for Ultrafast Imaging, University of Hamburg, Hamburg, Germany
  • F.X. Kärtner
    CFEL, Hamburg, Germany
  • P. Vagin
    DESY, Hamburg, Germany
 
  Funding: This work has been supported by the European Research Council under the European Union’s Seventh Framework Programme (FP7/2007-2013) through the Synergy Grant AXSIS (609920).
New compact particle acceleration structures, including but not limited to plasma, THz and direct laser driven accelerators, have in common that they cover a wide energy range of potential final energies and often show a large energy spread. Moreover, they may initially have a rather large emittance. To analyze the energy range of a single shot and/or to deflect the beam to safely dump the electrons away from an end-station requires an electron kicker covering a large energy range. Here, we present a magnetic dipole structure based on a 2D Halbach array. For the current experimental test accelerator in AXSIS, an electron beam in the energy range from 4 to 20 MeV is deflected by 90 degree and energetically dispersed. In direct contrast to a simple magnetic dipole, an array of cubic magnet blocks with tailored magnetization directions allows a focusing of the beam for both longitudinal and transverse directions at 90 degree bend. A generic algorithm optimizes the magnetic field array to the predefined deflection angle and divergence. The modular array structure, in combination with the algorithm enables a simple exchange of magnets to adapt for different beam parameters.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOMS032  
About • Received ※ 08 June 2022 — Revised ※ 11 June 2022 — Accepted ※ 12 June 2022 — Issue date ※ 14 June 2022
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MOPOMS003 Single-Sided Pumped Compact Terahertz Driven Booster Accelerator 625
SUSPMF026   use link to see paper's listing under its alternate paper code  
 
  • T. Kroh, R. Bazrafshan, F.X. Kärtner, N.H. Matlis
    Deutsches Elektronen Synchrotron (DESY) and Center for Free Electron Science (CFEL), Hamburg, Germany
  • M. Fakhari, M. Pergament, T. Rohwer, M. Vahdani, D. Zhang
    CFEL, Hamburg, Germany
  • F.X. Kärtner
    The Hamburg Center for Ultrafast Imaging, University of Hamburg, Hamburg, Germany
  • K. Kawase
    JAEA, Kizugawa, Japan
 
  Funding: European Research Council under the European Union’s Seventh Framework Programme (FP7/2007-2013) through the Synergy Grant ’Frontiers in Attosecond X-ray Science: Imaging and Spectroscopy’ (609920).
Scaling the RF-accelerator concept to terahertz (THz) frequencies brings several compelling advantages, including compactness, intrinsic timing between the photoemission and driving field sources, and high field gradients associated with the short THz wavelength and high breakdown threshold. Recent demonstrations of such THz powered accelerators relied on two counter-propagating single-cycle THz pulses. However, to achieve high energy gains in the acceleration process high energy THz pulses are needed which in turn require complex optical setups. Here, we present on the development of a matchbox sized multi-layered accelerator designed to boost the 50 keV output of a DC electron gun to energies of ~400 keV that only requires a single THz pulse to be powered. An integrated tunable mirror inside the structure interferes the front of the driving THz pulse with its rear part such that the field in the interaction region is optimized for efficient acceleration. This reduces the complexity of the required optical setup. Such a compact booster accelerator is very promising as electron source in ultrafast electron diffraction experiments and as booster stage prior to THz based LINACs.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOMS003  
About • Received ※ 08 June 2022 — Accepted ※ 17 June 2022 — Issue date ※ 20 June 2022  
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MOPOMS005 Start-to-End Simulations of a THz-Driven ICS Source 631
 
  • M. Fakhari, Y.-K. Kan
    DESY, Hamburg, Germany
  • F.X. Kärtner
    The Hamburg Center for Ultrafast Imaging, University of Hamburg, Hamburg, Germany
  • F.X. Kärtner
    Deutsches Elektronen Synchrotron (DESY) and Center for Free Electron Science (CFEL), Hamburg, Germany
  • N.H. Matlis, M. Vahdani
    CFEL, Hamburg, Germany
  • M. Vahdani
    University of Hamburg, Hamburg, Germany
 
  We present start-to-end simulations for a fully THz-driven table-top X-ray source. A dielectric-loaded metallic cavity operating at its Higher Order Mode accelerates 1 PC photo emitted electron bunch up to 430 keV kinetic energy. The output beam of the gun is injected into a dielectric-loaded waveguide where phase velocity of the traveling wave is adjusted in such a way that electrons see an accelerating field all the way along the tube resulting to an 18.5-MeV output beam which is then transported to an inverse Compton scattering (ICS) stage. The injection phase of the electrons can be tuned to introduce a negative energy chirp to the electron bunch leading to a ballistic bunch compression after the linac. In addition, a set of permanent magnet quadrupoles is designed to focus the beam at the ICS interaction point where the electron beam scatters off a 250-mJ, 0.5ps, 1-µm laser beam and generates an X-ray beam with 2.6x107 photons per shot containing photon energies 2keV< Eph <8keV in a beam with 50 mrad half opening angle. The required terahertz waves to power the gun and linac are 550-ps pulses at 300 GHz containing 5 mJ and 23 mJ energies respectively with 1 kHz repetition rate.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOMS005  
About • Received ※ 08 June 2022 — Accepted ※ 17 June 2022 — Issue date ※ 25 June 2022  
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MOPOMS007 Optimized Dielectric Loaded Waveguide Terahertz LINACs 634
SUSPMF028   use link to see paper's listing under its alternate paper code  
 
  • M. Vahdani
    University of Hamburg, Hamburg, Germany
  • M. Fakhari
    DESY, Hamburg, Germany
  • F.X. Kärtner
    The Hamburg Center for Ultrafast Imaging, University of Hamburg, Hamburg, Germany
  • F.X. Kärtner
    Deutsches Elektronen Synchrotron (DESY) and Center for Free Electron Science (CFEL), Hamburg, Germany
  • M. Vahdani
    CFEL, Hamburg, Germany
 
  Dielectric loaded waveguides (DLW) powered by multicycle terahertz (THz) pulses have shown promising performance as compact linear accelerators due to higher breakdown fields at THz frequencies compared to conventional RF components. By changing the dielectric dimensions one can control phase and group velocities of the THz pulse inside the DLW. Since optimum waveguide dimensions are dependent on initial electron energy, THz pulse energy, and etc., it is worthwhile to determine optimum values for different conditions to maximize final kinetic energy. In this work, we present a combined analytical/numerical guide to determine the optimum DLW parameters for single on-axis electron acceleration. We also introduce normalized graphic representations to visualize optimum designs for different initial electron and THz pulse energies.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOMS007  
About • Received ※ 09 June 2022 — Revised ※ 09 June 2022 — Accepted ※ 17 June 2022 — Issue date ※ 21 June 2022
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