Author: Ischebeck, R.
Paper Title Page
High Energy Tunable THz Source Based on Wakefield Excitation  
  • S. Bettoni, P. Craievich, E. Ferrari, R. Ischebeck, F. Marcellini, C. Ozkan Loch, M. Pedrozzi, S. Reiche, V. Schlott
    PSI, Villigen PSI, Switzerland
  We plan to use the interaction of a beam optimized for the generation of FEL radiation with a dielectric waveguide as a pump source for pump and probe experiments in FEL facilities. This scheme provides several advantages to fulfill the user requirements for a radiation source, in particular synchronization with the hard x-ray pulses, tunability throughout the THz frequency range of interest and energy level. We present the optimization of this scheme for SwissFEL, where optimized beam optics matches into a small aperture dielectric waveguide allowing for the highest THz radiation energy. We also propose a method to further increase the THz radiation energy at higher frequencies by shaping the electron bunch.
Paper soon submittedto a journal
TUP053 The ACHIP Experimental Chambers at PSI 1
  • E. Ferrari, M. Bednarzik, S. Bettoni, S. Borrelli, H.-H. Braun, M. Calvi, Ch. David, M.M. Dehler, F. Frei, T. Garvey, V. Guzenko, N. Hiller, R. Ischebeck, C. Ozkan Loch, E. Prat, J. Raabe, S. Reiche, L. Rivkin, A. Romann, B. Sarafinov, V. Schlott, S. Susmita
    PSI, Villigen PSI, Switzerland
  • E. Ferrari, L. Rivkin
    EPFL, Lausanne, Switzerland
  • P. Hommelhoff
    University of Erlangen-Nuremberg, Erlangen, Germany
  • J.C. McNeur
    Friedrich-Alexander Universität Erlangen-Nuernberg, University Erlangen-Nuernberg LFTE, Erlangen, Germany
  Funding: Gordon and Betty Moore Foundation
The Accelerator on a Chip International Program (ACHIP) is an international collaboration, funded by the Gordon and Betty Moore Foundation, whose goal is to demonstrate that a laser-driven accelerator on a chip can be integrated to fully build an accelerator based on dielectric structures. PSI will provide access to the high brightness electron beam of SwissFEL to test structures, approaches and methods towards achieving the final goal of the project. In this contribution, we will describe the two interaction chambers installed on SwissFEL to perform the proof-of-principle experiments. In particular, we will present the positioning system for the samples, the magnets needed to focus the beam to sub-micrometer dimensions and the diagnostics to measure beam properties at the interaction point.
Characterization of High-Brightness Electron Beams at the Frontiers of Temporal and Spatial Resolution  
  • R. Tarkeshian, T. Feurer, M. Hayati, Z. Ollmann
    Universität Bern, Institute of Applied Physics, Bern, Switzerland
  • T. Garvey, R. Ischebeck, E. Prat, S. Reiche, V. Schlott
    PSI, Villigen PSI, Switzerland
  • P. Krejcik
    SLAC, Menlo Park, California, USA
  • W. Leemans, R. Lehé, S. Steinke
    LBNL, Berkeley, California, USA
  We present two novel diagnostics to characterize high-brightness electron beams. The first technique, based on the tunnel ionization of a neutral gas by the intense (GV/m) self-field of the electron beam, can be used to measure the volumetric charge density of the beam, for example to reconstruct pulse durations shorter than few femtoseconds or to measure transverse beam sizes below the micron level. Experiments with sub-femtosecond unipolar self-field of electron beam, that approach the through-the-barrier tunneling times, could further deepen our understanding of quantum tunneling process. The second method can be used to streak electron beams with single cycle THz radiation concentrated in a micrometer gap of a resonant antenna, creating an enhanced electric near-field distribution. With this diagnostic one can measure with sub-femtosecond resolution the longitudinal duration, the slice emittance and energy spread of beams with energies up to tens of MeV. We show the validity of both methods with analytical calculations and particle-in-cell code simulations. We finally present practical implementation of both diagnostics at LCLS, in the XLEAP* experiment, and BELLA.
* X-Ray Laser Enhanced Altosecond Pulse Generation (XLEAP) For LCLS.
Sub-Micrometer Resolution, Nanotechnology Based Wire Scanners for Beam Profile Measurements at SwissFEL  
  • S. Borrelli, M. Bednarzik, Ch. David, E. Ferrari, A. Gobbo, V. Guzenko, N. Hiller, R. Ischebeck, G.L. Orlandi, C. Ozkan Loch, B. Rippstein, V. Schlott
    PSI, Villigen PSI, Switzerland
  SwissFEL Wire scanners (WSCs) measure electron beam transverse profile and emittance with high-resolution in a minimally-invasive way. They consist of a wire fork equipped with two 5 micrometer W wires, for high-resolution measurements, and two 12.5 micrometer Al(99):Si(1) wires, to measure the beam profile during FEL operation. Although the SwissFEL WSCs resolution is sufficient for many purposes, for some machine operations and experimental applications it is necessary to improve it under micrometer scale. The WSC spatial resolution is limited by the wire width which is constrained to few micrometers by the conventional manufacturing technique of stretching a metallic wire onto a wire-fork. In this work, we propose to overcome this limitation using the nanofabrication of sub-micrometer metallic stripes on a membrane by means of e-beam lithography. This presentation focuses in the design, construction and characterization of a high-resolution WSC prototype consisting of a silicon nitride membrane onto which two gold or nickel wires, widths ranging from 2 micrometers to 0.4 micrometers, are electroplated. We will also present the preliminary electron beam tests of our prototype.  
Saturation of Scintillators in Profile Monitors  
  • R. Ischebeck, E. Ferrari, F. Frei, N. Hiller, G.L. Orlandi, C. Ozkan Loch, V. Schlott
    PSI, Villigen PSI, Switzerland
  SwissFEL uses scintillating screens to measure the transverse profile of the electron beam. These screens, in combination with quadrupole magnets and a transverse deflecting RF structure, are used to measure projected and slice emittance, as well as bunch length. Scintillating screens have been chosen over optical transition radiators because of the coherent transition radiation emitted by the compressed bunches. It is therefore instrumental to characterize the linearity of these monitors in order to ensure reliable measurements. We are presenting here a measurement of saturation effects due to the high charge density in SwissFEL, and describe the results with a numerical model of the process.