Author: Vu, L.V.
Paper Title Page
WEPF04 A New Compact Design of a Three-Dimensional Ionization Profile Monitor (IPM) 811
  • H.F. Breede, H.-J. Grabosch, M. Sachwitz, L.V. Vu
    DESY Zeuthen, Zeuthen, Germany
  FLASH at DESY in Hamburg is a linear accelerator, which uses superconducting technology to produce soft x-ray laser light ranging from 4.1 to 45 nm. To ensure the operation stability of FLASH, monitoring of the beam is mandatory. Two Ionization Profile Monitors (IPM) detect the lateral x and y position changes. The functional principle of the IPM is based on the detection of particles, generated by interaction of the beam with the residual gas in the beam line. The newly designed IPM enables the combined determination of the horizontal and vertical position as well as the profile. This is made possible by a compact monitor, consisting of a cage in a vacuum chamber, two micro-channel plates (MCP) and two repeller plates with toggled electric fields at the opposite sides of the MCPs. The particles created by the FEL beam, drift in a homogenous electrical field towards the respective MCP, which produces an image of the beam profile on an attached phosphor screen. A camera for each MCP is used for evaluation. This indirect detection scheme operates over a wide dynamic range and allows the detection of the center of gravity and the shape of the beam. The final design is presented.  
poster icon Poster WEPF04 [3.643 MB]  
WEPF06 A Fast Switching Mirror Unit at FLASH 818
  • F. Perlick, J.D. Good, N. Leuschner, A.S. Ontoso, M. Sachwitz, L.V. Vu
    DESY Zeuthen, Zeuthen, Germany
  • H. Schulte-Schrepping
    DESY, Hamburg, Germany
  The Free Electron Laser (FLASH) at DESY Hamburg is a linac providing unique experimental opportunities to investigate the atomic structure and the properties of materials, nanoparticles, viruses and cells. At the experimental hall, the incoming FEL beam can be deflected towards five test sites by silicon mirrors mounted into vacuum vessels, of which one is operated in permanent switching mode, allowing the simultaneous use of the light at two different test sites. So far, the entire vacuum vessel with the mirror inside is moved into the beam by a linear motor. This results in high translatory inertia and, to compensate the vessel motion, requires vacuum bellows, which have a limited lifetime especially at higher switching frequencies. Therefore, in the recent design the mirror is shifted by piezo motors operated inside the vessel under ultra-high vacuum conditions. However, temperature measurements revealed that during continuous operation the motor reaches up to 90°C only when exposed to air, necessitating long breaks to allow it to cool. Therefore suitable cooling methods are being investigated to guarantee continuous operation of the motor under ultra-high vacuum conditions.  
poster icon Poster WEPF06 [2.431 MB]