WEOCMH  —  Beam Instrumentation and Feedback   (26-May-10   15:00—16:00)

Chair: I.S. Ko, PAL, Pohang, Kyungbuk

Paper Title Page
WEOCMH01 First Beam Test of the Tilt Monitor in the ATF2 Beam Line 2402
 
  • D. Okamoto
    Tohoku University, Graduate School of Science, Sendai
  • Y. Honda, T. Tauchi
    KEK, Ibaraki
  • T. Sanuki
    Tohoku University, School of Scinece, Sendai
 
 

We have studied a beam orbit tilt monitor for stabilizing the beam orbit in ATF2. Once we can measure a beam orbit tilt with high precision at one point, we can relate this data with the beam position profile at the focal point. A tilt monitor is composed of a single rectangular sensor cavity and a waveguide to extract the signal. In the sensor cavity, there is the most basic resonant mode called monopole mode. This monopole mode is perpendicular to the nominal beam axis, and excited by the beam tilt. We extract this monopole mode. As the result, the amplitude of the extracted signal is proportional to the tilt angle. The tilt monitor is almost indepnedent with beam postion, so we can get the tilt date independently. According to our simulation, the sensitivity is estimated about 35nrad in the vertical direction. The prototype was completed and installed in the test area on the ATF2 beamline. The first beam test will be performed in December 2009. We will report this result and future update plan.

 

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WEOCMH02 Recent Developments of the Beam Arrival Time Monitor with Femtosecond Resolution at FLASH 2405
 
  • M.K. Bock, M. Felber, P. Gessler, K.E. Hacker, F. Ludwig, H. Schlarb, B. Schmidt, J. Zemella
    DESY, Hamburg
  • F. Löhl
    CLASSE, Ithaca, New York
  • S. Schulz, L.-G. Wißmann
    Uni HH, Hamburg
 
 

At FLASH an optical synchronisation system with femtosecond stability is now being installed and commissioned. The system is based on pulses from a passively modelocked fibre laser which are distributed in length-stabilised fibres to various end-stations. Several modifications and improvements with respect to the original layout, especially concerning permanent operation and reliability, are already incorporated at this stage. The electron bunch arrival-time monitors (BAM), based on electro-optical modulation, are an integral part of the system. Built on the experiences with first prototypes, the most recent version of the BAM, installed prior to the first bunch compressor, includes essential changes affecting the optical layout, the mechanical and thermal stability as well as the electronics for read-out and controls. The revised BAM showed improved performance and will be complemented by a second congenerous BAM after the first bunch compressor during the present FLASH upgrade. The experiences with installation as well as the scope of improvements as to simplification and long-term stability will be presented.

 

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WEOCMH03 Bunch Length Measurements with Laser/SR Cross-Correlation 2408
 
  • A. Miller, D.R. Daranciang, A. Lindenberg
    Stanford University, Stanford, California
  • W.J. Corbett, A.S. Fisher, J.J. Goodfellow, X. Huang, W.Y. Mok, J.A. Safranek, H. Wen
    SLAC, Menlo Park, California
 
 

By operating SPEAR3 in the quasi-isochronous (low-alpha) mode, one can produce synchrotron radiation with pulse durations of order 1ps. Applications include pump-probe x-ray science and the production of THz radiation. Measurements of short pulse lengths are difficult, however, because the light intensity is low and streak camera resolution is of order 2ps. Bunch arrival time and timing jitter are also important factors. In order to further quantify the pulse length and timing system performance, a 5MHz, 50fs mode-locked laser was used to cross-correlate with the visible SR beam in a BBO crystal. The 800nm laser pulse was delayed with a precision mechanical stage and the product SHG radiation detected with a photodiode / lock-in amplifier using the ring frequency as reference. In this paper we report on the experimental setup, preliminary pulse length measurements and prospects for further improvement.

 

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