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auto-correlation

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THPP056 Initial Measurements of CSR from a Bunch-Compressed Beam at APS csr, gun, linac, radiation 608
 
  • A.H. Lumpkin, W. Berg, M. Borland, N. Sereno
    ANL, Argonne, Illinois
  
 

Funding: Work supported by U.S. Department of Energy, Office of Basic Energy Sciences, under Contract No. W-31-109-ENG-38.

The interest in bunch compression to generate higher peak current electron beams with low emittance continues in the free-electron laser (FEL) community. At the Advanced Photon source (APS) we have both an rf thermionic gun and an rf photocathode (PC) gun on the S-band linac. At the 150-MeV point in the linac, we have a flexible chicane bunch compressor whose four dipoles bend the beam in the horizontal plane. There is also a vertical bend dipole after the chicane that allows measurement of energy and horizontal beam size at the imaging screen station to study possible effects on emittance due to coherent synchrotron radiation (CSR) in the chicane. A far-infrared (FIR) coherent radiation monitor is located downstream of the chicane as well. We have begun recommissioning of this device with coherent transition radiation (CTR), but we also have directly observed CSR from the bunch-compressed beam as it transits the vertical dipole and goes into the down leg. The unique geometry allows simultaneous tracking of bunch length, horizontal emittance, and energy distribution effects. Initial measurements of the CSR and CTR as a function of linac phase are described.

   
    
THPP072 Single-Shot Electron Bunch Length Measurements Using a Spatial Auto-Correlation Interferometer interferometer, laser, linac, single-shot 648
 
  • D. Suetterlin, V. Schlott, H. Sigg
    PSI, Villigen
  • D. Erni, H. Jäckel
    ETH, Zurich
  • A. Murk
    University of Berne, Institute of Applied Physics, Berne
  
 

The polarization dependent intensity distribution of coherent transition radiation (CTR) emission has been studied theoretically and experimentally at an optical beam port downstream the 100 MeV SLS pre-injector LINAC. Based on these analyses, a spatial interferometer using the vertically polarized lobes of CTR has been designed and installed at this location. While a proof of principle of this bunch length monitor was achieved by step-scan measurements with a Golay cell detector, the single shot capability has been demonstrated by electro-optical correlation of the spatial CTR interference pattern with the fairly long Nd:YAG laser pulses in a ZnTe crystal. In single-shot operation variations of the bunch length due to different settings of the LINACs bunching cavities have been observed.