Reza's thoughts on bunchlength measurement at UITF

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Checking the bunch length system with 200keV beam and No choppers

Requirements: At minimum we need the following

  1. - Beam through bunch length cavity
  2. - More than 5uA tune beam
  3. - 200 keV energy or higher
  4. - Bunch length less than 30 degree of 1497 (typical low current beam at the gun)


  1. ) With choppers and buncher off, thread the 200 keV beam from gun up through the bunch length cavity.
  2. ) Setup more than 5uA tune beam (preferably to a beam dump or Fcup).
  3. ) Check the bunch length system by answering the following questions
  4. ) Do you see the bunch length output signal? If not stop and investigate.
  5. ) Does the bunch length signal change as the gun laser phase changes (multiples of 5 degrees, up to +/- 50 deg)? If not stop and investigate. Does the amount of change make sense?
  6. ) Does the bunch length signal changes as the 6 GHz reference signal phase is change (+/- 180 deg)? If not investigate.
  7. ) When all questions above have positive answer, the test is complete and system is checked for hardware.