T-474 phone conference

Thursday 22 june 2006, 16:00 GMT+1 (08:00 PDT, 11:00 EDT)

Phone number : (+ 1) 510-665-5437
Meeting code : 4194

general points

  • Email list set up, info see mail
  • Plots and analysis progress can be found as usual in the T474 analysis eLog
  • Reprocessing of external clock basically done, files can be found at this location, the runlist with more details is still in the eLog, Finished runs so far :
    367 - 501, 526 - 536, 679 - 705 ( all except 960 - )
    with all BPMs calibrated. Note for runs 960- no BPM 31,32 calibration will exist

discussion points


  Minutes of the 22 June 2006 T474 Phone conference

 - The funky IQ plots on the q10 reference cavity are due to the fact
   that the cables were swapped inbetween the q and x cavity for the
   last couple of runs. 

 - Apart from a couple of lonely runs, the external clock runs are
   basically reprocessed. They reside currently at UCL but will be
   copied to the same datadisk at SLAC. Will communicate by email on

 - Main discussion point is the phase dependence of the resolution,
   for which Mark seems to have found a clear hint from his MC
   simulation, where he varies the phase of the generated waveform
   keeping the amplitude constant. This seems to generate a
   small but large enough phase dependence of the DDC amplitude. Yury
   thinks this might be due to some non perfect filtering of the
   double-frequency component of the downconversion. So a couple
   of questions arose :

    o Does the amplitude of the residual sin-wave scale with the
      filter bandwidth ? -> clear hint ! 
    o Can we get rid of this effect by some IQ rotation ?
    o Can this behaviour be fixed by tuning the frequency or the t0Ref ?
    o Would reducing the filter bandwidth help ? Or cut-off parameter ?
    o Behaviour same for real and imaginary part ?

   Further checks in MC :

    o check effect of going off-frequency
    o can we predict the phase of this residual harmonic, either by MC
      simulation of by rigorously going through the math, and
      possibly correct for it in the algorithm ?

   Eventually, w.c.s. we could try out different filters as well, if
   this proves to be the problem. 

 - Now that the reprocessing of the external clock runs is basically
   done, it's time to revisit the systematics! Mark will have a think
   again and put something in the eLog for everybody to add/comment.

    o Need resolutions tabulated versus various beam conditions,
    o Should *really* revisit the extrapolation in DDC possibly
      enabling us to move t0 back in the waveform, enhancing
    o Look at stability of frequencies, gamma's etc...
    o Relationships between BPM stations, orbit fitting

 - The berkeley gang will come up with some macros for all of
   this. Yury will take the libRooEsa library from the UCL CVS and put 
   it into the main CVS at SLAC together with the rest of the data
   production code.

 - We will try to have a phone conference next week, will
   communicate to esa-t474 list.

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