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    User name paschke

    Log entry time 19:12:36 on July14,2005

    Entry number 148036

    keyword=How to measure the "phase advance"

    
    How to characterize the phase advance:
    
    First, just so you understand: what "phase advance" means for us is that 
    the two target bpms (4a and 4b) see different things when we pulse our
    beam dithering magnets.  Here I describe how to take the measurement.  
    I don't want to describe interpretation here... it would take a while.
    
    Steps for the measurement:
    
    1) About 10 uA of CW beam (or greater) is required for this measurement. For 
    tonight, that means we should do this with no target.
    
    2) Call MCC and ask them for two things:
      - Enable position modulation.  On accelerator medm screen, under "Magnets",
    under "Magnet Commander", under "1C", under "Position Modulation Control",
    set the switch to "MODULATION ON"
      - turn OFF position feedback in Hall A.  If hall C is not running and 
    the Hall A energy FFB is in use, the Hall A energy FFB must also be turned OFF.
    
    3) Start a run with the HAPPEX DAQ
    
    4) on the Greenmonster GUI (running on the adaql1 terminal), under the 
    "BMW" tab,  in the _upper_ box, hit the button "start beam modulation", 
    wait a couple of seconds then hit the button "check status"  You should 
    see statements like "beam modulation is ON" and 
    "Beam Modulation script is ACTIVE".
    
    5) wait for 2 full minutes, then hit the button "stop beam modulation" 
    (this is the same button as before, it just changed names).  Wait a couple
    of seconds, then hit the button "check status".  you should see statements
    like "beam modulation is OFF" and "Beam Modulation script is INACTIVE".
    
    6) Repeat steps 4-5, to generate a second cycle.  Be sure, when you are done,
    that you hit "check status" and see that "beam modulation is OFF".
    
    7) Be paranoid, and check the status of beam modulation again.  Really, 
    this should be off. Now end the HAPPEX run.  
    
    8)  Analyze the HAPPEX run (prompt can do this).
    
    9) type the following commands as apar on an adaq machine:
    
     > gopan
     > pan
     [0] open(####)   (where #### is the HAPPEX DAQ run number of interest)
     [1] .x lmacro/ditview3.macro
    
    If the bpms are not showing a clear response from the changing magnets, 
    then something is wrong. (You should see clear "triangle-wave" type patterns
    in each color on some bpm, except for energy which is not pulsing.) If you
    see this, halog the plot from this macro. If you don't see this, call MCC
    and ask if they are really sure that there is no FastFeedback operating on 
    the Hall A beam. (Right now, we don't care if Hall C has FFB going or not...
    later we will care, but not now.) When they are sure, try steps 4-9 again.
    If the plot still looks wrong, you've probably failed. Give up,  
    but halog the results and try to get on with your life anyway.
    
    10) Call MCC and tell them you're done, and an expert will interpret the
    plot later.  Tell them to disable position modulation again 
    (turn "MODULATION OFF" as per above instructions) and to go back to 
    whatever state they prefer for the FastFeedback. 
    
    Yer done with this procedure.