Beams-doc-2446-V1
September 8,2006
Rob Kutschke

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Abstract:

This note examines pbar data for state 11.  Two problems
are seen:  1) vp601 and hp602 have bad turn by turn sum 
and position data but their digitized raw data look OK; 
2) in the extraction turn by turn, the first two turns 
show a low sum signal.  I am not sure if this is a bug 
or a feature.

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The following notes refer to the accompanying pdf file.

These data are antiproton state 11, RR to TeV, turn by 
turn data.  Both injection and  extraction will be shown.
The data were taken Sept 7, 2006 in the mid afternoon.

Page 1:
  This is a reminder of what good data looks like.

  Top left: Sum signal, beam arrives on turn 34 ( counting 
            from 0 ).
  Top right: Position, set to 0 if sum is below a 
             threshold of 2000.
  Bottom left:  fft of sum, using only points above
                threshold and with the mean removed
                before fft.
  Bottom right: fft of position, using only points above 
                threshold and with the mean removed 
                before fft.

Page 2:

The top histogram shows the turn at which the beam first 
appears, as a function of bpm number, in order: hp100, 
hp101, vp101, hp102 ....
( ie numerical order, with h before v when both exist ).
The house boundaries are overlayed in red.

The second histogram is the same data zoommed in on
the y axis.

There are two bad bpms for which the beam is present 
at turn 0: vp101 and hp102.  More on these later.

For all other bpms the beam arrives at turn 34 or 35.
The seams are at:

  BPM   First turn
 vp321   34
 hp322   35
 hp532   35
 vp601    bad data
 hp602    bad data
 vp603   34

Dave: are these seams correct?

The third plot is the number of turns with a sum signal
over threshold ( 2000 counts).  The fourth plot is the 
same histogram but with a zoomed in y scale.  From this 
we learn that, except for vp601 and hp602, all bpms stay
above threshold for all turns after the first turn above
threshold.

Page 3:

Now look at the two bad channels in detail.

Top left:     sum signal for vp601 vs turn number.
Top right:    Detail for first 50 turns.
Bottom left:  sum signal for hp602 vs turn number.
Bottom right: Detail for first 50 turns.

From this we see that there is a total failure for
these BPMs.

Page 4:

This is the raw data for the two bad channels, taken
on a shot two days earlier.  This is still state 11.
The timing was set to show a full empty turn before
the first turn with data.

Top two plots:  Raw A and B for vp601
Next two plots: Raw A and B for hp602

Bottom plot: Raw A for hp603, a known good BPM
             included as a reference.  This BPM 
             shows good turn by turn data.

I believe that this shows that the problem lies
in the Echotek board or after, not in the 
transition boards or before.

According to Steve's email of June 27, these BPMs
are channels 15 and 16 in house 60S:

I:VP601 --> Channel 15
I:HP602 --> Channel 16

I think this means that they are on different 
Echotek boards.  So if it this is not a single board
failure - which makes me suspect a downstream bookkeeping
issue.

Steve: Is there anything unusual in the software
       configuration of 60S?  Have I correctly understood
       the channel assignments?


Page 5:

The sum signal vs turn number for the extraction tbt
measurement for the two bad bpms.  Nothing but noise.

Page 6:

Top left: Sum signal vs turn number for the extraction
           buffer for hp100.
Top right: Detail of same plot showing first 75 turns.

Bottom left and right: same plots for hp101.

These data illustrate a feature that is present in
all bpms in all state11 shots that I have looked at: 
the first two turns show a really low sum signal 
compared to the remaining turns.

Dave: Are there beam gymnastics going on at this
      time that could explain this or is this a
      sign of a bookkeeping problem?