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 \title{\makebox[\textwidth][r]{\normalsize CB-Note 313}\\[2cm]
Report on the last CB-Runs 8.10 - 9.12 1996}

 \author{A.~Berdoz, C.~A.~Meyer, W.~Roethel and P.~Schmidt }

\newpage

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 \tableofcontents 
 \listoftables
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\section{General Remarks}
This run report covers the run period between 8 October and 9 December 
1996, which also happens to be the last run period in CB history. Due to
the long measurement time (almost 3 months) the run co-ordination was split
in three periods (see table ~\ref{run96} for an overview).
\begin{table}[htbp]
\begin{tabular}{|c|c|c|c|}
\hline
Run Time & Co-ordination & Trigger & $\bar{p}$-Momenta ($\frac{MeV}{c}$)
 \\ \hline
17.10 - 27.10 1996 & W.Roethel et al. (Munich) & 0 \& 2 prong & 900, 1800
\\ \hline
28.10 - 17.11 1996 & P.Schmidt (Hamburg) & 0-prong & 900, 1642, fine scan \\
\hline
18.11 - 9.12 1996 & A.Berdoz, C.Meyer (CMU) & 0 \& 2 prong & 1525, 1642 \\
\hline
\end{tabular}
\caption[Run Co-ordination Oct-Dec 1996]{ {\footnotesize {\em 
Run co-ordination, trigger and antiproton momenta in last CB-run.
}}
}
\label{run96}
\end{table}
 Note, that the triggers
mentioned in table ~\ref{run96} refer to the triggers mainly used for data
taking. As is usual procedure, also a certain amount of minimum bias and
other triggers were applied (details given below).

The overall performance of the detector during these weeks was very stable
and reliable. Main problems occured due to general power failures and/or
 machine problems at LEAR.

\section{Trigger Conditions}

The main trigger conditions are shown in table ~\ref{trigger}.
For check-ups an additional trigger allowing for 2-or-more prongs was
set-up. 

\begin{table}[htbp]
\begin{center}
\begin{tabular}{|c|c|c|}
\hline 
Trigger name & SVX multiplicity & JDC multiplicity \\
\hline 
\hline 
2-Pr.default & 0-3 & 2 in layer 9/10\\
\hline 
0pr24.900 & 2 & 4 in layer 9/10 \\
 or & 0  & 0 in Layer 2/3 \\
  & & and 0 in Layer 9/10\\
\hline 
0-Pr\_nm.xxx & no SVX & 0 in layer 2/3 \\
   & instead Tonys box & 0 in layer 9/10 \\ 
\hline 
\end{tabular}
\end{center}
\caption[Main Trigger Conditions]{ {\footnotesize {\em 
Main Trigger Conditions used in 96 Oct-Dec run. In the 0-prong Trigger,
the xxx refers to the beam momentum used.
}}
}
\label{trigger}
\end{table}

Please note, that in case of all 0-prong triggers the Quick Energy Sum
(Tony's Box) was applied. As is common practice, the energy threshold
was adjusted at the beginning of each new $\bar{p}$ - momentum by using
online data.

\section{Accumulated Data}
The following lists ( ~\ref{data1}, ~\ref{finescan2}, ~\ref{data3} and
~\ref{zerop}) show
all data taken during the three different run-coordination periods.


\subsection{8 October - 27 October}

Includes 900 and 1800$\frac{MeV}{c}$ data taking. Very briefly a Kshort
trigger was tested, but this trigger was abandoned in the end.
The accumulated data per momentum and trigger can be seen in table
~\ref{data1}.

\begin{table}[htbp]
\begin{center}
\begin{tabular}{|l|r|r|}  
\hline
  Triggername       & Events @ 900 & Events at 1800 \\
  \hline
  0-pr-nm.900       & 1.95 M & 6.72  M \\ \hline
  0-pr-24.900       & 2.22 M &  \\ \hline
  2ormore           & 0.134M & 3.4M (and 200K for testing) \\ \hline
  minimum bias      & 21K &  \\ \hline 
  2 prong.default   & 21.01M & 7K \\
 \hline
\end{tabular}
\end{center}
\caption[Statistics of 900 and 1800 MeV]
{ {\footnotesize {\em
Summary of statistics for the 900 and 1800 $\frac{Mev}{c}$ running}}}
\label{data1}
\end{table}


\subsection{28 October - 17 November 1996}
This periods includes data taking for the {\em fine scan} and mostly
0-prong measurements at 900 and 1642 $\frac{MeV}{c}$.

\subsubsection{Fine Scan}
List ~\ref{finescan1} shows the used trigger files and their
corresponding antiproton momenta (at extraction) as measured by LEAR.
\begin{table}[htbp]
\begin{center}
\begin{tabular}{|r|r|}
\hline
Trigger Name & Antiproton Momenta \\ \hline
$1415\frac{MeV}{c}$ & 1412,9$\frac{MeV}{c}$ \\ \hline
$1420\frac{MeV}{c}$ & 1416,4$\frac{MeV}{c}$ \\ \hline
$1426\frac{MeV}{c}$ & 1422$\frac{MeV}{c}$  \\ \hline
$1432\frac{MeV}{c}$ & 1428,7$\frac{MeV}{c}$ \\ \hline
$1437\frac{MeV}{c}$ & 1436,4$\frac{MeV}{c}$ \\ \hline
$1443\frac{MeV}{c}$ & 1443,06$\frac{MeV}{c}$ \\ \hline
$1449\frac{MeV}{c}$ & 1448,74$\frac{MeV}{c}$ \\ \hline
$1454\frac{MeV}{c}$ & 1454,42$\frac{MeV}{c}$ \\ \hline
$1460\frac{MeV}{c}$ & 1460,5$\frac{MeV}{c}$ \\ \hline
\end{tabular}
\end{center}
\caption[Fine Scan Antiproton momenta]
{{\footnotesize {\em Exact values of antiproton momenta and their
corresponding trigger names.}}}
\label{finescan1}
\end{table}
 
The number of accumulated data during the fine scan are listed in
~\ref{finescan2}. Also listed therein are the corresponding run- and
tape numbers.
\begin{table}[htbp]
\begin{center}
\begin{tabular}{|r|c|c|r|}
\hline
$\bar{p}$-momentum & Run-Number & Tapes & Events \\
\hline
$1415\frac{MeV}{c}$ & 42041 - 42087 & & 834k \\ \hline
$1420\frac{MeV}{c}$ & 42087 - 42110 & & 460k \\ \hline
$1426\frac{MeV}{c}$ & 42111 - 42146 & & 570k \\ \hline
$1432\frac{MeV}{c}$ & 42147 - 42212 & & 1.235M \\ \hline
$1437\frac{MeV}{c}$ & 42407 - 42463 & & 1.145M \\ \hline
$1443\frac{MeV}{c}$ & 42464 - 42490 & & 448k \\ \hline
$1449\frac{MeV}{c}$ & 42491 - 42533 & & 505k \\ \hline
$1454\frac{MeV}{c}$ & 42534 - 42566 & & 549k \\ \hline
$1460\frac{MeV}{c}$ & 42567 - 42597 & & 659k \\ \hline
\hline
%%\hline
\end{tabular}
\end{center}
\caption[List of Accumulated Fine Scan Data]
{{\footnotesize {\em List of accumulated zero-prong data between October
28 and November 17. Note that for the fine scan momenta
(14xx$\frac{MeV}{c}$ the momenta are the names of the trigger files. The
exact values (as calculated by LEAR) are to be looked up in
~\ref{finescan1} }}}
\label{finescan2}
\end{table}

The fine scan had to be interrupted for a few days as serious machine
problems occured at LEAR (see below). In these days measurments were taken at a
momentum of 1642$\frac{Mev}{c}$ sharing the beam with PS185.

\subsubsection{900 and 1642 0-prong data}
List ~\ref{zerop} shows all data taken during the 0-prong run at 900 and
1642$\frac{MeV}{c}$:
\begin{table}[htbp]
\begin{center}
\begin{tabular}{|r|c|c|r|}
\hline
Trigger & Events @ 900 & Events @ 1642 \\ \hline
0-prong & 15.8M & 6.9M \\ \hline
\hline
%%\hline
\end{tabular}
\end{center}
\caption[List of 0-prong at 900 and 1642 MeV/c]
{{\footnotesize {\em List of accumulated zero-prong data between October
28 and November 17 for $\bar{p}$ momenta at 900 and 1642$\frac{MeV}{c}$. }}}
\label{zerop}
\end{table}



\subsection{18 November - 9 December 1996}

For testing purposes a few runs with bsvp1j1.sts (small bias in
~\ref{data3}) instead of the regular file were taken.
 \begin{table}[htbp]
\begin{center}
 \begin{tabular}{|l|r|r|}  \hline
  Trigger              & Events @ 1525 & Events at 1642 \\ \hline \hline
  O prong               & 10.035 M & 10.109 M \\
  2ormore              & 0.134M & 0.056M (since 2 Dec.) \\
  minimum bias         & 20.115M & \\ 
  small bias           & 0.164M & \\
  2 prong              & 4.479M & 12.403M \\ \hline
  \end{tabular}
\end{center}
 \caption[Statistics of 1525 and 1642 MeV]
{ {\footnotesize {\em
Summary of statistics for the 1525 and 1642 $\frac{Mev}{c}$ running}}}
 \label{data3}
 \end{table}

 


\section{Performance of Detector Components}
\subsection{Beam Counters}
At the beginning of the run period problems with the Si-centre counter
were reported (high noise level - bad signal/noise ratio). At 900
$\frac{MeV}{c}$ the efficiency was 85\% and went down to 75\% at
1800$\frac{MeV}{c}$. 

The following $\bar{p}$ stop condition was used (0-level):

  \begin{displaymath}
   \overline{p}_{stop} = (Si_{center}^{low} \wedge \overline{High}) \wedge
    (\sum_{i=1}^{4}{\rm OR}(Si_{i}^{low} \wedge \overline{High}))
    \; \; {\rm where} \; \;
    High = \sum_{i=1}^{4}Si_{i}^{high} \vee Si_{center}^{high}
  \end{displaymath}

The pile-up flag was provided by the proportional chamber (KC).


  The ratio of $Si_{center}\wedge\sum_{i=1}^{4}Si_{i} : KC$ constituted
  the criterion by which beam steering quality was monitored. These scalers
  were viewed on a CRT in the control room. A typical beam tune would reads
  85\% to 90\%of the beam going through the central silicon detector. 


\subsection{Silicon Vertex Detector}

The SVTX was used extensively in the triggers and performed well without
much attention during most of the time.

Channel 12 of the SVX was inactive during the 2-prong run at
900$\frac{MeV}{c}$. This was fixed during the break caused by the first
power failure. To check the performance of the SVX an additional 2-prong
trigger was set up to allow for 2 or more tracks.

 Extra noise in the backplane was
traced to a gating problem with the viking system and was fixed on 1.12.
96 by regenerating the NIM signal going into the CONV gate. This is also
believed to be the reason of few SVTX readout hangups.
\subsection{JDC}
On rare occasions the JDC tripped to unexpected high beam intensities
during data taking.
Otherwise the JDC performed reliably. 

Some FADC modules had to be replaced due to blown fuses.

A temporary problem concerning the JDC cooling was mentioned on 20.11.
96. This led to preamplifier tripping. More fluid to the preamp cooling
was added and the temperature trip set point was risen by 0.50 .
A broken wire on the preamp power supply was fixed during the run.
\subsection{Target}
No problems.
\subsection{Calorimeter}
The overall performance of the Calorimeter and its readout system was
reliable during most of the run.

\subsubsection{Crystals}
No problems to report.

\subsubsection{Readout}
A water leakage in the electronics hut caused problems with some
connections of FERA modules in the first week of the run period.

The two days power failure in November didn't result in serious FERA
problems except few bad linearities with crate 15, which disappeared
quickly after a short warming up period. FERA 1353 was reported to be
unstable.

The 2282 crystal readout worked fine during the run with the exception
of channel 984. The pedestals were unstable showing occasional changes
of +/- 100.

No problems were reported concerning the FACE and Lightpulser system.
\subsection{Magnet}
Due to power failure a magnet trip was reported which created some
problems with the water cooling.
\subsection{DAQ}
In principle the data aquisition system was working extremely stable.
Occasionally problems with j1xtal and j2xtal timouts occured and some
EVB hangups were reported. 
\subsection{LEAR}
Beam delivery was quite reasonable for most of the running period with
few minor problems like dipole instabilities, sudden and unexpected high
beam intensities (see JDC) etc. .


There were also some machine fall-outs.

The first two power failures occured during the first three weeks of the
run period. In the first instance the power failure caused a loss of 2
hours as only the cooling system of the JDC preamps was affected. The
second total power failure led to 14 hours beam loss.

 A special machine
problem occured during the {\em fine scan} period, which meant that only
four of the eight planned fine scan points could be measured in the
period originally forseen for the fine scan experiment
(4 Nov. - 8 Nov). The remaining scan
points were taken later (11 Nov. - 14. Nov.).

Another fall-out occured due to a general power failure on 30 November
which brought the entire CERN complex down. It took LEAR about 52 hours
to recover fully. 

For most of the time CB ran as the main user. Beam sharing with PS185
took place for testing purposes before 20 November and constantly after
20 November.

The servo system allowing to have a smooth start of the spill worked
fine.
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