\documentstyle[a4,psfig,12pt]{article}
\pagestyle{empty}
\begin{document}


\setlength{\unitlength}{1cm}
\noindent
\begin{picture}(0,0)
\put(0,2.5){\makebox(0,0)[l]{CH/meet/97/03}}   %% Reference number of document
\end{picture}

\noindent
\begin{minipage}[t]{10cm}
\fbox{
\parbox[t]{6.5cm}{
{\large {\bf Minutes}}\\[2mm]
Oxford DA meeting 21/11/97
}}\\[7mm]
\makebox[2.5cm][l]{Author:} SPGC, WDMR\\[2mm]
\makebox[2.5cm][l]{Date:} 24 November 1997\\[2mm]
\end{minipage}
\hfill \raisebox{-2.5cm}{
\psfig{figure=/home/chappell/texegs/egs/char-encap.ps,height=3cm}}\\[2mm]
\noindent
Present : Steve Chappell, Dick Hunt, Bill Rae, Martin Freer, Nobby Clarke,
Paul Jagpal and Steve Singer.\\
Circulation : Charissa-staff\\

The document CH/DOC/97/04 ``Report from ANU'' formed the basis of the
discussion. Please refer to actions outlined in that report as well as
those below.

\begin{enumerate}

\item{Steve Chappell reported on the outstanding problems with the DA
system. These are:}

i. TDC ringing\\
ii. WAG board failures\\
iii. Fiacre problems

\item{Dick Hunt reported on these problems and solutions:}

i. The TDC's are very sensitive and when many input lines change
at the same time ringing can occur. This is not so obvious looking
at the input signals on a scope but it is very clear inside the TDC
where two short pulses can be seen.

There is a very simple mod to the TDC (one wire) which would enable
the inputs to the TDC's to be gated off at the time when all channels
are firing ie the start of rundown. This seems to cure the problem
in tests here. But final tests need to be done at ANU in situ.

The TAIL modules will supply this pulse and thus need to be modified.
It was also noted that CAMAC power rails had to be close to specification
to get the best performance from the TDC's.

ii. The WAG problem relates to channels not firing sometimes and
WAG channels going down. Two cures for this problem. The first is
to install pull-up resistors where necessary so that when cables
are removed various signals do not float - which can cause the
problem since the crate may go into oscillation.

Certain chips on the WAG boards will be replaced by more powerful
versions. The only other chips which seem to blow are the CAT
amplifier chips. Hopefully the above mod with pull up resistors
might improve this.

iii. The FIACRE has been modified to look at the data coming off
the TDC. The new version can identify double time and energy
hits and will take the first hit rather than the second which
may be due to ringing. 


\item{Other matters which came up included:}

i. Problems with Silena boards. If there is an apparent problem
with a Silena sample and hold then it is better to swap the whole
amplifier rather than just the Silena. The Silena sample and
hold circuits have to be set up very carefully in each amplifier.
If one swaps Silena's this setting up must be done first.

ii.There may be a problem with the power contollers on the
amplifier crates. There are reports that these have dropped
the voltage on the output lines by a large amount. It is
possible that the opposite could happen thus damaging modules.

\item{Other developments are:}

i. A simple logic box has been built which will take the
logical output (after the discriminator) from up to
4 Multiplicity units and convert these to fast NIM. NIM
logic (eg scaledowns ) can then be used and a new MP
signal can be sent back to the DA system.

One of these modules has been tested. Two more are
required for the run in January.

ii. Dick is still working on the FACET which will replace the
Starburst. The new version will buffer a whole event making
the transfer to the HSM more reliable.

\item{The requirements for the run in January were discussed.}

i. SMS will get the working Scaler back from Strasbourg and send
off the broken Scaler to Lecroy.

ii. Paul will get the Exabyte drives refurbished in time to
go out to ANU with the next shipment on 12 Dec.

iii. SMS reported that VP has changed the way the DA system and
the amplifiers are controlled. He will use multiple RS232 and
hopefully this will speed up these processes.

iv. The display on Charissa1 at ANU is U/S. SMS will deal with this.

v. The spare disk with the backup of the DA software will be
updated with the current versions of the software.

vi. We need to have some measure of deadtime for the next run.
SPGC will look into this.

vii. Check event format [SMS/SPGC].

viii. The new RH tester units needs to be repaired. This checks
out strip cables and CAT outputs.

ix. RH will modify the TAIL's, WAG's etc on site at ANU. The new
FIACRE modules may also be installed if there is time. He will
also mod the TDC's on site.

x. SSJ to provide Silena set-up documentation and complete test rig.

xi. Faulty amps to be repaired and returned [SSJ].

xii. Lemo terminators ordered through ANU [SPGC].

\item{Other matters:}

MF reported on the Trigger System. He is waiting for a final
unit from York. He needs this module urgently if he is to
be ready to install the Trigger system in March before the
next MEGHA runs. Action DLW.

\end{enumerate}

\end{document}
