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 \title{Controls in EUROGAM}
 \author{M.M. Aleonard}
 \date{2 July, 91}
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EDOC125\par


 \section{INTRODUCTION}


 This paper  deals  with  the  controls  of  the  EUROGAM  array  during  an
 experiment. Those controls suppose that the array is in  correct  order  of
 function setups and checkings having been previously done.  (see  Edoc  067
 "Diagnostic procedure for EUROGAM D. Brightly and  P.  Coleman-Smith and
 also Edoc 043 on EUROGAM diagnostic software M.M. Aleonard).
 Those controls will need informations  available  in  different  files  (or
 structure) in the setups and checkings phases.
 The aim of the controls is to check that all counters, the  electronics  and
 the software are running correctly. There are several kinds of controls:

	  - count rate controls (check all detectors,...)

	  - gain and shift control

	  - data flow controls (event builder, tape...)

	  - H V

 \section{COUNT RATE CONTROLS}

 Count rate controls should be performed at given time interval. Two  options
 could be possible: erase after read or not erase. If data are not erased
 control
of the data rate will be performed by substraction of the previous readout.
The time interval will be selectable; standard values could be suggested (10
mn, 30 mn ...).
It is most likely that the acquisition should be stopped while reading scalers
and histograms. Sequence: stop trigger unit - read data - restart trigger
unit.

Controls can be performed via the following:

\subsection{Scalers}

Scalers are available in the trigger unit located in the VXI crate:

	- fast trigger

	- validations

	- fast trigger rejection while busy

	- fast trigger accepted

The systematic use of scalers on all CFD output from Ge cards does not seems
necessary as long as informations
can be obtained in the histograms. However a VME scaler unit would be useful
for diagnostics?

\subsection{Histograms}

Two kinds of histograms are available from the histogrammer unit or the sorter
unit. While
in the histogrammer we have raw and no gain  matched data the sorter can
provide corrected data besides these data
are filtered in the event builder then the sorter.

Note: the histograms to be used for controls should not be reselected without a
security
check even in the sorter unit. Also: in the histogrammer spectra are those
events
selected by the master trigger unit.

The histogrammer is the only point where BGO can be checked since that in most
experiments their output does
not go further than the event builder.

The A.C. and pile up rejected spectra could also be checked here if the space
needed is too
 big it is worth counting
the A.C. and pile up data of Ge {\bf in the event builder crate} idem for
histogram of BGO
hits deduced from the pattern.
(At this point the spectrum is not necessary). This histogram of each BGO hit
is necessary to help control the threshold or problems on the shields. To avoid
smearing spectra over a wide energy range control of the CFD threshold can be
performed by
integrating spectra up to 200 kev only for Ge low gain.
Calculation of peak to background ratio in each Ge need to be done either in
the histogrammer if
the trigger filtering is enough to get clean spectra or in the sorter unit.
These peaks can be a inixing of several channels but the background need to be
"clean" around. These features needs 45 (phase 1) Ge A.C and p.u. rejected
spectra with not too strong filtering (just Multiplicity window?) to get enough
counts for control.
Control of the target  yield is obtained from the scalers in the trigger unit,
but effect of beam misalignemment may be checked also by counting background
in low energy for the rear detectors.

\section{CONTROL MANAGING}

An organisation of all the controls has to be done. There are several aspects:
settings histograms needed for control, starting the controls, visualisazation
on a screen in such a way that a quick glance gives an overview of
 the status of the experiment.

\subsection{Software utilities}

Software facilities have to be provided for automatic checkings (at given
time interval) and passing results to a graphic interface for errors or to
update
histograms display.

Facilities also are needed to give parameters for parametrization of controls:
 selection of peaks... This includes a user interface to get a spectrum of
 selected regions with markers set but also to have an automatic correction
 {\it on option} of gain matched (
doppler corrected) histogrammer. This interface could be some interface between
the spectrum server and the client. This facility is absolutely necessary to
avoid
tedious scanning of spectra with a different gain in the histogrammer and the
sorter.

The control facility must check gain shifts on some 2 - 4 peaks in each Ge.
A.C. and P.u
rejected spectrum. Control of the resolution may not be easy in beam, use of a
source each day was a suggestion.
Note that, this imply changing the trigger setup!

\subsection{Graphic for controls}

The screen should present histograms of counts rate in detectors,
A.C. qualities of each detector control of events rates (scalers and tapes
rate)
and status (running , errors) of histogrammer sorter, trigger. On request a
fast scanning
of reference peaks (small energies regions) should be available.
On request access to more detailed informations on hight voltages(histograms)
and trigger programming. Presentation should emphasis anomalies (change to red)
if the limits of evolution of parameters can be fixed.


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