\documentclass{chowto}

\title{Operating the HMS Vacuum Window Shutter}
\howtotype{user} % ``expert'', ``user'', ``reference''
%\experiment{Name of experiment} % Optional
\author{H. Fenker}
\category{hms} % Subject area of this document

%\maintainer{Name of person maintaining document} % Optional
\date{April 11, 2003} % Can use \today as the argument

\begin{document}

\begin{abstract}
This document describes the operational procedures for opening
and closing the HMS Vacuum Window Shutter.
\end{abstract}


\section{Related {\it Howtos}} 
The following Hall-C {\it Howto} documents may be helpful.

%--DELETE THOSE  DOCUMENTS MENTIONED HERE WHICH ARE IRRELEVANT
User Level Documents-
    \par \indent \indent Base Equipment Checklist \cite{howto:base_equip_checklist}
    \par \indent \indent Operating the HMS Shield House Door \cite{howto:open_hms_door}
    \par \indent \indent Operating the SOS Shield House Door \cite{howto:open_hms_door}

\section{Shutter Description}

The HMS vacuum volume extends from near the scattering chamber, through the three
quadrupoles and the dipole, up to the thin aluminum vacuum window just upstream
of the first HMS drift chamber. Because of the considerable stored energy in such
a large vacuum volume, it is necessary to protect personnel working in the HMS
shield house from the possibiliity of a catastrophic failure of this vacuum.
See Figure \ref{fig:hms_detector_vacuum}.

\begin{figure}[hbp]
\centering
\includegraphics[width=6in,height=5in]{open_hms_shutter-hms_detector_vacuum.eps}
\caption{The HMS vacuum window in the HMS spectrometer hut.
\label{fig:hms_detector_vacuum}}
\end{figure}

Protection is provided by a 1~inch thick aluminum plate which covers the large 
vacuum window in the HMS shield house. This plate slides up and down in an
assembly which is attached to the end of the vacuum vessel. Movement of the
shutter is managed by a motor which is controlled from a control box on the
outside of the shield house, on the left side of the door.

\section{Interlocks}
An interlock prevents access to the HMS detector hut unless the
safety shutter has been moved to its `down' position,
such that it covers the vacuum window. This is to prevent people from
accidentally touching the large vacuum window, or suffering hearing
loss should there be a catastrophic failure of the window. The shutter cannot
be retracted unless the door is closed. The door cannot be opened
unless the shutter is already inserted.

\section{Shutter Operation}
To close the shutter, press (and hold for a few seconds) the button labeled
``DOWN'' on the shutter control box. This will start insertion of the
shutter. After a few seconds the light indicating ``OUT'' will turn off.
It takes about two minutes for the shutter to move into place. When it
does, the light labeled ``IN'' will glow. This indicates that the shutter is inserted and
the door may be opened.

To open (i.e. {\it raise} the shutter, after the HMS shield house door has been fully
closed, press the button labeled ``UP'' and hold it for a few
seconds. The ``IN'' light will dim as the shutter moves away from
the fully inserted position. Full retraction takes about two minutes.
 When the shutter is fully retracted,
the ``OUT'' light will glow.

Usually the shutter is retracted by MCC operators after they have
swept the interior of the HMS shield house and closed the door.
Experimenters should watch the operators, using the hall survey
TV cameras, to make certain that they complete this step during
any sweep of the hall. If the operators complete the sweep of the
hall without opening the shutter, you will have to make a
controlled access and open the shutter yourself.

If you enter the HMS shield house during Controlled Access,
you are responsible for closing the door and raising the shutter yourself.

``IN'' and ``OUT'' shutter status lights are located both on the
shutter control box and on the top left panel of the Counting House
main console. You can check the status of the shutter from the
Counting House via these lights.

\end{document}

% Revision history:
% $Log: open_hms_shutter.tex,v $
% Revision 1.2  2003/04/11 23:13:06  saw
% (hcf) Some corrections
%
% Revision 1.1  2003/04/04 16:01:38  saw
% Initial Checkin
%
