\documentclass{chowto}

\title{Monitoring HMS ``Utilities'' Systems}
\howtotype{user} % ``expert'', ``user'', ``reference''
%\experiment{Name of experiment} % Optional
\author{H. Fenker}
\category{hms} 

%\maintainer{Name of person maintaining document} % Optional
\date{April 4, 2003} % Can use \today as the argument

\begin{document}
\providecommand{\degg}{\ensuremath{^{\circ}\ }}

\begin{abstract}
Herein is descirbed how to verify the status of the services
required by the detectors in the HMS:
high and low-voltage electrical supplies, gas, and environmental
conditions. Basically, these are the {\it utilities} that the
detectors need in order to function. They should be continuously
monitored or, at a minimum, manually checked at least one time
during each eight-hour shift while the detectors are to be 
kept ready for data. 

Note that users must also check the {\it quality} of the data
produced by the detectors. Maintenance of the {\it utilities}
described here is necessary but not necessarily sufficient
to maintain good detector performance.

\end{abstract}


\section{Room Temperature}

The ambient temperature inside the HMS shield house is indicated
by one of the two temperture gauges mounted on the wall of the 
Counting Room above the far left of the control console. The
reading is in degrees Fahrenheit, and should be no higher than
about $75\degg F$.

\section{Drift Chambers}

The HMS includes two identical drift chambers, each of which
contains six planes of sense wires. 

\subsection{High Voltage}

Each sense plane requires
three high-voltage supplies (denoted ``triangle'', ``square'',
and ``circle''). Further, each chamber uses an additional
high-voltage channel to supply the ``guard'' wires. The 
nominal voltages are shown in \cite{howto:hms_nominal_settings}.
Check and modify the voltages using the High Voltage GUI
\cite{howto:caen_hv_gui}. Readback voltages should be within
about 20~V of the setpoint voltages. Normally the GUI
monitors the voltages and sounds an alarm if a channel is out of tolerance.
In this case, the user must simply verify that the alarm has
not been turned off. Typical currents in the wire chambers are less 
than 10~$\mu$A.


\subsection {Low Voltage}

The drift chamber preamplifiers, located on the side and top of
the chambers, require three supply voltages: +5V, -5V, and 
V$_{threshold}$. The $\pm 5V$ supplies are located in the HMS
shield house and cannot be monitored remotely. (If one of them
dies or a fuse blows, the entire effected chamber will have
no hits.) The threshold-voltage supplies, one for each chamber,
are located in rack
CH03B10 in the Counting house Electronics Room. The nominal
V$_{threshold}$ is noted in \cite{howto:hms_nominals}. 
It is only to be altered
by a staff expert, who will post the new nominal value at the
power supply if it differs from the value mentioned here.

These threshold voltages should be checked using {\bf only}
the digital voltmeter built in to the power supply. 

\subsection {Gas}

The drift chambers must be continuously flushed with fresh
operating gas. The gas is supplied from the gas shed. It is
composed of approximately 49.5\% argon, 49.5\% ethane, and
1\% {\it 2-propanol} (isopropyl alcohol). This mixture is automatically
controlled by the gas mixing system \cite{howto:drift_gas_system}.
Users must simply verify that the readings in the gas shed
are correct and that the gas supply does not run out. The
amount of argon left in a bottle can be determined from the
bottle pressure, while the ethane content may only be measured
by observing the drop in gross bottle weight. Physicists
should understand why this is true.

Nominal settings are given in \cite{howto:hms_nominal_settings}.

\section{Trigger Scintillators}

The trigger scintillators consist of two sets of crossed
scintillator paddles (H1X, H1Y) and (H2X, H2Y). Each paddle
has two phototubes (one at each end). The $X$ planes have
sixteen paddles and the $Y$ planes have ten paddles each.

A hodoscope system expert will determine the appropriate high
voltage for each of the 104 phototubes during the commissioning
period of each experiment. Check the logbook for a record of what
the present values are -- they should also be saved by the HV GUI.
The settings listed in \cite{howto:hms_nominal_settings}
are typical values only. 

All of the HMS hodoscope tube bases have a load resistance of $1M\Omega$
and should, therefore, draw in the neighborhood of 2.5~mA for a
supply voltage of 2500~V.

\section{Aerogel \v{C}erenkov Counter}

The aerogel \v{C}erenkov counter needs high voltage for each of
its phototubes. System experts will update the settings in the
HV GUI and make a log entry. High voltages are monitored by the
GUI, which sounds an alarm in case of error (if the GUI is running).
Typical voltage settings are given in \cite{howto:hms_nominal_settings}.

\section{Gas Cerenkov Counter}

The HMS Gas \v{C}erenkov needs high voltage for each of its
two photomultiplier tubes and needs to have constant pressure
and temperature.  

\subsection{High Voltage}
The high voltages are supplied by the HMS
high voltage GUI, of course. The PMT bases for the gas \v{C}erenkov
use {\it positive} high voltage. Note that all the other PMT bases 
in the HMS are designed for use with {\it negative} HV. 
They operate at between 2000 and 2700 Volts.  Nominal voltages
are given in \cite{howto:hms_nominal_settings}.


\subsection{Pressure and Temperature}
The pressure and temperature are
displayed by digital indicators located underneath the shield
house, near the primary magnet control screen. The displays
are viewed by a TV camera feeding a monitor in the Counting
Room. The two numbers shown are the temperature in $C\degg$
and the pressure in psia. See \cite{howto:hms_nominal_settings}.
The nominal pressure varies by experiment; the desired value
should be noted in the logbook during experiment commissioning.

\section{Lead-glass Calorimeter}

The calorimeter consists of four layers of thirteen glass blocks
each. Layers A and B have two phototubes per block. layers $C$ and
$D$ have one tube per block. The HV GUI will sound an alarm if
a channel's voltage differs significantly from the setpoint.
Typical voltages are shown in \cite{howto:hms_nominal_settings}.

\section{Related {\it Howtos}}
\begin{itemize}
\item High Voltage GUI
\item HMS Nominal Settings \cite{howto:hms_nominal_settings}.
\end{itemize}

\end{document}

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% Revision 1.1  2003/04/04 16:02:23  saw
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