1 saw   1.1 \documentclass{chowto}
  2           
  3           \title{Monitoring HMS ``Utilities'' Systems}
  4           \howtotype{user} % ``expert'', ``user'', ``reference''
  5           %\experiment{Name of experiment} % Optional
  6           \author{H. Fenker}
  7           \category{hms} 
  8           
  9           %\maintainer{Name of person maintaining document} % Optional
 10           \date{April 4, 2003} % Can use \today as the argument
 11           
 12           \begin{document}
 13           \providecommand{\degg}{\ensuremath{^{\circ}\ }}
 14           
 15           \begin{abstract}
 16           Herein is descirbed how to verify the status of the services
 17           required by the detectors in the HMS:
 18           high and low-voltage electrical supplies, gas, and environmental
 19           conditions. Basically, these are the {\it utilities} that the
 20           detectors need in order to function. They should be continuously
 21           monitored or, at a minimum, manually checked at least one time
 22 saw   1.1 during each eight-hour shift while the detectors are to be 
 23           kept ready for data. 
 24           
 25           Note that users must also check the {\it quality} of the data
 26           produced by the detectors. Maintenance of the {\it utilities}
 27           described here is necessary but not necessarily sufficient
 28           to maintain good detector performance.
 29           
 30           \end{abstract}
 31           
 32           
 33           \section{Room Temperature}
 34           
 35           The ambient temperature inside the HMS shield house is indicated
 36           by one of the two temperture gauges mounted on the wall of the 
 37           Counting Room above the far left of the control console. The
 38           reading is in degrees Fahrenheit, and should be no higher than
 39           about $75\degg F$.
 40           
 41           \section{Drift Chambers}
 42           
 43 saw   1.1 The HMS includes two identical drift chambers, each of which
 44           contains six planes of sense wires. 
 45           
 46           \subsection{High Voltage}
 47           
 48           Each sense plane requires
 49           three high-voltage supplies (denoted ``triangle'', ``square'',
 50           and ``circle''). Further, each chamber uses an additional
 51           high-voltage channel to supply the ``guard'' wires. The 
 52           nominal voltages are shown in \cite{howto:hms_nominal_settings}.
 53           Check and modify the voltages using the High Voltage GUI
 54           \cite{howto:caen_hv_gui}. Readback voltages should be within
 55           about 20~V of the setpoint voltages. Normally the GUI
 56           monitors the voltages and sounds an alarm if a channel is out of tolerance.
 57           In this case, the user must simply verify that the alarm has
 58           not been turned off. Typical currents in the wire chambers are less 
 59           than 10~$\mu$A.
 60           
 61           
 62           \subsection {Low Voltage}
 63           
 64 saw   1.1 The drift chamber preamplifiers, located on the side and top of
 65           the chambers, require three supply voltages: +5V, -5V, and 
 66           V$_{threshold}$. The $\pm 5V$ supplies are located in the HMS
 67           shield house and cannot be monitored remotely. (If one of them
 68           dies or a fuse blows, the entire effected chamber will have
 69           no hits.) The threshold-voltage supplies, one for each chamber,
 70           are located in rack
 71           CH03B10 in the Counting house Electronics Room. The nominal
 72           V$_{threshold}$ is noted in \cite{howto:hms_nominals}. 
 73           It is only to be altered
 74           by a staff expert, who will post the new nominal value at the
 75           power supply if it differs from the value mentioned here.
 76           
 77           These threshold voltages should be checked using {\bf only}
 78           the digital voltmeter built in to the power supply. 
 79           
 80           \subsection {Gas}
 81           
 82           The drift chambers must be continuously flushed with fresh
 83           operating gas. The gas is supplied from the gas shed. It is
 84           composed of approximately 49.5\% argon, 49.5\% ethane, and
 85 saw   1.1 1\% {\it 2-propanol} (isopropyl alcohol). This mixture is automatically
 86           controlled by the gas mixing system \cite{howto:drift_gas_system}.
 87           Users must simply verify that the readings in the gas shed
 88           are correct and that the gas supply does not run out. The
 89           amount of argon left in a bottle can be determined from the
 90           bottle pressure, while the ethane content may only be measured
 91           by observing the drop in gross bottle weight. Physicists
 92           should understand why this is true.
 93           
 94           Nominal settings are given in \cite{howto:hms_nominal_settings}.
 95           
 96           \section{Trigger Scintillators}
 97           
 98           The trigger scintillators consist of two sets of crossed
 99           scintillator paddles (H1X, H1Y) and (H2X, H2Y). Each paddle
100           has two phototubes (one at each end). The $X$ planes have
101           sixteen paddles and the $Y$ planes have ten paddles each.
102           
103           A hodoscope system expert will determine the appropriate high
104           voltage for each of the 104 phototubes during the commissioning
105           period of each experiment. Check the logbook for a record of what
106 saw   1.1 the present values are -- they should also be saved by the HV GUI.
107           The settings listed in \cite{howto:hms_nominal_settings}
108           are typical values only. 
109           
110           All of the HMS hodoscope tube bases have a load resistance of $1M\Omega$
111           and should, therefore, draw in the neighborhood of 2.5~mA for a
112           supply voltage of 2500~V.
113           
114           \section{Aerogel \v{C}erenkov Counter}
115           
116           The aerogel \v{C}erenkov counter needs high voltage for each of
117           its phototubes. System experts will update the settings in the
118           HV GUI and make a log entry. High voltages are monitored by the
119           GUI, which sounds an alarm in case of error (if the GUI is running).
120           Typical voltage settings are given in \cite{howto:hms_nominal_settings}.
121           
122           \section{Gas Cerenkov Counter}
123           
124           The HMS Gas \v{C}erenkov needs high voltage for each of its
125           two photomultiplier tubes and needs to have constant pressure
126           and temperature.  
127 saw   1.1 
128           \subsection{High Voltage}
129           The high voltages are supplied by the HMS
130           high voltage GUI, of course. The PMT bases for the gas \v{C}erenkov
131           use {\it positive} high voltage. Note that all the other PMT bases 
132           in the HMS are designed for use with {\it negative} HV. 
133           They operate at between 2000 and 2700 Volts.  Nominal voltages
134           are given in \cite{howto:hms_nominal_settings}.
135           
136           
137           \subsection{Pressure and Temperature}
138           The pressure and temperature are
139           displayed by digital indicators located underneath the shield
140           house, near the primary magnet control screen. The displays
141           are viewed by a TV camera feeding a monitor in the Counting
142           Room. The two numbers shown are the temperature in $C\degg$
143           and the pressure in psia. See \cite{howto:hms_nominal_settings}.
144           The nominal pressure varies by experiment; the desired value
145           should be noted in the logbook during experiment commissioning.
146           
147           \section{Lead-glass Calorimeter}
148 saw   1.1 
149           The calorimeter consists of four layers of thirteen glass blocks
150           each. Layers A and B have two phototubes per block. layers $C$ and
151           $D$ have one tube per block. The HV GUI will sound an alarm if
152           a channel's voltage differs significantly from the setpoint.
153           Typical voltages are shown in \cite{howto:hms_nominal_settings}.
154           
155           \section{Related {\it Howtos}}
156           \begin{itemize}
157           \item High Voltage GUI
158           \item HMS Nominal Settings \cite{howto:hms_nominal_settings}.
159           \end{itemize}
160           
161           \end{document}
162           
163           % Revision history:
164           % $Log$