\documentstyle[12pt]{report}
\begin{document}
%
\pagestyle{myheadings}

\baselineskip 18pt

\chapter[2\,m Chamber Vacuum Cycling and Gas Handling System at the ANU]
{2\,m Chamber Vacuum Cycling and Gas Handling System at the 
ANU\footnote{Authors: M.J.~Leddy and S.J.~Hall, University of
Birmingham. C.D.~Jones, University of York.}}
\today

\section{Introduction}

The 2\,m chamber is pumped by a combination of carbon-vane pumps, which
take pressure down from atmospheric to around 40\,mbar, vac-sorbs which
take pressure to 35\,microns ideally and finally a cryo-pump which
maintains the operating pressure in the $10^{-7}$\,torr range. The gas
handling is done by a unit similar in principle to the Daresbury units
(although a fraction of the size!) backed by a small rotary pump.
\newpage

\section{Evacuating the Chamber}

The valve status before
starting to pump should be:
\begin{itemize}
\item 2 valves to chamber (A and B) OPEN  
\item 2 valves to vacsorbs CLOSED
\end{itemize}
Valve~D below transducer OPEN so that digital guage reads pressure.
Ensure that the vacsorbs are cool or at least on the way.
Check that the gas-handling valves are in the following configuration:
\begin{itemize}
\item Gas-in valve (GD) on chamber wall CLOSED
\item Chamber equalisation valve (GH) OPEN
\item Detector input valve (GE) OPEN
\item Gas out valve (GF) to left of roughing line CLOSED
\item Beamline valves A and B SHUT. Beam hand valve OPEN.
\end{itemize}

\begin{itemize}
\item Lower chamber lid 
\begin{itemize}
\item Make sure everything is
clear and no plastic etc.\ has been left in the chamber. Switch control
to Down (no surprises there) and the lid will lower to within 1\,inch
of closing. Check the O-ring is seated and all is clear, then hold
down the "inch" button until the motor stops itself---don't just stop
because the lid looks like it is down.
\end{itemize}
\item Close valve~C
\begin{itemize}
\item If the airlock over the target region is to be used, ensure that the
large bore tube leading from the middle of the chamber lid is
connected to the roughing line (in front of the large plastic valve
handle on the right hand side of the line---valve~C in the figure) and
valve~C open. Two bolts is enough. If the airlock is not to be used,
close valve~C.
\end{itemize}
\item Switch on carbon vane and open valve E. 
\begin{itemize}
\item The thermocouple gauge should start to drop and the gas rack transducer reading
should also fall. If hybrid
gas detectors are being used then do not exceed 1mbar/sec pumping rate.
\end{itemize}
\item When the gas rack transducer reads less than 40\,mbar, close
valve~E and then switch off carbon-vane.
\item Open valve on small vacsorb.
\begin{itemize}
\item If the vacsorb is active you should
hear a hissing sound and the pressure should drop quite rapidly.
\end{itemize}
\item  Close valve~D.
\begin{itemize}
\item This isolates the gas rack transducer from the system due to small leak
in the gas lines at this point.
\end{itemize}
\item After 10-15 minutes close small vacsorb, open large vacsorb.
\begin{itemize}
\item {\bf Pressure must fall below 75\,microns on the vacsorb transducer before it is safe to open to the
cryo pump and usually the large vac-sorb can bring it down to about
35\,microns.}
\end{itemize}
\item Wait for thermocouple to drop below 60 microns and vacuum good/bad 
lights to turn to green.
\begin{itemize}
\item If this does not happen and you are impatient the protection on the
thermocouple can be switched off by moving the 2m thermocouple toggle switch
on the Target Line Vacuum Protection Unit to bypass-{\bf ONLY IF THE 
ROUGHING LINE THERMOCOUPLE IS $<$ 75~MICRONS.}
\end{itemize}
\item Close chamber valves~A and~B. Close vacsorb valves.
\item Switch the 2\,litre per second to bypass on the target line vacuum 
protection unit (TLVPU) and turn the range
switch on the 2\,litre per second guage to start (in that order).
\begin{itemize}
\item The orange vacuum fail light will come on on the 2l/s ion pump control unit.
\end{itemize}
\item Open the valve to the cryo-pump, called valve A on the TLVPU.
\begin{itemize}
\item The Thermocouple control unit should shoot down and the vacuum good light come on. The 2\,l/s ion pump control unit guage should
follow and the range can be set to 10\,mA or 1\,mA as needed.
\end{itemize}
\item When all vacuum good lights on TLVPU turn green switch all
bypass switches to protect.
\item Ensure chamber 2l/s pressure $<$ 70 $\mu$A and beamline valves A, B are shut.
\item Open beamline valve B between chamber and beamline.
\begin{itemize}
\item It is possible to hurry things along if necessary.
In this case ensure that the chamber 2l/sec guage reads $<$ 120$\mu$A. Then
on the line valve control unit (near quads) swith the line 2l/sec to 
bypass and open valve B between chamber and beamline. The vac 
fail light may come on but the line 2l/sec should read $<$ 120$\mu$A which is
OK. Pressure should continue to drop and vac fail light go out. At this point 
switch back to protect. Open valve A to beamline.
Nb- The line 2l/sec pump is located just upstream of the line A quads, the
reading is taken from a meter underneath the quads. If reading goes higher
than 10mA then shut valve B and let the pump recover. If this is not done then
pump can overheat.
\end{itemize}
\item With the system operational the following readings are to be expected:
\begin{itemize}
\item Gas rack transducer: 020 (nb - This is isolated from chamber)
\item Thermocouple control unit: 3 microns. Vacuum good light on.
\item TLVPU: Valve A open. Valve B shut. All vacuum good lights on.
\item 2 l/s ion pump control unit: $\sim$30 $\mu$a on 100$\mu$a setting.
Mains light on.
\item Carbon vane pressure transducer: 0. Thermocouple: full left ($<$1000
$\mu$m.
\end{itemize}
\end{itemize}
\newpage

\section{Venting}

{\bf *** Ensure biases are off the detectors ***}

\begin{itemize}
\item Shut beamline valves A and B.
\item Shut hand valve to beamline and insert holding pin if you want to leave this under vavuum. If not leave open.
\begin{itemize}
\item This valve is shut when the handle is pointing away from the chamber and the bellows are compressed.
\end{itemize}
\item Close cryo-pump valve (valve~A on vacuum control unit).
\item Ensure gas in valve~(GD) and gas out valve~(GF) on chamber wall are shut 
and the chamber equalisation valve~(GH) is open.
\item Open transducer valve~D.
\item Check pressure in roughing line indicated on the
thermocouple above the carbon-vane. If at atmospheric, rough out the
line using the carbon-vane. If the target line is attached, make sure
the valve~(C) is open so that this line is roughed out as well. If the line
is not attached make sure that C is shut.
\item If necessary attach nitrogen line to the roughing line.
\item Open valves~A and~B SLOWLY.
\item Allow nitrogen to enter the roughing line and chamber.
\begin{itemize}
\item Keep an eye on the
transducer reading---approximately 1\,mbar per second seems the usual rate to
vent at.
\end{itemize}
\item Watch the transducer reading and stop nitrogen flowing when
it reads approx 900\,mbar (local atmospheric pressure).
\begin{itemize}
\item If nitrogen
is allowed to flow beyond this pressure, the chamber lid will lift and
the O-ring may be damaged.
\end{itemize}
\item Slowly open the valve to the target line
(valve~C),assuming the line itself is not attached, so that the
chamber is open to the atmosphere.
\begin{itemize}
\item If the line is attached, the valve
should be open so that the target line is at the same pressure as the
roughing line. If this has not been done, open the valve now,
slowly. Then DISCONNECT the line, or it will be torn out when the lid
is lifted!
\end{itemize}
\item Lift the lid by about an inch, then check that the O-ring
has not lifted with it.
\begin{itemize}
\item This usually happens, so run a steel ruler
above the O-ring and let it drop back into place.
\end{itemize}
\item Raise chamber lid to required height.
\end{itemize}
\newpage

\section{Target Replacement System}
\subsection{Removing Existing Targets}
\begin{itemize}
\item Ensure that the chamber valve on top of the chamber is shut, that valve D is shut and the vacsorbs are cool.
\item Close beamline hand valve and beamline valve A as a precaution.
\item Connect up the target line to valve C and the N$_{2}$ line on top of the chamber.
\item Use carbon vane to pump out the target
line up to the chamber lid valve.
\begin{itemize}
\item Pressure can be measured on quage on top of
chamber.
\end{itemize}
\item Close valve E and open vacsorb valve.
\begin{itemize}
\item This will have removed most
of the gas from the system. The vacsorb should be left open at this point as
a safety.
\end{itemize}
\item Place the 2l/sec pump on the cryo on
bypass and open the valve on top of the chamber.
\begin{itemize}
\item The pressure in the
chamber will rise but should stay below 1mA before starting to drop again.
\end{itemize}
\item Remove target and shut valve on top of chamber.
\item Shut the vacsorb valve and valve C.
\item Place the target at 90$^{\circ}$ to the pumping line.
\item Open the N$_{2}$ line to the target replacement system and take line up to atmosphere.
\item Open flange on top of chamber and remove target.
\item As long as the vacuum is good then
the chamber 2l/sec ion pump can be placed back on protect and the scale changed 
back to 100$\mu$A.
\item The pressure in the chamber may now be slightly worse than
the pressure in the beamline. Therefore, put the beamline 2l/sec ion pump on
bypass before opening up the handvalve.
\item Wait for beamline 2l/sec ion pump to recover. Put beamline 2l/sec to
protect and open valve A to tandem.
\end{itemize}

\subsection{Placing new targets in Chamber}
\begin{itemize}
\item Close beamline hand valve and beamline valve A as a precaution.
\item Open valve C
\item Pump out the lines to the chamber lid valve using the carbon vane and vacsorb.
\item When the line is down to vacuum, place the chamber 2l/sec pump on the cryo on
bypass and open the
valve on top of the chamber (monitoring the chamber vacuum on the 
2l/sec ion pump as above).
\item Replace target, remove target rod and shut the chamber valve.
\item Close valve C.
\item Let line up to N$_{2}$.
\item As long as the vacuum is good then
the chamber 2l/sec ion pump can be placed back on protect and the scale changed 
back to 100$\mu$A.
\item The pressure in the chamber may now be slightly worse than
the pressure in the beamline. Therefore, put the beamline 2l/sec ion pump on
bypass before opening up the handvalve.
\item Wait for beamline 2l/sec ion pump to recover. Put beamline 2l/sec to
protect and open valve A to tandem.
\end{itemize}
\newpage

\section{Gas Handling system}

The gas flow is from a bottle behind the cryo-pump, through the
{\em transducer} panel to the control unit, through the gas-in and
detector in valves on the chamber wall, through the detectors, out via
the gas-out on the chamber wall and through a rotary pump.  There are
2 sensors in the control unit, one labelled HI, in the output line
which ranges up to atmospheric pressure, and one labelled LO in the
input line which reads up to about 10\,torr. For our purposes the HI
sensor will always be used assuming we are running at pressures $> 10$\,torr.

While the chamber vacuum is being cycled the valves should be in the
following status:
\begin{itemize}
\item 2 valves before the transducer (GA and GB) CLOSED
\item Transducer valve CLOSED (valve D)
\item Gas-in on control unit CLOSED (GC)
\item Exhaust valve on control unit CLOSED (GG)
\end{itemize}
In the triangle of valves on the chamber wall: 
\begin{itemize}
\item Gas-in CLOSED (GD)
\item Detector in OPEN (GE)
\item Chamber valve OPEN (GH)
\item Gas out valve to the left of the roughing line CLOSED (GF)
\item Proportional control valve set to `close'
\end{itemize}
Valve below gas-out is redundant but should be closed 

\subsection{Introducing Gas}

{\bf Gas should only be introduced into the detectors after the chamber pressure
has dropped below 250$\mu$A on chamber 2l/sec ion pump.}
\begin{itemize}
\item Shut beamline valves A and B. 
\item Turn on rotary pump below gas control panel and open gas out~(GG) on
control panel. 
\begin{itemize}
\item This pumps from the rotary pump, through
exhaust valve~(GG), to chamber gas out valve~(GF).
\end{itemize}
\item Shut gas bottle valve and gas regulator valve just above bottle.
\item Switch on carbon vane and open valve~E. Close valve~E and switch off
carbon vane after lines pumped out.
\item Switch proportional valve to LO and open vacsorb valve and transducer valve~D
\begin{itemize}
\item This evacuates between the propane bottle and the chamber gas-in valve~(GD).
The proportianal valve readout should read 0 by the end of pumping.
\end{itemize}
\item Open (in this order) valves GA, GB and GC. Switch the proportional valve
rotary pot to OPEN.
\begin{itemize}
\item Should see -ve gas flow in the flow rate meter at this stage.
\end{itemize}
\item Set proportional valve toggle switch to HI.
\item When lines have been roughed out, close transducer valve~(D) and 
valves~(GA and (GB).
\begin{itemize}
\item Leave vacsorb open for emergencies
\end{itemize}
\item Close chamber~(GH) valve on chamber wall. Check that exhaust valve~(GG)
is open. Open gas out valve~(GF) and then slowly open gas-in valve~(GD).
\begin{itemize}
\item Recheck that proportional
valve is reading 0, that the proportional valve is on the 10~V full scale 
setting and that the HI setting has been selected. 
\end{itemize}
\item Put the control 
switch on {\em auto} on the control box and ensure i/p line pressure is 
approx zero and the green status light is lit, as opposed to the red one.
\item Close valve GC as a safety.
\begin{itemize}
\item This means that the system is in its equilibrium state, which in turn means 
that you are starting off with the proportional valve fully closed as you
should. This is adjusted using the rotary pot, which may not read zero
for fully closed but probably will be near.
\end{itemize}
\item Fully open the valve on the
centre of the gas cylinder lid. 
\item Open the pressure regulator on the side
of the gas bottle until the 200 line can be read.  
\item Open the left hand valve on the {\em transducer} panel one
turn or less~(GA). 
\item Open the valve~(GB) very slowly.
\begin{itemize}
\item This is the 
needle valve which controls the gas supply pressure (eventually 
you will want this to give a reading of about 1000\,mbar (usually 1077\,mbar) on the transducer 
valve's digital read out). If the transducer won't go up to $\sim$1077 mbar then
open GA a bit further. 
\end{itemize}
\item Open GC fully. 
\begin{itemize}
\item The flow meter should register but the green 
status light remain lit.  Pressure in the detectors is then controlled 
by the control pot, and the central digit meter on the gas control box 
gives you the pressure in VOLTS (where for the HI 
range 10\,V~=~1\,atmosphere, approximately 760\,torr, and on the LO 
range 1\,V~=~1\,torr ).  Do NOT touch the 
toggle switch when the control is set to auto. If the toggle is changed, the
proportional valve will go crazy.

\item You should now be ready to introduce gas into the detectors. Monitor the 
digital pressure readout of the proportional valve, the flow rate meter and
also the 2l/sec readout below the vacuum protection unit. This 2l/sec readout
is important as it monitors the pressure in the chamber. 
\end{itemize}

\item Open proportional valve
slightly using the control pot. 
\begin{itemize}
\item The status light on the proportional valve should remain green. If it
goes red then you are opening too fast, stop and wait for it to recover.
\end{itemize}
\item With some gas in detector ($\sim$0.2~V on digital readout) close the gas
exhaust valve~(GG) until flow meter $\sim$100~scc/min. Introduce more gas 
by opening proportional valve control pot until required pressure is reached
(while continually checking 2l/sec pressure, if this goes very bad then wind down the proportional valve control pot and open valve D to the vacsorb). As you
do this keep closing exhaust valve~(GG) to keep flow rate at $\sim$100~scc/min.
\begin{itemize}
\item If the flow rate goes off scale and the control pot status light remains green 
then no worries! It just means that you should shut GG slightly.
\end{itemize}
\item After reaching the required pressure (eg. 1~V $\equiv$ 76 torr) make sure that
the flow rate is $\sim$40-60 scc/min. Close vacsorb and switch gas control, on
bottom of gas control unit, to protect.
\end{itemize}
During the run monitor...
\begin{itemize}
\item Gas flow rate ($\sim$40-60 scc/min)
\item Detector gas pressure ($\sim$1~V Digital readout on gas control).
\item Transducer Pressure ($\sim$1077~mbar).
\item Chamber pressure ($\sim$70 $\mu$A 2l/sec guage below vacuum protection unit).
\item Status green on proportional valve control pot.
\end{itemize}

\subsection{Removing Gas}

To vent the chamber with hybrid detectors inside...
\begin{itemize}
\item Close valves A and
B to the beamline and close valve A to the cryo. on Target Line Vacuum Protection Unit (TLVPU)
\item Switch from protect to bypass on gas control lower unit (below proportional control valve)
\item  Close the proportional valve
by winding down the control pot to 0 and switching it from auto to close.
\item Close GC and open GG fully. 
\begin{itemize}
\item This should pump the gas out of the detectors
until eventually the flow rate is very low and the digital pressure
readout is $\sim$0 (usually $\sim$0.05).
\end{itemize}
\item Close GB and GA to stop any more gas entering the gas control
system. 
\item close gas bottle valves.
\item Close GF and GG to stop pumping of gas from detectors. 
\item Switch 2l/s ion pump to bypass on TLVPU.
\begin{itemize}
\item Otherwise it tries to shut valve A to the cryo.
\end{itemize}
\item Open GH to
couple the detectors with the chamber. 
\begin{itemize}
\item The transducer  will still be reading $\sim$1077 mbar. The gas from here can
be pumped out using the carbon vane. 
\end{itemize}
\item Make sure that chamber valves A and
B are shut as well as GA, GB and GC. 
\item Switch on carbon vane and open valve E
(on carbon vane) and valve~D.
\begin{itemize}
\item This will pump out the carbon vane line down to $\sim$40 mbar. 
\end{itemize}
\item Close valve E and switch off carbon vane. 
\begin{itemize}
\item If you've got a working vacsorb then you can pull more gas out of the carbon vane line,
otherwise the remaining gas can be let into the chamber. 
\end{itemize}
\item Check that GF and GD are closed and that GH is open.
\item Slowly open
valve A on chamber wall. 
\begin{itemize}
\item This should release the gas into the chamber through
the detector. 
\end{itemize}
\item After pressure in transducer has dropped to 0 then slowly open
chamber valves A and B. 
\begin{itemize}
\item The N$_{2}$ can now be let into the chamber and
detectors.
\end{itemize}
\item Slowly open N$_{2}$ valve on plastic tube and then open N$_{2}$
valve on pumping rig. 
\begin{itemize}
\item Transducer pressure should start to increase from 0
to 900 at a rate of $\sim$1~mbar/sec. 
\end{itemize}
\item When transducer pressure reaches 900 mbar then shut N$_{2}$
valves, open valve C and lift the lid. 
\item Turn off rotary pump below gas control.
\end{itemize}




\end{document}


