1 saw   1.1 \documentclass{chowto}
  2           
  3           \title{Changing SOS Gas Cerenkov PMTs}
  4           \howtotype{expert} % ``expert'', ``user'', ``reference''
  5           %\experiment{Name of experiment} % Optional
  6           \author{Glen Warren}
  7           \category{sos} % Subject area of this document
  8           %\maintainer{Name of person maintaining document} % Optional
  9           \date{July 7, 2003} % Can use \today as the argument
 10           
 11           \begin{document}
 12           
 13           \begin{abstract}
 14           Instructions on how to remove and install PMTs for the SOS gas
 15           Cerenkov detector.
 16           \end{abstract}
 17           
 18           \section{Introduction}
 19           
 20           The detector employs four Burle 8854 PMTs. These are large 5''
 21           diameter, 14 stage tubes. They are housed in magnetic shields, and
 22 saw   1.1 look through Winston cones, parabolic mirrors that funnel photons
 23           to the photocathode. 
 24           
 25           \section{Removal}
 26           
 27           To remove a phototube from the detector, do the
 28           following: 
 29           
 30           \begin{enumerate}
 31           
 32             \item {\em Remember never to touch or apply force to the phototube
 33             face. This glass/metal seal is very fragile!}
 34           
 35             \item Loosen the hose clamps that connect the phototube and base and
 36             remove the base.
 37           
 38             \item Remove the six brass nuts that hold the phototube flange to the
 39             detector tank.
 40           
 41             \item Remove the whole phototube assembly (tube, flange, Winston cone
 42             and support) taking care not to bump the Winston cone on the hole in
 43 saw   1.1   the tank. The assembly is somewhat ``off balanced'' and a little
 44             heavy. It has been found that a round office waste basket is very
 45             useful in supporting this assembly, tube up, on a work bench.
 46           
 47             \item Loosen, but do not remove, the three, small, regular head
 48             screws that hold the Winston cone back against the phototube face.
 49           
 50             \item Undo the three Allen bolts that connect the aluminum ring
 51             (connected to the back of the Winston cone) to the flange (via the
 52             brass rods). The Winston cone should now be free.
 53           
 54             \item Now wiggle the magnetic shield, with the tube inside, free of
 55             the aluminum cylinder and flange. Take care not to let the phototube
 56             fall out of the shield. It's a little tight because there is an
 57             O-ring inside that forms the gas seal.
 58           
 59             \item Finally, remove the plastic ring from the face of the tube,
 60             and then remove the tube from the magnetic shield.
 61           
 62           
 63           \end{enumerate}
 64 saw   1.1 
 65           \section{Installation}
 66           
 67           To replace a phototube, do the following: 
 68           
 69           \begin{enumerate}
 70           
 71             \item {\em Remember never to touch or apply force to the phototube
 72             face. This glass/metal seal is very fragile!}
 73           
 74             \item Place the flange on top of an office waste basket with the
 75             aluminum cylinder pointing down.
 76           
 77             \item Insert the O-ring into the back of the wide part of the
 78             magnetic shield, slide the phototube in, and place the plastic ring
 79             around the face of the tube.
 80           
 81             \item Wiggle the magnetic shield into the aluminum cylinder/flange.
 82           
 83             \item Place the Winston cone assembly onto the front of the magnetic
 84             shield. The three small, regular screws should be loose. Note that
 85 saw   1.1   the shield should catch on the small lip on the inside of the
 86             aluminum ring connected to the cone. Tighten the three Allen bolts
 87             that attach the cone assembly to the flange via the brass rods.
 88           
 89             \item Center the Winston cone on the phototube by gently pushing the
 90             cone up against the plastic ring around the phototube. There is no
 91             need to apply force! Tighten the small screw holding the cone in
 92             place.
 93           
 94             \item Once you're sure that everything is secure, pick up the whole
 95             assembly and place it (Winston cone first!) into the detector
 96             tank. Making sure the flange O-ring is in place, tighten the six brass
 97             bolts slowly, and in a star pattern.
 98           
 99             \item Place the hose clamp collar around the phototube base housing,
100             and slide it up along the housing such that the white phototube
101             socket is the furthest thing out. This will enable you to see the
102             pin alignment hole as you connect it to the phototube pins. Once the
103             tube is connected (take care not to touch the pins, there is a
104             strong argument that this increases dark current) slide the hose
105             clamp collar down, such that it is centered between phototube and
106 saw   1.1   base. Tighten the hose clamps as needed. (Note that the center of
107             the phototube and base are often not quite collinear. This is
108             normal, and a little bit of ``tweaking'' is necessary. Try to maintain
109             that fine line between being gentle and forcing it.)
110           
111           \end{enumerate}
112           
113           \end{document}
114           
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