\chapter{CsI Scintillators}
\section{CsI Scintillator Mount}

N.B. \em Most components have an identification number stamped on them.
\newline
\newline
\rm Take the CsI scintillator mount (AO-32/8045). See Figure 3.1. The top of the mount has the number AO-32/8045 engraved upon it. Screw on four legs, see Figure 3.2.

\begin{figure}[ht]
\vspace{13cm}
\special{psfile = /home/oed/Modprotocol2/mount.ps
 hscale=80 vscale=80 hoffset=-20 voffset =-140}
\caption{CsI scintillator mount (A0-32/8045).}
\end{figure}

The screw holes for the legs can be located on the side of the mount (two screws per leg). The legs are identified by A2-32/8052. The feet of the leg should point outwards (see Figure 3.2). Eight screws (M2 6mm) will be needed for the attachment, in this case vacuum relieved screws are necessary as the screws do not go all the way through the CsI scintillator mount.

\begin{figure}[ht]
\vspace{8cm}
\special{psfile = /home/oed/Modprotocol2/leg.ps
 hscale=90 vscale=90 hoffset=-40 voffset =-255}
\caption{CsI scintillator mount support leg.}
\end{figure}

Four 60mm threaded rods are used to separate the different grids and PSD's used in the module. These rods screw into the four holes, that reside at the four corners of the central mount point (see Figure 3.1). Screw them through such that 5mm of rod shows through the back of the mount. Lock these rods into place using a small nut screwed tightly onto the 5mm of thread showing.

\section{CsI Scintillators}

Eight CsI scintillators will be required for the centre module and nine for the outer modules. Ensure that each scintillator has an insulator ring attached. At either side of the insulator ring are two spring mounts. Attach the round end of the spring to these (see Figure 3.3). The hooked end of the spring is used to attach the CsI scintillator to the scintillator mount.
At this point particular attention must be payed to the orientation of the CsI scintillators within the mount. The orientation of the scintillator is defined by the number on the back of the photo-diode PCB and pin 1 of the ribbon cable socket which sits on the PCB. See Figure 3.4.

\begin{figure}[ht]
\vspace{8cm}
\special{psfile = /home/oed/Modprotocol2/CsI1.ps
 hscale=90 vscale=90 hoffset=-45 voffset =-260}
\caption{CsI scintillator (side view).}
\end{figure}



Hence prior to fitting the insulator ring, make sure that the ring is fitted such that the correct orientation of scintillators is met according to Figure 3.5.
\newline

\begin{figure}[ht]
\vspace{8cm}
\special{psfile = /home/oed/Modprotocol2/csi.ps
 hscale=90 vscale=90 hoffset=-55 voffset =-240}
\caption{CsI scintillator (back view).}
\end{figure}
N.B. \em The spring hooks attach into the holes provided on the CsI scintillator   mount (see Figure 3.1) such that the front mylar face of the scintillator sits level with the front face of the mount. In this way when the mount is stood on its feet the spring takes the load and the mylar faces of the scintillators point upwards. If a centre module is being constructed, then the central CsI scintillator will be missing.
\newline
\rm

\begin{figure}[ht]
\vspace{10cm}
\special{psfile = /home/oed/Modprotocol2/csiarr.ps
 hscale=120 vscale=120 hoffset=-155 voffset =-340}
\caption{CsI scintillator configuration.}
\end{figure}

At this stage the CsI scintillator clamp (AO-32/8046) can be screwed in place. This requires four screws at each corner of the clamp, screwed into the CsI scintillator mount (see Figure 3.1). In this case the screws do not require vacuum relieving.

The CsI scintillator ribbon cable can now be attached as shown in Figure 3.5.
By flipping the top of the socket attached to the ribbon cable, it is possible to expose the pins which attach to the socket on the scintillator photo-diode PCB. Check the continuity between the pins of the last socket on the ribbon cable and the sixteen pin female connector at the other end of the ribbon cable. In this way we can make sure that there are no discontinuities in the signal lines of the ribbon cable.

Figure 3.4 shows the labeling used for the scintillator signals. It is important to understand that pin 14 of the socket on the back of the photo-diode PCB, corresponds to line 1 of the ribbon cable (i.e. the red line).

When placing the ribbon cable into the socket on the back of the scintillators, care must be taken not to bend any of the pins.
At this point check that each scintillator has a pre-amplifier board attached to the eight pin connector on the PCB.

The scintillator mount can now be screwed onto the baseplate, ensuring that the sixteen pin female connector at the end of the ribbon cable can be fitted into the glass feedthrough next to the  `gas in' SwageloK fitting.
Eight vacuum relieved screws (M2.5 8mm) are required at this point. Screw these through the feet of the mount into the eight holes on the base plate (see Figure 2.1)

Figure 3.5 also shows the way in which we number the telescopes. The telescope which is next to the sixteen pin female connector (attached to the ribbon cable) is defined as telescope one.

