
\subsection{Control of the tube position}

   The position of the tubes placed  in the jigs 
 is checked prior to glueing  by the readings of the
 End-Plug Laser systems at HV and RO ends ( see 5.3 ).
 A typical example of the residuals from a straight line
 fit throught the data is shown in fig [gltyp.ps].
  Deviations of more than 20~\mum 
 require an inspection of the associated tube(s).
 Repositionning of the tube usually solves the problem.
 Only in a few cases tubes had to be replaced because
 the plug was inproperly crimped into the tube.
 So far no significant deviations caused by plug
 diameter variations were found.  




   In Fig~\ref{guitomo}a~and~b we plot the average of the residuals from the straight
 line fits for all 6 layers of the first 4 chambers as a function 
 of the position in the comb at each side of the
 assembly table.

 The error bars represent the rms of the
 24 deviations found at that position, typically 5~\mum.
 Systematic  deviations of order 8~\mum can also be recognised.
  These are attributed to the fact that the jigs are 
 assembled out of 4 solid pieces  which were precisely machined
 and then glued together. 
 The fixation of the jigs to the granite table and 
 to the assembly stacking towers on the reference side ( position zero
 in the plots ) also leads to small distortions. However these systematic
 deviations are well within the required precision.


\begin{figure}[b]
\begin{center}
\setlength{\unitlength}{1cm}
\begin{picture}(14,10)
\put(0,0){\mbox{\epsfysize=12cm\epsffile{guitomo.eps}}}
\end{picture}
\end{center}
\caption{\sl  a) b) Deviation of wires obtained from X-ray tomograph.  c) d) Deviations obtained from the End-Plug Laser system.}
\label{guitomo}
\end{figure}























