\section{Machinery for Assembly and Gluing}
To dispense the glue on the tubes we developed
 a gluing machine based on the concept described in~\cite{mpi-glue}. 
The glue is always distributed on the tubes in the combs on the granite table.
The distribution of glue is illustrated in Fig.~\ref{gludist}, showing 
a cross section of a few tubes in a multi-layer.
\begin{figure}[tpbh]
\begin{center}
\setlength{\unitlength}{1cm}
\begin{picture}(14,14)
\put(0,0){\mbox{\epsfysize=10cm\epsffile{gludist.eps}}}
\end{picture}
\end{center}
\label{gludist}
\caption{\sl Glue distribution between tubes in a multilayer.}
\end{figure}

 For the central rope between neighbouring tubes held in the combs
 we use the thin glue
 Araldyte-DP2019 which nicely distributes itself around  the 65~\um waist.

 To glue  these tubes 
 to the  previously layer on the spacer  we use Araldyte-2011 
 which is more viscous and therefore the side  ropes on the tubes
 retain  their shape 
 until the two layers are pressed together.


\subsection{Sag Compensation}



 When suspended by the ears on the stacking towers the weight of the chamber
causes the cross-plates to sag by up  to 50~\um at the chamber ends and xx~\um  
in the middle.    
The tube layer to be glued is held flat in the combs
and thus without sag compensation 
a change in relative layer distance 
along the cross-plates would be frozen in.
The sags are removed by the sag compensation system
acting on the longbeams wich are attached to the 
cross-plates at the Bessel points. 
This allows to reduce the sags by typically 90%. 
To be able to reach this value 
without the risk of lifting the spacer out of the sphere holders
we added 10~kg weigths to the ears on the cross-plates. 

The system consists of 4 pneumatic tower-pairs. 
Each pair carries a
cross-bar that supports the two longbeams
at a specific position. We use a pair near the outer cross-plates and 
 a pair on each side of the middle cross plate. figure~\ref{sagcomp} 
shows two towers  on the ref-side at the middle cross-plate, 
which form individually two pairs with their corresponding towers 
at the non-ref side of the chamber.
The support of sag compension towers on the table allows them to
move freely over several mm  in the horizontal plane such 
that the spacer positionning 
is not constrained by the sag compensation.


\begin{figure}[tpbh]
\begin{center}
\setlength{\unitlength}{1cm}
\begin{picture}(14,14)
\put(-5,0){\mbox{\epsfysize=10cm\epsffile{sagcomp.eps}}}
\end{picture}
\end{center}
\label{sagcomp}
\caption{\sl Two sagcompensation towers at the middle cross-plate.}
\end{figure}

