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\section{Integration Procedures}
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\label{sec:Procedures}
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In this section the operations which are required to assemble a TIB shell will be listed
|
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and described in details.
|
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The various tests performed during the integration will just be mentioned among the
|
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other steps in the sequence of operations: a deeper discussion will be done
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in section \ref{sec:Tests}.
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\subsection{Shell Mechanics and Integration Bench}
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The carbon fiber supporting structure,
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on which the cooling pipes and the precision mounting ledges
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have been already glued, is the starting point for the TIB shell integration.
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To allow for a practical
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and safe handling of the structure during the integration, the shell is mounted, via an aluminum
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support frame which minimizes the mechanical stresses,
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onto an integration bench. The bench allow to rotate the shell around the horizontally placed
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cylindrical axis.
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In this way all the internal and external strings can be
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positioned in an optimal way for components mounting. The structure support frame holds also a
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number of plastic boxes which are used to temporary store the analog optohybrids fibres and their
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connectors allowing for their accessibility during the various tests.
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To identify each string during the shell integration bar code stickers are temporary glued
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on the structure. The string sticker is read and send to the integration database interface program
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before each mounting operation.\\
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A picture of a Layer 4 mechanical structure mounted on the integration bench is shown in Figure
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\ref{fig:bench}.
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\begin{figure}[!htb]
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\begin{center}
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\includegraphics[width=0.85\textwidth]{Figs/bench.pdf}
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\end{center}
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\caption{A shell carbon fiber structure mounted on the integration bench. The cooling pipes
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and ledges of inner part of the shell are visible.}
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\label{fig:bench} % Give a unique label
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\end{figure}
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\subsection{Control Ring Preparation}
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Once the shell has been mounted on the integration bench the next operation is the preparation
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of the Control Ring cables.
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As described in section \ref{fig:ctrlring} the readout clock,
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trigger and slow control signals are distributed to the
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detector modules via a token ring structured system mounted on the shells. Each TIB layer is
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served by different Control Rings whose dimensions, in terms of modules, depend on the layer position.
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For example Layer one and two, which are equipped with
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double sided modules, have control rings of 3 to 5
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strings, while Layer three and four have 13 to 15 single sided strings.\\
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The control ring boards (DOHM and AUX)
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are located on a carbon fiber plate mounted just above the modules on the
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external part of the shell (see Fig. \ref{fig:dohm}). A carbon fiber cover of the same dimensions
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of the plate close the control ring from above. An aluminum sheet has been glued
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both on the plate and the cover to protect the module from possible electrical interference. When
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monted this aluminum sheet is connected to the cooling manifold ground.
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\begin{figure}[!htb]
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\begin{center}
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\includegraphics[width=0.60\textwidth]{Figs/dohm.pdf}
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\end{center}
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\caption{A DOHM and an AUX (the smaller board) with control ring cables connected and mounted on a
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layer 3 shell.}
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\label{fig:dohm} % Give a unique label
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\end{figure}
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As can be seen in Figure \ref{fig:dohm}, due to the variable number of strings connected and their
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different positions with respect to the support
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mechanics and cooling, each control cable have a different length and shape and
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should be tailored in-situ to minimize the path satisfying all the mechanical constraints.
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To avoid damages the control cable preparation should be done when the
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modules are not yet installed on the
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structure. The control cable preparation has to be done very carefully to
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avoid mechanical interference with the services (cables, fibers and pipes)
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that share the narrow space on the shell flange
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(20mm in the z direction and 6mm in the radial one).?????????????????????????????
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When the control ring has been cabled it is dismounted from the structure
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to proceed with AOH and module installation. \\
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For layer three and four the part of the control cables
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which is not protected by the carbon fiber plate
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is shielded using a thin Aluminum foil.
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\subsection{Analog Opto Hybrid Installation}
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The small AOH board ($3\times 2.2 cm^2$)
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is simply screwed to a C-shaped ledge which is directly glued on the string cooling
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pipes. The mounting
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operation is complicated by the fact that each AOH has two (single sided modules)
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or three (double sided modules)
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two meter long pig-tail optical fibres ending with a connector. Due to mechanical constraints the
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fibers, and their connectors, should be carefully routed to the outside of the shell through a
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number of ledges, holes and pipes keeping
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them as close as possible to the carbon fiber structure surface to which they are finally fixed
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using kapton strips. The part of the pig-tail fibers which is not housed on the shell
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is temporary stored in the plastic
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boxes fixed to the shell support frame. Their connectors are inserted into
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optical plugs which
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ease the many connect-disconnect operations to be done during the tests.\\
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Since the optical fibers are quite fragile they have been
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protected when they cross the most critical points.
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For example at the
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shell flange, where the fibers should turn at 90$^\circ$ together with
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all the other services,
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they are grouped together and covered by a thin silicon rubber spiral (see Fig. \ref{fig:spiraline}).
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This procedure resulted in very reliable protection since only 4 fibres out of
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6984 was found broken at the end of TIB integration.
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A layer 2 shell with AOH mounted on is shown in Figure \ref{fig:aoh}.
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\begin{figure}[!htb]
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\begin{center}
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\includegraphics[width=0.60\textwidth]{Figs/aoh.pdf}
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\end{center}
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\caption{A layer 2 shell with AOH mounted. The optical fiber pig-tails are also visible.}
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\label{fig:aoh} % Give a unique label
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\end{figure}
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| 113 |
\begin{figure}[!htb]
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\begin{center}
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\includegraphics[width=0.60\textwidth]{Figs/spiraline2.pdf}
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\end{center}
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\caption{Group of optical fibers protected by siliconic ruber spirals at the flange exit.}
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\label{fig:spiraline} % Give a unique label
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\end{figure}
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Since the AOH are powered by the module kapton tail they cannot be easily tested before the
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modules are installed. This was a source of concerns when the integration has started: the
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operation of changing a broken AOH when the modules are already installed requires dismounting
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the entire string with the result of a considerable increase of the risk of damage to the
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mounted objects. The number of AOH that should be replaced was anyway very small at the level
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of one per shell.
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|
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|
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\subsection{Mother Cable Installation}
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The Mother Cables are inserted into the structure when the AOH have been mounted and the optical
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fibers fixed to the shell and protected. This procedure is in some cases complicated by mechanical
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constraints at the level of the shell front flange, where the mother cables are entered in the shell,
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and cooling manifolds. When the Mother Cables are inserted they
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are connected to the power cables (medusa cables) which are temporary fixed to the shell supporting
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frame. \\
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The 'medusa cables' are multi-strand cables with each conductor separatly insulated.
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This cable characteristic helps in efficiently use the very limited available space on the TIB
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| 138 |
front flange allowing to 'distribute' the cable among the other services. \\
|
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To make the control ring redundancy properly working each mother cable has to be provided with a
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CCU whose address is in a fixed order with respect to its position in the token ring. This
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position depends on how the control ring has been cabled, so this information
|
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has to be taken in mind when the Mother Cables are inserted into the structure.\\
|
| 143 |
|
| 144 |
\subsection{Module Mounting}
|
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Both single and double sided modules are mounted on the shell by hand.
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They are fixed on two precision ledges: one supports the module below the front-end
|
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hybrid and the other below the carbon fiber frame at the opposite end.
|
| 148 |
The ledges precisely define the module position and also, being in contact with the cooling pipes,
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| 149 |
act as heath sink for the front-end hybrid and sensor generated power.
|
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The shape of the ledges is different for the single sided and for the two kind
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of double-sided modules,
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| 152 |
reflecting, in this latter case, the two different orientations of the "stereo" side of the module.
|
| 153 |
Each ledge has two threaded holes (M1 screw type); one of them is concentric with a
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2 mm diameter socket
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| 155 |
acting as a slot for the module precision aluminum inset which fixes the detector
|
| 156 |
position. The socket has been precisely drilled with respect to the ledge edges which
|
| 157 |
in turns are the reference position for the precision mask used to glue them on the "shell".
|
| 158 |
All kind of modules have an aluminum pin glued on the carbon fiber frame at the hybrid end
|
| 159 |
and an aluminum U-shaped slot glued at the module opposite end. This two module insets,
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| 160 |
together with the two ledge sockets and a pin to be inserted into the U-shaped slots,
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define the module position with respect to the shell.\\
|
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Before mounting a module on the shell the structure is rotated to horizontally place
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the corresponding string. Then the string bar code sticker is read and entered into the
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integration database; the mounting location on the string is chosen and the database is
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queried for an appropriate module. The answer depends on the module type, on the inventory
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of the available module at the integration centre and on the module depletion
|
| 167 |
voltage (see par.~\ref{sec:biasandvdepl}). \\
|
| 168 |
The chosen module is then prepared: it is optically inspected under a microscope and
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the two 1-D temporary bar code stickers, one from the module frame and the
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| 170 |
other from the front-end hybrid kapton tail, are removed. Finally the module and ledges
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| 171 |
contact surfaces are inspected and cleaned to allow for an optimal heath exchange with the
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| 172 |
cooling circuit. These preparation operations are often difficoult and, especially for
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| 173 |
the double sided modules, very delicate; for these reasons they amount for
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| 174 |
a considarable fraction of the time spent to mount a module.\\
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When a module is ready the operator mounts it on the structure by hand.
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First the module is leaned onto the ledges keeping the microbonds away from the other
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ledges or cooling pipes.
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| 178 |
%This operation, because of the presence of microbonds on the back
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| 179 |
%side and the more stringent mechanical tollerances,
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%is quite difficult for double sided modules; for this reason a simple mechanical piece has
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%been realized in order to guide the operators hand avoiding possible module damages.
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When the module lies on the ledges the operator sligthly moves it to allow for the insertion
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pin (Fig. \ref{fig:insets} c) glued on the frame on the front-end hybrid side, to
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enters correctly the ledge precision socket.
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| 185 |
At this point the module has only the possibility to rotate around the pin axis.
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This last degree of freedom is then fixed inserting a T-shaped aluminum
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| 187 |
pin inside the frame U-shaped slot (Fig. \ref{fig:insets} b) and on the ledge precision socket.
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The U-shaped slot is used instead of a cylindrical hole, to allow for a module position
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| 189 |
matching also in presence of the unavoidable gluing errors on the precision insets and on the
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ledge slot positions.
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| 191 |
The module is finally fixed to the ledges by four M1 type amagnetic steel screws.
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| 192 |
It should be noted again that the module position is not
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determined by the screws but only by the precision sockets and the insets and slots positions. \\
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| 194 |
|
| 195 |
\begin{figure}[tbh]
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| 196 |
\centering
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| 197 |
\includegraphics[width=.7\textwidth]{Figs/collage.pdf}
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| 198 |
\caption{TIB single-sided module insets:
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| 199 |
\textbf{a:} The u-shaped slot glued on the carbon fiber module frame;
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\textbf{b:} the T-pin inserted in the slot (seen from below);
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\textbf{c:} front-end hybrid side precision insertion pin (seen from below).}
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\label{fig:insets}
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\end{figure}
|
| 204 |
|
| 205 |
The clearance between the module most delicate parts (bondings)
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| 206 |
and the other structure present when the operation is performed (cooling pipes and ledges of the
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adjacent strings and modules already mounted) are, in case of single-sided modules,
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sufficiently large for a safe operation.
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| 209 |
For the double-sided modules the cleareances are much reduced being
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| 210 |
of the order or less than a millimeter.
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| 211 |
In this case, to guide the module during its insertion, a simple mechanical
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| 212 |
tool has been used. This tool simply
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| 213 |
adds temporary constraints (mechanical stops) to the structure avoiding possible accidental contacts
|
| 214 |
between the module bondings and the rest of the shell.\\
|
| 215 |
When a module has been mounted on the structure its basic functionality is tested:
|
| 216 |
only low voltages are
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| 217 |
switched on and the I$^2$C communications with the various devices present on the hybrid, mother cable
|
| 218 |
and AOH are verified. Furthermore the module identity is checked and compared with the one stored on
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| 219 |
the integration database using the DCU hardware ID as a fingerprint of each produced module.
|
| 220 |
When a string of three modules has been mounted the I$^2$C communication are again verified and
|
| 221 |
a noise run, at 400V bias, is taken. For the tests complete description see section \ref{sec:Tests}.
|
| 222 |
|
| 223 |
\subsection{Control Ring Installation}
|
| 224 |
The TIB control electronics, which distributes clock, trigger and I$^2$C signals to the modules,
|
| 225 |
is located on a carbon fiber support mounted on the shell external surface
|
| 226 |
just above the modules.
|
| 227 |
A thin aluminum foil has been glued on the support and electrically grounded
|
| 228 |
to reduce possible interference between the logical control signals and
|
| 229 |
the module analog electronics. The DOHM and, when present, the AUX
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| 230 |
are mounted on the support (Fig. \ref{fig:dohml4}),
|
| 231 |
the preformed cables are connected to the Mother Cables.
|
| 232 |
The DOHM power cable is similar to the mother cable 'medusas' and it is directly plugger into
|
| 233 |
the DOHM. \\
|
| 234 |
|
| 235 |
\begin{figure}[tbh]
|
| 236 |
\centering
|
| 237 |
\includegraphics[width=.7\textwidth]{Figs/dohm.pdf}
|
| 238 |
\caption{A Layer 4 control ring circuitry. The DOHM and AUX boards are visible, the control ring
|
| 239 |
cables are connected to the mother cable heads (not visible).}
|
| 240 |
\label{fig:dohml4}
|
| 241 |
\end{figure}
|
| 242 |
|
| 243 |
The $4 \times 2$ optical fibers, which connect the two DOH to the FEC, should be very well protected
|
| 244 |
to assure a proper functionality of the control ring. In fact using the redundancy architecture
|
| 245 |
implemented for this circuitry it is possible to run the ring also in presence of a damaged
|
| 246 |
DOH, but the price to pay for a double failure in the DOH connections is of the order of 1-2\% of the
|
| 247 |
entire TIB.\\
|
| 248 |
When the control ring is completed it is closed with another
|
| 249 |
aluminun shielded carbon fiber cover (Fig. \ref{fig:dohml1})
|
| 250 |
and finally tested (see section \ref{sec:Tests}).\\
|
| 251 |
|
| 252 |
\begin{figure}[tbh]
|
| 253 |
\centering
|
| 254 |
\includegraphics[width=.7\textwidth]{Figs/L1DOHM.pdf}
|
| 255 |
\caption{A Layer 1 completed with its control rings. The DOHM and cable area is covered with
|
| 256 |
aa aluminum shielded carbon fiber plate.}
|
| 257 |
\label{fig:dohml1}
|
| 258 |
\end{figure}
|
| 259 |
|
| 260 |
Two PT1000 temperature probes per control ring are glued on the cooling manifolds.
|
| 261 |
The probe wires are
|
| 262 |
routed through the DOHM via the Control Ring power cable up to the power supply racks where an
|
| 263 |
interlock boards is located.
|
| 264 |
The PT1000 resistance measurement is done using a 4-wire connection to avoid the
|
| 265 |
contribution coming from the 40 meters long power cable. One humidometer is located on the
|
| 266 |
DOHM board and it is also read out through dedicated wires on the Control ring power cable.
|
| 267 |
|
| 268 |
|
| 269 |
\subsection{Integration Database}
|
| 270 |
|
| 271 |
Each active element, cables included,
|
| 272 |
of the CMS experiment is identified by a bi-dimensional, radiation resistant,
|
| 273 |
bar code which is glued on the component itself redundantly coding a 14-digit number.
|
| 274 |
For the tracker the registered components are:
|
| 275 |
detector modules, AOHs, DOHMs, DOHs, CCUs, Mother Cables,
|
| 276 |
optical fibres and ribbons, power and control cables.
|
| 277 |
Using this code the object characteristics and the results of the tests previously performed
|
| 278 |
during the production phase, can be retrievied from
|
| 279 |
the Tracker construction database~\cite{ref:database}.
|
| 280 |
Of equal, or even more, importance are the component
|
| 281 |
mounting locations and the connections between them.
|
| 282 |
This information is stored on the integration database at integration time.
|
| 283 |
Moreover the integration database acts also as an inventory to locate the components among
|
| 284 |
the various integration centers managing the shipping procedures.
|
| 285 |
It also contains a subset of the test data of all the
|
| 286 |
devices and their functional status (good, broken, mounted, dismounted, etc...).\\
|
| 287 |
Along with module tests results also an important number is stored for each module:
|
| 288 |
the hardware identifier of the DCU chip
|
| 289 |
embedded with the module (or DcuHardId). This code can be retrieved during data acquisition,
|
| 290 |
allowing for an unambiguous identification of a module.\\
|
| 291 |
A TIB/TID specific key was defined to store the location of mounted devices (named Geographical
|
| 292 |
Identifier, or GeoId): it is a string
|
| 293 |
composed of numerical fields separated by dots, as described in Table~\ref{tab:geoids}.
|
| 294 |
Bar code stickers with the GeoId are glued on the mechanical structure
|
| 295 |
before the integration starts (Fig. \ref{fig:stickers}).
|
| 296 |
|
| 297 |
\begin{figure}[t]
|
| 298 |
\centering
|
| 299 |
\includegraphics[width=.6\textwidth]{Figs/stickers.pdf}
|
| 300 |
\caption{An empty shell with the bar code stickers identifying the strings.}
|
| 301 |
\label{fig:stickers}
|
| 302 |
\end{figure}
|
| 303 |
|
| 304 |
The first 7 numbers in a GeoId identify the string to which a device belongs, while the last
|
| 305 |
part of this code represents the physical location where the device is placed.
|
| 306 |
|
| 307 |
\begin{table}[h!]
|
| 308 |
\begin{center}
|
| 309 |
\begin{tabular}{l|ccc}
|
| 310 |
& 1 & 2 & free value \\
|
| 311 |
\hline
|
| 312 |
a & TIB & TID & \\
|
| 313 |
b & Forward ($z>0$) & Backward ($z<0$) & \\
|
| 314 |
c & Up ($y>0$) & Down ($y<0$) & \\
|
| 315 |
d & & & Layer \# \\
|
| 316 |
e & Inner & Outer & \\
|
| 317 |
f & & & Manifold \# \\
|
| 318 |
g & & & String \# \\
|
| 319 |
\end{tabular}
|
| 320 |
\caption[smallcaption]
|
| 321 |
{A generic $a.b.c.d.e.f.g$ GeoId identifies a string and must be interpreted according
|
| 322 |
to this table. For example of GeoId 1.1.2.4.1.3.2 identifies the second string, of the
|
| 323 |
third manifold placed in the inner surface of the Layer 4 Down Forward TIB shell.}
|
| 324 |
\label{tab:geoids}
|
| 325 |
\end{center}
|
| 326 |
\end{table}
|
| 327 |
|
| 328 |
%The first number identifies TIB (1) against TID (2),
|
| 329 |
%the second number marks the forward part (1) vs. the backward (2). Hence TIB and TID codes become
|
| 330 |
%different. For TIB the third number identifies the upper/lower shell (1,2) and the fourth is
|
| 331 |
%the layer index (1-4).
|
| 332 |
%The following numbers represent if a device is placed on the inner or outer surface of a shell,
|
| 333 |
%the cooling manifold a device belongs to and the string index insidethe same manifold.
|
