LOS LÍPIDOS

When the the final layer is inserted the skin and electronics could be attached to the module along with the necessary service structures. MPPCs were clipped onto the end of each fibre in a specially designed shrouding as shown in Figure3.9. The coaxial cable, used to connect the MPPC to the front end board, was attached to the PCB. The two pins protruded out of

52 CHAPTER 3. CONSTRUCTION OF THE ND280 BARREL ECAL the PCB on either side of the co-axial connection. It was vital to make sure that the end of the co-axial cable did not touch these pins. Any contact between the cable and pins would create a short circuit and prevent that channel from being read out. A screw was placed through the hole in the shroud and screwed into the bulkhead to hold the MPPC assembly in place. Each MPPC and cable was pre-labelled with an assigned channel number and TFB. This is used downstream to produce a channel mapping for the software geometry. Each co-axial cable was then grouped together based on which channel on which TFB they would be connected to.

Figure 3.9: Left) The sensor-fibre connector shrouding. The setting tool clipped onto the ferrule holding the MPPC in place at the end of the fibre. Right) A picture of the MPPCs attached to the end of the fibres with the cables grouped by TripT.

During operation the TFBs require cooling to prevent overheating and damage to the boards. As a result the TFBs are affixed to stainless steel cooling plates using a thermal cooling plate, this allows the heat generated during operation to be dissipated much more quickly. The cooling plates were loosely fixed in place on the outer edge of the bulkheads and the co-axial MPPC cables were passed through the appropriate gaps in the cooling plates. At this point the cooling plate could only be loosely affixed at this point so that the MPPCs could still be accessed and, if necessary, replaced.

The label on each cable was used to clip the co-axial cable to the appropriate channel on the appropriate TFB. Each MPPC and TFB was tested to check for damage. Any damage was repaired or replaced. This ranged from faulty sensors, cables or boards to the simple short

circuit between the cable and pins. The length of the co-axial cables prevented complete removal of the cooling plates at this point without having to re-connect every MPPC (a lengthy process). This meant that any replacement or repair work had to be performed in the confined space that could be created behind the cooling plates without disconnecting or damaging the cables that were already attached.

The penultimate task was to add services to the module. First, five copper bus-bars were installed around the the centre of each module face hosting TFBs. These bus bars would be used to power the TFBs providing the four low voltage lines and one ground line. Metallic cooling pipes were also passed around the top and bottom of the modules. The cooling pipes were thermally coupled to the TFB cooling plates at several points on each face of the module. Finally, RJ45 patch cables were plugged into each TFB for readout to the back-end boards. These RJ45 cables were then passed through a patch panel to be inserted in the modules outer cover plate.

With the services and readout cables attached the final cover plates of the module were fixed in place. The module face without electronics readout was covered with a metal sheet. The other three sides were covered with metal plates, one of which contained the patch panel, the connection for the bus-bars, the intake for the dry air service and the inlets and outlets for the cooling water. The opposite face house two black vents as outlets for the dry air.

The second half of the module’s LI system was affixed to the top skin of the module in the same manner it was affixed to the module base. Once the LI was installed correctly the module’s top was bolted on top of the bulkhead. The module top was of the same construction as the module base for the side modules, i.e. a carbon fibre skin surrounded by an aluminium edging. For the top and bottom modules the top face was a thicker metallic construction with grooves so that the module could be fixed to the inner surface of the ND280 magnet on I-beam rails. An example of such a top face can be seen in Figure3.10. At this point the module is completed and ready to be shipped to the experimental site.

54 CHAPTER 3. CONSTRUCTION OF THE ND280 BARREL ECAL

Figure 3.10: A completed barrel bottom ECal module. The grooves on top of the module are for sliding the module onto the metal beam that will eventually attach it to the ND280 magnet.