1. CMS ECAL End Cap Meeting CERN 18 Oct to 22 Oct. 19991 ECAL End Cap High Voltage and Fibre Optic Monitoring Systems Progress. Progress on High Voltage and Fibre Optic Monitoring for the ECAL End Cap ECAL WEEK End Cap meeting held 18 October to 22 October at CERN Prepared by A.B.Lodge.

2. CMS ECAL End Cap Meeting CERN 18 Oct to 22 Oct. 19992 ECAL End Cap High Voltage and Fibre Optic Monitoring Systems Progress. Status Report Structure High Voltage PCB Design and Manufacture. EE Fibre Optic Monitoring System. Thermal Gasket Materials. Future Work Plan.

3. CMS ECAL End Cap Meeting CERN 18 Oct to 22 Oct. 19993 ECAL End Cap High Voltage and Fibre Optic Monitoring Systems Progress. Review of High Voltage PCBs To connect the the Super Crystal Modules with the Readout Electronics requires the design and manufacture of 3 different PCBs, these are as follows: The 5 channel High Voltage Filter Boards (5 boards per SCM). –These boards contain most of the HV Filter and De-coupling components. The High Voltage Termination Card. –This card is used to terminate and connect both the Anode and Dynode supply cables to the other 5 channel Filter cards. The low voltage Signal Termination Card. –Used to terminate the 25 signal co-axial cables from each SCM into a 50 way D-Type connector (these then connect with the 50 Channel Readout Modules).

4. CMS ECAL End Cap Meeting CERN 18 Oct to 22 Oct. 19994 ECAL End Cap High Voltage and Fibre Optic Monitoring Systems Progress. Review of High Voltage PCBs The design of the three different cards has now been completed and passed to a PCB design company for final artwork layout. Full Engineering Drawings have been produced. Quotes have been received and orders placed for the manufacture of enough cards for the construction of 2 Super Crystal Modules. Further design work is being carried out at RAL to try and optimise the design and produce the most cost effective final design solution for the EE.

5. CMS ECAL End Cap Meeting CERN 18 Oct to 22 Oct. 19995 ECAL End Cap High Voltage and Fibre Optic Monitoring Systems Progress. Review of Fibre Optic Monitoring System for the EE. Size of the MEM Module. The MEM module design proposed by SACLAY appears to be large (304*255*68) when we consider the amount of free space available to the EE after fitting the Readout Electronics, High and Low Voltage Services, Digital Readout Fibre Optics, Cooling Systems, Moderator and the rest of the Fibre Optic Monitoring System.We therefore need to understand the following: Why is the MEM module this size? The MEM module is a 12 channel unit and appears to be constructed of two identical 6 channel cards. If this is correct would it be possible to: Re-design the MEM module into 2 separate 6 channel MEM units? Or mount the MEM module remote from the EE? –If possible what would be the maximum distance?

6. CMS ECAL End Cap Meeting CERN 18 Oct to 22 Oct. 19996 ECAL End Cap High Voltage and Fibre Optic Monitoring Systems Progress. Review of Fibre Optic Monitoring System for the EE. MEM Module Cooling and Mounting. The TDR quotes a figure of 35 Watts power dissipation for each MEM module (2 per Dee); this is small when we consider that each 50 Channel Readout Module is quoted at 55 Watts (80 per Dee): Would it therefore be feasible to cool the MEM module with the same cooling system as either the Readout Electronics or the Back Plate cooling system? The MEM module appears to be designed to be mounted on the patch panels. Again due to the size of the MEM modules and the lack of free space on the End Cap patch panels, this would not be practical on the EE Is this really necessary for the End Caps?

7. CMS ECAL End Cap Meeting CERN 18 Oct to 22 Oct. 19997 ECAL End Cap High Voltage and Fibre Optic Monitoring Systems Progress. Review of Fibre Optic Monitoring System for the EE. Monitoring Fibre Layout and Routing. The Monitoring system layout and routing appear to be very difficult if not impossible if the following points are correct: All fibres from the same fibre harness (Level 1 & Level 2) have to be approximately the same length? All fibres from the same fibre harness (Level 1 & Level 2) should be exposed to the same levels of Radiation? Have Radiation Tests been been carried out on the proposed EE fibres? It would appear that each quadrant will have 2 triggers and therefore each 1/2 quadrant will be triggered separately How should these be grouped? If as shown, we may need to identify every fibre? A B

8. CMS ECAL End Cap Meeting CERN 18 Oct to 22 Oct. 19998 ECAL End Cap High Voltage and Fibre Optic Monitoring Systems Progress. Review of Fibre Optic Monitoring System for the EE. Monitoring Fibre Connections. It has been proposed by SACLAY that the EE will use a fusion splice method of joining the Level 1 fibre optics to the Super Crystal Modules: How long will it take to make a single fibre splice? Will each splice require a splice protector and at what cost? Are there mechanical splices available and at what cost? Do we know the cost for inline connectors? How much spare fibre will be required to re-make connections in the event of failure during construction? In the event of failure would all fibres of the same harness have to be remade so as to keep their lengths the same? What levels of testing will be required during the manufacture of SCM and the integration of each DEE and how will this be achieved? How will we identify individual fibres in the event of splice failure?

9. CMS ECAL End Cap Meeting CERN 18 Oct to 22 Oct. 19999 ECAL End Cap High Voltage and Fibre Optic Monitoring Systems Progress. Review of Fibre Optic Monitoring System for the EE. Monitoring Fibre Protection. During the construction of each Dee and considering the fact that we may require quite complicated routing patterns for the monitoring fibre layout, in addition, Super Crystal Modules will probably need to be mounted onto the back plate in its vertical position, starting from the top down: How will we protect the monitoring fibres during construction of the EE Dees? The idea of using polythene moderator beads in-cased in some kind of mechanical structure might be a little impractical for the End Caps.? Dual PN Diode Units. How many Monitoring Fibres are read back through each unit ( 2 or 4)? What is the power rating of each unit? Does each unit require any special cooling?

10. CMS ECAL End Cap Meeting CERN 18 Oct to 22 Oct. 199910 ECAL End Cap High Voltage and Fibre Optic Monitoring Systems Progress. Review of Fibre Optic Monitoring System for the EE. Spare Monitoring Fibre. With the Fibre Optic Monitoring System proposed, should we not provide spare fibres from the Laser switching module to the End Cap patch panels (Level 2 Fibre Harnesses)? Will we require connectors on the EE patch panels for these fibres and if so, do we have the mechanical details for them? Spare Level 1 & Level 2 Fibres. After construction of the End Cap Dees with the proposed system, the Level 1 and Level 2 fibres will be virtually inaccessible. Is it therefore accepted that these fibres will only be used during assembly to rectify any faults? Do we need try and layout the End Cap fibres to allow access after the initial construction?

11. CMS ECAL End Cap Meeting CERN 18 Oct to 22 Oct. 199911 ECAL End Cap High Voltage and Fibre Optic Monitoring Systems Progress. Review of Fibre Optic Monitoring System for the EE. Super Crystal Fibre Location. SACLAY have proposed to use a well engineered Level 1 Ferule Clip to locate the Level 1 fibre ferules with respect to the face of each crystal, this would seem to be a very good idea. Shouldn’t the End Cap also consider a similar idea? What would be the maximum distance allowable between the crystal end of the Level 1 fibres and its associated crystal face?

12. CMS ECAL End Cap Meeting CERN 18 Oct to 22 Oct. 199912 ECAL End Cap High Voltage and Fibre Optic Monitoring Systems Progress. Thermal Gasket Materials. One of the younger engineers at RAL ( Roger Barlow) has conducted some simple thermal tests on our Readout Module Prototype. These tests have shown that without proper thermal management the 50 Channel Readout Modules can reach a temperature in excess of 85°C. He has also placed samples of a selection of commercially available Thermal Gaskets into the ISIS Neutron Source and subjected them to 10^14n/cm^2. There appeared to be no visible change in the mechanical properties of these materials, but more detailed tests are needed to check for effects on their Thermal Conductivity.

13. CMS ECAL End Cap Meeting CERN 18 Oct to 22 Oct. 199913 ECAL End Cap High Voltage and Fibre Optic Monitoring Systems Progress. Future Work Plan. Continue with the designs of the HV PCB’s ( using conventional, as opposed to surface mount components to try and reduce the final cost). Use the new prototype High Voltage PCBs with this year’s Test Beam Super Crystal Module to evaluate the proposed designs. Set-up a meeting with the SACLAY design team and continue with Fibre Optic Monitoring System design proposals for the EE. Continue with a more detailed testing programme on Thermal Gasket materials.