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Totem T1 ESR 17 Sep 10

Totem T1 ESR 17 Sep 10. Observations from Electrical Inspection of T1. S. Lusin. Installation Requirements. Installation of T1 inside the structure of CMS must be consistent with maintaining: Safety Personnel and equipment safety must be assured Performance of CMS

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Totem T1 ESR 17 Sep 10

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  1. Totem T1 ESR 17 Sep 10 • Observations from Electrical Inspection of T1 S. Lusin

  2. Installation Requirements • Installation of T1 inside the structure of CMS must be consistent with maintaining: • Safety • Personnel and equipment safety must be assured • Performance of CMS • Introduction of the T1 detector must not compromise the physics performance of CMS • Operational readiness of CMS • Introduction of the T1 detector must not compromise the CMS or LHC schedule • Operation of the T1 detector must not compromise the operation of CMS

  3. Electrical Issues … • Power connections to the cathode and anode front-end boards are made through flat cables intended for signal transmission • These are fine-pitch cables • Adequacy of cross-sectional area devoted to the power conductors needs to be demonstrated • Have asked S. Minutoli to confirm. • Even with adequate copper, quality of the crimp connections between the cable and connector contacts is variable. • Experiences with this use of flat cable at Fermilab have not been positive • M. Johnson has pointed out that reversal of polarity is a concern • Potential for polarity reversal exists in the form multiple screw-terminal connections during installation • Electrical protection of these cables must be provided • Otherwise I would consider this to be a safety risk

  4. Electrical Issues II … • These same cables are used to read out the cathode front-end boards • Cables are 25-40cm long and are completely unshielded • Possibility for noise pickup or emission • CMS CSCs had appreciable noise pickup in the installed environment even though they used shielded cables, only 10-20cm long, with half their length being inside an aluminum enclosure. • In the end, the CMS CSC group had to modify the aluminum covers over the cathode front-end boards in order to provide additional shielding • TOTEM electrical designers should consider providing shielding over the ROC-CFEC connections • There will be no possibility to add it later • Lack of shielding presents a potential operational readiness risk

  5. Electrical Issues III … • The lack of line protection on the LV fanouts is a serious concern • Each MARATON channel, capable of delivering up to 50A, is connected via two 16 mm^2 conductors to a patch panel where it is fanned out via two 1.5 mm^2 conductors per ROC board • At the ROC boards there is then a further level of fanout to the CFEC and AFEC boards via the flat cables mentioned earlier • Apparently, there is no line protection to prevent the full allowable channel current from flowing through a single low-area conductor • If this is true, I would consider it a safety risk • Similar to issue #1 but more general

  6. Electrical Issues IV … • With the exception of the unshielded flat cables in item #2, the LV and HV distribution and remote sense cables are all shielded • Shields are terminated not by bringing out the braid, but by ~ 0.5-1.0 mm^2 wire pigtails, approximately 10cm long • These are high inductance connections that may defeat the purpose of using shielded cable • These connections are left dangling • The documentation shows these connections as jumper options • There is no default grounding configuration; all options remain open • When T1 is installed on the HF platform there will be no time to optimize ground jumper configurations • There should be a baseline configuration ready-wired on T1 and reflected in the documentation • Otherwise I would consider it an operational readiness risk as well as a detector performance risk

  7. Electrical Issues V … • Ground connections between the T1 detector elements, the T1 support frame, and the CMS steel are undefined • Any useful grounding connections will involve a fair amount of mechanical design and fabrication • That work should be done now, as it will not be possible to do it during installation • I would consider any attempt to design and fabricate the mechanical grounding scheme in situ to be both an operational readiness risk as well as a detector performance risk

  8. Operational Readiness… • CMS must come back online following the end-of-year technical stop fully ready to take data • During CMS running, Totem T1 must be able to operate without resulting in any loss of data-taking to CMS • Expected performance parameters of T1 should be described to CMS technical team prior to start of data-taking

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