CMS Bulletin

MUON DETECTORS: CSC

The ambitious CSC upgrade programme during Long Shutdown 1 (LS1) includes the installation of 67 new ME4/2 chambers, and replacement of the cathode electronics in ME1/1 to use flash ADCs and undo the 3:1 ganging of strips in the inner section that covers pseudorapidity 2.1–2.4. The ME1/1 project passed a follow-up (MPR) review on 14 June and is now proceeding rapidly. A programme to eliminate a tin-gold interface in the low voltage connectors in our 60 peripheral crates is well underway. Meanwhile, a combined muon system (CSC+DT+RPC) performance paper has been submitted to JINST and arXiv at the end of June.

The ME4/2 chamber factory at Prevessin’s building 904 has produced 51 of the needed 67 chambers, and continues to turn out at least the anticipated one chamber per week. Cathode (CFEB) boards are now being recuperated from ME1/1 for use on the ME4/2 chambers. Installation of associated infrastructure including cooling, low-voltage and cabling are going well. High-voltage boards are in full production with completion expected at the end of 2013.

Removal of the ME1/1 chambers is complete for the positive endcap and is proceeding on the negative endcap. The chambers are brought to the CSC surface facility at SX5 (see the Image 5 below), where they are refurbished with the new electronics and cabling, and then thoroughly tested.  The 36 associated patch panels have been removed from the noses of both endcaps, and trial installation of three new patch panels has been made.

The new digital cathode boards (DCFEBs) for ME1/1 are now in full production and more than 100 have been shipped to CERN (seven are needed on each ME1/1 chamber). Additional low-voltage power supplies have been delivered, and on-chamber cables and power distribution boards are mostly in hand. The new off-chamber boards are coming along well, with OTMB (trigger) boards in full production, while ODMB (data-acquisition) boards are nearing their production readiness review.

A comprehensive test suite has been developed that is being used for testing ME4/2 and ME1/1 chambers; this suite will also be applied to the other CSC chambers in the UXC when services are fully restored. A few ME1/1 chambers have been tested at SX5, and it is expected that two chambers will be reinstalled onto the endcap nose in August, well in advance of the reinstallation of the remainder on the positive endcap starting in October.

Image 5: The CSC facility at SX5 with ME1/1 chambers undergoing refurbishment and testing

In the CSC peripheral crates, the low-voltage “fretting” problem due to a tin-to-gold power connection is being fixed by replacement of the tin-plated backplane connectors. Tooling was created to accomplish this replacement in situ, and 12 of the 60 crates have already been repaired