TECHNICAL COORDINATION

 

In the reporting period, CMS has collected about 10 fb–1 of pp collision data. Considering the prolonged duration of the current running period, with no opportunity for thorough maintenance since 2009, the reliability of the infrastructure and common systems was satisfactory. . Once again, CMS was fortunate that some failures coincided with LHC downtime, avoiding major data losses.

After repeated difficulties over the summer with reconnection of the cold box following an unexpected stop, the procedure was revised. For reliability, and to reduce the risk of a fast discharge, the reconnection is now done at a reduced field of 2 T, resulting in a mechanical on-off-on cycle. It is also time consuming, with two times two hours for the ramp-down/up and several hours for refilling the He dewar before restoring the field to 3.8 T. In response to this, a mode of operation has been successfully tested that allows doubling the refill rate of the dewar. Reconnection at a somewhat higher field is also under study, with the aim of having the magnet operational again within about five hours of a cold-box stop.

As the cold box was disconnected twice since the last CMS week due to insufficiently planned or misguided interventions, very strict rules have now been imposed on those interventions, including a formal ban on any interventions on the electrical system of the magnet during beam operation.

Other infrastructure incidents have mostly affected the cooling system and involved faulty sensors. The C6F14 cooling was stopped three times, the first due to a faulty level-indicator in the main reservoir falsely indicating a major leak, the second due to a failing power-LED in the control system found to be in series with the cooling PLC, and the third due to a low liquid-level alarm caused by an incorrect threshold setting. A major overhaul and review of the system and its operational procedures is planned during LS1 to further improve its fault tolerance and redundancy.

YETS

LHC proton-proton beam operation will end on 17 December at 06:00. The following 24 hours will be used for calibration at full field. In the morning of 18 December the magnet will be ramped down, followed by some hours’ calibration at 0 T. In parallel, the RP sweep in the UXC will take place. On 19 December the detector will be brought into a safe state for the year-end-closure of CERN, including a stoppage of all flammable gases. At 15:00 the shift operation will be terminated. From then on, two daily safety tours will take place. In addition the installation of CASTOR will be prepared during 19–21 December.

On 3 January, well before the official re-opening of CERN on 7 January, the cool-down of the magnet will start, to ensure readiness for a cosmic run on 12–14 January, prior to the first beam in the LHC. Also on 3 January, CASTOR will be installed at the negative end with the beam pipe under vacuum. As the ZDC crane is unfortunately still not mounted on the TANs, the ZDC will be reinstalled inside the TAN with conventional means, provided the radiation level permits. The installation is foreseen for 7 January to allow for the longest possible cooling time.

Shift operation is planned to start on 5 January. For the safety tours between 20 December and 3 January as well as the shifts between 3 January and 7 January, volunteers are still highly welcome – please contact Technical Coordination.

LS1

The third TC workshop in preparation for LS1 took place during 26–27 November at Chateau Bossey, with an overflow session on 5 December at CERN. Due to intensive work on the planning of sub-projects and on the overall schedule, a robust master schedule –– with branching points, milestones and a small (three-week) contingency –– will be available shortly. Major rework of the schedule in late spring/early summer 2013, with an early exposure of YB0, now gives more time for successful humidity sealing and cooling system insulation to be installed in the vactank area, allowing the Tracker to be operated cold, one of the most important objectives of LS1.

The list of main objectives for LS1 was reviewed and left unchanged:

·       Prepare CMS to be able run the Tracker cooling fluid at –25 ºC.

·       Install a 45mm o/d beam pipe and make provisions for an installation of a new pixel detector before LS2.

·       Complete the DAQ upgrade and make provisions for a Trigger upgrade before LS2.

·       Eliminate of all CMS specific risks to detector integrity, data quality and data taking efficiency, requiring the substantial overhaul and consolidation of the magnet, the electrical system, the cooling systems, the gas systems and the dry gas distribution.

·       Complete all upgrade and consolidation work on the muon systems that requires a long shutdown, such as YE4, ME1/1, DTSC.

·       Complete the first stage of the consolidation and upgrade of the HCAL photon transducers, the HO and HF, and the exchange of the CCMs.

·       Complete the installation of the 4th endcap muon layer (ME4/2, RE4)

·       Correct all known faults, affecting the physics performance of CMS. (Each subsystem has a prioritised list of interventions.)

The preparation of SX5 as a centre for detector maintenance and repair is well advanced. The areas for the muon detectors will be operational by the end of the year. The HVAC system for the pixel lab is being installed. The lab will be ready to receive the pixel detector when it is extracted. The various storage areas including those for activated parts are under preparation and will be ready at the beginning of LS1.

Technical oversight of LS1projects involved a large number of reviews for a great variety of projects. They showed that the projects are in a well-advanced state and are expected to be ready as required by the master schedule.

A few more reviews are still outstanding:

·       An EDR for RPC4, scheduled for early 2013, when we will have some experience with the gap production currently starting at Kodel.

·       A MPR for ME4/2 and ME1/1, which are closely interlinked. It will be held early in 2013 when hopefully all questions on the new on-board electronics and the increased LV power consumption can be answered and the new ODMB with copper control circuitry will be available.

·       A Pixel-Beam Pipe Integration Review to revisit all aspects of the installation of the old and new pixel detectors around the new beam pipe, particularly the tests and measurements to be done in LS1. The review will be held in spring 2013.

In general the preparations for LS1 are proceeding well, consistent with a robust and credible master plan. If resources are made available as planned and there are no major surprises in the next 2 months, CMS will start LS1 well prepared.


by A. Ball and W. Zeuner