Muon System Safety Issues Burkhard Schmidt

Safety Inspection HV-GEM electrical safety inspection: Done yesterday with ‘Bureau Veritas’ In general it went well We received 3 remarks requiring a follow-up: – Grounding of HV-cables in D3 – HV-pictograms to be put on racks in D3 and T0A – Mechanical protection of cables at the end of the cable chain  We will sort this out by Friday this week, prior to the closing of the cavern for the ‘LHC run 2009’. This allows avoiding comments in the final report.

DSS issues Reminder (from the GLIMOS): DSS is a fail safe robot system. It evaluates alarm conditions and takes action. That’s all. The absence of DSS veto shall not be interpreted as a green light for operation. Status of the Muon DSS: System has been fully tested and activated. Exceptions: – the ‘GEM Gas not ok’ alarm, which should cut the HV on the GEMs. – The ‘M1-air-cooling off’ alarm, which should cut after 30min the LV power to the M1 chambers.

Overview of the Muon DSS

ECS alerts and actions In terms of equipment safety, the following parameters are monitored by the ECS: The temperature of 160 representative Muon chambers These chambers are equipped with PT100 sensors on their Faraday cages. In case of too high temperature an alert is given, leading eventually to turn off the LV-power for the FE-electronics in the corresponding detector part. The gas-flow of the 180 MWPC and 12 GEM channels Should there be a problem with the gas flow an alert is given, which leads to turn off the HV-power on the chambers concerned.  The alerts are not yet set up in PVSS. The intention is to do this with a student early next year.

Powering the Detector General Rule: Recent incidents let us to be again more careful on powering the detector, also in terms of LV: HV and LV should only been put on the detector by sub-detector experts.

Muon Chamber HV-Powering HV settings MWPCs HV settings GEMs Voltage Configurations for the 2009/2010 run Configuration for first injection : For the first injection the system should be in the ‘OFF’ state. Procedure for circulating beam : When either beam 1 or beam 2 are circulating in the machine, we can turn on the system and move to the ‘Standby 1’ state with the trip (I max ) values as defined above. Under the assumption that the currents are well below the trip values, one can move via the ‘Standby 2’ state to the ‘Ready’ state. Procedure for first collisions at 450 GeV/c: The same procedure as outlined above. In case of trips on individual chambers, the trip (I max ) values might need some adjustment. However, the indicated trip (I max ) value of 10μA should not be exceeded for any chamber.  Background values should be measured and compared with expectations.

Documentation Safety procedures : A draft for the general operation procedures for the Muon system has been prepared. The present version can be found under: The document summarizing the HV powering of the system has been updated, including the GEM part. The current version can be found under: Comments are welcome !