The April Global Run (AGR) took place last week, Monday-Friday 7-11 April. This being the first run since November 2013, the last run using the Run-1 DAQ, and the last run just before an extended cooling maintenance at P5, we embarked on the week with an ambitious plan of work.

The run started in fine form already on Sunday evening with a power cut which affected the cooling water for many subsystems, turning Monday to a recovery day for them. Other hurdles that we had to deal with included the need to keep night shifts for all nights beginning Tuesday to keep the runs going, the elevator breaking down (twice), the gas system killing the HV on the RPC (5 times) and the CSC (once), and relatively frequent breakdowns of communication between shift crews and the experts. At times it did feel like a real test!

In spite of this list (it’s more fun to talk about the problems!), the run was a roaring success. A clock frequency scan proved that the QPLLs of the CMS subsystems can operate well beyond the range required for LHC runs with heavy ions (a more demanding requirement than protons). The communication and synchronization between a small set of production oSLBs and oRMs (new trigger optical connections from ECAL→RCT) was successfully established in situ. Strips successfully collected cosmic ray muons in a global run for the first time at the Run-2 operating temperature of –15°C. HCAL commissioned the new HO Silicon Photomultiplier tubes, using cosmic ray triggers both self-generated as well as by DT. The DTs successfully established the timing of their new sector collector boards and proved they were synchronized with RPC. The RPCs ran in a global run for the first time with the newly installed RE4 chambers. Last but not least, CSC also successfully ran with both endcaps with the newly installed ME4/2 chambers.

For those interested in more details, a twiki documenting the AGR can be found at https://twiki.cern.ch/twiki/bin/view/CMS/AprilGlobalRun2014, the Run Meeting with the “shakedown” of the operations aspect can be found at https://indico.cern.ch/event/313742/, a summary of the operations was presented at the Wednesday General Meeting (https://indico.cern.ch/event/298334/), and a “Data Analysis Jamboree” is scheduled for 29 April (no indico agenda yet…).

By Greg Rakness