LHC status Friday 11 th September 2015 Coordination: Mike Lamont, Jorg Wenninger

Thursday 10 th September 07:20 Operator dump to ramp down before loss of Cryo Maintain at point 4 (SB 745b) – Surface cold box struggling to supply He to QUIC True everywhere – point 4 the worst Level drops in the QUIC Defense: Increase 60 A leads regulation temperature from 17 to 20 K everywhere (still margin to go to 23 K). Also possibility to decrease temperature on inlet to beam screens from 13 to 9 K (as already done in IP2) – Issues in point 6 - running on 1 CB and 1 QUIC for 2 sectors – should be enough in principle – BS program kicks in after 400 b – leave enough time to stabilize before starting ramp (~15 minutes)

Thursday 10 th September So while cryogenics is recovering, attention turned to QPS – A remote software intervention to recover the QPS_OK conditions with a recent update to the macro tool was unsuccessful and eventually a QPS controller in each of 5 sectors were power cycled, provoking a heater firing – 11 heaters fired in total. 9 systems generated correctly their PM files and have a good discharge. Two heaters have incomplete PM files, however the first part of the discharge is OK.

Thursday 10 th September 12:45 Trip of sector 3-4 – RQF.A34 provoked a Global Abort of ARC 34 – Energy extraction “trip” 13:35 Start precycle 15:20 Injection for instability MD on FT – phase 1: 50 ns 18:15 OP dump 19:15 Lose RD2.L1 during turn around

Friday 11 th September 02:45 Access finished – RD2.L1: replaced power supply but they could not switch it in ON. – Problem with a fuse, TI had to send someone. – Then the fast abort could not be cleared because of FW DIODE fault was still sending the fast abort unsafe 03:15 Lost RQTF.A12B1 during pre-cycle – Resets by QPS piquet ineffective – contacted MP3 piquet (Ivan). – Trigger: power converters with Vin DC under voltage 05:00 Access for EPC point 2 to change the power module

Friday 11 th September 07:50 RQTF/D.A12B1 and RQS.L2B1 ok after EPC intervention plus test Give up and give general access – CMS, ALICE – Cryo: worldFIP RE78 – CV – UW25 – ED station – Cryo: – temp sensor DFBs IP4 & IP55 – BI – FBCT – add attenuators – BGV – point 4 – Schottky – bypass RF filter – BBQ – check of dev system

Instability Threshold for 2x36b trains with 50ns spacing 2 INDIVS + 2 trains of 36b with 50ns spacing separated by 250ns. Emittances approximately 3um (tend to start lower and end higher). At flat top, set Q’ to 7 both beams and planes. Reduce octupole current until instability forms. First 4 bunches in B2V becomes unstable at 94A with a clear mode =|2| from the head tail monitor. We then see activity in B2H soon after. B2 octupoles to 550A. Continue with B1, first few bunches in B1H become unstable at 37A, followed by half of first batch in H, including INDIV’s. L.R. Carver, B. Salvant, T. Levens

Sync phase at end of fill. B2 Left: No synchronous phase shift along train. Below: BSRT from just prior to first instability. Emittance profiles along the bunch are the same as when first reaches flat top. No signs of e-cloud. Instability thresholds for 50ns train were consistent with previous single bunch measurements and pure impedance predictions. Need to ramp with 25ns bunch spacing to compare when e-cloud is present. B1

RD2.L1

Today Access until around midday Recover/precycle 4 – 5 hours beta* - tbc Physics with 745 bunches