Run Coordination Report 4th RPC General Meeting (CMS week) Luigi BENUSSI, Hassan SHAHZAD, Nicolas ZAGANIDIS

RPC Operation overview LHC achievements & plans Detector behavior Online P correction Operation performances Shifts Conclusions 2

LHC achievements Since the 24 th of June new scheme : :50ns_1236b+1small_1180_37_1152_144bpi50ns_1236b+1small_1180_37_1152_144bpi

LHC achievements 23:55 April 21st - world record for luminosity at a hadron collider with 4.67e32 cm -2 s -1.

LHC plans

Stay at 50 ns bunch spacing this year. Only next year go to 25 ns :  Now : Physics with 1236 bunches: 50/pb-1 fill is the goal.  Physics with 1394 bunches  Decrease the emittances, populate the bunches expected pileup rate : x ~3

CMS reached the fb -1

RPC Hardware Status  Annual HV module recalibration – all CAEN A3512N HV module offsets recalibrated (125 Hvboards)  Number of RPCs operated in Single Gap mode is unchanged in 2011 for the endcap and increased from 6 to 10 for the Barrel: Now : 10 in the Barrel and 19 in the Endcap  Number of disconnected chambers is unchanged in 2011 : 3 in Barrel & 3 in Endcap 8 ….More details in the TC presentation…

 Number of active electronic channels is stable ~ 98.5% 9

Barrel z dependence: 2010 (left) vs (right, CMS PRELIMINARY) Background rate vs Instantaneous Luminosity For different Wheels (different position along z) CMS preliminary 2011  Chamber behavior versus beam Luminosity

 The Current follows the beam luminosity No any abnormal behavior of the dark current has been observed Beginning of the stable beams End of stable beams RPCs ON cosmics RPCs in STANDBY Peak Luminosity: 1.274x10*33 cm-2s x10*33 cm-2s-1  imon= 0.07 uA

BARREL Endcap Dark current follows the CMS Peak luminosity

W-2 : 2.0uA W0 : 1.5 uA W-1 : 1.4 uA W+2 : 1.8 uA W+1 : 1.6 uA BARREL: The average RPC chamber current per wheel is lower than 2 µA for high luminosity beams except for W-2 which reached 2 uA Stable operation, No any chamber with abnormal behavior observed

ENDCAP: Higher currents comparing to Barrel Two disks reached 3 uA at the maximum instantaneous Luminosity Stable Operation, no any chamber with abnormal behavior of the dark current EP1 : 2.4 uA EP3 : 3.uA EN1 : 1.6 uA EN2 : 2.8 uA EP2 : 2.6 uA EN3 : 3 uA 14

Average current (uA) / Wheel,Disk Wheel/Disk Fill x 10*33 cm-2s-1 Fill x 10*33 cm-2s-1 Relative increase of Imon Cosmics W % 1.18 WM % 0.95 WM % 1.14 WP % 1.14 WP % 1.13 EN % 1.33 EN % 1.28 EN % 1.28 EP % 1.9 EP % 1.37 EP % week 21-22

 Individual HV value setting for each channel optimizing the WP of each chamber In 2010 RPC system worked with 2 common HV working points 9.35 kV (barrel) & 9.55 kV (Endcap) We wanted to define the WP of each chamber in order to  improve the performance of the system by fine tuning the position of the WP in the plateau chamber by chamber : i) avoid to stress the detector ii) less sensitive to the small environmental changes In 2010 not enough statistics to make a full efficiency scan In 2011 RPC collaboration put a lot of effort in doing a full high voltage scan chamber by chamber in order to identify the best working point (WP) of each RPC roll and each HV channel taking into account efficiency, cluster size, Noise and trigger rate 16 …more details see DPG presentation...

RPC average Hit Efficiency vs time Barrel Endcap CMS preliminary /4/ /6/201121/4/201107/6/2011 Average efficiency 94.9 ± 1 % (including all chambers)  Next step : Online Pressure correction of the Working Point  1% efficiency fluctuation due to pressure variation  reduce the spread of the HV effective values  keep safe the detector

During running period:  Temperature is almost stable.  Big variation in pressure (typically in the range mbar) During running period:  Temperature is almost stable.  Big variation in pressure (typically in the range mbar)

The Automatic Algorithm: Vinitial Enable/Disable correction RoT = 1 RoP Vbest MaxVAllowed MinVAllowed CalcularionError The Automatic Algorithm: Vinitial Enable/Disable correction RoT = 1 RoP Vbest MaxVAllowed MinVAllowed CalcularionError DETECTOR Values calculated automatically using the only P sensor available in UX Granularity per chamber New correction every mins, ready to be applied STB ON Last Vbests applied ONLY whenever the ON command is released (squeeze) No change whenever the sys is ON Vbest calculated but not applied. Possibility to apply the new vbest resending On command. Warning the operator in the rare cases a new correction is needed during the run 7000V Ready but not applied Applied ON Manual ON …………. … Algorithm- Flow diagram

The Online P correction will be deployed in the next TA. New DOC duties : i) checking if not abnormal values of the HV that will be applied during the transition to SQEEZE ii) in SQEEZE checking that the HV applied values are conformal to the expected one iii) if  V >50 Volts (  P~5mbar) during stable beams apply the new Voltage (SMS warning) iv) CMS center : monitor the currents

i)For the physics fills the CMS shift leader will call the RPC doc at the beginning of the ramp. Latest one hour after the call the OM has to be in P5 ii) He has to check the distribution of the HV values that will be applied to the system. He wait until the transition to physics ( RPCs ON) and he checks that the applied HV correction is the expected one iii)During stable beams : if  V >50 Volts (  P~5mbar) one SMS warning will be sent to the RPC phone. The OM has to go to P5 check the distribution of the new HV values and send the command ON manually on the system. NEW PROCEDURE for the OM: DM + OM :  check the currents OFF line  Check the HV dustributions before & after the correction

RPC Operation Performances 22

Trigger L1-RPC : 0:04:02min/ 535 hours A closer look to that 0% !.... No any significant RPC downtime & dead time during the last 3 months

Actually was a Trigger shifter fault! Fault of LV LB power supply 3.3 pb -1 of BAD runs du to the HV scan over 700 pb -1 recorded No any significant impact of the HV scan on the quality of the data  We decided to do an HV scan per year

Shifts OM shift instruction manual on twiki needs to be updated. To get the access rights in UXC, all the present and future OMs have to follow: i)BioCell training course register ii) CMS level-4 safety module (online 40 minutes) Follow at least the RPC weekly DPC &RC meeting. OM Training sessions will be organized in near future.

Run 2011 RPC shift The present table contains the requested shift per institution. The shift are calculated considering 48 weeks of runs and 3 shifter per week (DOC, DM and CAF) plus 15% of contingency. The request is to provide 2 shift(weeks)/EPS Shifts done or assigned up to 06/30/2011 M&O 2010# ESPNumber of required 2011 shifts (weeks)DOC 2011 (weeks) DM 2011 (weeks) CAF 2011 (weeks) Total shift done up to 06/30/2011 Peking univ SKK Univ (Korea) 2411 Korea Univ (Korea) Chonnam (Korea) 00 Mumbai-Barc (India) 12 Chandigarh (India) Ghent (Belgium) Brussel Univ (Blgium) 12 Uniandes 24 Pakistan Asrt-Enhep (Egypt) 3611 CERN 48 Bari INFN - LNF Napoli Pavia Sofia Univ Sofia INRE RPC TOTAL

August still 3 weeks are missing, september is empty :  please book RPC doc shifts !!! New OM shifters are welcome JOIN the CLUB No subscription fees! Car and petrol are provided !

Conclusions  Low Dark currents and background rates are following the beam luminosity no any unexpected behavior  Fine tune of the WP improved the performance and insures more safe conditions for the detector  Online P correction of the WP will insure more stable operating conditions  Improve instructions & the shift organization 28