Run Coordination Report

4th RPC General Meeting (CMS week)

Luigi BENUSSI, Hassan SHAHZAD, Nicolas ZAGANIDIS

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RPC Operation overview

• LHC achievements & plans• Detector behavior • Online P correction• Operation performances• Shifts• Conclusions

LHC achievements

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

LHC achievements

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

LHC plans

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 bunchesDecrease the emittances, populate the bunches expected pileup rate : x ~3

CMS reached the fb-1

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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

….More details in the TC presentation…

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Number of active electronic channels is stable ~ 98.5%

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Barrel z dependence: 2010 (left) vs. 2011 (right, CMS PRELIMINARY)

2010

2011

Background rate vs Instantaneous LuminosityFor 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-11.053x10*33 cm-2s-1 Dimon= 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 uAStable operation, No any chamber with abnormal behavior observed

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ENDCAP:Higher currents comparing to BarrelTwo disks reached 3 uA at the maximum instantaneous LuminosityStable Operation, no any chamber with abnormal behavior of the dark current

EP1 : 2.4 uA

EP3 : 3.uA

EN1 : 1.6 uAEN2 : 2.8 uAEP2 : 2.6 uA

EN3 : 3 uA

week 21-22

Average current (uA) / Wheel,Disk

 Wheel/DiskFill 1813

1.053x 10*33 cm-2s-1

Fill 18151.27x 10*33

cm-2s-1

Relative increase of

ImonCosmics

W00 1.42 1.47 3.5% 1.18

WM1 1.36 1.43 5.1% 0.95

WM2 1.90 2.03 6.8% 1.14

WP1 1.51 1.57 4.0% 1.14

WP2  1.77 1.92 8.5% 1.13

 EN1 1.64 1.69 3.0% 1.33

 EN2  2.62 2.89 10.3% 1.28

EN3 2.65 2.94 10.9% 1.28

EP1 2.16 2.26 4.6% 1.9

EP2 2.35 2.51 6.8% 1.37

EP3 2.73 2.99 9.5% 1.37

01-06-11

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Individual HV value setting for each channel optimizing the WP of each chamber

In 2010 RPC system worked with 2 common HVworking 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 changesIn 2010 not enough statistics to make a full efficiency scanIn 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

…more details see DPG presentation ...

RPC average Hit Efficiency vs time

Barrel Endcap

CMS preliminary 2011 CMS preliminary 2011

21/4/2011 07/6/2011 21/4/2011 07/6/2011

Average efficiency 94.9 ± 1 % (including all chambers)

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 945-975 mbar)

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 10-20 mins, ready to be applied

Vbest-5 Vbest-4 Vbest-2 Vbest-1

Vbest -1

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

Vbest -1 Vbest -1

7000V

Vbest

Vbest Ready but not applied

Applied

Vbest+100Vbest+1 Vbest+2 Vbest+10

ON

Man

ual O

N

Vbest +10

………….

…

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 DV >50 Volts (DP~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 P5ii) 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 oneiii)During stable beams : if DV >50 Volts (DP~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

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RPC Operation Performances

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

recordedNo 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 Isabelle.Cusato@cern.ch 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 # ESP Number of required 2011 shifts (weeks)

DOC 2011 (weeks)

DM 2011 (weeks)

CAF 2011 (weeks)

Total shift done up to 06/30/2011

Peking univ 2 4 1.4 1.4SKK Univ (Korea) 2 4 1 1Korea Univ (Korea) 10 20 3.6 3.6Chonnam (Korea) 0 0Mumbai-Barc (India) 1 2Chandigarh (India) 3 6 6.4 6.4Ghent (Belgium) 9 18 6 4.6 2 12.6Brussel Univ (Blgium) 1 2Uniandes 2 4Pakistan 6 12 5 5Asrt-Enhep (Egypt) 3 6 1 1CERN 4 8Bari 12 24 1 4 5INFN - LNF 5 10 7 7Napoli 9 18 5.9 5.9Pavia 3 6 2 2 1 5Sofia Univ 6 12 6 3 3 12Sofia INRE 6 12 2 3 5RPC TOTAL 84 168 29 22.5 19.4 70.9

• August still 3 weeks are missing, september is empty :

please book RPC doc shifts !!!

New OM shifters are welcome

JOIN the CLUBNo subscription fees!

Car and petrol are provided !

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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