1. SPD commissioning Ricci, Míriam, Daniel, Edu, Hugo et al. from 1

2. Outline SPD calibration with cosmics V ref calibration LED intensity: limits and current status SPD hardware LED features 2

3. Calibration with cosmics Have to set threshold @ 0.5 – 0.7 MIP MIP computed by multiplying calibration of components – nPhes from Evgeni: cosmics with the detector “on a table” Check MIP computation with cosmics: 1) Make sure that SPD occupancy looks uniform on ECAL&&HCAL cosmics 2) Try to compare efficiency with expectation 3 R. Vázquez

4. Uniformity Cosmics allowed to solve a bug in HV settings in a few PMTs Reasonable uniformity after correction: 4 Threshold @ 0.5 MIP 1 M events Threshold @ 1.5 MIP 0.5 M events R. Vázquez

5. Global SPD efficiency Tried to define a clean sample: – Track extrap. >2  away from acceptance limits – No multiple hits in SPD – Track extrap.  x,  y < 150 mm – Energy in PS > 40 ADCs – PS cell and track extrap. in 3  & only 1 cell – Look in any BX Still, efficiency lower than expected – Reason: time of arrival 5 R. Vázquez

6. Efficiency vs arrival time 6 R. Vázquez 0.5 MIP 1.5 MIP 100%50% Arrival time (ns)

7. With perpendicular cosmics Selecting cosmics with  x/  x  < 1.2 7 0.5 MIP1.5 MIP 100%50% Arrival time (ns)

8. Threshold voltage vs V ref V th = 0.65 · V ref ·(n/63), n  internal DAC reg. Physics setting: in each VFE, minimum V ref that can provide 1 MIP in all channels – To minimize step size, hence resol on threshold But will need  2 MIPs for threshold scans How stable is calibration under changes in V ref ? Checked by measuring noise offset by performing threshold scans with different V ref 8

9. Threshold dependence of V ref Checked with V ref = 555 mV vs V ref = 1560 mV Dispersion lower than 1 step (5-15 mV) Slight bias due to choice of step (will be optimized) 9 Míriam  V off (V)

10. LED system Light intensity being adjusted by Evgeni Limit on LED light? – Occupancy wrt 40 MHz @ 2·10 32 : (0.001,0.03)  (40K, 1.2M) MIP·s -1 – LED system: 40 MHz / (3564 * 5 ) = 2.2 KHz A LED flashing @ 20 MIP is contributing between 3% and 100% of the light from physics 10

11. Measuring LED intensity 11 Idea: change SPD threshold to a very high value and look for signal Electronics allows for a maximum of 6 MIPs if we want to have uniform thresholds in the whole SPD Max SPD threshold in MIPs

12. LED results: intensity Complete results from runs from 25 th Jan at: http://lhcb.ecm.ub.es/~lhcb/2009/jan/27/ http://lhcb.ecm.ub.es/~lhcb/2009/jan/27/ All in the form of LED-timing scans: LED trigger delay from 0 to 25 ns with steps of 1ns Look at many BXs: can study duration of signal Edu, Evgeni will explain details, here just flash some results 12 Míriam/Daniel

13. VFE 35 / Trigger 40 / Vled(8) = 1750 0.5 MIPs Old HV settings Vled = 1700 2 MIPs 6 MIPs 13 Míriam/Daniel C side Too much light!

14. VFE 21 / Trigger 43 / Vled(7) = 1750 0.5 MIPs Old HV settings Vled = 1700 2 MIPs 6 MIPs 14 Míriam/Daniel C side Far too much light! Remember subtractor 20% of previous BX How many MIPs?

15. VFE 40 / Trigger 40 / Vled(8) = 1750 0.5 MIPs Old HV settings Vled = 1800 15 Míriam/Daniel C side Too little light

16. VFE 91 / Trigger 41 / Vled(8) = 1700 0.5 MIPs Old HV settings Vled = 1700 16 Míriam/Daniel A side Far too little light

17. 2/Feb/2009SPD shutdown activities and LED checks 17 SPD electronics status Checks on 1 VFE which showed problems: –VFE number 2 (crate PRS0, CB5, channel2) on C-side –No communication between VFE and CB before Christmas. Now OK. –Possible causes: VFE problem Control/clock cable problem (as 2 other from same bundle) Metal dust inside EE box –Actions done: As VFE worked last week, just clean all dust. Wait until all detectors are closed on C-side (if the cable is the problem) or the problem apears again –Solution if the cable is found broken: Use another box control/clock spare cable and extension. It is not feasible to pass a few new control/clock cables to the problematic zone through the chain.

18. 2/Feb/2009SPD shutdown activities and LED checks 18 SPD shutdown activities: tests VFE tests: –LED measurements Uniformity study and adjustment (Evgeny) Run types: –Simple measurement (just apply a trigger pattern) –Time alignment scan (change delay on the trigger of the LEDs) –Threshold scan (modify threshold values on each step) –Offset measurements Threshold scan with and without HV Repeat for various Vref and to check stability –Mapping test Check the DAQ vs. VFE channel mapping To do it once

19. A-side V(2)=2800 V(7)=2450 V(8)=1700 V(9)=2400 V(10)=2500 C-side V(2)=2100 V(7)=1750 V(8)=1750 V(9)=2100 V(10)=1750 19 Bias applied

20. 2/Feb/2009SPD shutdown activities and LED checks 20 VFE 33 / Trigger 42 / Vled(8) = 1750 0.5 MIPs Old HV settings Vled = 1700 2 MIPs Problems with LEDTSB, VFE configuration?

21. 2/Feb/2009SPD shutdown activities and LED checks 21 VFE 38 / Trigger 41 / Vled(8) = 1750 0.5 MIPs Old HV settings Vled = 1700 2 MIPs 6 MIPs Trigger signal reflections

22. BACK-UP 22

23. Occupancies lumi2 lumi5 23

24. Conclusions on LEDs C-side: – Most VFE have signal with threshold @ 6 MIPs V LED (2, 7, 9, 10) too low; V(8)~OK? A-side: – Some VFE signal too low (@ 0.5 MIP) V LED (2,8) too high; V(7, 9, 10) ~OK? – Problems with triggers 31, 32, 38, 39 (V LED not controlled) and 42, 56 (not triggered) – VFE 65(?), 66 no HV 24

25. ‘Teor’ Delays from data Some discrepancies for inner, ~ 3ns. (Check teor fiber delays.) Wait for fine time alignment with first collisions. 25 Time alignment Míriam With 2.6 M cosimic events analyzed:

26. Material traversed by cosmics 26 R. Vázquez (-5<t<5)(15<t<25)

27. Offset difference in Volts VV V V 27 RUN 36187 (V ref = 555 mV) vs RUN 36204 (V ref = 1560 mV) Míriam