1. Commissioning the LHCb VErtex LOcator (VELO) Mark Tobin University of Liverpool On behalf of the LHCb VELO group July 28, 2008Vertex 2008: 17th International Workshop on Vertex detectors 1

2. Overview Introduction LHCb experiment. The Vertex Locator (VELO). Description of System. Commissioning the subsystems. Commissioning the full system Status. July 28, 2008 Vertex 2008: 17th International Workshop on Vertex detectors 2

3. Motivation for LHCb LHCb designed to study:  Heavy flavour physics  CP-violation in b sector  Constrain unitarity triangles  Rare B decays  Search for New Physics B meson production:  bb-pairs correlated in space. July 28, 2008 Vertex 2008: 17th International Workshop on Vertex detectors 3

4. LHCb detector design 27th July, 20084 Vertex 2008: 17th International Workshop on Vertex detectors

5. LHCb detector rotated 27th July, 2008 Vertex 2008: 17th International Workshop on Vertex detectors 5

6. LHCb detector (Reality) 27th July, 2008 Vertex 2008: 17th International Workshop on Vertex detectors 6 VELO Muon det Calo’s RICH-2Magnet OT+IT RICH-1 Installation of all detectors is complete

7. Vertex detector requirements Event reconstruction:  Precise tracking  Low mass Vertexing:  Need to separate primary/secondary interactions  Close to beam in extreme radiation environment. Trigger:  Fast reconstruction of primary vertices.  R-Φ sensor geometry. LHC beam tolerance:  Detector must be 30mm from beam at injection July 28, 2008 Vertex 2008: 17th International Workshop on Vertex detectors 7

8. VErtex LOcator 2 retractable halves 5mm from beam when closed 30mm from beam during injection 21 R-Ф modules/half Operates in secondary vacuum (<10 -4 mbar) 300μm foil separates detector from beam vacuum (<10 -8 mbar) 2 phase CO 2 cooling system 27th July, 2008 Vertex 2008: 17th International Workshop on Vertex detectors 8

9. Vacuum system 27th July, 2008 Vertex 2008: 17th International Workshop on Vertex detectors 9 Detector separated from beam vacuum by 300μm Aluminium foil Maximum allowed differential pressure is 5mbar Shape allows overlapping sensors VELO sensors PileUp sensors RF-foil

10. n strip sensor technology (Micron) Double metal layer for signal routing. R sensors:  45 degree quadrants  Pitch=40-101μm Ф sensors:  2 regions  Short/long strips  Pitch=38-100μm  Stereo angle. Sensor Design July 28, 2008 Vertex 2008: 17th International Workshop on Vertex detectors 10

11. Radiation tolerance n + in n-bulk sensors Strip isolation via p + spray 300μm thick Harsh non-uniform radiation environment  1.3x10 14 n eq /cm 2 /year at 8mm  5x10 12 n eq /cm 2 /year at 42mm Run partially depleted after 3-4 year (8fb -1 )  Reduced CCE July 28, 2008 Vertex 2008: 17th International Workshop on Vertex detectors 11 type inverted not type inverted after 1 year of irradiation [2 fb -1 ] R [cm] U dep [V]

12. Module design July 28, 2008 Vertex 2008: 17th International Workshop on Vertex detectors 12 Double sided hybrid to balance stresses due to “bi-metallic effects”. Thermal pyrolytic graphite core removes 24W of heat (ΔT=20C). Carbon fibre cover for rigidity. 2 phase CO 2 cooling system  Sensors operate at -5C Non-planarities ~250μm Sensor-sensor < 10μm Readout with 16 Beetle chips:  2048 channels/sensor.  172032 channels in VELO.

13. Material budget July 28, 2008 Vertex 2008: 17th International Workshop on Vertex detectors 13

14. Material budget/component July 28, 2008 Vertex 2008: 17th International Workshop on Vertex detectors 14

15. Module production (to be repeated) July 28, 2008 Vertex 2008: 17th International Workshop on Vertex detectors 15 6 Visual Inspections, 6 Metrologies, 7 Electrical Tests, 4 Vacuum Tests

16. VELO Assembly @ CERN July 28, 2008 Vertex 2008: 17th International Workshop on Vertex detectors 16

17. Installation July 28, 2008 Vertex 2008: 17th International Workshop on Vertex detectors 17

18. Installation July 28, 2008 Vertex 2008: 17th International Workshop on Vertex detectors 18

19. What the LHC sees during injection… July 28, 2008 Vertex 2008: 17th International Workshop on Vertex detectors 19

20. Overview of VELO electronics July 28, 2008 Vertex 2008: 17th International Workshop on Vertex detectors 20 All components installed. Each system commissioned stand-alone first.

21. Readout Board (Tell1) Analog input from 64 links 10 bit ADC @ 40MHz [A- Rx] FPGA for pre-processing  Cross-talk, common mode suppression, clustering  Zero suppression of data Data sent out by Gigabit ethernet Max output rate is 1.1MHz Control via credit card PC 27th July, 2008 Vertex 2008: 17th International Workshop on Vertex detectors 21 ARX GBE TTCRx CCPC

22. Control system and DAQ All cables and boards installed Extensive testing programme:  ADC cards [A-Rx]  Readout boards [Tell1]  Control boards  Readout slices – Timing – Cable checks – Noise levels July 28, 2008 Vertex 2008: 17th International Workshop on Vertex detectors 22 adjustment of timing to 0.65 ns

23. Low voltage system Standard Easy3000 CAEN system 1 mainframe controller 3 48V power convertors 22 8V/9A 12 channel power supply boards. 2 modules per power supply board. July 28, 2008 Vertex 2008: 17th International Workshop on Vertex detectors 23

24. Problems with LV system Reliability of A3009 8V/9A supplies  Many were sent back to CAEN  Mean = 0.58 Bad connections to front of supply.  Solder leakage on manufacture of connectors. July 28, 2008 Vertex 2008: 17th International Workshop on Vertex detectors 24

25. Safety problem with A3009 modules Tried many safety test.  One problem found. Communication cable was pulled.  Channels stayed on. Jumpers from interlock were pulled.  Channels stayed on. Simultaneous loss of cooling  Rapid heating of hybrid. Firmware fix from CAEN Currently not used. July 28, 2008 Vertex 2008: 17th International Workshop on Vertex detectors 25

26. High Voltage System ISEG EHQ 607n-F 5 Iterations of OPC Server from ISEG An example problem: – Ramp channel one – Turn on channel two – Channel one jumps to target voltage Remaining problem – OPC server crashes ~ once per week Company engineers extremely helpful but a long (and not yet finished) process

27. Commissioning the VELO (I) Single module operation under Neon atmosphere – 18 th March 2008.  Final cooling, vacuum, LV, HV, interlocks, DAQ and control software  Looked at IV scans  Data taken in various configurations Noise level compared with previous data taken in assembly Single module test repeated for all modules on 1st side – 5 th May onwards Warm cooling (8C) Modules operated at 25C Differential pressure between 2 and -5mbar Operation of 15 modules on 15 th May 2008 27th July, 2008 Vertex 2008: 17th International Workshop on Vertex detectors 27 R-side not CM corrected CM corrected Differential pressure

28. Commissioning the VELO (II) Single module test of 2 nd half – from 2 nd June. Full half powered for first time – June 10 th. Many problems found.  Failure and replacement of broken read-out boards.  Problems related to fabrication of Tell1 boards. Preparation for operation under vacuum. 27th July, 2008 Vertex 2008: 17th International Workshop on Vertex detectors 28

29. VELO under vacuum Full detector operated under vacuum after beam evacuated. Operated cooling fully loaded at -25C  Modules @ -5C  Cooling of rf foil affects beam pressure. Majority of data taking during commissioning at -5C  Modules @ 14C.  Minimize thermal cycling of modules. July 28, 2008 Vertex 2008: 17th International Workshop on Vertex detectors 29 10 -5 10 -8

30. System @ full power July 28, 2008 Vertex 2008: 17th International Workshop on Vertex detectors 30 First operation of full system: 01:40 28 th June 2008

31. Data taking Non-zero suppressed data:  300000 events  10Hz with limited event builder. Zero suppressed data (with test pulses)  1kHz with limited event builder.  1/100 th of design rate. July 28, 2008 Vertex 2008: 17th International Workshop on Vertex detectors 31

32. Noise performance July 28, 2008 Vertex 2008: 17th International Workshop on Vertex detectors 32 Phi sensor R sensor Raw noise Common mode subtracted noise

33. Noise all sensors PHI R Mean = 2.062 +/- 0.155 Mean = 1.894 +/- 0.167

34. Noise comparison between single module power up and system power up July 28, 2008 Vertex 2008: 17th International Workshop on Vertex detectors 34

35. Status Installation Module production and assembly of detector halves – March 2007 All other systems installed:  Cooling  Vacuum  Positioning system.  High voltage  Low voltage Installation of detector halves – October 2007 Connected the cables to the modules. Full system operation – June 2008 Outstanding issues Integration into LHCb global running. 3 broken Tell1 boards to be replaced. Data taking at high rates. Software improvements:  Online monitoring. Wait for first beams. July 28, 2008 Vertex 2008: 17th International Workshop on Vertex detectors 35

36. Conclusions All components fully installed and tested. Extensive commissioning programme over last year. First operation of whole detector under vacuum  99.2% of channels fully operational. LHCb VErtex LOcator in good shape for first beams July 28, 2008 Vertex 2008: 17th International Workshop on Vertex detectors 36