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The Time Of Flight detector of the ALICE experiment

The Time Of Flight detector of the ALICE experiment. E. Scapparone (INFN – Bologna) on behalf of the TOF(*) Group QM2006, Nov 15, 2006. The role of the TOF in ALICE; The optimal detector choice: the MRPC; FRONT-END and Readout Electronics; Supermodule construction and test;

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The Time Of Flight detector of the ALICE experiment

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  1. The Time Of Flight detector of the ALICE experiment E. Scapparone (INFN – Bologna) on behalf of the TOF(*) Group QM2006, Nov 15, 2006 • The role of the TOF in ALICE; • The optimal detector choice: the MRPC; • FRONT-END and Readout Electronics; • Supermodule construction and test; • The installation of the first two supermodules • - Conclusions (*) INFN and University, Bologna (Italy) – INFN and University, Salerno (Italy) – ITEP Moskow (Russia) - Kangnung University (South Korea) The TOF detector of the ALICE experiment E. Scapparone

  2. p/K TPC + ITS (dE/dx) K/p e /p 0 1p(GeV/c) Particle Identification in ALICE HMPID p/K K/p 0 1 2 3 4 5 p(GeV/c) HMPID TPC ITS TOF (3.7 m from the beam pipe) p/K TOF (100 ps) e /p K/p p/K TOF ( 50 ps) e /p K/p The TOF detector of the ALICE experiment E. Scapparone 0 1 2 3 4 5 p(GeV/c)

  3. Large array to cover the ALICE barrel (~150 m2) Time resolution σ < 100 ps High efficiency, ε > 95% High segmentation: few thousands of particles per unit of rapidity expected in Pb-Pb collision at s = 5.5 TeV/nucleon pair TOF requirements: √ ALICE choice: a detector based on MRPC, segmented in ~157,000 channels, (3.5 x 2.5) cm2 area The TOF detector of the ALICE experiment E. Scapparone

  4. M = p ((t2 c2 /L2 )-1)1/2 σTOF = 80 ps ; B = 0.5 T The TOF detector of the ALICE experiment E. Scapparone

  5. Combined PID Performance Kaon PID (the most difficult case...) (Cp : CK : Cp= 0.75 : 0.15 : 0.1) Efficiency/Contamination TPC ITS TOF(*) (120 ps) p (GeV/c) p (GeV/c) p (GeV/c) Higher efficiency & Lower contamination wrt individual detectors Combined PID ITS & TPC & TOF (*) very conservative p (GeV/c) The TOF detector of the ALICE experiment E. Scapparone

  6. 157248 pads, total sensitive area: ~150 m2 A TOF SuperModule in the Space Frame 18 Supermodules, each made of 5 modules: 2 external(19 strips), 2 intermediate(19 strips), 1 central(15 strips) 7.4 m Readout performed by two VME Crates/Side 2 crates /side The TOF detector of the ALICE experiment E. Scapparone

  7. 0º 0.5º 1.6º 2.7º 3 .7º 4.8º 5.9º 6.9º 7.9 º 7.4º 8.5 cm 1º 3.2º 5.3º 15.30 cm 2.1º 4.3º 6.3º 99 cm 114 cm 492 415 349 276 209 138 70 Intermediate module 8.2º 9.3º 10.3º 11.4º 12.4º 13.4º 14.5º 15.5º 16.5º 17.5º 18.5º 19.5º 20.5º 21.5º 22.5º 23.4º 24.4º 25.4º 26.3º 27.3º 20.1º 22.1º 9.8º 11.9º 13.9º 16º 18º 25.9º 26.8º 19.1º 21.1º 10.8º 12.9º 14.9º 17º 23º 23.9º 24.9º 8.7º 134.30 cm 147 cm Outer module 27.3º 28.2º 29.2º 30.1º 31.0º 31.9º 32.8º 33.7º 34.6º 35.4º 36.3º 37.1º 37.9º 38.8º 39.6º 40.4º 41.2º 42.0º 42.8º 43.5º 44.3º 27.8º 30.5º 31.5º 37.4º 40.1º 40.8º 41.6º 42.4º 43.1º 32.3º 33.3º 34.2º 34.9º 35.8º 36.6º 38.3º 39.2º 43.9º 29.6º 28.7º 173 cm 178.2 cm Central module The TOF detector of the ALICE experiment E. Scapparone

  8. Cross section of a double-stack MRPC strip Differential signal to FEA card 2 rows of 48 readout pads (3.5 x 2.5 cm2) Active strip length = 120 cm The TOF detector of the ALICE experiment E. Scapparone

  9. MRPC CONSTRUCTION AND TEST IN BOLOGNA • 91MRPC strips /SM to be produced = 1638  Produced up to now ~1550 strips ~ 95 % of the total MPRC production -  Several quality assurance tests: -Signal connector soldering test; - Gap size test ; - Glass test; - HV test; - Cosmic test (sample); The TOF detector of the ALICE experiment E. Scapparone

  10. TOF front end electronics: 6552 FEA cards 3 NINO ASICs (8 ch) /card LV The benefit of the ASIC: - Input stage (and following) fully differential; - Adjustable input resistance ( 30 Ohm – 100 Ohm); - Power: 40 mW/channels (to be compared with 400 mW/channels of the COTS amplifier); - Nice matching with detector capacitance ( 30 pf ); - LVDS Output signal, compatible with HPTDC input To LTM The TOF detector of the ALICE experiment E. Scapparone

  11. DRM DRM LTM LTM CPDM TRM TRM TRM TRM TRM TRM TRM TRM TRM TRM TRM TRM TRM TRM TRM 30 High Performance TDC Chips LTM TRM TRM DRM TRM TRM TRM - FEA LV monitor - FEA thresh. set & monitor - FEAC temperature monitor - FEA OR signals for trigger - Wake up to TRD CPDM -VME master - TRM readout - DAQ (DDL) - L0,L1,L2 (TTC) - Slow control -Pulser to MRPC - Clock distribution TOF Electronics: 2 VME CRATES @ each SM side Crate left Crate right The chips contained in these boards were carefully tested in radiation (PSI, Louvain, Legnaro) and magnetic (CERN) enviroments. Taking advantage of the very fast time response, TOF partecipates to the ALICE L0 trigger ( T < 800 ns sfter the collision) The TOF detector of the ALICE experiment E. Scapparone - control

  12. An example: TRM (TDC Readout Module): 240 channels Leading and trailing edge measurements  signal width (TOT) for time slewing correction Each TRM is equipped with 10 piggy-backs. Each piggy-back contains 3 HPTDC ASIC chip ( 8 channels, 25 ps intrinsic resolution) The TOF detector of the ALICE experiment E. Scapparone

  13. Time slewing correction is mandatory to get extremely good time resolutions.TOT is a good charge substitute. The TOF detector of the ALICE experiment E. Scapparone

  14. Test beam of single strips Gas mixture: C2F4H2(90%) – SF6 (5%) – C4H10(5%) ε > 99.9 % average ~ 50 ps Efficiency Time resolution( ps) Similar results obtained when strips are inserted inside the modules The TOF detector of the ALICE experiment E. Scapparone

  15. Ageing study: two MRPC strips irradiated at GIF Time(min) Total charge = 14 mC/cm2 Charge/event = 2 pC 7 *109 events /cm2 @ 50 Hz/cm2 T=1.4 108 sec = 1620 days Pb-Pb run The TOF detector of the ALICE experiment E. Scapparone

  16. GIF results: No current increase I (mA) Flow = 1.4 cm3/s Source on Source on The gas going to the chamber 2 was bubbled through water for some time of the exposure Source off Source off The TOF detector of the ALICE experiment E. Scapparone

  17. GIF results Working voltage = 13 kV No ageing effect measured at PS The TOF detector of the ALICE experiment E. Scapparone

  18. TOF Modules moved to CERN Cosmic Facility Scintillator Trigger MODULE 1 MODULE 2 MODULE 3 MODULE 4 MODULE 5 Scintillator Trigger Modules are tested with the same electronics, service (HV+LV) and cables used in the experiment The TOF detector of the ALICE experiment E. Scapparone

  19. SUPERMODULE CABLING SM 1 during the cabling - FEAs ~750 cables/Supermodule HV Read out Crate Read out Crate LV Signal cables The TOF detector of the ALICE experiment E. Scapparone

  20. AFTER CABLING: START A NEW SET OF TESTS • Gas system. • Cooling system test  - pipe tightness, cooling test, temp monitor; • HV test up to 4000 V; • Power on the LV for crates ( 3.3 V ) + FEAs ( 2.5 V) + Vth measurement; • New Pulser test (a first pulser test on each module done when modules arrive at CERN ); • Readout checks; • - Slow control test, Data on Dim server, PVSS control. The TOF detector of the ALICE experiment E. Scapparone

  21. Installing the first TOF Supermodule The TOF detector of the ALICE experiment E. Scapparone

  22. Oct. 5, 2006 2 TOF SMs inserted The TOF detector of the ALICE experiment E. Scapparone

  23. CONCLUSIONS • MRPC is an optimal choice to achieve a time resolution below 100 ps • with high efficiency on a highly segmented detector (> 157,000 ch); • -Test beam, radiation and cosmic tests gave very good results in • terms of time resolution, efficiency and ageing; • MRPC strips production and front end + read out electronics • delivery  being completed; • First and second Supermodule of the ALICE TOF succesfully • installed; • The second TOF installing period is planned for May 2007. All productions (MRPCs, mechanics, electronics) well in progress. Installation of first 2 SM in July and August (20/7-2/8!!!??) will be “critical” test (as usual when you install “first” pieces.... + service ready?? + very short time window!) We are confident to have 2 (already inserted) + 8/9 SM assembled in January. Installation time @ the pit could be critical! The TOF detector of the ALICE experiment E. Scapparone

  24. RISERVE The TOF detector of the ALICE experiment E. Scapparone

  25. DISMOUNTING MODULES FROM COSMIC SETUP The TOF detector of the ALICE experiment E. Scapparone

  26. MOUNTING MODULES ON THE ASSEMBLY BENCH The TOF detector of the ALICE experiment E. Scapparone

  27. TOF construction (installation) schedule(Notice that, e.g., February = 28/02, April = 30/04, July = 31/07, ….) Electronics TRM+Crates+LV 30% production Nov. 2005 December 2006 TRM+Crates+LV 100% production Oct. 2006February 2007 DRM+Trigger Start production Nov. 2005March 2006 DRM 30 % production Feb. 2006December 2006 DRM 100 % production July 2006February 2007 Module construction 30% modules assembly February  July 2006 100% modules construction December2006 May 2007 SuperModules Installation (new ALICE installation schedule) Start installation SM [Stage 1] March  July 2006 End installation ( 2 SM) [Stage 1] July  August 2006 TOF production milestones : SM 50% (9 SM) ready for installationAugustDecember 2006 SM 100% (18 SM) ready for installationMarchAugust 2007 With the present ALICE installation schedule we foresee to install in February 2007 ~ 10 SuperModules. Notes : i) One complete order for TRM +Crates+ LV system ii) One complete order for DRM + Trigger system, to the same company as for TRM+ Crates + LV system The TOF detector of the ALICE experiment E. Scapparone

  28. 98.4 % The TOF detector of the ALICE experiment E. Scapparone

  29. Honeycomb Module production and assembly: • Module box + honeycomb production • (first company, BERCELLA) Completed within this summer • Interface card production  Completed within this summer • (second company, ELTOS ) • Interface card assembly on honeycomb • (third company, RAV) Completed within Dec. 06 Module box Supermodules status - 1st Supermodule  modules tested, mechanic structure mounted, cabling completed. - 2nd Supermodule  modules in the Cosmic test facility at CERN - 3rd Supermodule  working on the assembly The TOF detector of the ALICE experiment E. Scapparone

  30. LTM (Local Trigger Module)  4/Supermodule  TOTAL = 72 Production 5 produced and tested  OK for 1° SM schedule 4 expected within Jun 06  OK for 2° SM 32 expected within Sep 06 40 expected within Nov 06 The TOF detector of the ALICE experiment E. Scapparone

  31. CPDM (Clock and Pulser Distributor Module): 1 per 2 SMs TOTAL = 36 Pulser CLK Da mettere foto piu’ recente.... Production 2 produced and tested schedule 7 expected within Jun 06 (OK for 4 SMs) The TOF detector of the ALICE experiment E. Scapparone

  32. TOF Standalone PID (80 ps res. as in the PPR)

  33. GIF results No current increase No current increase I (mA) Source on Source on Source off Source off E. Scapparone RPC2003 The TOF detector of the ALICE experiment E. Scapparone

  34. detection (0.02 ppm), I.e. no trace of HF in the samples ppm Chemical analysis (Chromatography) of the outgoing gas from both MRPCs (CH1, CH2) by CERN EST/SM - CP : measured concentration of Fluorine under the limit of - Active detector volume is 2% of the total volume of the gas box; - Diffusion for the gas exchange between strip and the surrounding gas. • No sign of degradation; - No increase of dark current; - No degradation in efficiency; - No degradation in time resolution; E. Scapparone RPC2003 The TOF detector of the ALICE experiment E. Scapparone

  35. POSITION SCAN ACROSS BOUNDARIES Sharing of charge between neighbouring pads causes : Global efficiency loss due to boundaries < 2% Global double hit probability ~15% Deterioration in resolution at the borders Could use algorithm like average, pulse height weighted average etc.. Sharpness of boundaries depends on : Threshold/dynamic range of charge spectrum Size of footprint of avalanche on pickup pads The TOF detector of the ALICE experiment E. Scapparone

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