1 ALICE T0 detector W.H.Trzaska (on behalf of T0 Group) LHCC Comprehensive Review, March 2003

W.H.T.LHCC Comprehensive Review, March Evolution of T0 detector concept Initial proposal (TP, MoU) one detector does it all (MCP) cost ~1.5 MCHF (Greece, Russia) Fall 2000 split of FMD into 3 sub.detectors:  Si FMDV0  Si FMD, V0 and T0  T0 (cost ~200 kCHF) Spring 2001 Choice of PMT-based T0 (worked-out by a Russian team) Spring 2002 Finland commits 200 kCHF to T0 and joins the T0 collaboration

W.H.T.LHCC Comprehensive Review, March T0 must work for all ions and for all energy densities central minimum bias

W.H.T.LHCC Comprehensive Review, March Main requirements: Precise timing (50 ps) also on-line Main LVL0 trigger Rough on-line vertex (1.5 cm) Beam – gas suppression Pre-trigger for TDR Event spacing 25 ns (pp) Provide backup for V0 and FMD Operates in the magnetic field (0.5 T) Huge dynamic range (almost 1:1000)

W.H.T.LHCC Comprehensive Review, March T0 – the final configuration: Two arrays of 12 PMTs with quartz radiators T0 Right ( m) T0 Left ( m) Two shoe boxes of fast electronics inside the magnet (+5 m and –5 m) Few creates of electronics outside the magnet Laser calibration system also outside the magnet

W.H.T.LHCC Comprehensive Review, March Output signals: T0 = (t r +t l )/2+t d T0 v = t r -t l (ON/OFF adjustable during run) T0-L, T0-R, Coinc Time and energies (all 24 PMTs) 3 levels of sum energy Low Medium High

W.H.T.LHCC Comprehensive Review, March T0 Left & T0 Right arrays: T0 L -5 <  < -4.5 T0 R 2.9 <  < 3.3

W.H.T.LHCC Comprehensive Review, March Mechanics – T0 Right

W.H.T.LHCC Comprehensive Review, March T0 Left

W.H.T.LHCC Comprehensive Review, March T0-Right 1:1 prototype: T0-Right 1:1 prototype:

W.H.T.LHCC Comprehensive Review, March Front view:

W.H.T.LHCC Comprehensive Review, March Back view:

W.H.T.LHCC Comprehensive Review, March End-cups on the base side:

W.H.T.LHCC Comprehensive Review, March Mounting of the optical fibre (  0.4 mm)

W.H.T.LHCC Comprehensive Review, March PiLaser PiLaser 400 nm pulse width <40ps roughly 400mW optical peak out of the fibre

W.H.T.LHCC Comprehensive Review, March Possible location of shoe boxes: Box 50 W Box 50 W 12 PMT full current <15 W

W.H.T.LHCC Comprehensive Review, March Inside the shoe box: Dual CFD Unit Dual CFD Unit

W.H.T.LHCC Comprehensive Review, March Characteristics of the Dual CFD Unit

W.H.T.LHCC Comprehensive Review, March Pre-TDR timetable Production completed by July 2005 Fully assembled T0 Tests before shipment to CERN Oct Shipment to CERN – November 2005 Final tests – December 2005 Installation in ALICE – March 2006

W.H.T.LHCC Comprehensive Review, March Pre-TDR financing 200 kCHF from Finland Sufficient to cover the detector and front- end electronics Readout electronics and integration with DAQ Collaboration with TOF group Greek contribution

W.H.T.LHCC Comprehensive Review, March Highlights of 2002: Completion of the first draft of TDR (100 pages!) Mechanical prototype of T0 Right Final multiplicity resolution simulations Electronic prototypes: Dual CFD Unit (2 prototypes) Mean timer Circuit for generating T0 V signal Choice of laser and the layout of the laser calibration system

W.H.T.LHCC Comprehensive Review, March Still to be chosen: Final choice of time discriminators (test CERN in July 2003) Final configuration of readout electronics, DAQ and trigger collaboration with TOF discussions with the Greek team

W.H.T.LHCC Comprehensive Review, March Measured performance of CFDU (JYFL) prototype 5.3 ps/ch Jitter = 25 ps (fwhm)

W.H.T.LHCC Comprehensive Review, March The third option: T0T0 T logA

W.H.T.LHCC Comprehensive Review, March Mean timer prototype

W.H.T.LHCC Comprehensive Review, March T0 V DC Fast digitiser for T0 V signal Range of coded time intervals ±2.5 ns Digitisation step 20 ps (for 8-bit) Dead time not more than 25 ns TAC + Flash ADC

W.H.T.LHCC Comprehensive Review, March T0 V DC performance Delay [ns] vs. channel number Calibration spectrum

W.H.T.LHCC Comprehensive Review, March Cables and connection from L3 HV cables 2 x 12 Coaxial cables Thresholds2 x 12 Bunch crossing2 x 1 Time individual2 x 12 Output Amplitudes2 x 12 TRD wake up2 x 4 T0 right/left2 x 1 Optical fibre 2 x 12

W.H.T.LHCC Comprehensive Review, March General, preliminary readout scheme for T0:

W.H.T.LHCC Comprehensive Review, March Layout and connections:

W.H.T.LHCC Comprehensive Review, March Large change compared to the previous version of PYTHIA: Efficiency of registration of p-p collisions