T0 status1W.H.Trzaska HIP Jyväskylä Status of T0 project ALICE Comprehensive Review IV March 23, 2004

T0 status2W.H.Trzaska HIP Jyväskylä The main physics objectives Precise start signal for TOF –(does not have to be on-line) Trigger functions (on-line): –Rough vertex position –Rough multiplicity (V0 backup) –vertex-independent interaction time “wake-up” signal to TRD

T0 status3W.H.Trzaska HIP Jyväskylä Design considerations detectors on both sides of the interaction point compact design (minimal space on RB 26 side) time resolution of about 50 ps; position resolution (along the beam direction)  1 cm; laser calibration system total dead time of less than 25 ns (40 MHz BC); operation in the magnetic field of up to 0.5 Tesla; radiation hardness up to 500 krad; reasonable multiplicity resolution for charged particles; high reliability & maintenance-free operation.

T0 status4W.H.Trzaska HIP Jyväskylä Detector choice  Cherenkov radiator + PMT 2 x 12 PMT units Choice of PMT models and manufacturers: –Hamamatsu R5506 (Japan) Considerably more expensive(–) No direct link to the production plant(–) No possibility to “hand-pick” the tubes(–) Well-established company(+) –Electron FEU-187 (Russia) Same performance(+) Full compatibility with R5506 (if needed)(+) Slightly larger diameter(+) Our choice

T0 status5W.H.Trzaska HIP Jyväskylä Radiator choice & length Possible materials (good timing, UV transparent) –Acrylic (Lucite) Prone to radiation damage (above 100 krad) –Quartz Heavier (0.25 X0 / 0.1 X0 for 3 cm quartz / Lucite) Calculated radiator length  3 cm –Cherenkov light emission band is nm –N ph = 2  (1/ 2 - 1/ 1 ) sin 2  (per cm length) –n =  cos  = 1/n =  sin 2  = 0.53 –average quantum efficiency of the photo cathode =15% Our choice

T0 status6W.H.Trzaska HIP Jyväskylä Radiator’s diameter – not yet fixed 3.0 cm – matches the outside diameter of PMT –Higher efficiency in p-p collisions (+) –Slightly more material (–) –Little worse time resolution (edge effects) (–) 2.5 cm – matches the size of the photo cathode –Improved time resolution (to be measured) (+) –Less material (1/1.44) (+) –Reduced efficiency for p-p (–) 3.0 cm – T0-R 67% : T0-L 60% : R&L 48% 2.5 cm – T0-R  47% : T0-L  42% : R&L  23% Will be determined experimentally June 2004

T0 status7W.H.Trzaska HIP Jyväskylä Latency questions Latency of time signal from T0-Right to the rack –IP  PMT cm/ns = 2 ns –Delay inside PMT = ~15 ns –Delay on 25 m of cable (5ns/m)= 125 ns –Fast Signal Processing (stage I)= ~45 ns –T0 Vertex (FSP stage II)= ~43 ns sub TOTAL (trigger)= 230 ns T0 Rack  TRD (20m?) ns Not acceptable!= 330 ns To provide TRD wake-up call T0 shoeboxes will be inside the magnet! fixed

T0 status8W.H.Trzaska HIP Jyväskylä Cable layout & length Too far out! Accessibility of the shoeboxes! T0-Right shoebox

T0 status9W.H.Trzaska HIP Jyväskylä Quiescent Current +6 V mA Max Current +6 V mA -6 V mA -6 V mA Amplifier-Transmitter Based on Op-Amp OPA MHz bandwidth, 4300 V/us slew rate. Inside the shoebox:

T0 status10W.H.Trzaska HIP Jyväskylä Left Shoe-boxRight Shoe-box Left t0 detection system - 12 Cerenkov detectorsRight t0 detection system - 12 Cerenkov detectors TRD Wake-up Unit 12 Amplifier-Transmitters PowerConsumption: Quiescent: +6V, 1A -6V, 1A Max: +6V, 3A -6V, 3A 12 Amplifier-Transmitters + TRD WU 24 cables 12 cables

T0 status11W.H.Trzaska HIP Jyväskylä T0 + TRD Combined shoebox preliminary

T0 status12W.H.Trzaska HIP Jyväskylä T0 data flow challenge 24 PMTs (2  Ampl. + 2  Time) + N = MHz (BC rate in pp):  25 ns dead time required! Dead time for all triggering functions is  25 ns  no loss of trigger pulses (guarantied!) To provide also the readout system with 25 ns dead time is not trivial (corresponds to several Gb/sec of dataflow) –It is possible with the existing hardware by using 16-fold demultiplexer (  16 more hardware) –Is it really needed?

T0 status13W.H.Trzaska HIP Jyväskylä T0 data readout options T0 will use TOF readout –TOF is the main and by so far the only detector that needs non-trigger data from T0 –amplitude from T0 PMTs will be converted to time log(Amplitude)  Time There are 2 possible options: –With 16  demultiplexer (dead time  25 ns)  ready for data readout within 25 ns of the previous data  16  hardware; guarantied digitisation of all data –Without demultiplexer (dead time  400 ns)  Small percentage of the trigger events will lack the digitised amplitudes and times of PMT pulses

T0 status14W.H.Trzaska HIP Jyväskylä Strobe options (without demultiplexer) No strobe –If any of the T0 PMTs fires within BC it will be send to the readout and block it for the duration of about 250 ns –Some “important” trigger events may not be digitised T0 vertex strobe –Readout only if T0 vertex generated –All “important” trigger events digitised –All “unimportant” trigger events are not digitised

Digital Variable Attenuator DA S-830-9/125-M-35 Laser Calibration System Picosecond Injection Laser PIL040G, 408 nm Splitter FOBS SSS /50 RS fibers to Cerenkov detectors MM patchcord SM patchcords T0 rack Start 66/34 4 spare 50/50 25%75% of laser power100% of laser power

T0 status16W.H.Trzaska HIP Jyväskylä Key electronics modules of T0 Mean Timer – produces on-line timing signal indicating accurate interaction time T 0 = ½ (T LEFT + T RIGHT ) T0 Vertex – gives an on-line ON/OFF signal indicating location of the vertex within the given limits. Selectable range  70 cm; accuracy  1 cm; dead time < 25 ns Fast Front-End electronics – amplifier + CFD stage to produce high quality time and amplitude signals for on- and off-line processing. Must be capable to handle very large dynamic range (about 1:500)

T0 status17W.H.Trzaska HIP Jyväskylä T0 Mean Timer performance Generated mean time signal remained perfectly constant within our measurement accuracy: 0  10 ps

T0 status18W.H.Trzaska HIP Jyväskylä T0 Vertex Module Resolution fwhm = 3 cm  = 1.3 cm Range  88cm 7mm(23ps)/step 256 steps Eff. = 98% Profile doesn’t depend on the threshold value

T0 status19W.H.Trzaska HIP Jyväskylä We could not test in the full dynamic range! T0 time resolution (with PS particles) TOF FWHM=124 ps  = 37 ps Measured TOF spectrum

T0 status20W.H.Trzaska HIP Jyväskylä T0 Milestones DateMilestone May 2004Laser calibration I June 2004TDR text completed June 2004Test run at CERN July 2004Integration test August 2004T0 Technical Project I September 2004Final cabling inside L3 September 2004TDR in print October 2004Quartz radiators production November 2004Purchase of PMTs December 2004Laser calibration II September 2005T0-R & T0-L assembled October 2005Pre-shipment tests November 2005T0 shipped to CERN December 2005Final tests March 2006T0 installation