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Preliminary Design of Trigger System for BES III

Preliminary Design of Trigger System for BES III. Zhen’an LIU Inst of High Energy Physics,Beijing Oct. 14 2001. Outline. Introduction Estimation of event rate The principle of BESIII trigger Subsystems Description Summary. BEPCI: low luminosity(3 10 30 cm -2 s -1 ) .

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Preliminary Design of Trigger System for BES III

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  1. Preliminary Design of Trigger System for BES III Zhen’an LIU Inst of High Energy Physics,Beijing Oct. 14 2001

  2. Outline • Introduction • Estimation of event rate • The principle of BESIII trigger • Subsystems Description • Summary BESIII Workshop, IHEP, BEIJING

  3. BEPCI: low luminosity(310 30cm-2s-1). Single bunch mode bunch separation: 800ns trigger:latch-process-decision Introduction BEPCII • BEPCII: • double ring • high luminosity(10 33cm-2s-1). • multi-bunch mode • bunch separation 8ns TRIGGER FOR BESII CAN NOT BE USED IN BESIII BESIII BESIII Workshop, IHEP, BEIJING

  4. Introduction(2) • BES III: • new vertex detector • new MDC • new TOF • new EMC(barrel BGO endcap CsI) • superconducting magnet • new muon counter • new FEE for all subdetectors BESIII Workshop, IHEP, BEIJING

  5. A NEW TRIGGER SYSTEM MUST BE DESIGNED ! BESIII Workshop, IHEP, BEIJING

  6. Estimation of event rate • Good physics events(J/,  at BEPCII/BESIII) • Bhabha and radiative Bhabha scattering • Machine background • Coulomb scattering, Bremsstrahlung with residual gas • Touscheck scattering • Cosmic Ray background • Purpose: • To accept all interested events • To rejects as much background as possible BESIII Workshop, IHEP, BEIJING

  7. Background from Lost particles BESIII Workshop, IHEP, BEIJING

  8. Background from Lost particles BESIII Workshop, IHEP, BEIJING

  9. Machine background Intensity: IBEPCII = (1.1+1.1) A, ( 1.1  1013 e ) ( 40  IBEPC) Lifetime: BEPCII = 3.5~3.8 hr (0.5  BEPC) Lost rate: (dn/dt) BEPCII = 8.7  108/s (80  dn/dt BEPC) Lost rate(BESIII): (dn/dt) BESIII  1.3  107 /s  N beam-BEPCII = 13MHz (80 N beam-BEPC) BESIII Workshop, IHEP, BEIJING

  10. BG measurement of MDC in BES2 BESIII Workshop, IHEP, BEIJING

  11. Machine background BEPC/BESII • 15Hz at DAQ • Single wire of 1st layer of MDC BEPCII/BESIII • 30KHz on single MDC wire at R=17cm • 1500 Hz (DAQ) Fig:Backgrounds rate vs beam current BESIII Workshop, IHEP, BEIJING

  12. Cosmic ray background • Flux Beijing=170 m-2 s-1 • N =1500 /s • BESI/II: • T window = 40 ns • 95% suppressed • N cosmic = 1 Hz • BESIII: • No time window • similar geometrical size to BESI/II • Same # of cosmic rays hitting on BESIII • Using Vertex counter • N cosmic = 20 Hz BESIII Workshop, IHEP, BEIJING

  13. Good physics +Bhabha events • Luminosity LBEPCII = 1  1033 cm-2 s-1 • Optimized to J/ and  energy N J/ = 1500 Hz N ´= 420 Hz N BB = £   BB = 550 Hz (| cos |< 0.95) BESIII Workshop, IHEP, BEIJING

  14. Total event rate Total event rate = good event rate + cosmic event rate + bhabha rate + machine background rate = ~ 3000 Hz BESIII Workshop, IHEP, BEIJING

  15. The principle of BESIII trigger • Trigger requirement • no dead time or small total dead time • Flexibility • Constraints from BEPCII • 93 bunches in the ring (8 ns separation) Latch-process-decision mode not possible in 8ns Pipeline must be used in FEE & trigger BESIII Workshop, IHEP, BEIJING

  16. Trigger pipeline • Constraints due to Detectors • Tdrift MDC = 500 ns(C3 H8 + small cell), signals from different collisions mixed together • Trigger pipeline clock: • RF division (fRF=499.8MHz) • 20MHz (fRF/24) • all trigger promitives are processed every 50ns Trigger latency BESIII Workshop, IHEP, BEIJING

  17. The principle of BESIII trigger(2) • Hardware trigger + software filter(L2) • FEE signal splitted: trigger + FEE pipeline • Trigger pipeline clock 20MHz • Level 1(L1): 2.4s • FEE Control Logic checks L1 with pipeline clock • L1 YES: moves pipeline data to readout buffer • L1 No: • overwritten by new data Time Reference Detector 0 s FEE pipeline Level 1 2.4s Readout buffer switch Ev.Filter Farms (L2) Disk BESIII FEE pipeline and Data flow BESIII Workshop, IHEP, BEIJING

  18. Schematic of BES III Trigger VC DISC Hit Count L0 trigger Logic FEE L0P TOF DISC Hit/Seg Count Global Trigger Logic MDC DISC Track Seg. Finder Track Finder DAQ EMC BTE Sum Tile Sum Tile Processor Total Ener Sum L1P MU DISC Mu track CLOCK RF TTC 2.4 s BESIII Workshop, IHEP, BEIJING

  19. Subsystem Description • MDC Trigger • EMC Trigger • Trigger Timing and Control • Global Trigger Logic BESIII Workshop, IHEP, BEIJING

  20. Trigger for MDC • MDC: • 5740 wires, • 36 layers in 9 super-layers • 6 stereo superlayers • 3 axial superlayers • Trigger: • Axial superlayers for trigger • PT > 150 MeV • step1: track segment finding • step 2:track-finding BESIII Workshop, IHEP, BEIJING

  21. MDC Tracking • Track Segment Finder • Reference layer: second layer in each super-layers • Segment definition • 3/4 logic in a superlayers • Track segments: • Superlayer 1: 66 • Superlayer 2: 162 • superlayer 3: 192 • superlayer 4 270 • Track finder • Reference Segment: second superlayer (track reference: 162) • Track definition • all 4 segments in 4 superlayers BESIII Workshop, IHEP, BEIJING

  22. Track Segment finding BESIII Workshop, IHEP, BEIJING

  23. MDC track combination MCCalculation • MC • Private code • random P(0.15-1.547GeV), initial angle in phi • B = 1.0 T • Ask for all superlayers with segment hit • combinations for each reference segment ~ 117 • realization with CPLD or FPGA BESIII Workshop, IHEP, BEIJING

  24. EMC(Barrel) trigger • BEMC: • 19360 BGO crystals • 88 rings along Z • 44 rings with 240 crystals(inner) • 44 rings with 200 crystals(outer) BESIII Workshop, IHEP, BEIJING

  25. EMC(Barrel) Trigger TILE:25( )22(z) Z BTE:25cells BTE:30cells Tile:30( )22(z)  • Totoal Energy Trigger: sum of all tile signals thresholds • Segmentation: 8() 4(z) = 32 segments Vthl and Vthh No. Of segments • Event time • Basic Trigger element(BTE): BTE1:FEE sum of 30 cells BTE2:FEE sum of 25 cells • Tile: Tile1:sum of 23 BTE’s Tile2:sum of 23 BTE’s BESIII Workshop, IHEP, BEIJING

  26. BESIII Workshop, IHEP, BEIJING

  27. Trigger Timing and Control(TTC) • fRF= 499.8 MHz • fRF /12  40MHz • FEE TDC clock • fRF/24 20MHz • trigger & FEE pipeline clock BESIII Workshop, IHEP, BEIJING

  28. Global Trigger Logic • Inputs: subdetector primitives • Time adjustment • trigger table • Prescaling of some event types • System Configuration • Trigger data readout BESIII Workshop, IHEP, BEIJING

  29. Summary • Pipeline will be used • Hardware trigger + software filter • Hardware: level 0 + level 1 (L0 is spare signal for FEE) • Latency:L0- 200 ns, L1- 2.4 s • Monte Carlo simulation undergoing • backgrounds • Subsystem trigger scheme • Collaboration domestic and international BESIII Workshop, IHEP, BEIJING

  30. THANK YOU ! WELCOME COLLABORATIONS! BESIII Workshop, IHEP, BEIJING

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