1. BESIII Electronics and On-Line BESIII Workshop in Beijing IHEP Zhao Jing-wei Sheng Hua-yi He Kang-ling October 13, 2001 Brief Measurement Tasks Technical Strategy Sub-systems Configurations and Software On-Line System

2. Brief BESIII ’ s sub-detectors are: Vertex Chamber Main Drift Chamber TOF plus CCT Counter Electromagnetic Calorimeter MUON Identifier Electronics will consist of five sub-systems correspondingly. Total channel amount is about 50K~77K.

3. Measurement Tasks To measure the time information carried by detector signal. To measure the charge values carried by detector output signals or signal amplitude. To deliver the information of fired point position (x,y) in detector cells. To provide the hit information or sum of analog signals for making trigger decision. To implement data taking and data formatting and preprocessing and sub-event packing. To transfer the packed data to On-line computer system via fast switch network.

4. Technical Strategy Short bunch crossing (8 ns) Long trigger latency (2.4us)  pipeline must be used. High luminosity (1×10 33 cm -2 s -1 ). High event rate.  Parallel processing on-board is needed to make dead time as small as possible.

5. Technical Strategy High beam intensity (1100 mA×2) Short lifetime (3-4 hours) Bad noise environment  Measures must be taken to make system immune from noise background and RF interference. Weak signal, especially for VC, EMC and MDC.  low noise technique must be adopted.

6. Sub-system MDC Tasks Tasks & technical requirements The charge deposition on sense wire (dE/dx) Charge range : 8~1500 fc Resolution: σ Q ≈ 4 fc The drift time of ionized electrons towards sense wires. (to determine the spatial trajectory of particles and the momentum of particles.) Time range : 0~500ns Resolution :σt ≈ 0.5ns Hit information to trigger

7. Sub-system MDC Scheme 1 Based on “ Q to T converter + HPTDC ” Wire signal trigger Online VMEbus Q to T based mainamp Calibration CERN HPTDC based TDC Preamp

8. Sub-system MDC Scheme 1 Preamp. A transimpedance type Low noise Low power dissipation Main amp. Based on Q to T converter – MQT300A TDC module Adopt CERN HPTDC as a key component. Advantage for above scheme: Simple system: Use only TDC to measure both the time and charge.

9. Sub-system MDC Scheme 2 Based on “ FADC and HPTDC ” VMEbus Clock online Preamp Trigger Start Wire Signal Q measurement T measurement Calibration Mainamp Trigger Timing dE/dX V th

10. Sub-system MDC Scheme 2 Charge measurement is based on FADC waveform sampling & Numerical integral. 10bit and 40MHz FADC is required. 9U VME board and 32 ch./board Time measurement is based on CERN HPTDC chip 9U VME board and 96 or 128 ch./board

11. Sub-system VC Charge information Range = 0.22 fc on average σQ ≤ 20% at 0.22fc Ch. = 300 Hit information to trigger

12. Sub-system EmC Tasks Charge measurement Range : 0.2 fc to 300 fc Resolution :  q = 0.1 fc

13. Sub-system EmC Block diagram Trigger Post amplifier VMEVME Trigger L1 CTrigger CL1 Trigger L1 CR (RC 2 ) ∑ calibration Fan - out Charge measurement controller Σ BGOBGO ∑ Preamplifier

14. Sub-system EmC Brief introduction 20200 BGO crystals Charge-sensitive preamplifier to receive the signal from photodiode 20MHz FADC to digitize the waveform 15 bit dynamic range is needed. 10 bit resolution is required.

15. Sub-system EmC Scheme Preamplifiers are mounted on the BGO crystals. Two signals from each crystal are added together, and then feeds to post-amplifier for further amplifying and shaping. FADC samples the signal with 20MHz. The data are pushed to the digital pipeline. The length of the pipeline equals the trigger L1 latency. Digitized data within 1.5s interval are read out by a peak finding circuit on arrival of trigger L1. The peak value is stored in a buffer for readout by VME. Auto Range Encode Circuits are employed to expand the FADC dynamic range from 10 bits to 15 bits.

16. Sub-system TOF Tasks To provide the information for particle identification by measuring the flight time of the particles. To correct the flight time by measuring the charge. To provide hit information to trigger

17. Sub-system TOF Requirement Time measurement Number of channels: 320 Range : 0~60ns Resolution : σt ≤25ps Charge measurement Number of channels : 320 Dynamic range : 2Vmax for TOF 0.2Vmax for CCT Resolution : 2% at 2V for TOF 2% at 0.2V for CCT

18. Sub-system TOF Block Diagram Start 10ns L-threshold H-threshold L0 trigger From Online To Trigger Pre-amp Splitter Stop Signal Driver HL Calibration LL delay Trigger L1 Q Read-out T

19. Sub-system TOF Charge measurement The circuitry consists of the Voltage-to- Current converter,integrator, FADC and two FIFOs. VME BUS W R W 40MHz CLK V/I FADC Peak- finding FIFO Trigger L1

20. Sub-system TOF Time measurement TOF time measurement schema is based on TAC plus FADC. CLK 40M L0 200ns Delay vcc _ + S !Q R Q Temp control STOP TAC START FADC

21. Sub-system Muon Tasks Tasks & technical requirements To deliver the information of fired point position(x,y) in detector cells. The hit information to trigger

22. Sub-system Muon Configuration Configuration Modules of VME 7 Chains in a module 24 Data of a chain 256 Total data of readout system 10K~30K

23. Sub-system Muon Diagram of chain

24. Sub-system Muon Diagram of VME

25. Configuration and Software Tasks DAQ L1 Event Rate ≈ 3000Hz Event Length ≈ 6K~10K Byte Read Out Tasks: protocols & communications system control data taking Preprocessing transmission 50K~77K channels will be read out and preprocessed and sent out reduce the “ dead-time ” in data taking from read out electronics avoid “ bottle-neck ” of data flow

26. Configuration and Software Structure branch 1branch n

27. Configuration and Software Device Read-Out Crate VME Crate + ADC/TDC modules + Processor There are ~600 channels in each read out crate. ~90 VME crates will be needed. Branch Computer (Multi-CPU) + Switch( 100M) + Crates Multi-Port network card will be used to the computer. One port is linked to the online computer system via a Gigabit switch, others are linked with the processors of Read-Out Crates via 100M switch. There are 1~6 VME Read Out Crates per branch. There are >16 branches in BESIII read out electronics system.

28. Configuration and Software Design Consideration Adopt Commercial Product PowerPC 、 100M Switch 、 Computer and others Consider to adopt new technique and future device Performance/cost ratio The software developing environment VxWorks and x86 BSP 、 PowerPC750 BSP

29. On-Line System Tasks Event rate ~2000Hz after L2 filter ~16MBytes/sec to persistent store Event Builder System Transport information from readout crate to Online(L2) farm L2 trigger System Software trigger. Selects events for storage Online System Run environment monitoring and controlling Experiment monitoring and controlling Human interface

30. On-Line System Tasks Data Storage mass storage and transmission via fast network Slow control system HV control and monitoring Environmental monitoring Dead time & Luminosity monitoring Tests

31. On-Line System Requirements High performance computer Graphics User Interface to experiment Functional requirement Configuration and constants of system Execute command to FEE and Farm nodes Error message reports for FEE and Farm nodes Calibration Support Diagnostic Tools Data Monitoring Support Database and network support

32. Thanks!