Working Principles of Time Projection Chamber 1.Passage of charged particles through the gas generates ionization electrons. 2.Electrons drift towards the readout plane along the imposed E x B drifting fields. 3.At the end of readout plane, an avalanche (amplification) will happen upon the arrival of electrons by the proportional sense wires and an induced image charge on the corresponding cathode pads. 4.The pads are connected with a read-out electronics which provides low-noise and high resolution analogue information as well as the drift time associated with the signal.
Electric Field Configuration Grid Wire Sense Wire Field Wires Cathod
View of Particle Trajectory along the beam in Simulation
TPC Mechanical Specification Inner radius: < 1.25 cm. Outer radius: < 30 cm. Read out channels: 95 sensing wires, 1000 pads. Pad size:inner 8mm*8mm, outer 8mm*13mm. Distance between sensing wires and pads: 4mm. Separation of sensing wire: 4mm. Cathode readout. Maximum drift distance : about 70 cm. Maximum drift time: about 14 sec with drift velocity = 5.1 cm/ sec.
Requirement of TPC Electronics Good energy resolution: measuring dE/dx from the charge readout of either wires or pads for the particle identification for K/p separation at low momentum. Requirement of spatial resolution: –x,y < 300 m. –z < 1 mm. Position information: –x(t),y(t): x from fired sense wires; y from interpolation of signals on pads(t). –z(t) from time bin of FADC time slice. Timing information: fitting of pulse peak in FADC. On-board zero-suppression to ensure fast data transfer and short system dead time.
Digitizer in TPC Electronic: FADC Large data size: –High sampling rate: 40 MHz = 25 nsec. –Read-out bit (Nbit): 10 bits. –# of Time bins per event: ~600 time bins. (Max drift time/clock = 14 sec/25 nsec = 560 bins.) –1000 channels. Trigger latency: 1 sec. On-board zero-suppression. Need of a large buffer size to store 4-5 events on board for one single VME readout.(16*600*5=48K per channel, w/o a zero suppression factor.) High channel density.
SPring-8 FADC Module –Use TEXONO FADC and IHEP BES version as the starting point. –40 MHz; 10-bit FADC: input 0-2 V range. –Shift register inside FPGA: length = trigger latency (1 s). –On-board FPGA for threshold suppression. –Buffer FIFO: dual port memory. –CPLD: controlling VME actions. –Free clock running. –VME 9U; 32 channels/module; 8 attached cards/module; 4 channel/card.
Main Electronic Components Receiver: MAXIM, MAX4145ESD. OPA: Analog Device, AD8138ARSO-8. FADC: Analog Device, AD9203ARVRU- 28. FPGA: Xilinx, XC2S150-6FG456. FIFO: TI, SN74V245.
40 MHz sampling rate. 10 bits resolution with 2Vp-p dynamic range. Clock distribution with Phase Lock Loop circuit. On Board digital signal delay and Real-Time ZERO-Suppression. High capacity First In First Out Memory. Easy to use with high density connector. Mixed signal AD Converter Adapter Board
FPGA, digital signal control chip. First In First Out memory. VMEBus slave controller, with high performance BLTransfer Mode. 32 Channels, high sampling rate Flash AD converter. Differential AD Converter (40 MHz) 16 channels differential signal input connector. Spring-8 2002/03
Receiver & Driver FADC Differential Signal from MAMP 10 Hit Flag FIFO Processing FPGA Clock Trigger Receiver & Driver FADC 10 Receiver & Driver FADC 10 Receiver & Driver FADC 10 CH 1 CH 4 CH 3 CH 2 x 8 Four Channels VA[8..23] Trigger Counter Trigger FIFO VME Control 12 Delay Write VME_Reset Check Trigger Number Clear Trigger FIFO Read Trigger FIFO VD[0..11] x 8 ReadRST Read Flag Write Flag Global FPGA JTAG VD[0..31] VA[8..15] 4 Flag Reset Download PROM VD1 VA1 VC AS,D0,D1,AM[0..5],Write,DTACK, et. al. 8 bits DIP Switch 8 Write_in Read_out Download PROM
Shift Register 10 bits Data Threshold Comparator 32 bits FIFO 10 Trigger Clock Counter & Control Enable Clock Over_Threshold Comp_Control Write_header&trailer Clock Rst Reset VD[0…15] VA[8…15] Read Write Enable Write DisableClear Count Write_Data Write_Flag Read Write Flag S R Q Flag 10 L=(Trigger Latency + 1) VA2 VD2 Fig. 2 Block Diagram of Processing FPGA Clock
Data Format 16151413121110090807060504030201 CS001NDFADC Module Number (1-64)Channel Number (1-32) CS010ND ADC (0-1024) CS100ND Number of ADC data bins (0-600) CS011ND Time (0-1024) Header 1 ADC Time Trailer CS: Checksum bit ND: Not defined. Lowest Bit CS001NDEvent Number (1-5) Header 2
CSR Format 16151413121110090807060504030201 Reset Sampling Count: default value 1020. VME address: 0x010000 Lowest Bit 1 1 00 Last six digits of number of sampling count.
FADC VME Action List (A24/D16) 0x0i0000: address to write, bit 9 for resetting FIFO and set ready, bit 10 for resetting suppression threshold and bit 11 for setting the sample count of the FADC i. (Address modifier: 0x3D). 0x0i0100: address to read the merged 32 FIFOs’ content in BLT mode for FADC i. (Address modifier: 0x3B, 0x3F). 0x0i0101: address to read the BLT reading cycle for FADC i. (Address modifier: 0x3B, 0x3F). 0x0i0000+j*0x000100: address to read the single FIFO content in AO mode for channel j. (Address modifier: 0x3D) 0x0i0000+j*0x000100: address to write for setting the zero- suppression threshold for channel j. (Address modifier: 0x3D)
The Control Flow of FADC < 5 events Send IRQ to VME CPU DAQ READ FIFO DAQ send Reset FADC clear BUSY Clear trigger Veto Yes No DAQ Start Trigger Count *Veto NIM CPLD FADC Trigger Clock 100MHz Trigger signal Trigger FADC Busy FADC Module Preamplifier Module For each channel VME CPU Reset Master Slave Trigger, Conversion
Observation Window of Signals Signal Trigger Conversion Strobe Sampling Counts ( max 1024*25ns=25 s) Shift Register Length ( max 100*25ns = 2.5 s)
Events 02/09/2001: Prof. Imai and Ahn visited AS. Collaborating plan was discussed and finalized. 03/31/2001: Wen-Chen and Henry visited IHEP, Beijing and explored the R&D plan in IHEP. 05/31/2001: IHEP was not able to perform the R&D plan. 08/01/2001: Da-Shun visited IHEP for 3 weeks to learn the conceptual design. 02/01/2002: Prototype 1 boards made. 02/28/2002: Wen-Chen and Da-Shun tested prototype-1 boards with TPC at SPring-8. 04/25/2002: Finished up 64 channels of prototype-1 and deliver them to SPring-8.
Plan 04/30/2002: Issue out prototype-2 (quasi-final) fabrication order. 05/21/2002: Deliver prototype-2 to SPring-8. 06/01/2002: System test with a complete electronic chain (Pre-amp, shaper, and FADC) with TPC and Solenoid magnet. 06/15/2002: Issue out final production fabrication order (1440 channels). 07/01/2002: Send production boards for stuffing. 07/15/2002 – 07/31/2002: Test production boards. 08/01/2002 – 08/31/2002: Delivery of production board, installation, system test and DAQ. 09/15/2002: Commission Run with photon beam.
Remarks Many valuable experiences learned: board design, firmware, modification of TEXONO DAQ, coordinating people, etc. A good starting point for a continuing “rooting” process of experimental technique at IPAS. Thanks to many people: Henry, P.K., A.C., K.C., Tracy, IHEP group….