LEPS TPC Electronics

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LEPS TPC Electronics

• ???
• Wen-Chen Chang
• Institute of Physics, Academia Sinica
• 03/30/2001

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TPC inside LEPS Detectors
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Experimental Environments

• ?N??N, ?KN, ?N, ?N....
• Fixed target experiment with forward acceptance.
  Occupancy is low, with at most 4-5 charged tracks
  per event.
• Highest photon flux 10M/sec.
• Triggering rate with 0.1 radiation target 1M
  /sec. (Most of them are ee- events.) The ee-
  events are expected to evade through the central
  pipe of TPC and will not come into the effective
  tracking volume.
• Interaction of hadronic events (total cross
  section 1 mb) 1/1000 of ee- events 1k Hz. 1
  kHz DAQ rate required for recording all hadronic
  events. However, ?N??N rate is 0.01 mb.
• Current DAQ rate is about 100Hz. Improvement will
  be done.

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SPRing-8 Beam Structure

• SPring-8 beam structure width of bunch 25 psec,
  minimum gap of bunch 2 nsec.
• The circumference of the ring 1435.95 m 5000
  ns .
• "24/29 filling" means that the ring is filled
  with bunches with 2 nsec separation for 24/29 of
  the ring like
• lt----------------- one cycle
  ----------------------gt
• 24/29 2ns bunches
  5/29
• http//www.spring8.or.jp/ENGLISH/schedule/2000sche
  dule-e.html.
• The closest beam bunch in time is 2 nsec.

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TPC Mechanical Specification

• Inner radius lt 1.25 cm.
• Outer radius lt 30 cm.
• Maximum drift distance 70 cm.
• Maximum drift time 14 ?sec with drift velocity
  5 cm/?sec.
• Read out channels 95 sensing wires, 1000 pads.
• Geometric size of pads two types(?).
• Separation of sensing wire 4mm.

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Requirement of TPC Electronics

• Determine dE/dx from the charge readout of
  either wires or pads.
• Requirement of spatial resolution
• x,y lt 250 ?m.
• z lt 1 mm.
• Position information
• x(t),y(t) from the x and y of fired sense wires
  and 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.

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TPC Electronic Pre-Amp

• Directly hooked to the endplate of TPC.
• ATLAS TGC ASD Chip
• http//onlax2.kek.jp/sosamu/ASD-PRR.pdf.
• Gain 0.8 V/pC.
• Integration time 16 nsec.
• Pulse lengthen 100 nsec.
• ENC7500 electrons at Cd150 pF.

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TPC Electronic Main-Amp

• For trigger determination.
• Differential signal input.
• Discriminator and Shaper.
• Output pulse width lt 200 ns.
• Gain ??
• Module NIM, CAMAC or on FADC board.
• Output V range 0-2 V.
• DO we need this part?

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TPC Electronic FADC

• Sampling rate 40 MHz 25 nsec ? (by fitting,
  peak determination) 5 nsec 0.25 mm (spatial
  resolution) 20 MHz 50 nsec ? 10 nsec 0.5 mm
  .
• Read-out bit (Nbit) 8-10 bits, depending on the
  charge resolution and identification of low
  momentum K,p by dEdx.
• of Time bins per event 700 bins.
• trigger latency/clock 1 usec/25 nsec 40 bins.
• max drift time/clock 15 usec/25 nsec 600 bins.

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TPC Electronic FADC

• Event Size/per channel 8bit700700 bytes.
• Event Size w/o zero suppression
  0.7KB100020KB(header)720KB0.72MB.
• LEPS DAQ transfer rate 3MB/sec.
• Transfer dead time 0.72/30.24 sec.
• Buffer depth NbitNsliceNevtFiducial.
• Zero-suppression Yes.

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AS Neutrino Exp (Texono)

• Measuring energy loss of neutrinos in CsI crystal
  via PMT.
• Main-Amp (no Pre-Amp)
• Preserving time shape.
• Gain Ki3.2 V/mA, Kv64.
• Vout 0-2.8 V.
• Negative signal input, differential output.
• NIM module, 16 channels/per mod.
• 900 USD/per mod.

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BESII upgrade at IHEP, Bejing (I)

• FADC
• 40 MHz (?22.5 MHZ) 8 bits readout.
• On-board DSP for zero-suppression.
• Single event rate lt 354 Hz.
• Maximum firing rate (2k-3k Hz).
• Spatial resolution 0.5 mm.
• 16-32 channels/ per board.

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BESII upgrade at IHEP, Bejing (II)

• TDC using CERN HPTDC chip.
• Dead time free, high resolution, 32 chan/per
  chip.
• 66 USD/per chip.
• Status and Schedule
• 2-channel test board, done.
• pre-prototype, 09/2001.
• prototype, 12/2001.
• With Main-Amp, summer of 2002.

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Information Needed

• 1. Bombard rate 1K Hz for total hadronic
  events.
• 2. Trigger latency time for making trigger
  decision? lt 1 micro-sec.
• 3. Trigger rate data-taking rate lt 100 Hz (10
  dead time)
• 4. Signal rate per channel how frequent a
  channel fires? 1KHz or more ? This depends on
  track density.
• 5. Signal width from TPC Is it mainly
  determined by the pre-amp? something like a
  couple hundred nsec.
• 6. Maximum drift time 70cm/(5cm/micro-sec) 14
  micro-sec.
• 7. Required time resolution(sigma, in ns)
  contributed by electronics say, less than 1mm,
  1mm/(5cm/micro-sec)20 nsec.
• 8. Required integrated non-linearity for time
  measurement???

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Questions

• 9. Maximum charge value to be measured
  depending on how many electrons will be collected
  and the gain of Pre-amp.
• 10. Required charge resolution contributed by
  electronics less than the single bit of FADC.
• 11. Required integrated non-linearity for charge
  measurement depending on the ADC specification.
• 12. Channel number for time measurement for
  sense wires about 100 channels
• 13. Channel number for charge measurement for
  pad channels about 1000 channels.
• 14. Required on-board pre-processing items?????

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Questions

• 15. Inherent chamber spatial(position)
  resolution we need calculation about the
  diffusion of electron clusters when they drift
  toward the pads. We need the pressure and B field
  strength for the estimation.
• Typical sigma(x,y)100-200 ?m, sigma(z)0.2-1
  mm.
• 16. Electron drift velocity in the TPC gas about
  5 cm/micro-sec
• 17. Allowed dead time 10 dead time?.
• 18. Multi-hit ability for each channelYes,
  because of the spiral motions of low momentum
  tracks.

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Events

• Prof. Imai and Ahn visited AS on
  02/09/2001-02/10/2001. Collaborating plan was
  discussed and finalized.
• AS group will prepare the electronic modules for
  June testing.
• Kyoto and RCNP group will prepare the VME (6U-9U)
  and CAMAC crates.
• The DAQ interface cards are purchased and FADC
  modules, Clock module, Calibration module and
  logic control module are being built.
• Appendix of NSC 2001 proposal is submitted on
  03/19/2001.
• Wen-Chen and Henry will discuss with IHEP group
  on 03/31-04/02.
• IHEP group will send one expert to be stationed
  at AS in this summer.
• Maybe a student from Kyoto group will go to AS
  some time for setting up electronics, DAQ and
  event display for June test.

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Plan and Milestones

• Up to 06/01/2001 construction of TPC mechanical
  parts.
• 06/01/2001-12/31/2001 testing of TPC using
  TEXONO FADC modules and DAQ system.
• 12/31/2001 Construction of prototype of new FADC
  module at IHEP, Bejing.
• 01/01/2002-01/31/2002 Testing of prototype FADC
  module.
• 02/01/2002-04/30/2002 Mass production of new
  FADC modules.
• 05/02/2001-06/30/2002 Delivery of FADC modules
  to Spring-8 and installation.
• 07/02/2001-08/32/2001 Electronics system test.
• 09/01/2001 Data-taking starting at Spring-8.