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Possible schemes for ICAL electronics

Possible schemes for ICAL electronics. B.Satyanarayana Department of High Energy Physics Tata Institute of Fundamental Research Homi Bhabha Road, Colaba, Mumbai, 400 005 E-mail: bsn@tifr.res.in. Plan of the presentation. Characterisation of RPC pulses ICAL detector requirements

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Possible schemes for ICAL electronics

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  1. Possible schemes for ICAL electronics B.SatyanarayanaDepartment of High Energy PhysicsTata Institute of Fundamental ResearchHomi Bhabha Road, Colaba, Mumbai, 400 005E-mail: bsn@tifr.res.in

  2. Plan of the presentation • Characterisation of RPC pulses • ICAL detector requirements • Front-ends currently in use • RPC pulse profile studies • Possible schemes for the ICAL detector • Control and monitoring systems • Summary B.Satyanarayana TIFR, Mumbai September 21, 2007

  3. Resistive plate Resistive plate Resistive plate Principle of operation of RPC Charge depletion induces signal. Charge depletion fixed by geometry, resistivity, gas. Dielectric ++++++++++++++++ +++++ + + +++++ +++++ +++++ Region recharges on scale of up to sec due to bulk resistivity (1011Wcm) Streamer forms, depletes charge over (1-10mm2). Field drop quenches streamer HV HV HV Ionization leads to avalanche ----- ----- Gas ----- - - ---- B.Satyanarayana TIFR, Mumbai September 21, 2007

  4. RPC signal generation • A passing ionising particle will liberate N0 electrons, creating an initial current, i0=eN0v/g, that depends on the electron’s drift velocity v and on the width g of the gas gap. • The gas avalanche process will immediately amplify the initial current in time as i=i0esth(t), where s is a real positive parameter and h(t) the unit step function. • The exponential multiplication factor may reach very large value, up to 108. The output voltage signal is given by v(t)=i0Z(s)est B.Satyanarayana TIFR, Mumbai September 21, 2007

  5. RPC signal characteristics For a given threshold setting, time deference should be independent of i0 (which fluctuates event by event) and independent of the circuit properties (represented by Z(s)) B.Satyanarayana TIFR, Mumbai September 21, 2007

  6. Important conclusions • The nature of the detector electrodes, coupling lines, amplifiers, etc, will affect only the magnitude of the output signal through the combined transimpedance Z(s), while leaving unaffected the time development of the signal. • The signal shape (exponential) will be influenced only by the value of s, determined by the gas avalanche process in the detector. B.Satyanarayana TIFR, Mumbai September 21, 2007

  7. RPC mode definitions Let, n0 = No. of electrons in a cluster  = Townsend coefficient (No. of ionisations per unit length  = Attachment coefficient (No. of electrons captured by the gas per unit length Then, the no. of electrons reaching the anode, n = n0e(- )x Where x = Distance between anode and the point where the cluster is produced • Gain of the detector, M = n / n0 • M decides the mode of RPC operation • M > 108  Streamer mode; • M << 108  Avalanche (Proportional mode) B.Satyanarayana TIFR, Mumbai September 21, 2007

  8. RPC mode definitions • A planar detector with resistive electrodes • ≈ Set of independent discharge cells • Expression for the capacitance of a planar condenser  Area of such cells is proportional to the total average charge, Q that is produced in the gas gap. Induced charge is only ~5% of the total charge collected by the anode Where, d = gap thickness V = Voltage applied to the electrodes 0 = Dielectric constant of the gas Lower the Q, Lower the area of the cell (that is ‘dead’ during a hit) and hence higher the rate handling capability of the RPC Q ~ 100pC = Streamer mode Q ~ 1pC = Proportional (Avalanche) mode B.Satyanarayana TIFR, Mumbai September 21, 2007

  9. RPC signal characteristics B.Satyanarayana TIFR, Mumbai September 21, 2007

  10. ICAL detector specifications B.Satyanarayana TIFR, Mumbai September 21, 2007

  11. What is specific for ICAL DAQ? • Large number of data channels to handle; large scale integration needed. • But, fewer and simpler parameters to record • Low rates; high degree of multiplexing possible • Monolithic detector; unlike the case accelerator based detectors • ASICs, pipelining, trigger farm,VME are the keywords • ASICs for front-end, timing, even for trigger! B.Satyanarayana TIFR, Mumbai September 21, 2007

  12. Recordable parameters (Detectors) • Event data • Strip hit information (Boolean, 1 bit per strip) • Strip signal timing with reference to event trigger • Strips ORed to reduce timing channels • Monitor data • Strip single/noise counting rate • Chamber voltage and current B.Satyanarayana TIFR, Mumbai September 21, 2007

  13. Recordable parameters (DAQ) • Preamplifier gain and input offset • Discriminator threshold and pulse width • Trigger logic parameters and tables • DAQ system parameters • Controllers and computers’ status B.Satyanarayana TIFR, Mumbai September 21, 2007

  14. Recordable parameters (Gas system) • Open loop versus closed loop systems • Gas flow via Mass Flow Controllers • Exhaust gas flow monitor • Residual gas analyser data • Gas contaminants’ monitor data • Gas leak detectors • Safety bubblers’ status B.Satyanarayana TIFR, Mumbai September 21, 2007

  15. Recordable parameters (Ambient) • Temperature • Gas • Front-end electronics • Barometric pressure • Gas • Relative humidity • Dark currents of the bias supplies • Electronics B.Satyanarayana TIFR, Mumbai September 21, 2007

  16. Pickup strip characteristics Characteristic impedance Foam based pickup panel Capacitance B.Satyanarayana TIFR, Mumbai September 21, 2007

  17. w h Transmission line impedance Readout strips er Ground plane B.Satyanarayana TIFR, Mumbai September 21, 2007

  18. Impedance versus strip width B.Satyanarayana TIFR, Mumbai September 21, 2007

  19. G-10 based pickup plane B.Satyanarayana TIFR, Mumbai September 21, 2007

  20. 14.5 m m Tests on signal pickup schemes Adjoining strip Central strip Adjoining strip Dt The cross talk on the adjoining strips, after the signal propagation along the 15 m long FCS, is very small m Attenuation = 0.052 db/m t = Propagation constant = 5.6 ns/m B.Satyanarayana TIFR, Mumbai September 21, 2007

  21. Test on readout system The time performance of the X-system, of the order of 100 ps, shows that 15 m long FCS can be used without a worsening of the intrinsic time resolution of the Glass RPC (~1 ns). Even the Y-coordinate can be measured with a resolution of the order of 1 cm by a Δt measurement Raw data resolution = 2.4 cm. After subtracting quadratically the broadening due to the scintillator width σX (cm) = 1.23 cm sx (cm) = 2.st.t = 11.2 .st(ns) B.Satyanarayana TIFR, Mumbai September 21, 2007

  22. Goodlinearity s t Vs position Test on readout system B.Satyanarayana TIFR, Mumbai September 21, 2007

  23. Preamps for prototype detector HMC based Opamp based B.Satyanarayana TIFR, Mumbai September 21, 2007

  24. B.Satyanarayana TIFR, Mumbai September 21, 2007

  25. Preamplifier pulses on trigger B.Satyanarayana TIFR, Mumbai September 21, 2007

  26. Charge-pulse height plot B.Satyanarayana TIFR, Mumbai September 21, 2007

  27. Pulse height-pulse width plot B.Satyanarayana TIFR, Mumbai September 21, 2007

  28. Charge spectrum of the RPC  = 375fC B.Satyanarayana TIFR, Mumbai September 21, 2007

  29. Time spectrum of the RPC t = 1.7nS B.Satyanarayana TIFR, Mumbai September 21, 2007

  30. Charge-timing scatter B.Satyanarayana TIFR, Mumbai September 21, 2007

  31. Decay constant of the preamp output B.Satyanarayana TIFR, Mumbai September 21, 2007

  32. Single/Noise monitoring Time profile Rate distribution B.Satyanarayana TIFR, Mumbai September 21, 2007

  33. Major sub-systems • Analog and digital front-ends • Mounted on or very close to detectors • Programmable preamps and comparators • Latches, pre-trigger generators, pipelines and buffers • Data concentrators and high speed serial transmitters • VME back-ends • Data collectors and frame transmitters • Time to digital converters (TDCs) • Trigger system • Works on inputs from front-ends, back-ends or external • Place for high density FPGA devices B.Satyanarayana TIFR, Mumbai September 21, 2007

  34. A readout system concept B.Satyanarayana TIFR, Mumbai September 21, 2007

  35. Typical front-end circuit B.Satyanarayana TIFR, Mumbai September 21, 2007

  36. Various signal profiles B.Satyanarayana TIFR, Mumbai September 21, 2007

  37. Zero-crossing discriminator B.Satyanarayana TIFR, Mumbai September 21, 2007

  38. Discriminator response (Overdrive) B.Satyanarayana TIFR, Mumbai September 21, 2007

  39. Discriminator response B.Satyanarayana TIFR, Mumbai September 21, 2007

  40. Double pulse resolution B.Satyanarayana TIFR, Mumbai September 21, 2007

  41. Output driver B.Satyanarayana TIFR, Mumbai September 21, 2007

  42. Example for a front-end (NINO) Architecture Specifications Input stage B.Satyanarayana TIFR, Mumbai September 21, 2007

  43. 24-channel NINO board Calibration B.Satyanarayana TIFR, Mumbai September 21, 2007

  44. Front-end ASIC concept B.Satyanarayana TIFR, Mumbai September 21, 2007

  45. HPTDC architecture B.Satyanarayana TIFR, Mumbai September 21, 2007

  46. HPTDC specifications B.Satyanarayana TIFR, Mumbai September 21, 2007

  47. Control and monitoring systems • Front-end, DAQ and trigger system control and monitoring • Front-end gain, threshold, pulse width • Trigger tables etc • High voltage control and monitoring • Gas system control and monitoring • Ambient parameter monitoring • Temperature, barometric pressure, relative humidity • Data can be used for even for off-line corrections B.Satyanarayana TIFR, Mumbai September 21, 2007

  48. High voltage system control and monitoring • Number of independently controllable channels? • Worst case • Combine all RPCs in a layer  140 channels • Best case • One channel per RPC  26,880 channels! • We can settle for one channel/road/layer, for example • Ramp rate, channel control, voltage and current monitoring are the bare minimum requirements • Modular structure, Ethernet interface, local consoles, distributed displays, complete high voltage discharge etc are most desired features B.Satyanarayana TIFR, Mumbai September 21, 2007

  49. A scheme for dark current readout Dark current = Current drawn from negative supply – 3.5A (Current drawn through 1G) B.Satyanarayana TIFR, Mumbai September 21, 2007

  50. Gas system control and monitoring • Channel control and flow monitoring • On-line gas sample analysis (RGA) • Gas leak monitoring • Moister level monitoring B.Satyanarayana TIFR, Mumbai September 21, 2007

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