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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 B.SatyanarayanaDepartment of High Energy PhysicsTata Institute of Fundamental ResearchHomi Bhabha Road, Colaba, Mumbai, 400 005E-mail: bsn@tifr.res.in
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
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
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
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
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
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
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
RPC signal characteristics B.Satyanarayana TIFR, Mumbai September 21, 2007
ICAL detector specifications B.Satyanarayana TIFR, Mumbai September 21, 2007
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
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
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
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
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
Pickup strip characteristics Characteristic impedance Foam based pickup panel Capacitance B.Satyanarayana TIFR, Mumbai September 21, 2007
w h Transmission line impedance Readout strips er Ground plane B.Satyanarayana TIFR, Mumbai September 21, 2007
Impedance versus strip width B.Satyanarayana TIFR, Mumbai September 21, 2007
G-10 based pickup plane B.Satyanarayana TIFR, Mumbai September 21, 2007
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
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
Goodlinearity s t Vs position Test on readout system B.Satyanarayana TIFR, Mumbai September 21, 2007
Preamps for prototype detector HMC based Opamp based B.Satyanarayana TIFR, Mumbai September 21, 2007
B.Satyanarayana TIFR, Mumbai September 21, 2007
Preamplifier pulses on trigger B.Satyanarayana TIFR, Mumbai September 21, 2007
Charge-pulse height plot B.Satyanarayana TIFR, Mumbai September 21, 2007
Pulse height-pulse width plot B.Satyanarayana TIFR, Mumbai September 21, 2007
Charge spectrum of the RPC = 375fC B.Satyanarayana TIFR, Mumbai September 21, 2007
Time spectrum of the RPC t = 1.7nS B.Satyanarayana TIFR, Mumbai September 21, 2007
Charge-timing scatter B.Satyanarayana TIFR, Mumbai September 21, 2007
Decay constant of the preamp output B.Satyanarayana TIFR, Mumbai September 21, 2007
Single/Noise monitoring Time profile Rate distribution B.Satyanarayana TIFR, Mumbai September 21, 2007
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
A readout system concept B.Satyanarayana TIFR, Mumbai September 21, 2007
Typical front-end circuit B.Satyanarayana TIFR, Mumbai September 21, 2007
Various signal profiles B.Satyanarayana TIFR, Mumbai September 21, 2007
Zero-crossing discriminator B.Satyanarayana TIFR, Mumbai September 21, 2007
Discriminator response (Overdrive) B.Satyanarayana TIFR, Mumbai September 21, 2007
Discriminator response B.Satyanarayana TIFR, Mumbai September 21, 2007
Double pulse resolution B.Satyanarayana TIFR, Mumbai September 21, 2007
Output driver B.Satyanarayana TIFR, Mumbai September 21, 2007
Example for a front-end (NINO) Architecture Specifications Input stage B.Satyanarayana TIFR, Mumbai September 21, 2007
24-channel NINO board Calibration B.Satyanarayana TIFR, Mumbai September 21, 2007
Front-end ASIC concept B.Satyanarayana TIFR, Mumbai September 21, 2007
HPTDC architecture B.Satyanarayana TIFR, Mumbai September 21, 2007
HPTDC specifications B.Satyanarayana TIFR, Mumbai September 21, 2007
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
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
A scheme for dark current readout Dark current = Current drawn from negative supply – 3.5A (Current drawn through 1G) B.Satyanarayana TIFR, Mumbai September 21, 2007
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