Transcript INO TRIDAS activities at Mumbai

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: [email protected]
Plan of the presentation
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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
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Principle of operation of RPC
Charge depletion induces signal. Charge
depletion fixed by geometry, resistivity, gas.
Dielectric
HV
Resistive plate
Resistive plate
Resistive plate
++++++++++++++++
+++++
+++++ + + +++++
Ionization leads
to avalanche
Gas
B.Satyanarayana
HV
-----
+++++
Streamer forms,
depletes charge over
(1-10mm2). Field drop
quenches streamer
-----
TIFR, Mumbai
HV
Region recharges on
scale of up to sec due to
bulk resistivity
(1011Wcm)
----- - - ----
September 21, 2007
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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
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RPC signal characteristics
Th1  v0 ( s) exp(st1 )
Th2  v0 ( s) exp(st 2 )
ln(Th1 / Th2 )  s(t1 - t2 )
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
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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
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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
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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
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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.
Qd
S
 0V
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
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TIFR, Mumbai
September 21, 2007
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RPC signal characteristics
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TIFR, Mumbai
September 21, 2007
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ICAL detector specifications
No. of modules
Module dimensions
Detector dimensions
No. of layers
Iron plate thickness
Gap for RPC trays
Magnetic field
RPC dimensions
Readout strip width
No. of RPCs/Road/Layer
No. of Roads/Layer/Module
No. of RPC units/Layer
No. of RPC units
No. of readout channels
B.Satyanarayana
3
16 m X 16 m X 12 m
48 m X 16 m X 12 m
140
6 cm
2.5 cm
1.3 Tesla
2mX2m
3 cm
8
8
192
26880
3.6 X 106
TIFR, Mumbai
September 21, 2007
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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
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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
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TIFR, Mumbai
September 21, 2007
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Recordable parameters (DAQ)
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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
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Recordable parameters (Gas system)
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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
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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
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Pickup strip characteristics
Characteristic impedance
Foam based pickup panel
B.Satyanarayana
TIFR, Mumbai
Capacitance
September 21, 2007
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Transmission line impedance
Readout strips
w
r
h
Ground plane
 r 1  r -1
x  w / h  r '  2  2 1  10 x 
-
1
2
60 x ln( 8/x  x/4)
: x 1
r '
377
Z
: x 1
 r ' ( x  1.393 0.667ln(x  1.444))
Z
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TIFR, Mumbai
September 21, 2007
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Impedance versus strip width
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TIFR, Mumbai
September 21, 2007
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G-10 based pickup plane
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TIFR, Mumbai
September 21, 2007
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Tests on signal pickup schemes
Adjoining strip
Central strip
Adjoining strip
Dt
14.5 m
m
Attenuation = 0.052 db/m
t = Propagation constant = 5.6 ns/m
B.Satyanarayana
TIFR, Mumbai
m
The cross talk on the
adjoining strips,
after the signal
propagation along
the 15 m long FCS, is
very small
September 21, 2007
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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
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Test on readout system
Good linearity
s t Vs position
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TIFR, Mumbai
September 21, 2007
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Preamps for prototype detector
HMC based
B.Satyanarayana
Opamp based
TIFR, Mumbai
September 21, 2007
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B.Satyanarayana
TIFR, Mumbai
September 21, 2007
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Preamplifier pulses on trigger
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TIFR, Mumbai
September 21, 2007
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Charge-pulse height plot
0
60
80
100
120
140
160
180
-20
y = -1.8814x + 128.03
Pulse height, mV
-40
-60
-80
-100
-120
-140
-160
9.9KV
10.0KV
9.5KV
Linear (9.9KV)
-180
Charge, QDC bins
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TIFR, Mumbai
September 21, 2007
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Pulse height-pulse width plot
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Pulse width, Bins
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12
10
8
6
4
2
9.9KV
10.0KV
9.5KV
0
-180
-160
-140
-120
-100
-80
-60
-40
-20
0
Pulse height, mV
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TIFR, Mumbai
September 21, 2007
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Charge spectrum of the RPC
m = 375fC
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TIFR, Mumbai
September 21, 2007
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Time spectrum of the RPC
st = 1.7nS
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TIFR, Mumbai
September 21, 2007
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Charge-timing scatter
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TIFR, Mumbai
September 21, 2007
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Decay constant of the preamp output
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TIFR, Mumbai
September 21, 2007
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Single/Noise monitoring
Time profile
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Rate distribution
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September 21, 2007
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Major sub-systems
• Analog and digital front-ends
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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
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TIFR, Mumbai
September 21, 2007
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A readout system concept
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TIFR, Mumbai
September 21, 2007
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Typical front-end circuit
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TIFR, Mumbai
September 21, 2007
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Various signal profiles
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TIFR, Mumbai
September 21, 2007
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Zero-crossing discriminator
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TIFR, Mumbai
September 21, 2007
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Discriminator response (Overdrive)
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TIFR, Mumbai
September 21, 2007
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Discriminator response
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TIFR, Mumbai
September 21, 2007
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Double pulse resolution
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TIFR, Mumbai
September 21, 2007
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Output driver
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TIFR, Mumbai
September 21, 2007
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Example for a front-end (NINO)
Architecture
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Specifications
Input stage
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September 21, 2007
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24-channel NINO board
Calibration
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TIFR, Mumbai
September 21, 2007
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Front-end ASIC concept
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TIFR, Mumbai
September 21, 2007
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HPTDC architecture
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TIFR, Mumbai
September 21, 2007
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HPTDC specifications
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TIFR, Mumbai
September 21, 2007
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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
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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
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A scheme for dark current readout
Dark current = Current drawn from negative supply –
3.5mA (Current drawn through 1GW)
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TIFR, Mumbai
September 21, 2007
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Gas system control and monitoring
• Channel
control and
flow
monitoring
• On-line gas
sample
analysis (RGA)
• Gas leak
monitoring
• Moister level
monitoring
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TIFR, Mumbai
September 21, 2007
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On-line data browsers
• Web servers for operating parameter browsers
– Java applets
• On-fly sample data quality checks
– Interactive/configurable tools
• Remote access
– Graded/filtered data, security issues
B.Satyanarayana
TIFR, Mumbai
September 21, 2007
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Some technology standards
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Backend: VME
OS platform: Linux
Networking of processing nodes
Front-end, gas system and HV control
– Ethernet
• Ambient parameter monitoring
– Embedded processors with Ethernet interfaces
• Data bases
– Scientific versus commercial
– Presets, event, monitor data
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TIFR, Mumbai
September 21, 2007
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Summary
• RPC’s pulse characteristics and ICAL’s requirements understood
to a large extent; more will be known from the prototype detector
• Time to formulate competitive schemes for electronics, data
acquisition, trigger, control, monitor, on-line software, databases
and other systems
• A couple of best options could be selected for detailing.
• Feasibility R&D studies on front-ends, timing elements, trigger
architectures, on-line data handling schemes should be
concurrently taken up
• Power budgets, integration issues etc. must be addressed
• Procurement of design and simulation tools
• Design teams/centres and industry structure and coordination
• Preparation of Engineering Design Report (EDR) and Technical
Design Report (TDR)
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TIFR, Mumbai
September 21, 2007
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