Minni Singla* 1 , Sudeep Chatterji 2 , V.Kleipa 2 , W.F.J.Mueller 2 and J.M.Heuser 2
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Transcript of Minni Singla* 1 , Sudeep Chatterji 2 , V.Kleipa 2 , W.F.J.Mueller 2 and J.M.Heuser 2
Minni Singla*1, Sudeep Chatterji2, V.Kleipa2, W.F.J.Mueller2 and J.M.Heuser2
1Goethe University, Frankfurt2GSI, Darmstadt
IEEE Nuclear Science Symposium 201231st Oct. 2012 1
DipoleMagnet
The Compressed Baryonic Matter Experiment
Ring ImagingCherenkovDetector
Transition Radiation Detectors
ResistivePlate Chambers(TOF)
Electro-magneticCalorimeter
SiliconTrackingStations
Tracking Detector
Muondetection System
Projectile SpectatorDetector(Calorimeter)
VertexDetector
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• Central 25A GeV Au+Au collision overlaid with GEANT simulation• 10MHz interaction rate• Up to 700 charged particles/evt• Track densities up to 30 cm-2/ evt
10MHz interaction rate Fast electronicsMinimize multiple scattering Low material budgetExpected Fluence 1014 neqcm-2 Radiation hard sensors
Technological Challenges
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To develop low-mass, low noise system of rad-hard DSSDs and signal transmission line
Double Sided silicon Strip Detectors Radiation hard DSSDs tolerant up to 1014 neq cm-2
Loss of Charge Collection efficiency with fluence Any increase in Capacitive/Resistive Noise? Continuous need of increased operating voltage limited by breakdown Comparison of various Isolation techniques to optimize DSSDs
performance Readout cables
Low material budget Minimize ENC Comparison of various designs in this direction Expected transmission losses
Motivation
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Layout of sensor module
MODULE
AC coupled Double Sided Senors by CiS, Erfurt Germany p+ strips on n-type bulk n+ strips with p-stop, p-spray, schottky metal Orthogonal strips Sensor thickness: 300 m
With Hamamatsu, Japan (in preparation)
CABLECABLE
FEE
SENSORS
SE
CT
OR
Series Capacitive Noise (ENCc) C tot => Total capacitance (sensor+cable) a + b×C tot e- R s => Series resistance (sensor+cable) τ => Shaping time Series Resistive Noise (ENCRs) I => Leakage Current 24×Ctot (pF) ×√{Rs (Ω) / τ (ns)} e- R s => Parallel resistance
Shot Noise (ENCI) 108×√{I(μA).τ(ns)} e-
Parallel Resistive Noise (ENCRp) 24×√{τ (ns)/ Rp(MΩ)} e-
(ENCtot)2 = (ENCc)2+(ENCRs)2+(ENCI)2+(ENCRp)2
Ref.: C. Bozzi, ”Signal-to-Noise evaluations for the CMS Silicon Microstrip Detectors,” CMS note
1997/026
n-XYTER parameters (for CBM-STS)fast channel slow channel 200e- +27 e-/pF 233e- + 13 e-/pF
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Cables Manufactured: SE SRTIIE, Kharkov, Ukraine
Simulated grids for various Isolation Techniques (SYNOPSYS)
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Metal workfunction = 4.29eVBarrier height (n-type) = 0.7eVBarrier height (p-type) = 0.58eV
p-spray
Measured / Simulated Cint
Good match after depletion Schottky worse than P-Stop/P-Spray when under-depleted => probably betterif schottky contact is reverse-biased
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CCE/Rint, Conventional Vs. Schottky
Schottky discarded (for UNBIASED schottky contact)8M.Singla IEEE-NSS 2012
Various combinations for modulated p-spray(@1x1014neqcm-2) p-stop => region with higher p-dose in modulated p-spray
p-spray dose (cm-3)
1×1015
(Very low dose)4×1016
(Low Dose)8×1016
(Medium Dose)12×1016
(High Dose)
p-stop width (μm)
Vbd (V)
Cint (pF cm-1)
Vbd
(V)Cint
(pF cm-1)Vbd
(V)Cint
(pF cm-1)Vbd
(V)Cint
(pF cm-1)
n-side p-side n-side p-side
n-side p-side n-side p-side
5 1125 1.56 1.75 490 2.40 1.75 210 2.46 1.76 161 2.47 1.77
10 1125 1.5 1.75 480 2.40 1.75 205 2.46 1.76 160 2.47 1.77
15 1150 1.6 1.75 488 2.37 1.75 205 2.43 1.76 160 2.47 1.77
20 650 2.09 1.75 450 2.51 1.75 205 2.42 1.76 160 2.47 1.77
Isolation
Technique
Fluence
(neqcm-2)
Vbd
(V)
Cint
(pFcm-1)
CCE
(%)
P-stop 2x1013
1x1014
800
610
2.08
2.09
93.15
88.87
P-spray 2x1013
1x1014
513
495
2.56
2.44
93.17
89
Optimized Modulated
P-spray
2x1013
1x1014
1600
1150
1.58
1.60
93.22
89
Optimized isolation technique
In optimized sensor design V bd twice
C int ~ 25 %
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εrANSYS (pF/cm)
RAPHAEL simulation
(pF/cm)
Relative diff .
1 0.328 0.337 2.2%
2 0.449 0.440 2.2%
3 0.566 0.531 6.1%
Package used : RAPHAEL (sub-package of SYNOPSYS)Validation of Package Used : a cable in the D0 silicon tracker simulated with the ANSYS simulations code, have been reproduced
and simulated results compared with measurements for CBM prototype readout cables.
Layers C tot (pF/cm)
Measured Simulated
Layer1 1.06 0.93
Layer 2 1.07 0.95
C tot => Capacitance of one trace w.r.t. all other traces
(Ref: Kazu Hanagaki, NIMA vol.511 2003, 121-123)
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Trace width* trace height
(μm*μm)Trace material
Capacitance (pF/cm)
Resistance (Ohm/cm)
Radiation length (%X0 )
Noise (ENCtot)e -
Slow shaper
Fast shaper
28*14 Aluminum 0.76 0.72 0.10 951 1922
Copper 0.76 0.43 0.15 932 1850
16*8 Aluminum 0.60 2.20 0.095 899 1892
Copper 0.60 1.31 0.11 856 1734
46*14 Aluminum 0.95 0.44 0.11 1077 2195
Copper 0.95 0.26 0.18 1062 2139
Same radiation length
Using Copper Same Radiation length300 e- less noise
Dependence of noise on trace geometry and material
However, when basing the electrical interconnection on tab bonding, the copper variant can not be applied, as opposed to the aluminum that is approved for wedge bonding the cable directly onto the silicon microstrip detectors or the front-end chip.
For now still working with the CBM prototype cables with Aluminum traces.
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Simulated/Experimental dB loss
Cable as a first orderlow-pass filter
V in
Vout
Readout Cable (10cm)
Vector Network Analyzer
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Transmission Losses for CBM readout cable prototype
For 30 cm. long cable
Transmission Coefficient (%)= (Vout / Vin ) *100
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Amplitude loss & Broadening of pulse=> ballistic deficit
Simulated I/O pulse 50 cm cable
Summary
TCAD tool SYNOPSYS used to design rad-hard DSSDs & low-noise system
New isolation technique “Schottky Barrier” compared with conventional isolation techniques
Optimized design of DSSD tolerant upto 1014 neq cm-2 and having low ENC proposed
Design optimization done for readout cables to reduce material budget and ENC
Expected dB loss for readout cables simulated and validated with measurements
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TCAD Validation (SYNOPSYS)
Measured I-V of DSSD having P-Stop Isolation Simulated I-V CharacteristicM.Singla IEEE-NSS 2012 17
TCAD Validation
Measured/Simulated I-V characteristics of DSSD having Schottky IsolationM.Singla IEEE-NSS 2012 18
Strip Isolation/Interstrip Resistance
Measured at MSU, M.Merkin et.al. Simulated Interstrip Resistance
Operating Voltage
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CCE Validation
G.Casse et. al., IEEE Trans. Nucl. Sci.,vol..55 (3), 2008, pp.1695 M.Singla IEEE-NSS 2012 20