Transcript Computer simulations of new kind of tracking detector

INTERNATIONAL PHD PROJECTS IN APPLIED NUCLEAR PHYSICS AND INNOVATIVE TECHNOLOGIES
This project is supported by the Foundation for Polish Science – MPD program, co-financed by the European Union within the European Regional Development Fund
Computer Simulations of New
Kind of Tracking Detector
Sedigheh Jowzaee
Jagiellonian University
Foundation Meeting, Krakow, Poland, 29 November 2011
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Outline
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Principle of operation
Applications
GARFIELD simulation
Results
Comparison with experiment
Future plans
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Straw Detector
 The straw tube is a proportional counter
 Gas-filled cylindrical tube made of aluminized mylar as a cathode
and Ø20 µm gold-plated tungsten wire stretched along the cylinder
axis as an anode
Charge particle track
crossing the straw
t
y   v(t )dt
t0
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Modular Straw Tube Tracker
 Moduls (easy to exchange, high flexibility)
 Low mass (self supporting by gas overpressure )
 High rates (1 MHz/wire)
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Low ageing & reasonable gain by choosing the best gas mixture
 Fast readout (pulse shaping and digitalization)
Assembly of modules
Double layer
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Straw Detector Application
 PANDA (antiProton Annihilation at DArmstdat) Detector
Central
Tracker
Micro-Vertex
detector
Forward
Muon
detector
Drift
Detector
Muon
Filter
Forward
Tracker
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Straw Detector Application
 Straw detector in medicine
A prototype breast PET camera, consisting of
6 lead-walled straw detector modules
Proposed 3D small animal PET scanner
using lead-walled straw detectors
(proportional tech)
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Straw Tube Simulation
 GARFIELD: a computer program for the detailed simulation
of two- and three-dimensional gas detectors.
 Garfield input is subdivided in sections:
 CELL : Chamber layout and voltage
 FIELD : Visualization of the Electric field
 MAGNETIC : Magnetic field setting
 GAS : Transport and ionization properties of the gas
 OPTIMISE : Modification and improvement of other sections
 DRIFT : Drifting of electrons and ions
 SIGNAL : Induced currents
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Straw Tube Simulation
Full penning transfer
No penning transfer
The gain curves vs. Anode voltage with
different Penning rates are compared with
preliminary experimental data
The detector signal for 0.7 GeV/c Pions
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Signal & Transfer Function
 Transfer Function: relation between the Laplace transform of
the output and input pulse H (s)  uout (s)
I in ( s)
 Front-end electronic response:
f (s) 
Shaping
n!
(1  s ) n 1
n: number of integrations
τ: time constant of one
integration stage
 n=2 , τ=10 nsec (peaking time=2*τ=20nsec)
Tail cancellation
( s 1  1).(s 2  1)
f ( s) 
( s 3  1).(s  1)
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Convoluted Signals
shaping
Threshold level
Threshold crossing
Detector output pulse
Pulse after shaping
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Convoluted Signals
Ion tail
Tail
cancellation
Removing the tail
filter
Ion Drift pulse after shaping
Shaped pulse after p/z filters
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Particle Identification Using dE/dx
 Amplitude
 Charge
 Time Over Threshold
TOT
Threshold level (-0.01 μA)
Amplitude
Charge (1 μsec integration)
Threshold crossing
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Signal for 0.7 GeV/c Pions
• Far from the anode wire
TOT
Threshold level (-0.01 μA)
• Near the anode wire
TOT
Threshold level (-0.01 μA)
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Distance Corrected Data of TOT
0.7 GeV/c Proton, Pion and Kaon
TOT of pions without distance correction
Distance from wire (cm)
Distance from wire (cm)
Distance from wire (cm)
TOT of pions with 2times distance correction
TOT of kaons with 2times distance correction
TOT (μsec)
Distance from wire (cm)
TOT (μsec)
TOT (μsec)
TOT of protons with 2times distance correction
TOT of kaons without distance correction
TOT (μsec)
TOT (μsec)
TOT (μsec)
TOT of protons without distance correction
Distance from wire (cm)
Distance from wire (cm)
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Separation Powers Comparison
Separation power after distance correction
K-p
Separation power
K-π
Separation power
Separation power
p-π
momentum (GeV)
momentum (GeV)
N A, B 
momentum (GeV)
 dE / dx  A   dE / dx  B
( A   B ) / 2
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TOT Histogram with Fe-55 Source
(5.9 keV X-ray & 2.9 keV Ar escape peak)
Simulated TOT
TOT spectrum in scope
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Conclusions
 Results show:
 TOT method works! (proved for the first time)
 TOT method shows similar separation power as the amplitude
 Distance correction improves resolution
Following Works
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Optimization the tail cancellation filter
High rate simulation
Adding noise function
Compare the simulation with experiment
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Foreign Collaboration Plans
 University of Ferrara, Italy: Building prototype STT
 Research Center Jülich, Germany: Testing Prototype STT
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Thanks for Your Attention.
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Cell & Field
Tube radius= 0.5 cm
Wire voltage=+1800 V
Wire radius= 10 μm
B=0
d=20 μm
D=1 cm
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Gas File
 Make a gas file with Magboltz 7
 90% Ar, 10% CO2, Temperature 300 K, Pressure 2 atm
 Importance of different parameters:
 Electric-field-range
 The number of points with N-E
 The number of collisions in MONTE-CARLO integration
Gain changes with E-range setting
Gain changes with no. of steps in E-range
250000
6.00E+05
Gain
4.00E+05
3.00E+05
200000
Gain
1: 100-100000 (default)
2: 100-200000
3: 600-350000
4: 100-350000
5.00E+05
150000
100000
2.00E+05
50000
1.00E+05
0
0.00E+00
0
1
2
E-range (V/cm)
3
4
0
10 20
30
40 50
60 70
N-E
80
90 100 110
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Gas Gain & Penning Effect
 Penning transfer rate
G  exp 
anode
tube

dr ( E (r ))
ion
i
( E (r ))   ri iexc ( E (r ))

ion
i
( E (r ))
Full penning transfer
 In Ar-CO2 gas mixtures:
•
Penning rate is below 50%
 New version of Magboltz 8.95
• Ar cross section is updated
The gain curves in this graph
correspond to Penning transfer rates
of 0%, 20%, 30%, 40% and 100%
are compared with preliminary
experimental data. This transfer
occurs at a rate of 30%.
No penning transfer
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Time Over Threshold (TOT)
 TOT: the width of signal at the
threshold level
 Time over threshold depends on


particle’s energy loss
track distance to wire
 Have to be corrected for
distance
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