simulation studies using garfield and ansys for...
TRANSCRIPT
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Simulation studies using Garfield and ANSYS for SπRIT TPC
Yaofeng Zhang for the SπRIT TPC collaboration
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Outline:
1. Introduction to
• Garfield program
• field cage of SπRIT TPC
• some simulation results based on the program
2. 3D Electric field calculations for SπRIT TPC using ANSYS
3. Summary and Conclusions
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1. Introduction
Widely used program for gas detectors—Garfield:
GARFIELD: • gas detectors simulations
• open source program
• electric field calculation(2D or simple 3D)
• nearly exact boundary method
• Can do 2D/3D simulations using E-field data from other
finite element method programs, such as OPERA-3D, ANSYS
• Can not save a data lib file, need field calculation for each
new running
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SπRIT and its simulations:
SπRIT-TPC has been constructed to constrain the symmetry-energy term in the nuclear Equation of State (EOS).
Cathode Plane
Pad Plane
Gating Wires
Strips
Anode Wires
Window Beam
Ground Wires
Strips
Field cage of SπRIT TPC
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Avalanche region:
Windows region
Drift region:
Electrons will be pre-amplified and collected in avalanche region, and that is why we can get signal.
Electrons will drift in this region. The strips here will help to achieve a very uniform electric field in this region.
Beam will go through this region and collide with the target.
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Electric field & drift simulation in the drift region:
Size range of the field cage :
A large number of strips were added to hold a uniform electric field inside the field cage.
Typical size of strips:
6mm(y)*0.035mm(z)*1m(x)
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Drift simulation
Drift simulationEqual potential distribution
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Avalanche region:
Electrons will be pre-amplified and collected in avalanche region, and that is why we can get signal.
Electric field & drift simulation in the avalanche region:
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-115 V
By=0.5T
anode wires
Ground wires
Gating grid wires
gating grid is open open: Vgg=-115; Voff=0
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-80 V-150 V -150 V
gating grid is closed
-80 V-150 V -150 V
By=0.5T
Closed: Vgg=-115; Voff=35
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Comparison for transparency results by different methods
for By=0
The transparent ratio was
calculated by:
T = 1−σg+||σp|
open
By=0T
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The experimental parameters:
anode wire: 680V
cathode: -6637.15V
By=0
Vgg=-114.84V
Transient condition(from open to closed)
Reason for difference:
The e-field near gating wires varies dramatically so that electrons will not strictly drift following the e-field lines.
GARFIELD with direct simulations
Analytic solution
Experiments
GARFIELD using mc-simulations
By=0T
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Windows region Beam will go through this region and collide with the target.
Window region :
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The window contains many layers of strips, and has a very complicated geometry.
We need to carefully analyze the e-field in the region nearby.
We have to do 3D electric field calculation and drift simulation!
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SπRIT TPC simulations using Garfield only:
• Electric field calculation• Detector simulations
• 2D calculation: OK
• 3D calculation: failed
• Needs more
memory(100G to start)
• Program often
terminated
• Needs a few weeks,
and often finally fails
• Solution: using external FEA program: ANSYS
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The pros for TPC simulations by GARFIELD using the e-field data from ANSYS:
• Can do 2D/3D simulations for TPC detectors
• Can generate a binary e-field file, which could be read by GARFIELD very
quickly(a few seconds). So we will save a lot of time for TPC’s repeated
simulation.
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2. 3D Electric field calculations for SπRIT TPC using ANSYS
The workflows for the electric field calculations in ANSYS:
build the geometry model
mesh the model
electric field calculation
apply the boundary condition
to refine the grids in the
region near wires and strips
to apply the BC according to
the position of each node
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3D meshed model
¼ of the whole body
Region of strips
Region of rear strips
Pad plane & wire regions
Window frame
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Top plate
drift area
x
y
z
electric field equalpotential
distribution
avalanche area
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Drift simulations for electrons based on 3D electric field data
Window region
Drift regionDrift region
1cmaway
Window region
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4. Summary and Conclusions
• Garfield program can be used to do 2D e-field calculation and drift simulations for SπRIT TPC.
• ANSYS program could be employed to do 3D e-field calculation, and 3D drift simulation for SπRIT TPC can also be finished with combination of Garfield.
• The simulation results agree well with the experimental data in the test stage.
• Simulation results could help us to get the optimal parameters for SπRIT TPC
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Acknowledge:
Suwat Tangwancharoen, Jon Barney, Justin Estee, Bill Lynch, Betty Tsang.
Funding of DOE.
Funding from BNU.
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Thanks!