1 Small GEM Detectors at STAR Yi Zhou University of Science & Technology of China.
Simulation of multi-layer GEM detectors
Transcript of Simulation of multi-layer GEM detectors
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Simulation of multi-layer GEM detectors
Aera JUNG, Yong BAN, Dayong WANG, Yue WANG, Licheng ZHANG
- school of physics, Peking University (PKU), China
1第十届全国先进气体探测器研讨会 (http://cicpi.ustc.edu.cn/indico/conferenceDisplay.py?confId=3793) online
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01 Contents
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• Motivation and Method
• Simulation results of single, double and triple GEMs
• Simulation results of quadruple GEMs
• Summary
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01 Contents
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• Motivation and Method
• Simulation results of single, double and triple GEMs
• Simulation results of quadruple GEMs
• Summary
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01 Introduction
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• Major advantage: With a multi-GEM layer structure, a very higheffective gain (up to 106 with some gases) can be attained with eachGEM layer working at an individually much lower gain thus avoidingdischarge problems.
• Our group’s simulation motivation:• Single, double and triple GEMs:
• Quadruple GEM:
- There is not enough information to compare and understand the differences between single, double and triple GEMs seen in experiments and simulations.- There are consistently seen difference in gain between simulation and experiment results.
- Lower operating voltage, low discharge probability and lowIBF make it more attractive for high radiation environments
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01 Simulation steps (characteristics of the detector)
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• Commercial software ANSYS + free software GARFIELD++
ANSYS : https://www.ansys.com/
Garfield++: https://garfieldpp.web.cern.ch/garfieldpp/
design the detector geometry, set boundary conditions and optimize the mesh of the structure for the electric potential calculation of each finite element
simulation of the electron motions
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01 Simulation model – GEM foil geometry and gas
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Fabio Sauli, The gas electron multiplier (GEM): Operating principlesand applications, Nuclear Instruments and Methods in Physics Research A 805 (2016) 2-24
• Schematics of single GEM detector
• Microscope view of GEM foil
• Standard hexagonal GEM foil
• The foil (e.g. 50 um thick kapton) is metalized on both sides (e.g. 5 um copper) and has a pattern of holes (e.g. 70 um with a 140 um pitch).
• Gas: Single, double and triple GEMs - 70% Ar + 30% CO2 triple and quadruple GEMs - 70% Ar + 30% CO2 and 90% Ar + 10% CO2
140 um
70 um
https://garfieldpp.web.cern.ch/garfieldpp/examples/triplegem/
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01 Simulation model – detector configuration in the simulation
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drift distance
[mm]
transferdistance
[mm]
inductiondistance
[mm]
HV divider readout shape
drift field
[kV/cm]
transfer field
[kV/cm]
induction field
[kV/cm]single 3 1 / 2 1 / 2 2 3.5 3.5 plate
double 3 1 / 2 1 / 2 2 3.5 3.5 plate
triple 3 1 / 2 1 / 2 2 3.5 3.5 plate
quadruple 4.8 2 2 strip[Rajendra Nath Patra, et al., Nucl. Instrum. Meth. A 906, 37-42 (2018)]
strip150 um
space60 um
pitch210 um
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01 Contents
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• Motivation and Method
• Simulation results of single, double and triple GEMs
• Simulation results of quadruple GEMs
• Summary
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01 Simulation results
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• Gain: given by the number of electrons created by each primaryelectron that reaches the anode
The experimental data (green)originally from Bachmann’s paper [S. Bachmann, et al., Nucl. Instrum. Meth. A 479, 294-308 (2002)]
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01 Simulation results
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• Spatial resolution: key parameters for tracking systems andextracted from the width of the residual distribution reached onthe anode/readout plate
• distance from the first GEM to the readout plate increases by about 15 um/mm
~150 um
• e.g. triple GEM (3/2/2/2) has a spatial resolution of ~240 um (=150 + 15 x 6)
triple GEMs
double GEMs
single GEMs
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01 Simulation results
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• Energy resolution: central for GEM detectors working inproportional mode and other devices aiming for a measurement of thedeposited energy
triple GEMsdouble GEMs
single GEMs
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01 Simulation results
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• Efficiency: the probability of a trespassing particle to yield theexpected signal and, if applicable, to overcome a threshold valueneeded have this signal recognized
triple GEMs double GEMs single GEMs
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01 Contents
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• Motivation and Method
• Simulation results of single, double and triple GEMs
• Simulation results of quadruple GEM
• Summary
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01 Simulation results
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• Spatial resolution: calculated by the Center of Gravity (COG) method• 70% Ar + 30% CO2• 150 GeV muon beam• Strip: 150 um• Space: 60 um
• Time resolution: used a Constant Fraction Discriminator (CFD) method• 70% Ar + 30% CO2
and90% Ar + 10% CO2
• Triple GEM better• 70:30 gas better
Experiment data originally from [Rajendra Nath Patra, et al., Nucl. Instrum. Meth. A 906, 37-42 (2018)]
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01 Simulation results
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• Primary electron transparency: defined as the fraction of electronsthat go through the first GEM foil
• Gas: 70% Ar + 30% CO2
X-ray source
free electron
150 GeV muon
free electron
• As the Edriftincreases, primary electron transparency decreases
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01 Simulation results
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• Effective gain
Experiment data originally from [Rajendra Nath Patra, et al., Nucl. Instrum. Meth. A 906, 37-42 (2018)]
• Efficiency• Gas: 70% Ar + 30% CO2• Input particle
• free electron• beta source
• Gas: 70% Ar + 30% CO2• Input particle
• X-ray• free electron• beta source
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01 Contents
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• Motivation and Method
• Simulation results of single, double and triple GEMs
• Simulation results of quadruple GEM
• Summary
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01 Summary
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• Single, double and triple GEMs
• Quadruple GEM
• Energy resolution deteriorates with more GEM layers
• Spatial resolution becomes poorer as the distance between thefirst GEM and the anode increases
• Efficiency is not so relevant to the number of GEM layers atappropriate HV
• Time resolution, spatial resolution, effective gain, efficiency and transparency are studied. Simulation and Experimental data are consistent.
• On going study: optimization of quadruple GEM structure design, Ion Back Flow rate, discharge effect….