detector design and data analysis for heavy ion collision experiments
DESCRIPTION
Detector Design and Data Analysis for Heavy Ion Collision Experiments. Peter, Chan Chak Fai SURE 2011 Supervisor: Prof Betty Tsang(NSCL, MSU). National Superconducting Cyclotron Laboratory (NSCL) Michigan State University (MSU). With Prof Betty Tsang and HiRA group. Background. - PowerPoint PPT PresentationTRANSCRIPT
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Detector Design and Data Analysis for Heavy Ion Collision Experiments
Peter, Chan Chak Fai
SURE 2011
Supervisor: Prof Betty Tsang(NSCL, MSU)
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National Superconducting Cyclotron Laboratory (NSCL)Michigan State University (MSU)
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With Prof Betty Tsang and HiRA group
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Background• Symmetry Energy Project (SEP) is one of the current
projects at NSCL.
• Its physics goals include the determination the equation of state of nuclear matter, density dependence of symmetry energy, etc.
• Heavy ion collisions (Ca, Sn, etc.) are studied experimentally and with computer simulations.
• The project is an international collaboration.
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Equation of State
Energy in nuclei:
SymmetryEnergy TermImage from http://www.nscl.msu.edu/~tsang/iso_Texas_11.pdf
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Detector Design• A Time Projection Chamber (TPC)
is designed to detect pions and charged particles emitted in heavy ion collisions.
• The charged particles produced in heavy ions collision will ionize the gas in the chamber.
• The ionized gas is drifted towards the pad plane by electric and magnetic field.
• The drift time and the position of the ionized gas can be used to generate the tracks of primary charged particles.
• It is designed and made in US and will be installed in RIKEN, Japan.
Image from http://www-rnc.lbl.gov/EOS/
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Overall Design
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Overall Design
Lid and electronics
Field cage
Enclosure
Voltage step down
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Contributions in TPC design
• Use of Computer-Aided Design (CAD) software
• Design modification
• Model construction
• Rotation structure design
• Stress calculations
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CAD Software used• Autodesk Inventor, a Computer-Aided Design (CAD) software is used
for the 3D design of TPC.
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Design Modification
• Examples of my contributions:
• Changed the color of the cooling rod.
• Added the copper strips on the corners of the field cage.
• Modified the position of the standoff in voltage step down.
• Modified the dimension of the enclosure.
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Foam Model Making• The foam model of TPC is made and shipped to Japan to ensure it can
be placed inside the magnet.
• Made together with Jon Barney and Justin Estee.
MSURIKEN
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• Not all the ribs are made.
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• In addition, the TPC should be able to move down the hallways and doors in NSCL.
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• The foam model in Japan (photos from RIKEN)
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Rotation Structure Design• The TPC will be assembled upside down since there are wires to be
attached to the bottom of top plate.
• It has to stand on its side to move down the hallways at NSCL.
• One idea is to rotate the TPC around its center of mass:
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Stress analysis• The frame structure should be able to support the TPC(~520kg).
• The condition of the TPC on its side sitting on a cart is simulated by inventor.
• Less than 2mm deformation is observed.
• Simulation to rotate the TPC to different orientation is still in progress.
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Analysis of Computer Simulated Collision Data
• Simulations are done by Hang Liu using the supercomputer in Austin, Texas
• Improved Quantum Molecular Dynamics Model (ImQMD) is currently used, the results would be compared to transport theory(BUU) and real collision.s
• More than 60000 collision events are generated for each reaction.
• The collision under different initial conditions at different energies and impact parameters are simulated:
• Examples:
- Sn124+Sn124 (sn124s)
- Sn124+Sn112 (sn112m)
- Sn112+Sn124 (sn124m)
- Sn112+Sn112 (sn112s)
Visualization of collisions in computer simulation
Photo from Y.X. Zhang www.imqmd.com/income/zhang1.pdf
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Contributions in Data Analysis
• Computation knowledge of Fortran was used• Some observables were analyzed• Neutron-to-proton (n/p) ratio• Tritium-to-helium3 (t/3He) ratio• Ri value
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n/p ratio• Example: E70b7x0.7
- beam energy = 70MeV/A
- impact parameter = 7fm
- stiffness of equation of state of nuclear matter (gamma) = 0.7
n/p ratio for e70b7x0.7
0
0.5
1
1.5
2
2.5
3
0 20 40 60 80 100
Ec.m.(MeV)
n/p
ra
tio sn112m
sn112s
sn124m
sn124s
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• After colliding, fragments with lower energy have a higher neutron content, while that with higher energy have a higher proton content.
• The graphs of n/p ratio for other reactions and graphs of double ratio were also plotted.
n/p ratio for e70b7x0.7
0
0.5
1
1.5
2
2.5
3
0 20 40 60 80 100
Ec.m.(MeV)
n/p
ra
tio sn112m
sn112s
sn124m
sn124s
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t/3He ratio• t/3He ratio is interesting because neutron is hard to detect in experiment
and hence the error in experimental value of n/p ratio is high.
• More tritium(t) are produced in lower energy while more 3He are produced in higher energy in general.
t/He3 ratio for e70b7x0.7
0
0.5
1
1.5
2
2.5
3
3.5
0 10 20 30 40 50
Ec.m.(MeV)
t/H
e3
ra
tio sn112m
sn112s
sn124m
sn124s
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• The error in this result is larger than that of n/p ratio.
• The count number at high energy is small, which produces a relatively high statistical error.
• More events will be simulated to reduce the error.
t/He3 ratio for e70b7x0.7
0
0.5
1
1.5
2
2.5
3
3.5
0 10 20 30 40 50
Ec.m.(MeV)
t/H
e3
ra
tio sn112m
sn112s
sn124m
sn124s
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Ri value
• Ri is the isospin transport ratio, which is a measure of isospin diffusion.
• XAA refers to the neutron-rich system (sn124+sn124), XBB refers to the proton-rich system (sn112+sn112).
• If no diffusion, Ri(XAA) = 1; Ri(XBB) = -1.
• If isospin equilibrium is reached, Ri(XAB) = Ri(XBA) = 0.
• In theory, X is the asymmetry of the fragments.
• Two types of Ri: Ri(n,frag) and Ri(zmax>20)
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• In general, the isospin diffuse more at lower beam energy and lower gamma. Current plan is to compare Ri at more beam energies.
• Graphs for comparing different incident energies at fixed impact parameters were made.
• The next step is to compare for different impact parameters.
Value of Ri(n,frag), b7
00.10.20.30.40.50.60.70.80.9
0 0.5 1 1.5 2 2.5
gamma
Ri(
n,f
rag
)
e35(Ri(124+112))
e50(Ri(124+112))
e70(Ri(124+112))
e35(-Ri(112+124))
e50(-Ri(112+124))
e70(-Ri(112+124))
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Acknowledgement
• Thanks to Betty Tsang, Bill Lynch, Fei Lu, Rebecca Shane, Jon Barney and Justin Estee for all their help!
• Thanks to Department of Physics, CUHK for the opportunity of SURE!