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Tomographic Imaging in Aditya Tokamak
Nitin Jain
DivyaDrishti, Nuclear Engineering and Technology Programme
Indian Institute of Technology Kanpur
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Acknowledgements
• Prof. Prabhat Munshi
Indian Institute of Technology Kanpur
• Dr. C. V. S. Rao
Institute for Plasma Research Gandhinagar
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Outline
1. Energy Demands : Increasing
2. Near Term Solution : Fission
3. Long Term Solution : Fusion
4. Confinement of Plasma : Major Issues– Instabilities and Impurities
5. Online Feedback Needed for “Selective” Heating
6. Stable Power Supply from Fusion Reactor
Role of tomography is in step 5
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(1) D + D → T (1.01 MeV) + p (3.03
MeV)
(2) D + D → He3 (0.82 MeV) + n (2.45
MeV)
(3) D + T → He4 (3.52 MeV) + n (14.06
MeV)
(4) D + He3 → He4 (3.67 MeV) + p (14.67
MeV)
(5) Li6 + n → T + He4 + (4.8 MeV)
(6) Li7 + n → T + He4 + n – (2.5 MeV)
Fusion
For D-T reaction: Largest cross section Energy released highest
Why is fusion power attractive?
• Fuel is widely available • Reaction is relatively clean• Low cost
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Thermo Nuclear Fusion
• D-T mixture to be heated to 100 million degrees in order to overcome Coulomb repulsion
• Why Plasma is required?
• Necessary conditions for fusion• Temperature
• Density
• Confinement
These simultaneous conditions are represented by a fourth state of
matter called PLASMA.
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Fusion Reactor
An electric power plant based upon a fusion reactor
Plasma Confinement
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Magnetic Confinement: Tokamak
• A tokamak is a plasma confinement device invented in the 1950s
• Plasma is confined here by magnetic fields.
• The magnetic fields in a tokamak are produced by a combination of currents flowing in external coils and currents flowing within the plasma itself
Magnetic circuit of JET tokamak
Courtesy: w
ww
.jet.efda.org
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Experimental tokamaks: Currently in operation
• T-10, in Kurchatov Institute, Moscow, Russia (formerly Soviet Union); 2 MW; 1975 • TEXTOR, in Jülich, Germany; 1978 • Joint European Torus (JET), in Culham, United Kingdom; 16 MW; 1983 • CASTOR in Prague, Czech Republic; 1983 after reconstruction from Soviet TM-1-MH • JT-60, in Naka, Ibaraki Prefecture, Japan; 1985 • STOR-M, University of Saskatchewan; Canada 1987; first demonstration of alternating
current in a tokamak. • Tore Supra, at the CEA, Cadarache, France; 1988 • Aditya, at Institute for Plasma Research (IPR) in Gujarat, India; 1989 • DIII-D,[4] in San Diego, USA; operated by General Atomics since the late 1980s • FTU, in Frascati, Italy; 1990 • ASDEX Upgrade, in Garching, Germany; 1991 • Alcator C-Mod, MIT, Cambridge, USA; 1992 • Tokamak à configuration variable (TCV), at the EPFL, Switzerland; 1992 • TCABR, at the University of Sao Paulo, Sao Paulo, Brazil; this tokamak was
transferred from Centre des Recherches en Physique des Plasmas in Switzerland; 1994.
• HT-7, in Hefei, China; 1995 • MAST, in Culham, United Kingdom; 1999 • UCLA Electric Tokamak, in Los Angeles, United States; 1999 • EAST (HT-7U), in Hefei, China; 2006
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Experimental tokamaks: Planned
• KSTAR, in Daejon, South Korea; start of operation expected in 2008 • ITER, in Cadarache, France; 500 MW; start of operation expected in 2016 • SST-1, in Institute for Plasma Research Gandhinagar, India; 1000 seconds operation;
currently being assembled
ITER
Official objective
"demonstrate the scientific and technological feasibility of fusion energy for peaceful purposes"
Participants
European Union (EU), India, Japan, People's Republic of China, Russia, South Korea, and USA
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Indian Nuclear Fusion Program: Aditya Tokamak
Major radius = 0.75 mMinor radius = 0.25 mMaximum toroidal magnetic field = 1.2 TCurrents = 80-100 kA Plasma discharges duration ~ 100 ms
Courtesy: w
ww
.ipr.res.in
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Problems in Confinement of Plasma
• Plasma Instabilities• Impurities
• How do we measure impurities in plasma?
• Can we see various plasma instabilities non-invasively?
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Role of Plasma Tomography in Fusion
• Tomography is the only tool to give non-invasive point wise information about instabilities
• Diagnostics paint a picture of plasma evolution
Soft x-ray tomography
X-ray emissivity contours Thermal instability, tearing modes, Sawtooth activity, internal disruptions, &
Major disruptions
Microwave interferometer
Phase change through plasma
Evolution of electron density
Optical tomography Visible radiation profile Density profile modification & micro instability stabilization
Diagnostics Measurement Information
Hard X-ray tomography
Fast electron production and confinement
Steady state operation of tokamaks & LHCD performance
Gamma-ray tomography
-ray emission profile Radial distribution of fast ions
Neutron tomography Generation and volume distribution of neutrons
Fish-bone instability, burst of neutron emission & fusion reaction monitoring
Bolometry tomography
Radiation profile and radial distribution
Radiative instability, MARFE, & MERFE
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Soft X-ray Tomography
Soft x-ray tomography gives measure of
Plasma density Temperature of Plasma Impurities in Plasma Determination of position and shape of
Plasma Determination of radial current distribution
These X-rays are utilized to study MHD Phenomena
Courtesy: w
ww
.jet.efda.org
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Chord Segment Inversion (CSI) Algorithm
,
,,pL
dsrgpf
L
dsrgd ,
m
jjjkk gSd
1,
= length of the segment of the ray falling in ring== average value of in ring= number of rings assumed within the object.
jkS ,thk thj
CBBC
jg g thjm
maxL
1jL
jL
kL
0LB
C CB
o
1jj
k
ringthj ringthj )1(
Plasma
Detectorsmk ,.......,2,1
If the emissivity is circularly symmetric, g will be a function of r alone.
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Chord Segment Inversion (CSI) Algorithm
• Reconstructed emissivity values from CSI algorithm are fitted in phenomenological curve
gSd Where
11 .,........., dddd mm Data vector
11 .,.........,][ gggg mm Emissivity
vector
1,11,2,1
1,1,1
, 00
SSS
SS
S
S
mm
mmmm
nm
dSg 1
2
2
1)0()(a
rgrg
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Results: Radial Profile of Emissivity
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Emissivity Reconstructed Images
(Shot # 13127)
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Variation of Emissivity with Time
(Shot # 13127)
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Emissivity, Alpha and Plasma current w.r.t. Time
(Shot # 13127)
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Conclusions
• Experimental results indicate a successful adaptation of the tomography technique for the analysis of events occurring during a plasma discharge
• Reconstructed profiles can be used to study the sawtooth instability, major and minor disruptions, impurity transport, and the phenomena following pellet injection
• Profile peakedness parameter () can be used to predict information about the evolution phase of the discharge and termination phase
• CSI algorithm has given very good results in reconstruction of emissivity and can be used for real time tomography in fusion experiments
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Thank You
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