Tomographic Imaging in Aditya Tokamak

1
Tomographic Imaging in Aditya Tokamak

• Nitin Jain

DivyaDrishti, Nuclear Engineering and Technology
Programme Indian Institute of Technology Kanpur
2
Acknowledgements

• Prof. Prabhat Munshi
• Indian Institute of Technology Kanpur
• Dr. C. V. S. Rao
• Institute for Plasma Research Gandhinagar

3
Outline

• Energy Demands Increasing
• Near Term Solution Fission
• Long Term Solution Fusion
• Confinement of Plasma Major Issues
• Instabilities and Impurities
• Online Feedback Needed for Selective Heating
• Stable Power Supply from Fusion Reactor
• Role of tomography is in step 5

4
Fusion
(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)

• 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

5
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.

6
Fusion Reactor

• An electric power plant based upon a fusion
  reactor

Plasma Confinement
7
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 www.jet.efda.org
8
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

9
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

10
Indian Nuclear Fusion Program Aditya Tokamak
Courtesy www.ipr.res.in
Major radius 0.75 m Minor radius 0.25
m Maximum toroidal magnetic field 1.2
T Currents 80-100 kA Plasma discharges
duration 100 ms
11
Problems in Confinement of Plasma

• Plasma Instabilities
• Impurities
• How do we measure impurities in plasma?
• Can we see various plasma instabilities
  non-invasively?

12
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

Diagnostics Measurement Information
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
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
13
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 www.jet.efda.org
14
Chord Segment Inversion (CSI) Algorithm
length of the segment of the ray falling
in ring average value of in
ring number of rings assumed within the object.
If the emissivity is circularly symmetric, g will
be a function of r alone.
15
Chord Segment Inversion (CSI) Algorithm

• Reconstructed emissivity values from CSI
  algorithm are fitted in phenomenological curve

Where
Data vector
Emissivity vector
16
Results Radial Profile of Emissivity
17
Emissivity Reconstructed Images
(Shot 13127)
18
Variation of Emissivity with Time
(Shot 13127)
19
Emissivity, Alpha and Plasma current w.r.t. Time
(Shot 13127)
20
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

21

• Thank You