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

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