1/21

Tomographic Imaging in Aditya Tokamak

Nitin Jain

DivyaDrishti, Nuclear Engineering and Technology Programme

Indian Institute of Technology Kanpur

2/21

Acknowledgements

• Prof. Prabhat Munshi

Indian Institute of Technology Kanpur

• Dr. C. V. S. Rao

Institute for Plasma Research Gandhinagar

3/21

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

4/21

(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

5/21

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.

6/21

Fusion Reactor

An electric power plant based upon a fusion reactor

Plasma Confinement

7/21

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

8/21

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

9/21

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

10/21

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

11/21

Problems in Confinement of Plasma

• Plasma Instabilities• Impurities

• How do we measure impurities in plasma?

• Can we see various plasma instabilities non-invasively?

12/21

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

13/21

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

14/21

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.

15/21

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

16/21

Results: Radial Profile of Emissivity

17/21

Emissivity Reconstructed Images

(Shot # 13127)

18/21

Variation of Emissivity with Time

(Shot # 13127)

19/21

Emissivity, Alpha and Plasma current w.r.t. Time

(Shot # 13127)

20/21

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

21/21

Thank You