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Tokamak and Tokamak related Diagnostic Experience in India

Tokamak and Tokamak related Diagnostic Experience in India. Parameswaran Vasu vasu@ipr.res.in I nstitute for P lasma R esearch Gandhinagar, INDIA Web site : http://www.ipr.res.in. Out line of the Talk. Introduction to IPR Introduction to Indian Tokamaks Diagnostics Systems at IPR

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Tokamak and Tokamak related Diagnostic Experience in India

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  1. Tokamak and Tokamak related Diagnostic Experience in India Parameswaran Vasu vasu@ipr.res.in Institute for Plasma Research Gandhinagar, INDIA Web site:http://www.ipr.res.in

  2. Out line of the Talk • Introduction to IPR • Introduction to Indian Tokamaks • Diagnostics Systems at IPR • Summary

  3. Where we are located CAT IPR SINP

  4. About the Institute • The Institute for Plasma Research (IPR) – Located in village • Bhat- a few kilometers from Ahmedabad Intnl. Airport • Institute was established in 1986 • 210 Scientist /Engineers • TOTAL STAFF STRENGTH = 440

  5. Objectives Of the Institute • Experimental & Theoretical research in Plasma sciences & Nonlinear phenomena • Physics and Technology of Magnetically Confined Plasmas • To stimulate plasma Research & Development activities in the Universities and Industrial sector. • Contribute in the training of plasma Physicists & Technologists in the Country.

  6. Indian Tokamaks SINP ADITYA SST-1 Major Radius R0(m) 0.30 0.75 1.1 Minor Radius a (m) 0.045-0.075 0.25 0.2 Toroidal Field BT (T) 2.00 1.50 3.0 Plasma Current Ip (kA) 75 250 220 Pulse Duration (s) 0.02-0.03 0.25 1000 Plasma Cross-section Circular Circular Elongated Elongation ---- ----- 1.7-2.0 Triangularity ---- ----- 0.4-0.7 Configuration Poloidal Poloidal Double/single Null Limiter Limiter Poloidal Divertor Coils Type (TF & PF) Copper Copper Superconducting Water Cooled 4.5K Current Drive & Heating ----Ohmic Transformer------ Ohmic/LHCD (Iron Core)(Air Core) (Air Core) Vacuum vessel Conducting Vessel with Vessel without Shell (Al) Electrical break Break Design & Fabrication M/S Toshiba Indigenous Indigenous Installation 1987 1989 2006

  7. SINP Tokamak Diagnostics • Spectroscopy • Microwave interferometry • Internal magnetic and rogowskii coils • Time of flight analyser • Hard X-ray systems for Runaway electrons

  8. SINP Tokamak • Two Operational Regimes: • Normal q regime ; q egde > 3 • Low q & ultra low q regimes; 0 < q egde < 2 • Experiments in normal q regime: • Drift wave like instability in Tokamak core region. • Anomalous current penetration • Temperature fluctuation induced anomalous transport • Origin of inversion of up-down potential assymetry • Observation of Runaway Electrons by ECE • Current holes, negative currents have been observed • Experiments in low q regime: • Accessibility condition for VLQ and ULQ regimes • Anomalous Ion heating in VLQ discharges • Edge Biasing experiemts in VLQ dicharges • Runaway Electrons in startup phase of VLQ discharges • Variation in Up-down asymmetry with edge safety factor

  9. ADITYA Since 1989 … Major Radius R0(m) 0.75 Minor Radius a (m) 0.25 Toroidal Field BT (T) 1.50 Plasma Current Ip (kA) 250 Plasma Cross-section Circular Configuration Poloidal Limiter

  10. ADITYA discharge

  11. ADITYA discharge

  12. Diagnostics on ADITYA • Magnetic probes • Langmuir probes • Microwave interferometer • Soft X-ray, Vert. and Hor. Arrays • Bolometer array • HXR • Thomson Scattering • Spectroscopy, Visible to EUV • Impurity line monitors • Visible continuum • ECE • Microwave reflectrometry • Lithium themal beam and laser blow off • Limiter IR thermography

  13. Inward particle transport [NF 1993]: • Net flux outward, differential flux bipolar • Low freq (<20 kHz) flux inward • Ionization driven drift instability Inward Outward Net flux outward

  14. Intermittency measured through non-Gaussian PDF (PRL, 1992). • First in ADITYA • Confirmed worldwide • New perspective • -- intermittent/ • bursty transport • --IPO / coherent • structures

  15. Publications [1] Phys. Rev. Lett. 69, 1375 (1992). [2] Nucl. Fusion 33, 1201 (1993). [3] Current Science 66, 25 (1993). [4] IAEA (1993) Vol. 1, pp. 467-472. [5] Phys. Rev. Lett. 73, 3403 (1994). [6] Phys. Plasmas, 3, 2979 (1996) [7] Phys. Plasmas 4, 2982 (1997). [8] Phys. Plasmas 4, 4292 (1997). [9] Pramana, 55, 727 (2000). [10] Phys. Plasmas 10, 699 (2003). [11] IAEA (1995) Vol.1, pp. 583-591. [12] In Nonequilibrium Phenomena in Plasmas, Springer, Dordrecht, (2005) pp. 199-218. [13] Phys. Plasmas 12, 072520 (2005).

  16. Thomson Scattering 7 Channels 100 GHz Interferometer plot- ---log I vs ( )2

  17. SXR Front view Horizontal Array • 36 detectors distributed in 2 arrays. • X-ray energy range : 500 eV to 15 keV. Spatial resolution : 1.5 cms. • Temporal resolution : 10 microsecs. • Absorber foil technique for Te (100eV to 800eV) Vertical Array Side view

  18. SXR Tomographic pictures

  19. Plasma Spectroscopy, IPR • Spectroscopy Group in IPR is involved in the following diagnostics monitoring plasma emission in • Visible to EUV wavelengths • Halpha • Visible Continuum • Impurity monitoring • Using • 1.0 mVacuum Normal Incidence Spectrograph • 1.5 m Vacuum Grazing Incidence Monochromator • 0.3 m Vacuum EUV Survey Spectrograph • 0.5 m Visible spectrograph • 1.0 m Visible imaging (multi-track) Spectrograph • Filters-PMT Assemblies

  20. RESULTS The existing Spectroscopic Diagnostic facilities are versatile enough to be used in diverse situations encountered in ADITYA operation and yield good quality data which have been used in: • Fluctuation studies • Impurity Influx estimates • Zeff measurements • Profile reconstruction of emissivities • Spectral line shape analysis • The results have been used to model our discharges using codes like Tokamak Simulation Code (TSC)

  21. Sawteething: Cross correlation between SXR (from Core) and H (from edge) shows 200 sec delay. [ICPP Conf. (2004)] Time series analysis shows the oscillations (~10 KHz) in CIV emission correlating to MHD oscillation (m=2) Mirnov signal. Fluctuation

  22. 41.7 nm Fe XV Time (ms) Reduction in Fe signal following wall conditioning Successive spectra (15 ms apart): evolution of CIII and CV ionization stages Impurity Influx

  23. Visible continuum measurement: Typical intensities ~1011 photons/cm2.sr.nm.sec, 50 s time resolution, S/N ~ 4 Zeff during a clean shot estimated, and compared with modelling results from Tokamak Simulation Code[PPCF (2004)] Noise Level Zeff measurements

  24. Profile reconstruction of emissivities & Line Shape Multi-track spectral data around H from nine poloidal chords simultaneously; OV, H and CII are seen Analysis of H line shape shows presence of multi-temp. components of Hydrogen atoms in the plasma edge Inversion of above data shows emitting regions of H, CII and OV at plasma edge

  25. ADITYA wall conditioning often uses a helium discharge by ECR, upon which periodic Ohmic Pulsed Discharges (PD) are superimposed (4 ms every 4 s) ECR plasma (Te~17eV, Ne~7.5x1010 cm-3) is confined to a narrow region, while during PD, the plasma (Te~8.5eV, Ne~9x1011 cm-3)fills vessel cross section. Analysis of spectral data using a Collisional Radiative (CR) Model code to infer Te and Ne that ‘best fit’ the Helium lineintensities [JAP (2005)] Analysis of spectra with CR Model

  26. ADITYA simulations using TSC • Total eight shots were chosen for modeling. Typical parameters : • R/a=0.75/0.25m, BT=0.75T, Ip~65-75kA, density~1.2-2 x1013/cc, • discharge duration 75-95 msec, negligible hard X-ray during flat top • Inputs to TSC : • Plasma and vessel geometry, experimental OT and BV currents. But FB applied on these currents to force TSC follow experimental Ip and Rp. Hence the differences between experimental and simulated values are to be considered as error in the simulations. • experimentally measured central and edge densities. Density profile chosen as ne(ψ,t)=ne0(t)(1- ψβ)α+nb. α=1, β=2 chosen for all shots • Impurity concentrations

  27. TSC simulation results of ADITYA shot #12308

  28. Te,i profiles Impurity charge states Current profile χe,i (m2/s) ψ Flux surfaces TSC simulation results (other parameters) #12486 t=20 msec t=60 msec

  29. Publications [14] “Modelling of Ohmic discharges in ADITYA tokamak using Tokamak Simulation Code”, Plas. Phys. & Cont. Fus., 46, 1443 (2004). [15] Optimization of the number of soft x-ray arrays and detectors for SST-I Tokamak by the tomographic method. Rev. Sci. Ins., 74, 2353 (2003). [16] Superiority of Bessel function over Zernicke polynomial as base function for radial expansion in tomographic reconstruction.Pramana, 61, 141 (2003) [17]"Characterization of Helium Discharge Cleaning Plasmas in ADITYA Tokamak Using collisional radiative-model Code", Jnl. App. Phys. (2005). [18] “Exploring core-to-edge transport in Aditya tokamak by oscillations observed in the edge radiation”Proc. 12th International Congress on Plasma Physics (ICPP), held during October 25-29, 2004 at Nice, France.

  30. SST-1 : A steady state superconducting tokamak • OBJECTIVES: • Study Physics of Plasma Processes in tokamak under steady-state conditions. • Particle Control (fuel recycling and impurities) • Heat removal • Divertor Operation (radiation, detachment , pumping etc ) • Current maintenance • LHCD, Bootstrap, advanced configurations • Learning new Technologies relevant to steady state tokamak operation: • Superconducting Magnets • Large scale Cryogenic system (He and LN2) • High Power RF Systems • Energetic Neutral Particle Beams • High heat flux handling

  31. Status: • SST-1 assembly has been completed. Commissioning is in progress. • Integrated operation of the Cryogenic system with magnets and thermal shield have been carried out and distribution of cryogens have been checked. • Cooling of thermal shields up to 80K and of magnets up to 70K has been achieved. • Leaks in the cryogenic distribution were observed and prevented further cool down of magnets. The leaks have been identified and repaired. • Modifications of the Liquid Nitrogen distribution Has been completed to achieve uniformity in temperatures at different thermal shields. • In-vessel and other first phase diagnostics have been integrated to SST-1. • Next cool down scheduled to start in two months.

  32. DIAGNOSTICS ON SST-1 • Far Infrared Interferometers -- Density measurement and Control • Vertical , Lateral and Tangential • Electron Cyclotron Emmission • Radiometer 91-130 GHz • Fast Scanning Fourirer Transform Michelson Interferometer 75-1000 GHz • Thermography • Thomson Scattering • X-Rays • Soft X-Ray imaging; Hard X-Ray Monitors; Vacuum Photodiode Array • Motional Stark Effect • Spectroscopy • Passive : Visible/UV/VUV • Active : HNB based CXRS & MSE • Electromagnetic Sensors • Rogowskii Coils -- Plasma current & Halo Current • Mirnov Coils -- Magnetic Fluctuations & Eddy Currents • Magnetic Probes -- Plasma position and shape measurements • Saddle Loops -- Locked mode detection • Fiber Optic Current sensors -- Plasma current • Hall Probes -- Plasma current and position • Flux Loops -- Loop Voltage • Diamagnetic Coils -- total stored energy • Langmuire Probes Divertor Plasma

  33. Summary • I P R has built Aditya & SST-1 Indigenously • Developed & Installed various diagnostics in Aditya • Design & Procurement of diagnostics systems for SST-1 is underway. • In India we have a big diagnostics group with first hand experience in: • Designing and putting together a variety of optics and spectroscopy based diagnostics, and • The analysis of data from such diagnostics Which will enable us to execute effectively the ITER related diagnostics responsibilities we undertake

  34. Thank you

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