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Recent experiments in the STOR-M Tokamak*

Recent experiments in the STOR-M Tokamak*. Akira Hirose In collaboration with: C. Boucher (INRS-EMT), G. St. Germaine D. Liu, S. Livingstone, A. Singh, C. Xiao. Plasma Physics Laboratory University of Saskatchewan Saskatoon, Saskatchewan, Canada *Supported by NSERC, CRC. Outline.

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Recent experiments in the STOR-M Tokamak*

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  1. Recent experiments in the STOR-M Tokamak* Akira Hirose In collaboration with: C. Boucher (INRS-EMT), G. St. Germaine D. Liu, S. Livingstone, A. Singh, C. Xiao Plasma Physics Laboratory University of Saskatchewan Saskatoon, Saskatchewan, Canada *Supported by NSERC, CRC

  2. Outline • Edge plasma flow measurements with Mach probes • Low frequency edge density and potential fluctuation measurements with Langmuir probes (GAM) • Skin size ballooning mode (theory) • Density fluctuation measurements with 2 mm microwave scattering (search for ETG and skin size mode) • Vertical CT (compact torus) injection • Future plan PPL, Univ. of Sask.Department of Physics & Engineering Physics

  3. STOR-M top view PPL, Univ. of Sask.Department of Physics & Engineering Physics

  4. STOR-M side view PPL, Univ. of Sask.Department of Physics & Engineering Physics

  5. 4-Pair Mach (Gundestrup) Probes PPL, Univ. of Sask.Department of Physics & Engineering Physics

  6. Ohmic discharge (Ip counter to Bt) Flow is predominantly along the magnetic field. PPL, Univ. of Sask.Department of Physics & Engineering Physics

  7. Parallel flow in the direction of current. r=10.5 cm t=17 ms Bt Ip PPL, Univ. of Sask.Department of Physics & Engineering Physics

  8. When the current is reversed, so is the flow. r=12 cm t=17 ms Bt Ip PPL, Univ. of Sask.Department of Physics & Engineering Physics

  9. Neoclassical theory • In an axisymmetric plasma, Toroidal flow Poloidal flow may depend on collisionality PPL, Univ. of Sask.Department of Physics & Engineering Physics

  10. Electrode Biasing PPL, Univ. of Sask.Department of Physics & Engineering Physics

  11. GAM (Geodesic Acoustic Mode) • GAM frequency • In GAM, the potential is symmetric but density perturbation is not, • Excitation mechanism? Its roles? poloidal angle PPL, Univ. of Sask.Department of Physics & Engineering Physics

  12. Probes and locations PPL, Univ. of Sask.Department of Physics & Engineering Physics

  13. Observation • Potential fluctuations have a peak at f ~ 12-15 kHz at all positions • Density fluctuation has this peak except at the outer mid plane q = 0 where it is small. • Unclear what role is played by GAM in transport. PPL, Univ. of Sask.Department of Physics & Engineering Physics

  14. Power spectra of potential and density fluctuations Density at -90 degrees (bottom) Potential at 0 degree Density at 0 degree PPL, Univ. of Sask.Department of Physics & Engineering Physics

  15. Skin size ballooning mode • Skin size plasma turbulence has long been speculated. Such turbulence would explain Ohkawa diffusivity and thus Alcator scaling • Earlier this year, a novel short wavelength ballooning mode was predicted in the regime PPL, Univ. of Sask.Department of Physics & Engineering Physics

  16. Electron thermal diffusivity in units of gyro-Bohm PPL, Univ. of Sask.Department of Physics & Engineering Physics

  17. 2 mm microwave scattering: experimental setup Upper mirror Received signal Directional Coupler Detector 2 Standard Gain Horn Klystron Isolator Mixer Vertical ports on STOR-M chamber Power supply and cooling system E-H Tuner Isolator Detector 1 Directional Coupler Plasma Two Attenuators 20dB Phase Shifter Scattering Volume Reference Arm Quartz windows Over-moded (WR-28) waveguide sections Transmitted signal GOLA Horn Lower mirror PPL, Univ. of Sask.Department of Physics & Engineering Physics

  18. Dispersion relation The solid line indicates the ion drift mode. The observed normalized frequency tends to be constant at high k. PPL, Univ. of Sask.Department of Physics & Engineering Physics

  19. Fueling Large Tokamak A.J.H. Donne et al. Fusion Sci. &Tech., January 2006 issue: “In the field of density control it has been concluded that there is not much flexibility in the fueling of ITER.” As part of their recommendations, they further state: “New fueling techniques should be tested on present devices. Given the prospects of CT (compact torus) injection, a test on a relatively large device is highly desirable.” [Summary of 2005 IEA Workshop on Burning Plasma Physics and Simulations, Tarragona, Spain] PPL, Univ. of Sask.Department of Physics & Engineering Physics

  20. Compact Torus (CT) injectionHorizontal vs. vertical PPL, Univ. of Sask.Department of Physics & Engineering Physics

  21. USCTI with deflector PPL, Univ. of Sask.Department of Physics & Engineering Physics

  22. Effects of vertical CT injection (preliminary) PPL, Univ. of Sask.Department of Physics & Engineering Physics

  23. Vertical CT injection (cont.) PPL, Univ. of Sask.Department of Physics & Engineering Physics

  24. Future plan • Plasma flow: more complete plasma data are needed for comparison with the neoclassical theory • Repetitive CT injection • Heterodyne 2 mm microwave scattering • Numerical simulations of the skin size ballooning mode PPL, Univ. of Sask.Department of Physics & Engineering Physics

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