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Behaviors of Electron Heat Transportation in HT-7 Sawtoothing Plasma

HT-7. ASIPP. Behaviors of Electron Heat Transportation in HT-7 Sawtoothing Plasma. Liqun HU, Yi XU, Baonian WAN, Yuejiang SHI Xiangjun ZENG and HT-7 Team. Institute of Plasma Physics Chinese Academy of Sciences Shushanhu Road 350, Hefei 230031, P. R. China

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Behaviors of Electron Heat Transportation in HT-7 Sawtoothing Plasma

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  1. HT-7 ASIPP Behaviors of Electron Heat Transportation in HT-7 Sawtoothing Plasma Liqun HU, Yi XU, Baonian WAN, Yuejiang SHI Xiangjun ZENG and HT-7 Team Institute of Plasma Physics Chinese Academy of Sciences Shushanhu Road 350, Hefei 230031, P. R. China E-mail contact of main author:lqhu@ipp.ac.cn

  2. HT-7 ASIPP In HT-7 ohmic plasma, main energy loss comes from electron heat conduction, electron thermal transportation plays a crucial role in determining achieved plasma parameters and their spatial distribution, which is very closely associated with the plasma confinement. Based on the heat pulse propagation originating from the sawtooth activity on the soft x-ray intensity signal, some data processing methods, including average of tens of sawteeth, has been tried to experimentally determine electron heat diffusivity on the HT-7 tokamak. As a result, methods of time to peak and sawteeth averaging have been adopted finally to get stable and reasonable electron heat diffusivity value. Based on preliminary understanding of the measured electron heat diffusivity, performances of different high confinement target plasmas are presented and discussed.

  3. HT-7 ASIPP Experimental apparatus HT-7 superconducting Tokamak R = 1.22 m, a = 0.27 m Ip = 100~250 kA BT = 1~2.5 T ne = 1~8x1013 cm-3 Te = 1~5 KeV Ti = 0.2~1.5 KeV Limiter: graphite limiter with poloidal and toroidal configuration ICRF: f = 15~30MHz, P = 0.3MW f = 30~110MHz, P = 1.5MW LHCD: f = 2.45GHz, P = 1.2MW Main Goal: Advanced Steady-state operation and related physics

  4. HT-7 Vertical array with 37 detectors of SBDs Au-Si detector Slot-aperture with a movable slider covered with Be foils Au-Si detector Horizontal array with 37 detectors of SBDs ASIPP Soft X-Ray Diagnostic Arrays High spatial resolution and time resolution

  5. HT-7 ASIPP Mathematical description of the heat pulse propagation General electron-heat-balance equation: Ignoring all heat sources and sinks, and assuming constant Ne (r) and e (r):

  6. HT-7 Dipole Model: Monopole Model: ASIPP • Time-to-peak analysis • Fourier transform based techniques • Time-domain modeling:data fitting by a model Time-to-peak analysis Fourier transform: sensitive to the shape of heat pulse high and better periodical sawtooth

  7. HT-7 ASIPP Time-to-peak analysis The dipole model: applied, more ideal and more suitable for HT-7 than the monopole model for good mathematical reasons and carrying zero total heat content.

  8. HT-7 ASIPP Data Processing Method for determining electron thermal diffusivity e 1. Function fitting Difficult to find suitable function for the data 2. Superposing of sawteeth heat pulse Good ratio of signal to noise, but sensitive to the initial point choice of each sawtooth, suitable for platform stage of the discharge. 3. Averaging of sawteeth Relatively simple, better for widely practical use

  9. HT-7 tPi ri ASIPP Averaging of tens of sawteeth

  10. HT-7 ASIPP Preliminary analyses of HT-7 electron heat transport 1.Asymmetry of the spatial electron heat transport Ip=200kA, BT=2.0T, ne=1.51019 m-3, PLHW=400kW, PIBW=230kW

  11. HT-7 ASIPP Improvement of heat transport in LHCD plasma Ip=220kA, BT=2.0T, ne=1.51019m-3, PLHW=260kW, f=2.45GHz

  12. HT-7 ASIPP Dependence of electron heat transport on LHW power Ip=125kA,BT=1.8T,ne=1.51019m-3

  13. HT-7 ASIPP Dependence of electron heat transport on IBW power Ip=150kA, BT=1.9T, ne=1.51019m-3, f=30MHz

  14. HT-7 ASIPP Dependence of electron heat transport on density in the synergy of LHW+IBW heated plasma Ip=200kA,BT=1.8T, PIBW=230kW(27MHz),PLHW=540kW

  15. HT-7 ASIPP Dependence of electron heat transport on density in the synergy of LHW+IBW heated plasma

  16. HT-7 ASIPP Dependence of electron heat transport on LHW power in the synergy of LHW+IBW heated plasma Ip=200kA,It=1.95T,ne=1.71019m-3,PIBW=230kW

  17. HT-7 ASIPP Discussion Dependence of RF power on electron heat transport

  18. HT-7 ASIPP Discussion Dependence of RF power on electron heat transport in the synergy of LHW +IBW

  19. HT-7 ASIPP Summary Preliminary analyses on HT-7 electron heat transport indicates: • Asymmetry of the spatial electron heat transport • LHW can not only drive plasma current and plasma temperature, but also improve plasma particle confinement and electron heat transport. As increase of the LHW power, electron heat transport decreases apparently. • In IBW heated plasma, the electron electron heat transport decreases obviously as the IBW power increase after the IBW power launched over a power threshold. • In the synergy of LHW and IBW plasma, the electron heat transport improves as the density increase, however, over a certain value, deteriorate as the power increase. • More deep and systematic analyses will be done to find detailed relations among the electron heat transport and plasma parameters.

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