The effect of time of applied bias on the edge turbulent transport is analyzed by the multi-fractal detrend fluctu- ation analysis （MF-DFA） method in the IR-Tl tokamak. The generalized Hurst exponents and the multif...The effect of time of applied bias on the edge turbulent transport is analyzed by the multi-fractal detrend fluctu- ation analysis （MF-DFA） method in the IR-Tl tokamak. The generalized Hurst exponents and the multifractal spectrum are computed by this method. The MF-DFA method is applied to the fluctuation of gradient of float- ing potential time series collected by a multipurpose probe. Tile monofractality or multifractality of the time series can be detected by generalized exponent. The multifractal spectrum describes the singularity content of the process. The results show that with applying bias to the plasma at different times （t = 15 ms, 18ms and 22ms）, the degree of multifractality changes. It reaches the minimum when the bias is applied at t = 18 ms. The multifractality source of data is investigated by the surrogate method （phase randomization techniques）. The surrogate method can destroy the different types of correlations in all the sizes of fluctuations. The results show that the long-range correlation contributes more to multifractality than the fat tail distribution.展开更多
The effect of the positive bias on Reynolds stress （RS） and its effect on the radial turbulent transport at the edge plasma （r/a =0.9） and scrape-off layer （SOL） region of plasma in tokamak are investigated. The...The effect of the positive bias on Reynolds stress （RS） and its effect on the radial turbulent transport at the edge plasma （r/a =0.9） and scrape-off layer （SOL） region of plasma in tokamak are investigated. The radial and poloidal electric fields （Sr, Ep） and ion saturation current （Is） are measured by multi-purpose probe （MPP）. This probe is fabricated and constructed for the first time in the IR-T1 tokamak. The most advantage of this probe is that the variations of Er and Ep can be measured in different radii at the single shot. Thus the information of different radii can be compared with high precision. The bias voltage is fixed at Vbias = 200 V and it has been applied with the limiter bias that is fixed in r/a = 0.9. Moreover, the phase difference between radial and poloidal electric fields, and temporal evolution of the RS .spectrum detected by MPP are calculated. RS magnitude on the edge （r/a = 0.9） is more than its value in the SOL （r/a = 1.02）. With the applied bias 200 V, ItS and the magnitude of the phase difference between Er and Ep are increased, while the radial turbulent transport is decreased simultaneously. Thus it can be concluded that RS affects radial turbulence. Temporal evolution of the RS spectrum shows that the frequency of RS is increased and reaches its highest value at r/a=0.9 in the presence of bias.展开更多
文摘The effect of time of applied bias on the edge turbulent transport is analyzed by the multi-fractal detrend fluctu- ation analysis （MF-DFA） method in the IR-Tl tokamak. The generalized Hurst exponents and the multifractal spectrum are computed by this method. The MF-DFA method is applied to the fluctuation of gradient of float- ing potential time series collected by a multipurpose probe. Tile monofractality or multifractality of the time series can be detected by generalized exponent. The multifractal spectrum describes the singularity content of the process. The results show that with applying bias to the plasma at different times （t = 15 ms, 18ms and 22ms）, the degree of multifractality changes. It reaches the minimum when the bias is applied at t = 18 ms. The multifractality source of data is investigated by the surrogate method （phase randomization techniques）. The surrogate method can destroy the different types of correlations in all the sizes of fluctuations. The results show that the long-range correlation contributes more to multifractality than the fat tail distribution.
文摘The effect of the positive bias on Reynolds stress （RS） and its effect on the radial turbulent transport at the edge plasma （r/a =0.9） and scrape-off layer （SOL） region of plasma in tokamak are investigated. The radial and poloidal electric fields （Sr, Ep） and ion saturation current （Is） are measured by multi-purpose probe （MPP）. This probe is fabricated and constructed for the first time in the IR-T1 tokamak. The most advantage of this probe is that the variations of Er and Ep can be measured in different radii at the single shot. Thus the information of different radii can be compared with high precision. The bias voltage is fixed at Vbias = 200 V and it has been applied with the limiter bias that is fixed in r/a = 0.9. Moreover, the phase difference between radial and poloidal electric fields, and temporal evolution of the RS .spectrum detected by MPP are calculated. RS magnitude on the edge （r/a = 0.9） is more than its value in the SOL （r/a = 1.02）. With the applied bias 200 V, ItS and the magnitude of the phase difference between Er and Ep are increased, while the radial turbulent transport is decreased simultaneously. Thus it can be concluded that RS affects radial turbulence. Temporal evolution of the RS spectrum shows that the frequency of RS is increased and reaches its highest value at r/a=0.9 in the presence of bias.
