Density Modulation Experiments on HT-7 Tokamak

Abstract

Density modulation experiments are successfully conducted on HT-7 ohmic discharge to investigate particle transport coefficients: diffusion coefficients D and convection velocity V. The particle transport is studied at low (1.5×1019 m−3) and high (3×1019 m−3) density regimes. The clear differences are observed that D is 0.42 m2 /s and 0.17 m2/s, V is 4.7 m/s (outward) and 1.6 m/s (inward) for low and high density plasmas respectively, where spatially constant D and V(r) = (r/a)V 0 were assumed for the analysis.

Particle confinement and transport coefficients in ac plasmas on the HT-7 superconducting tokamak

“…The modulation of electron density [13,14] has been studied to determine the particle diffusion coefficient (D) and the convection velocity (V ) on the HT-7 tokamak since 2004. The particle diffusion coefficient and the convection velocity were studied based on the density modulation using D2 gas puffing on the HT-7 tokamak.…”

“…To investigate the particle transport coefficients in ac plasmas, the method of gas puff modulation [9][10][11][12][13][14] is used to determine the particle diffusion coefficient (D) and the convection velocity (V ) on the HT-7 tokamak in 2007. The density modulation experiment shows that the particle diffusion coefficient (D) of the positive current plasma is almost the same as that of the negative one, but the inward pinch velocity (V ) of the positive one is much lower than that of the negative current plasma.…”

Observation of multi-channel non-local transport in J-TEXT plasmas

“…On the other hand, the spatial particle transport coefficients based on perturbation principle and modulation technology [26][27][28][29][30][31][32][33] reaches 90m/s. Normally, the particle convection velocity in other machines [26,27,33] which are similar size as J-TEXT is around 1~10m/s , which is already much higher than the neoclassic prediction (abnormal transport). Compared to experiment results of other machines, both averaged 40m/s and localized 90m/s, which are estimated from local transport mode, are astounding high value.…”

New evidence and impact of electron transport non-linearities based on new perturbative inter-modulation analysis

“…Different modulated sources can be used to perturb various transport channels such as: the electron heat transport by electron cyclotron resonance heating (ECRH) [7,8,9] or with repetitive pellet injection [10] or using a minority heating scheme [11]; particle transport using modulated gas-puffing with helium [12,13]; the momentum transport using modulated neutral beam injection (NBI) to modulate the torque [14,15,16]; the ion heat transport using ion cyclotron resonance heating [17,18]; and the analysis of impurity transport using for instance laser blow-off of boron and carbon materials [19]. This list is far from exhaustive and for a more complete overview of such experiments and its history the reader is referred to [2,3,20].…”