arXiv subjects

Yuejiang Shi

Publications and source records attributed to Yuejiang Shi.

23 records · Page 2Linked to original sources

arXiv2018

Dynamics of cold pulses induced by super-sonic molecular beam injection in the EAST tokamak

Evolution of electron temperature, electron density and its fluctuation with high spatial and temporal resolutions are presented for the cold pulse propagation induced by super-sonic molecular beam injection (SMBI) in ohmic plasmas in the EAST tokamak. The non-local heat transport occurs for discharges with plasma current $I_p$=450 kA ($q_{95}\sim5.55$), and electron density $n_{e0}$ below a critical value of $(1.35\pm0.25)\times10^{19}~\mathrm{m^{-3}}$. In contrary to the response of core electron temperature and electron density (roughly 10 ms after SMBI), the electron density fluctuation in the plasma core increases promptly after SMBI and reaches its maximum around 15 ms after SMBI. The electron density fluctuation in the plasma core begins to decrease before the core electron temperature reaches its maximum (roughly 30 ms). It was also observed that the turbulence perpendicular velocity close to the inversion point of the temperature perturbation changes sign after SMBI.

physics.plasm-ph↗

arXiv2018

Alternating Current Adiabatic Compression Tokamak: A New Way to Fusion Reactor

A novel magnetic confined fusion scheme for the fusion reactor is proposed in this paper. A simple numerical estimation shows that ignition of D-T plasma can be achieved in tokamak with only OH heating by major and minor radius adiabatic compression. The density and temperature of compressed plasma can reach 1-3*10^22/m^3 and 15-25keV, respectively. Alternating current with adiabatic compression pulse of ACACT with R0 = 1.8m can deliver 400MW fusion power.

physics.plasm-ph↗

arXiv2017

New experimental findings of non-local transport in J-TEXT plasmas

In the cold pulse experiments in J-TEXT, not only are the rapid electron temperature increases in core observed, but also the steep rises of inner density are found. Moreover, the core toroidal rotation is also accelerated during the non-local transport process of electron temperature. These new findings of cold pulse experiments in J-TEXT reveal that turbulence spreading is the possible mechanism for the non-local transport dynamics.

physics.plasm-ph↗

arXiv2016

Fluctuation signatures of rotation reversals and non-local transport events in KSTAR L-mode plasmas

Experiments of electron cyclotron resonance heating (ECH) power scan in KSTAR tokamak clearly demonstrate that both the cut-off density for non-local heat transport (NLT) and the threshold density for intrinsic rotation reversal can be determined by the collisionality. We demonstrate that NLT can be affected by ECH, and the intrinsic rotation direction follows the changes of NLT. The cut-off density of NLT and threshold density for rotation reversal can be significantly extended by ECH. The poloidal flow of turbulence in core plasma is in the electron and the ion diamagnetic direction in ECH plasmas and high density OH plasma, respectively. The auto-power spectra of density fluctuation are almost the same in the outer region for both ECH and OH plasmas. On the other hand, in the core region of ECH plasmas, the power spectra of the density fluctuations are broader than those of OH plasma. All these observations in macroscopic parameters and micro fluctuations suggest a possible link between the macro phenomena and the structural changes in micro-fluctuations.

physics.plasm-ph↗

arXiv2014

Investigation of toroidal acceleration and potential acceleration forces in EAST and J-TEXT plasmas

In order to produce intrinsic rotation, bulk plasmas must be collectively accelerated by the net force exerted on them, which results from both driving and damping forces. So, to study the possible mechanisms of intrinsic rotation generation, it is only needed to understand characteristics of driving and damping terms because the toroidal driving and damping forces induce net acceleration which generates intrinsic rotation. Experiments were performed on EAST and J-TEXT for ohmic plasmas with net counter- and co-current toroidal acceleration generated by density ramping up and ramping down. Additionally on EAST, net co-current toroidal acceleration was also formed by LHCD or ICRF. For the current experimental results, toroidal acceleration was between - 50 km/s^2 in counter-current direction and 70 km/s^2 in co-current direction. According to toroidal momentum equation, toroidal electric field (E\-(\g(f))), electron-ion toroidal friction, and toroidal viscous force etc. may play roles in the evolution of toroidal rotation. To evaluate contribution of each term, we first analyze characteristics of E\-(\g(f)). E\-(\g(f)) is one of the co-current toroidal forces that acts on the plasma as a whole and persists for the entire discharge period. It was shown to drive the co-current toroidal acceleration at a magnitude of 10^3 km/s^2, which was much larger than the experimental toroidal acceleration observed on EAST and J-TEXT. So E\-(\g(f)) is one of co-current forces producing cocurrent intrinsic toroidal acceleration and rotation. Meanwhile, it indicates that there must be a strong counter-current toroidal acceleration resulting from counter-current toroidal forces. Electron-ion toroidal friction is one of the counter-current toroidal forces because global electrons move in the counter-current direction in order to produce a toroidal plasma current.

physics.plasm-ph↗