A magnetic measurement system consisting of magnetic probes and flux loops for spherical tokamak SUNIST, is uniquely designed due to the strongly shaped plasma cross section and the narrow space near the central solen...A magnetic measurement system consisting of magnetic probes and flux loops for spherical tokamak SUNIST, is uniquely designed due to the strongly shaped plasma cross section and the narrow space near the central solenoid. Plasma equilibrium reconstruction with the current filament method is performed to determine the number and positions of the magnetic probes and flux loops, as well as their design precision required.展开更多
The goal of the Sino-United Spherical Tokamak (SUNIST) at Tsinghua University is to extend the understanding of toroidal plasma physics at a low aspect ratio (R/a≈1.3) and to demonstrate a maintainable target plasma ...The goal of the Sino-United Spherical Tokamak (SUNIST) at Tsinghua University is to extend the understanding of toroidal plasma physics at a low aspect ratio (R/a≈1.3) and to demonstrate a maintainable target plasma by non-inductive startup. The SUNIST device is designed to operate with up to 13 kA of ohmic heating field current, and to 0.15 T of toroidal field at 10 kA of discharge current. All of the poloidal fields can provide 30 mVs of Volt-seconds transformer. Experimental results of plasma startup show that SUNIST has remarkable characteristics of high ramp rate (dIp/dt≈50 MA/s ), high normalized current In of about 2.8 (In = Ip/αBt), and high-efficiency (Ip/Irod ≈0.4) production of plasma current while operating at a low toroidal field. Major disruption phenomena have not been observed from magnetic diagnostics of all testing shots. Initial discharges with 52 kA of plasma current (exceeding the designed value of 50 kA), 2 ms of pulse length and 50 MA/s of ramp rate have been achieved easily with pre-ionized filament.展开更多
The gas puffing performance plays a key role in repeatable discharges in the Sino- UNited Spherical Tokamak （SUNIST） experiments. In this paper, temporal evolution of the gas pressure in the vacuum vessel and the de...The gas puffing performance plays a key role in repeatable discharges in the Sino- UNited Spherical Tokamak （SUNIST） experiments. In this paper, temporal evolution of the gas pressure in the vacuum vessel and the dependence of the repeatability of plasma discharges on different timing arrangements between the gas puffing pulse and the Ohmic field have been experimentally investigated. The results show that, after a fast rising phase, the gas pressure becomes quasi-stationary. In the regime of the discharges being started up when the gas pressure has already reached the quasi-stationary state for about 37 ms, an improved repeatability of the plasma discharges is achieved.展开更多
Control of the vertical instability of the plasma in the SUNIST spherical tokamak is studied. A proportional-derivative （PD） position controller is employed in a control system which consists of a massless plasma, a...Control of the vertical instability of the plasma in the SUNIST spherical tokamak is studied. A proportional-derivative （PD） position controller is employed in a control system which consists of a massless plasma, active coils and a passive conducting vessel. Stability conditions axe determined and the feedback control with different combinations of both active and passive coils, available on SUNIST, is emphasized. The simulation results are also discussed.展开更多
Internal reconnection event （IRE）, which is characterized by a perturbation in plasma current Ip, loop voltage Vloop, Hα radiation and magnetic perturbation dBp, was observed in the SUNIST experiment. It is found t...Internal reconnection event （IRE）, which is characterized by a perturbation in plasma current Ip, loop voltage Vloop, Hα radiation and magnetic perturbation dBp, was observed in the SUNIST experiment. It is found that, the fluctuation before IREs is characterized by a structure of m= 2/n = 1, then changes to m = 4/n = 1 during the IREs; and, after IREs, the mode number changes to m = 3/n = 1. An analysis in the evolution of equilibrium parameters during IREs shows that a positive spike appears in the evolution of the plasma＇s elongation and a negative spike in the poloidal beta of plasma. A collapse in the pressure profile, corresponding to the occurrence of IREs, is also found.展开更多
基金National Science Foundation of China(No.10535020)the Foundation for the Authors of National Excellent Doctoral Dissertation of China(No.200456)
文摘A magnetic measurement system consisting of magnetic probes and flux loops for spherical tokamak SUNIST, is uniquely designed due to the strongly shaped plasma cross section and the narrow space near the central solenoid. Plasma equilibrium reconstruction with the current filament method is performed to determine the number and positions of the magnetic probes and flux loops, as well as their design precision required.
基金Improving Tsinghua University of China to Top-ranking Foundation
文摘The goal of the Sino-United Spherical Tokamak (SUNIST) at Tsinghua University is to extend the understanding of toroidal plasma physics at a low aspect ratio (R/a≈1.3) and to demonstrate a maintainable target plasma by non-inductive startup. The SUNIST device is designed to operate with up to 13 kA of ohmic heating field current, and to 0.15 T of toroidal field at 10 kA of discharge current. All of the poloidal fields can provide 30 mVs of Volt-seconds transformer. Experimental results of plasma startup show that SUNIST has remarkable characteristics of high ramp rate (dIp/dt≈50 MA/s ), high normalized current In of about 2.8 (In = Ip/αBt), and high-efficiency (Ip/Irod ≈0.4) production of plasma current while operating at a low toroidal field. Major disruption phenomena have not been observed from magnetic diagnostics of all testing shots. Initial discharges with 52 kA of plasma current (exceeding the designed value of 50 kA), 2 ms of pulse length and 50 MA/s of ramp rate have been achieved easily with pre-ionized filament.
基金supported by National Natural Science Foundation of China(Nos.10990214,11175103,11261140327 and 11075092)Ministry of Science and Technology(MOST)of China(Nos.2013GB112001 and 2010GB107002)Tsinghua University Initiative Scientific Research Program
文摘The gas puffing performance plays a key role in repeatable discharges in the Sino- UNited Spherical Tokamak （SUNIST） experiments. In this paper, temporal evolution of the gas pressure in the vacuum vessel and the dependence of the repeatability of plasma discharges on different timing arrangements between the gas puffing pulse and the Ohmic field have been experimentally investigated. The results show that, after a fast rising phase, the gas pressure becomes quasi-stationary. In the regime of the discharges being started up when the gas pressure has already reached the quasi-stationary state for about 37 ms, an improved repeatability of the plasma discharges is achieved.
基金supported by National Natural Science Foundation of China (No.10535020)the Foundation for Authors of National Excellent Doctoral Dissertations of China (No.200456)
文摘Control of the vertical instability of the plasma in the SUNIST spherical tokamak is studied. A proportional-derivative （PD） position controller is employed in a control system which consists of a massless plasma, active coils and a passive conducting vessel. Stability conditions axe determined and the feedback control with different combinations of both active and passive coils, available on SUNIST, is emphasized. The simulation results are also discussed.
基金supported by National Natural Science Foundation of China(Nos.10405014,10990214)MOST of China(Nos.2009GB105002 and 2008GB717804)in part by the JSPS-CAS Core-University program in the field of 'Plasma and Nuclear Fusion'
文摘Internal reconnection event （IRE）, which is characterized by a perturbation in plasma current Ip, loop voltage Vloop, Hα radiation and magnetic perturbation dBp, was observed in the SUNIST experiment. It is found that, the fluctuation before IREs is characterized by a structure of m= 2/n = 1, then changes to m = 4/n = 1 during the IREs; and, after IREs, the mode number changes to m = 3/n = 1. An analysis in the evolution of equilibrium parameters during IREs shows that a positive spike appears in the evolution of the plasma＇s elongation and a negative spike in the poloidal beta of plasma. A collapse in the pressure profile, corresponding to the occurrence of IREs, is also found.
