Wang Shiqing

Essential Characteristics of Plasma Antennas Driven by One-ended Surface Wave

Based on the principle that one-ended electromagnetic surface wave can drive a plasma antenna, the relation between the effective length of an antenna column and the applied radio frequency (RF) power was studied both theoretically and experimentally. The density distribution along the antenna column as well as the electron temperature in different conditions were investigated. The characteristics of the reception of local frequency modulated (FM) electromagnetic wave by the plasma antenna were compared with that by a copper antenna with same dimensions. The results show that it is feasible to take plasma antennas as receiving ones.

Array of HgI2 detectors on the HL-1M Tokamak

An array of seven HgI2 detectors, which are suitable for detecting the time and space evolution of the x-ray radiation flux and energy spectrum in the range between 15–150 keV relevant to suprathermal electron and runaway electrons was installed on the HL-1M Tokamak (R0=1.02 m, a=0.26 m, BT=3.5 T, IP=350 kA, ne=3–6×1013 cm−3, Te=0.8–1.5 keV). Our iodine mercury (HgI2) semiconductor detectors possess the properties of low noise level, high detection efficiency, high counting rate, high energy resolution, and working at room temperature. Every detector is a high quality, high purity detector cut out of a big size HgI2 crystal. A new type of multichannel energy spectrometer with a high speed acquisition system was developed. Therefore, the spatial and temporal distribution of the x-ray energy spectrum induced by thermal and superthermal electrons can be observed.

Essential Characteristics of Plasma Antennas Filled with He-Ar Penning Gases

Based on the essential theory of Penning gases, the discharge characteristics of He-Ar Penning gases in insulating tubes were analyzed qualitatively. The relation between the effective length of an antenna column filled with He-Ar Penning gases and the applied radio frequency (RF) power was investigated both theoretically and experimentally. The distribution of the plasma density along the antenna column in different conditions was studied. The receiving characteristics of local frequency modulated (FM) electromagnetic waves by the plasma antenna filled with He-Ar Penning gases were compared with those by an aluminum antenna with the same dimensions. Results show that it is feasible to take plasma antennas filled with He-Ar Penning gases as receiving antennas.

Effect of Anode Magnetic Shield on Magnetic Field and Ion Beam in Cylindrical Hall Thruster

Numerical simulation of the effect of the anode magnetic shielding on the magnetic field and ion beam in a cylindrical Hall thruster is presented. The results show that after the anode is shielded by the magnetic shield, the magnetic field lines near the anode surface are obviously convex curved, the ratio of the magnetic mirror is enhanced, the width of the positive magnetic field gradient becomes larger than that without the anode magnetic shielding, the radial magnetic field component is enhanced, and the discharge plasma turbulence is reduced as a result of keeping the original saddle field profile and the important role the other two saddle field profiles play in restricting electrons. The results of the particle in cell (PIC) numerical simulation show that both the ion number and the energy of the ion beam increase after the anode is shielded by the magnetic shield. In other words, the specific impulse of the cylindrical Hall thruster is enhanced.

Study on Propagation Characteristics of Plasma Surface Wave in Medium Tube

Axial propagation characteristics of the axisymmetric surface wave along the plasma in the medium tube were studied. The expressions of electromagnetic field inside and outside the medium tube were deduced. Also, the impacts of several factors, such as plasma density, signal frequency, inner radius of medium tube, collision frequency, etc., on plasma surface wave propagation were numerically simulated. The results show that, the properties of plasma with higher density and lower gas pressure are closer to those of metal conductor. Furthermore, larger radius of medium tube and lower signal frequency are better for surface wave propagation. However, the effect of collision frequency is not obvious. The optimized experimental parameters can be chosen as the plasma density of about 1017 m−3 and the medium radius between 11 mm and 19 mm.