Numerical studies for plasmas of a linear plasma device HIT-PSI with geometry modified SOLPS-ITER

The HIT-PSI is a linear plasma device built for physically simulating the high heat flux environment of future reactor divertors to test/develop advanced target plate materials.In this study,the geometry-modified SOLPS-ITER program is employed to examine the effects of the magnetic field strength and neutral pressure in the device on the heat flux experienced by the target plate of the HIT-PSI device.The findings of the numerical simulation indicate a positive correlation between the magnetic field strength and the heat flux density.Conversely,there is a negative correlation observed between the heat flux density and the neutral pressure.When the magnetic field strength at the axis exceeds 1 tesla and the neutral pressure falls below 10 Pa,the HIT-PSI has the capability to attain a heat flux of 10 MW·m-2 at the target plate.The simulation results offer a valuable point of reference for subsequent experiments at HIT-PSI.

Improvement of atmospheric jet-array plasma uniformity assisted by artificial neural networks

Atmospheric pressure plasma jet(APPJ)arrays have shown a potential in a wide range of applications ranging from material processing to biomedicine.In these applications,targets with complex three-dimensional structures often easily affect plasma uniformity.However,the uniformity is usually crucially important in application areas such as biomedicine,etc.In this work,the flow and electric field collaborative modulations are used to improve the uniformity of the plasma downstream.Taking a two-dimensional sloped metallic substrate with a 10°inclined angle as an example,the influences of both flow and electric field on the electron and typical active species distributions downstream are studied based on a multi-field coupling model.The electric and flow fields modulations are first separately applied to test the influence.Results show that the electric field modulation has an obvious improvement on the uniformity of plasma while the flow field modulation effect is limited.Based on such outputs,a collaborative modulation of both fields is then applied,and shows a much better effect on the uniformity.To make further advances,a basic strategy of uniformity improvement is thus acquired.To achieve the goal,an artificial neural network method with reasonable accuracy is then used to predict the correlation between plasma processing parameters and downstream uniformity properties for further improvement of the plasma uniformity.An optional scheme taking advantage of the flexibility of APPJ arrays is then developed for practical demands.

Special issue on selected papers from HVDP 2018

This special issue contains the selected papers from the 2018 National Conference on High Voltage and Discharge Plasmas (HVDP 2018) in Nanjing, China, 12-14October, hosted by the Committee of Plasmas and Applications, China Electrotechnical Society. Over 650 participates from more than 150 universities, research institutes, and enterprises all over China attended the conference and delivered 458presentations, including 32 invited talks, 260 oral presentations and 196 posters.This well-established event provides a full scale assembly of contributions from areas of high voltage, pulsed power technology as well as basic theories and applications of discharge plasma.

Experimental and numerical studies on the receiving gain enhancement modulated by a sub-wavelength plasma layer

A novel technique based on sub-wavelength plasma structure effects on enhancement of RF communication signals on a receiving antenna is carried out in this paper in laboratory experiments and analyzed by corresponding numerical simulations.Considerable intensification on receiving signal gain up to -10 d B in comparison with that without the plasma modulation is observed experimentally in -1 GHz RF band,with an effective enhancement bandwidth of -340 MHz and the fractional bandwidth of -34%.Then,the optimal modulation parameters of plasma are further studied by a numerical simulation.It is shown that the number density,the layer thickness,and the collision frequency of the plasma,as well as the relative distance between the plasma layer and antenna synergistically affect the modulation.Compared to the metallic antenna with the same overall dimension,the modulated antenna covered by the subwavelength plasma structure features higher receiving efficiency and lower radar cross section in the studied RF band.The mechanism of the reception enhancement is further revealed by analyzing characteristics of electromagnetic scattering and electric field distribution in the subwavelength plasma layer.The results then exhibit scientific significance and application potential of sub-wavelength plasma modulation on compact receiving antennas with higher performance and better feature of radar stealth.

Effect of attack angle on the electromagnetic wave transmission characteristics in the hypersonic plasma sheath of a re-entry vehicle

The attack angle may greatly affect the hypersonic plasma sheaths around the re-entry vehicle,thereby affecting the transmission characteristics of electromagnetic(EM)waves in the sheaths.In this paper,we propose an integrated three-dimensional(3D)model with various attack angles and realistic flying conditions of radio attenuation measurement C-II(RAM C-II)re-entry tasks for analyzing the effect of the attack angle on the transmission characteristics of EM waves in the sheaths.It is shown that the electron density and collision frequency of the sheath on the windward side can be increased by an order of magnitude with the increase of the attack angle.Meanwhile,the thickness of the sheath on the leeward side is increased where the electron density and collision frequency are reduced.The EM waves are mainly reflected on the windward plasma sheath due to the cutoff effect,and the radio-frequency(RF)blackout is mitigated if the antenna is positioned on the leeward side.Thus,by planning the trajectory properly and installing the antenna accordingly during the re-entry,it is possible to provide an approach for mitigation of the RF blackout problem to an extent.