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|JULY 2018 FEATURE ARTICLES - THESE ARE OPEN ACCESS FOR A LIMITED TIME|
We are pleased to announce that the 2017 Impact Factor for T-PS has increased by 20% and now stands at 1.253!
A High Repetition-rate Bipolar Nanosecond Pulse Generator for Dielectric Barrier Discharge Based on a Magnetic Pulse Compression Systemby Yan Mi, Jialun Wan, Changhao Bian, Yanyuan Zhang, Chenguo Yao, and Chengxiang Li
Magnetic pulse compression (MPC) systems are suitable for generating dielectric barrier discharges (DBDs) owing to their capability of producing high-amplitude, short pulse voltage waves. This paper proposes a high-frequency, bipolar magnetic compression system to study DBD plasma characteristics. First, the principle of bipolar MPC is explained [a bipolar MPC system comprises a full bridge inverter circuit, pulse transformer (PT), and magnetic switch (MS)]. Additionally, the design of the PT and MS is described. Then, the waveform of the resistive load is tested and compared with PSpice simulation results. It was found that the nanosecond pulse generator produces a pulse on a resistor with an amplitude of 0-13 kV, a rise time of approximately 100 ns, and a repetition frequency of 0 to several kHz. Finally, this paper studies the plasma characteristics under the application of a high-frequency bipolar pulse, and the charge-voltage Lissajous figure of the discharge waveform is analyzed. Combining discharge photographs and theoretical calculation results yields the relationship between the discharge characteristics and the frequency, which enriches the theoretical study of high-frequency bipolar discharges. more...
Electron Transportation Simulation for Spacecraft Internal Charging based on Reverse Monte Carlo Methodby Kang Wang, Zhen-Long Zhang, and Li-Hua Zhu
To make an estimation of the internal charging effect caused by the high energy electrons, a high-efficient 3-D transportation simulation code for satellite has been developed based on a reverse Monte Carlo (RMC) method implemented in Geant4. Charge production distribution, dose distribution in the sensitive volume has been simulated via forward Monte Carlo (FMC) and RMC, respectively, for the same geometry construction. Simulation results show that the computing time is significantly reduced in this RMC electron transportation simulation, especially when the sensitive volume is much smaller than the entire geometry. As an example, the computing time of RMC for a sensitive volume accounting for 0.0001% in the entire structure is only 1/500 of that of FMC. Difference of the results between RMC simulation and traditional Monte Carlo simulation is less than 10%. more...
Large-scale heliospheric flux ropes are observed by in situ instruments onboard heliospheric observatories as magnetic structures embedded in interplanetary coronal mass ejections (ICMEs). They are known as the interplanetary counterpart of the coronal mass ejections (CMEs), and the main drivers of geomagnetic activity. These structures can be reconstructed by fitting an axial symmetric flux rope model to the data. By using a circular-cylindrical analytical flux rope model, the 3-D reconstruction provides information about the heliospheric orientation, geometry, magnetic field at the flux rope center, and force distribution along the radius. Other quantities that can be derived are the magnetic flux and helicity. This model is constrained by the current density distribution along the tube. Thus, this paper aims to evaluate how different current density profiles change the physical and geometrical quantities. We selected two Earth-directed ICME events from the Wind ICME catalog (wind.gsfc.nasa.gov) and fit the model parameters to the data using two model-cases with different current density profiles. In general, the orientation, geometry, magnetic field strength, relative helicity, and size seem well-defined quantities. However, in the case of the magnetic flux and number of turns, the reconstructions are more sensitive to the current density constraint. This comparative analysis of the variation of the quantity will allow us to constrain not only this model but also the coronal models and the dynamical evolution of ICMEs in the solar wind by comparing the physical quantities. more...
We present a new code designed to solve the equations of classical magnetohydrodynamics in 3-D under the effects of magnetic resistivity and heat transfer. The purpose of the code centers on the analysis of solar phenomena within the photosphere-corona region and the study of the propagation of coronal mass ejections in the interplanetary medium. We present 1-D and 2-D standard tests to demonstrate the quality of the numerical results obtained with our code. As a new code test, we include a system directly related to solar physics: the formation of a jet triggered by magnetic reconnection. The program uses high-resolution shock-capturing methods, using HLLE, HLLC, and HLLD flux formulas combined with MINMOD, MC, and reconstructors. The divergence-free magnetic field constraint is controlled using the extended generalized Lagrange multipliers method and flux-constrained transport (Flux-CT) method. Concerning the accuracy of the numerical results, we present three important cases: first, for the self-similar current sheet test, the error with respect to the exact solution is 0.13%; second, about the violation of the divergence-free magnetic field constraint, we use the blast wave test and show the constraint is of order 10 -11; and third, related to the magnetic field reconnection, the code reproduces the predicted reconnection rate for the Sweet-Parker model. more...
The Large Helical Device: Entering Deuterium Experiment Phase Toward Steady-State Helical Fusion Reactor Based on Achievements in Hydrogen Experiment Phaseby Yasuhiko Takeiri
The large helical device (LHD) is one of the world's largest superconducting helical system fusion-experiment devices. Since the start of experiments in 1998, LHD has extended its parameter regime, aiming at achievement of the reactor-relevant plasma conditions and the exploration of related plasma physics in helical-type magnetic configurations. The LHD has also demonstrated its inherent advantage for steady-state operation. Based on these leading developments of helical plasma research, LHD has progressed to the advanced research phase, that is, the deuterium experiment that started in March 2017. It is expected that plasma parameters should be extended toward more reactor-relevant regime, and the related physics research is allowed in such extended regime. Taking this opportunity, parameter extensions such as density, temperature, and steady-state operation achieved in the hydrogen experiment phase are overviewed, along with the initial highlighted results in the very first deuterium experiment campaign in 2017. The design activity of LHD-type steady-state helical fusion reactor is also briefly introduced. more...
Analytic Exploration of the Accuracy of Pierce’s Three-Wave Beam-Wave Interaction Theory of Traveling-Wave Tubesby Hai-Jian Qiu, Yu-Lu Hu, Quan Hu, Xiao-Fang Zhu, and Bin Li
As it is well known that the simplified classical Pierce’s three-wave theory can provide scaling insights into traveling-wave tube (TWT) operation for its close-form solutions, and thus becomes a useful guide for TWT design. However, the classical Pierce’s three-wave theory shows poor agreement with Lagrangian theory, so determining how to achieve a more accurately Pierce’s three-wave theory from Pierce’s four-wave theory becomes an open problem. In this paper, a more accurately revised Pierce’s three-wave dispersion relation is deduced by using an approximate treatment on the nonlinear term of the dispersion relation of Pierce’s four-wave beam-wave interaction theory. Meanwhile, the boundary conditions of classical Pierce’s three-wave theory are revised by theoretical analysis. Thus, the revised Pierce’s three-wave theory is established. The Pierce small-signal theories are compared to each other and Lagrangian theory on a set of TWT parameters which are based on a single pitch section of C- and Ku- bands TWTs. It is found that the revised Pierce’s three-wave theory agrees extremely well with Lagrangian theory and gains more accuracy than the classical Pierce’s three-wave theory in the small-signal beam-wave interaction region. Finally, the phase difference between Pierce’s four-wave theory and revised Pierce’s three-wave theory is discussed. more...
A PUBLICATION OF THE IEEE NUCLEAR AND PLASMA SCIENCES SOCIETY
|JULY 2018 | VOLUME 46 | NUMBER 7 | ITPSBD | (ISSN 0093-3813)|
|PART I OF THREE PARTS
SPECIAL ISSUE ON SELECTED PAPERS FROM THE LAWPP 2017
SPECIAL ISSUE PAPERS
SPECIAL ISSUE ON HIGH POWER MICROWAVE GENERATION 2018
SPECIAL ISSUE PAPERS
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