Simulations of the Characteristics of the Entropy Mode in Dipole-Magnetic-Confined Plasmas.

Plasmas confined in a dipole magnetic field widely exist in both space and laboratories, and this kind of plasma draws much attention from researchers both in plasma physics and in space science. In this paper, the characteristics of the collisionless electrostatic instability of the entropy mode in a dipole-magnetic-confined plasma are simulated with the linear gyrokinetic model. It is found that the entropy mode can be generated in dipole-magnetic-confined plasmas, and there are two typical stages of the entropy mode, with another transitional stage at different values of η. The main instability changes from the ion diamagnetic drift to the electronic diamagnetic drift as η becomes larger. In addition, the MHD mode predicts that the most stable point is at η~2/3 when k⟂ρi << 1. However, we find that η and k⟂ρi are coupled with each other, and the most stable point of the mode moves gradually to η~1 as k⟂ρi increases. There is a peak value for the entropy mode growth rate around k⟂ρi~1.0, and more complicated modes are induced so that the dispersion relation has been changed when the driving force of the plasma pressure gradient effect is obvious. For example, the characteristics of the interchange-like modes gradually emerge when the driving effect of the plasma pressure becomes stronger. Further investigations should be taken to reveal the characteristics of the entropy mode in magnetospheric plasmas.

An 18.3 MJ charging and discharging pulsed power supply system for the Space Plasma Environment Research Facility (SPERF): The subsystem for the magnetic perturbation coils.

The mechanism of acceleration, loss, and wave-particle interaction of energetic particles in the magnetosphere is a research content of the Space Plasma Environment Research Facility, which is being built as a user facility at the Harbin Institute of Technology in China. Two magnetic perturbation coils are used to simulate the magnetic storm distortion and excite Alfvén wave perturbation. A capacitor-based pulsed power supply (PPS) system with a modular design is developed to excite the magnetic perturbation coils to generate the required amplitude and duration of the magnetic field. The two magnetic perturbation coils are the CRDI coil and CRDII coil and are excited by one set of PPSs. The PPS for the CRDI coil consists of two modules and can provide a pulsed current of no less than 132 kA at 0.12 ms when the charging voltage is 20 kV, and the duration of the pulsed current from the peak to 10% of the peak is no more than 0.7 ms. The PPS for the CRDII coil consists of five modules and can provide a pulsed current of no less than 16 kA at 0.45, 0.65, 0.8, 0.95, and 1.1 ms, and the duration of the pulsed current from the peak to 10% of the peak is no more than 4.5 ms. The detailed design of the PPSs has been discussed in this paper, and the discharge test of the PPSs is carried out to verify the design of the PPSs.

An 18.3-MJ charging and discharging pulsed power supply system for the Space Plasma Environment Research Facility (SPERF): The subsystem for the magnetosheath coils.

3D asymmetric magnetic reconnection is an important investigation of the Space Plasma Environment Research Facility, which is being built as a user facility at the Harbin Institute of Technology in China. Four magnetosheath coils, which consist of Poloidal Field (labeled PF) coils and Toroidal Field (labeled TF) coils, are used to generate the magnetic field and plasma environment for the reconnecting experiment. A capacitor-based pulsed power supply (PPS) system with a modular design is developed to excite the magnetosheath coils to generate the required amplitude and duration of the magnetic field. The PPS system includes the PF PPS and TF PPS, which include four sets of PPSs, respectively. Each set of PF PPS and TF PPS consists of nine modules and four modules, respectively, and each module consists of a charge and discharge unit. The PF PPS can provide a pulsed current of no less than 360 kA for the corresponding PF coil at 0.11 ms when the charging voltage is 20 kV, and the duration of the pulsed current from the peak to 10% of the peak is no more than 0.6 ms. The TF PPS can provide a pulsed current of no less than 200 kA for the corresponding TF coil at 0.08 ms when the charging voltage is 20 kV, and the duration of the pulsed current from the peak to 10% of the peak is no more than 1.6 ms. The detailed design of the PPS has been discussed in this paper, and the detailed design of the main components in the discharge unit of the PPS is also given in this paper. Finally, the discharge tests of all the PPSs are carried out to verify the design of the PPSs, and the results of the PPSs in discharge tests indicate that all the PPSs meet the design requirements.

The magnet system of the Space Plasma Environment Research Facility (SPERF): Parameter design and electromagnetic analysis.

A magnet system is used in the SPERF to create the magnetic field configuration for simulating the space plasma environment. In this paper, the parameters of the system are designed to achieve the target fields needed by the scaling laws, and the electromagnetic analysis has been performed to validate the results. A procedure to obtain the parameters is proposed based on the investigation into the physical and technological constraints. The vacuum magnetic fields for studying the 3D magnetic reconnection at the magnetopause, Earth's magnetosphere, and 3D magnetic reconnection driven by a plasma gun are computed. In addition, the engineering complexity is reviewed in brief. This research is crucial to the construction of the SPERF, and it is valuable to designing the magnets applied in other fields.

An 18.3 MJ charging and discharging pulsed power supply system for the Space Plasma Environment Research Facility (SPERF): The subsystem for the dipole coil.

The Space Plasma Environment Research Facility (SPERF) currently under construction at the Harbin Institute of Technology in China is a user facility dedicated to studying space plasma physics on the ground. A coil system of the SPERF consists of seven types of coils, which are used to generate the magnetic fields and plasma required by the physical experiments. A dipole coil of the coil system works with four magnetosheath coils (flux cores) to build the magnetic fields resembling that of the Earth and solar wind. A capacitor-based pulsed power supply (PPS) system with a modular design is developed to excite the dipole coil to generate a magnetosphere-like magnetic field required by the magnetopause magnetic reconnection experiment. The PPS of the dipole coil has a longer pulse duration and more energy than that of other coils in the coil system, it delivers a pulsed current with a peak of more than 18 kA, and the duration of the current is not less than 95% of the peak over 10 ms to the dipole coil when the charging voltage is not less than 20 kV. The detailed design of the PPS is discussed in this paper, and the discharge test of the PPS is carried out to verify the design of the PPS.

An 18.3 MJ charging and discharging pulsed power supply system for the Space Plasma Environment Research Facility (SPERF): The subsystem for the magnetopause shape control coils.

The Space Plasma Environment Research Facility currently under construction at the Harbin Institute of Technology in China uses four magnetosheath coils (flux cores) and a dipole coil to generate the magnetic field required for the study on the magnetopause magnetic reconnection. Two groups of magnetopause shape control coils (labeled CK coils) are used to slightly adjust the magnetic field distribution on the magnetopause. A capacitive pulsed power supply (PPS) system with a modular design is developed to excite CK coils. The PPS system consists of six sets of PPS with the same principle and structure, which are used to excite six sub-coils of the CK coils, respectively. Each set of PPS consists of ten modules and one local controller, and each module consists of a charger and discharge unit. Each set of PPS can provide a pulsed current of no less than 400 kA for the corresponding sub-coil at 0.11 ms when the charging voltage is 20 kV, and the duration of the pulsed current from the peak to 10% of the peak is no more than 0.6 ms. The detailed design of the PPS is discussed in this paper, and the discharge test of the PPS is carried out to verify the design of the PPS. Because there are acquisition and control devices in the discharge unit, the electromagnetic interference immunity design is also discussed to ensure the normal operation of the PPS.

An 18.3 MJ charging and discharging pulsed power supply system for the Space Plasma Environment Research Facility (SPERF): Modular design method and component selection.

The capacitor-based pulsed power supply (PPS) system is an important subsystem of the Space Plasma Environment Research Facility being built as a user facility at Harbin Institute of Technology in China. It has been developed with a modular design to drive magnetic coils to generate magnetic fields and plasma for the physical experiments. In this paper, the modular design and component selection are proposed based on a calculation of parameter ranges of components and the number of modules followed by a simulation and an engineering test. Both the simulation and test results show the feasibility of the selected components and the number of modules to meet the designing requirements of the PPS.

An 18.3 MJ charging and discharging pulsed power supply system for the Space Plasma Environment Research Facility (SPERF). I. The overall design.

The Space Plasma Environment Research Facility (SPERF) is a new ground-based experimental device for fundamental research studies on space plasma currently under construction at Harbin Institute of Technology in China. Scientific objectives of the SPERF include studying the asymmetric reconnection dynamics relevant to the interaction between the interplanetary and magnetospheric plasmas, reproducing the inner magnetosphere to simulate the processes of trapping, acceleration, and transport of energetic charged particles restrained in a dipole magnetic field configuration, and revealing the physical mechanism of the dipolarization front in the magnetotail. The device comprises a vacuum chamber, 11 coils consisting of 18 groups of sub-coils that are independently programmablely energized, and the plasma source system to provide the magnetic field and the plasma required by the physical experiments. Thus, each of these 18 groups of sub-coils requires a separate pulsed power supply; furthermore, the 18 pulsed power supplies constitute the pulsed power supply system of the SPERF of which the total storage energy is up to 18.3 MJ, and the technical challenges have to be overcome. The power supply energizing a dipole field coil (labeled OJC coil) wired by the copper wire to provide a dipole magnetic field is the most energetic power supply (labeled OJC power supply) with a 2.42 MJ, 16.8 mF capacitor bank charged to 20 kV. The OJC power supply delivers a current with a peak of 18 kA for a rise time of ∼26.69 ms, and the duration of the current is not less than 95% of the peak over 10 ms to the OJC coil. Meanwhile, the most challenging power supply is the power supply labeled poloidal field power supply with a 5.04 mF capacitor bank charged to 20 kV, which provides the excitation current for the load coil set with the current not less than 360 kA at the typical time of 0.11 ms to produce the sufficient growth of the magnetic field that the experiments need. In this paper, the overall design of the pulsed power supply system, the design concept of the modularization, and the principle selection basis of the key components are presented. The technical details of each power supply will be demonstrated in the future.