Design And Test Of Gas Injection Strategy For FRC Plasma Device

Controllable nuclear fusion energy is the ultimate energy source known to mankind to solve the future energy crisis.It fundamentally meets human pursuits of energy‘s security,efficiency,cleanliness and sustainability.Up to now,the theory of magnetic confinement and inertial confinement,which are two mainstream controllable fusion approaches,has made great progress.However,due to the high construction cost of their reactor,more and more researchers have begun to explore economic approaches to realize fusion.Represented by the field-reversed configuration(FRC),the magnetic inertial confinement has great advantages in this respect.In order to carry out related research,Huazhong University of Science and Technology has also begun the development of magnetic compression field-reversed configuration(MCFRC)plasma device.MCFRC device is mainly composed of three parts.There are two FRC plasma forming region on the both sides of the device,and a collision fusion region in the center.The FRC plasma is first generated in the formation region,and then merged into the central region.In order to improve the plasma's quality,the distribution of neutral gas in the device is very important.The FRC plasma in the device formation region is generated by ?-pinch.Related studies have shown that in its pre-ionization,the gas near the wall of the vacuum chamber is the easiest and the first to be ionized.Therefore,if radial gas distribution is controlled to make more gas distributed near the wall than near the axis,the efficiency of the pre-ionization may be increased.In addition,the neutral gas in the central region can cool the injected plasma,which may result in a parameter decrease in the plasma.Therefore,if the distribution of the gas in the axial direction is controlled during gas injection,so that he neutral gas in the central region is reduced as much as possible,and then the quality of the FRC plasma generated by the collision-merging may be improved effectively.In summary,the design of the gas injection strategy is related to the results of the FRC plasma experiment,therefore,it must be carefully considered during the design phase of the device.The design and test of gas injection strategy for FRC plasma device is described in this paper.Due to the difficulty in simulation work,the paper conducts relevant research through experiments.The time from the initial injection to the pre-ionization is only a few milliseconds,so the hot cathode ionization gauge is utilized to monitor the gas pressure change during experiment.In addition,a pulse solenoid valve with fast response time(<200 ?s)and sufficient gas injection volume(>1000 Pa·L)is adopted to inject sufficient gas into the forming region before the neutral gas diffuses to the central region.To further study the influence of gas injection position on gas distribution,an experimental gas injection test platform was fabricated.Gas pressure distribution results under two gas injection strategies,i.e.axis injection and radial injection,are measured and discussed in detail.The consistency and reliability of results demonstrates the axis gas injection strategy can meet the requirements of gas injection system of FRC device...