Development and characteristics of a fast gas valve for plasma-jet-driven magneto-inertial Fusion (PJMIF)

To provide rapid gas injection for the plasma gun developed at the CUE of ShanghaiTech University, a new fast gas valve activated by eddy currents has been designed and tested on an experimental facility. A 7075 aluminum flyer plate is used to control the gas injection process. A saucer spring is designed to provide pre-compression force and back force on the flyer plate. Four displacement sensors are installed vertically to the flyer plate to measure distances at four equally distributed points. A capacitance diaphragm gauge is used to measure pressure changes in the vacuum chamber. The main characteristics of the fast gas valve are as follows: (1) the open-close time (the opening to complete closure time) is less than 230 μs, with a minimum value of 102 μs; (2) a saucer spring is designed to provide pre-compression force on the flyer plate, which demonstrates better performance than conventional spiral springs; (3) the gas mass dispensed by the fast gas valve is highly stable, with an average variation of less than 1%; (4) the maximum variation in displacements at the four measuring points on the flyer plate is less than 7%. The fast gas valve has been tested with argon gas on the plasma gun and has shown good performance.