Conversion Of Magnetic Energy Into Kinetic Energy Of Runaway Electrons During Disruption On The J-TEXT

Plasma disruption in tokamaks is almost inevitable and catastrophic.When a large number of runaway electrons are produced to form a runaway current,part of the magnetic energy contained in plasma is transferred to the runaway current beam.For the international thermonuclear experimental reactor(ITER),magnetic energy contained in the runaway current beam up to 307 MJ under unfavorable conditions.At the termination of runaway plateau,this part of magnetic energy may be converted into kinetic energy of runaway electrons,which will aggravate the damage to the plasma-facing components(PFCs)of the device.Therefore,it is of great significance for the safe and stable operation of tokamaks to study the conversion of magnetic energy to the kinetic energy carried by runaway electrons and to explore the effective methods to transfer magnetic energy contained in runaway current beam.Based on J-TEXT tokamak device,the main work of this paper is as follows.First,the magnetic energy inside vacuum vessel and the magnetic energy flowing into the vacuum vessel during the runaway current plateau are estimated,The estimation of these two parts of magnetic energy is completed,which lays the foundation for the subsequent magnetic energy analysis.Then,the conversion of magnetic energy into kinetic energy carried by runaway electrons during current quench phase,runaway current plateau phase and the termination of runaway current plateau phase are analyzed,and the factors influencing the increase of kinetic energy carried by runaway electron at the termination of runaway current plateau are analyzed.Generally speaking,the more magnetic energy is lost inside the vacuum vessel,the larger the kinetic energy runaway electrons gain.However,in the case when the RE beam-wall strike maintains the whole termination of runaway current plateau phase,there is no obvious relationship between the magnetic energy lost in vacuum vessel and the kinetic energy carried by runaway electrons: no matter how large the magnetic energy lost in the vacuum chamber,the kinetic energy carried by runaway electrons remains at a low level.At the termination of runaway current plateau phase,with stronger average normalized magnetic fluctuation level and faster decrease of runaway current,and the increase of kinetic energy carried by runaway electrons is less obvious.Finally,the methods to transfer magnetic energy during the runaway current plateau are explored.The applied reverse toroidal electric field can reduce the magnetic energy flowing into the vacuum vessel,and the transfer efficiency can be as high as 41.35%.When the position of the runaway current beam is well-controlled,the runaway current can achieve a soft landing.The applied magnetic energy transfer coil has no obvious effect in the runaway current plateau stage,and has certain effect to transfer magnetic energy in the termination of runaway current plateau stage,and the transfer efficiency can reach 26.5%.