Particle Confinement Property In The Cusp-mirror Field Of A Compact Fusion Reactor

In this paper,the physical mechanism of the particle confinement in a new fusion device named Compact Fusion Reactor(CFR)with a hybrid cusp-mirror magnetic field is studied by employing test particle simulations,which is first proposed by Lockheed Martin Corporation.First,the magnetic configurations of Compact Fusion Reactor and cascade magnetic mirror device have been built.And differing from the cascade magnetic mirror configuration,in the weak magnetic region of the CFR's center can form a magnetic well structure.With observation of single particle trajectories,the adiabatic region and non-adiabatic region are found in the CFR's magnetic configuration.In the non-adiabatic region,due to the magnetic field-free space existing,the particles are scattered stochastically and not directly guided into the loss cone,unlike the particles around fixed magnetic lines in the adiabatic region,which decrease the particle loss rate.The CFR's configuration,combining advantages of cusp-magnetic configuration and mirror-magnetic configuration,leads to confine particles longer than cascade magnetic mirror's.Then,considering the neutral beam particles are injected to the core area,namely,the magnetic well,using single particle mode to calculate the loss-rate after a certain amount of time.The results show that the CFR's configuration,combining advantages of cusp-magnetic configuration and mirror-magnetic configuration,leads to confine particles longer than cascade magnetic mirror's.This phenomenon may have relevance to the construction of advanced magnetic-confinement devices.Meanwhile,three ways of dispersing the Newton-Lorentz equation in single particle mode have been used,they are centered-difference Algorithm with leap-frog pattern,Fourth-order Runge-Kutta Algorithm and Boris Algorithm,respectively.Runge-Kutta Algorithm's results show energy dissipation while we emulate a long-running process,and the longer the simulation is,the more particles loss.Besides,the dissipative phenomena get worse in the large B-gradient configuration such as CFR than a uniform magnetic field.However,the other two methods' results shows that the errors of energy are limited in a small extent all the time,albeit with only second-order accuracy.Simulations show that the centered-difference Algorithm and Boris method can ensure conservation of energy.