Helicon plasma in a magnetic shuttle

The defnition of a magnetic shuttle is introduced to describe the magnetic space enclosed by two magnetic mirrors with the same feld direction and high mirror ratio. Helicon plasma immersed in such a magnetic shuttle (mirror ratio 5) that can provide the confnement of charged particles is modeled using an electromagnetic solver. The perpendicular structure of the wave feld along this shuttle is given in terms of stream vector plots, showing a signifcant change from midplane to ending throats, and the vector feld rotates and forms a circular layer that separates the plasma column radially into core and edge regions near the throats. The influences of the driving frequency (f = 6.78 MHz–40.68 MHz), plasma density (nemax = 1016 m-3 to 1019 m-3), and feld strength (B0max = 0.017 T–1.7 T) on the wave feld structure and power absorption are computed in detail. It is found that the wave energy and power absorption decrease for increased driving frequency and reduced feld strength and increase signifcantly when the plasma density is above a certain value. The axial standing-wave feature always exists, due to the interference between forward and reflected waves from ending magnetic mirrors. Distributions of wave energy density and power absorption density all show a shrinking feature from midplane to ending throats, which is consistent with the nature of the helicon mode that propagates along feld lines. Theoretical analysis based on a simple magnetic shuttle and the governing equation of helicon waves shows consistency with computed results and previous studies. This hypothetical work is a valuable to guide the helicon physics prototype experiment, which is designed for the fundamental wave–particle interaction study in helicon plasma, to achieve high plasma density andenergy absorption effciency.