Magnetic Ion Beam Deflection in the Helicon Double-Layer Thruster

Abstract

Transverse magnetic fields (along the x-axis, transverse to the z-axis) are applied to a helicon double-layer plasma to investigate the effect on the ion beam accelerated in the electric field of the double-layer. The 250 W radio frequency argon plasma is operated at a pressure of 0.04 Pa in a diverging magnetic field with a maximum of ∼140 G along the primary axis (z-axis). The diverging magnetic field is produced by two primary solenoids aligned coaxially along the z-axis. Introducing an additional solenoid mounted along the x-axis, perpendicular to the z-axis, generates a 0 to 250 G magnetic field at its center (0 to 55 G at the z-axis) as the supplied current is swept from 0 to 6 A. Spatial measurements of the ion beam downstream of the double-layer using a retarding field energy analyzer reveal deflection of the ion beam vector, with the angle of deflection increasing with increasing transverse solenoidal current. Deflection of the ion beam is observed for both transverse solenoidal polarities, with the polarity determining the direction of ion beam deflection. Under the influence of the transverse magnetic field, the ion beam vector is demonstrated to be deflected in the x-z plane as a function of the transverse solenoidal polarity. The ion beam is measured to be deflected by up to -26 and 14 deg for the transverse polarity pointing out of and into the thruster, respectively, where positive deflection is defined in the positive x-direction.