Testing a Helicon Double Layer Thruster immersed in a space-simulation chamber

The Helicon Double Layer Thruster, a new magnetoplasma thruster that accelerates ions to supersonic velocities using a current-free electric double layer, has been tested successfully for the first time inside a space-simulation vacuum chamber. Using a retarding field energy analyzer, the presence of a current-free double layer and the associated ion beam in argon have been confirmed for operating conditions of 0.297 mgs^-1 of argon, 53.3 mPa gas pressure, 100 W of radio-frequency forward power at 13.56 MHz, and a maximum axial magnetic field of 138 G. The inductively coupled plasma and ion beam formed have been characterized axially, and the measured beam velocity is about 8.7 kms^-1 for these conditions. The effect of moving the Helicon Double Layer Thruster source tube relative to the magnetic field and radio-frequency antenna is investigated, and the pressure dependence of the double layer is measured from 20 to 275 mPa and compared with a recently developed theoretical model. Ions in the Helicon Double Layer Thruster exhaust are also shown to be nonmagnetized, suggesting that ion detachment has occurred.