Optimizing Directional Power Deposition of Antenna in Radio Frequency Excited Helicon Plasma Thruster

Abstract

Plasma thruster operating with high-density helicon source is expected to mitigate the problems of the finite lifetime of electric thrusters and shows a possibility to be incorporated in spacecraft for long-duration interplanetary missions. Helicon wave is a low-frequency whistler wave, where the frequency $\omega$ lies in between lower hybrid frequency $\omega_{LH}$ and electron cyclotron frequency $\omega_{c}$ . The generated electromagnetic wave from helicon antenna penetrates to the plasma and transfer energy to the particles. In helicon thruster with lower rf power 1 – 2 kW, relatively fully ionized plasma $\eta\geq 10^{14}cm^{3}$ can be achieved [1], [2]. The high plasma resistance and power deposition are the key factors for the optimal design of helicon antenna [3]. This research work investigates the directional power deposition of nagoya, half helix, and a single loop antenna at a driven frequency, $f=13.56$ MHz. A wide range of plasma densities, $n_{0}$ from 1011cm−3 to 101cm−3 and magnetic field strength, $B_{0}=0.3T$ was taken into account. HELIC code [4]–[7] is used for designing rf plasma sources. Plasma density profile has significant effects on antenna plasma coupling. The optimal combination of the plasma density, magnetic field for which the rf power deposition maximize presented.