Enhancing Confinement and Acceleration of Cathodic Plasma Plume by Using Electro-magnetic Nozzle

The concept of the magnetic nozzle (MN) is used for accelerating the plasma plume produced from the resonance-excited plasma source such as ECR and Helicon source for propulsive application. [1-4] Yet, the evaluation from MHD theory indicates an upper limit for the conversion of plasma internal energy (IE) to the kinetic energy (KE) before the occurrence of plasma detachment. A new concept, a.k.a. the electromagnetic nozzle (EMN), is proposed to enhance the conversion of plasma IE. [5] The idea is to introduce a positively biased ring-electrode to regulate the electric potential around the MN exit. This can enhance the dissipation of electron KE to the ionization processes as well as reshaping the potential gradience for plasma acceleration.

The EMN is demonstrated with a gridded hollow cathode and with argon as working gas. [5] The measurement of near-field plasma is performed with a Langmuir probe and Faraday probe. The formation of virtual cathode on the axis of the plume is observed when the B field at the throat is larger than 50 G, which indicates effective electron confinement. Ion flux density is greatly enhanced when the positive bias is applied on ring-electrode. The results prove the concept of EMN on plasma confinement and acceleration for propulsive applications.