Research On Hollow Cathode-Hall Thruster Coupling Charateristics

Experimental investigation was conducted on the influence of environmentalfactors produced by Hall Effect Thruster(HET) on hollow cathode dischargecharacteristics, as well as characteristic parameters of plasma bridge(couplingzone) under different hollow cathode and HET operation parameters.Magnetic field was introduced into classical diode discharge configuration ofhollow cathode and divided into two groups regarding parallel magnetic field andperpendicular magnetic field respectively. The macro variation of hollow cathodedischarge characteristics was measured and micro probe diagnostics of hollowcathode plume inside parallel magnetic field was included. Results indicate thatlocal magnetic field is of significant influence to hollow cathode dischargecharacteristics, in which perpendicular magnetic field raises discharge impedancewhile parallel magnetic field lowers impedance, suppress discharge oscillationand shorten ignition time consumption. The infection area of parallel magneticfield extends from downstream hollow cathode plume into upstream emitter zone,though in different patterns involving sheath structure, drift diffusion process andbackpressure changes.Axial and circumferential characteristic parameters of plasma bridge wereacquired and influencing factors were investigated. Data implies that as the lowimpedance channel of hollow cathode electrons, a structure of distributarysurface was found inside, the EXB drifting of which induces thruster plumeasymmetry. Great excitation and ionization occurs on the magnetic mirror ofplasma bridge, and low impedance area was accidentally discovered local to thesurface of outer magnetic pole. The choice of cathode local magnetic inductionline is of great relevance to the position and width of distributary surface andthruster plume asymmetry, providing a entry point of active control of plumeelectric potential. Operation parameters of HET influences the self-consistentEXB transport process from distributary surface to channel, downstream plumeand electron fast channel local to outer magnetic pole, providing reference formatching principle of hollow cathode and local magnetic field in differentoperation point. Furthermore, the validity of virtual-cathode assumption relevant to numerical simulation of HET was analyzed.