Plume Characteristics of a Quasi-steady Magnetplasmadynamic Arcjet

摘要

The plasma plume of a 1-MW-class quasi-steady magnetoplasmadynamic (MPD) arcjet is studied to reveal the plume structure and the plasma plume fluctuations in a downstream plume region (250-1250 mm away from the MPD arcjet). By using a double probe, a high electron temperature (～5 eV) and a high number density (～8×l0~(19)m~(-3)) region so-called "cathode jet" are found along the central axis of plasma plume near the MPD arcjet and the plasma plume radial profile is flat in a downstream plume region (750 mm or more from the MPD arcjet). The power spectrum density (PSD) of the ion saturation current is proportional to 1/f~(1.6): frequency) for f> 80 kHz range, and at this range PSD decreased with the distance from the MPD arcjet. In the lower frequency region of 80 kHz in contrast, where PSD vs./curve is flat. Although the peak considered to be the GLHDI (Generalized Lower Hybrid Drift Instability) instability existed in PSD of the discharge voltage, it is not measured in the plasma plume near the MPD arcjet. The influence of the GLHDI is limited only in the discharge chamber, and the fluctuation is random in the downstream region.