Electron Diamagnetic Effect on Axial Force in an Expanding Plasma: Experiments and Theory

Abstract

The axial force imparted from a magnetically expanding current-free plasma is directly measured for three different experimental configurations and compared with a two-dimensional fluid theory. The force component solely resulting from the expanding field is directly measured and identified as an axial force produced by the azimuthal current due to an electron diamagnetic drift and the radial component of the magnetic field. The experimentally measured forces are well described by the theory.

Experimental Identification of Thrust Components Imparted by an Electrodeless Helicon Plasma Thruster

“…(3) and Eq. (5) as (9) (10) As seen in Eq. (9), the azimuthal electron current can be given by the electron ExB drift current (the first term) and the electron diamagnetic drift current (the second term), while the ion azimuthal current can be expressed by the ExB drift current.…”

“…Pb_5 calculation can be found in Ref. [10]. The calculated T total , T B , and T s are plotted in Fig.…”

“…The measurements of the thrust are performed with the pendulum thrust balance, which has already been described in the previous paper 10) . When only the solenoid coil is attached to the balance, only the force components exerted on the magnetic nozzle can be transferred to the balance; hence only the T B component can be measured.…”

“…According to the previously reported theory 9) , the spontaneously formed electric fields do not impart the momentum to the plasma; hence the thrust is still given by the maximum electron pressure integrated in cross section. Subsequently, the magnetic field configuration is modified by adjusting the solenoid current and the higher pressure in the magnetic nozzle is achieved 10) . In this configuration, the thrust increase has been clearly observed by the sole measurement of the force exerted on the expanding magnetic field.…”

Direct Measurement of Axial Momentum Imparted by an Electrothermal Radiofrequency Plasma Micro-Thruster

“…The small diameter Pocket Rocket plasma thruster called (MiniPR), is attached to a thrust balance comprising a grounded open cube frame (0.3 × 0.3 × 0.3 m 3 ) suspended from four "chimneys" (Figure 1). A laser-displacement sensor system [13,14] positioned near the top of the thrust balance mounting is used to measure the displacement of the thrust balance and hence the axial force imparted by the plasma heated gas flow. The base pressure is measured to be about 7 × 10 −7 Torr using an ion gauge and a baratron gauge located 2 m downstream of the thrust balance.…”