Wave propagation downstream of a high power helicon in a dipolelike magnetic field

Abstract

The wave propagating downstream of a high power helicon source in a diverging magnetic field was investigated experimentally. The magnetic field of the wave has been measured both axially and radially. The three-dimensional structure of the propagating wave is observed and its wavelength and phase velocity are determined. The measurements are compared to predictions from helicon theory and that of a freely propagating whistler wave. The implications of this work on the helicon as a thruster are also discussed.

Direct thrust measurements and modelling of a radio-frequency expanding plasma thruster

“…Figure 2(a) shows that the plasma density for the long cavity (closed circles; taken at z ¼ À10 cm) is approximately linear with effective power, going from around 4 Fig. 2(b) show that for both cases the temperature is approximately constant with effective power, with a value of about 5.5 eV for the long cavity and 4 eV for the short cavity.…”

“…1,2,5 The plasma is then accelerated by ambipolar or double layer fields that form internal to the plasma. 1,2,4,6 While prolific studies of the fundamental physics in such systems have been done, detailed experimental measurements of the thrust of such devices are only now beginning to be performed. 7,8 These thrust measurements are vital, as they allow almost all other electric propulsion figures of merit to be determined, 9 and thus, the performance of such systems to be assessed.…”

“…The measured thrusts are in good agreement with the maximum upstream electron pressure found from measurements of the plasma parameters and in fair agreement with a simple global approach used to model the thruster. Expanding plasma and double layer (DL) thrusters [1][2][3][4] are receiving increasing interest due to their potential advantages over conventional systems such as ion or hall thrusters. Such advantages include the lack of an explicit neutralizer, high power and thrust densities, and the absence of biased electrodes.…”

Direct thrust measurement of a permanent magnet helicon double layer thruster

“…12 Thus a separate neutralizer system is not needed. Experimental research on plasma thrusters has to date involved studies of the fundamental physics associated with DLs, 2,3 the use of different propellant gases, 3,13 helicon wave characterization, 8 and the use of permanent magnets. 5,9 Performance estimations with regard to propulsion applications are only now starting to be considered.…”

“…In contrast to more familiar electrostatic acceleration thrusters, such as ion engines and hall thrusters, 6 plasma thrusters make use of ambipolar electric fields or DLs to accelerate ions to supersonic speeds. 1,3 These systems typically consist of an insulating source tube and a magnetic field 3,5,[7][8][9] used to provide plasma confinement and produce plasma expansion, hence forming the DL. 3,10 An rf antenna is used to produce the plasma, which is usually inductively 11 or wave coupled.…”