11:00 AM - 1:00 PM
[PEM16-P07] Mechanism of the helicon plasma production from low-density to high-density regimes
The development of high-power electric thrusters has become active across the world for the purpose of reducing the flight time of long-term future missions such as the manned exploration of Mars. The high-density helicon plasma source is expected to be useful for such high-thrust propulsion systems, and helicon thrusters based on magnetic nozzle type propulsion are being developed [1,2].
In the helicon plasma production, neutral dynamics plays an important role in determining the plasma transport and the maximum plasma density [3]. In laboratory experiments, it is shown that the plasma density saturates as the input power is increased [4], and the density profile starts to oscillate [5] due to the depletion of the neutral gas. Physical understanding of these processes is important to overcome the density limit and to realize stable plasma sources. For the stable production of high-density plasma, it is also important to understand the transition process from the low-density (~1017-18 m-3) to high-density (~1019-20 m-3) regime, which are observed in experiments [6].
We have numerically investigated the self-consistent behavior of the helicon discharge including the neutral dynamics [7]. In the low-density regime (~1017-18 m-3), it is found that the plasma production is sustained by the electrostatic wave and the cpasisitively coupled component of the radio-frequency antenna. In the high-density regime, the plasma density temporarily grows to ~1019-20 m-3 with increasing the input power, but the neutrals are seriously depleted to a level below the plasma density (~1018 m-3). In this situation, the pressure balance between the plasma and the neutrals is violated and the density profile starts to oscillate. The time scale of the oscillation is characterized by the sound speed defined by the neutrals. In this presentation, we discuss the mechanism of the helicon plasma production from the low-density to high-density regimes.
[1] Press release from Ad Astra Rocket Company (http://www.spaceref.com/news/viewpr.html?pid=57827)
[2] K. Takahashi, T. Sugawara and A. Ando, Sci. Rep. 10 1061 (2020).
[3] A. Fruchtman, J. Phys. D: Appl. Phys. 50, 473002 (2017).
[4] R. M. Magee et al., Phys. Plasmas, 20 123511 (2013).
[5] A. W. Degeling et al., Phys. Plasmas, 6 3664 (1999).
[6] M. Nisoa, Y. Sakawa and T. Shoji, Jpn. J. Appl. Phys. 40 3396 (2001).
[7] S. Isayama, S. Shinohara, T. Hada and S. H. Chen, Phys. Plasmas, 26 053504 (2019).
In the helicon plasma production, neutral dynamics plays an important role in determining the plasma transport and the maximum plasma density [3]. In laboratory experiments, it is shown that the plasma density saturates as the input power is increased [4], and the density profile starts to oscillate [5] due to the depletion of the neutral gas. Physical understanding of these processes is important to overcome the density limit and to realize stable plasma sources. For the stable production of high-density plasma, it is also important to understand the transition process from the low-density (~1017-18 m-3) to high-density (~1019-20 m-3) regime, which are observed in experiments [6].
We have numerically investigated the self-consistent behavior of the helicon discharge including the neutral dynamics [7]. In the low-density regime (~1017-18 m-3), it is found that the plasma production is sustained by the electrostatic wave and the cpasisitively coupled component of the radio-frequency antenna. In the high-density regime, the plasma density temporarily grows to ~1019-20 m-3 with increasing the input power, but the neutrals are seriously depleted to a level below the plasma density (~1018 m-3). In this situation, the pressure balance between the plasma and the neutrals is violated and the density profile starts to oscillate. The time scale of the oscillation is characterized by the sound speed defined by the neutrals. In this presentation, we discuss the mechanism of the helicon plasma production from the low-density to high-density regimes.
[1] Press release from Ad Astra Rocket Company (http://www.spaceref.com/news/viewpr.html?pid=57827)
[2] K. Takahashi, T. Sugawara and A. Ando, Sci. Rep. 10 1061 (2020).
[3] A. Fruchtman, J. Phys. D: Appl. Phys. 50, 473002 (2017).
[4] R. M. Magee et al., Phys. Plasmas, 20 123511 (2013).
[5] A. W. Degeling et al., Phys. Plasmas, 6 3664 (1999).
[6] M. Nisoa, Y. Sakawa and T. Shoji, Jpn. J. Appl. Phys. 40 3396 (2001).
[7] S. Isayama, S. Shinohara, T. Hada and S. H. Chen, Phys. Plasmas, 26 053504 (2019).