26aD21P
永久磁石を用いた高周波プラズマの特性評価
Characteristics of Radio Frequency Plasma Using Permanent Magnets
岸謙介，山瀬智也，桑原大介，篠原俊二郎
K. Kishi, T. Yamase, D. Kuwahara, S. Shinohara
農工大工TUAT
between magnetic fields, RF frequencies, and argon
gas pressures by measuring an electron density neand ion velocity vi in the radial and axial directions
by the use of an L-shaped Mach probe. In addition,
to verify and improve the effect of permanent
magnet system on the plasma, we will attempt touse another gas species, and have a combined
operationwithpermanentmagnets
andelectromagnets.
Magnets holder

Vacuum chamber(i.d. = 165 mm)

Argon gas

Quartz tube

Mach probe

Antenna(i.d. = 20 mm)

To pump-170 -50 0-400865

z [mm]

Fig. 1 Schematic of SHD.
(i)

Unit : mm(ii)

Permanentmagnets

1210For a deep space exploration, electric
propulsion systems are more efficient thanchemical ones, because of their higher specificimpulse, which is suitable for long-term space
missions with less propellant. In the conventional
electric propulsion systems, e.g., ion thrusters,
their lifetime are often limited due to electrodeerosion by a collision with plasmas. In order tomake the longer lifetime and the higher efficiency,
we have been developing new electrodelessplasma propulsion systems with a high-density(~1013 cm-3) helicon plasma source, as a Helicon
Electrodeless Advanced Thruster (HEAT) project[1]. This acceleration principle uses the Lorentz
force Fz, the product of the induced azimuthal
current j in the plasma and the external static
radial magnetic field Br.
In recent years, a number of researches of ahelicon plasma thruster using a magnetic nozzle
have been developed [2,3]. This takes advantage
of efficient helicon plasma production, obtaining
high-density plasma (~ 10 13 cm-3) with a wide
range of external conditions. A magnetic nozzle
with the strong magnetic field is important to be
applied to the electrodeless plasma propulsion
system because of two following benefits: anincrease of an electron density [4] and a reductionof a radial plasma loss [5]. Therefore, we havedeveloped an external magnetic field source using
permanent magnets, which can generate strong
magnetic field more easily without power
supplies compared to the electromagnets
This study deals with characteristics ofradio-frequency (RF) plasma performance using amagnetic nozzle system in a small-diameter heliconsource named Small Helicon Device (SHD), as
shown in Fig. 1 [6]. The magnetic field was up to0.3 T by the developed permanent magnet system(Fig. 2). Here, the plasma was generated at an RF
frequency of 12 ~ 150 MHz with an RF power up to1 kW.
In the presentation, we will show effects of thedeveloped magnet system on the plasma
performance: we have examined a relationship

Quartz tuber2033 46

Antenna Quartz tube

Permanentmagnets

Fig. 2 Layout of permanent magnets.
(i) Shematic of magnets holder. (ii) Arrangement ofthe magnets from the front side.
[1] S. Shinohara et al., IEEE Trans. Plasma Sci. 42(2014) 1245.
[2] K. Takahashi et al., J. Phys. D: Appl. Phys. 46(2013) 352001.
[3] T. Nakamura et al., Trans. JSASS Aerospace Tech.
Japan 12 (2014) ists29 p. Po_1_1-Po_1_6.
[4] S. Shinohara et al., Rev. Sci. Instrum. 77 (2006)
036108.
[5] K. Takahashi et al., Phys. Rev. Lett., 110 (2013)
195003.
[6] D. Kuwahara et al., Rev. Sci. Instrum. 84 (2013)
103502.