24P156-B
Preliminary Experiment on Dust Critical Phenomena
by Using High Density Plasma
高密度プラズマを用いた微粒子プラズマの臨界現象実験
Yasushi Maeda, Tatsuo shoji, Kozo Yamazaki
前田 靖，庄司 多津男, 山﨑 耕造
Graduate School of Engineering, Nagoya University
Furo-tyo, Chikusa-ku, Nagoya 464-0814, Japan
名古屋大学大学院工学研究科 〒464-0814 名古屋市千種区不老町

Yukawa particles in ambient neutralizing plasma are known to show a critical behavior where the inverse
isothermal compressibility vanishes predicted by Totsuji. To reveal the critical point in the dust plasma, it ispreferable to have electron density of1010−11 cm −3 [1-2] as is higher than that in conventional

experiments. We developed to create relatively high density plasma by using surface magnetic field
confinement system. We obtained electron density of more than 1010cm −3 with hollow density profile.

The dust density fluctuation measurement in the plasma is now under way.

Te ~ 3eV , ion density Ti ~ 300 K ) We developed

1. Introduction
Dustplasmas

areoneof

Yukawato obtained the electron density of less than

one-component plasmas (OCP) and are have been

1010 cm −3 with hollow density profile, which isneed to study fundamental phenomena caused byneeded to confine three-dimensional dust particles,

long range inter-particle interaction such as

by using surface energetic confinement system,

Coulomb solidification [3-4].

(SURMAC) [5]Liquid-solid phase transition in Yukawa OCP
has well studied by colloid and dust plasma
experiments, but recently critical phenomena in

2. Experimental set-up

liquid-gas plasma in dust plasmas are studied

The SURMAC plasma system is shown in Fig.1.

theoretically by Totsuji [1-2]. It is predicted toThe chamber of inner diameter R0 = 94mm andobserve the critical point where the inverse

height h = 218mm is surrounded by 12 around ofisothermal

thesamarium cobalt permanent magnets. Permanent

cm , which ismagnets column are arranged with alternative polehigher than that in conversional dust plasma

to have mirror field near the wall of the chamber.

experiments. (The example of critical parameters

Magnetic field strength profile in the horizontal

compressibility

electron density range of 10

around ne = 10

10 −11vanishes,
10 −11in−3−3

cm : degree of defiladeξ=5,cross section of the chamber is shown in Fig.1 (b).

a particle diameter rp = 1µm , electron density

The magnetic field strength at the inner chamberantenna consists of 6 rods along the axis of thechamber and are placed at r = 38mm . RF current
is fed by the power supply of 13.56MHz, 1kW toproduce inductively coupled discharge. The dust
particles are fed from the top of the chamber andthe radial density profile is measured by Langmuirprobe confined by the concave shaped electrode
where DC voltage can be applied.

Electron Density ne [cm-3]surface is 15kG and 10G of r = 20mm . RF101210111010P =1kWrf

P =350W
rf

910-40-2002040X [mm](a)Fig.2

Radialprofiles.

(b)electrondensity

f = 13.8MHz , Ar gas(1mTorr).

References[1] H. Totsuji: Plasma Res., Vol.3, 046 (2008) .
[2] H. Totsuji: Phys. Plasma, 15, 072111 (2008)[3] Y. Hayashi: J. Vac. Sci. Technol., A 18 (2000) 938.
Fig.1 (a) Schematic of RF discharge device.

[4] Lin. I: J. Vac. Sci. Technol., A 19 (2001) 2373.

(b) Arrangement of permanent magnets and[5] Y. Wong, Y. Nakamura, B. H. Quon, J. M. Dawson:

magnetic field strength contours in thehorizontal cross section Z=0.

3. Preliminary experiment on RF discharge
Plasma is produced by the RF inductive electricfields near the antenna and confined by the strong
surface magnetic field near the chamber wall.
Examples of the radial electron density profile for
Ar gas pressure of 1mTorr, RF power of 1kW and350W frequency of 13.8MHz are shown in Fig.2.
The hollow density profile obtained have us due tothe plasma loss than the top and bottom plate of thechamber where no permanent magnets are placed.
The hollow density profile is designed to havethree-dimensional dust structures.

Phys. Rev. Lett., Vol.35, 17 (1975)