24P128-P
Particle Reflection from Tungsten Surface Immersed in a Hydrogen Plasma
タングステン表面での水素プラズマイオンの反射特性
Taishi Kameda1, Toshiro Kasuya1, Takahiro Kenmotu2, Yasuyuki Kimura1and Motoi Wada１
亀田大志1, 粕谷俊郎1, 剣持貴弘2, 木村恭之1, 和田 元1,1

Graduate School of Engineering, Doshisha University
1-3 Tatara Miyakodani, Kyotanabe-shi, Kyoto 610-321, Japan
2
Faculty of Life and Medical Sciences, Doshisha University
1-3 Tatara Miyakodani, Kyotanabe-shi, Kyoto 610-321, Japan1
同志社大学大学院工学研究科 〒610-321 京田辺市多々羅都谷1-32
同志社大学大学院生命医科学研究科 〒610-321 京田辺市多々羅都谷1-3
The angular and energy distributions of hydrogen atoms released from tungsten surface due to hydrogenion reflections are calculated by ACAT code, to evaluate the spectrum broadening of H . The result has
shown a characteristic shape of line broadening distinctively different from the Gaussian velocity
distribution. An experimental system is being arranged to observe the Doppler shifts of H line spectrum
corresponding to the ACAT calculation conditions.

1. Introduction
Reflection of hydrogen atoms at tungsten surface
should exhibit a peculiar characteristic showing acomponent of atoms reflected into the solid angle
nearly parallel to the tungsten surface with little
energy loss by collision. This component ofreflected hydrogen can be measured by observing aDoppler shift of hydrogen line spectrum emission
like H (656.28 nm).
The line spectrum
broadening of H due to impact of 200 eV proton
has been calculated with ACAT (Atomic Collisionin Amorphous Target) code and the result is shownin Fig. 1. The experimental arrangement to obtain
spectroscopic data that can be compared with Fig. 1
is being assembled.
200 eV H+ →W at 0°Intensity [a.u.]

0.20

0.15

0.10

mounted with heating element to control the surface
temperature.
Dimensions of the dischargechamber are 220 mm in diameter, and 920 mm inlength. Plasma can be excited either by tungsten
filament cathode, or a microwave applicator.
The area in front of the W target is observedwith the light axis set parallel to the target surface.
The light along the observation axis is reflected by
90 degree with a copper mirror inside of thedischarge chamber, and guided to a vacuum
window mounted at the end of the dischargechamber. A condenser lens is mounted in theanodized aluminum cylinder to exclude stray lights,
and the lens focuses the image of the sheath in frontof the target at the slit of a monochromator of 0.1
angstrom resolution.
The direct light from the hydrogen plasma isbright and the measurement of the Doppler
broadening has to be done with poor S/N ratio. To
improve the S/N ratio, H spectrum will berecorded phase sensitively by modulating the target
bias voltage.

0.05

0.00
-0.4

Power supply

-0.2

0.0

0.2

0.4

Photomultiplier
tubeRef.

Wave length [nm]Fig. 1. Doppler shift of H from hydrogen atoms
produced by reflection of 200 eV protons at tungsten
surface.

Function generator

Logger
Amplifier

LensGrating

Spectrometer

2. Experimental apparatus
A schematic illustration of the experimental
setup is shown in Fig. 1. At the end of the plasma
column sustained by 800 G magnetic field, atungsten target of 50 mm in diameter has been

Lock-in amplifier

CoppermirrorTargetPlasmaChamber
Filament

Fig. 2. Illustration of the experimental setup to measure
the H Doppler shift of H atoms from W surface.