S-P6-3
Fusion of Advanced Plasma Spectroscopy and Confinement Research
先進的分光計測と閉じ込め研究の融合
Masahiro Hasuo
蓮尾昌裕
Graduate School of Engineering, Kyoto University,Yoshidahonmachi, Sakyo-ku, Kyoto 606-8501, Japan
京都大学大学院工学研究科 〒606-8501 京都市左京区吉田本町
We have demonstrated for an LHD plasma that multi-line of sight and simultaneous observation ofpolarization-resolved spectra of hydrogen atomic Balmer-α, -β, -γ lines and molecular Fulcher-α
ro-vibronic bands offers information about local generation and excitation of hydrogen molecules andtransport of hydrogen from the edge region to the confined region. We have also demonstrated that atime-resolved measurement of the Balmer-α line profile offers information about temporal development ofhydrogen atom influx and those of electron temperature and density around and in the confined region
because the total intensity reflects the atom influx and the wing of the profile reflects the behavior of atom
penetration through charge exchange collisions with protons.

1. Introduction
Dynamics of the neutral hydrogen has asignificant influence on the plasma confinement ofmagnetically confined plasmas [1,2]. It isdemanded to observe behavior of atomic andmolecular hydrogen from a wall or diverter
boundary to the core region.
Spectroscopic diagnostics is one of the powerfultools. Since emission integrated along a line of sight(LOS) is usually observed in this method, local
measurements with the aid of the Zeeman pattern
appearing in the line shapes have been developed
for the Hα and Dα line emissions frommagnetically confined plasmas [3,4,5]. It is known
that polarization-resolved spectroscopy improves
accuracy in detection of the Zeeman split [6,7].
Recently, a series of work on the Hα emissions
from the periphery region of LHD plasmas with thistechnique were reported [8,9,10].
For the purpose of further improving thistechnique, we recently demonstrated a method toobserve several emission spectra of hydrogen atoms
and molecules simultaneously with developing a
multi-wavelength high-resolution spectrometer[11,12]. During these researches it has been foundthat line profiles of the Balmer-series emissions
have substantial wings, which reflect the existenceof high velocity neutral atoms and depend on theplasma parameter in the confined region [13]. Thehigh velocity neutral atoms are attributed to thosepenetrating into the high temperature region andbeing heated through charge exchange collisions
with high temperature protons there [14].
In this paper, we briefly review these work
reporting our recent progress.

2. Simultaneous measurement of polarizationresolved spectra of hydrogen atomic andmolecular emission lines
Figure 1 shows an example of the observed
spectra of the Balmer-α, -β, -γ lines, and the Q1lines of the Fulcher-α transition bands for an LHD
plasma. The temporal developments of the plasma
parameter and heating are shown in Figs. 2(a-1,2)
with the exposure time of the CCD detector. The
system for the simultaneous measurement of thesehigh-resolution spectra is explained in detail in ref.
[11,12]. The polarization dependences are clearlyobserved for all the spectra, which are due to theZeeman effect caused by the strong magnetic fieldin LHD. From the analysis of the line profiles,emission locations, intensities and velocities along
LOS can be derived as shown in Figs. 2(b-1,2). The
methods of the polarization-resolved measurement
and analysis are explained in detail in ref. [7].

Fig. 1. The observed emission spectra of the LHD
plasma. (a-1, 2, 3) show the Balmer-α, -β, -γ lines and(b-1,2) show the Q1 lines of the Fulcher-α v: 0-0 andv: 2-2 transition bands, respectively. The spectra oforthogonal polarizations are shown in the upper andlower figures. v is the vibrational quantum number.

It is seen in Figs. 2(b-1,2) that the atomic
emissions locate in the periphery region, while themolecular emissions locate outside of those. The
influence of the divertor leg on the moleculardissociation is suggested. The molecular emissions
are also found to be very large near the position
where the divertor leg hits the divertor plate. Supplyof protons, recombination to hydrogen andmolecular desorption are expected to be efficient
there. The observed results support this expectation.

Fig. 2. Temporal developments of the central electron
temperature and density (a-1), and those of the ECHand NBI heating (a-2) of the observed LHD plasma.
The exposure time of the CCD detector are shown by
the dotted squares. The emission locations, intensitiesand velocities along LOS derived from the observedhydrogen spectra at t = 3.74 - 3.92 s (b-1) and t = 4.04 4.22 s (b-2), which are indicated by the center and areaof the circles, and the length of the arrows, respectively.

3. Time-resolved measurement of Balmer-α line
profiles in a large dynamic range

Fig. 3. (a) An example of the Balmer-α emission spectra
measured by the 16-channel photo-multiplier system(bars) and the CCD system (dots). (b) Timedevelopments of the central electron temperature anddensity, and (c) those of spectral components of theBalmer-α line. A hydrogen pellet is injected at t =3.72 s.

Figure 3(a) shows an example of Balmer-α line
profiles observed for an LHD plasma. It is notedthat the intensity scale is logarithmic and thewavelength range is 6 times as large as that in Fig.
1(a-1). A large wing is seen. This wing is thought tobe due to high velocity hydrogen atoms penetrating
into the confined region through charge exchange
collisions with high temperature protons there[13,14]. On the other hand, the central part of theprofile mainly reflects the atom influx as seen inFigs. 2(b-1,2).
By developing a fast line-profile measurement
system (measurement cut-off frequency: 40 kHz)with a photo-multiplier linear array, we observe
time developments of the profile components
shown by the bars in Fig. 3 (a). The result is shownin Fig. 3 (c) with the plasma parameter change (Fig.
3(b)). The effect of a hydrogen pellet injection at
3.72 s is detected as a sudden increase in the central
intensity and decrease in the wing intensity.
Acknowledgments
The author would like to thank Mr. Fujii for his
deep contribution to this work. The author also
thanks Dr. Iwamae for the polarization-resolved
experiment from his initial stage of thedevelopment, and thanks Profs. Morita and Goto,and LHD experiment group for their support inexperiments. This work was in part by the National
Institute for Fusion Science (NIFS08KOAP020,
NIFS10KLMP003, NIFS11KLPP023)
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