23P032-P
Pitch Angle Dependence of Fast Electrons Energy Spectra
Measured with a Soft X-Ray Pulse Height Analyzer in Heliotron J
ヘリオトロンJにおける軟X線波高分析による
高速電子エネルギー分布のピッチ角依存性計測
Yoshinobu Wada1, Hiroyuki Okada2, Kazunobu Nagasaki2, Satoshi Yamamoto2, Tohru Mizuuchi2,Takashi Minami2, Shinji Kobayashi2, Shinsuke Ohshima3, Kiyofumi Mukai1, Hyunyong Lee1,
Linge Zang 1, Watada Hiroto1, Arai Shohei1, Kagawa Tasuku1, Kousji Mizuno1, Takayuki Minami1,Hiroaki Yashiro1, Yuji Nakamura1, Kiyoshi Hanatani2, Shigeru Konoshima2 and Fumimichi Sano2
和田善信 1, 岡田浩之 2, 長崎百伸 2，山本 聡 2, 水内 亨 2, 南 貴司 2, 小林進二 2,大島慎介 3, 向井清史 1, H.Y. Lee1, L. Zang1, 和多田泰士 1, 荒井翔平 1, 香川 輔 1,水野浩志 1, 南 貴之 1, 八代浩彰 1, 中村祐司 1, 花谷 清 2, 木島 滋 2, 佐野史道 2
1

Graduate School of Energy Science, Kyoto University, Gokasho, Uji, 611-0011, Japan京都大学エネルギー科学研究科 〒611-0011 京都府宇治市五ヶ庄
2Institute of Advanced Energy, Kyoto University, Gokasho, Uji, 611-0011, Japan京都大学エネルギー理工学研究所 〒611-0011 京都府宇治市五ヶ庄
3Pioneering Research Unit for Next Generation, Kyoto University, Gokasho, Uji, 611-0011, Japan
京都大学次世代開拓ユニット 〒611-0011 京都府宇治市五ヶ庄
A soft x-ray Pulse Height Analyzer (PHA) is installed in Heliotron J for the measurement of fast-electronenergy spectrum at various pitch angles. The detector can be tilted in the range from -10° to 10°
horizontally and from -3° to 7° vertically. The main purpose of the study is to confirm experimentally thechange of fast-electron spectra expected in the electron cyclotron current drive (ECCD) phase. In this paper,
we report the change in fast-electron energy spectrum of ECH only phase in pitch angle scan.

1. Introduction
Measurement of energy spectra in soft X-ray
region can give us useful information about line
impurities species, bulk electron temperature andelectron loss region in the velocity space. In
addition, the effect of fast electrons on the toroidal
current can be evaluated from the signals in theparallel and anti-parallel directions.
A new movable PHA system has been installedin Heliotron J [1, 2] in order to measure the pitch
angle dependence of the electron energy spectrum.
In this paper, we report a preliminary result of pitch
angle scan experiment performed to examine thechange in energy spectrum, especially in ECCDexperiment.
2. PHA System in Heliotron J
Figure 1 illustrates the arrangement of the PHA
system in Heliotron J. This system can tilt its sightline horizontally from -10° to 10°. This range isequivalent to the pitch angle,  from 98° to 126° inthe standard configuration of Heliotron J. The
observing area can be controlled by using

perpendicular and horizontal slits. The sensitivity
range of a silicon detector in the PHA system isfrom 0.5 to 30 keV. The energy resolution is 0.10 0.25 keV.
The maximum rate of the shaping amplifier isabout 80×103 counts/s. This system has four Befilters of which thickness are 30 m, 70 m, 150
m and 300 m to control minimum detectableenergy. The values of photon energy for thetransparency greater than 80% are 2.5 keV for the30 m filter, 3.2 keV for 70 m filter, 4 keV for 150
m filter and 5keV for 300 m filter.
Figure 2 shows arrangement of PHA system inthe poloidal cross-section. The angle of the sightline can be changed perpendicularly from -3° to 7°.
These values correspond to the range in normalizedradius from 0 to 0.35. By using this tilting system
the observed pitch angle can be changed toroidallywith keeping the condition that the sight line
crosses the magnetic axis.
3. Experiments and Discussions
Figure 3 shows the line averaged electron

1.5

n e (10 19 m-3)
Ip (kA)#44006

Measurement
time

10.5
ICRF

0200

Fig.1 Arrangement of the PHA system

ECH

300time (ms)Fig.3 Measurement plasma parameter andinjection parameter
0.6
A (#43801~#43842)
B (#43857~#43894)
C (#43986~#44028)

I (A.U.)

0.5

Fig.2 Projection of the sight line of PHA systemon the poloidal cross-section
density, ne , and the non-inductive plasma toroidal
current, Ip. A plasma is generated and sustained by
70-GHz ECH (N// = 0.35) in the high bumpy
configuration [3]. The average magnetic fieldstrength is 1.36 T. The ECH pulse is injected from
165 ms to 285 ms, and its injection power is about
250 kW. In addition, ICRF [4] is injected from 220ms to 240 ms in this particular set of discharges.
The electron density is about 0.5×1019 m-3. The total
plasma current flows in the counter-clockwise
direction in Fig.1. The current gradually increases
up to 0.8 kA in the first half period of the discharge
and is almost constant in the second half of thedischarge. The energy spectra are observed for threedifferent pitch angles keeping on-axis condition.
The selected sight lines are indicated as A, B and Cin Fig.1. The pitch angles are 119° for A, 110° for
B, and 101° for C.
Figure 4 shows the observed energy spectra forthe three cases. The measurement time interval of
the PHA is from 240 ms to 290 ms. It is observedthat the photon counts in the energy range 7-10 keV
is decreased as changing the pitch angle from 101° to 119°, while there is no clear difference at
low-energy (< 6.5 keV) photon counts andhigh-energy (> 9 keV) photon counts. The result of

0.4
0.3
0.2
0.1
078910Energy (keV)

Fig.4 Measurement of energy spectra of soft
X-ray by PHA system
the observation is consistent with the toroidal
current direction if the fast electrons in the range of
7-10 keV carry the plasma current. For the next step,
we will try to make observation of PHA signals forthe plasmas where the toroidal plasma current by
ECCD flows much larger, for example, in low
bumpy configurations [3].
Acknowledgement
This work is performed with the support andunder the auspices of Collaboration Program of theLaboratory for Complex Energy Processes, Instituteof Advanced Energy, Kyoto University, NationalInstitute for Fusion Science (NIFS) Collaborative
ResearchProgram(NIFS10KUHL030,
NIFS11KUHL038)
References[1] F.Sano et al., J. Plasma Fusion Res. SERIES 3,26 (2000).
[2] T.Obiki et al., Nucl.Fusion 41, 833 (2001)[3] K.Nagasaki et al., J. Plasma and Fusion Res.
Vol. 3, S1008 (2008).
[4] H.Okada et al., Nucl. Fusion 47, 1346 (2007)