23P079-P
Analysis of Current Quench of the JT-60U tokamak by using two dimensional
MHD equilibrium calculation Code (DINA).
2 次元軸対称MHD平衡計算コードDINAを用いたJT-60Uにおける電流クエンチ解析
Syo Kawakami, Shibata Yoshihide, Watanabe Kiyomasa, Ohno Noriyasu,
Kajita Shin,Okamoto Masaaki, Isayama Akihiko, Sugihara Masayoshi,
Kawano Yasunori, V.E. Lukash, R.R. Khyarutdinov
河上翔，柴田欣秀，渡邊清政 1，大野哲靖，梶田信 2，岡本征晃 3，
諌山明彦 4，杉原正芳 4，河野康則 4，V.E. Lukash5, R.R. Khayrutdinov5
Graduate School of Engineering, Nagoya University,Furou-cho, Chikusa-ku, Nagoya, Aichi 464-8603, Japan
名古屋大学工学研究科, 〒464-8603 名古屋市千種区不老町
1
National Institute for Fision Science, Oroshi-cho, Toki, Gihu 509-5292, Japan
自然科学研究機構 核融合科学研究所, 〒509-5292 岐阜県土岐市下石朝 322-6
2Eco Topia Science Institute, Nagoya University, Furou-cho, Chikusa-ku, Nagoya, Aichi 464-8603, Japan
名古屋大学エコトピア研究機構, 〒464-8603 名古屋市千種区不老町3Ishikawa National College Technology, Kitachoujo, Tsubata-cho, Kahoku-gun, Ishikawa 929-0392, Japan
石川工業高等専門学校, 〒929-0392 石川県河北郡津幡町北中条夕 1
4Japan Atomic Energy Agency, Muramatsu, Tokai-mura, Naka-gun, Ibaraki 319-1184, Japan
日本原子力研究開発機構, 〒319-1184 茨城県那珂郡東海村村松 4-49
5Kurchatov Institute, Academician Kurchatov Sq 1, Moscow, Russia 123 098
During the disruption of tokamak, the plasma current rapidly decays to zero and it gives the large mechanical force inthe structure. In this study, we predicted the time evolution of plasma current during the disruption by using thedisruption simulation code, which is called DINA, and investigated the effects of electron temperature, Te and aneffective charge, Zeff on the predicted time evolution of plasma current, Ip in JT-60U radiative disruption. In thecalculation, it was found that time evolution of Ip is good agreement with the experimental behavior of Ip when weassumed Te=30eV and Zeff=3. However, internal inductance, which indicates the shape of current density distribution,evaluated by DINA code differs from the experimental values. Hence, we need to match the experimental andcalculated results in order to predict correctly the plasma behavior during the disruption.

1. Introduction
The plasma current and cross-section plasma
rapidly decay to zero during tokamak disruption.
They generate a halo current and an eddy current,
and such currents give a large mechanical force into
the structure around the plasma. It is a significant
problem for stable operation of fusion tokamak
device such as ITER.
In this study, we simulate the behavior of theplasma current during the radiative disruptive
discharge in JT-60U by using a disruptive
simulation code, DINA in order to clarify thedetermination mechanism of plasma current decay
during the current quench [1].
2. Modification of DINADINA is two dimensional MHD equilibrium
calculation code for disruption simulation. The rateof plasma current quench in DINA, taking the time
evolution of the poloidal flux into account, isdetermined with specified values of electron
temperature, Te, and an effective charge, Zeff [2,3].

Te and Zeff are calculated by a Power Balance
equation. However, the upper limit of Te calculation
result sets to 10eV because Te has the single uniquesolution. To investigate the effect of those plasma
parameters on the time evolution of plasma current
during disruption, we analyze in the radiative
disruptive disruption of JT-60U. Table I shows theassumption values of Te and Zeff in this calculation[4]. In case A, the Te and the Zeff were calculated by
DINA code. In case B, we assumed Te equals 20eVand Zeff calculated from Power Balance equation. In
case C, we assumed Zeff equals 3.
Table I. The assumption values of Te and Zeff in thiscalculation
Te (eV)
Zeff

Case A
Case B
Case C
Case D–20(constant)20(constant)30(constant)––
33

3. Result
Waveforms of time evolutions of plasma current Ip,Te, and plasma cross-section, S, are shown in Fig.1.
In case A, DINA does not reproduce behavior of theplasma current, because Te decays rapidly comparedwith the experimental data. In case D, time
evolutions of the Ip and S were good agreementwith the experimental data.
Fig.2 shows profiles of normalized current density
distributions at Ip =Ip0 (t1) and Ip=0.9 × Ip0 (t2). HereIp0 is the value of plasma current just after current
quench starts. ρ is a normalized plasma small radius.
The current density profile is calculated by theEq(1)𝑗⁄𝑗0 = (1 − 𝜌2 )𝜈 ,(1)
ν = (𝑒 𝑙𝑖 − 1.65)⁄0.89,(2)where ν is the peaking factor and li is the internal
inductance [3]. In experimental data, we calculated
ν using the Eq(2). When Ip =Ip0, in case D, thisprofile does not match the experimentalmeasurement. Furthermore, time change ofexperimental current density profile is peaking at
center relative to time change of DINA.
In addition to, in case C, Ip decays more rapidlyrelative to case B and in case B, averaged Zeff is
1.29. Therefore, the rate of plasma current quench
depends on Zeff.

Fig.1.Time evolutions of plasma current Ip ,electron
temperature Te ,and plasma cross-section S

Fig.2. Profiles of normalized current density distribution

4. Summary
We analyzed the current quench in the radiative
disruption of JT-60U by using DINA. When we
assumed Te=30eV and Zeff=3 in DINA, we showed
the behavior of the plasma current is good
agreement and Zeff affects to Ip. However, DINA
profile of normalized current density distribution at
Ip=Ip0 does not match the experimental
measurement, because flat Te profile was assumed
in the present DINA calculation.
For future work, we will introduce the measured
Te profile to the DINA code to reproduce the profileof the normalized current density distribution moreaccurately.
References[1] R.R.Khayrutdinov and V.E.Lukash, J. Comput.
Physics, 109(1993) 193-201.
[2] H. Ohwaki, et al., Plasma and Fusion Research
Regular Articles,1(2006) 016.
[3] J.A.Wesson, Tokamaks 3rd edition, Oxford
University Press, (2004) Ch 3,6,7.
[4] Y.Shibata, et al., Nucl Fusion, 50(2010)025015.