25T1
New Plasma Regime and Physics Research in JT-60SA
towards ITER and DEMO
JT-60SAにおける新しいプラズマ領域とITERおよび原型炉に向けた物理研究
Takaaki Fujita1, the JT-60SA Team藤田隆明1, JT-60SAチーム
1

Japan Atomic Energy Agency
801-1, Mukoyama, Naka-shi, Ibaraki-ken 311-0193, Japan
日本原子力研究開発機構 〒311-0193 茨城県那珂市向山801-1
The JT-60SA device is a highly shaped large superconducting tokamak with a variety of plasma actuators.
The JT-60SA will explore new plasma regimes and resolve key physics issues associated with ITER andDEMO in the areas including particle/heat transport, MHD stability, non-inductive current drive, highenergy particle physics, ELMs and particle/heat control with divertor. By integrating these studies,
steady-state sustainment of integrated performance required for DEMO will studied in JT-60SA, aiming at
establishment of control scenarios with minimum actuators.

1. Introduction
The JT-60SA Project [1] is a combined projectof the Broader Approach (BA) Satellite Tokamak
Program, jointly implemented by Europe andJapan, and the Japanese national program. The
mission of JT-60SA is to contribute to early
realization of fusion energy by supporting theexploitation of ITER and research towards
DEMO [2]. This paper reports the new plasma
regimes and physics research to be addressed in
JT-60SA towards ITER and DEMO.
2. Device Features and Status of Construction
The JT-60SA device has superconducting
toroidal and poloidal field (TF and PF) coils. The
maximum plasma current (Ip) is 5.5 MA and thetoroidal field (Bt) is 2.25 T. A highly shaped
configuration (major radius R = 2.96 m, minor
radius a = 1.18 m, aspect ratio A = 2.5, elongation
κx = 1.95, triangularity δx = 0.53) is possible. The
poloidal cross-section of the device in shown in Fig.
1. The superconducting coils consist of 18 TF coils,
4 central solenoid (CS) modules and 6 equilibrium
field (EF) coils. In the vacuum vessel, 3 sets ofcopper coils will be installed; fast plasma position
control coils (upper and lower axisymmetric coils),
error field correction coils (3 poloidal × 6 toroidal)
and Resistive Wall Mode (RWM) control coils (3poloidal × 6 toroidal). Furthermore, a stabilizing
plate (shell) is equipped for suppressing the verticalstability and RWM. All of the plasma facingcomponents are water-cooled. The divertor hasvertical CFC monoblock targets that will handle
high heat flux up to 15 MW/m2. Cryopanels will be

installed beneath the divertor cassette for pumping.
A remote handling system will be prepared formaintenance of in-vessel components including thedivertor cassette without manned entry after highpower deuterium operation. Metallic targets will be
installed in the later phase.

Fig.1. Cross-section of the JT-60SA tokamak.

The heating system provides 34 MW of NB
injection, including 24 MW of positive ion NB(P-NB) and 10 MW of 500 keV negative ion NB(N-NB), and 7 MW of ECRF for up to 100 s. The
N-NB will be tangentially injected into a half radiusregion of the plasma. This is one of the uniquefeatures of JT-60SA, which will enable weak orreversed magnetic shear configuration for advanced
tokamak operation.
Construction of JT-60SA is in progress towardthe first plasma foreseen in 2016. Fabrication of PF
coils, the vacuum vessel and the cryostat base wasstarted, and the first 40 degree sector of the vacuum
vessel was completed. Disassembly of the JT-60U
device is underway and will be completed by 2012.
3. New Plasma Regimes and Physics ResearchNon-dimensional plasma parameters (beta,normalized poloidal gyroradius, normalizedcollisionality) will be closer to the values in ITER
and DEMO than all existing devices, as shown inFig. 2, under reactor-relevant heating conditions(dominant electron heating and low central fuelingand low external torque input), which will enable
heat and particle transport study, in the core andalso at the pedestal, for ITER and DEMO. Plasma
characteristics including beta limit and confinement
properties will be studied in a regime with A~2.5
which is relevant to the economic DEMO design.
A long pulse, high current, high beta reversed
shear plasma with full non-inductive current driveis expected using off-axis NBCD. Figure 3 shows
profiles of density, temperature, current density andsafety factor q in a reference scenario where Ip = 2.3
MA, the normalized beta βN = 4.3, the confinement
enhancement factor H98y2 = 1.3, and the bootstrap
current fraction fBS = 0.68 with the injected powerof 37 MW (N-NB: 10 MW, P-NB: 20 MW and
ECRF: 7 MW). The MARG2D analysis confirmsthat this plasma is stable for the n≤4 kinkballooning mode with ideal wall. The pedestal isstable for the n<40 peeling-ballooning mode.
Sustainment of high beta above the no-wall beta
limit will be extended up to 100 s, as shown in Fig.
4, by using the stabilizing shell, the RWM control
coils and the error field correction coils as well asby plasma toroidal rotation scan with co- andcounter injected NBs. Interactions between highenergy ions and MHD instabilities will also bestudied with N-NB injection that will realize
reactor-relevant high energy particle conditions
with βfast = 0.2–1% and Vfast-ion/Valfven = 1.5–2. The
high power long pulse N-NB will also enablenon-inductive current ramp experiment, which isindispensable for a slim CS DEMO.
The ELM study including the type-I ELM
energy loss and ELM mitigation using resonant
magnetic perturbation (RMP) and pellet pacing will
be studied at the ITER-relevant collisionality at thepedestal in the ITER-like plasma shape. For DEMO,
JT-60SA expands the Grassy ELM regime in thehigh triangularity shape. At divertor, the particle
control will be achieved by changing the pumping
speed of cryopanels. Impurity seeding will beemployed to achieve high radiation power for aplasma with full non-inductive current drive andwith relatively low edge density.
By integrating the above studies, steady-statesustainment of integrated performance required for
DEMO will studied in JT-60SA, aiming at
establishment of control scenarios with minimum
actuators. A plasma simulator code with integrated
models for core and SOL/divertor plasmas is underdevelopment, in order to predict plasma
characteristics and develop control scenarios inJT-60SA and ITER.

Fig.2. Normalized poloidal gyroradius and normalized
collisionality.

Fig.3. A high beta plasma with full non-inductive
current drive.

Fig.4. High β N target regime of JT-60SA.
References[1] S. Ishida et al.: Nucl. Fusion 51 (2011) 094018.
[2] Y. Kamada et al.: Nucl. Fusion 51 (2011) 073011.