Overview of the KSTAR Research Progress and Future Plan toward
ITER and K-DEMO

Hyeon K. Park
UNIST, Ulsan, Korea
On behalf ofthe co-authors and KSTAR Teamat 27th IAEA FEC,
Gandhinagar, India, 2018

M.J. CHOIb, S.H. HONGb Y. Ina, Y.M. JEONb,
J.S. Kob, W.H. Kob, J.G. KWAKb J.M. KWONb, J.
Leeb, J.H. LEEb, W. LEEb, Y.B. NAMd, Y.K. Ohe,
B.H. PARKb, J.K. PARKf, Y.S. PARKg, S.J.
WANGb, M. YOO c, S.W. YOONb, J.W. AHNh,
J.G. BAKb, C.S. CHANGf, W.H. CHOEi, Y. CHUb,
J. CHUNGb, N. EIDIETISj, H.S. HANb, S.H.
HAHNb, H.G. JHANGb, J.W. JUHNb, J.H. KIMb,
K. KIMh, A. LOARTEe, H.H. LEEb, K.C. LEEb, D.
MUELLERf, Y.S. Nac, Y.U. NAMb, G.Y. PARKb,
K.R. PARKb, R.A. PITTS e, S.A. SABBAGHg,
G.S. YUNk
IAEA FEC PARKa Ulsan National Institute of Science and Technology, Ulsan,

Korea
b National Fusion Research Institute, Daejeon, Korea
c Seoul National University, Seoul, Korea
d CEA, St. Paul Lez Durance, Francee ITER Organization, Route de Vinon-sur Verdon. 13067 St.
Paul Lez Durance, France
f Princeton Plasma Physics Laboratory, Princeton, NJ, USA
g Columbia University, NY, USA
h Oak Ridge National Laboratory, TN, USAi Korea Advanced Institute of Science and Technology,
Daejeon, Korea
j General Atomics, CA, USA
k Pohang University of Science and Technology, Pohang,
Korea

-1-

Topics to be addressed Mission and role of the KSTAR research for ITER and KDEMO
 Advantages of tokamak plasma research on KSTAR
 Progress of the KSTAR research programHigh performance and steady-state operation
Physics of MHD/Turbulence
Progress and understanding of the ELM-crash control with RMP
Research efforts for ITER and K-DEMO Future upgrade plan Summary
IAEA FEC PARK

-2-

Mission and role of KSTAR for ITER and K-DEMO
 KSTAR Mission is:• to explore science and technology for high performancesteady-state operation, that are essential for fusion reactors

K-DEMO Role of KSTAR for ITER & K-DEMO• Expansion of operating regimes, validation of tokamak
physics and advanced control for SC device like ITER
using the KSTAR unique tools• Stationary High beta (𝝱N ~4) with highbootstrap• Optional new mode of operation including
auto start-up with high duty cycle• CD and divertor heat flux control

 to expand the KSTAR operation boundaries of the conventional modes ofoperation and new mode of operation for minimum harmful instabilities(avoid NTM and ELM-crash) to explore physics and preemptive control of the harmful instabilities inhigh beta operation (ELM-crash, NTM, disruptions, etc.)

ITER to assist optimum operation of ITER: H-mode threshold power control,
rotation control via NTV, heat dispersion with RMP, etc.

• Exploration of the limit of high beta steady state operation
and R&D of key engineering and technology for K-DEMO
 Exploration of higher beta operation with the KSTAR upgrade

KSTAR

 Alternative current drive for steady-state operation
 New start-up for high duty cycle with long pulse
IAEA FEC PARK

• Steady-state H-mode (𝝱N ~2)• Rotation by NTV, and new start-up,
H-mode access• Suppression of ELM-crash,disruption-3-

View of KSTAR with new NBI-2 system

ECH & Helicon & LHCD
KSTAR

NBI-1

Advanced Microwave
Imaging Diagnostics
Carbon wall

NBI-2 (New)

IAEA FEC PARK

-4-

Collaborating domestic and international Institutes andUniversities on the KSTAR program
Domestic Collaborating
Universities and Institutes

Domestic Collaborating
Universities and Institutes

IAEA FEC PARK

-5-

Device parameters of KSTAR, ITER and K-DEMO
KSTAR(achieved)

KSTAR(Goals)ITER(Baseline/SS)

K-DEMO(Option II)

Major radius, R0 [m]Minor radius, a [m]Elongation, Triangularity, Plasma shape

1.8
0.5
2.16*
0.8
DN, SN

1.8
0.5
2.0
0.8
DN, SN

6.2
2.0
1.7
0.33
SN

6.8
2.1
1.8
0.63
DN (SN)

Plasma current, IP [MA]
Toroidal field, B0 [T]H-mode duration [sec]N
Bootstrap current, fbs

1.0
3.5
73
3.0 (4.3, transient)
~0.5

2.0
3.5
300
5.0

15/ ~105.3
400 / 1000
~3.0

> 12
7.4
SS
~ 4.2
~ 0.6

Superconductor
Heating /CD [MW]PFC / Divertor
Fusion power, Pth [GW]

Nb3Sn, NbTi
~10
C, W

Nb3Sn, NbTi
~ 28
C, W

Nb3Sn, NbTi
~ 73
W
~0.5

Nb3Sn, NbTi
120
W
~ 3.0

Parameters* exceeded
IAEA FEC PARK

-6-

Topics to be addressed Mission and role of KSTAR research Advantages of tokamak plasma research on KSTAR
 Progress of the KSTAR research programHigh performance and steady-state operation
Physics of MHD/Turbulence
Progress and understanding of the ELM-crash control with RMP
Research efforts for ITER and K-DEMO Future upgrade plan Summary
IAEA FEC PARK

-7-

Uniqueness-1: nearly perfect symmetry of thetokamak plasmas
 Extremely low magnetic ripple for minimum ripple loss. (B/B~0.05 %) Extremely low error field configuration (𝛿B/B0~1x10-5)
 Manufacturing and assembly of the magnets with high accuracy
 Robust structures to sustain the TF coil shape uniform Designed with strong shaping capability for high beta operation stability
 Double & single null capable and passive stabilizer for stabilizing VDE & RWM

 Control flexibility using four pairs of CS coils and high elongation ( ~ 2.16) &triangularity ( ~ 0.8)

SC magnets manufactured without internal joints to minimize error field
IAEA FEC PARK

-8-

Uniqueness-2: Versatile in-vessel control coils for
perturbation study and advanced imaging diagnostics
 Unique in-vessel control coils with 3 poloidal rows
(top, middle and bottom; e.g., ITER) Flexible 3D field perturbation with n=1, 2 and mixed
 Broad band power supply (~10 kHz) and patch panel
for fast control for position, ELM-crash, rotation
control & RWM control

KSTAR In-vessel
Control Coils
Top / Middle / Bottom

 Advanced 2D/3D imaging diagnostics
 ECEI, MIR, BES, imaging bolometer,
FILD, SXR, etc.

ECEI

MIR

Bolometer Enable us to access the dynamics offundamental physics of MHD/
turbulence that were not available

IAEA FEC PARK

-9-

Topics to be addressed Mission and role of KSTAR research Advantages of tokamak plasma research on KSTAR
 Progress of the KSTAR research programHigh performance and steady-state operation
Physics of MHD/Turbulence
Progress and understanding of the ELM-crash control with RMP
Research efforts for ITER and K-DEMO Future upgrade plan Summary
IAEA FEC PARK

- 10 -

Effect of high toroidal rotation (or high edge rotation shear)on energy confinement in KSTARBeam torque is linear with
Mach number

MAST, Mi ~1.
Off-set value:
Intrinsic rotation

S.G. Lee, EX/P7-4

Toroidal rotation (Mi or torque) is a hidden parameter in energy
confinement scaling??
 Excellent correlation between the energy confinement time(tth) and Mach number (Mi) or torque L-mode and H-mode data can be combined with the rotation
related parameter (turbulence physics basis?) Further study on edge shear, counter rotation, role of intrinsic
rotation, etc. is in progress
J.S. Kang, NFRIHigh toroidal rotation speed in KSTAR may be due to nearly perfecttokamak plasma symmetry (low error field)
Beam torque is linear with the Mach number (record high Mi~0.8)
Edge rotation shear and Er are well correlated with core rotation speed

H-mode L-mode

Off-set value:
Intrinsic rotation(AU)

IAEA FEC PARK- 11 -

NBI-heated long pulse H-mode operation (> 1 min)
 Long pulse H-mode discharge with NBI & ECH•

Fully non-inductive advanced operation with high beta (N ~2.0, P ~2.5) was up to 20s.

•

H-mode was sustained over 70 s, BUT gradual performance degradation due to the heated limiterIn 2018 campaign, longer
steady-state, fully noninductive operation over
~100s will be attempted with
upgraded- Active water cooling into
PFC/Divertor- Boron powder dropper (PPPL /ORNL collaboration)

Gradual performance degradation
Due to increased wall recycling

0

10

20

30

40

50

- Additional heating (NBI, ECCD)

60
IAEA FEC PARK70

- 12 -

Exploring conventional and new operation modes for
optimal scenarios applicable to ITER and K-DEMO
76#16498ITB foot(ρ=0.46)

Ti (keV)

5
4
3
2
1
0
400

ITB @2.5 s
H-mode @4.5 s

Vt (km/s)

300

200

100

0
1.8

1.9

2.0

2.1

2.2

2.3

R (m)

Search of alternative new mode ofOperation (combine ITB and low q95)

 Broad ITB provides good confinement in the core
 Low q95 avoids harmful MHDs (e.g. NTM and ELMs)
 Sawtooth can be used for particle control and q~1 surface
can be controlled with CD.
 Expense for MHD control (ELM and NTM) can be used for
additional CD due to reduced Fbs from H-mode

IAEA FEC PARK

- 13 -

Topics to be addressed Mission and role of KSTAR research Advantages of tokamak plasma research on KSTAR
 Progress of the KSTAR research programHigh performance and steady-state operation
Physics of MHD/Turbulence
Progress and understanding of the ELM-crash control with RMP
Research efforts for ITER and K-DEMO Future upgrade plan Summary
IAEA FEC PARK

- 14 -

Theoretical model for Sawtooth instability (Full or Partial)?
 Direct q0 measurements (2015, 2016) alone
cannot validate the model#18186• During nearly four decades, there are two groupsof measurement; <q0>~1.0 and <q0>~0.8 with q0~0.07

 Supplementary experiment is essential• Excitation of double tearing modes inside the q~1
surface is consistent with the growth rates
calculated by M3DC1 with q0>1.0 in MHD
quiescent time right after the crash

Measurement of q0 for two years(2015, 2016) confirms <q0>~1.0 with
q0~0.07 (J. Ko)• Time evolution of 3/3  2/2 1/1 further supportsq0>1.0 “Full reconnection model” by Kadomtsev
is supported by the validation experiments
Y. Nam, NF 2018

Growth rates of double tearing
modes with the position of current
blip (M3DC1)
IAEA FEC PARK

- 15 -

Magnetic island (2/1) can alter the electron heat transport by
the flow and turbulence Measured Te turbulence and apparent
rotation around the 2/1 island Magnetic island modifies the poloidal flow
and the 𝑻𝒆 turbulence around itself

 Merging of turbulence near X-point and penetration
to the island can cause “minor and major” disruption

 Global XGC1 simulationshows that magnetic island
makes an 2/1 electrostatic
potential structure  nonaxisymmetric 𝐸 × 𝐵 flow
perturbation (a) gKPSP Micro-stability
analysis shows that the 𝐸 × 𝐵
shear flow at near O-point isstrong enough to suppress asignificant portion of microinstabilities (c)M.J. Choi, NF (2017), EX/11-2 (oral)
IAEA FEC PARK

J.M. Kwon, Phys. Plasmas (2018)
TH/8-1 (oral)- 16 -

Exploring the physics of transport and transient instability
using ECEI and MIR systems
 Interaction of the ELMs and Solitary
perturbation (SP: partial n=1 mode)• SP appears ~ 100 𝝁s prior to crash• Opposite rotation due to Er x B drift

JE Lee, Scientific Report 2017

 Observation of long range non-  Quasi-coherent modes (QCMs)
diffusive “avalanche” event
were observed in lowcollisionality regime of KSTAR• Voids and bumps in spatial Te
ECH and ohmic discharges.
fluctuations is shown in (a)• Symmetric corrugations in Te profile
are shown in (b) and (c)• In ECH discharge, the increased
Te/Ti by ECH injection seems todrive the QCM.

M. Choi, 4th UNIST-Kyoto
Workshop (2018)

J.H. Lee, POP (2018)

IAEA FEC PARK

- 17 -

Topics to be addressed Mission and role of KSTAR research Advantages of tokamak plasma research on KSTAR
 Progress of the KSTAR research programHigh performance and steady-state operation
Physics of MHD/Turbulence
Progress and understanding of the ELM-crash control with RMP
Research efforts for ITER and K-DEMO Future upgrade plan Summary
IAEA FEC PARK

- 18 -

Stable and robust ELM-crash control at ITER baseline
operation conditions
 ELM-crash suppression state sustained with
n=1, and RMPs (record ~34 s with n=1)

 34 sec  twall ELM-crash suppression is close to the
ITER baseline conditions (q95~3.4, andβN~1.8)n=1 full RMP under 360 degree rotation

 ELM-crashsuppressed
condition issustained under
3600 rotation at n=1
RMP: owing to thelow error fields in
KSTAR?
 Middle coils are very
important to get betterand reliable ELMcrash suppression in
KSTAR Additional mid-RMP
coil could provide
more flexibility incontrol of the ELMs
and rotation in ITER
IAEA FEC PARK

3600 rotation

3.0 kA/turnMitigation

n=2, even (T/B)+-++-+-

Suppression

n=2, even (T/M/B)+-+-+-++-+- 19 -Prediction and validation of the n=1 RMP operating window for the
ELM-crash suppression in complex KSTAR coil configuration space Offering excellent guidance tooptimize new RMPs – such as “offmid-plane” only n=1 RMP ELM
suppression in KSTAR Various ELM suppression windows
were successfully validated withdynamic RMPs

IM=0kA subspace (off-mid-plane only)

J.K. Park, Nature Physics 2018

IT=IB=5kA subspace

IAEA FEC PARK

- 20 -

Role of turbulence induced by RMP and rotation (v⊥,ped ) in
the ELM-crash suppression experiment Change of the turbulence amplitude (red box) andv⊥,ped (blue box) as the RMP current ramp up anddown (green) during ELM-crash suppression
experiment:• Turbulence amplitude: Gradual increase and gradualdecrease with a clear time delay with the RMP
current ramp up and down – slow magnetic diffusion?
• Rotation (v⊥,ped ): Bifurcation?
J.H. Lee, EX/P7-13#19355

 Poloidal coherence : Gradual increase in turbulence
level along the field line through the ELM-crash phase,-mitigation, and -suppression phases
 Radial coherence : only at ELM-crash suppression
phase – turbulence spread ?
J.H. Lee, PRL, 2016
In early study, amplitude of the
ELM (blue) during ELM-crashsuppressed period isdecreasing as the amplitude ofturbulence (red) induced by
the ramping RMP current (gold)

IAEA FEC PARK

- 21 -

Topics to be addressed Mission and role of KSTAR research Advantages of tokamak plasma research on KSTAR
 Progress of the KSTAR research programHigh performance and steady-state operation
Physics of MHD/Turbulence
Progress and understanding of the ELM-crash control with RMP
Research efforts for ITER and K-DEMO Future upgrade plan Summary
IAEA FEC PARK

- 22 -

Study of L/H transition Pth, NTV controlled rotation anddivertor heat dispersion using RMPs The effect of error fields on L-H transition
threshold (Resonant B is more critical)
19

KSTAR, 0.6MA, 1.8T, q95~4.1, ne= 2x10 m

n=1

1.6

n=2

n=1

19

-3

-4

n=2

B/B0 (~2.7x10 ) + B/B0

1.6 NRMP

n=1, -90p, ne= 1.5~1.7
n=2,

1.4

Resonant B

PTH [MW]1.2
1.00p, ne= 1.3

Non-resonant B

1.2

Y. In (oral) EX-7-1
broadening of wetted area
during RMP suppression

1.0
0.8

0.8

0

1

2
3
-4
B/B0 (10 )

4

5

0

W.H. Ko, APS 2017

1

2

3

4

5

INRMP [kA/t]

Normalized Heat flux (a.u.)

PTH [MW]

1.4-3

KSTAR, 0.6MA, 1.8T, q95~4.1, ne (10 m ) Misaligned RMP configurations could be analternative way to disperse the localized
divertor heat flux
 No electromagnetic cycling of the coils for
misaligned RMPs.

 Rotation control with NTV• Strong n = 2 field + ECH heatingyields counter-Ip rotation in core,
co-Ip rotation in outer region (first
direct measurement of NTV)• Application to the ITER initial H-modes(5 MA / 1.8 T) with ECH heating toincrease edge rotation
S. Sabbagh (Columbia U)
IAEA FEC PARK

- 23 -

Advanced shaping control and new start-up method forsuperconducting tokamak plasmas
 Improved
stability highelongation up
to 2.16(design ~ 2.0)
for high 
operation

 ITER baseline scenario withITER similar shape (ISS)Standard
shape

ITER ShapeIp [MA]

Verticallyextendedshape

D. Mueller et al. APS 2017

 Validation of Trapped
Particle Configuration (TPC)
for reliable ECH-assisted
startupq95 ≈ 3.2

βN ≈ 2
N. Eidietis, APS 2017
Comparison of a synthetic
diagnostic of the Balmer-α line
emission in the BREAK code
simulation considering the selfgenerated electric fields (a)with an experimental visible
camera image (b)• Robust startup method than theconventional field null method• Possible new automated start-up
J.W. Lee, NF 2017
IAEA FEC PARK

- 24 -

Topics to be addressed Mission and role of KSTAR research Advantages of tokamak plasma research on KSTAR
 Progress of the KSTAR research programHigh performance and steady-state operation
Physics of MHD/Turbulence
Progress and understanding of the ELM-crash control with RMP
Research efforts for ITER and K-DEMO Future upgrade plan Summary
IAEA FEC PARK

- 25 -

New NBI-2 and Helicon CD systems for KSTAR Helicon CD experiment and modeling NBI systems (6 MW NBI-1 + 6 MW NBI-2)• On-and Off-axis heating to get stable high beta operation•

Prototype 500 MHz : 0.1 MW (‘16 ~’18)• Co-current direction in both NBI-1 & 2 (for CD & high rotation)•

High power HCD (2 ~ 4 MW)• NBI-2: 6 MW, 100keV, 300 s (4MW off-axis + 2MW on-axis)• Schedule : 1 ion source (in 2018), 3 ion sources (in 2019)• Klystron : 1 MW CW tube (5 units from SLAC) (‘19)• Power supply : 2 MW ready (‘19)• Launcher : 2 MW (‘19)
Perfect alignment

1-D full wave modeling

5.5 deg .
NBI-1 NBI-2(6 MW) (6 MW)

Current drive

NBI-1(6 MW)

No dependency of coupling (A)on misalignment +/-3 degrees
measured

NBI-2 (6 MW)

Heating

Slow wave coupling canbe ignored if polarization
misalignment phi<5𝑘degrees ( ∥ 𝑘⊥ )Prototype Helicon Antenna
IAEA FEC PARK

E.H Kim, PPPL

- 26 -

Time line of research and upgrade plan of KSTAR
2017

2008

First plasma(ECH 84 GHz)

Long-pulse Heating(NBI~5.5 MW)(ECH~1 MW)

Long-pulse H-mode research• Long pulse H-mode (>70s)• Alternative modes (ITB, low q, ..)• ELM research & control (>30s)• Fundamental physics validation

2018

2020

• Stable high beta operation(N > 3.0, fBS > 0.5, Tion ~ 10 keV)
• Advanced mode develop. (hybrid, ITB, low q)• MHD & disruption control

Heating upgrade(NBI ~ 12 MW)(ECH ~ 6 MW)

2021 ~

Advanced scenario & MHD research2023 ~

Divertor upgrade(Tungsten divertor)(Detached divertor)

Steady-state & reactor mode research
CD upgrade(LHCD~4 MW)(Helicon CD~4 MW)

IAEA FEC PARK

• Tungsten divertor & active cooling• Advanced current drive(HFS LHCD, Helicon CD, etc. )• Steady-state operation (~300s)- 27 -

Summary
 KSTAR is well engineered superconducting tokamak with unique tools for advanced research Nearly perfect tokamak symmetry, intricate IVCC (top/middle/bottom) like ITER IVCC and advanced
2D/3D microwave imaging diagnostics

 Significant progress in expansion of operation regimes, validation of fundamental physics andITER/DEMO relevant research Long pulse H-mode (with ELM-crash) over 70s and ELM-crash suppressed H-mode over 30s
 Expansion of conventional operating regimes (hybrid, high beta-P, ISS, High poloidal beta, ITB, lowedge q95, etc.) and exploration of new alternative mode for minimum harmful instabilities
 Validation of fundamental physics: “full reconnection model” in sawtooth (1/1), Transport modification
by turbulence and MHD in TM (2/1), design of optimum window for RMP field penetration, role ofturbulence induced by RMP in ELM-crash suppression and turbulence physics (Avalanche and QCM) ITER relevant research results: H-mode threshold power influenced by error fields, Rotation by NTV,
Divertor heat dispersion by rotating RMPs, New start-up method, etc.

 Future upgrade plan with new ancillary systems
 NBI-2 installation (2018~) and Helicon CD installation (2019~)
 Upgrade plan (2021~) will be followed for actively cooled divertor and in-vessel components
IAEA FEC PARK

- 28 -

Thank you for your attention !

29
IAEA FEC PARK

- 29 -