OV/1-1
Extension of Operational Regime of LHD
towards Deuterium ExperimentY. Takeiri for LHD Experiment Group
National Institute for Fusion Science,National Institutes of Natural Sciences, JapanSOKENDAI, Japan

26th IAEA Fusion Energy Conference, Oct. 17-22, 2016, Kyoto, Japan1

Significance of LHD in the world fusion research• High-performance steady-state plasmas is required to realize fusion reactor• LHD is based on Japan-originated heliotron concept, and the world-largest
class of superconducting fusion device• LHD has demonstrated its inherent advantage for steady-state operation
Duration: 47min.39sec
2keV, 1.2×1019m-3, 1.2MW, 3.36GJ

towards steady-statehigh-performance regime

2Progress towards high-performance plasmas
 Steady increase of plasma parameters in recent years
 Coming deuterium experiment should further extend the parameters
towards reactor-relevant regime, in which advanced research can be
performed for establishing firm basis for steady-state helical reactor
Parameters

Achieved

Ti

8.1 keV (ne = 1×1019 m-3)Te

20 keV (2×1018 m-3)
10 keV (1.6×1019 m-3)

Density

1.2×1021m-3 (Te = 0.25 keV)

β5.1 % (BT = 0.425 T)
4.1 % (1 T)
54min. 28sec(0.5MW, 1keV, 4×1018m-3)
47min. 39sec.
(1.2MW, 2keV, 1×1019m-3)

Steady-stateoperation

Key physics
Ion ITB
Impurity hole

Super densecore
MHD in currentfree plasmas

Target10 keV(ne = 2×1019m-3)
10 keV(2×1019m-3)
4×1020 m-3(Te = 1.3 keV)
5%(BT = 1 - 2 T)

Dynamic wall
retention

1 hour
(3 MW)

Electron ITB

3Contents
1. Introduction on LHD
2. Recent progress• Extension of operational regime- high Ti, Te- high β,• Impurity transport• LHD as the advanced academic platform
3. Deuterium experiment- Objects- Schedule- Hardware improvement (negative-ion based NBI)
4. Summary

4Introduction
Large Helical Device (LHD), the largest helical device
LHD is optimized heliotron with simply and continuously wound helical coils.
The superconducting LHD has been
operated since 1998 without any
severe cryogenic troubles.
FIP/3-4Rc, Takahata

Specification• Helical mode numbers:
l/m=2/10• All superconducting coil system• Plasma major radius:
3.42-4.1 m• Plasma minor radius:0.63 m• Plasma volume:
30 m3• Toroidal field strength:
3T• 20 RMP coils

Heating Systems• negative-NBI x 3
H-inj. 180 keV, 16MW
• positive-NBI x 2
H-inj. 40-50 keV, 12MW
• ECH (77 GHz x 3, 154 GHz x 2, 82.7 GHz, 84 GHz), 5.4MW (0.6 MW CW)
5• ICH (20 –100 MHz) x 6 3 MW

Contents
1. Introduction
2. Recent progress• Extension of operational regime- high Ti, Te - high β,• Impurity transport• LHD as the advanced academic platform
3. Deuterium experiment- Objects- Schedule- Hardware improvement (negative-ion based NBI)
4. Summary6Extension of temperature regime
Plasma control and physics findings extended temperature regime
PPC/1-1, Takahashi (Wed)10

Extended
Regimeafter FEC2014

Te0[keV]86• ICH/ECH wall conditioning iseffective to reduce recycling,leading to enhancement of NB
penetration to the core region.
EX/P8-2, Tsujimura

4~FEC2014
After FEC2014
After FEC2014(fine-tuned ECH)

20

• Ti had been extended to above 8keV (ion ITB) (FEC2014, Nagaoka)

0246
Ti0 [keV]810• Feedback ECH optimization forfine-tuned ECH is applied onto
high-Ti plasmas
 Extended temperature regime tohigh Ti and Te, simultaneously
reaching around 6 and 8 keV,
respectively.
7

Study on Impurity hole has progressed
Density profile: Carbon and helium ions are hollow, while bulk ion is peaked
Radial density profiles of bulk and impurity ions are simultaneously measured by CXS
A. Perek, K. Ida et al., to be submitted to NF (2016).

peaking factor(quasi steady-sate)

Ti ~ 5-6 keV
Te~ 3-4 keVH: peakedC, He: hollow
8Strategy of high-beta plasma production
High beta has been realized with two scenarios in previous experiments

Standard scenario (broad P-profile)- Low Ap configuration to increase heating
efficiency, and to optimize transport, MHD- <β> of 5.1 % was obtained at low-Bt

SDC (Super Dense Core) scenario(peaked P-profile)- Peaked P profile by multi-pellet injections- High density (> 1020 m-3)

StandardScenario

SDCScenario

Ap = 6.6(2005~)
Ap = 6.3(2004)Ap = 5.8(~2003)

Towards more reactor-relevant research,high beta plasmas in low-collisional
regime are necessary
Realization of high temperature and high beta
plasma in inward shifted configuration

9

High β trial in low collisional regime
High beta operation has been extended to low collisional regime
EX/4-4, Sakakibara (Wed)Raxv = 3.56 m, Bt = -1T, Ap = 5.8
EX/P8-9, Tokuzawa
Appearanceof locked
mode

Limit

Magnetic shear
Multi-pellet injections (Maximum beta)⇒4.1 %（Te0 = 0.9 keV, ne0 = 6×1019 m-3)
Gas puffing (Quasi-steady state)⇒3.4 %（Te0 = 1.2 keV, ne0 = 3×1019 m-3) 10

Impurity transport in core region
Strong suppression of accumulation behavior is observed in
impurity accumulation window, during high power heating
EX/P8-4, Nakamura

Impurity accumulation window exists withboundaries determined by1) Er
2) edge stochastic layer
3) NBI (power, torque), etc.
• experimentally confirmed• newly found• including impurity hole in high T regime
TH/P2-3, Nunami

11Impact of NBI torque input on impurity transport
It is suggested that NBI torque plays animportant role in exhausting C impurity
When NBI torque input direction is switched fromco- to ctr-injection,
 little change in Te and Ti is observed drastic change of nC profile is observed in
response to the rotation parameters (Vt and uc’) nC profile is hollow in the co-injection
 nC profile is observed to be peaked in the ctrinjection
On the other hand, it is also observed that thecarbon density profile becomes hollow withincreasing in the Ti-gradient.
EX/P8-4, Nakamura

12

Impurity transport in stochastic region
Impurity flow direction in stochastic
region is determined by the balance
between friction and thermal forces
Agreement between experimental andnumerical (EMC3-EIRENE) results wasconfirmed.
friction force
stochastic region

coreLCFS

divertor

thermal force

EMC3-EIRENE model (expectation)
C-flow observed by VUV spectroscopy• Downstream flow towards the divertor
plate was experimentally observed.
• Impurity outboard flow is enhanced
as ne increases.
EX/7-2, Oishi (Fri) 13

Particle balance in steady-state plasma
Wall does not saturate during 48 min.
discharge due to deposition layers
Dynamic change of He retention
Three different retention phases:
1. quite high wall pumping
by implantation in divertor plates
2. inventory declination
by out gassing due to increased
surface temperature of divertor tiles
3. continuous wall pumping
by deposition layer on the first wall
can be explained by the global particle
balance and plasma-exposed sample
analyses.
Deposition layers continuously grows
during the long-pulse discharge.
EX/P8-3, Motojima

14

LHD as the advanced academic platform
Hysteresis intransport relation
OV/P1-8: K.ItohImpact of stochastization Impact of high-Te laboratory
plasma on fundamental
on momentum transportphysics, industry
EXC/P8-7, Ida
C. Suzuki, EPS2016 Invited Talk
New!

67Ho
68Er

New!
K.Ida et al., Nature
Communications 6 (2015) 5816.

69Tm
70Yb

K.Ida et al., NF 55 (2015) 013022.
Wavelength (nm)

EXC/P8-607:
T.Kobayashi

EX/P8-14, D. Kato

Abrupt excitation of a linearly stable
mode: subcritical instability
T. Ido, et al., PRL116 (2016) 015002 .
M. Lesur, et al., PRL 116 (2016) 015003.
TH/P4-11, Wang

15

Contents
1. Introduction
2. Recent progress• Extension of operational regime- high Ti, Te - high β,• Impurity transport• LHD as the advanced academic platform
3. Deuterium experiment- Objects- Schedule- Hardware improvement (negative-ion based NBI)
4. Summary
16

Objectives of LHD deuterium experiment
1. High-performance plasmas through confinement
improvement
 Scientific research in more reactor-relevant conditions
 Full of research opportunities

2. Clarification of the isotope effect on confinement
 Long-standing mystery in world fusion research Needs to be understood towards burning plasma

3. Demonstration of the confinement capability ofenergetic ions in helical systems
 Perspectives towards helical reactor

4. Isotope effect on PWI Global particle balance for hydrogen isotopes
17

Schedule for LHD deuterium experiment- Concluded the agreements for LHD deuterium experiment with local governments in 2013
- Deuterium experiment will start in March 2017 and will last 9 years
2013

2016

2017

Deuterium Experiments (9 years)

Preparation for D-experimentHydrogen Experiments

Upgrade for Heating System(NBI, ECH, ICRF)

Upgrade for Diagnostics System(Neutron diagnostics, etc.)

Installation of Safety Equipments(Tritium removal system, etc.)

Remodeling of Building and Facilities

Preliminary Experiments for Commissioning

Legal License

Deuterium Experiments
Calibration Experiments for Neutron Diagnostics

Agreements
for D-exp.

2025

Closed Helical Divertor withPumping System
NBI: 18MW (60-80keV, 2sec)
14MW (180keV, 2sec)
ECH: 6MW-3sec, 1MW-CW(77GHz & 154GHz)
ICRF: 6MW-5sec, 2-3MW-CW
Neutron Diagnostics
High-energy Particle Measurement
3-Dimensional Measurement
High-Accuracy Measurement
Divertor Diagnostics
Steady-State Data Acquisition

Targetin D-Exp.

Ti = 10keV
at 2×1019 m-3<β> ~ 5%
at Bt=1TnTτ
>1×1020
m-3 keV s3MW Heatingfor 1 hour

PWI Laboratory18

World-leading negative-ion-based NBIs
Negative-NBIs reliably inject 15MW of 180keVH-beams into LHD plasma.
For D-beam injection, upgrade of the negative
ion source performance with understanding ofthe source physics is being carried out.
Such engineering and physics research should
contribute to ITER-NBI development.

Kisaki, FIP/1-4 (Mon)2024 20 22 18 16 14
Z [mm]

Source plasmaNegative-ion flow near PG
10864

High current of>30A (per source)
is availableYZ• Negative-ion richplasma (nH->>ne) isproduced near PG.

Beam

PG EGGG• Negative-ion flow in thesource plasma isevaluated for the firsttime.

19

Helical reactor (FFHR-d1) design and R&D
1. Construction/maintenance scenario

2. Development of new materials
Low activation vanadium alloys
Highstrength

NIFS-HEAT-2 (high-purity, ▲●)and US (lower- purity)

NIFS-HEAT-2 ingot(166 kg)

Sagara, FIP/3-4Ra (Sat)High

3. Integrated blanket system study
by circulation loops

Vickers
hardness, Hvstrength

180150High temperature& long life

Advanced Cu alloy for divertor
300gf

32h

12090

Alloying
time 1h60

Pure
Cu

30
000.1

250rpm-1h
950⁰C-150MPa8h
4h

Glidcop™
100 μm250rpm-32h
950⁰C-150MPa

MA-HIP(250rpm)(New Process)
0.2

0.3

0.4

Mechanical
Alloyingand Hot
IsostaticPress

100 μm

1.0 1.1 1.2

1.3 1.4

1.5

Smaller grain size

Average grain size, d-1/2 (μm-1/2)

4. Divertor mock-up and heat load tests
High heat
flux testfacilityOroshhi‐2: Operational Recovery Of
Separated Hydrogen and Heat Inquiry-2

20

List of Presentations on NIFS activities
Overview
OV/1-1

Y. Takeiri

OV/P-8K. Itoh

Extension of Operational Regime of LHD towards Deuterium
Experiment
Hysteresis and Fast Timescale in Transport Relation of Toroidal
Plasmas

Oral
Enhancement of helium exhaust by resonant magnetic
perturbation fields
Extension of High-beta Plasma Operation to low collisional
EX/4-4
S. Sakakibara
RegimeObservation of carbon impurity flow in the edge stochastic
EX/7-2
T. Oishimagnetic field layer of Large Helical Device and its impact on theedge impurity control
Two Conceptual Designs of Helical Fusion Reactor FFHR-d1A
FIP/3-4Ra A. Sagara
Based on ITER Technologies and Challenging Ideas
Extension of Operational Regime in High-Temperature Plasmas
PPC/1-1
H. Takahashi
and Effect of ECRH on Ion Thermal Transport in the LHD
Multi-Machine Analysis of Turbulent Transport in Helical Systems
TH/6-2
A. Ishizawa
via Gyrokinetic Simulation
EX/1-4

O. Schmitz

21

List of Presentations on NIFS activities
PosterA. Dinklage

EX/P8-5

H. Xianli

FNS/P5-8

EX/P6-19 N. Ashikawa

EX/P8-6

B. Peterson

MPT/P5-19 Y. Nobuta

EX/P8-1

EX/P8-7

K. IdaMPT/P5-21 T. Nagasaka

EX/P8-10 S. Ohdachi

EX/P8-8

Y. Narushima

MPT/P5-23 A. Itoh

EX/P8-11 K. Tanaka

EX/P8-9

T. Tokuzawa

TH/P1-4

K. Ichiguchi

EX/P8-12 X. Du

FIP/3-4Rb H. Hashizume

TH/P1-5

H. Miura

EX/P8-13 T. Ido

FIP/3-4Rc

K. Takahata

TH/P2-2

M. Nakata

EX/P8-14 D. Kato

FIP/P4-37

M. Tokitani

TH/P2-21

S. Murakami

EX/P8-15 T. Kobayashi

FIP/P4-41

Y. Hatano

TH/P2-3

M. Nunami

EX/P8-2

T. Tsujimura

FIP/P4-7

H. Nakanishi

TH/P4-11

H. Wang

EX/P8-3

G. Motojima

FIP/P7-11

N. Yanagi

TH/P6-17

H. Hasegawa

EX/P8-39 T. Goto

FIP/P7-2

J. Miyazawa

EX/P8-4

FIP/P7-35

M. Yokoyama

EX/P5-1

Y. Yoshimura

Y. Nakamura

K. Ogawa

22Summary LHD has progressed as a large-scale superconducting
device since 1998, without any severe cryogenic troubles
 Demonstration of steady-state operation as inherent
advantage of helical systems
 Improvement of plasma performance based on extended
experimental capabilities and physics findings
 Further plasma performance improvement is envisaged in
the coming deuterium experiment, to provide firm basis forhelical reactor design
 LHD as the academic platform, to provide opportunities forchallenging and cutting-edge research

23

Join us for the coming
deuterium experiment !

24