Heliotron J

Studies of Configuration Control Effects
on Dynamic Behavior of Heliotron J Plasmas
Presented byMIZUUCHI Tohru
for Heliotron J Team

IAE, Kyoto University
This work is performed with the support and under the auspices of the Collaboration Program of the Laboratory forComplex Energy Processes, IAE, Kyoto Univ. and Kyoto Univ. 21st century COE Program “Establishment of COE on Sustainable Energy
System” as well as the NIFS Collaborative Research Program.

Studies of Configuration Control Effects
on Dynamic Behavior of Heliotron J Plasmas
Heliotron J
Heliotron JOutline

IAE, Kyoto University
IAE, Kyoto University

 Introduction
 Control of Field Configuration
 Control of vacuum configuration
 Effects of plasma pressure & current(Numerical calculation)
 Dynamic Behavior during a Discharge
 Change of Field Topology by Plasma Current
 Onset condition for Transition Phenomena for
NBI-only Plasma SummaryIAE, Kyoto University

 Basic idea of the concept:– Bumpiness control in thefield harmonics for better
confinement– Introduction of magnetic
well for MHD activity
control One of the major objectives ofHeliotron J program:

R (m) / "Coner"
12

1.2

1.4

1.6OMS
confinement
region1.5

10.8– Examination of the configuration effects
on the plasma performance.
» Rotational transform control, ι/2π
» Bumpiness control, εb=B04/B00|B| (T)

Heliotron JThe Heliotron J device isa flexible concept-exploration facility
for the helical-axis heliotron concept.

confinement
OMS
region0.9
11.1

R (m) / "Straight"» Effects of non-inductive plasma current(bootstrap, NBCD, ECCD)
1.2

The configuration can be controlled
by changing the five sets of the coil current
inHeliotron
J.
Heliotron JIAE, Kyoto University
Example of Vacuum Rotational Transform Control
Heliotron J (vacuum)

Ad. Ip8/13

0.60

ι/2πSTD

0.55

4/7
12/22
8/15
12/23
4/80.50
Sub. Ip) The bumpiness is mainly
controlled by changing thecoil current ratio of two
toroidal-coil sets, ITA : ITB.
) ι(r)/2π|vac can be controlled
by mainly changing thecurrent ratio of the helicalcoil to the toroidal coils.

8/17

0.00

0.10
0.20
<r> (m)) The vacuum ι/2π is usually set not to cross the low-mode rational.
) However, plasma pressure and toroidal plasma current can modify theι/2π-profile and make the field topology change in the core and peripheral
regions.

Effect of Plasma Current on Field Topology
vacuum- HINT2 Calculation for STD (ι(a)/2π ≈ 0.56) configuration β(s) = 0.5·(1-s)2 [%], jp = jp0·(1-s)2Heliotron JIAE, Kyoto University

Plasma current can modify not only the ι/2π-profile
but also the “shape” of magnetic surfaces.
 Asymmetric effect of plasma current due to the “proximity” toa low-mode rational number.
ad. 4kAad. 2kAad. 1kA0kA

β (s)=b0(1-s)2, β 0=0.5 %jp(s)=j0(1-s)2HINT2

Ip=4kA2kA

ι/2π

0.60

8/13

1kA0kA 4/7-1kA-2kA

0.50

-4kA

00.1
<r> (m)

12/22
8/15
12/23
4/8

0.2

sub. 1kA

sub. 2kA

sub. 4kA

Behavior of MHD-activity indicates the change ofι/2π(r) caused by plasma current.
IAE, Kyoto University
P2-046 (Wed.) G. Motojima,
et al.

Heliotron J In this vacuum condition (ι(a)/2π = 0.49), there is

no rational of m/n = 2/1.
 However, The m/n=2/1 resonant mode has been
observed in ECH + Co-NBI plasma.
 This indicates that ι(r)/2π is modified by theplasma pressure and toroidal current, resulting
in crossing the rational of m/n = 2/1.
19-36

n=2*10 (m )*(1-ρ )2 2

T =0.45(keV)*(1-ρ )eRotational Transform

0.52

2 2T =0.15(keV)*(1-ρ )iβ(0)=0.25 %

0.51
0.50

ι/2π0.49
0.48
0.47

2 2j(ρ)=(1-ρ ) (1kA)
20.46
0.45
0.00

4j(ρ)=ρ -ρ (1.5kA)
2VMEC2000

4j(ρ)=1+4ρ -5ρ (2.5kA)
vacuum

0.20

0.40

0.60
ρ

0.80

1.00

Plasma current can modify the edge field topology.
- Experimental observations Heliotron JIAE, Kyoto Universitytarget

X

RtargetTarget Camera Image

Rtarget (m)

1.34

HJ/MB

Zt= -0.215m

1.32
1.30
1.28
1.48

RDPA (m)Intensity profile along the target edgetime

#22935(B>0)#22936(B>0)

ECH+NBI

1.46
1.44
1.42
1.40
-0.5

00.5

11.5

2Ip (kA)
T. Mizuuchi, et al., Nucl. Fusion 47, 395 (2007)

X

2.5

Examples of Transition to improved modein ECH-only & NBI-only Plasma
Heliotron JIAE, Kyoto University

ECH-only, STD
ECH

1.0(a.u.)

0.00.1W(kJ)

Gas Puff
Hα #11.5

1Is#11.5

02.00.1
ne L

mWb

1019 m-20

SOL Probe

Co-NB

03 x1019m-3
Gas Puff08

ECE6

IHα0.0
Add.

0.0kA

ECH

01.0-1.0

3 #11948

ne(a.u.)2.0

STD
PINJ = 460 kW, Gas:H2, NBI:H2

HJ21448 (Rev. B)

Ip
200

250time (ms)

0(A.U.)
180200220time (ms)240

Observation of peripheral plasma turbulenceusing a fast camera in Heliotron J
Heliotron JIAE, Kyoto University

 In Heliotron J, the observation ofperipheral plasma turbulence by using
a fast camera has been performed.
80kFPS

Object lens

 In this setting, we observed

perpendicularly the edge plasma.
 In the same toroidal position, amovable Langmuir probe set isinstalled.

Movable probeFast camera images reveal the filamentary
structure of the edge plasma perturbation.
Filamentary structure seems to move crossing the magnetic field.
Heliotron J

IAE, Kyoto UniversityExample for ECH-only plasma
Filamentary Structure

Probe

80kFPSTime duration of each frame is about 9.524 μsdownward

B direction
timePixel data at the probe position

When the “filament” hits the probe, theion-saturation current shows a burst.
Ion-saturation current

Motion of the 2D phase pattern for ＃21448 shot
(ECH-only plasma)- 80kFPS, ~ 8.8kHz BP filter -Heliotron J

HJ21448 (Rev. B)(a.u.)

2.0

Gas Puff

0.1

Hα#11.5

Probe  The motion of the0.1

mWb1019 m-2

B direction

102.0

2D-phase images of~8.8kHz are shown.
– All phase images
above 5kHz weresimilar in this shot.

0Is#11.5



1.00.0(a.u.)

Filamentary Structure

ECHIAE, Kyoto University

neL0SOL Probe

filamentary structure
seems to be reversed
when the transition
takes place.

1.0
ECE6
0.0

-1.0

Add.

kA

0.0
Ip
200

250
time (ms)

220 - 250ms~8.8kHzP1-020N. Nishino, et al.

Configuration effects on the global energy confinement
have been examined by controlling the vacuum ι/2π(a).
Heliotron J

IAE, Kyoto University Transition to better confinementτexp/(f×τISS04)

mode is observed in higher ne region.
 The rotational transform windows forthe high quality H-mode(τexp/ (f×τISS04) > 1.5) are close to thelow-mode rationals of the vacuumι/2π(a).
9 The influence of the topology(“shape”) of the magnetic
surfaces with regard to thepoloidal viscous damping rate has
been discussed.

ι(a)/2π|vacF. Sano, et al., Nucl. Fusion 45 (2005) 1557.

How about non-inductive current effects?
⇓NBI-only plasma instead of ECH+NBI→ simple situation→ current control in higher ne (>ne,th)Comparison between Co/CTRConfig. ; ι(a)/2π=0.54
plasmas for ι(a)/2π = 0.54. #25892(Co-NB),#25989(CTR-NB)

natural rational surface of m/n=15/8 exists (ρ=0.87)
 Almost the same injection power– PINJ = 0.58MW(Co), 0.56MW(CTR)
 Achieved toroidal current− Co : Ip ~ +3kA ↔ CTR : Ip ~ -1kA
− The current direction is consistent withNBCD
 Bootstrap ( Co direction) + NBCD (Co or CTR)
 ne = 2.0 ~ 3.0 x 1019 m-3
 In Co-NBI, the transition were observed,

but no transition in CTR-NBI.
) Difference in Pth for transition due to Position of rational surface, Shear, Shape of LCFS, Direction of momentum input ?

2 ECH

CTR-NB
NBI

0ne(x1019m-3)

at ι(a)/2π ~ 0.54

Co-NB
IAE,
Kyoto University

202Co

Ip(kA)

 Comparison between Co- & CTR-NBI plasmas

W(kJ)- No transition in CTR NBI -0-2 CTR
6IHα(A.U.)

Heliotron J

420180200 220time (ms)240For NBI-only dischargesin εb ≈ 0.15 (high-εb) and 0.06 (medium-εb)cases. (ι(a)/2π|vac~0.56)

0 No transition in low εb (≈ 0.01) case.
− Cf. Transition can be rather easily
observed for ECH+NBI discharges.
− Pth or ECH effects?
S. Kobayashi, et al.,EPS2007, H-mode Workshop (Sept., 2007)

Co-NB

Delay Time180(A.U.)200
220time (ms)240

Dependence
of delay time on PNB
50

delay time (ms)→ almost the const. abs. efficiency

IAE, Kyoto University

ECH08

 The delay times for two configurations

are almost the same and decrease asincrease of Pinj.
ne ~ 1.5-2×1019 m-33 #11948

IHαHeliotron JW(kJ)

Time delay Δt from the start of NBI to theonset of the transition is observed.

4030
201000High εbMedium ε200Pb400(kW)PortThrough600

The transition is observed when the plasma
current reaches a critical value.
Heliotron JIAE, Kyoto University

Dependence of IP at transition on PNB

depends on the configuration;
0.7±0.1kA in middle εb1.3±0.2kA in high εb cases.
 The observed time delay would be related
to the growing-up time of the current.

2Ip @ H α drop (kA) The critical value of the plasma current

High εb1Dependence of delay time on PNBHigh ε00

Medium εbb

Medium ε200
Pb400(kW)600

Portthrough− In high εb case, higher Ip was required.

delay time (ms)504030201000High εbMedium ε200
Pb400(kW)600

PortThroughThe effects of the plasma current on the field configuration should depend on thevacuum rotational transform. → ι(a)/2π|vac-scan experiment.

The critical current for NBI-only plasmastrongly depends on ι/2π.
Heliotron J

IAE, Kyoto University

Radial profile of rotational transform

12/23 12/22

1

8/17 4/8 8/15

4/7

8/13

8/13

0.60(High εb)

4/7

ι/2π

Ip (kA) (kA)
Ip@transition

2

Heliotron J (vacuum)

0.55

12/22
8/15
12/23
4/8

0.50

8/17

0.00

0.10
<r> (m)0.20) ι(a)/2π|vac –scan for NBI-only plasma(mainly the medium-εb condition)
00.45
0.50.55
0.60.65 ) the critical current exists for all config.
ι(0)/2π (=1/q)) The value systematically decreases asι(a)/2π|vacincrease of ι(a)/2π|vac) So far, the spontaneous transition was0.25 MW < Pinj < 0.6 MW,
observed only in Co-NBI (ad. NBCD) plasmas
19-3
ne ~ 1.5-2×10 m(Pinj < 0.6 MW)

Plasma current control by ECCD scenario
is effective in rather low-density plasma.
Heliotron JIAE, Kyoto University
I-17 (Fri.) K. Nagasaki,et al.

 The density dependence of EC

current for three field configurations.
9 the BS current is eliminated.
 The maxi. EC current of 4.6 kA is
attained at the ripple top heating.
 The EC current flows in the opposite
direction at the ripple bottom heating,and its amplitude is one-third as low
as the ripple top heating.
 The transition study in ECH-onlyplasma with ECCD control would give
us useful data to understand thephenomena.

Does a high ECCD current opens a new window for
the transition in lower density region?.
Heliotron JIAE, Kyoto University

HJ28275

 A spontaneous change to a better

1.0mWb

ECH

confinement mode was observed ina high ECCD current discharges.
(Low-εb, ι/2π(a) ~ 0.56,
ECH-only with PECH > 0.3 MW) The line-averaged density is much
lower than the critical low-density
limit observed in the previous
experiments for STD configuration.

ad.

(a.u.)

2.0

 No enough experiments, from this point

Gas Puff(a.u.)

0.0
0.02

Hα#11.5

0.01

kA1019 m-2

00.4
0.2

0.1

00.00
Ip

-1.0
-2.0
-3.0

200

250time (ms)300of view, in sub. high ECCD condition.

Studies of Configuration Control Effects on Dynamic Behavior of Heliotron J Plasmas
Heliotron JSummary

IAE, Kyoto University In recent Heliotron J experiments, we are interested in theIAE, Kyoto University
configuration effects on the plasma performance especiallyrelating to the field modification by non-inductive current.

Heliotron J⇐ prediction of free-boundary equilibrium calculations,⇐ MHD-activities relating to resonance condition which does not exist
for vacuum condition,⇐ the shift of the diverter footprints during a discharge.

 Transition to an improved confinement mode in NBI-onlyplasma has been investigated, focusing on the onset conditionof the transition.
– Under the experimental condition (Pinj and mag. configuration), notransition has been observed in the CTR-NBI-only plasmas.
– Transition was observed for medium- or high-εb, but not for low-εb.
– The existence of the critical current for the onset of the transition isfound out in NBI-only plasma.
– This critical current depends on ι(a)/2π|vac and the bumpiness, but
is independent of Pinj.

Thanks for joining our experiments
and fruitful discussions!
Heliotron JIAE, Kyoto University

KYOTO UNIVERSITY
F. Sano, T. Mizuuchi, K. Hanatani, K. Nagasaki, H. Okada, S. Kobayashi,Y. Ijiri, T. Senju, K. Yaguchi, M. Shibano, K. Tohshi, K. Sakamoto
K. Kondo, Y. Nakamura, H. Arimoto, G. Motojima, S. Watanabe, F. Hamagami,
D. Katayama, H. Matsuoka, A. Matsuyama, K. Mukai, K. Murai, A. Nakajima,
H. Takahashi, H. Yasuda, K. Hosaka, Y. Kowada, S. Mihara
S. Murakami
S. Yamamoto

NATIONAL INSTITUTE FOR FUSION SCIENCE
T. Mutoh, S. Okamura, K. Y. Watanabe, M. Yokoyama, M. Isobe, T. Minami,Y. Suzuki, Y. Yoshimura

HIROSHIMA UNIVERSITYN. Nishino

UNIVERSITY TSUKUBA
Y. Nakashima

CIEMAT
A. Fernández, A. Cappa, E. Ascasibar

SWIP
Z. Feng, Q. Yang

Please visit our sessions andenjoy discussions on our presentations!!
Heliotron J

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

IAE, Kyoto University

P1-020N. Nishino, et al.,Measurement of peripheral plasma turbulence using a fast camera
in Heliotron J
P2-034
S. Yamamoto, et al.,Energetic ion driven MHD instabilities and their impact on ion transport
in Heliotron J plasmas
P2-046
G. Motojima, et al.,Study of toroidal current effect on rotational transform profile
by MHD activity measurement in Heliotron JP2-054
Y. Nakashima, et al.,Analysis of neutrals in helical-axis Heliotron-J plasmas
using the DEGAS Monte-Carlo code
P2-071
S. Kobayashi, et al.,Observation of Ion tails in ECH/ECCD plasmas in helical devices
P2-091
S. Watanabe, et al.,Measurement of radiation profile at density ramp-up phaseby using AXUV photodiode arrays in Heliotron JI-17
K. Nagasaki, et al.,ECCD Experiments in Heliotron J, TJ-II, CHS and LHD