Toroidal rotation dynamics in pedestal and core across ELMs in JT-60U
Off-axis Current Drive and Current Profile Control in JT-60U
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Transcript of Off-axis Current Drive and Current Profile Control in JT-60U
Off-axis Current Drive andCurrent Profile Control in JT-60U
T. Suzuki, S. Ide, T. Fujita, T. Oikawa, M. Ishikawa,G. Matsunaga, M. Takechi, M. Seki, O. Naito, K. Hamamatsu,M. Sueoka, H. Hosoyama, M. Nakazato, and the JT-60 Team
Japan Atomic Energy Agency
21th IAEA Fusion Energy Conference(19 Oct. 2006, Chengdu) EX/6-4 (17+3min.)
This work was partially supported by Grand-in-Aid for Young Scientists (B) No. 18760650 and Grand-in-Aid for Scientific Research No. 18560798 and 16082209 from MEXT.
JT-60U
Introduction
Optimization or control of q/j profile is crucial. For higher confinement and stability such as
in ITER SS & hybrid scenarios In a self-organized plasma, real-time feedback
control is essential. Minimum but efficient control is preferable.
Minimum q (qmin) is one of the key parameters for stability at high and resulting confinement. Raising qmin can avoid low m/n MHD, such as
NTM and sawtooth. For the qmin control, off-axis current drive is
required. LHCD & NBCD
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Contents
Current drivers and MSE diagnostic for current profile measurement
Real-time control of qmin using off-axis LHCD in high plasmas
Measurement of beam driven current profile by off-axis NBCD
Summary
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Off-axis NBCD 2MW/2MW for co/ctr Investigated here
Off-axis Current Drivers and high resolution MSE diagnostic in JT-60U
LHCD (2GHz, <1.5MW for co) Continuous control of power and N//
possible at every 10ms Used as current driver for real-time
control of qmin
q(r) measurement using 30ch MSE dR~0.06-0.1m (a~1m) at every 10ms for real-time calc.
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Real-time control of qmin using off-axis LHCD in high plasmas
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In 2006, qmin is controlled in real-time using LHCD in high plasmas
In 2004, q profile control at low demonstrated Real-time evaluation of q(r) using MSE Real-time control of CD location through N//
In 2006, qmin control at high for better core performance
Control of key parameter at high : qmin
Real-time control of LH power: PLH ILH
N// is fixed to keep CD location at higher Te region for better CD efficiency.
LH power control: dPLH/dt=-(qmin - qmin,ref) : positive constant LH power increases when qmin < qmin,ref.
JT-60U
Real-time qmin control demonstrated atN=1.3-1.6, fBS=0.46, fCD=0.87
High-p ELMy H-mode Ip=0.8MA, Bt=2.5T, q95=5.8,
ne=1.8x1019m-3, p=1.2-1.5.
qmin followed the given reference qmin,ref. =2MW/s
Without control, qmin goes down to 1.3.
1.31.7
interlocksby arcing
N//=1.7
qmin raisedqmin=1.7
0
1
2
3
4
0 0.2 0.4 0.6
e46965
q(t=7.00s)q(t=8.00s)q(t=13.00s)q(t=14.80s)
ρ
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0
0.2
0.4
0.6
0.8
0 0.2 0.4 0.6 0.8 1ρ
=7.0t s
=13.5t s
Complex behavior in current profile evolution during qmin control in high
LHCD spatially localized at ρ=0.3-0.5 decrease j by reduction of jOH inside
ρ=0.3 Complex interaction between j, p, and
Te(or NC) at high during qmin control
q(r) change through qmin control
Te increases
jOHNC and jBS increase
qmin decreases
Control system increases PLH
contour plotj increase
jLH
jBS+jOH
qmin control
0
4
8
0 0.2 0.4 0.6 0.8 1ρ
=12.0t s
=13.0t s
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m/n=2/1 NTM in high-p mode plasma atN~1.7, p=1.5
Ip=0.8MA, Bt=2.4T, q95=5.4
22% decrease in Wdia
qmin rises above 2
overshoot of control
during qmin control to 1.7
m/n=2/1 NTM disappears Wdia recovers
Central ne, Te, Ti increase.
No change in peripheral
MHD stabilization and confinement recovery by qmin control in high
m/n=2/1 NTM
confinementrecovery
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Measurement ofbeam driven current profile
by off-axis NBCD
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Off-axis NBCD investigation for real-time current profile control
Off-axis NBCD has been known to drive current, raise central q and decrease Vloop in JT-60U. working as one of standard off-axis
current drivers in JT-60U But, off-axis NBCD “profile” has not
been fully recognized, yet. difficult to measure, veiled by large
Ohmic current. Important to know its character in order
to use for optimization and real-time control of j(r).NBCD profile measurement exploiting progress in diagnostics (high resolution
MSE, neutron emission profile) flexible NBI system (perp. NB w/o
NBCD) improvement in analysis technique
typical configuration for off-axis NBCD
JT-60U
Spatially localized off-axis NBCD profile is measured using MSE diagnostic.
Ip=1.2MA, Bt=3.8T, q95=5.4, fixed ne=3.3x1019m-3, ELMy H-mode, No MHD except ELMs
Temporal evolution of increment of current I from reference current profile, measured by MSE spatially localized NBCD at ρ=0.65-0.8
Off-axis beam driven current profile jBDdS agrees with increase in neutron emission Sn(r) representing beam population profile.
th-th neutron < 10%, bulk density constant
tangential minor radius ρmin of diag. sight line
0
0.5
1
1.5
0 0.2 0.4 0.6 0.8 1ρ
before NBCD=8.9t s
during NBCD=12.5t s
46214e
current increase
0.9
1
1.1
1.2
0 0.2 0.4 0.6 0.8 1ρmin
=13.0t s( )during NBCD
0 0.2 0.4 0.6 0.8
e46214
ρ1
measurementusing MSE
15
10
5
0
(reference)
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0 0.2 0.4 0.6 0.8
e46214
ρ1
15
10
5
0
measurement
0 0.2 0.4 0.6 0.8
e45466measurement
1ρ
15
10
5
0
Measured IBD agrees with calc., but CD location in calc. shifts inward than meas.
Ip=0.8MAIp=1.2MA Measured off-axis NBCD is spatially localized both at Ip=0.8&1.2MA.
consistent with neutron emission profile
Peak CD location in calc. shifts inward than exp. by dρ~0.2 in Ip=0.8&1.2MA. But, total NBCD current
in exp. agrees with calc. in Ip=0.8&1.2MA.
Difference between CD locations in exp. and calc. further study required
12732kA
103kA
10641kA
90kA
0.9
1
1.1
1.2
0 0.2 0.4 0.6 0.8 1ρmin
=13.0t s( )during NBCD
0.9
1
1.1
1.2
0 0.2 0.4 0.6 0.8 1ρmin
=11.0t s( )during NBCD
calculationcalculation
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Summary
Real-time control of qmin was demonstrated in high plasma having N=1.3-1.6, fBS=0.46, fCD=0.87. qmin was evaluated by MSE, and current profile was modified by off-
axis LHCD at ρ=0.3-0.5. qmin followed the given reference rising in time. Complex interaction between j, p and Te was observed.
NTM (m/n=2/1) was stabilized through qmin increase above 2 during qmin control, and confinement was recovered. Development of current profile control system is important for higher
confinement and stability in advanced scenarios in ITER. Spatially localized off-axis NBCD is possible.
Measured CD location agrees with neutron emission profile. Measured total driven current agrees with the ACCOME calc. CD location in the ACCOME code shifts inward than measurement by
dρ~0.2. Some mechanism is required for the explanation. further study