Presented by Masao Ishikawa (JAEA)
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Transcript of Presented by Masao Ishikawa (JAEA)
Confinement Degradation of Energetic Ions due to Alfvén Eigenmodes in JT-60U Negative-Ion
-Based Neutral Beam Injection Plasmas
M. Ishikawa, M. Takechi , K. Shinohara, G. Matsunaga, Y. Kusama, V.A. Krasilnikov1, Yu. Kashuck1, M. Isobe2, T. Nishitani, A. Morioka, M. Sasao3, M. Baba3, JT-60 team
JAEA (Japan), 1 TRINITI (Russia), 2 NIFS (Japan), 3 Tohoku Univ. (Japan)
Presented by Masao Ishikawa (JAEA)
21th IAEA FEC‘06.10.16th ~ 21th, Chengdu, China
E X / 6 - 2
- Introduction
• Background
• Previous results (large h) and issues of Alfvén eigenemodes study in JT-60U
- Alfvén eigenmodes experiments in weak shear plasmas
• Alfvén eigenmodes in weak shear plasma (moderate h)
• Investigation of confinement degradation of energetic ions
- Summary
Table of Contents
Burning plasmas are self-sustained by alpha-particle heating
AEs induce the enhanced transport of alpha-particles from the core region
- A performance of a burning plasma could be degraded
- First walls could be damaged by lost alpha-particles
Understanding of the alpha particle transport in the presence of AEs is the important research issues for ITER
However, a high alpha particle pressure gradient could destabilize Alfvén eigenmodes (AEs)
TAEモードの励起
高速α 粒子
ねじれアルヴェン波
核融合プラズマ 高速α 粒子の損失
Burning plasma Loss of α-particle
Excitation of AE
Fast α-particle
Shear Alfvén wave
Background
In weak shear plasma with large h
• Bursting AEs called Abrupt Large amplitude Events (ALEs)
In JT-60U, AE experiments have been performed utilizing Co-injected Negative-ion-based Neutral Beam (NNB)
(ENNB : 340 ~ 400keV, PNNB :3 ~ 5MW) in several kinds of magnetic shear plasma under combination with PNBs
JT-60U
Previous results and issuesof AE studies in JT-60U
time scale : < msamplitude : large
In weak shear plasma with moderate h
time scale : 100ms ~ 1 samplitude : moderate
Investigation energetic ion behavior
ALE
(h : energetic ion beta)
We did not investigate energetic ion behavior
redistribution of energetic ions due to resonant interaction with AEs M. Ishikawa, 20th. IAEA FEC in Portugal
New simulation resultG. Vlad, TH/P6-4 Fri, (this Conf.)
To investigate energetic ion behavior in the presence of AEs
Diagnostics for investigationof energetic ion transport
Neutron ProfileMonitor
Energy distribution of neutral particles has information on energy distribution of energetic ions
JT-60U
T-NBI
N-NBI
P-NBI
P-NBI
P-NBI
P-NBI
P-NBI
T-NBIP-1
P-9P-10
P-13
P-14
P-16P-17 P-18
P-8
P-7
P-5
P-4
P-2
Neutral ParticleAnalyzer (NDD)
Neutron emission profile measurement
CX neutral particle measurement
radial profile energy distribution
Beam -Thermal neutron is dominant component of the total neutron rate
0
0.2
0.4
0.6
0.8
5 5.5 6 6.5 7 7.5 8
am
plit
ud
e (
a.u
.)
time (s)
1
1.5
2
qm
in
100
20
40
60
80
Fre
qu
en
cy
(k
Hz)
0
24
PN
NB (
MW
)AEs in Weak Shear Plasma (moderate h)
E46078 1.0MA/1.7T, ENNB~390 (keV) n =1 modes with up-frequency sweeping are observed and its frequency saturates.
(A) (B)
(A)
(B)
Energetic ion confinement with AE can be investigated by compared with that in the later NNB injection phase
Only weak AEs are observed
RSAE is global AEs localized near the zero magnetic shear region.
weak AEs
0
0.1
0.2
0.3
0.4
0.5
0.6
0 0.2 0.4 0.6 0.8 1
w/w
A
r/a
qmn~ 1.5
transition
(2)2 > qmn > 1.5
0
0.1
0.2
0.3
0.4
0.5
0.6
0 0.2 0.4 0.6 0.8 1
w/w
A
r/a
RSAE
(1)
0
0.1
0.2
0.3
0.4
0.5
0.6
0 0.2 0.4 0.6 0.8 1
w/w
A
r/a
qmn< 1.5
qmn= 1.4
TAE
(3)
0
0.1
0.2
0.3
0.4
0.5
0.6
0 0.2 0.4 0.6 0.8 1
w/w
A
r/a
qmn= 1.2(4)
(1) (2) (3)
(4) 0
1
2
3
4
0 0.2 0.4 0.6 0.8 1
(%)
r/a
classical b
Confinement degradation of energetic ions due to n = 1 AEs
E46078 1.0MA/1.7T To investigate energetic ion confinement, the total neutron rate (Sn) is calculated with the OFMC code
• Confinement of energetic ions is classical(B)(A)
02.5
5
(MW
)
PN
NB
100
20
40
60
80
Fre
qu
en
cy
(k
Hz)
0
0.4
0.8
am
plit
ud
e(a
. u.)
0
0.5
1
1.5
2
2.5
3
3.5
5 5.5 6 6.5 7 7.5 8
rate
(1
015
n/s
)N
eu
tro
n e
mis
sio
n measurement
time (s)
00.05
0.10.15
0.20.25
5 5.5 6 6.5 7 7.5 8
S
n/S
n
time (s)
calculation Sn
Energetic ion transport ?0
0.05
0.1
0.15
0.2
0.25
0.3
0 0.2 0.4 0.6 0.8 1
red
uct
ion
rat
e
amplitude (a.u.)
Reduction rate in Sn increases when mode amplitude increases
Sn
/Sn
(B) with only weak AEs
(A) with clear AEsMeasured Sn is smaller than calculated one
Time evolution of measured Sn agrees with calculated Sn
~ Classical confinement
Confinement degradationSn/Sn ~ 25 %
0
2
4
6
8
10 MeasurementTOPICS
(101
3 m
-2s-1
)N
eutr
on fl
ux
0.40.60.8
11.21.41.61.8
2
0 0.2 0.4 0.6 0.8 1Mea
s./T
OP
ICS
r/a0.40.60.8
11.21.41.61.8
2
0 0.2 0.4 0.6 0.8 1Mea
s./T
OP
ICS
r/a
02468
101214 Measurement
TOPICS
(101
3 m
-2s-1
)N
eutr
on fl
ux
(A) with AEs (t=6.4s) (B) with weak AEs (t=7.8s)
0
2
4
6
8
10
5 5.5 6 6.5 7 7.5 8ne
utr
on
co
un
ts (
10
13 m
-2s
-1)
time (s)
-- r/a ~ 0.19 -- r/a ~ 0.32 -- r/a ~ 0.46 -- r/a ~ 0.56 -- r/a ~ 0.73 -- r/a ~ 0.84
NNB NNB
20
40
60
80
100
Fre
qu
ency
(kH
z)
Energetic ion transport from the core region due to AEs
Calculated line integrated neutron profile with a transport code (TOPICS) is compared with the measurement.
(A) (B)
Plasma configuration and sight lines
Energetic ion transport from the core region of the plasma
To investigate energetic ion transport, neutron emission profile was measured
0.4
0.5
0.6
0.7
0.8
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
t = 5.9s
Me
as.
/TO
PIC
S
r/a
t = 6.1s
0
2
4
6
8
10
5 5.5 6 6.5 7 7.5 8ne
utr
on
co
un
ts (
10
13 m
-2s
-1)
time (s)
-- r/a ~ 0.19 -- r/a ~ 0.32 -- r/a ~ 0.46 -- r/a ~ 0.56 -- r/a ~ 0.73 -- r/a ~ 0.84
NNB NNB
20
40
60
80
100
Fre
qu
ency
(kH
z)
The second channel signal increases rapidly
Local transport of energetic ions in the center region
qmin and q = 1.5 surface (TAE gap) both lie around r/a < 0.3
The innermost channel signal does not increase
Local transport of energetic ionsin the transition phase
In transition phase,
qmin=1.5
Resonant energy range => 140 ~ 280 keV
10
100
1000 with AEs (t=5.9 - 6.2s)
w/o AEs (t=7.4 - 7.7s)
Cou
nts
(a.u
.)
ENNB
(a)
0
0.2
0.4
0.6
0.8
1
0 50 100 150 200 250 300 350 400
F/F
energy (keV)
(b)
Neutral particle fluxes in limited energy range (50 ~ 300 keV) are enhanced.
Peak fraction of enhanced neutral particle flux is ~ 200 keV.
[ Resonance condition with the mode ]
N= (f / fc) q - nq + m = integer f = mode frequency (60 - 70 kHz) q = safety factor ( 1.4 - 1.6) n, m = toroidal, poloidal mode number Fc = troidal transition frequency of energetic ions
( R. B. White et.al. Phys. Fluids 26 (1983) 2958 )
Fre
qu
enc
y (k
Hz) 100
50
0
5.5 6.0 7.06.55.0 8.06.5time (s)
Changes in the energy distribution suggest the resonant interaction between energetic ions and modes
Resonant interaction with AEs and eneregetic ions
summary
Confinement degradation of energetic ions are quantitatively observed.
Changes in neutral particle flux suggest the resonant interaction between energetic ions and modes.
• total neutron emission rate• neutron emission profile• charge exchange neutral particle flux
Neutron emission profile measurements indicate energetic ion transport from core region to outer region and local transport in the core region in the transition phase.
( time scale : 100ms ~ 1s, amplitude : moderate )
in weak shear plasma with moderate h
• AEs with frequency sweeping
Energetic ion behavior is investigated with
0
1
2
3
4total neutron
Neu
tron
rat
e(1
015 s
-1)
0
1
2
3 neutral particleflux E>20 keV
4 4.5 5 5.5 6 6.5 7
Neu
tral
par
ticle
flux
(104
s-1
)
Time (s)
Fre
quen
cy (
kHz)
180
100
120
140
160
N N B
Change in neutral particle flux suggests energetic ion transport from core to outer region
Neutral particle flux change after neutron emission rate changed Time lag (t) ~ 100 ms time scale of transport and /or slowing downEnergetic ions are neutralized through
charge exchange reactions with D0 or C5+ in outer region of the plasma
t
energetic ion transport from core region to outer region
1.5
2
2.5
3
3.5
5400 5500 5600 5700 5800 5900 6000
(b) 20 - 100 keV
1.5
2
2.5(a) 100 - 500 keV
Neu
tral
par
ticle
flux
(a.
u.)
~ 50 ms
time (ms)