ecrh/eccd system and experimental results in...
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KOREA-JAPAN workshop on physics of wave heating and current driveOct. 24, 2005 in Pohang,
ECRH/ECCD system and experimental results in LHD
T.Notake, S.Kubo, T.Shimozuma, Y.Yoshimura, H.Igami, Y.Takita,S.Kobayashi, S.Ito, Y.Mizuno, T.Mutoh and LHD Team
National Institute for Fusion Science
1. ECRH/ECCD system in LHD・ Gyrotron and transmission lines・ Transmission Efficiency ・ Controllability of beam-focusing/steering・ Controllability of beam-polarizations
2. Experimental results・ Formation of electron internal transport barrier
Bird eye’s view of the system
• 9 gyrotrons, 8 set of transmission lines and antennas are equipped.• 4-168GHz CPD (Toshiba), 2-84GHz CPD (Gycom), 2-82.7GHz non-CPD (Gycom),
1-84GHz CW-CPD (Gycom) → Operated 65min at the power of 160kW(MOU-out)
• 2-evacuated 1.25inch and 6-aired 3.5 inch corrugated waveguides system.• Total lengths of each transmission lines are about 100m .
2-1.25inch
Transmission Efficiency
• Loss in MOU of 168GHz-system are higher than that of 84GHz-system.-Due to the sensitivity of the alignment?
• Losses in WGs of evacuated 1.25 inch lines are higher than that of 3.5 inch aired-lines.
-Due to the low purity of the coupled HE11-mode?
• Further optimizations are needed.• Total injection power into LHD
reached 2.1MW.
S.Kubo,et al., PPCF 47 (2005)
0
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#1 #2 #3 #7 #4 #5 #11 #12
loss in MOU (168GHz)loss in trans. (168GHz)injection to LHD (168GHz)
loss in MOU (82.7 & 84GHz)loss in trans. (82.7 & 84GHz)injection to LHD (82.7 & 84GHz)
effic
ienc
y [%
]
168GHz 84GHz 82.7GHz
1 68GHz Beam
SteeringMirror
FocusingMirror
from Waveguides
84GHz Beam
SteeringMirror
FocusingMirror
radial
toroidal
From waveguide
168GHzbeam
82.7GHzbeam
steeringFocusing
Antenna system (at vertically elongated cross section)
• Beam focusing/steering are important for local ECRH/ECCD• 4-upper port antennas and 2-lower port antennas are installed.• Injection beam is focused by Quasi-Optical mirrors and steered to
toridal/radial directions by final plane-mirror.
2-lower antennas
4-upper antennas
Hot test results of beam steering/focusing
• Errors of steering for tor/rad-directions notably affect deposition profile• Beam steering/focusing were checked in vacuum vessel of LHD by using
kapton film and IR-camera.
Power deposition profiles
S.Kubo,et al., J.Plasma.Fusion.Res.SERIES 5 (2002)
• Experimental power deposition The boxcar analysis is used to deduce the power deposition profile.We uses plus/minus 3ms data points at turn-on/off timings to avoid effect of diffusion.
• Depositon profile is almost consistent with ray-tracing results.
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1
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Pabs
[a.u
.] Ray-Tracing
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40
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120
0 0.2 0.4 0.6 0.8 1
3.55m3.53m3.45m3.40m
Pdep
[MW
/m3 ]
ρ
deduced from MECH
82.7GHz
Controllability of wave polarization
• Polarization of incident wave is essential parameter in order to couple it to the desired mode in the plasma.
• Two-polarizers with different grating parameters are used to form arbitrary polarization states
T.Notake, et al., Rev.of Sci.Instruments 76 (2005)
-45
-30
-15
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-45 -30 -15 0 15 30 45
βmea
sure
d [d
eg]
βset [deg]
β-scan(α=-45o)Polarization monitor was developed. -Two linear components are sampled independently at the miter-bend via coupling holes opened reflecting-plates.-Amplitude ratio and phase differences of them are deduced by QPSK method.
polarization monitor
-90
-60
-30
0
30
60
90
-90 -60 -30 0 30 60 90
αm
easu
red[
deg]
αset[deg]
α−scan(β=0o)
Definition of polarization
50
100
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200
0.2
0.4
0.6
0.8
1Pabs
ΔTe
Abs
orbe
d Po
wer
[kW
] Increment of Te [keV]
α [deg]0
0.2
0.4
0.6
0.8
1
-90 -60 -30 0 30 60 90
O-m
ode
purit
y
Plasma response to incident polarization• Incident wave polarization for ECRH were optimized experimentally.• Heating efficiency and increment of Te were clearly changed for polarizations.• Experimental results are well explained using the developed model for the
O/X-mode excitation at the LCFS.
β−dep.
T.Notake, et al., PPCF 47
50
100
150
200
250
0.5
1
1.5
Pabs
ΔTe
Abs
orbe
d Po
wer
[kW
] Increment of Te [keV]
β [deg]0
0.2
0.4
0.6
0.8
1
-45 -30 -15 0 15 30 45
O-m
ode
purit
y
Formation of electron internal transport barrier
• High electron temperature plasmas with steep gradient (eITB) are formed by centrally localized intense ECRH.
• The formation of the eITB has a distinct ECRH power threshold. • The threshold power increases with electron-density.
T.Shimozuma, et al., PPCF 45 (2003)
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2.8 3.2 3.6 4
T e [keV
]
R [m]
177kW
282kW
#28143#28146
width0
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0 200 400 600
T e0 [k
eV]
wid
th [r
ho]
ECH Power [kW]
ne=0.3 x 1019m-3
ne=0.5 x 1019m-3
0.5
0
Evaluation of thermal diffusivity
• Transport analysis by using PROCTR-code was performed for previous two cases.
• once increase within rho~0.45 due to the ECRH injection, But when the eITB was formed by additional 282kW ECRH injection, it decreased drastically.
• The formation of strong positive-radial electric fields are predicted from the neoclassical theory within rho~0.45 for eITB plasma.
T.Shimozuma, et al., PPCF 45 (2003)
eχ
0
4
8
12
0 0.2 0.4 0.6 0.8 1
E rneo [k
V/m
]
ρ
20
-200
1 root3 roots
PECH
=282kW
χ eneo [m
2 /s]
Er0
4
8
12
χ eexp [m
2 /s]
177kW
282kW
02468
01234
T e [keV
]
p ECH [W
/cm
3 ]
282kW
177kW
#28143, 28146
Summary
• High power test was carried out in order to confirm and optimize antenna steering, beams focusing and polarization controls. High precision controls of them become possible.
As a results of the system optimization,
• Well localized and controlled power deposition profiles are experimentally demonstrated.
• Incident wave polarizations are optimized for effective ECRH.
• High-Te plasmas with steep Te-gradient are formed by centrally focused intense ECRH. The thermal diffusivity in the core region would be reduced due to the transition of radial electric field.
정청 감사합니다
Other experiments
• Electron cyclotron current drive
• Electron Bernstein wave heating (slowX-B coupling)
• 3rd X-mode Heating
• Density pumpout
• Control of radial electric field
• Synergy effect (ECRH+ICRF)
• Steady state experiment using CW gyrotron