Behaviors of Electron Heat Transportation in HT-7 Sawtoothing Plasma
description
Transcript of Behaviors of Electron Heat Transportation in HT-7 Sawtoothing Plasma
HT-7 ASIPP
Behaviors of Electron Heat Transportation
in HT-7 Sawtoothing Plasma Liqun HU, Yi XU, Baonian WAN, Yuejiang SHI Xiangj
un ZENG and HT-7 Team
Institute of Plasma Physics
Chinese Academy of Sciences
Shushanhu Road 350, Hefei 230031, P. R. China
E-mail contact of main author:[email protected]
HT-7 ASIPPIn HT-7 ohmic plasma, main energy loss comes from
electron heat conduction, electron thermal transportation plays a crucial role in determining achieved plasma parameters and their spatial distribution, which is very closely associated with the plasma confinement. Based on the heat pulse propagation originating from the sawtooth activity on the soft x-ray intensity signal, some data processing methods, including average of tens of sawteeth, has been tried to experimentally determine electron heat diffusivity on the HT-7 tokamak. As a result, methods of time to peak and sawteeth averaging have been adopted finally to get stable and reasonable electron heat diffusivity value. Based on preliminary understanding of the measured electron heat diffusivity, performances of different high confinement target plasmas are presented and discussed.
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Experimental apparatus HT-7 Experimental apparatus HT-7 superconducting Tokamaksuperconducting Tokamak
R = 1.22 m, a = 0.27 m
Ip = 100~250 kA
BT = 1~2.5 T
ne = 1~8x1013 cm-3
Te = 1~5 KeV
Ti = 0.2~1.5 KeV
Limiter:
graphite limiter with poloidal and toroidal configuration
ICRF:
f = 15~30MHz, P = 0.3MW
f = 30~110MHz, P = 1.5MW
LHCD:
f = 2.45GHz, P = 1.2MW
Main Goal:
Advanced Steady-state operation and related physics
Vertical array with 37 detectors of SBDs
Horizontal array with 37 detectors of SBDs
Slot-aperture with a movable slider covered with Be foils
Au-Si detector
Au-Si detector
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Soft X-Ray Diagnostic Arrays
High spatial
resolution and
time resolution
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Mathematical description of the heat pulse propagation
General electron-heat-balance equation:
Qr
trTrrrn
rrt
trTrn e
eee
e
]
),()()([
1),()(
2
3
Ignoring all heat sources and sinks, and assuming constant Ne (r) and e (r):
]),(
[1),(
)(2
3~~
r
trTrn
rrt
trTrn eee
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Time-to-peak analysis
Fourier transform:
sensitive to the shape of heat pulse
high and better periodical sawtooth
Dipole Model: e
p
rt
9
2
p
e t
r
9
2
Monopole
Model: ep
rt
8
3 2
p
e t
r
8
3 2
1. Time-to-peak analysis 2. Fourier transform based techniques 3. Time-domain modeling: data fitting by a model
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The dipole model: applied, more ideal and more suitable
for HT-7 than the monopole model for good mathematical
reasons and carrying zero total heat content.
Time-to-peak analysis
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Data Processing Method for determining electron thermal diffusivity e
1. Function fitting
Difficult to find suitable function for the data
2. Superposing of sawteeth heat pulse
Good ratio of signal to noise, but sensitive to the initial point choice of each sawtooth, suitable for platform stage of the discharge.
3. Averaging of sawteeth
Relatively simple, better for widely practical use
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Averaging of tens of sawteeth
pe t
r
8
3 2
mttt jro
m
j
jripi /)(
1
ri
tPi
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1. Asymmetry of the spatial electron heat transport
Ip=200kA, BT=2.0T, ne=1.51019 m-3, PLHW=400kW, PIBW=230kW
Preliminary analyses of HT-7 electron heat transport
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Improvement of heat transport in LHCD plasma
Ip=220kA, BT=2.0T, ne=1.51019m-3, PLHW=260kW, f=2.45GHz
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Dependence of electron heat transport on LHW power
Ip=125kA,BT=1.8T,ne=1.51019m-3
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Dependence of electron heat transport on IBW power
Ip=150kA, BT=1.9T, ne=1.51019m-3, f=30MHz
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Dependence of electron heat transport on density in the synergy of LHW+IBW heated plasma
Ip=200kA,BT=1.8T, PIBW=230kW(27MHz),PLHW=540kW
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Dependence of electron heat transport on density in the synergy of LHW+IBW heated plasma
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Ip=200kA,It=1.95T,ne=1.71019m-
3,PIBW=230kW
Dependence of electron heat transport on LHW power in the synergy of LHW+IBW heated plasma
HT-7 ASIPPDiscussion
Dependence of RF power on electron heat transport
HT-7 ASIPPDiscussion
Dependence of RF power on electron heat transport in the synergy of LHW +IBW
Preliminary analyses on HT-7 electron heat transport indicates:• Asymmetry of the spatial electron heat transport• LHW can not only drive plasma current and plasma
temperature, but also improve plasma particle confinement and electron heat transport. As increase of the LHW power, electron heat transport decreases apparently.
• In IBW heated plasma, the electron electron heat transport decreases obviously as the IBW power increase after the IBW power launched over a power threshold.
• In the synergy of LHW and IBW plasma, the electron heat transport improves as the density increase, however, over a certain value, deteriorate as the power increase.
• More deep and systematic analyses will be done to find detailed relations among the electron heat transport and plasma parameters.
Summary
HT-7 ASIPP