ht-7 asipp density modulation experiment within lithium coating on ht-7 tokamak wei liao,yinxian...
TRANSCRIPT
HT-7
ASIPP
Density Modulation Experiment within
Lithium coating on HT-7 Tokamak
Wei Liao ,Yinxian Jie, Xiang Gao and the HT-7 team
Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, China
2011.7.19
HT-7tokamak 2011 data meeting and workshop 1
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ASIPP
Introduction
Experimental Set-Up
Density Modulation Experiment
– Modification principle and the major diagnostics
– The calculation of transport coefficients: diffusion
coefficient (D) and convection velocity (V) Conclusion and Discussion
Outline
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Introduction
For magnetically confined plasmas, the study of the particle transport coefficients is a significant and perplexed issue in this field. Density modulation is a powerful approaching to solve the experiment difficulties.
For further particle transport research , this new density measurement is under the full metallic wall condition and lithium limiter applying.
Prompted lithium coating3
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Introduction
According the modulation principle, we can obtain the results which conclude particle transport coefficients under new conditions this year.
The most significant things is to make a comparison between the results this year and the ones under carbon wall and carbon limiter conditions in 2004
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ASIPP
Introduction
Experimental Set-Up
Density Modulation Experiment
– Modification principle and the major diagnostics
parameters
– The calculation of transport coefficients: diffusion
coefficient (D) and convection velocity (V) Conclusion and Discussion
Outline
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ASIPP
Experimental Set-up
Rebuilt from the original Russian T-7 tokamak in 1994, the HT-7 superconducting tokamak has a major radius of R=1.22m and a minor radius of a =0.27m in the circular cross-section.
Basically, the HT-7 tokamak with the limiter configuration is normally operated under the basic parameters: Ip=100-250kA, the toroidal magnetic field Bt=2T, the central line-averaged plasma density ,central electron temperature Te=0.5-3.0keV and central ion temperature Ti =0.2-1.5keV.
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Experimental Set-up
We may see that the main limiter stuffing equipment below:
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Introduction
Experimental Set-Up
Density Modulation Experiment
– Modification principle and the major diagnostics
– The calculation of transport coefficients: diffusion
coefficient (D) and convection velocity (V) Conclusion and Discussion
Outline
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ASIPP
Density modulation experiment
The principle of density modulation:
The particle balance equation is shown as follows,
1 (1),
nS r S
t r r
(2) nD Vnr
where n, Γ, S, D and V are electron density, particle flux, particle source rate, particle diffusion coefficient and convection velocity, respectively. Here, we assume the equilibrium and modulated components are independent, and separate these two components as follows,
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Density modulation experiment
Then, the following particle balance equations for modulated components are obtained from eq.(1)
(3) ~
SS ,~
,~eq Snnn eqeq
(4) ~~ ,~~ , ~~
nitnenneSS titi
(5) 0~
~~1~11~2
2
D
Sn
Din
r
V
DrD
V
r
n
D
V
r
D
Drr
n
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ASIPP
Density modulation experiment
Convection velocity is assumed to be zero at plasma center and increase proportionally to minor radius. This is expressed by the following equation.
V(r) = (r/a)V0
The value of D and V0 are scanned. For each D and V0 are calculated. Then, the difference between the experiment and calculated values is calculated to minimize as the following equation:
chord
IcalcIRcalcxp NLNLNLNL 2
exp
2
Re
2 )()(
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Density modulation experiment
The major diagnostics and FIR detector:
Schematic of optical arrangement of Multi-channel interferometer
Waveguide Detector sensitivity ~100mV/mW
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IP=130kA, Bt=3800A, density measured by FIR interferometer system
Low density --1.5x1019 m-3 High density --2.2x1019 m-3
Density modulation experiment
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The estimation of particle source by IDL program
Density modulation experiment
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ASIPP
Density modulation experiment
The calculation of transport coefficients: diffusion coefficient (D) and convection velocity (V) (two shots: under different density)
Low density - shot 112671 High density - shot 11283815
HT-7
ASIPP
Density modulation experiment
The calculation of transport coefficients: diffusion coefficient (D) and convection velocity (V) (two shots: under different density)
Shot <ne> ( x1019 m-3)
D (m2/sec) V0 (m/sec)
112671 1.5 0.47 -2.5
112838 2.2 0.21 -3.6
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ASIPP
Introduction
Experimental Set-Up
Density Modulation Experiment
– Modification principle and the major diagnostics
– The calculation of transport coefficients: diffusion
coefficient (D) and convection velocity (V) Conclusion and Discussion
Outline
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ASIPP
Conclusion and Discussion
The Comparison
shot <ne>(x1019 m-3) D (m2/sec) V0 (m/sec)
67938 1.5 0.42 4.7
67941 2.2 0.28 -0.4
shot <ne>(x1019 m-3) D (m2/sec) V0 (m/sec)
112671 1.5 0.47 - 2.5
112838 2.2 0.21 -3.6
Experiment results without lithium coating in 2004
Experiment results with lithium coating in 2011
Point 1Point
1
Point 2
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Conclusion and Discussion
The Discussion
when the background plasma density is 1.5x1019 m-3, the V in 2004 is positive ,but in the same background density the experiments operate under lithium coating circumstances in 2011, the V is negative, implying the desirable and expecting pinch effect
Of equal importance, we can tell the evident difference between the data V in 2004 and the data V in 2011 in higher density case (<ne> = 2.2x1019 m-3), since the absolute value of the later one is much larger than that of the former, inferring that the new experiments under lithium coating condition bring a better particle constraint.
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Conclusion and Discussion
The Future work
the root reason why coating changes makes the significant difference deserves the further investigation and research.
more experiments with different modulation frequency, wall material and limiter will help us to get more sufficiently and effectively experiment data and to get more precise analysis
this technique is expected for the analysis of LHW and IBW heating in the future experiments on EAST tokamak.
Acknowledgement : This work was funded by the National Nature Science Foundation of China with contract NO.11075179.
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Thank you !