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CCS Method to Reproduce Tokamak Plasma Shape ( C auchy C ondition S urface). F. Wang* 1 , K. Nakamura 2 , O. Mitarai 3 , K. Kurihara 4 , Y. Kawamata 4 , M. Sueoka 4 , K. N. Sato 2 , H. Zushi 2 , K. Hanada 2 , M. Sakamoto 2 ,
F. Wang*1, K. Nakamura2, O. Mitarai3, K. Kurihara4, Y. Kawamata4,
M. Sueoka4, K. N. Sato2, H. Zushi2, K. Hanada2, M. Sakamoto2,
H. Idei2, M. Hasegawa2, S. Kawasaki2, H. Nakashima2, A. Higashijima2
Prepared and Presented by Wang Feng in ITC-16
Modified and Presented by Kazuo Nakamura in ASIPP
RIAM, Kyushu University
Main parameters of CPD:
1) The CCS method can reproduce plasma shape with high precision corresponding to the number and types of available sensors.
2) The CCS method can identify plasma current with an error of less than 2%.
3) The CCS position and shape are insensitive to reproduction accuracy. This is advantageous in the application to the real-time plasma control.
 K. Kurihara, Nuclear Fusion, Vol.33, No.3 (1993) 399-412.
CCS method was proposed by Dr. Kurihara and tested on JT-60U.
Flux Loops CCS && PF Coils
Magnetic Probes CCS && PF Coils
CCS CCS && PF Coils
1. Various ideal flux surfaces corresponding to different plasma profiles are made by equilibrium code.
2. These plasma shapes are reproduced by using CCS method.
3. The original and reproduced shapes are compared.
R: +0.1 ~ +0.8
Z: -0.7 ~ +0.7
PF Coils: 7
Flux Loops: 45
Mesh Size (RxZ): 140x280
Mesh Precision: 0.005m
Ellipse for CCS
Small radius: 0.03m
Large radius: 0.05m
Reproduction with 45 flux loops
Reproduction with 26 magnetic probes
The CCS method can reproduce plasma shape of spherical tokamak solely with the measurements of flux loops.
In case of much elongated and triangular plasmas in spherical tokamak CPD, good precision can be achieved by changing the degrees of parametric freedom of Cauchy-Condition Surface.
In case of circular plasma shape, normally the shape difference of circular plasma shape is less than 1% compared with major radius R.
X Point difference
Typical plasma shape reproduction
(Ip = 100kA, IPF1=10kA, βp=0.5, li=0.7, κ=2.1)
Difference of X Point
Difference of Plasma Shape
The differences between CCS method and ECODE are compared. In case of large elongated and triangular double-null plasma of CPD, normally the X point difference is less than 2%, and shape difference is less than 3% compared with major radius R.
1. The CCS method can reproduce plasma shape of spherical tokamak in good precision solely with the measurements of flux loops or magnetic sensors.
2. In case of much elongated and triangular plasmas in spherical tokamak, good precision can be achieved by increase in degrees of parametric freedom representing the Cauchy condition.
3. The CCS method can reproduce spherical tokamak plasma shape with good precision in different plasma current profiles (li=0.5 ~ 1.0). In case of large elongated and triangular double-null plasma, normally the X point difference is less than 2%, and shape difference is less than 3%.
In the real plasma discharge experiment, eddy current effect is important, especially at ramp-up stage of plasma current. The effect of eddy current will be taken into account in Cauchy Condition Surface method in future.