The Divertor Configuration in Experiments’03 on HL-2A Tokamak *

The Divertor Configuration inExperiments’03 on HL-2A Tokamak*

Li Qiang(李强 ), Mao Suying(毛苏英 ), Luo Cuiwen(罗萃文 ), Pan Li(潘莉 ), Zhang Jinhua(张锦华 ), Yang Qingwei(杨青巍 ),Song Xianming(宋显明 ),HL-2A team

Southwestern Institute of Physics

P. O. Box 432, Chengdu, 610041, China

*Partly supported by the National Natural Science Foundation of China(No. 10175022)

Outline1. Basic background

2. The progress of plasma LCFS determination on HL-2A

3. Boundary identification verification

4. Boundary features in LPDs on HL-2A in the first experiment campaign

5. Conclusion and discussion

Workshop on Plasma Theory and Simulation(PST), Sep. 13-15, 2004, SWIP, Chengdu, China

LI Qiang, et al, Configuration xperiment’03 on HL-2A核工业西南物理研究院Southwestern Institute of Physics

1. Basic background

• Plasma boundary(PB) is a key issue of advanced tokamaks(AT);

• PB is one of the most basic tasks for HL-2A;

• PB identification is a tough nut to crack;

• HL-2A paid enough carefulness on the application and citation of the results;

• Enough special seminars for verification and qualification of the results have been held in SWIP;

• The understanding and the code are progressing in HL-2A;

• PB is a relative of equilibrium to be stressed in this talk.

Main references about the contents in this pageLI Qiang, et al., Plasma Science&Technology, 2004,Vol.6 No.3, p2313LI Qiang, et al., 5th Japan-China workshop, Jaeri, Feb 2-4, JapanSee also other papers concerning Plasma Boundary Identification in Annual Reports of SWIP





MotivationThe PB should be verified;

It is the first but indispensablestep for the understandings of adivertor tokamak.

The equilibrium feature should beknown;

The equilibrium parameters are necessary for the model establishment of further control tasks on HL-2A, e.g., statistical database method, dynamic controls, etc.

Especially LPDs are of importance for plasma discharge control;

The quantitative equilibrium parameters are useful for benchmarks on the codes.

HL-2A operational parameters

R=1.64m

a<0.4m

1.4T168kA0.92s

2.2T300kA1.5s

2.8T450kA4.5s

BtIpPulse length

rated 2003 2004

2 The progress of plasma LCFS determination on HL-2A

• A boundary identification code was transferred from JT-60U

• Major revisions on the code transferred;

• Tentative application on this code;

• Verification on this code;

• Accepted by most people, then the code is named B2F2(Boundary identification By Filament Fitting)

• Many other methods kept or are coming forth to verify each other;

• The code transferred keeps being modified for further applications.



3 Boundary identification verification

•The code should be benchmarked before it is used;•Boundary is the LCFS which can’t be directly measure;•The measurements, i.e., CCD photos, light intensity, etc, can only give qualitative information of boundary;•Though the potentials given by ESPs can give some quantitative message, but the behaviors of particles in the SOL is still unclear;However, the results from the code is quantitatively checked with a set of data given by an equilibrium code

Theoreticalverification



Comparison between 2 sets of results from SWEQU and B2F2

Conditions assumed in SWEQU: Ip=100kA, Imp1=-Imp2=Imp3=Iv =7kA, Irf=4kA

Rp(m) ap(m) Ri(m) Ro(m) Z(m) (aver) (up) (down)x-point(Xr,Xz)

SWEQU1.63 .38 1.251 2.011 .04 1.039 .108 .042 .173 (1.546,-.478)

B2F2 1.63 .379 1.25 2.009 .039 1.031 .095 .013 .177 (1.547,-.473)

Remarks on the comparison•Actual measurement situation, LPD with Ip about 100kA, actual operational situation are taken into account; •Enough good consistency is obtained;•They uncertainty is possibly caused by the number of probes, calculation error, etc.CONCLUSION: B2F2 is able to give a precise result if signals are precise enough.



4 Boundary features in LPDs on HL-2A in the first experiment campaign

A typical LPD limiter dischargeIp=118kA





A normal divertor discharge



A discharge with Ip>100kA(SHOT01651)



CCD photos of Shot01651

Configuration features

t=160ms





It’s clear that the plasma geometric center is well controlled by Iv. Even when Iv is large enough, the horizontal location of x-point is fixed.

Horizontal configuration parameters in bulk plasma vs Iv in Shot01651



It can be seenthe plasma vertical displacement ΔZ is well confined by Irf while the vertical location of x-point is determined by the Imp2;Imp2 can’t control ΔZ and Irf can’t control Xz;Though Imp2=-Imp1=-Imp2, Xr can’t be changed by Imp2(the figure in previous page).

Vertical configuration parameters in bulk plasma vs Imp2 and Irf in Shot01651

5 Conclusion and discussion• The divertor configuration has been achieved and identified on HL-2A;

• There are some distinct features for LPDs on HL-2A, e.g., actually unchangeable elongation;

• The machine exhibits controllability, due to simple function for the EPF coils in the cost of changeability of the shape.

Then location of x-point doesn’t need to be controlled;

Positions of plasma can be easily controlled by Iv and Irf respectively;

The unused EPS coils, e.g., MP coils are useful for configuration optimization.

• With the optimization on the feeding EPF currents, the elongation about 1.3 can be achieved;

• With local driving, e.g., LHCD to be probably conducted in 2004, higher elongation about 1.4 can be expected;

• Higher values of elongation are still impossible, unless the machine is modified;

• The modification are doing. Primary engineering design has been done then the equilibrium and physical ones.



谢谢 !Thanks!



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The Divertor Configuration in Experiments’03 on HL-2A Tokamak *