7th Asia-Pacific Conference on Plasma Physics, 12-17 Nov, 2023 at Port Messe Nagoya

Validation of the plasma equilibrium configuration designed by FEEQS in theHL-2M experiment
Y.Y. Zhong 1, L. Xue 1, W.L. Zhong1, J.X. Li1, X. Song1, Z. Yan1, H. Heumann2
1Southwestern Institute of Physics, China,
2
Université Côte d'Azur, Inria, CNRS , Francee-mail (speaker): Zhongyuanyun@swip.ac.cn

Plasma equilibrium is essential for tokamak
engineering design and physical research. It has beenfrequently applied for scenario development, MHD
instability analysis, plasma control, etc. HL-2M[1] is a
new copper-conductor tokamak device built at theSouthwestern Institute of Physics (SWIP), and recently
achieved plasma current of 1 MA. Owing to the poloidal
field (PF) coils inside the toroidal field coils, it is easy toflexibly control the plasma equilibrium configuration.
One of its important missions is to develop theconfiguration
researchforvarious
divertor
configurations. This paper presents that simulation
results of the free-boundary equilibrium code FEEQS[2,3] ,has been successfully used to design the HL-2M limiterand divertor configurations. The design has beenvalidated in the recent experiments. The study provides asignificant equilibrium analysis and benchmark method,
accumulating relevant technology experiences toward
IMAS[4].
FEEQS solves the free-boundary equilibrium equation,
based on the Finite Element Method with triangularmesh and applies piecewise linear shape functions toapproximate the magnetic flux. The direct static mode inFEEQS solves the equilibrium problem by given PF coilcurrents. For the evolution problem, it couples theplasma equilibrium and circuit equations in atime-dependent way and results in plasma boundaries,
plasma profiles of toroidal current density, and safety
factor in an offline way.
We designed a few configurations by direct static
mode and made benchmark with EFIT code. In addition
several shots by direct evolution have been validatedwith the HL-2M experiments in the flat-top phase withlimiter and conventional divertor configurations. The(a)fundamental parameters of these limiter shots are
R=1.78m, a = 0.65m, IP = 0.6MA and k = 1.2-1.4. It hasbeen demonstrating that(i)with static mode, the EFIT plasma boundary is wellmatched during the benchmark, as shown in Figure 1(a),FFEQS is capable of designing various shapeconfigurations.
(ii)With evolution mode, Figure 1(b) shows that thecurrent evolution of central solenoid (CS) coils andpoloidal coil (PF) simulated by FEEQS fit theexperimental data well. The plasma boundary evolutionof FEEQS can match the image of the fast camera and
EFIT’s reconstruction. The trend consistency of a and R
is fairly well. According to all the simulated shots, therelative error on a is less than 3%, and the case for R is
no more than 1.7%. Nevertheless, it could be concluded
that the FEEQS simulation on shape configuration andcoil currents are reliable.
These works and validations would be helpful inproviding reference to the next engineering testing andphysical study. More details will be presented in thisconference.
Reference[1]. X.R. Duan et al 2022 Nucl. Fusion 62 042020[2]. Heumann H. et al 2015 Quasistatic free-boundary
equilibrium of toroidal plasma with CEDRES++:
computational methods and applications J. Plasma
Phys. 81 905810301[3]. Xiao Song. Model-based control-oriented scenario
construction in tokamaks. Automatic ControlEngineering. COMUE Université Côte d'Azur(2015 - 2019), 2019. English. ⟨NNT :2019AZUR4089⟩.
[4]. F. Imbeaux et al 2015 Nucl. Fusion 55 123006