Plasma Physics and Fusion Science by Virtual-Reality System
Hiroaki Ohtani1,2 , Yasuhiro Suzuki1,2 , Akira Kageyama3 , Ryutaro Kanno1,2 , Seiji Ishiguro1,2 , Mamoru Shoji1 , andYuichi Tamura4
121

Department of Helical Plasma Research, National Institute for Fusion Science, Japan
Department of Fusion Science, The Graduate University for Advanced Studies (SOKENDAI), Japan
3
Graduate School of System Informatics, Kobe University, Japan
4
Faculty of Intelligence and Informatics, Konan University, Japan

Introduction

Scientiﬁc visualization analysis by virtual-reality (VR)technology has a clear advantage compared with an analysis on a two-dimensional display because the technology
can immerse a researcher totally in the VR space. NationalInstitute for Fusion Science (NIFS) introduced a CAVEtype VR system[1] in 1997 to analyze simulation results,
such as magnetohydrodynamics (MHD) simulation resultsfor MHD dynamo and spherical tokamak, molecular dynamics simulation results for chemical sputtering of plasma
particle on a diverter, and particle simulation for magnetic
reconnection.
In the analysis of the magnetic reconnection, we clearlydisplayed the relationship between the complex threedimensional (3D) structures of magnetic ﬁelds, ﬂow velocity of ion, distribution of ion temperature and ion trajectories in the VR space[2].
Recently, we succeeded to visualize integrally a simulation result and experimental device data, and analyzed
equilibrium plasma in the Large Helical Device (LHD) ofNIFS [3, 4]. In this paper, we report one of the recent applications of VR technology to investigate plasma physics
and fusion science in NIFS.
2Visualization of Equilibrium Plasma in Experimental Device

Equilibrium plasma in LHD is calculated by the MHD
simulation code HINT[5], in which each coil is assumed
to be a ﬁlament outside the computation box. The visualization software Virtual-LHD visualizes an isosurfaceof plasma pressure, a streamline of magnetic-ﬁeld, andan orbit of drift particle of an LHD plasma in the VRspace[6]. By visualizing this equilibrium LHD plasma simulation data integrally in the experimental vessel, in which
the devices, such as divertor plates, ion and electron cyclotron heating antennae, are located in the same positions
as those in the actual vessel according to CAD data[3, 4], it
is possible to trace the magnetic-ﬁeld line and particle trajectory to examine whether they strike against the wall ordivertor plate, and to check the plasma pressure isosurface
to check an interference with the wall or antennae.
The integrated VR visualization is realized by EasyVRand FusionSDK, which can capture OpenGL graphic data
created by diﬀerent visualization software and fuse together the data into one graphic data in one VR space[7, 8].
In the previous paper[9], we visualized an LHD equilibrium simulation data by HINT2[10, 11], in which thecoil currents existed in the computation region, and it

became much easier to use the code in practical applications for evaluation of the equilibrium of actual nonaxisymmetric conﬁgurations. In order to check the visualization of HINT2 data, we excluded the divertor region.
In this paper, we succeed to visualize the HINT2 simulation data including the divertor region, and show someresults in the next section.
3

Analysis of Equilibrium Plasma in Experimental Device

Figure 1 is a scientiﬁc visualization of a HINT2 plasma
simulation result by Virtual LHD in the VR space. Greenline shows the stream line of magnetic-ﬁeld. The starting
point is given by Wand in the 3D space. We can visualize
various ﬁeld lines. The black plates are the divertor plates.
Top and bottom panel in Fig. 1 shows the same magneticﬁeld line from the diﬀerent view point. In this way, wecan trace it in the immersive 3D VR space. Since thisHINT2 data includes the divertor region, it is possible toanalyze the magnetic structure there. It is found that thestreamline strikes the divertor plate in the top panel ofFig. 1, and that another end of the line also strikes thewall as shown in the bottom panel.
Figure 2 shows the other magnetic structure. Since theHINT2 code can treat consistently the net toroidal current eﬀects (Ohmic and Neoclassical) and the full torus
conﬁguration with the coil currents in the computation region, the stochastic magnetic structure can be displayed in
the periphery region. The structure is complex as shown inFig. 2. However, this structure cannot be clearly-identiﬁed
as the stochastic. The Poincare map is one of the available
tools, and we will add a function of drawing the map inthe VR space.
Figure 3 displays the drift particle trajectory in the divertor region. We can put any points and pitch angles as
an initial condition for the equation of motion by Wand in
the 3D space. Because the HINT2 data takes in the divertor region, we can analyze the orbit there. In the Fig. 3, it
is found that the particle moves along the divertor plates
or the wall with a complex orbit.
4Conclusion

Streamline of magnetic-ﬁeld and orbit of drift particleof equilibrium LHD plasmas by HINT2 simulation code
were demonstrated in the LHD vessel in the immersive
3D space by the VR system. The HINT2 simulation data
included the divertor region. It became possible to investigate the magnetic-ﬁeld structure and the particle orbits inFig. 3. Tracing of the particle trajectory in the divertor
region. The magenta line shows the particle trajectory.

Collaborative Research
NIFS09KDBN004).

Program(NIFS09KDAN004,

References

Fig. 1. Scientiﬁc visualization of the Large Helical Device(LHD) plasma by Virtual LHD in the LHD vessel in theVR space. Green line shows the stream line of magneticﬁeld. The black plates are the divertor plates. Top andbottom panels show the same magnetic-ﬁeld line from thediﬀerent view point.

the divertor region. It is hard to recognize the stochastic
structure of magnetic-ﬁeld as shown in Fig. 2. In order toconﬁrm the existence of the magnetic islands and stochastic regions in the periphery and divertor region, Poincare
map is useful. In the near future, we will add a function ofdrawing the Poincare map of the magnetic-ﬁeld structure
simultaneously to Virtual LHD.
VR technology is powerful equipment for analyzing simulation data. We believe that the buildup in this paper
will boost up the research of the plasma physics and fusion plasmas.
Acknowledgement
This work was performed under the auspices ofthe National Institute for Fusion Science (NIFS)[1] C. Cruz-Neira, D. J. Sandin, and T. A. DeFanti, Surroundscreen projection-based virtual reality: The design
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Fig. 2. Magnetic ﬁeld structure. The starting point of thestreamline is diﬀerent from that in Fig. 1.