YouJun Hu's Homepage

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Research interests

Computational plasma physics; Machine learning

I am currently working on using machine learning to reconstruct magnetic/kinetic equilibrium in tokamaks. Meanwhile, I also work on particle simulation of tokamak turbulence, the interaction of energetic particles and MHD modes, and noninductive current drive. I love programming (primarily in Python and Fortran). Some codes I developed can be found here

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Research notes

• Notes on Tokamak equilibrium [PDF]
• Nonlinear gyrokinetic equation][HTML in one file] [PDF]
• Particle in cell simulation [PDF] [source code]
• Guiding center motion in tokamaks [PDF]
• Linear MHD Theory of Tokamak Plasmas [PDF] [HTML] [HTML in one file]
• Notes on Collisionless Drift Kinetic Equation [PDF] [HTML]
• Notes on Landau damping [PDF] [HTML]
• Numerical modeling of neutral beam injection
• Beam driven current
• Fokker-Planck collision operator
• Computational Physics [PDF]
• Fourier analysis [PDF] [HTML]
• Machine Learning [PDF]
• Full orbit integrator: Boris algorithm

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Talks

• ITPA-EP-35: ITPA-EP TAE benchmark using a new gyrokinetic PIC code TEK

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Publications

1. Anisotropic distribution of alpha particles in a tokamak reactor ,
   Youjun Hu, et al., Nucl. Fusion 65 (2025) 066022
   
2. Simulation of neutral beam current drive on EAST tokamak,
   Youjun Hu, et al., Phys. Plasmas 30, 092507 (2023)
   
3. Fast equilibrium reconstruction by deep learning on EAST tokamak,
   JingJing Lu, Youjun Hu, Nong Xiang, Youwen Sun, AIP Advances 13, 075007 (2023)
   
4. Effects of resonant magnetic perturbations on neutral beam heating in a tokamak,
   Youjun Hu, et al., Phys. Plasmas 28, 122502 (2021)
   
5. Fully Kinetic Simulation of Ion-Temperature-Gradient Instabilities in Tokamaks,
   Youjun Hu, Matthew T. Miecnikowski, Yang Chen and Scott E. Parker, Plasma 1, 10 (2018)
   
6. Kinetic-MHD hybrid simulation of fishbone modes excited by fast ions on EAST tokamak,
   Youbin Pei, N. Xiang, Youjun Hu, Y. Todo et al., Phys. Plasmas 24, 032507(2017)
   
7. Simulation of fast-ion-driven Alfven eigenmodes on EAST tokamak,
   Youjun Hu, Y. Todo,Youbin Pei, Guoqiang Li, Jinping Qian, et al., Phys. Plasmas 23, 022505 (2016)
   Erratum_2016-3-11.PDF
8. Numerical study of Alfven eigenmodes on EAST tokamak,
   Youjun Hu, Guoqiang Li, N. N. Gorelenkov, Huishan Cai, et al., Phys. Plasmas 21, 052510 (2014)
   Erratum_2014-8-22.PDF
9. Electron shielding current in neutral beam current drive in general tokamak equilibria and arbitrary collisionality regime,
   Youjun Hu, Yemin Hu, and Y.R. Lin-Liu, Phys. Plasmas 19, 034505 (2012)
10. Relativistic collision operators for modeling noninductive current drive by waves,
    Youjun Hu, Yemin Hu, and Y.R. Lin-Liu, Phys. Plasmas 18, 022504 (2011).
    Erratum_2012-7-19
11. Drift kink instability in the current sheet with a kappa-distribution,
    Youjun Hu, Weihong Yang, Yinhua Chen, et al. Phys. Plasmas 15, 082114 (2008).
12. Lower-Hybrid Drift Instability in Modified Harris Current Sheet,
    Hu Youjun, Yang Weihong, Chen Yinhua et al., Plasma Sci. Technol. 10, 416 (2008).
13. Resonant absorption via mode conversion in magnetized inhomogeneous plasma,
    Hu Youjun, Yang Weihong, Chen Yinhua, Zhang Yu, Chinese Journal of Computational Physics (in Chinese) Vol. 24, No. 3, 330-336 (2007)

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Some Visualizations

The following figures visualize magnetic field lines on tokamak magnetic surfaces with different values of safety factor q.



Fig. Magnetic field lines on q=1/10 magnetic surface (upper left), q=1/2 magnetic surface (upper right), q=1 magnetic surface (middle left), q=2 magnetic surface (middle right), q=3 magnetic surface (lower left), and q=4 magnetic surface (lower right). Source codes for producing these figures: p.sh and torus.sketch.



Fig. Left: 3D view of guiding-center motion in tokamak; Right: 2D poloidal view

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