Calculation of collisionless pitch-angle scattering of runaway electrons with synchrotron radiation via high-order guiding-centre equation

Journal Article · Thu Oct 06 00:00:00 EDT 2022 · Journal of Plasma Physics

DOI:https://doi.org/10.1017/s0022377822000861· OSTI ID:1999803

Liu, Shi-Jie  ^[1]; Wang, Feng ^[1]; Liu, Chang  ^[2]; Hu, Di ^[3]; Wu, Kai-Bang ^[1]; Liu, Jian  ^[4]; Wang, Zheng-Xiong ^[1]

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1. Dalian Univ. of Technology (China)
2. Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)
3. Beihang University, Beijing (China)
4. Univ. of Science and Technology of China, Hefei (China); Qilu University of Technology, Jinan (China)

Recently, the collisionless pitch-angle scattering for relativistic runaway electrons (REs) in toroidal geometries such as tokamaks was discovered through a full orbit simulation approach (Liu et al., Nucl. Fusion, vol. 56, 2016, p. 064002), and it was then theoretically investigated that a new expression for the magnetic moment, including the second-order corrections, could essentially reproduce the so-called collisionless pitch-angle scattering process (Liu et al., Nucl. Fusion, vol. 58, 2018, p. 106018). In this paper, with synchrotron radiation, extensive numerical verification of the validity of the high-order guiding-centre theory is given for simulations involving REs by incorporating such an expression for the magnetic moment into our particle tracing code. A high-order guiding-centre simulation approach with synchrotron radiation (HGSA) is applied. Synchrotron radiation plays an essential role in the life cycle of REs. The energy of REs first increases and then becomes saturated until the electric field acceleration is balanced by the radiation dissipation. Unfortunately, the process cannot be simulated accurately with the standard guiding-centre model, i.e. the first-order guiding-centre model. Remarkably, it is found that the HGSA can effectively produce the fundamental process of REs. Since the time scale of the energy saturation of REs is close to seconds, the computational cost becomes significant. In order to save costs, it is necessary to estimate the time of energy saturation. An analytical estimate is derived for the time it takes for synchrotron drag to balance an accelerating electric field and the provided formula has been numerically verified. Finally, test calculations reveal that HGSA is favourable for exploiting the dynamics of REs in tokamak plasmas.

• Research Organization: Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)
• Sponsoring Organization: USDOE; National Key Research and Development Program of China; National Natural Science Foundation of China (NSFC); Fundamental Research Funds for the Central Universities
• Grant/Contract Number: AC02-09CH11466; 2022YFE03090000; 11975068; 11925501; DUT22ZD215
• OSTI ID: 1999803
• Journal Information: Journal of Plasma Physics, Vol. 88, Issue 5; ISSN 0022-3778
• Publisher: Cambridge University Press
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
runaway electrons
plasma simulation
fusion plasma