Plasma and Fusion Research

Volume 20, 1403058 (2025)

Regular Articles

Development of a Hybrid Fast Ion Transport Code with Bounce Time-Step-Based Orbit-Following and Drift Orbit-Following
Kouji SHINOHARA1,3), Keiji TANI2), Nobuhiko HAYASHI3), Shuhei SUMIDA3), Akira EJIRI1), Naoto TSUJII1), Takeru INOUE1), Masanobu SUZUKI3), Andreas BIERWAGE3), Yu-Ting LIN1), Yiming TIAN1), Fumiya ADACHI1), Shunya ABE1), Yuta TAKECHI1)
1)
The University of Tokyo, Chiba 277-8561, Japan
2)
Kyoto Fusioneering, Tokyo 100-0004, Japan
3)
QST, Naka Institute for Fusion Science and Technology, Ibaraki 311-0193, Japan
(Received 16 September 2025 / Accepted 23 October 2025 / Published 24 December 2025)

Abstract

We developed a bounce-time-based (BT) orbit-following Monte-Carlo code in order to calculate a fast ion transport in the previous work as an extension of the OFMC code in QST. In the BT method, we take a bounce time as a time step of the orbit following for the purpose of reducing computational resources. However, the BT method code has limitations in its realistic application. In order to reduce the limitation, we have developed a hybrid code with the BT method and a drift orbit-following method. In the code, we can switch the methods depending on conditions for each purpose. With using this hybrid code, we have reduced the difference between the BT method and drift orbit-following method in the distribution of fast ions and heating in the plasma central region, which was observed in the previous work, and have been able to adopt a realistic first wall as a loss boundary instead of a separatrix. We have also applied this hybrid approach to handle a fast ion transport in a toroidal field ripple. The hybrid calculation well reproduced the profiles of several quantities obtained by the drift orbit calculation alone while reducing the calculation time.

Keywords

fast ion transport, bounce time, finite orbit width, Monte Carlo code, tokamak

DOI: 10.1585/pfr.20.1403058

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References

  • [1] N. Hayashi and JT-60 Team, Phys. Plasmas 17, 056112 (2010).
  • [2] A. Fukuyama et al., Proc. 20th IAEA FEC (Villamoura, Portugal, 2004) IAEA-CSP-25/CD/TH/P2-3.
  • [3] S. Mochinaga et al., Nucl. Fusion 64, 066002 (2024).
  • [4] K. Tani et al., J. Phys. Soc. Jpn. 50, 1726 (1981).
  • [5] K. Tobita et al., Nucl. Fusion 35, 1585 (1995).
  • [6] K. Shinohara et al., Nucl. Fusion 47, 997 (2007).
  • [7] K. Shinohara et al., Nucl. Fusion 43, 586 (2003).
  • [8] G.J. Kramer et al., Nucl. Fusion 53, 123018 (2013).
  • [9] JT-60SA Research Plan, https://www.qst.go.jp/uploaded/attachment/6690.pdf.
  • [10] K. Shinohara et al., Fusion Eng. Des. 84, 24 (2009).
  • [11] K. Shinohara et al., Nucl. Fusion 51, 063028 (2011).
  • [12] K. Tani et al., Nucl. Fusion 52, 013012 (2012).
  • [13] K. Shinohara et al., Nucl. Fusion 52, 094008 (2012).
  • [14] K. Shinohara et al., Plasma Fusion Res. 20, 1403017 (2025).
  • [15] B.A. Trubnikov, Rev. Plasma Phys. 1, 105 (1965).
  • [16] K. Shinohara et al., Nucl. Fusion 60, 096032 (2020).