Plasma and Fusion Research

Volume 15, 2405059 (2020)

Regular Articles

Comparative Studies on the Control Algorithm for the High-Density Ignition Regime in FFHR-d1

Osamu MITARAI, Shota SUGIYAMA¹⁾, Nagato YANAGI²⁾, Yoshiro NARUSHIMA²⁾, Ryuichi SAKAMOTO²⁾, Takuya GOTO²⁾, Hideaki MATSUURA¹⁾ and Akio SAGARA²⁾

: Institute for Advanced Fusion and Physics Education, 2-14-8 Tokuou, Kitaku, Kumamoto 861-5525, Japan
1): Department of Applied Quantum Physics and Nuclear Engineering, Kyushu University, 744 Motooka, Fukuoka 819-0395, Japan
2): National Institute for Fusion Science, 322-6 Oroshi-cho, Toki 509-5292, Japan

(Received 27 November 2019 / Accepted 21 June 2020 / Published 6 August 2020)

Abstract

In the Force Free Helical Reactor FFHR-d1 (R∼15.7 m, a∼2.5 m, B_o ∼4.5 T, 〈β〉∼5 % and the fusion power of 3 GW) [1, 2], it is demonstrated that the thermally unstable operation is better to achieve the higher density and lower temperature plasma (n(0)∼ 9 × 10²⁰ m⁻³ and T(0)∼7 keV) than the impurity injection method. One drawback of the thermally unstable operation is a possibility of the thermal runaway when fueling systems have failures. However, we have found that the inherently safe function exists owing to the plasma outward shift during the thermal runaway. Thus we continue to pursue this high-density operation scenario for FFHR-d1. Preliminary estimation of the alpha energy loss fraction of ∼3 % is obtained for a broad density profile in the high-density ignition regime.

Keywords

helical system, ignition, impurity injection, thermally unstable, alpha particle loss

DOI: 10.1585/pfr.15.2405059

Full Text

PDF format (1.1Mbytes) PDF Download

References

[1] A. Sagara et al., Fusion Eng. Des. 87, 594 (2012).
[2] T. Goto et al., Plasma Fusion Res. 7, 2405084 (2012).
[3] N. Ohyabu, T. Morisaki, S. Masuzaki, R. Sakamoto et al., Phy. Rev. Lett. 97, 055002 (2006).
[4] O. Mitarai et al., Plasma Fusion Res. 2, 021 (2007).
[5] O. Mitarai et al., Fusion Sci. Technol. 56, 1495 (2009).
[6] O. Mitarai, A. Sagara et al., “The high density ignition in FFHR helical reactor by neutral beam injection (NBI) heating” IAEA-FEC-FTP/P6-19 (2010, Daejon, Korea).
[7] K. Watanabe et al., Nucl. Fusion 32, 1499 (1992).
[8] J. Mandrekas and W.M. Stacy Jr., Fusion Technol. 19, 57 (1991).
[9] T.Watanabe et al., Plasma Fusion Res. 10, 3405054 (2015).
[10] O. Mitarai et al., Fusion Eng. Des. 136, Part A, 82 (2018).
[11] O. Mitarai, A. Sagara and R. Sakamoto, “Control concept for the high density and low temperature ignition in the FFHR helical reactor”, Chapter 4, page 128, in Fusion Energy and Power: Applications, Technologies and Challenges (Nova Science Publisher, 2015).
[12] O. Mitarai, A. Sagara et al., Plasma Fusion Res. 5, S1001 (2010).
[13] K. Yamazaki et al., Fusion Technol. 21, 147 (1992).
[14] S. Ohdachi, K.Y. Watanabe et al., Nucl. Fusion 57, 066042 (2017).
[15] H. Matsuura et al., Plasma Fusion Res. 6, 2405086 (2011).
[16] Y. Masaoka et al., Nucl. Fusion 53, 093030 (2013).
[17] D.A. Spong et al., Bull. Am. Phys. Soc. 44, 215 (1999).
[18] S.P. Hirshman and J. Whitson, Phys. Fluids 26, 3553 (1983).
[19] M.Yu. Isaev et al., Nucl. Fusion 43, 1066 (2003).