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Fusion Science and Technology
ANS members approve amendment adding YMG rep to board of directors
The American Nuclear Society will include a representative from the Young Members Group on its Board of Directors after ANS members voted this week overwhelmingly in favor of amending Article B6 of the ANS bylaws. The change was mandated by Objective Outcome 5 of the ANS Change Plan 2020.
To keep the number of directors at 16, the approved amendment decreased the number of non–U.S. resident directors from three to two.
Hongda He, J. Q. Dong, Zhixiong He, K. Zhao
Fusion Science and Technology | Volume 70 | Number 1 | July 2016 | Pages 54-61
Technical Paper | dx.doi.org/10.13182/FST15-169
Articles are hosted by Taylor and Francis Online.
The density gradient of fast ions is the main driving force for fishbone instability that in turn results in fast ion loss. It is possible to reduce the instability by eliminating the density gradient of the fast ions by employing dual neutral beam injection (DNBI) in tokamak plasmas. The dispersion relation for the fishbone instability is applied to the case of DNBI with suitable fast ion distribution functions. The results show that the density distribution of fast ions of DNBI can bring about a stable window that is a range of values for the distance between the on-axis beam and the off-axis beam that yields an overall stabilization of the resultant fishbone mode. The width of the stable window increases linearly with the position of the safety factor q = 1 magnetic flux surface increasing. In addition, the width of the stable window becomes wider for a more peaked density profile of fast ions and keeps constant for a peaked enough density profile of fast ions. The growth rates of the fishbone modes dramatically decrease with the intensity ratio of off-axis neutral beam injection (NBI) and on-axis NBI, and the critical beta values of fast ions increase with the intensity ratio increasing. Fishbone modes can be avoided with DNBI, which may be an effective method to prevent fast ion loss resulting from fishbone instabilities.