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Fusion Science and Technology
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General Kenneth Nichols and the Manhattan Project
Nichols
The Oak Ridger has published the latest in a series of articles about General Kenneth D. Nichols, the Manhattan Project, and the 1954 Atomic Energy Act. The series has been produced by Nichols’ grandniece Barbara Rogers Scollin and Oak Ridge (Tenn.) city historian David Ray Smith. Gen. Nichols (1907–2000) was the district engineer for the Manhattan Engineer District during the Manhattan Project.
As Smith and Scollin explain, Nichols “had supervision of the research and development connected with, and the design, construction, and operation of, all plants required to produce plutonium-239 and uranium-235, including the construction of the towns of Oak Ridge, Tennessee, and Richland, Washington. The responsibility of his position was massive as he oversaw a workforce of both military and civilian personnel of approximately 125,000; his Oak Ridge office became the center of the wartime atomic energy’s activities.”
Hongda He, J. Q. Dong, Zhixiong He, K. Zhao
Fusion Science and Technology | Volume 70 | Number 1 | July 2016 | Pages 54-61
Technical Paper | 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.
