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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.”
Yu. Turkin, H. Maassberg, C. D. Beidler, J. Geiger, N. B. Marushchenko
Fusion Science and Technology | Volume 50 | Number 3 | October 2006 | Pages 387-394
Technical Paper | Stellarators | doi.org/10.13182/FST06-5
Articles are hosted by Taylor and Francis Online.
The magnetic configuration of the Wendelstein 7-X (W7-X) stellarator is optimized following a set of criteria including a rotational transform profile with low shear and minimized bootstrap current that must be controlled for proper functioning of the island divertor. This paper studies the compensation of residual bootstrap current by using electron cyclotron current drive (ECCD). The modeling shows that the loop voltage induced by ECCD leads to a redistribution of the current density with a diffusion time of ~2 s. The relaxation time of the total current is much longer, however - for W7-X plasma parameters the total toroidal current reaches steady state after several L/R times requiring hundreds of seconds. In order to keep the toroidal current and its profile in the acceptable range, a feed-forward or predictive control method using ECCD as actuator is proposed. The main steps are as follows: (a) calculate the bootstrap current distribution using plasma parameters measured in the online transport analysis and (b) determine and apply ECCD as needed. For the current control to work properly and to avoid long relaxation times, the reaction time of the control loop must be less than the current skin time.