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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.”
A. Weller, S. Sakakibara, K. Y. Watanabe, K. Toi, J. Geiger, M. C. Zarnstorff, S. R. Hudson, A. Reiman, A. Werner, C. Nührenberg, S. Ohdachi, Y. Suzuki, H. Yamada, W7-AS Team, LHD Team
Fusion Science and Technology | Volume 50 | Number 2 | August 2006 | Pages 158-170
Technical Paper | Stellarators | doi.org/10.13182/FST06-A1231
Articles are hosted by Taylor and Francis Online.
Substantial progress has been achieved in raising the plasma beta in stellarators and helical systems by high-power neutral beam heating, approaching reactor-relevant values. The achievement of high-beta operation is closely linked with configuration effects on the confinement and with magnetohydrodynamic (MHD) stability.The magnetic configurations of the Wendelstein 7-AS (W7-AS) stellarator and of the Large Helical Device (LHD) and their optimization for high-beta operation within the flexibility of the devices are characterized. A comparative description of the accessible operational regimes in W7-AS and LHD is given. The finite-beta effects on the flux surfaces depend on the degree of configuration optimization. In particular, a large Shafranov shift is accompanied by formation of islands and stochastic field regions as found by numerical equilibrium studies. However, the observed pressure gradients indicate some mitigation of the effects on the plasma confinement, presumably because of the high collisionality of high-beta plasmas and island healing effects (LHD). As far as operational limits by pressure-driven MHD instabilities are concerned, only weak confinement degradation effects are usually observed, even in linearly unstable regimes.The impact of the results concerning high-beta operation in W7-AS and LHD on the future stellarator program will be discussed, including the relationship to tokamak research. Some of the future key issues appear to be the following: the control of the magnetic configuration (including toroidal current control), the modification of confinement and MHD properties toward the low-collisional regime, and the compatibility of high-beta regimes with power and particle exhaust requirements to achieve steady-state operation.