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2. The Role of Nature in New England Puritan Theology: The Case of Samuel Willard

Author

Wolfe Stephen M.

Subjects
samuel willard, natural law, natural religion, reformed orthodoxy, new england puritans, Philosophy. Psychology. Religion
Abstract

This article discusses the role of nature in the theological system of New England minister Samuel Willard (1640-1707). I focus specifically on his account of theological anthropology, the relationship of nature and grace, and the moral (or natural) law, and show how each relates to his views on civil government and civil law. Willard affirmed the natural law, natural religion, and natural worship, and he acknowledged and respected pagan civic virtue and grounded civil order and social relations in nature. Willard’s theological articulations are substantively the same as those found among the ‘Reformed orthodox’ theologians of 17th century Europe, which provides evidence for the thesis that Reformed orthodoxy was a transatlantic movement. His reliance on nature also corrects scholarship on the New England Puritans, which often assumes that they rejected the Christian natural law tradition.

Published
2022
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3. Control of plasma stored energy for burn control using DIII-D in-vessel coils

Author

Massachusetts Institute of Technology. Plasma Science and Fusion Center, Wolfe, Stephen M, Hawryluk, R. J., Eidietis, N. W., Grierson, B. A., Hyatt, A. W., Kolemen, E., Logan, N. C., Nazikian, R., Paz-Soldan, C., Solomon, W. M., Massachusetts Institute of Technology. Plasma Science and Fusion Center, Wolfe, Stephen M, Hawryluk, R. J., Eidietis, N. W., Grierson, B. A., Hyatt, A. W., Kolemen, E., Logan, N. C., Nazikian, R., Paz-Soldan, C., and Solomon, W. M.

Abstract

A new approach has been experimentally demonstrated to control the stored energy by applying a non-axisymmetric magnetic field using the DIII-D in-vessel coils to modify the energy confinement time. In future burning plasma experiments as well as magnetic fusion energy power plants, various concepts have been proposed to control the fusion power. The fusion power in a power plant operating at high gain can be related to the plasma stored energy and hence, is a strong function of the energy confinement time. Thus, an actuator that modifies the confinement time can be used to adjust the fusion power. In relatively low collisionality DIII-D discharges, the application of non-axisymmetric magnetic fields results in a decrease in confinement time and density pumpout. Gas puffing was used to compensate the density pumpout in the pedestal while control of the stored energy was demonstrated by the application of non-axisymmetric fields.

Published
2018

4. High-field side scrape-off layer investigation: Plasma profiles and impurity screening behavior in near-double-null configurations

Author

Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Labombard, Brian, Kuang, Adam QingYang, Brunner, Daniel Frederic, Faust, Ian Charles, Walk Jr, John R, Chilenski, Mark Alan, Lin, Ya, Marmar, Earl S, Wallace, Gregory Marriner, Whyte, Dennis G, Wolfe, Stephen M, Wukitch, Stephen James, Faust, I., Mumgaard, R., Reinke, M.L., Marmar, Earl S., Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Labombard, Brian, Kuang, Adam QingYang, Brunner, Daniel Frederic, Faust, Ian Charles, Walk Jr, John R, Chilenski, Mark Alan, Lin, Ya, Marmar, Earl S, Wallace, Gregory Marriner, Whyte, Dennis G, Wolfe, Stephen M, Wukitch, Stephen James, Faust, I., Mumgaard, R., Reinke, M.L., and Marmar, Earl S.

Abstract

New experiments on Alcator C-Mod reveal that the favorable impurity screening characteristics of the high-field side (HFS) scrape-off layer (SOL), previously reported for single null geometries, is retained in double null configurations, despite the formation of an extremely thin SOL. In balanced double-null, nitrogen injected locally into the HFS SOL is better screened by a factor of 2.5 compared to the same injection into the low field side (LFS) SOL. This result is insensitive to plasma current and Greenwald fraction. Nitrogen injected into the HFS SOL is not as well screened (only a factor of 1.5 improvement over LFS) in unbalanced double-null discharges, when the primary divertor is in the direction of B×∇B. In this configuration, impurity ‘plume’ emission patterns indicate that an opposing E × B drift competes with the parallel impurity flow to the divertor. In balanced double-null plasmas, the dispersal pattern exhibits a dominant E × B motion. Unbalanced discharges with the primary divertor opposite the direction of B×∇B exhibit excellent HFS screening characteristics – a factor of 5 enhancement compared to LFS. These data support the idea that future tokamaks should locate all RF actuators and close-fitting wall structures on the HFS and employ near-double-null magnetic topologies, both to precisely control plasma conditions at the antenna/plasma interface and to maximally mitigate the impact of local impurity sources arising from plasma-material interactions. Keywords: Alcator C-Mod; Impurity screening; Double null; High field side scrape-off layer, United States. Department of Energy (Contract DE-FC02-99ER54512)

Published
2018

5. Non-resonant destabilization of (1/1) internal kink mode by suprathermal electron pressure

Author

Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Shiraiwa, Shunichi, Irby, James Henderson, Granetz, Robert S, Parker, Ronald R, Baek, Seung Gyou, Faust, Ian Charles, Wallace, Gregory Marriner, Mumgaard, Robert Thomas, Gao, Chi, Greenwald, Martin J, Hubbard, Amanda E, Hughes Jr, Jerry, Marmar, Earl S, Rice, John E, Wolfe, Stephen M, Delgado-Aparicio, L., Sugiyama, L., Gates, D. A., Gorelenkov, N., Scott, S., Bertelli, N., Phillips, P. E., Rowan, W. L., Wilson, R., Wukitch, S., Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Shiraiwa, Shunichi, Irby, James Henderson, Granetz, Robert S, Parker, Ronald R, Baek, Seung Gyou, Faust, Ian Charles, Wallace, Gregory Marriner, Mumgaard, Robert Thomas, Gao, Chi, Greenwald, Martin J, Hubbard, Amanda E, Hughes Jr, Jerry, Marmar, Earl S, Rice, John E, Wolfe, Stephen M, Delgado-Aparicio, L., Sugiyama, L., Gates, D. A., Gorelenkov, N., Scott, S., Bertelli, N., Phillips, P. E., Rowan, W. L., Wilson, R., and Wukitch, S.

Abstract

New experimental observations are reported on the structure and dynamics of short-lived periodic (1, 1) "fishbone"-like oscillations that appear during radio frequency heating and current-drive experiments in tokamak plasmas. For the first time, measurements can directly relate changes in the high energy electrons to the mode onset, saturation, and damping. In the relatively high collisionality of Alcator C-Mod with lower hybrid current drive, the instability appears to be destabilized by the non-resonant suprathermal electro n pressure - rather than by wave-particle resonance, rotates toroidally with the plasma and grows independently of the (1, 1) sawtooth crash driven by the thermal plasma pressure., United States. Department of Energy (Contract DE-FC02-99ER54512), United States. Department of Energy (Contract DE-SC0007883)

Published
2018

6. Alcator C-Mod: research in support of ITER and steps beyond

Author

Candy, J., Canik, J., Churchill, R.M., Holland, C., Loarte, A., Reinke, M.L., Scott, S., Snyder, P., Theiler, C., Diallo, A., Edlund, E., LaBombard, B., Baek, Seung Gyou, Marmar, Earl S, Barnard, Harold Salvadore, Bonoli, Paul T, Brunner, Daniel Frederic, Ennever, Paul Chappell, Fiore, Catherine L, Gao, Chi, Golfinopoulos, Theodore, Greenwald, Martin J, Hartwig, Zachary Seth, Hubbard, Amanda E, Hughes Jr, Jerry, Hutchinson, Ian Horner, Irby, James Henderson, Labombard, Brian, Lin, Yijun, Mumgaard, Robert Thomas, Parker, Ronald R, Porkolab, Miklos, Rice, John E, Shiraiwa, Shunichi, Sorbom, Brandon Nils, Terry, David Rankin, Terry, James L, Vieira, Rui F, Walk Jr, John R, Wallace, Gregory Marriner, White, Anne E., Whyte, Dennis G, Wolfe, Stephen M, Wright, John C, Wright, Graham, Wukitch, Stephen James, Xu, Peng, Cziegler, Istvan, Dekow, Gary L, Delgado-Aparicio, Luis, Lipschultz, Bruce, Theiler, Christian, Diallo, Ahmed Y, Edlund, Eric Matthias, Faust, Ian Charles, Massachusetts Institute of Technology. Department of Biological Engineering, Massachusetts Institute of Technology. Department of Mathematics, Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Department of Physics, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Hutchinson Ian, Baek, Seung Gyou, Marmar, Earl S, Barnard, Harold Salvadore, Bonoli, Paul T, Brunner, Daniel Frederic, Ennever, Paul Chappell, Fiore, Catherine L, Gao, Chi, Golfinopoulos, Theodore, Greenwald, Martin J, Hartwig, Zachary Seth, Hubbard, Amanda E, Hughes Jr, Jerry, Hutchinson, Ian Horner, Irby, James Henderson, Labombard, Brian, Lin, Yijun, Mumgaard, Robert Thomas, Parker, Ronald R, Porkolab, Miklos, Rice, John E, Shiraiwa, Shunichi, Sorbom, Brandon Nils, Terry, David Rankin, Terry, James L, Vieira, Rui F, Walk Jr, John R, Wallace, Gregory Marriner, White, Anne E., Whyte, Dennis G, Wolfe, Stephen M, Wright, John C, Wright, Graham, Wukitch, Stephen James, Xu, Peng, Cziegler, Istvan, Dekow, Gary L, Delgado-Aparicio, Luis, Lipschultz, Bruce, Theiler, Christian, Diallo, Ahmed Y, Edlund, Eric Matthias, and Faust, Ian Charles

Subjects
Nuclear and High Energy Physics, Materials science, Tokamak, Divertor, Nuclear engineering, Cyclotron, FEC 2014, chemistry.chemical_element, overview, Electron, Tungsten, Condensed Matter Physics, law.invention, Pedestal, Alcator C-Mod, chemistry, law, Dielectric heating, Atomic physics, tokamak
Abstract

This paper presents an overview of recent highlights from research on Alcator C-Mod. Significant progress has been made across all research areas over the last two years, with particular emphasis on divertor physics and power handling, plasma–material interaction studies, edge localized mode-suppressed pedestal dynamics, core transport and turbulence, and RF heating and current drive utilizing ion cyclotron and lower hybrid tools. Specific results of particular relevance to ITER include: inner wall SOL transport studies that have led, together with results from other experiments, to the change of the detailed shape of the inner wall in ITER; runaway electron studies showing that the critical electric field required for runaway generation is much higher than predicted from collisional theory; core tungsten impurity transport studies reveal that tungsten accumulation is naturally avoided in typical C-Mod conditions., United States. Department of Energy (DE-FC02-99ER54512-CMOD), United States. Department of Energy (DE-AC02-09CH11466), United States. Department of Energy (DE-FG02-96ER-54373), United States. Department of Energy (DE-FG02-94ER54235)

Published
2015

7. Effects of Magnetic Shear on Toroidal Rotation in Tokamak Plasmas with Lower Hybrid Current Drive

Author

Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Department of Physics, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Rice, John E., Podpaly, Y. A., Reinke, Matthew Logan, Mumgaard, Robert Thomas, Shiraiwa, Shunichi, Wallace, Gregory Marriner, Gao, Chi, Granetz, Robert S., Hughes, Jerry W., Parker, Ronald R., Bonoli, Paul T., Greenwald, Martin J., Hubbard, Amanda E., Hutchinson, Ian H., Irby, James Henderson, Marmar, Earl S., Wolfe, Stephen M., Scott, S. D., Chouli, B., Fenzi-Bonizec, C., Nave, M. F. F., Diamond, P. H., Delgado-Aparicio, Luis, Eriksson, L.-G., Giroud, C., Kirov, K., Mailloux, J., Hughes Jr, Jerry, Parker, R., Hubbard, Amanda E, Hutchinson, Ian Horner, Wolfe, Stephen M, Podpaly, Yuri, Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Department of Physics, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Rice, John E., Podpaly, Y. A., Reinke, Matthew Logan, Mumgaard, Robert Thomas, Shiraiwa, Shunichi, Wallace, Gregory Marriner, Gao, Chi, Granetz, Robert S., Hughes, Jerry W., Parker, Ronald R., Bonoli, Paul T., Greenwald, Martin J., Hubbard, Amanda E., Hutchinson, Ian H., Irby, James Henderson, Marmar, Earl S., Wolfe, Stephen M., Scott, S. D., Chouli, B., Fenzi-Bonizec, C., Nave, M. F. F., Diamond, P. H., Delgado-Aparicio, Luis, Eriksson, L.-G., Giroud, C., Kirov, K., Mailloux, J., Hughes Jr, Jerry, Parker, R., Hubbard, Amanda E, Hutchinson, Ian Horner, Wolfe, Stephen M, and Podpaly, Yuri

Abstract

Application of lower hybrid (LH) current drive in tokamak plasmas can induce both co- and countercurrent directed changes in toroidal rotation, depending on the core q profile. For discharges with q[subscript 0] < 1, rotation increments in the countercurrent direction are observed. If the LH-driven current is sufficient to suppress sawteeth and increase q[subscript 0] above unity, the core toroidal rotation change is in the cocurrent direction. This change in sign of the rotation increment is consistent with a change in sign of the residual stress (the divergence of which constitutes an intrinsic torque that drives the flow) through its dependence on magnetic shear., United States. Dept. of Energy (Contract DE-FC02-99ER54512), United States. Dept. of Energy (Fusion Research Postdoctoral Research Program)

Published
2014

8. X-ray imaging crystal spectroscopy for use in plasma transport research

Author

Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Hutchinson, Ian, Reinke, Matthew Logan, Podpaly, Yuri, Hutchinson, Ian H., Rice, John E., Gao, Chi, Greenwald, Martin J., Howard, Nathaniel Thomas, Hubbard, Amanda E., Hughes, Jerry W., White, Anne E., Wolfe, Stephen M., Bitter, M., Delgado-Aparicio, Luis, Hill, K., Pablant, N., Hutchinson, Ian Horner, Hubbard, Amanda E, Hughes Jr, Jerry, Wolfe, Stephen M, Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Hutchinson, Ian, Reinke, Matthew Logan, Podpaly, Yuri, Hutchinson, Ian H., Rice, John E., Gao, Chi, Greenwald, Martin J., Howard, Nathaniel Thomas, Hubbard, Amanda E., Hughes, Jerry W., White, Anne E., Wolfe, Stephen M., Bitter, M., Delgado-Aparicio, Luis, Hill, K., Pablant, N., Hutchinson, Ian Horner, Hubbard, Amanda E, Hughes Jr, Jerry, and Wolfe, Stephen M

Abstract

This research describes advancements in the spectral analysis and error propagation techniques associated with x-ray imaging crystal spectroscopy (XICS) that have enabled this diagnostic to be used to accurately constrain particle, momentum, and heat transport studies in a tokamak for the first time. Dopplertomography techniques have been extended to include propagation of statistical uncertainty due to photon noise, the effect of non-uniform instrumental broadening as well as flux surface variations in impurity density. These methods have been deployed as a suite of modeling and analysis tools, written in interactive data language (IDL) and designed for general use on tokamaks. Its application to the Alcator C-Mod XICS is discussed, along with novel spectral and spatial calibration techniques. Example ion temperature and radial electric field profiles from recent I-mode plasmas are shown, and the impact of poloidally asymmetric impurity density and natural line broadening is discussed in the context of the planned ITER x-ray crystal spectrometer., United States. Dept. of Energy (Contract DE-FC02-99ER54512), United States. Dept. of Energy (Contract DE-AC02-09CH11466), United States. Dept. of Energy (Fusion Research Postdoctoral Research Program)

Published
2014

9. Multi-device studies of pedestal physics and confinement in the I-mode regime

Author

Massachusetts Institute of Technology. Plasma Science and Fusion Center, Whyte, Dennis, Hubbard, Amanda E, Hughes Jr, Jerry, Marinoni, Alessandro, Marmar, Earl S, Rice, John E, Walk Jr, John R, Whyte, Dennis G, Wolfe, Stephen M, Osborne, T., Ryter, F., Austin, M., Barrera Orte, L., Churchill, R. M., Cziegler, I., Fenstermacher, M., Fischer, R., Gerhardt, S., Groebner, R., Gohil, P., Happel, T., Loarte, A., Maingi, R., Manz, P., McDermott, R. M., McKee, G., Rhodes, T. L., Schmitz, L., Theiler, C., Viezzer, E., Walk, J. R., Wolfrum, E., Yan, Z., Massachusetts Institute of Technology. Plasma Science and Fusion Center, Whyte, Dennis, Hubbard, Amanda E, Hughes Jr, Jerry, Marinoni, Alessandro, Marmar, Earl S, Rice, John E, Walk Jr, John R, Whyte, Dennis G, Wolfe, Stephen M, Osborne, T., Ryter, F., Austin, M., Barrera Orte, L., Churchill, R. M., Cziegler, I., Fenstermacher, M., Fischer, R., Gerhardt, S., Groebner, R., Gohil, P., Happel, T., Loarte, A., Maingi, R., Manz, P., McDermott, R. M., McKee, G., Rhodes, T. L., Schmitz, L., Theiler, C., Viezzer, E., Walk, J. R., Wolfrum, E., and Yan, Z.

Abstract

This paper describes joint ITPA studies of the I-mode regime, which features an edge thermal barrier together with L-mode-like particle and impurity transport and no edge localized modes (ELMs). The regime has been demonstrated on the Alcator C-Mod, ASDEX Upgrade and DIII-D tokamaks, over a wide range of device parameters and pedestal conditions. Dimensionless parameters at the pedestal show overlap across devices and extend to low collisionality. When they are matched, pedestal temperature profiles are also similar. Pedestals are stable to peeling–ballooning modes, consistent with lack of ELMs. Access to I-mode is independent of heating method (neutral beam injection, ion cyclotron and/or electron cyclotron resonance heating). Normalized energy confinement H 98,y2 ≥ 1 has been achieved for a range of 3 ≤ q 95 ≤ 4.9 and scales favourably with power. Changes in turbulence in the pedestal region accompany the transition from L-mode to I-mode. The L–I threshold increases with plasma density and current, and with device size, but has a weak dependence on toroidal magnetic field B T. The upper limit of power for I-modes, which is set by I–H transitions, increases with B T and the power range is largest on Alcator C-Mod at B > 5 T. Issues for extrapolation to ITER and other future fusion devices are discussed., United States. Department of Energy (DE-FC02-99ER54512-CMOD), United States. Department of Energy (DE-SC0012469), United States. Department of Energy (DE-FC02-04ER54698), United States. Department of Energy (DE-FG02-94ER54235), United States. Department of Energy (DE-AC52-07NA27344), United States. Department of Energy (DE-AC02-09CH11466), United States. Department of Energy (DE-FG02-89ER53296), United States. Department of Energy (DE-FG02-08ER54999), United States. Department of Energy (DE-FG02-08ER54984)

Published
2017

10. The scaling of fuel recovered following un-mitigated disruptions in Alcator C-Mod with high-Z PFCs

Author

Massachusetts Institute of Technology. Plasma Science and Fusion Center, Lipschultz, Bruce, Whyte, Dennis G, Granetz, Robert S, Reinke, Matthew Logan, Wolfe, Stephen M, Loarte, A., Massachusetts Institute of Technology. Plasma Science and Fusion Center, Lipschultz, Bruce, Whyte, Dennis G, Granetz, Robert S, Reinke, Matthew Logan, Wolfe, Stephen M, and Loarte, A.

Abstract

United States. Department of Energy (DE-FC02-99ER54512)

Published
2017

11. Alcator C-Mod: research in support of ITER and steps beyond

Author

Massachusetts Institute of Technology. Department of Biological Engineering, Massachusetts Institute of Technology. Department of Mathematics, Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Department of Physics, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Hutchinson Ian, Baek, Seung Gyou, Marmar, Earl S, Barnard, Harold Salvadore, Bonoli, Paul T, Brunner, Daniel Frederic, Ennever, Paul Chappell, Fiore, Catherine L, Gao, Chi, Golfinopoulos, Theodore, Greenwald, Martin J, Hartwig, Zachary Seth, Hubbard, Amanda E, Hughes Jr, Jerry, Hutchinson, Ian Horner, Irby, James Henderson, Labombard, Brian, Lin, Yijun, Mumgaard, Robert Thomas, Parker, Ronald R, Porkolab, Miklos, Rice, John E, Shiraiwa, Shunichi, Sorbom, Brandon Nils, Terry, David Rankin, Terry, James L, Vieira, Rui F, Walk Jr, John R, Wallace, Gregory Marriner, White, Anne E., Whyte, Dennis G, Wolfe, Stephen M, Wright, John C, Wright, Graham, Wukitch, Stephen James, Xu, Peng, Cziegler, Istvan, Dekow, Gary L, Delgado-Aparicio, Luis, Lipschultz, Bruce, Theiler, Christian, Diallo, Ahmed Y, Edlund, Eric Matthias, Faust, Ian Charles, Candy, J., Canik, J., Churchill, R.M., Holland, C., Loarte, A., Reinke, M.L., Scott, S., Snyder, P., Theiler, C., Diallo, A., Edlund, E., LaBombard, B., Marmar, Earl S., Bonoli, Paul T., Fiore, Catherine, Greenwald, Martin J., Parker, R., Rice, John E., Wright, John C., Massachusetts Institute of Technology. Department of Biological Engineering, Massachusetts Institute of Technology. Department of Mathematics, Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Department of Physics, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Hutchinson Ian, Baek, Seung Gyou, Marmar, Earl S, Barnard, Harold Salvadore, Bonoli, Paul T, Brunner, Daniel Frederic, Ennever, Paul Chappell, Fiore, Catherine L, Gao, Chi, Golfinopoulos, Theodore, Greenwald, Martin J, Hartwig, Zachary Seth, Hubbard, Amanda E, Hughes Jr, Jerry, Hutchinson, Ian Horner, Irby, James Henderson, Labombard, Brian, Lin, Yijun, Mumgaard, Robert Thomas, Parker, Ronald R, Porkolab, Miklos, Rice, John E, Shiraiwa, Shunichi, Sorbom, Brandon Nils, Terry, David Rankin, Terry, James L, Vieira, Rui F, Walk Jr, John R, Wallace, Gregory Marriner, White, Anne E., Whyte, Dennis G, Wolfe, Stephen M, Wright, John C, Wright, Graham, Wukitch, Stephen James, Xu, Peng, Cziegler, Istvan, Dekow, Gary L, Delgado-Aparicio, Luis, Lipschultz, Bruce, Theiler, Christian, Diallo, Ahmed Y, Edlund, Eric Matthias, Faust, Ian Charles, Candy, J., Canik, J., Churchill, R.M., Holland, C., Loarte, A., Reinke, M.L., Scott, S., Snyder, P., Theiler, C., Diallo, A., Edlund, E., LaBombard, B., Marmar, Earl S., Bonoli, Paul T., Fiore, Catherine, Greenwald, Martin J., Parker, R., Rice, John E., and Wright, John C.

Abstract

This paper presents an overview of recent highlights from research on Alcator C-Mod. Significant progress has been made across all research areas over the last two years, with particular emphasis on divertor physics and power handling, plasma–material interaction studies, edge localized mode-suppressed pedestal dynamics, core transport and turbulence, and RF heating and current drive utilizing ion cyclotron and lower hybrid tools. Specific results of particular relevance to ITER include: inner wall SOL transport studies that have led, together with results from other experiments, to the change of the detailed shape of the inner wall in ITER; runaway electron studies showing that the critical electric field required for runaway generation is much higher than predicted from collisional theory; core tungsten impurity transport studies reveal that tungsten accumulation is naturally avoided in typical C-Mod conditions., United States. Department of Energy (DE-FC02-99ER54512-CMOD), United States. Department of Energy (DE-AC02-09CH11466), United States. Department of Energy (DE-FG02-96ER-54373), United States. Department of Energy (DE-FG02-94ER54235)

Published
2017

12. Investigation of the Thomson scattering-ECE discrepancy in ICRF heated plasmas at Alcator C-Mod

Author

Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Koch Institute for Integrative Cancer Research at MIT, White, Anne E., Hubbard, Amanda E., Hughes, Jerry W., Bonoli, Paul T., Bader, Andrew, Lin, Yijun, Ma, Y., Wolfe, Stephen M., Wukitch, Stephen James, Austin, M. E., Harvey, R. W., Reinke, M. L., Wolfe, Stephen M, Ma, Yunxing, Hubbard, Amanda E, Hughes Jr, Jerry, Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Koch Institute for Integrative Cancer Research at MIT, White, Anne E., Hubbard, Amanda E., Hughes, Jerry W., Bonoli, Paul T., Bader, Andrew, Lin, Yijun, Ma, Y., Wolfe, Stephen M., Wukitch, Stephen James, Austin, M. E., Harvey, R. W., Reinke, M. L., Wolfe, Stephen M, Ma, Yunxing, Hubbard, Amanda E, and Hughes Jr, Jerry

Abstract

This paper reports on new experiments at Alcator C-Mod that were performed in order to investigate the long-standing, unresolved discrepancy between Thomson scattering (TS) and electron cyclotron emission (ECE) measurements of electron temperature in high temperature tokamak plasmas. Ion cyclotron range of frequency (ICRF) heating is used to produce high temperature conditions where the type of TS-ECE discrepancy observed in the past at JET and TFTR should become observable. At Alcator C-Mod, plasmas with Te(0) up to 8 keV are obtained using ion cyclotron resonance heating (ICRH), ICRF mode conversion heating and a combination of the two heating methods in order to explore the hypothesis that the presence of ICRH-generated fast ions may be related to the discrepancy. In all high temperature cases, the TS and ECE measurements of electron temperature agree to within experimental uncertainties. We find no evidence for the type of discrepancy reported at JET and TFTR. These results show that the TS-ECE discrepancy does not depend on high temperatures alone and also that the presence of ICRH-generated fast ions is insufficient to cause the TS-ECE discrepancy., United States. Dept. of Energy (DE-FC02-99ER54512)

Published
2013

13. Scaling of the power exhaust channel in Alcator C-Mod

Author

Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Department of Physics, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Hutchinson, Ian H., Labombard, Brian, Terry, James L., Hughes, Jerry W., Brunner, Daniel Frederic, Payne, Joshua E., Reinke, Matthew Logan, Cziegler, Istvan, Granetz, Robert S., Greenwald, Martin J., Irby, James Henderson, Lin, Yijun, Lipschultz, Bruce, Ma, Yunxing, Marmar, Earl S., Tsujii, Naoto, Wallace, Gregory Marriner, Whyte, Dennis G., Wolfe, Stephen M., Wukitch, Stephen James, Rowan, W. L., Wurden, G., Hughes Jr, Jerry, Hutchinson, Ian Horner, Whyte, Dennis G, Wolfe, Stephen M, Terry, James L, Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Department of Physics, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Hutchinson, Ian H., Labombard, Brian, Terry, James L., Hughes, Jerry W., Brunner, Daniel Frederic, Payne, Joshua E., Reinke, Matthew Logan, Cziegler, Istvan, Granetz, Robert S., Greenwald, Martin J., Irby, James Henderson, Lin, Yijun, Lipschultz, Bruce, Ma, Yunxing, Marmar, Earl S., Tsujii, Naoto, Wallace, Gregory Marriner, Whyte, Dennis G., Wolfe, Stephen M., Wukitch, Stephen James, Rowan, W. L., Wurden, G., Hughes Jr, Jerry, Hutchinson, Ian Horner, Whyte, Dennis G, Wolfe, Stephen M, and Terry, James L

Abstract

Parametric dependences of the heat flux footprint on the outer divertor target plate are explored in EDA H-mode and ohmic L-mode plasmas over a wide range of parameters with attached plasma conditions. Heat flux profile shapes are found to be independent of toroidal field strength, independent of power flow along magnetic field lines and insensitive to x-point topology (single-null versus double-null). The magnitudes and widths closely follow that of the “upstream” pressure profile, which are correlated to plasma thermal energy content and plasma current. Heat flux decay lengths near the strike-point in H- and L-mode plasmas scale approximately with the inverse of plasma current, with a diminished dependence at high collisionality in L-mode. Consistent with previous studies, pressure gradients in the boundary scale with plasma current squared, holding the magnetohydrodynamic ballooning parameter approximately invariant at fixed collisionality—strong evidence that critical-gradient transport physics plays a key role in setting the power exhaust channel., United States. Dept. of Energy (Award DE-AC52-06NA25396), United States. Dept. of Energy (Coop. Agreement DE-FC02-99ER54512)

Published
2011

14. Observation of Self-Generated Flows in Tokamak Plasmas with Lower-Hybrid-Driven Current

Author

Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Department of Physics, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Hutchinson, Ian H., Rice, John E., Ince-Cushman, Alexander, Reinke, Matthew Logan, Greenwald, Martin J., Wallace, Gregory Marriner, Parker, Ronald R., Fiore, Catherine L., Hughes, Jerry W., Bonoli, Paul T., Shiraiwa, Shunichi, Hubbard, Amanda E., Wolfe, Stephen M., Marmar, Earl S., Bitter, M., Wilson, J., Hill, K., Parker, R., Fiore, Catherine, Hughes Jr, Jerry, Hubbard, Amanda E, Wolfe, Stephen M, Hutchinson, Ian Horner, Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Department of Physics, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Hutchinson, Ian H., Rice, John E., Ince-Cushman, Alexander, Reinke, Matthew Logan, Greenwald, Martin J., Wallace, Gregory Marriner, Parker, Ronald R., Fiore, Catherine L., Hughes, Jerry W., Bonoli, Paul T., Shiraiwa, Shunichi, Hubbard, Amanda E., Wolfe, Stephen M., Marmar, Earl S., Bitter, M., Wilson, J., Hill, K., Parker, R., Fiore, Catherine, Hughes Jr, Jerry, Hubbard, Amanda E, Wolfe, Stephen M, and Hutchinson, Ian Horner

Abstract

In Alcator C-Mod discharges lower hybrid waves have been shown to induce a countercurrent change in toroidal rotation of up to 60 km/s in the central region of the plasma (r/a~<0.4). This modification of the toroidal rotation profile develops on a time scale comparable to the current redistribution time (~100 ms) but longer than the energy and momentum confinement times (~20 ms). A comparison of the co- and countercurrent injected waves indicates that current drive (as opposed to heating) is responsible for the rotation profile modifications. Furthermore, the changes in central rotation velocity induced by lower hybrid current drive (LHCD) are well correlated with changes in normalized internal inductance. The application of LHCD has been shown to generate sheared rotation profiles and a negative increment in the radial electric field profile consistent with a fast electron pinch., U. S. Department of Energy (Contract No. DE-FC02- 99ER54512-CMOD)

Published
2010

15. Experimental vertical stability studies for ITER performance and design

Author

Hutchinson, Ian H., Wolfe, Stephen M., Ferrara, Marco, Humphreys, D. A., Casper, T. A., Eidietis, N., Gates, D. A., Jackson, G. L., Kolemen, E., Leuer, J. A., Lister, J., LoDestro, L. L., Meyer, W. H., Pearlstein, L. D., Portone, A., Sartori, F., Walker, M. L., Welander, A. S., Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Hutchinson, Ian H., Wolfe, Stephen M., and Ferrara, Marco

Abstract

Operating experimental devices have provided key inputs to the design process for ITER axisymmetric control. In particular, experiments have quantified controllability and robustness requirements in the presence of realistic noise and disturbance environments, which are difficult or impossible to characterize with modelling and simulation alone. This kind of information is particularly critical for ITER vertical control, which poses the highest demands on poloidal field system performance, since the consequences of loss of vertical control can be severe. This work describes results of multi-machine studies performed under a joint ITPA experiment (MDC-13) on fundamental vertical control performance and controllability limits. We present experimental results from Alcator C-Mod, DIII-D, NSTX, TCV and JET, along with analysis of these data to provide vertical control performance guidance to ITER. Useful metrics to quantify this control performance include the stability margin and maximum controllable vertical displacement. Theoretical analysis of the maximum controllable vertical displacement suggests effective approaches to improving performance in terms of this metric, with implications for ITER design modifications. Typical levels of noise in the vertical position measurement and several common disturbances which can challenge the vertical control loop are assessed and analysed., United States Department of Energy (DE-FC02-04ER54698, DEAC52- 07NA27344, and DE-FG02-04ER54235)

Published
2009

16. Non-local heat transport in Alcator C-Mod ohmic L-mode plasmas

Author

Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Department of Physics, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Gao, Chi, Rice, John E., Reinke, Matthew Logan, Howard, Nathaniel Thomas, Hubbard, Amanda E., Chilenski, Mark Alan, Walk Jr, John R., Hughes, Jerry W., Jr., Ennever, Paul Chappell, Porkolab, Miklos, White, Anne E., Sung, Choongki, Delgado-Aparicio, Luis, Baek, Seung Gyou, Rowan, William L., Greenwald, Martin J., Granetz, Robert S., Wolfe, Stephen M., Marmar, Earl S., Sun, H. J., Mikkelson, D., Brookman, M. W., Alcator C-Mod Team, Gao, Chi, Ph. D. Massachusetts Institute of Technology, Hughes, Jerry W., Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Department of Physics, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Gao, Chi, Rice, John E., Reinke, Matthew Logan, Howard, Nathaniel Thomas, Hubbard, Amanda E., Chilenski, Mark Alan, Walk Jr, John R., Hughes, Jerry W., Jr., Ennever, Paul Chappell, Porkolab, Miklos, White, Anne E., Sung, Choongki, Delgado-Aparicio, Luis, Baek, Seung Gyou, Rowan, William L., Greenwald, Martin J., Granetz, Robert S., Wolfe, Stephen M., Marmar, Earl S., Sun, H. J., Mikkelson, D., Brookman, M. W., Alcator C-Mod Team, Gao, Chi, Ph. D. Massachusetts Institute of Technology, and Hughes, Jerry W.

Abstract

Non-local heat transport experiments were performed in Alcator C-Mod ohmic L-mode plasmas by inducing edge cooling with laser blow-off impurity (CaF2) injection. The non-local effect, a cooling of the edge electron temperature with a rapid rise of the central electron temperature, which contradicts the assumption of 'local' transport, was observed in low collisionality linear ohmic confinement (LOC) regime plasmas. Transport analysis shows this phenomenon can be explained either by a fast drop of the core diffusivity, or the sudden appearance of a heat pinch. In high collisionality saturated ohmic confinement (SOC) regime plasmas, the thermal transport becomes 'local': the central electron temperature drops on the energy confinement time scale in response to the edge cooling. Measurements from a high resolution imaging x-ray spectrometer show that the ion temperature has a similar behaviour as the electron temperature in response to edge cooling, and that the transition density of non-locality correlates with the rotation reversal critical density. This connection may indicate the possible connection between thermal and momentum transport, which is also linked to a transition in turbulence dominance between trapped electron modes (TEMs) and ion temperature gradient (ITG) modes. Experiments with repetitive cold pulses in one discharge were also performed to allow Fourier analysis and to provide details of cold front propagation. These modulation experiments showed in LOC plasmas that the electron thermal transport is not purely diffusive, while in SOC the electron thermal transport is more diffusive like. Linear gyrokinetic simulations suggest the turbulence outside r/a = 0.75 changes from TEM dominance in LOC plasmas to ITG mode dominance in SOC plasmas., United States. Dept. of Energy (DoE Contract No DE-FC02-99ER54512), Oak Ridge Institute for Science and Education (DOE Fusion Energy Postdoctoral Research Program)

Published
2015

17. Non-local heat transport in Alcator C-Mod ohmic L-mode plasmas

Author

Gao, Chi, Rice, John E., Sun, H. J., Reinke, Matthew Logan, Howard, Nathaniel Thomas, Mikkelson, D., Hubbard, Amanda E., Chilenski, Mark Alan, Walk Jr, John R., Hughes, Jerry W., Jr., Ennever, Paul Chappell, Porkolab, Miklos, White, Anne E., Sung, Choongki, Delgado-Aparicio, Luis, Baek, Seung Gyou, Rowan, William L., Brookman, M. W., Greenwald, Martin J., Granetz, Robert S., Wolfe, Stephen M., Marmar, Earl S., Alcator C-Mod Team, Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Department of Physics, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Gao, Chi, Rice, John E., Reinke, Matthew Logan, Howard, Nathaniel Thomas, Hubbard, Amanda E., Chilenski, Mark Alan, Walk Jr, John R., Hughes, Jerry W., Jr., Ennever, Paul Chappell, Porkolab, Miklos, White, Anne E., Sung, Choongki, Delgado-Aparicio, Luis, Baek, Seung Gyou, Rowan, William L., Greenwald, Martin J., Granetz, Robert S., Wolfe, Stephen M., and Marmar, Earl S.

Subjects
Nuclear and High Energy Physics, Materials science, Alcator C-Mod, Physics::Plasma Physics, Pinch, Electron temperature, Plasma, Electron, Collisionality, Atomic physics, Condensed Matter Physics, Thermal diffusivity, Ohmic contact
Abstract

Non-local heat transport experiments were performed in Alcator C-Mod ohmic L-mode plasmas by inducing edge cooling with laser blow-off impurity (CaF2) injection. The non-local effect, a cooling of the edge electron temperature with a rapid rise of the central electron temperature, which contradicts the assumption of 'local' transport, was observed in low collisionality linear ohmic confinement (LOC) regime plasmas. Transport analysis shows this phenomenon can be explained either by a fast drop of the core diffusivity, or the sudden appearance of a heat pinch. In high collisionality saturated ohmic confinement (SOC) regime plasmas, the thermal transport becomes 'local': the central electron temperature drops on the energy confinement time scale in response to the edge cooling. Measurements from a high resolution imaging x-ray spectrometer show that the ion temperature has a similar behaviour as the electron temperature in response to edge cooling, and that the transition density of non-locality correlates with the rotation reversal critical density. This connection may indicate the possible connection between thermal and momentum transport, which is also linked to a transition in turbulence dominance between trapped electron modes (TEMs) and ion temperature gradient (ITG) modes. Experiments with repetitive cold pulses in one discharge were also performed to allow Fourier analysis and to provide details of cold front propagation. These modulation experiments showed in LOC plasmas that the electron thermal transport is not purely diffusive, while in SOC the electron thermal transport is more diffusive like. Linear gyrokinetic simulations suggest the turbulence outside r/a = 0.75 changes from TEM dominance in LOC plasmas to ITG mode dominance in SOC plasmas., United States. Dept. of Energy (DoE Contract No DE-FC02-99ER54512), Oak Ridge Institute for Science and Education (DOE Fusion Energy Postdoctoral Research Program)

Published
2014

18. Ohmic energy confinement saturation and core toroidal rotation reversal in Alcator C-Mod plasmas

Author

Massachusetts Institute of Technology. Department of Physics, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Porkolab, Miklos, Rice, John E., Greenwald, Martin J., Podpaly, Y. A., Reinke, Matthew Logan, Hughes, Jerry W., Howard, Nathaniel Thomas, Ma, Y., Cziegler, Istvan, Ennever, Paul Chappell, Ernst, Darin R., Fiore, Catherine L., Gao, Chi, Irby, James Henderson, Marmar, Earl S., Tsujii, Naoto, Wolfe, Stephen M., Diamond, P. H., Duval, B. P., Massachusetts Institute of Technology. Department of Physics, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Porkolab, Miklos, Rice, John E., Greenwald, Martin J., Podpaly, Y. A., Reinke, Matthew Logan, Hughes, Jerry W., Howard, Nathaniel Thomas, Ma, Y., Cziegler, Istvan, Ennever, Paul Chappell, Ernst, Darin R., Fiore, Catherine L., Gao, Chi, Irby, James Henderson, Marmar, Earl S., Tsujii, Naoto, Wolfe, Stephen M., Diamond, P. H., and Duval, B. P.

Abstract

Ohmic energy confinement saturation is found to be closely related to core toroidal rotation reversals in Alcator C-Mod tokamak plasmas. Rotation reversals occur at a critical density, depending on the plasma current and toroidal magnetic field, which coincides with the density separating the linear Ohmic confinement regime from the saturated Ohmic confinement regime. The rotation is directed co-current at low density and abruptly changes direction to counter-current when the energy confinement saturates as the density is increased. Since there is a bifurcation in the direction of the rotation at this critical density, toroidal rotation reversal is a very sensitive indicator in the determination of the regime change. The reversal and confinement saturation results can be unified, since these processes occur in a particular range of the collisionality., United States. Dept. of Energy (Contract DE-FC02-99ER54512)

Published
2013

19. Rotation Reversal Bifurcation and Energy Confinement Saturation in Tokamak Ohmic L-Mode Plasmas

Author

Massachusetts Institute of Technology. Plasma Science and Fusion Center, Porkolab, Miklos, Driscoll, John E., Cziegler, Istvan, Diamond, P. H., Duval, B. P., Podpaly, Yuri A., Reinke, Matthew Logan, Ennever, Paul Chappell, Greenwald, Martin J., Hughes, Jerry W., Ma, Y., Marmar, Earl S., Tsujii, Naoto, Wolfe, Stephen M., Rice, John E., Massachusetts Institute of Technology. Plasma Science and Fusion Center, Porkolab, Miklos, Driscoll, John E., Cziegler, Istvan, Diamond, P. H., Duval, B. P., Podpaly, Yuri A., Reinke, Matthew Logan, Ennever, Paul Chappell, Greenwald, Martin J., Hughes, Jerry W., Ma, Y., Marmar, Earl S., Tsujii, Naoto, Wolfe, Stephen M., and Rice, John E.

Abstract

Direction reversals of intrinsic toroidal rotation have been observed in diverted Alcator C-Mod Ohmic L-mode plasmas following electron density ramps. For low density discharges, the core rotation is directed cocurrent, and reverses to countercurrent following an increase in the density above a certain threshold. Such reversals occur together with a decrease in density fluctuations with 2 cm[superscript -1]≤k[subscript θ]≤11 cm[superscript -1] and frequencies above 70 kHz. There is a strong correlation between the reversal density and the density at which the Ohmic L-mode energy confinement changes from the linear to the saturated regime., United States. Dept. of Energy (Contract No. DE-FC02-99ER54512)

Published
2012

20. Experimental vertical stability studies for ITER performance and design

Author

Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Hutchinson, Ian H., Wolfe, Stephen M., Ferrara, Marco, Humphreys, D. A., Casper, T. A., Eidietis, N., Gates, D. A., Jackson, G. L., Kolemen, E., Leuer, J. A., Lister, J., LoDestro, L. L., Meyer, W. H., Pearlstein, L. D., Portone, A., Sartori, F., Walker, M. L., Welander, A. S., Ferrara, Marco, Ph. D. Massachusetts Institute of Technology, Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Hutchinson, Ian H., Wolfe, Stephen M., Ferrara, Marco, Humphreys, D. A., Casper, T. A., Eidietis, N., Gates, D. A., Jackson, G. L., Kolemen, E., Leuer, J. A., Lister, J., LoDestro, L. L., Meyer, W. H., Pearlstein, L. D., Portone, A., Sartori, F., Walker, M. L., Welander, A. S., and Ferrara, Marco, Ph. D. Massachusetts Institute of Technology

Abstract

Operating experimental devices have provided key inputs to the design process for ITER axisymmetric control. In particular, experiments have quantified controllability and robustness requirements in the presence of realistic noise and disturbance environments, which are difficult or impossible to characterize with modelling and simulation alone. This kind of information is particularly critical for ITER vertical control, which poses the highest demands on poloidal field system performance, since the consequences of loss of vertical control can be severe. This work describes results of multi-machine studies performed under a joint ITPA experiment (MDC-13) on fundamental vertical control performance and controllability limits. We present experimental results from Alcator C-Mod, DIII-D, NSTX, TCV and JET, along with analysis of these data to provide vertical control performance guidance to ITER. Useful metrics to quantify this control performance include the stability margin and maximum controllable vertical displacement. Theoretical analysis of the maximum controllable vertical displacement suggests effective approaches to improving performance in terms of this metric, with implications for ITER design modifications. Typical levels of noise in the vertical position measurement and several common disturbances which can challenge the vertical control loop are assessed and analysed., United States Department of Energy (DE-FC02-04ER54698, DEAC52- 07NA27344, and DE-FG02-04ER54235)

Published
2010

22. Remote Control of Alcator C-Mod from Lawrence Livermore National Laboratory

Author

Horne, Steve F., primary, Greenwald, Martin, additional, Fredian, Tom W., additional, Hutchinson, Ian H., additional, Labombard, Brian Louis, additional, Stillerman, Josh, additional, Takase, Yuichi, additional, Wolfe, Stephen M., additional, Casper, Thomas A., additional, Butner, David N., additional, Meyer, William H., additional, and Moller, Jeffrey M., additional

Published
1997
Full Text
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26. Authors

Author

Tinios, Gerasimos, primary, Horne, Steve F., additional, Hutchinson, Ian H., additional, Wolfe, Stephen M., additional, Tsuji, Yasumasa, additional, Murakami, Yoshiki, additional, Sugihara, Masayoshi, additional, van Haren, Paul C., additional, Oomens, Noud A., additional, Chubb, Scott R., additional, Chubb, Talbot A., additional, Elawadly, Khalil M., additional, Blanchard, James P., additional, Silver, David S., additional, Dash, John, additional, and Keefe, Patrick S., additional

Published
1993
Full Text
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27. CHRONICLES OF A FINANCIAL CRISIS: CAUSES AND ETHICAL DIMENSIONS.

Author

Wolfe, Regina Wentzel and Wolfe, Stephen M.

Subjects
FINANCIAL crises, BUSINESS cycles, BUSINESS ethics, STUDENTS, PROFESSIONAL education
Abstract

The article reports on the need to include ethics in business education to deal with challenges of financial crisis. It is said that understanding the intricacies of financial crisis depends on recognizing the complexity of the crisis and its causes and on acknowledging that those involved include individuals from a broad spectrum of society. Engaging students in examination ethical dimensions of the financial crisis can assist in furthering these learning goals.

Published
2012

29. High-field side scrape-off layer investigation: Plasma profiles and impurity screening behavior in near-double-null configurations

Author

S.M. Wolfe, G.M. Wallace, D.G. Whyte, Robert Mumgaard, Dan Brunner, Jerry Hughes, Brian LaBombard, Adam Kuang, S.J. Wukitch, J.R. Walk, J.L. Terry, Yuxuan Lin, M. Chilenski, Matthew Reinke, Earl Marmar, Ian Faust, Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Labombard, Brian, Kuang, Adam QingYang, Brunner, Daniel Frederic, Faust, Ian Charles, Walk Jr, John R, Chilenski, Mark Alan, Lin, Ya, Marmar, Earl S, Wallace, Gregory Marriner, Whyte, Dennis G, Wolfe, Stephen M, and Wukitch, Stephen James

Subjects
Nuclear and High Energy Physics, Tokamak, Field (physics), Materials Science (miscellaneous), Analytical chemistry, 01 natural sciences, Molecular physics, 010305 fluids & plasmas, law.invention, Alcator C-Mod, Impurity, law, Double null, 0103 physical sciences, Impurity screening, 010306 general physics, Null (radio), Chemistry, Divertor, Plasma, lcsh:TK9001-9401, Nuclear Energy and Engineering, High field side scrape-off layer, lcsh:Nuclear engineering. Atomic power, Antenna (radio)
Abstract

New experiments on Alcator C-Mod reveal that the favorable impurity screening characteristics of the high-field side (HFS) scrape-off layer (SOL), previously reported for single null geometries, is retained in double null configurations, despite the formation of an extremely thin SOL. In balanced double-null, nitrogen injected locally into the HFS SOL is better screened by a factor of 2.5 compared to the same injection into the low field side (LFS) SOL. This result is insensitive to plasma current and Greenwald fraction. Nitrogen injected into the HFS SOL is not as well screened (only a factor of 1.5 improvement over LFS) in unbalanced double-null discharges, when the primary divertor is in the direction of B×∇B. In this configuration, impurity ‘plume’ emission patterns indicate that an opposing E × B drift competes with the parallel impurity flow to the divertor. In balanced double-null plasmas, the dispersal pattern exhibits a dominant E × B motion. Unbalanced discharges with the primary divertor opposite the direction of B×∇B exhibit excellent HFS screening characteristics – a factor of 5 enhancement compared to LFS. These data support the idea that future tokamaks should locate all RF actuators and close-fitting wall structures on the HFS and employ near-double-null magnetic topologies, both to precisely control plasma conditions at the antenna/plasma interface and to maximally mitigate the impact of local impurity sources arising from plasma-material interactions. Keywords: Alcator C-Mod; Impurity screening; Double null; High field side scrape-off layer, United States. Department of Energy (Contract DE-FC02-99ER54512)

Published
2017

30. Multi-device studies of pedestal physics and confinement in the I-mode regime

Author

Jerry Hughes, A. Loarte, T.H. Osborne, L. W. Schmitz, George McKee, Alessandro Marinoni, D.G. Whyte, E. Wolfrum, E. Viezzer, Istvan Cziegler, R. M. McDermott, S.P. Gerhardt, Zheng Yan, M.E. Fenstermacher, L. Barrera Orte, Amanda Hubbard, F. Ryter, J. E. Rice, R. Maingi, P. Gohil, T. L. Rhodes, R. Fischer, Randy Michael Churchill, J.R. Walk, S.M. Wolfe, Max E Austin, P. Manz, T. Happel, Anne White, Earl Marmar, R. J. Groebner, Christian Theiler, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Whyte, Dennis, Hubbard, Amanda E, Hughes Jr, Jerry, Marinoni, Alessandro, Marmar, Earl S, Rice, John E, Walk Jr, John R, Whyte, Dennis G, Wolfe, Stephen M, Alcator C-Mod Team, ASDEX Upgrade Team, Max Planck Institute for Plasma Physics, Max Planck Society, and DIII-D Team

Subjects
Physics, Nuclear and High Energy Physics, Tokamak, Cyclotron, Collisionality, Condensed Matter Physics, 01 natural sciences, Neutral beam injection, Electron cyclotron resonance, 010305 fluids & plasmas, law.invention, Pedestal, ASDEX Upgrade, law, Physics::Plasma Physics, 0103 physical sciences, Atomic physics, 010306 general physics, Dimensionless quantity
Abstract

This paper describes joint ITPA studies of the I-mode regime, which features an edge thermal barrier together with L-mode-like particle and impurity transport and no edge localized modes (ELMs). The regime has been demonstrated on the Alcator C-Mod, ASDEX Upgrade and DIII-D tokamaks, over a wide range of device parameters and pedestal conditions. Dimensionless parameters at the pedestal show overlap across devices and extend to low collisionality. When they are matched, pedestal temperature profiles are also similar. Pedestals are stable to peeling–ballooning modes, consistent with lack of ELMs. Access to I-mode is independent of heating method (neutral beam injection, ion cyclotron and/or electron cyclotron resonance heating). Normalized energy confinement H 98,y2 ≥ 1 has been achieved for a range of 3 ≤ q 95 ≤ 4.9 and scales favourably with power. Changes in turbulence in the pedestal region accompany the transition from L-mode to I-mode. The L–I threshold increases with plasma density and current, and with device size, but has a weak dependence on toroidal magnetic field B T. The upper limit of power for I-modes, which is set by I–H transitions, increases with B T and the power range is largest on Alcator C-Mod at B > 5 T. Issues for extrapolation to ITER and other future fusion devices are discussed., United States. Department of Energy (DE-FC02-99ER54512-CMOD), United States. Department of Energy (DE-SC0012469), United States. Department of Energy (DE-FC02-04ER54698), United States. Department of Energy (DE-FG02-94ER54235), United States. Department of Energy (DE-AC52-07NA27344), United States. Department of Energy (DE-AC02-09CH11466), United States. Department of Energy (DE-FG02-89ER53296), United States. Department of Energy (DE-FG02-08ER54999), United States. Department of Energy (DE-FG02-08ER54984)

Published
2016

31. The scaling of fuel recovered following un-mitigated disruptions in Alcator C-Mod with high-Z PFCs

Author

Bruce Lipschultz, S.M. Wolfe, D.G. Whyte, A. Loarte, Matthew Reinke, Robert Granetz, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Lipschultz, Bruce, Whyte, Dennis G, Granetz, Robert S, Reinke, Matthew Logan, and Wolfe, Stephen M

Subjects
Nuclear and High Energy Physics, Materials science, Magnetic energy, business.industry, Nuclear engineering, Analytical chemistry, chemistry.chemical_element, Plasma, Tungsten, Nuclear Energy and Engineering, Alcator C-Mod, chemistry, Thermal, General Materials Science, Current (fluid), business, Scaling, Thermal energy
Abstract

The retention of fuel in plasma facing components (PFCs) is important for the viability of fusion – both in terms of economics and safety. This study shows that a single, un-mitigated, disruption can remove >30× more fuel than that retained in a single, 1s, C-Mod discharge with molybdenum and tungsten PFCs. The fuel is recovered due to heating of the near-surface (∼100 μm) during the thermal and current quench periods of the disruption. A regression analysis of full-current disruptions in a dataset of 3200 discharges leads to a scaling of fuel recovered approximately proportional to W TH 1 × W MAG 2 where WTH and WMAG are the thermal and poloidal magnetic energy inside the vessel respectively. Scaling by surface area and disruption time scales to ITER indicate 5–10 MA plasmas with low thermal energy (e.g. during current rampdown) may be ideal for removing fuel from plasma-wetted surfaces.

Published
2011

32. Core impurity transport in Alcator C-Mod L-, I- and H-mode plasmas

Author

Martin Greenwald, Robert Mumgaard, Amanda Hubbard, S.M. Wolfe, S.J. Wukitch, J.L. Terry, Anne White, Nathan Howard, L. F. Delgado-Aparicio, C. Gao, Earl Marmar, D.G. Whyte, J. H. Irby, M. Chilenski, Yu-Ming Lin, S. D. Scott, Jerry Hughes, J.R. Walk, John Rice, Matthew Reinke, Robert Granetz, Massachusetts Institute of Technology. Department of Physics, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Whyte Dennis, Rice, John E, Gao, Chi, Howard, Nathaniel Thomas, Chilenski, Mark Alan, Granetz, Robert S, Greenwald, Martin J, Hubbard, Amanda E, Hughes Jr, Jerry, Irby, James Henderson, Lin, Yijun, Marmar, Earl S, Mumgaard, Robert Thomas, Terry, James L, Walk Jr, John R, White, Anne E., Whyte, Dennis G, Wolfe, Stephen M, and Wukitch, Stephen James

Subjects
Convection, Nuclear and High Energy Physics, Materials science, Cyclotron, Plasma, Condensed Matter::Mesoscopic Systems and Quantum Hall Effect, Condensed Matter Physics, law.invention, Ion, Amplitude, Alcator C-Mod, law, Impurity, Physics::Plasma Physics, Electron temperature, Atomic physics
Abstract

Core impurity transport has been investigated for a variety of confinement regimes in Alcator C-Mod plasmas from x-ray emission following injection of medium and high Z materials. In ohmic L-mode discharges, impurity transport is anomalous (D[subscript eff] ≫ D[subscript nc]) and changes very little across the LOC/SOC boundary. In ion cyclotron range of frequencies (ICRF) heated L-mode plasmas, the core impurity confinement time decreases with increasing ICRF input power (and subsequent increasing electron temperature) and increases with plasma current. Nearly identical impurity confinement characteristics are observed in I-mode plasmas. In enhanced D[subscript α] H-mode discharges the core impurity confinement times are much longer. There is a strong connection between core impurity confinement time and the edge density gradient across all confinement regimes studied here. Deduced central impurity density profiles in stationary plasmas are generally flat, in spite of large amplitude sawtooth oscillations, and there is little evidence of impurity convection inside of r/a = 0.3 when averaged over sawteeth., United States. Department of Energy (Contract DE-FC02-99ER54512), United States. Dept. of Energy. Fusion Energy Postdoctoral Research Program (Oak Ridge Institute for Science and Education)

Published
2014

33. 20 years of research on the Alcator C-Mod tokamaka)

Author

Istvan Cziegler, R. M. McDermott, John Goetz, R.F. Vieira, Robert Granetz, Amanda Hubbard, S. Horne, Ian H. Hutchinson, Nathan Howard, C. K. Li, Robert Mumgaard, E. Edlund, Arturo Dominguez, A. Tronchin-James, Paul Ennever, Theodore Golfinopoulos, C. Gao, John Rice, J. H. Irby, S. Pitcher, Thomas W. Fredian, James Myra, R.R. Parker, N. Smick, Stewart Zweben, D. R. Mikkelsen, Bruce Lipschultz, Olaf Grulke, W. Bergerson, D. Terry, Aaron Bader, D.G. Whyte, V.A. Izzo, Yuichi Takase, Z.S. Hartwig, Brian LaBombard, Harold Barnard, James R. Wilson, W. Burke, S.J. Wukitch, Vincent Tang, G. McCracken, D.R. Ernst, J. M. Sierchio, G.M. Olynyk, Igor Bespamyatnov, W. Beck, C.L. Fiore, Christian Theiler, Jeff Candy, Joshua Stillerman, Dan Brunner, S.M. Wolfe, P.T. Bonoli, Jerry Hughes, A. Loarte, Andrea Schmidt, Choongki Sung, B. P. Duval, John Wright, Odd Erik Garcia, Gregory Wallace, Mohammad Reza Bakhtiari, D. L. Brower, R. Ochoukov, Ian Faust, S. Shiraiwa, A. Mazurenko, Earl Marmar, W. L. Rowan, Anne White, Ahmed Diallo, D. A. Mossessian, Miklos Porkolab, J.L. Terry, C.E. Kessel, Naoto Tsujii, P. B. Snyder, G.M. Wright, J. A. Snipes, Seung Gyou Baek, E. Nelson-Melby, Martin Greenwald, Yuri Podpaly, Brandon Sorbom, Yu-Ming Lin, Cornwall Lau, Matthew Reinke, Orso Meneghini, J.R. Walk, S. D. Scott, M. Churchill, Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Department of Physics, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Greenwald, Martin J., Baek, Seung Gyou, Barnard, Harold, Beck, William K., Bonoli, Paul T., Brunner, Daniel Frederic, Burke, William M., Ennever, Paul Chappell, Ernst, Darin R., Faust, Ian Charles, Fiore, Catherine, Fredian, Thomas W., Gao, Chi, Golfinopoulos, Theodore, Granetz, Robert S., Hartwig, Zachary, Hubbard, Amanda E., Hughes, Jerry W., Jr., Hutchinson, Ian H., Irby, James Henderson, Labombard, Brian, Li, Chikang, Lin, Yijun, Marmar, Earl S., Mumgaard, Robert Thomas, Parker, Ronald R., Porkolab, Miklos, Rice, John E., Shiraiwa, Shunichi, Sierchio, Jennifer M., Sorbom, Brandon Nils, Stillerman, Joshua A., Sung, Choongki, Terry, David Rankin, Terry, James L., Vieira, Rui F., Walk, John R., Jr., Wallace, Gregory Marriner, White, Anne E., Whyte, Dennis G., Wolfe, Stephen M., Wright, Graham, Wright, John C., and Wukitch, Stephen James

Subjects
Physics, Tokamak, VDP::Mathematics and natural science: 400::Physics: 430::Space and plasma physics: 437, Divertor, Nuclear engineering, Cyclotron, Context (language use), Fusion power, Condensed Matter Physics, 01 natural sciences, 010305 fluids & plasmas, law.invention, Alcator C-Mod, Physics::Plasma Physics, law, VDP::Matematikk og Naturvitenskap: 400::Fysikk: 430::Rom- og plasmafysikk: 437, 0103 physical sciences, Plasma diagnostics, Radio frequency, Atomic physics, 010306 general physics
Abstract

The object of this review is to summarize the achievements of research on the Alcator C-Mod tokamak [Hutchinson et al., Phys. Plasmas 1, 1511 (1994) and Marmar, Fusion Sci. Technol. 51, 261 (2007)] and to place that research in the context of the quest for practical fusion energy. C-Mod is a compact, high-field tokamak, whose unique design and operating parameters have produced a wealth of new and important results since it began operation in 1993, contributing data that extends tests of critical physical models into new parameter ranges and into new regimes. Using only high-power radio frequency (RF) waves for heating and current drive with innovative launching structures, C-Mod operates routinely at reactor level power densities and achieves plasma pressures higher than any other toroidal confinement device. C-Mod spearheaded the development of the vertical-target divertor and has always operated with high-Z metal plasma facing components—approaches subsequently adopted for ITER. C-Mod has made ground-breaking discoveries in divertor physics and plasma-material interactions at reactor-like power and particle fluxes and elucidated the critical role of cross-field transport in divertor operation, edge flows and the tokamak density limit. C-Mod developed the I-mode and the Enhanced Dα H-mode regimes, which have high performance without large edge localized modes and with pedestal transport self-regulated by short-wavelength electromagnetic waves. C-Mod has carried out pioneering studies of intrinsic rotation and demonstrated that self-generated flow shear can be strong enough in some cases to significantly modify transport. C-Mod made the first quantitative link between the pedestal temperature and the H-mode's performance, showing that the observed self-similar temperature profiles were consistent with critical-gradient-length theories and followed up with quantitative tests of nonlinear gyrokinetic models. RF research highlights include direct experimental observation of ion cyclotron range of frequency (ICRF) mode-conversion, ICRF flow drive, demonstration of lower-hybrid current drive at ITER-like densities and fields and, using a set of novel diagnostics, extensive validation of advanced RF codes. Disruption studies on C-Mod provided the first observation of non-axisymmetric halo currents and non-axisymmetric radiation in mitigated disruptions. A summary of important achievements and discoveries are included., United States. Dept. of Energy (Cooperative Agreement DE-FC02-99ER54512), United States. Dept. of Energy (Cooperative Agreement DE-FG03-94ER-54241), United States. Dept. of Energy (Cooperative Agreement DE-AC02-78ET- 51013), United States. Dept. of Energy (Cooperative Agreement DE-AC02-09CH11466), United States. Dept. of Energy (Cooperative Agreement DE-FG02-95ER54309), United States. Dept. of Energy (Cooperative Agreement DE-AC02-05CH11231), United States. Dept. of Energy (Cooperative Agreement DE-AC52-07NA27344), United States. Dept. of Energy (Cooperative Agreement DE-FG02- 97ER54392), United States. Dept. of Energy (Cooperative Agreement DE-SC00-02060)

Published
2014

34. External excitation of a short-wavelength fluctuation in the Alcator C-Mod edge plasma and its relationship to the quasi-coherent mode

Author

R.F. Vieira, E. M. Davis, R. Leccacorvi, William M. Parkin, Martin Greenwald, J.L. Terry, R.R. Parker, Brian LaBombard, Earl Marmar, Theodore Golfinopoulos, W. Burke, S.M. Wolfe, Miklos Porkolab, J. H. Irby, Robert Granetz, Massachusetts Institute of Technology. Department of Physics, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Golfinopoulos, Theodore, Labombard, Brian, Parker, R. R., Burke, William M., Davis, E., Granetz, Robert S., Greenwald, Martin J., Irby, James Henderson, Leccacorvi, Rick, Marmar, Earl S., Parkin, William C., Porkolab, Miklos, Terry, James L., Vieira, Rui F., and Wolfe, Stephen M.

Subjects
Physics, Wavelength, Tokamak, Alcator C-Mod, law, Field line, Resonance, Quartz crystal microbalance, Atomic physics, Antenna (radio), Condensed Matter Physics, Excitation, law.invention
Abstract

A novel “Shoelace” antenna has been used to inductively excite a short-wavelength edge fluctuation in a tokamak boundary layer for the first time. The principal design parameters, k[subscript ⊥] = 1.5 ± 0.1 cm[superscript −1] and 45 < f < 300 kHz, match the Quasi-Coherent Mode (QCM, k[subscript ⊥] ∼ 1.5 cm[superscript −1], f ∼ 50−150 kHz) in Alcator C-Mod, responsible for exhausting impurities in the steady-state, ELM-free Enhanced D[subscript α] H-mode. In H-mode, whether or not there is a QCM, the antenna drives coherent, field-aligned perturbations in density, [˜ over n][subscript e], and field, [˜ over B][subscript θ], which are guided by field lines, propagate in the electron diamagnetic drift direction, and exhibit a weakly damped (γ/ω[subscript 0] ∼ 5%−10%) resonance near the natural QCM frequency. This result is significant, offering the possibility that externally driven modes may be used to enhance particle transport. In L-mode, the antenna drives only a non-resonant [˜ over B][subscript θ] response. The facts that the driven mode has the same wave number and propagation direction as the QCM, and is resonant at the QCM frequency, suggest the antenna may couple to this mode, which we have shown elsewhere to be predominantly drift-mode-like [B. LaBombard et al., Phys. Plasmas 21, 056108 (2014)]., United States. Dept. of Energy (Cooperative Agreement DE-FC02-99ER54512)

Published
2014

35. Investigation of the Thomson scattering-ECE discrepancy in ICRF heated plasmas at Alcator C-Mod

Author

S.J. Wukitch, M. L. Reinke, Amanda Hubbard, R. W. Harvey, Ye Ma, Anne White, Yuxuan Lin, A. Bader, Max E Austin, P.T. Bonoli, Jerry Hughes, S.M. Wolfe, Massachusetts Institute of Technology. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Koch Institute for Integrative Cancer Research at MIT, White, Anne E., Hubbard, Amanda E., Hughes, Jerry W., Bonoli, Paul T., Bader, Andrew, Lin, Yijun, Ma, Y., Wolfe, Stephen M., and Wukitch, Stephen James

Subjects
Nuclear and High Energy Physics, Tokamak, Materials science, Thomson scattering, Cyclotron, Electron, Condensed Matter Physics, law.invention, Ion, Alcator C-Mod, law, Electron temperature, Atomic physics, Ion cyclotron resonance
Abstract

This paper reports on new experiments at Alcator C-Mod that were performed in order to investigate the long-standing, unresolved discrepancy between Thomson scattering (TS) and electron cyclotron emission (ECE) measurements of electron temperature in high temperature tokamak plasmas. Ion cyclotron range of frequency (ICRF) heating is used to produce high temperature conditions where the type of TS-ECE discrepancy observed in the past at JET and TFTR should become observable. At Alcator C-Mod, plasmas with Te(0) up to 8 keV are obtained using ion cyclotron resonance heating (ICRH), ICRF mode conversion heating and a combination of the two heating methods in order to explore the hypothesis that the presence of ICRH-generated fast ions may be related to the discrepancy. In all high temperature cases, the TS and ECE measurements of electron temperature agree to within experimental uncertainties. We find no evidence for the type of discrepancy reported at JET and TFTR. These results show that the TS-ECE discrepancy does not depend on high temperatures alone and also that the presence of ICRH-generated fast ions is insufficient to cause the TS-ECE discrepancy., United States. Dept. of Energy (DE-FC02-99ER54512)

Published
2012

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