Dennis whyte

Whyte received a national grant from the Canadian government as a post-doc which encouraged him to go outside Canada to gain experience. Canada then cancelled their fusion program, so Whyte stayed in the United States.

Becoming a teacher made Whyte a better researcher. The exercise of explaining the fundamentals to students led to ideas and turned into big projects. Whyte spent four years at the University of Wisconsin, but he missed being in a bigger team and working on the applied part of research. Whyte has been at MIT for 12 years. Because of the expertise present, they had the ability to make magnetic fields that were much stronger than other laboratories were considering.

By some basic arguments, they made the device smaller, which became Alcator. The focus of the program was education and training. It was solely funded through the Department of Energy and the program stopped a couple years ago. On the last day of its operation, it set a world record for fusion performance by surpassing 2 atmospheres of pressure in a plasma that was significantly hotter than the center of the sun.

Doubling the pressure seen in other devices quadruples the energy density, making it more economical. Magnetic fields exert a magnetostatic pressure that is counteracting or containing the plasma. Nothing physically contacts the plasma, otherwise the plasma would become cold.

Hubbard, J. Hughes, D. Mikkelsen, F. Parra, M. Reinke, C. Sung, J. Walk and D. Walk, J. Hughes, A. Terry, D. Whyte, A. White, S. Baek, M. Theiler, R. Churchill, J. Rice, P. Snyder, T. Osborne, A. Dominguez and I. Wright, H.

Barnard, L. Kesler, E. Peterson, P. Stahle, R. Sullivan, D. Whyte and K. Ochoukov, D. Whyte, D. Brunner, D. D'Ippolito, B. LaBombard, B. Lipschultz, J.

Myra, J. Terry and S. Cooper, J. Wallace, M. Candidate asymmetry drivers are explored, showing that neither non-uniform impurity sources nor localized fluctuation-driven transport are able to explain satisfactorily the impurity density asymmetry. Since impurity density asymmetries are only present in plasmas with strong electron density gradients, and radial transport timescales become comparable to parallel transport timescales in the pedestal region, it is suggested that global transport effects relating to the strong electron density gradients in the pedestal are the main driver for the pedestal in-out impurity density asymmetry.

In density ramp experiments in Alcator C-Mod and other machines the onset of PDI activity has been well correlated with a decrease in current drive efficiency and production of fast electron bremsstrahlung.

However whether PDI is the primary cause of the 'density limit', and if so by exactly what mechanism beyond the obvious one of pump depletion has not been clearly established. In order to further understand the connection, the frequency spectrum of PDI activity occurring during Alcator C-Mod LHCD experiments has been explored in detail by means of a number of RF probes distributed around the periphery of the C-Mod tokamak including a probe imbedded in the inner wall.

The results show that i the excited spectra consists mainly of a few discrete ion cyclotron IC quasi-modes, which have higher growth than the ion sound branch; ii PDI activity can begin either at the inner or outer wall, depending on magnetic configuration; iii the frequencies of the IC quasi-modes correspond to the magnetic field strength close to the low-field side LFS or high-field side separatrix; and iv although PDI activity may initiate near the inner separatrix, the loss in fast electron bremsstrahlung is best correlated with the appearance of IC quasi-modes characteristic of the magnetic field strength near the LFS separatrix.

These data, supported by growth rate calculations, point to the importance of the LFS scrape-off layer SOL density in determining PDI onset and degradation in current drive efficiency.

Increased current drive efficiency at high density has been achieved in FTU and EAST through lithium coating and special fuelling methods, and in recent C-Mod experiments by operating at higher plasma current. Another approach would be to locate the launcher in the inner wall with double null operation. This would reduce the SOL density by an order of magnitude or more and greatly mitigate the effects of PDI as well as other parasitic losses. General recommendations include: 1 Research should be preferentially focused on the most technologically advanced options i.

I-mode operation appears to have naturally occurring suppression of large Edge-Localized Modes ELMs in addition to its highly favorable scalings of pedestal structure and overall performance. We apply similar tools to the structure and ELM stability of I-mode pedestals. Likewise, numerical modeling of the KBM turbulence onset, as well as scalings of the pedestal width with poloidal beta, indicates that I-mode pedestals are not limited by KBM turbulence—both features identified with the trigger for large ELMs, consistent with the observed suppression of large ELMs in I-mode.