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The National Energy Research Scientific Computing Center (NERSC) was originally launched as a computing center for the exclusive support of magnetic confinement fusion research in the US. There is, thus, a long history of computational advances and successes that ties fusion scientists with NERSC and its staff. One example of the numerous computational achievements enabled by NERSC in this field is the development of the global gyrokinetic particle-in-cell approach for the simulation of turbulent transport in tokamak fusion devices. This article describes the historical evolution of this method and the codes implementing it, and the impact that NERSC had in their development and the scientific discoveries that they allow. [ABSTRACT FROM AUTHOR]

The primary goal of the extreme-scale plasma turbulence studies described in this article is to gain new insights on confinement scaling in magnetic fusion systems by using powerful, world-class supercomputers to carry out simulations with unprecedented resolution and temporal duration. New insights have been gained on the key question of how the turbulent transport of thermal energy and particles in the plasma and the associated confinement scale from present-generation devices to much larger ITER-size plasmas. In particular, new results from large-scale simulation studies have demonstrated that improvement in confinement as devices grow larger is far more gradual, with significantly lower loss rates than less-powerful computer simulations have indicated in research carried out over the past decade. [ABSTRACT FROM PUBLISHER]

This letter reports on the design, fabrication, and testing a new class of low-impedance multiple-frequency micromechanical resonator using piezoelectric transduction mechanism. The resonator is fabricated out of a 3-µm-thick silicon layer on a silicon-on-insulator wafer with a low-temperature post-CMOS compatible process. Two types of low-impedance resonators using the same design principle are presented here. The center frequency of the novel resonator is set by the lithographically defined in-plane dimension of the device (width of bar or radius of disk). The 200-µm-diameter disk-shaped resonator is measured to have an impedance of 1.6 kΩ at the resonant frequency of 45.4 MHz, with a quality factor of 1100. The bar-type resonator is measured to have an impedance of 920 µ at 60 MHz, exhibiting a Q factor of 1400. [ABSTRACT FROM AUTHOR]