J. A. Merrifield T. D. Arber S. C. Chapman R. O. Dendy
Understanding the phenomenology captured in direct numerical simulation (DNS) of magnetohydrodynamic (MHD) turbulence rests upon models and assumptions concerning the scaling of field variables and dissipation. Here compressible MHD turbulence is simulated in two spatial dimensions by solving the isothermal equations of resistive MHD on a periodic …
PublishedD. A. Murdick X. W. Zhou H. N. G. Wadley D. Nguyen-Manh R. Drautz D. G. Pettifor
An analytic, bond-order potential BOP is proposed and parametrized for the gallium arsenide system. The potential addresses primary and secondary bonding and the valence-dependent character of heteroatomic bonding, and it can be combined with an electron counting potential to address the distribution of electrons on the GaAs surface. The potential …
PublishedG. Van Oost E. Del Bosco M. P. Gryaznevich A. Malaquias G. Mank
Small tokamaks may significantly contribute to the better understanding of phenomena in a wide range of fields such as plasma confinement and energy transport; plasma stability in different magnetic configurations; plasma turbulence and its impact on local and global plasma parameters; processes at the plasma edge and plasma-wall interaction; scena…
PublishedC. G. Gimblett
This paper discusses an approach to modelling Edge Localised Modes (ELMs) in which toroidal peeling modes are envisaged to initiate a constrained relaxation of the tokamak outer region plasma. Relaxation produces both a flattened edge current profile (which tends to further destabilise a peeling mode), and a plasma-vacuum negative current sheet whi…
PublishedH. Smith P. Helander L.-G. Eriksson T. Fülöp
The usual calculation of Dreicer [Phys. Rev. 115 , 238 (1959); 117 , 329 (1960)] generation of runaway electrons assumes that the plasma is in a steady state. In a tokamak disruption this is not necessarily true since the plasma cools down quickly and the collision time for electrons at the runaway threshold energy can be comparable to the cooling …
PublishedC. N. Lashmore-Davies A. Thyagaraja D. R. Mccarthy
The mechanism of four nonlinearly interacting drift or Rossby waves is used as the basic process underlying the turbulent evolution of both the Charney-Hasegawa-Mima-equation CHME and its generalized modification GCHME. Hasegawa and Kodama’s concept of equivalent action or quanta is applied to the four-wave system and shown to control the distrib…
PublishedA. J. Webster D. J. Szwer H. R. Wilson
Modern tokamaks can produce transport barriers TBs—localized regions with an increased energy confinement. Previous studies have been unable to examine the stability of internal TBs to radially extended short-wavelength magnetohydrodynamic instabilities “ballooning modes”, for the usual case with a sheared plasma flow and a magnetic shear tha…
PublishedK. G. McClements
A full orbit code is used to compute collisionless losses of fusion particles from three proposed burning plasma tokamaks: the International Tokamak Experimental Reactor ITER; a spherical tokamak power plant (STPP) [T. C. Hender, A. Bond, J. Edwards, P. J. Karditsas, K. G. McClements, J. Mustoe, D. V. Sherwood, G. M. Voss, and H. R. Wilson, Fusion …
PublishedP. Helander R. J. Akers
The collisional interaction between neutral-beam ions and bulk plasma electrons leads to convective transport of particles and energy similar to the well-known Ware pinch. These transport fluxes are calculated, and it is found that the particle flux is outward when the neutral beams are in the same direction as the plasma current and inward otherwi…
PublishedC. Lang D. J. H. Cockayne D. Nguyen-Manh
Atomistic simulations combining a Monte Carlo algorithm and molecular static relaxations were carried out to predict the alloying profile in pyramid and dome shaped Ge(Si)/Si(001) islands. The results show that the composition profile is dominated by the surface segregation of Ge and segregation of Si to the substrate island interface. Within the i…
Published