An analysis is presented of runaway electron formation and its evolut,ion during disruptions in large tokamaks, where avalanche phenomena play a crucial role. A simplified, but sufficiently accurate, analytical model suitable for one dimensional (1-D) transport codes is proposed. Validation of the model was done by comparison with Monte Carlo calculations.

This paper presents the results of the latest analysis of disruption in tokamaks and the prediction of disruptions in ITER. The emphasis is on predictions of the halo current and its toroidal asymmetry in ITER, a study of runaway electron formation and an analysis of the concept for fast plasma shutdown by impurity injection. The concept of the plasma shutdown based on a massive injection of deuterium is also discussed.

Overview of C-2 field-reversed configuration experiment plasma diagnosticsa) Rev. Sci. Instrum. 85, 11D836 (2014); 10.1063/1.4884616 Density fluctuation measurements by far-forward collective scattering in the MST reversed-field pincha) Rev. Sci. Instrum. 83, 10E302 (2012);A new high performance field reversed configuration operating regime in the C-2 devicea)Conventional field-reversed configurations (FRCs), high-beta, prolate compact toroids embedded in poloidal magnetic fields, face notable stability and confinement concerns. These can be ameliorated by various control techniques, such as introducing a significant fast ion population. Indeed, adding neutral beam injection into the FRC over the past half-decade has contributed to striking improvements in confinement and stability. Further, the addition of electrically biased plasma guns at the ends, magnetic end plugs, and advanced surface conditioning led to dramatic reductions in turbulence-driven losses and greatly improved stability. Together, these enabled the build-up of a well-confined and dominant fast-ion population. Under such conditions, highly reproducible, macroscopically stable hot FRCs (with total plasma temperature of $1 keV) with record lifetimes were achieved. These accomplishments point to the prospect of advanced, beam-driven FRCs as an intriguing path toward fusion reactors. This paper reviews key results and presents context for further interpretation. V C 2015 AIP Publishing LLC. [http://dx.

A hot stable field-reversed configuration (FRC) has been produced in the C-2 experiment by colliding and merging two high-β plasmoids preformed by the dynamic version of field-reversed θ-pinch technology. The merging process exhibits the highest poloidal flux amplification obtained in a magnetic confinement system (over tenfold increase). Most of the kinetic energy is converted into thermal energy with total temperature (T{i}+T{e}) exceeding 0.5 keV. The final FRC state exhibits a record FRC lifetime with flux confinement approaching classical values. These findings should have significant implications for fusion research and the physics of magnetic reconnection.

Fusion reactivity for the pB11 fuel has been reassessed for magnetic confinement devices. This study is based on two factors: new measurements of the fusion reaction cross-sections and an accounting of the kinetic effects that lead to the increase of the number of protons at higher energies (with respect to a pure Maxwellian). The net effect leads to an approximately 30% increase of the fusion yield for the same global plasma parameters compared to the previous assessments.