ФОТОЯДЕРНЫЙ ЭФФЕКТ Н А НИКЕЛЕ, МЕДИ И ЦИНКЕ

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Plasma acceleration in a wave with varying frequency

The averaged velocity of a test particle and the averaged velocity of a plasma in an electro-magnetic wave packet with varying frequency (e.g., a radiation pulse from pulsar) is derived. The total momentum left by the wave packet in regions of plasma inhomogeneity is found. If the plasma concentration is changing due to ionization, the plasma may be accelerated parallelly or antiparallelly to the direction of the wave packet propagation, which is relevant for a laser induced breakdown in gas.The author thanks R.Klíma for numerous discussions.     

Theoretical estimates of radial electric fields and plasma rotation induced in H-1NF by RF waves

The purpose of this study is to estimate, for planned experiments at the H-1NF heliac, nonlinear variations of the stationary radial electric field, and poloidal and toroidal plasma rotation, that result from ponderomotive forces exerted by large amplitude RF waves in the H-1NF. Similarly as in the previous studies of nonlinear transport effects induced by RF waves, the nonlinear ponderomotive force effects on the radial electric field, toroidal and poloidal plasma rotation become important for dissipated powers of the order of 1 MWm^–3 for RF waves with frequency of about 10 MHz. At these high RF powers, the nonlinear ponderomotive force effects might therefore result in important changes in plasma confinement and RF wave coupling in H-1NF.This work has been partially supported by the Australian National University, by the DIST Department of the Australian Government, by the Czech Grant Agency grants No. 202/96/1355 and 1350, and by the Queen Elisabeth II grant administered by G.G. Borg. The author is grateful to G.G. Borg and R.L. Dewar for many stimulating discussions.     

JET: Preparing the future in fusion

JET (Joint European Torus) is the largest tokamak in the world and the only fusion facility able to operate with Tritium, the fusion fuel, and Beryllium, the ITER first wall material. JET also features the most complete remote handling equipment for invessel maintenance. As a multinational research center, JET provides logistic experience in preparing for operation of the global facility, tokamak ITER.Experiments on JET are focused on ITER-relevant studies, in particular on detailing the operational scenarios (EL My H-modes and advanced regimes), on enhancing the heating systems, on developing diagnostics for burning plasmas etc. Pioneering real-time control techniques have been implemented that maximize performance and minimize internal disturbances of JET plasmas. In helium plasmas, ion cyclotron heating (ICRH) created fast α-particles, mimicking their populations in future burning plasmas. The recent successful Trace Tritium campaign provided important new data on fuel transport. Current enhancements on JET include a new ITER-like ELM-resilient high power ICRH antenna (7 MW) and over twenty new diagnostics that will further extend the JET scientific capabilities and push the facility even closer to the ITER parameters.A special mention is given to the involvement of the fusion experts from Association EURATOM-IPP.CR, who have been actively participating in the collective use of JET facility for more than three years.     

Fast electrons generation by RF and random fields near the antenna I. One dimensional model and regular fields

Test particle motion and acceleration has been explored in strong radio frequency (RF) fields, for which quasilinear ponderomotive force approximation is not valid. By nonlinear acceleration in spatially varying wave amplitude of RF travelling wave, electrons may be accelerated to time averaged velocities significantly larger than the RF wave phase velocity, and than the boundary plasma thermal velocity, in RF fields of several Volts per centimeter at wave frequency of 7 MHz. It is also demonstrated that even weak spatial gradients, much weaker than those expected in experiments, of the RF wave field amplitude, have significant consequences for the particle motion. Estimates are presented of the total energy transferred from the near antenna RF field to the plasma due to the nonlinear electron acceleration effects.     

On the bootstrap effect in large tokamaks with lower hybrid driven current

The amplification of lower hybrid (LH) driven current of various profiles has been found. The results strongly depend on the plasma temperature profile, on the LH current profile, and on the magnitude of the particle diffusion flux.This work was started during the visit of the author in the I. V. Kurchatov Institute of Atomic Energy, Moscow. The author thanks IAE for hospitality, and V. Parail, G. V. Pereverzev, A. Smoljakov and R. Klíma for many useful and critical discussions.