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In toroidal magnetically confined plasmas, eigenmodes of Alfvén waves can be destablized by energetic ions with velocities comparable to the Alfvén velocity. With the advent of tokamak experiments in which populations of energetic ions can be introduced by neutral beam injection, radio frequency wave heating or by fusion reactions, major advances have been made in Alfvén eigenmode research in the past 10 years. After introducing the basic concepts on the Alfvén eigenmode instability, data on this subject from various toroidal devices are described, emphasizing the interplay between experiment and theory. Experimental results on mode identification, instability drive, mode damping and saturation, and energetic ion redistribution are compared with theory.

The code TORIC solves the finite Larmor radius wave equations in the ion cyclotron range of frequencies in arbitrary axisymmetric toroidal geometry. The model used, based on the finite Larmor radius approximation, describes the compressional and torsional Alfvén waves and ion Bernstein waves excited by linear mode conversion. Absorption by the ions occurs at the fundamental and first harmonic of the cyclotron frequency, and by the electrons through Landau and transit time damping.

The numerical solution is based on the spectral representation of the wave fields in the poloidal angle , and cubic finite elements in the radial variable . The spectral approach in the poloidal angle allows us to evaluate in a numerically efficient way the integrals over the particle orbits along magnetic field lines which arise when the high frequency (HF) plasma current is obtained by solving the linearized Vlasov equation; the leading effects of toroidicity on cyclotron absorption and spatial dispersion are also taken into account. The code offers a number of options, which allow us to compare the complete finite Larmor radius model with simpler approximations, such as the widely used order reduction algorithm, which replaces the excitation of ion Bernstein waves with an equivalent power sink.

The magnetic island width during long-pulse, high- discharges was evaluated by measuring oscillations of electron cyclotron emission using a heterodyne radiometer. Because of its high spatial resolution of about 2 cm, evolution of the magnetic island structure can be measured in detail. The island width increases with the amplitude of the magnetic fluctuations. The saturated island width was about 7 cm when the m/n = 3/2 mode appeared. The resistive modes which limit the sustainable have typical mode numbers of m/n = 3/2 and 2/1. The relationship between the observed magnetic island and the neoclassical tearing mode is discussed.

A new radiative cooling curve for molybdenum, determined from the Hebrew University, Jerusalem - Lawrence Livermore atomic code (HULLAC) has been used to estimate the radiative power losses from various ion cyclotron resonance frequency (ICRF) and ohmically heated Alcator C-Mod tokamak plasmas and ohmically heated Frascati tokamak upgrade (FTU) plasmas. This cooling curve has been found to accurately predict the radiative losses from molybdenum ions in plasma. Radiative losses from molybdenum computed by using the HULLAC cooling curve could typically account for greater than 60% of the total radiative losses as measured by bolometry in Alcator C-Mod tokamak plasmas. The molybdenum density was found to be as high as particles in ICRF heated plasmas. Plasmas after botonization of the plasma facing surfaces had the lowest molybdenum density and radiated power of all the plasmas examined; ICRF heated plasmas had the highest. The molybdenum density and radiative power losses were found to increase roughly linearly with input ICRF power during different heating schemes in plasmas with both H-mode and L-mode confinement. Although the molybdenum densities were found to decrease with increasing electron density, the radiative power losses did not change significantly for all types of plasmas studied in Alcator C-Mod and FTU: diverted plasmas heated with ICRF and both limited and diverted plasmas heated ohmically.

Effects on reflectometer phase and power fluctuation signals due to (a) asymmetries in the transmit-plasma-receive antenna geometry (misalignments), and (b) asymmetries in the plasma cut-off layer perturbations (distortions from sinusoidal or Gaussian) are studied using a two-dimensional (2D) physical optics model. Results show the onset of phase runaway with antenna misalignment and/or sawtooth type perturbations when the perturbation amplitude exceeds some critical value. For broadband (Gaussian) turbulence antenna misalignment leads to Doppler shifts in the spectrum - provided the reflectometer beam width w and spectral width of the turbulence are sufficiently large. Misalignment also generates coherence between and at Bragg backscatter frequencies with quadrature phase difference. Sawtooth (asymmetric gradient) perturbations also generate phase-power coherence in quadrature, but at frequencies determined by w and , i.e. not Bragg. Cusped or spiky (asymmetric amplitude) perturbations generate asymmetric phase distributions (nonlinear phase offsets) and low-frequency phase-power coherence with 0 or phase difference. The simulations indicate that a combination of antenna misalignment (or plasma tilt) and cusped reflection layer perturbations can account for a wide range of experimentally reported features in reflectometer signals.

Experimental results on the heating of matter carried out in a study on laser-driven shock waves in aluminium are discussed. The measured temporal evolution of the `colour' temperature of the rear surface of the target is compared with that computed by numerical codes. We show how the target preheating can substantially affect optical signals recorded from the rear side of the target, and consequently influence the accuracy of temperature and pressure measurements of the material behind the shock wavefront.

The extreme ultraviolet (XUV) spectrum of C V and C VI from the edge plasma in JET has been analysed and a collisional radiative model (CRM) is used to simulate the line emissivities. We view, in the XUV range, the scrape-off layer (SOL) during the limiter phase of the discharge evolution, whereas, when the divertor configuration is established, the X-point region is viewed. A zero-dimensional model of the SOL has shown that the line ratios are sensitive to the peripheral profiles (T_e, n_D fraction and carbon ionization degree) and these parameters are inferred as a function of time for an ohmic JET discharge. We find that charge exchange of carbon ions with deuterium (the filling gas) is an important process in the SOL and near-edge plasma and is included as an integral part of the CRM.

In the EXTRAP T2 reversed-field pinch the diagnostic techniques for the measurement of electron density and temperature include; Thomson scattering which gives values at three radial positions in the core (r/a = 0, 0.28, 0.56), Langmuir probes which give values at the edge (r/a > 0.9) and interferometry which gives a line-averaged density. The empirical scaling of electron density and temperature including profile information with global plasma parameters has been studied. The density profile is subject to large variations, with an average parabolic shape when the density is low and flatter shapes when the density is increased. The change in the profile shape can be attributed to a shift in the penetration length of neutrals from the vicinity of the wall. The temperature scales roughly as I/n^1/2 where I is the plasma current and n is the density. The temperature profile is always quite flat with lower variations and there is a tendency for a flatter profile at higher temperatures.

The 5th EFPW took place in December 1997 at Sesimbra in Portugal. It was hosted by the Instituto Superior Técnico, Lisbon and sponsored by the European Commission. Within an overall theme of magnetohydrodynamic (MHD) phenomena in magnetically confined plasmas, four topics of importance to the future development of magnetic confinement fusion were discussed in detail: integrated control of fusion plasmas, MHD in advanced scenarios, neoclassical modes and disruptions. In addition, an extended review of the results of the recent JET deuterium-tritium experiments was presented and the physics research opportunities which would be made available by ITER operation were discussed. The main issues discussed in each session and the areas identified as requiring further study are summarized here.

14-18 June 1999 26th European Physical Society Conference on Controlled Fusion and Plasma PhysicsMaastricht, The Netherlands Contact: Dr E Vietzke. E-mail: EPS99@fz-juelich.de, Website: http://www.rijnh.nl Registration and abstract deadline: 31 January 1999.

5-16 July 1999 36th Culham Plasma Physics Summer SchoolCulham, Oxfordshire, UK Contact: Mrs Julie Bright, UKAEA, Culham Division, Culham Science Centre, Abingdon, Oxfordshire OX14 3DB, UK. E-mail: julie.bright@ukaea.org.uk, Website: http://www.fusion.org.uk/info/sschool99.htm, Tel: +44 1235 463773, Fax: +44 1235 463288.

19-21 July 1999 2nd IAEA Technical Committee Meeting on Control, Data Acquisition and Remote Participation for Fusion ResearchLisboa, Portugal Website: http://www.cfn.ist.pt

2-6 August 1999 14th International Symposium on Plasma ChemistryPrague, Czech Republic Contact: V Sember. E-mail: sember@ipp.cas.cz, Website: http://www.ipp.cas.cz/NTP/ispc-14/index.html

6-10 September 1999 International Topical Conference on Plasma Physics: New Frontiers of Nonlinear SciencesFaro, Portugal Contact: Mr R Guerra, Department of Physics, University of Algarve, Faro, Portugal. E-mail: rguerra@mozart.si.ualg.pt. Registration deadline: 30 November 1998, abstract deadline: 15 February 1999.