Table of contents

Recent theoretical and experimental research with short-pulse, high-intensity lasers is surveyed with particular emphasis on new physical processes that occur in interactions with low- and high-density plasmas. Basic models of femtosecond laser - solid interaction are described including collisional absorption, transport, hydrodynamics, fast electron and hard x-ray generation, together with recently predicted phenomena at extreme intensities, such as gigagauss magnetic fields and induced transparency. New developments in the complementary field of nonlinear propagation in ionized gases are reviewed, including field ionization, relativistic self-focusing, wakefield generation and scattering instabilities. Applications in the areas of x-ray generation for medical and biological imaging, new coherent light sources, nonlinear wave guiding and particle acceleration are also examined.

A method to calculate the electron Landau damping of toroidal Alfvén eigenmodes (TAE) is presented. Owing to the presence of a small current produced by thermal electrons near the trapped - passing boundary, a jump in the electrostatic potential near the surface occurs. An analytic expression for this jump is derived in the low-, large-aspect-ratio limit, and is suitable for incorporation into either numerical eigenvalue codes or analytic models. In the limit of small magnetic shear, the calculation is performed analytically, giving a simple local expression for the damping.

A model for the ballooning mode destabilization in the presence of a sufficiently large island is developed. This model may explain the fast MHD activity (sawtooth-like) observed on Tore Supra during LH current drive in shearless equilibrium regimes with a safety factor on axis of just less than two. A simple analytical stability criterion is derived which indicates whenever an equilibrium is stable or unstable against the ballooning mode. The model is supported by Tore Supra experimental data and may also apply in other tokamaks exhibiting nearly flat q-profiles.

A general expression for the growth rate of the toroidal Alfvén eigenmode (TAE) instability is derived by employing a Hamiltonian action-angle approach. It takes into account the finite orbit width effects, the finite Larmor radius (FLR) effects of energetic particles and the effect of mode localization, as well as the possible mode excitation by both passing and trapped energetic ions. In particular, the stabilizing effect of the large particle orbit widths on the TAE modes excited by fast passing and trapped ions is investigated. In the limiting cases when and , the instability drive is reduced by factors of and , respectively, as compared with the prediction of the narrow orbit theory, when , where is the particle orbit width and is the inner (outer) width of the mode structure. For the TFTR parameters, the stabilization effect is much stronger in the case of TAE excitation by fusion-produced alpha particles than that in connection with neutral beam injection (NBI)-generated energetic ions.

In this paper, observations are presented of ICRF wave modes that propagate in the form of narrow beams along magnetic field lines in the plasma edge. A beam composed of evanescent shear waves was observed above the ion cyclotron frequency using edge magnetic probes. Observations of the beam were also obtained around the transition defined by , where the shear wave is propagating for and evanescent for . A previously unobserved localized edge feature above the ion cyclotron frequency is also described and is attributed to high m > 0 propagating fast wave modes.

The implosion dynamics of a high density -pinch plasma driven by a spinning annular gas-puff of negligible thickness is investigated. Numerical results show that spinning the outer Z-pinch plasma alone, though adequate to suppress the growth of RT instability, is not enough to achieve thermonuclear fusion conditions with staged pinch. However if, together with the spinning gas-puff, one uses high- Z impurity seeded DT-fibre, then owing to radiative collapse, thermonuclear fusion conditions are achievable.

Analytical expressions for the wave permeability tensor are derived for a two-dimensional plasma model of a straight axisymmetric mirror trap. The dielectric tensor components are found through a solution of the Vlasov equation, using the theory of Jacobian elliptic functions. The bounce-resonance effect of trapped particles on wave dissipation is analysed. It is shown that collisionless wave dissipation in the plasma with a mirror-trap configuration of a magnetic field can differ essentially from Landau damping in a plasma with straight uniform magnetic field lines. This dielectric tensor can be used in numerical calculations of Alfvén and ion cyclotron heating of mirror-trap plasmas.

Using the combination of early neutral beam injection, ramping of the plasma current, low electron density and controlled L - H transitions, robust discharges with negative central magnetic shear are reproducibly obtained on the DIII-D tokamak. The effects of these factors on the formation and evolution of the q profile during the initial phase of these discharges are documented. Details of the evolution of the inverted q profile are obtained from measurements of the internal field pitch using a 16-channel motional Stark effect (MSE) system. Time-dependent MSE data are used to directly construct the profile of the toroidal electric field and allow a straightforward calculation of the non-inductive current density profile.

It is shown that it is possible to measure both the plasma density and the poloidal magnetic field simultaneously by polarimetry, purely from phase measurements. The latter are advantageous compared with previously proposed amplitude measurements. The phase measurements can be performed either by modulating the input polarization (two alternative configurations for this modulation are considered), or by modulating the output polarization. The merits of the three schemes are discussed. The polarimeter required for these measurements is simpler and more robust than the conventional interferometer - polarimeter presently used for the combined density and magnetic field measurements.

The simulation and analysis of neutron signals of plasmas heated by neutral beam injection (NBI) requires fast computer codes for evaluating non-thermal velocity distributions. In such calculations effects of sawtooth activity are usually neglected. In this comment, the consequences of such an approximation are discussed. The time-dependent bounce-averaged Fokker - Planck equation is solved numerically. The solution is used to calculate the effect of sawtooth activity on the time evolution of the fusion reactivity.

8 - 19 July 1996 33rd Culham Plasma Physics Summer School (UKAEA/Euratom) Oxford, UK Contact: Mrs J Bright, UKAEA Fusion, Culham, Abingdon, Oxfordshire, OX14 3DB, UK. Tel +44-1235-463773, Fax +44-1235-463474, E-mail julie.bright@ukaea.org.uk.

8 - 18 August 1996 International Summer School on Plasma Physics and Technology La Jolla, CA, USA Contact: Mr V Stefan, Institute for Advanced Physics Studies, PO Box 2964, La Jolla, CA 92038, USA. Tel +1-619-456-5737.

26 - 30 August 1996 Joint Varenna - Lausanne International Workshop on Theory of Fusion Plasmas Villa Monastero, Varenna, Italy Contact: Centro di Cultura Villa Monastero, 1 Piazza Venini, 22050 Varenna (Lecco), Italy. Tel +39-341-831261, Fax +39-341-831281. Application and abstract deadline: 15 June 1996.

2 - 5 September 1996 EU - US Workshop on Transport in Fusion Plasmas Villa Monastero, Varenna, Italy Further information: G Gorini, ISPP, 16 Via Celoria, I-20133 Milano, Italy. Tel +39-2-2392637, Fax +39-2-2392205, E-mail ggorini@mi.infn.it.

Administrative contact: Centro di Cultura Villa Monastero, 1 Piazza Venini, 22050 Varenna (Lecco), Italy. Tel +39-341-831261, Fax +39-341-831281. Application and abstract deadline: 15 June 1996.

9 - 13 September 1996 International Conference on Plasma Physics Nagoya, Japan Contact: Conference Secretariat, c/o Prof. Hiromu Momota, National Institute for Fusion Science, Nagoya 464-01, Japan. Tel +81-52-789-4260, Fax +81-52-789-1037, E-mail icpp96@nifs.ac.jp. Abstract deadline: 31 March 1996.

16 - 20 September 1996 19th Symposium on Fusion Technology Lisbon, Portugal Contact: Professor Carlos Varandas, Centro de Fusão Nuclear, 1096 Lisboa Codex, Portugal. Fax +351-1-8417819, E-mail cvarandas@cfn.ist.utl.pt. General information will be available via WWW with URL http://www.cfn.ist.utl.pt.

25 - 29 September 1996 Summer University of Plasma Physics Garching, Germany Contact: Ms Ch Stahlberg, Max-Planck-Institut für PlasmaPhysik, Boltzmannstr 2, D-85748 Garching, Germany. Tel +49-89-3299-2232, Fax +49-89-3299-1001.

2 - 4 October 1996 6th European Conference on Fusion Theory Utrecht, The Netherlands Contact: T J Schep, FOM - Institute for Plasma Physics, Postbus 1207, NL-3430 BE Nieuwegein, Netherlands. Tel +31-3402-312-24.

11 - 15 November 1996 38th Annual Meeting of the Division of Plasma Physics, APS Denver, CO, USA Contact: Dr Richard Hazeltine, University of Texas, Institute for Fusion Studies, RLM 11.314, Austin, TX 78712. Tel +1-512-471-1322, E-mail stewart@hagar.ph.utexas.edu.

6 - 11 April 1997 10th Joint Workshop on Electron Cyclotron Emission and Electron Cyclotron Resonance Heating Ameland, The Netherlands Contact: J Hamers-Smit, FOM - Instituut voor Plasmafysica 'Rijnhuizen', Postbus 1207, 3430 BE Nieuwegein. Tel +31-30-6096999, Fax +31-30-6031204, E-mail ec10@rijnh.nl. Application and abstract deadline: 17 January 1997.

8 - 12 September 1997 12th International Conference on Gas Discharges and their Applications Greifswald, Germany Contact: Dr G Babucke, Inst. f. Niedertemperatur-Plasmaphysik, Robert-Blum-Str. 8 - 10, 17489 Greifswald, Germany. Tel +49-3834-554411, Fax +49-3834-554301, E-mail gd97@public.inp.uni-greifswald.de.