Table of contents

The stability properties of non-inductively driven, reversed-shear type current profiles that may be achieved for Alcator C-Mod tokamak-like parameters (aspect ratio R/a = 3) are examined. It is found that without a conducting wall, the best stability results ( up to 3.7) are achieved for highly triangular plasmas at , for relatively broad pressure profiles and large values of . For elliptical or circular cross-sectional plasmas with little triangularity, the stability limits are significantly lower ). Finally, more-peaked pressure profiles have lower beta limits than broader profiles.

Circular cumulative jets produced by impacts of aluminium strikers upon conical targets are considered. Numerical results for two problems corresponding to certain experiments are presented. The first problem deals with the investigation of flow stability for axisymmetric perturbations of a metal - deuterium interface. The second problem deals with thin foils as compressing pistons.

The measurement of electron density in the JET pumped divertor by conventional reflectometry techniques is difficult because of poor access to the divertor region,unfavourable plasma geometry and the small plasma size. This paper presents a new reflectometer diagnostic which can operate in the difficult conditions of the pumped divertor. It is a `comb' reflectometer in which a number of microwave signals with different frequencies are launched simultaneously into the plasma, and the peak electron density along the sightline is estimated by determining which signals are transmitted and which are reflected. The design and operating principles of the diagnostic are described, and preliminary results illustrating its performance are presented.

Non-local effects have recently been observed in many transient experiments in different tokamaks. These effects have been modelled by introducing a non-local dependence in the Bohm part of a previously introduced model for L-mode, so that good simulations are obtained for L - H transitions, cold pulses, sawteeth and ELMs. This model also explains the improvement of core transport in the whole high-performance phase of H-mode ELM-free discharges.

In this paper, the analytical and computational theory of quasi-linear and toroidal effects on electron cyclotron current drive (ECCD) is presented. Simple analytical formulae for the estimation of the ECCD correction due to the action of high-power microwaves and banana electrons are obtained. The article extends the results of calculations performed with the use of the OGRAY code. Good agreement between the analytical and numerical calculations is obtained. The optimum conditions of ECCD are investigated.

The decay of an ion density discontinuity in a collisionless plasma is considered when allowance is made for the effect of ion temperature on the process. A proper rarefaction wave is given. It is shown that the process can be described without recourse to complicated computations. The theoretical, numerical and experimental results are found to be in reasonable agreement.

The effects of neutrals near the X-point of tokamaks on the L/H transition are examined. Four mechanisms for bipolar losses, i.e. the loss cone loss, the bulk viscosity loss, the charge-exchange (CX) loss between ions and neutrals and the anomalous loss, occur simultaneously in high-temperature plasmas. Neutral particles near the X-point are found to trigger the H-mode transition. They cause an additional ion loss cone loss via collisions. The lower limit of the neutral density near the X-point for the onset of the H-mode transition is estimated. Neutral particles at the main plasma are shown to prevent the H-mode transition because of CX loss.

A killer pellet is an impurity pellet that is injected into a tokamak plasma in order to terminate a discharge without causing serious damage to the tokamak machine. In JT-60U neon ice pellets have been injected into OH and NB heated plasmas and fast plasma shutdowns have been demonstrated without large vertical displacement. The heat pulse on the divertor plate has been greatly reduced by killer pellet injection (KPI), but a low-power heat flux tail with a long time duration is observed. The total energy on the divertor plate increases with longer heat flux tail, so it has been reduced by shortening the tail. Runaway electron (RE) generation has been observed just after KPI and/or in the later phase of the plasma current quench. However, RE generation has been avoided when large magnetic perturbations are excited. These experimental results clearly show that KPI is a credible fast shutdown method avoiding large vertical displacement, reducing heat flux on the divertor plate, and avoiding (or minimizing) RE generation.

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.

2 - 4 June 1997 9th National Topical Conference on High-Temperature Plasma Diagnostics St Petersburg, Russia Contact: Ms Galina Onishchuk, TRINITI, 142092 Troitsk Moscow Reg, Russia. Fax +7-095-334-5776, E-mail galina@fly.triniti.troitsk.ru. Application and abstract deadline: 1 March 1997.

27 August - 2 September 1997 International Conference on Superstrong Fields in Plasmas Villa Monastero, Varenna (Lc), Italy Contact: Mrs D Pifferetti, Secretariat Villa Monastero, 1 Piazza Venini, 22050 Varenna, Italy. Tel +39-341-831261, Fax +39-341-831281, E-mail ccvm@ccvm.cil.lc.it (abstracts should be sent to Dr M Lontano, Istituto di Fisica del Plasma, Consiglio Nazionale delle Ricerche, Via Cozzi 53, 20125 Milano, Italy. Tel +39-2-66173260, Fax +39-2-66173239, E-mail lontano@ifp.mi.cnr.it). Application and abstract deadline: 13 June 1997

4 - 12 September 1997 International Workshop on Diagnostics for Experimental Fusion Reactors Villa Monastero, Varenna, Italy Contact: D Pifferetti, Centro di Cultura `Villa Monastero', 1 Piazza Venini, 22050 Varenna (Lc) Italy. Tel +39-341-831261, Fax +39-341-831281, E-mail ccvm@ccvm.cil.lc.it. Application and abstract deadline: 13 June 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.

8 - 19 September 1997 3rd Carolus Magnus Summer School on Plasma Physics Spa, Belgium Contact: Dr G van Oost, c/o Institut für Plasmaphysik, Forschungszentrum Jülich GmbH, D-52425 Jülich, Germany. Tel +49-2461-61-5626, Fax +49-2461-61-3331, E-mail vanoost@fusion.rma.ac.be. Application deadline: 15 May 1997, abstract deadline: 15 July 1997.

13 October - 7 November 1997 Autumn College on Plasma Physics Miramare-Trieste, Italy Contact: S M Mahajan, International Centre for Theoretical Physics, Autumn College on Plasma Physics, PO Box 586, I-34100 Trieste, Italy. Tel +39-40-2240357, Fax +39-40-224163, E-mail smr1012@ictp.trieste.it. Application deadline: 30 April 1997.

10 - 14 November 1997 Topical Workshop on Plasma Physics: New Perspectives of Collective Effects Miramare-Trieste, Italy Contact: P K Shukla, International Centre for Theoretical Physics, PO Box 586, I-34100 Trieste, Italy. Tel +39-40-2240357, Fax +39-40-224163, E-mail smr1014@ictp.trieste.it. Application deadline: 31 March 1997.