FOREWORD

Abstract

The 9th International Workshop on Carbon Materials was held on the 18th and 19th of September 2000 in Hohenkammer Castle nearby Munich, Germany. The symposium was jointly organised by the Max-Planck-Institute für Plasmaphysik (Garching) and Forschungszentrum Jülich, Germany. Previous symposia of this series took place at the Forschungszentrum Jülich, Germany (seven meetings) and once at the Royal Institute of Technology (KTH) in Stockholm, Sweden. Participation of experts from overseas is always essential to keep high scientific standards. Therefore, the Carbon Workshops have been organised as satellite ones to a large conference held in Europe. This time, it was in connection with the 21st Symposium on Fusion Technology (SOFT) held a week earlier in Madrid, Spain.These workshops have been perceived as a forum for open discussion aiming at the evaluation of the behaviour and properties of carbon as a material for plasma facing components in controlled fusion devices. Unfortunately, the list of relevant materials for the first wall in a fusion reactor is short and carbon is one of only few choices; the others are beryllium and tungsten. A very important and attractive feature of carbon is, that its properties can be tailored to meet designed requirements regarding, for instance, thermal conductivity and mechanical strength. In this sense, "carbon" is a common name for a great variety of graphite-based materials: from highly purified isotropic graphite to multidirectional fibre composites and plasma sprayed layers, including those doped with boron, silicon, titanium or their carbides.It has been a tradition of this workshop that each time three specific subjects have been selected for detailed discussions. The topics presented in Hohenkammer were: Erosion and Deposition Dust Formation and Tritium Retention New Carbon-based Materials Basic scientific and technical aspects have always been in the scope of the meeting. Therefore, among 64 registered participants there were experts from institutes of plasma physics, material engineering laboratories and industrial companies. The scientific programme consisted of 17 invited talks, two guided summary & general discussion sessions and presentation of over 20 posters. The programme covered a wide range of topics spanning from fundamental processes underlying the reactions between hydrogen atoms and CH3 radicals with carbonaceous surfaces to the development of plasma facing components for a next-step device. There were talks on the evaluation of spectroscopic data from the edge and divertor plasmas and, on the "wash-and-flush" concepts to remove dust from the vacuum vessel of fusion devices. Much attention was focused on the influence of hydrogen flux density (so-called "flux dependence") on the erosion rate of carbon. This volume contains a selection of works presented.The presentations documenting that significant progress have been made in all the treated topics since the 8th Carbon Workshop. However, it has also been obvious that many open questions remain. In our view, the most important are: the flux dependence of carbon erosion and the evaluation of corresponding data; erosion and deposition of hydrogenated carbon layers because of their huge contribution to the total fuel inventory in plasma facing components; basic erosion processes (the energy gap for hydrogen erosion between thermal energies and about 10 eV); the influence of material mixing on the performance of plasma facing components. Impressive progress has been achieved in the development and manufacturing of actively cooled plasma facing components. We are looking forward to see the results of the first large-scale application, in Tore Supra, which will be known in two years.It appears that a safe prediction for a material choice for a next-step device cannot be made on the basis of available data and much more efforts have to be undertaken to address open questions in the field. We will hopefully be able to present a number of answers to those open questions on the occasion of the 10th Carbon Workshop. Finally, the symposium was also a great opportunity to express deep gratitude and to warmly say "good bye" to some of the protagonists and pioneers in the field. Gottfried Veider, who acted as a member of the programme committee of this workshop, retired in the mid of 2000. Egon Vietzke, who devoted most of his scientific career to the basic studies and deep understanding of hydrogen - carbon interactions, will retire at the end of this year. We wish them good, good health and many exciting activities beyond carbon and fusion.We would like to thank our sponsors: Max-Planck-Institute für Plasmaphysik and Forschungszentrum Jülich. Their support helped to keep the registration fee low and to make the meeting effective, fruitful and pleasant in the beautiful scenery of Hohenkammer. We thank our secretary, Mrs. Katharin Marx, for her efforts in the organisation of the symposium and Hans Meier for the creation and maintenance of the workshop web-page. We thank all the participants, authors and referees of the articles for their co-operation.