Multi-range tomographic system for transport studies in tokamak plasmas Project ID: GA202/09/1467 Provider: Czech Science Foundation Period: Jan 01, 2009 - Dec 31, 2012 Principal Investigator: Mgr. Vladimír Weinzettl, Ph.D. Co-investigators , , , , , , , , Aims of the project: Future realization of tokamak based fusion power plants will be possible only if a question of the particle and energy transport across the magnetic field toward the first wall and connected technical problems of extremely high heat loads to plasma-facing components will be satisfactorily solved.The main aim of this project is to contribute to an understanding of physics behind transport processes in magnetically confined plasmas using fast tomographic measurements in different spectral regions (bolometry, soft X-rays, visible light) and their comparison with results of other sufficiently fast plasma diagnostics. Prospective spatial resolution of the constructed tomographic systems will range in centimeter scales on plasma column at fewmicroseconds time base. Research will be done under the EURATOM Treaty in a broad international collaboration by a team of young scientists. Progress/Results: The main aim of the project was to contribute to understanding of mechanisms behind transport processes in plasma of big experimental devices with magnetic confinement. The project was based on a broad international collaboration in the frame of European organizations EURATOM and EFDA (European Fusion Development Agreement). The tasks have been realized on the Czech COMPASS tokamak, on the JET tokamak in England as well as on the German tokamak ASDEX-Upgrade. On COMPASS at IPP AS CR, v.v.i., the unique, highly compact tomographic system suitable for measurements of fast processes observable in different spectral ranges has been designed and constructed there. The role of tearing mode instability has been analyzed and its characteristics have been measured. Sawteeth instability has been identified in discharges with a divertor plasma configuration and its characteristics have been measured. The characteristic flat shape of the measured density profile has been connected with a presence of this instability. The observed L- to H-mode transition has been always triggered by sawteeth instability. The consequent increase of both the core plasma density and temperature has been measured as a result of the decreased radial transport, thus, the increased energy and particle confinement time. On the German ASDEX Upgrade tokamak, the experiment with edge plasma biasing by the reciprocating manipulator has been realized. It has not been confirmed that a perturbation of the radial electric field can trigger the ELM type I instability, however, a local perturbation of the plasma density profile does. The edge plasma parameters in both L- and H-modes have been measured and compared using a combination of ball-pen and Langmuir probes located on the reciprocating manipulator. An agreement of the interchange turbulence model generating blobs in the edge plasma with the experiment has been demonstrated. Also, a dominance of electron density fluctuations over fluctuations of both temperature and plasma potential has been shown. By use of fast probe measurements of both electron density and temperature in ELMy H-mode, the concept of the filament structure of the ELM instability has been confirmed. On the JET tokamak in England, the algorithm of the pixel method based on Minimum Fischer Regularization has been optimized. Although, it is used for reconstructions of neutron radiation on JET, the code has been accommodated for the other tokamaks (COMPASS, TORE SUPRA, TCV) to perform a tomography of the local radiated power from data of both soft X-ray and bolometric diagnostics. Next, an analysis of the experimental data from the JET tokamak recording H-mode transitions from/to regimes of ELM type I and III has been done. The measured experimental scaling have been incorporated to the international database, which is used to create new experimental proposals on existing tokamaks as well as new scenarios for ITER and DEMO. The grant project has also contributed significantly to education of the new generation of scientists in the field of thermonuclear fusion. Many Czech as well as foreign students have been participated in the project (including 9 PhD students) resulting in four defended bachelor theses, three defended diploma theses and one defended PhD thesis. The milestones of the project were fulfilled.