Beam Emission Spectroscopy Group
Department
Plasma Physics

Group leader: Dániel Dunai

The website od the group: wigner.mta.hu/beam_emission_spectroscopy

The group works on the physics aspects of controlled fusion, i.e. the most promising large scale climate neutral energy production scheme on the long term. Most of the research activities are implemented through the EUROfusion consortium, the integrated fusion program of the EU, in which Wigner RCP is the national participant nominated by the Hungarian Government. Our group adopts its own developed technologies to develop, manufacture, and operate state-of-art measurement systems in leading fusion devices in the EU and worldwide: JET(EU), MAST(UK), AUG(DE), W7-X(DE), KSTAR(KO), EAST(CN), JT60SA(JP), COMPASS (CZ). Participating in large scale fusion experiments also gives the chance to our industrial partners (Optimal Optik, OMI Optic, C3D, Evopro, etc..) to tender in European and World wide calls. The fruitful collaboration between the basic research and industry gives long term benefits for Hungary. The achieved scientific results are published in leading journals of the field. Partial funding for these activities is provided by the ITER EU Domestic Agency (F4E) and EUROfusion.    
Members of the research group are experts of various fields, which are detailed in the following sections.

Beam Emission Spectroscopy Diagnostics

Several of our systems are key components on large fusion experiments (EAST, KSTAR, MAST, Wendelstein 7-X) and we take part in their scientific exploitation. In these experiments we are analysing physics processes (fuelling, turbulence), which determine the plasma performance of present and future devices. In collaboration with the Plasma Technology group and several EU fusion laboratories we are designing a novel spectroscopy system for ITER, the largest scientific collaboration in the world. Based on our previous developments, we plan to further improve our scientific and technology capabilities to sustain our long term participation in fusion research. Besides other phenomena, we have characterized edge plasma losses induced by turbulence, time evolution of disruptive instability occurring in the edge region (ELMs), which are key element of plasma operation. 

Pellet-plasma interaction 

The primary reason for launching fueling (cryogenic Hydrogen) pellets into the plasma is to increase the plasma density effectively. Our fast camera observations are focused on the drift processes during ablation, which result in the high speed displacement of the material leaving the pellet (secondary cloud/s). The pellet cloud drift is a key issue to economically operate a future fusion power plant, as it can significantly modify the efficiency of refueling. Fueling pellets can also be used to trigger edge plasma instabilities (ELMs), thereby we can also pace and control ELMs by repetitive pellet injection. In our studies we are investigating the parameters that can affect the ELM triggering potential of the pellets, that is, in what pellet- and plasma parameter range the pellet ELM pacing is applicable. Impurity pellets are mainly used to study transport processes, by applying spectroscopic methods. In our studies we are observing at which location and time the impurity tracer material, introduced into the plasma at a specific location, emerges, and we are also studying other effects caused to the main plasma, including the possibility of ELM pacing by impurity pellets. In support of the latter aim, a small, portable pellet injector (“TATOP”) is also under development, which would allow us to conduct very similar experiments at various fusion devices.

Filament (plasma turbulence) studies 

The structures of plasma turbulence, the filaments, elongated along magnetic field lines and having a small extension in the perpendicular direction, can be clearly observed using fast cameras in Wendelstein 7-X stellarator plasmas. The poloidal and radial movement of filaments, as well as their lifetime, have a significant effect on the behaviour of the fusion plasma, therefore we are focusing our studies onto these areas.

Intelligent video diagnostics

Our group is developing a special camera (EDICAM), capable of real-time data processing or even changing its own operational parameters (e.g. frame rate), allowing us to conduct complex measurements and save a significant amount of disk space. Based on parameters set a priori, the EDICAM can detect specific events automatically, and can also transmit signals to other devices in real-time.

Laser Plasma 

Focusing high intensity laser pulses results in the generation of hot dense and warm dense matter. They have basic role in inertial fusion researches, in which KrF lasers are possible alternatives of solid state systems. X-ray spectrometers are to be developed for laser plasma experiments. Ion acceleration, generation of THz radiation and Coulomb explosion of clusters are investigated by KrF lasers.  Nanoplasmas generated inside the clusters, generation of high harmonics and attosecond light pulses are studied by ultrashort laser pulses.