Edge plasma studies with turbulence imaging Beam Emission Spectroscopy diagnostics

Nyomtatóbarát változatNyomtatóbarát változat
PhD típus: 
Fizikai Tudományok Doktori Iskola
Dunai Dániel
Email cím: 
Wigner Research Centre for Physics
Senior Research Fellow
Tudományos fokozat: 
Pokol Gergő
Email cím: 
The Institute of Nuclear Techniques, BME
associate professor
Tudományos fokozat: 

In recent years several two dimensional turbulence imaging Beam Emission Spectroscopy (BES) diagnostics have been installed to large fusion experiments by Wigner Research Centre for Physics. Nearly all major European and Asian fusion experiments is equipped with a BES diagnostics, and the Wigner team partly operates these diagnostics and is also responsible for the data evaluation. This gives a unique opportunity to participate in the physics program of leading fusion experiments and also to compare results from different experiments.

In high confinement plasma scenarios (H-mode) violent edge plasma instability called ELM (Edge Localised Mode) appears. The type I ELMy H-mode is the baseline operating scenario for ITER. However, the energy predicted to be released by a type I ELM in ITER is unacceptably high.  The challenge is to produce a non-linear model that can predict when an ELM will be triggered and predict the ELM energy loss.  The present understanding is that type I ELMs result from the peeling-ballooning instability.  In this theory the edge pressure gradient grows in the inter-ELM period until the peeling-ballooning stability boundary is crossed at which point the ELM is triggered.  However, it has been observed on several devices that the experimental profiles can exist near to this stability point for a substantial fraction of the inter-ELM period raising the question: what ultimately triggers the ELM?  Normally there is a large velocity shear at the edge of the H-mode plasma but the non-linear theory (explosive growth stage) of the ELM predicts that the filaments associated with ELMs have to push out through this edge of the plasma and that these filaments can only grow through a region of small velocity shear.  Hence, in order for the ELM to erupt the edge shear velocity has to be reduced. BES diagnostics have unique capabilities to study plasma edge fluctuations and flows.

To characterize ELMs and edge plasma turbulence and compare is the primary aim. A program package that was developed in Wigner RCP is used for this calculation. A part of the work is to develop numerical methods and implement codes to improve the analysis. These codes are then to be tested in artificial data sets and then used in real measurement results.  

Multi device experimental results have to be compared to computational results. The non-linear MHD code JOREK is used these days to model ELM crash dynamics and to predict ELM size. These calculation results have to be confirmed with experimental results. The calculations are planned to be run in collaboration with Culham Centre for Fusion Energy in UK.

Although type I ELMy H-mode operation is the standard scenario, the heat loss will unacceptably high at the divertor tiles. Several alternative scenarios are being developed in these years like small ELM operation scenarios or quiescent H-mode scenarios. The understanding of the physics mechanism, which stabilizes the pedestal in in these scenarios is a key towards their future applicability.

The successful candidate will use existing data analysis codes and develop new algorithms for physics interpretation of the measurement data, as well as taking part in the diagnostic development and operation. As the experiments are in Europe and Asia strong collaboration is necessary with foreign laboratories. Good English language skills are required. In case of interest longer participation in experiments as diagnostic operator is also possible in Germany, UK, Korea or China.


programming skills for data analysis, Effective written and oral communication skills in English 

Munkahely neve: 
MTA Wigner RCP
Munkahely címe: 
1121, Budapest, Konkoly Thege Miklós út 29-33