International Doctoral College in Fusion Science and Engineering
 Thesis catalogue
Modeling and experiments for accurate thermal control of Plasma Facing Components in fusion facility
PhD Code: 2016-DC-06:
Mobility
  • Host institute 1: AM07-Aix- Marseille Université (Home University) - FP8-Institut de Recherche sur la Fusion par confinement magnétique, Saint-Paul-lez-Durance, France (Home Institution)
  • Host institute 2: FP5-Universität Stuttgart (Host University) - FP9-Max-Planck-Institut für Plasmaphysik Garching und Greifswald (Host Institution)
  • Host institute 3: AM04-ITER Organization
Research fields:
  • F1. Tokamak physics for ITER and beyond
Promotor(s):
  • Prof. Christophe LE NILIOT (promotor), Dr. Fabrice Rigollet (mentor)
  • Dr. Marie-Helene Aumeunier (mentor)
  • Dr. Albrecht Herrmann (mentor)
  • Dr. Roger Reichle (mentor)
Contact Person and email: Marie-Helene Aumeunier - marie-helene.aumeunier@cea.fr

Subject description
Background: In magnetic fusion devices, the vessel walls receive high heat and particle loads. The performances of the experiments performed in next step fusion facilities, such as ITER, will strongly depend on the ability to monitor and protect the vessel walls from excessive heat loads. An accurate and well interpreted thermal measurement on plasma facing components (PFCs) offers maximization of the high heat flux in fusion facilities in order to allow for maximum fusion performance while protecting the vessel walls, but also provides data for physics analysis, such as the power distribution on PFCs, or plasma-wall interaction studies such ageing of PFC. Infra-red (IR) measurement is a very appropriate method to fulfill such requirements, by providing thermal images of the PFC under plasma exposure. However, with the introduction of all-metal walls in fusion devices, disturbance phenomena, such as reflections, or inaccuracy on emissivity will affect the interpretation of IR measurements, leading to inacurate PFC temperature estimate and potentially endangering machine safety. The topic of this thesis aims at recovering the true PFC surface temperature from the infrared measurements using a physics-based simulation. This project is made of two complementary workpackages. • The first one is the consolidation of a simulation dealing with all physical processes involved in the measurements: from the source to the pixel response including the effects of reflective and radiative environment (forward simulation). • The second work package will consist in the development of models to analyze and interpret the experimental IR data leading to an accurate estimation of the true surface temperature (deconvolution problem or inverse simulation). Both types of simulations will then be confronted to experimental measurements in fusion devices. The WEST platform (IRFM/CEA, France), aiming at testing ITER grade metallic PFCs in a tokamak environement, provides a unique opportunity to consolidate physical models by comparing simulation results with experimental data. A collaboration is foreseen with the ASDEX Upgrade tokamak (IPP Garching, Germany), also equipped with metallic PFCs. In support to integrated tokamak experiments, added specific measurements will be performed in laboratory to characterize material optical properties (emissivity and reflectivity) and instrumental response. This topic is very important for ITER, in which a wall monitoring system based on IR and visible imaging is foreseen.

Expected outcomes

Objective: The 1st objective of the thesis is to achieve a consolidated synthetic IR diagnostic validated on two experimental facilities: WEST (France) and ASDEX UPGRADE (Germany). This is a key element for the success of the thesis to improve the measurement prediction and to prepare the deconvolution models. The “lessons learned” from these two experimental devices, characterized with different environments (specific tokamak geometry, materials features and imaging systems) will allow to prove and validate the simulation to predict the behavior of future diagnostics in ITER. The first task of the student will be the implementation of synthetic diagnostic of WEST and ASDEX UPGRADE facilities. This requires the adaptation of existing 3D CAD models of the experiments and addition of optical parameters to the model. This will be then combined with existing camera systems. These facilities are equipped with visible and infrared cameras with a wide range of resolution in order to monitor the surface temperature of the plasma facing components (divertor, antenna and inner/outer bumper). The student will participate to the data interpretation during the plasma operation. He will be in charge of the off-line data analysis aiming to compare the simulation results with experimental data in order to adjust and carry out accurate models in the forward simulation. The student will have to acquire a good overview and comprehension of all the involved phenomena ranging from plasma and thermal physics to the computer sciences (data processing) through instrumentation (optics and detector). To do that, the student will work in interaction with a multi-disciplinary team: diagnostics physicist, materials and optical engineers. In parallel, the student will run the synthetic diagnostic to identify the physical parameters that are the most influencing on the quantitative measurement. The second task of the student will be the implementation of synthetic diagnostics for ITER. For that, the student will benefit of the work in-progress in the team for the definition and design of the ITER IR/VIS diagnostic. He will have to work with ITER collaborators to predict the performances and vulnerability of optical diagnostics. The 2nd objective deals with the development and test of methods of deconvolution in order to provide reliable and precise measurement of the surface temperature in reflective environment. The student will be in charge of studying the inversion problem, which is composed of two main stages: (a) the image restoration which consists in reconstructing the original image degraded by the instrumental effects (b) the correction of the contribution of surrounding radiations (parasitic signals) in order to obtain the true temperature. Time line and mobility scheme (research need to be performed for at least six month in two different countries): • 1st year: Implementation of the synthetic diagnostic for WEST and ASDEX Upgrade - consolidation of physical models and the 3D CAD data - implementation of the existing viewing (vis/IR) systems. • 2nd year : (1) Participation in plasma experiments in WEST and ASDEX Upgrade - interpretation and data analysis of IR and visible diagnostics - comparison the the synthetic diagnostic - development of methods for deconvoluting measurement (2) implementation of synthetic diagnotics of ITER • 3rd year: Design and test a data analysis tool able to provide reliable and precise measurement of the surface temperature. Mobility plane proposal (tbc): Months 1-10 IRFM, CEA-Cadarache Months 11-12 Max-Planck-Institut für Plasmaphysik,Garching und Greifswald Months 12-22 IRFM, CEA-Cadarache Months 23-24 Max-Planck-Institut für Plasmaphysik Garching und Greifswald Months 25-30 IRFM, CEA-Cadarache / Aix-Marseille University Months 31-32 Max-Planck-Institut für Plasmaphysik Garching und Greifswald Months 32-36 IRFM, CEA-Cadarache / Aix-Marseille University I

 

 

Original document: 2016-DC-06



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