Abstract
Laser-based methods are widely used techniques for thermonuclear plasma diagnostics, since they can probe the internal of the plasma, being contactless and non-invasive. The interferometer, the polarimeter and Thomson scattering are the most widespread techniques, providing line-integral information of the electron density and the magnetic field (interferometer–polarimeter) and local information of the electron density and temperature (Thomson scattering). The design of the diagnostics is a fundamental step, which usually requires an iterative process to maximise the performances of the diagnostics and their durability. In the future reactors, such as ITER and DEMO, the working environment will be much challenging, due to the various electro-mechanical, thermal and nuclear loads which may affect the life of the components and degrade the performances of the diagnostics. This work aims to present the modelling of plasma interferometry, polarimetry and Thomson scattering applied to a ray optics code. The model, developed on the COMSOL Multiphysics software, can be easily interfaced with multiphysics problems, allowing the possibility to test the performances of the diagnostics in several conditions.
Highlights
Plasma diagnostics is one of the most important research fields in nuclear fusion, since they are the inputs of the control system, which has the scope to control the confinement stability of the plasma, and they are fundamental to understand and analyse the plasma physics and equilibrium [1,2,3,4,5]
This work aims to present the methodology implemented on the ray optics module of COMSOL Multiphysics to simulate three of the most important laser-based diagnostics in nuclear fusion reactors: interferometry, polarimetry, and Thomson scattering
The numerical model has been implemented in COMSOL Multiphysics, a numerical simulation software which allows an easy interface of different physics
Summary
Plasma diagnostics is one of the most important research fields in nuclear fusion, since they are the inputs of the control system, which has the scope to control the confinement stability of the plasma, and they are fundamental to understand and analyse the plasma physics and equilibrium [1,2,3,4,5]. The scattered radiation intensity is directly proportional to the local electron density, while the scattered spectrum is dependent on the local electron temperature, because of the Doppler effect which occurs due to the interaction of the electromagnetic radiation with the moving electrons [18,19] The design of these diagnostics is a crucial point of the building process of a tokamak since several factors must be considered. A preventive effort to find more reliable and resilient solutions is fundamental to ensure the longest duration of the best performances For these purposes, numerical simulations are decisive in finding the best diagnostic design. This work aims to present the methodology implemented on the ray optics module of COMSOL Multiphysics to simulate three of the most important laser-based diagnostics in nuclear fusion reactors: interferometry, polarimetry, and Thomson scattering. The most important issues and results are resumed in the last section
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