Measurement And Analysis Of The Radiated Power For The Ohmic Discharges In The J-text Tokamak

There are electrons, ions and neutral atoms in the Tokamak plasma. The interactions between these particles as well as these particles and the electromagnetic fields often produce electromagnetic wave radiation. When the plasma is in thermodynamics equilibrium or local thermodynamics equilibrium state, that is, the particles'(molecule, atom, ion, electron etc.) distribution of the system can be described by the Boerziman distribution under a certain temperature, the electromagnetic radiation is called heat radiation. It is an important way of the transport and diffusion for the energy in the high-temperature plasma. Through the measurement of radiation, the energy balance can be understood well. Furthermore, the composition, ionization state, temperature and density can be obtained, so the radiation measurement is a basic diagnosis.The thesis introduces the design and application of the radiated power measurement system in the J-TEXT tokamak, as well as the experimental results and the physical analyses. The major contents are as follows:(1) At the current temperature, the dominated wavelength of the radiation is between extreme Vacuum ultraviolet (XUV) and soft X-ray. According to the density, temperature and other parameters of the J-TEXT Tokamak, the main wavelength of the radiation and the total radiated power can be estimated. Then based on these parameters, the appropriate detectors (photodiodes) and the appropriate receiving optical path can be chosen and the radiated system can be designed. The system includes poloidal arrays and toroidal arrays. The former ones are intended to measure the radiated power, radiated power profiles and the radiation evolution process in the poloidal direction. The latter ones, which are in nine small ports can study the radiation symmetry (especially the process of the disruption and the disruption mitigation) of the toroidal direction and proof the completeness of the magnetic surface.(2) In the J-TEXT tokamak ohmic discharges, the total radiated power is about20%-80%of the ohmic power in the current flattened stage, so the total radiated power play an important role in the power balance. The radiated power profiles got by the poloidal arrays can reflect the temperature profiles of the plasma and the composition, proportion of impurities. In the J-TEXT discharges, there are two kinds of profiles:peak shaped profile and hollow shaped profile. For the peak shaped profile, the radiated power is about30%of the ohmic power at the center of the plasma(r=0-0.2a), which mainly comes from the impurity line radiation (Fell, etc.); at the boundary (r=0.7a-a), the radiated power is about15%.For the hollow radiation profile, the radiated power is about15%at the center (r=0-0.2a) and at the boundary, the radiated power is about20%, which are mainly provided by the light impurities.(3) The photodiode is applied in the J-TEXT tokamak. Its response time is0.5μs (AXUV16ELG), therefore the fast MHD instability information can be obtained by analyzing the radiation signals. It is found that the radiation signals are modulated by the sawtooth and other MHD instabilities in the poloidal direction and toroidal direction. When the Mirnov oscillation is strong, the magnetic island (main the m/n=2/1) location can be deduced by the radiation signals.(4) In the current discharges, the disruption is mainly caused by tearing mode instability. Among them, the m/n=2/1mode dominates, accompanied by m/n=3/1mode. In this kind of disruption, the radiated power doesn't change obviously before the disruption. But after the disruption, it significantly increases. This indicates that the radiation is not a trigger mechanism but a channel of energy loss. According to the estimation, the radiated energy is about10%of the thermal energy during the thermal quench (TQ).(5) In the static magnetic perturbation field experiments (SFX) of the J-TEXT tokamak, it is found that after the perturbation field applied, the core radiation intensity decreases but the edge radiation intensity increases. This may be because the confinement gets worse and the temperature changes. In the noble gas (He, Ne, Ar) injection experiments, the radiated power doesn't increase obviously by gas puffing. However, when the gases are injected by supersonic molecular beam (SMBI), the radiated power increases obviously and the increased rate changes as the Zeff, pressure and the gases pulses.