Initial measurement of ion nonextensive parameter with geodesic acoustic mode theory

Abstract

The consideration of nonextensivity effects is crucial to the accurate diagnosis of plasma parameters; common plasma nonextensive parameters include electron nonextensive parameter and ion nonextensive parameter, and the former can be measured, while the ion nonextensive parameter cannot be measured yet. Here we show the measurement of ion nonextensive parameter of plasma based on the theory of nonextensive geodesic acoustic modes. We assume that the plasma to be measured can be described by nonextensive statistical mechanics, and on this basis, the nonextensive geodesic acoustic mode theory is established. Utilizing this theory, we have measured the ion nonextensive parameter $${{q}_{{{F}_{\mathrm {i}}}}}= 1.565$$ q F i = 1.565 which cannot be diagnosed even by a nonextensive single electric probe. Our research points out that the proposed measurement method of ion nonextensive parameter may play a role in plasma diagnosis and will help us to grasp the nonextensivity of plasma more precisely. We hope the proposed method of ion nonextensive parameter diagnosis based on the nonextensive geodesic acoustic mode theory can be the starting point of more complex ion nonextensive parameter diagnosis methods. In addition, the measurement of ion nonextensive parameter is closely related to the study of various plasma waves, instabilities, turbulence and abnormal transport, and a defined and quantitative test of nonextensive geodesic acoustic mode theory will bound up deeply with such developments.

Initial analytical theory of plasma disruption and experimental evidence

“…However, the development of nonextensive gyrokinetic theory has brought an opportunity for the study of the analytical theory of the disruption: there are increasing evidences that nonextensive statistical mechanics can be considered as the basis for a more appropriate theoretical framework to describe complex systems whose properties cannot be described by Boltzmann–Gibbs statistical mechanics 17 , 21 . Here, we propose an analytical theory of the plasma disruption based on nonextensive gyrokinetic theory 12 , and give the physical mechanism of the tokamak plasma disruption, which is supported by the experimental data of 59152 shot on T-10 device 15 . We assume that the plasma can be described by nonextensive statistical mechanics, and based on this, we establish the nonextensive geodesic acoustic mode theory 12 , and then, an in-depth analysis of this theory finds that when the ion nonextensive parameter is in a specific interval, a strong wave-particle resonance interaction will occur in the plasma, and the wave will continuously absorb energy from the plasma until the amplitude is too large and the plasma disrupts, that is, a disruption event occurs.…”

“…Here, we propose an analytical theory of the plasma disruption based on nonextensive gyrokinetic theory 12 , and give the physical mechanism of the tokamak plasma disruption, which is supported by the experimental data of 59152 shot on T-10 device 15 . We assume that the plasma can be described by nonextensive statistical mechanics, and based on this, we establish the nonextensive geodesic acoustic mode theory 12 , and then, an in-depth analysis of this theory finds that when the ion nonextensive parameter is in a specific interval, a strong wave-particle resonance interaction will occur in the plasma, and the wave will continuously absorb energy from the plasma until the amplitude is too large and the plasma disrupts, that is, a disruption event occurs. The test process of this tokamak plasma disruption mechanism is presented in Fig.…”

“…In addition, in the tokamak, which is the main device for controlled nuclear fusion, the avoidance of plasma disruption events and the development of more powerful disruption prediction methods will be closely related to such research, such as the utilization of physical quantities like ion nonextensive parameter into the prediction theory 7 , 10 . These initial results illustrate the potential of nonextensive gyrokinetic theory to accelerate advances in fusion-energy science and, more generally, to understand and predict complex physical systems 12 , 17 – 19 .…”

“…On this basis, we establish the nonextensive geodesic acoustic mode theory 11 , 12 , and through in-depth analysis of this theory, we find that the physical mechanism for the disruption of the tokamak plasma lies in it: when the ion nonextensive parameter is in a specific interval, a strong wave-particle resonance interaction will occur in the plasma, and the wave will continuously absorb energy from the plasma until the amplitude is too large and the plasma disruption occurs. At this time, the ion nonextensive parameter measured by method of ion nonextensive parameter diagnosis 12 – 14 is close to , and another accompanying ion nonextensive parameter is close to , which has been confirmed by 59152 shot experimental data on T-10 device. Our results demonstrate that the proposed theory can explain many related phenomena before and after plasma disruption, such as 9 , 10 , 15 , 16 the conversion of low-frequency waves to high-frequency waves, thermal quench, and current quench.…”

“…The resulting thermal and electromagnetic force loads can cause irreparable damage to critical device components 7 . The analytical theory of the tokamak plasma disruption is developed on the basis of the nonextensive geodesic acoustic mode theory 12 , and it is an analytical theory that can give the physical mechanism of the plasma disruption phenomenon. It can be used to guide avoiding the generation of plasma disruptions, and at the same time, it provides more positive information for predicting the occurrence of disruptions, and provides new ideas and new solutions for improving the accuracy of prediction.…”