Study of Globus-M Tokamak Poloidal System and Plasma Position Control

In order to provide efficient performance of tokamaks with vertically elongated plasma position, control systems for limited and diverted plasma configuration are required. The accuracy, stability, speed of response, and reliability of plasma position control as well as plasma shape and current control depend on the performance of the control system. Therefore, the problem of the development of such systems is an important and actual task in modern tokamaks. In this study, the measured signals from the magnetic loops and Rogowski coils are used to reconstruct the plasma equilibrium, for which linear models in small deviations are constructed. We apply methods of the H∞-optimization theory to the synthesize control system for vertical and horizontal position of plasma capable to working with structural uncertainty of the models of the plant. These systems are applied to the plasma-physical DINA code which is configured for the tokamak Globus-M plasma. The testing of the developed systems applied to the DINA code with Heaviside step functions have revealed the complex dynamics of plasma magnetic configurations. Being close to the bifurcation point in the parameter space of unstable plasma has made it possible to detect an abrupt change in the X-point position from the top to the bottom and vice versa. Development of the methods for reconstruction of plasma magnetic configurations and experience in designing plasma control systems with feedback for tokamaks provided an opportunity to synthesize new digital controllers for plasma vertical and horizontal position stabilization. It also allowed us to test the synthesized digital controllers in the closed loop of the control system with the DINA code as a nonlinear model of plasma.     

Tearing Mode Behavior in the Globus-M Spherical Tokamak Plasma

Physics of Atomic Nuclei - The 2/1 tearing mode instability during the plateau phase of the plasma current time evolution has been observed since the start of the Globus-M spherical tokamak...     

A Study of the Near-Wall Plasma of the Globus-M Tokamak Using an Array of Divertor Langmuir Probes

Technical Physics - An array of ten built-in divertor probes was installed on the lower dome of the Globus-M spherical tokamak. It was used to measure the profiles of the floating potential,...     

托卡马克高约束模边缘等离子体不稳定性研究

托卡马克高约束模运行可大幅提高磁约束核聚变等离子体约束品质,该模式下的等离子体不稳定性研究对于控制约束和保护装置有重要意义。本文主要介绍了高约束模及其边缘等离子体不稳定性的研究概况,并重点介绍了中国环流器二号A托卡马克装置上关于高约束模转换、边缘局域模特征和控制方法、台基区不稳定性和台基饱和机制等方面的研究进展。研究结果表明,实验上有望通过粒子和射频波注入等外部激励的方法,影响台基区等离子体湍流,进行控制台基动力学演化以及ELM,实现既保持高约束又降低高热负荷的等离子体稳态运行。     

Spectroscopic Diagnostic of the Peripheral Plasma in the Globus-M2 Tokamak with the Injection of Neutral Helium

JETP Letters - The diagnostic of the peripheral plasma parameters in terms of the relation of lines of neutral helium is included in the diagnostic complex of the tokamak Globus-M2. The first...     

Theoretical Study of ECRH Heating Of HL-2A Tokamak Plasma

Electron cyclotron resonance heating （ECRH） is one of the main auxiliary heating schemes for the HL-2A tokamak. Routinely, the ohmic heating can provide a heating power about 300-450 kW in this device （ estimated from that the total toroidal current is about 300 kA while the totoidal voltage is 1-1.5 V）. The total power for the ECRH now is 1 MW and in future 2 MW.     

基于神经网络的托卡马克能量约束时间预测

使用机器学习理论中的神经网络方法,根据通用逼近原理对能量约束时间的复杂函数进行逼近,采用托卡马克装置的典型实验数据,设计一种组合结构的神经网络.通过大量的调参试验,给出一套性能最好的参数组合,并与传统幂指数形式的多元线性回归方法进行准确性和数据集迁移能力的比较.结果表明:神经网络模型对于能量约束时间的预测准确率更高,回...     

Energy Confinement Dynamics and Soft X-Ray Spectra in Experiments on ECR Plasma Heating in the L-2M Stellarator at Heating Powers to 1 MW

Bulletin of the Lebedev Physics Institute - The shape of soft X-ray spectra and energy confinement dynamics is studied in experiments on central ECR heating with a power to 1 MW using the L-2M...     

First Heat and Particles Transport Study in the Globus-M2 Spherical Tokamak with Neutral Beam Injection at the Current Ramp-Up

Technical Physics - The article presents the results of studying the transfer of heat and particles in the Globus-M2 spherical tokamak in discharges with neutral injection at the current ramp up....     

Study of Plasma MHD Equilibrium in HL-2A Tokamak

1 Introduction In an axisymmetric toroidal system, the MHD equilibrium G-S equation can be written as：     

Study of Density Behavior During LHCD and IBW Heating in the HT-7 Superconducting Tokamak

A new method using special shape parameters has been introduced to study density behavior with synergy of lower hybrid current drive (LHCD) and ion Bernstein wave (IBW) heating in the HT-7 superconducting tokamak. During the synergy of the LHCD and IBW heating an improved confinement plasma was achieved, and the electron density was increased and peaked.     

Study of Plasma MHD Equilibrium in HL-2A Tokamak

In an axisymmetric toroidal system, the MHD equilibrium Grad-Shafranov equation can be written as     

On an Unconventional Approach to the Improvement of Plasma Confinement in Tokamaks

JETP Letters - A conceptual proposal has been suggested to improve the confinement of a turbulent plasma in tokamaks with the use of discharges with large safety factors qL at the plasma...     

Low-Threshold Parametric Excitation of Electron Plasma Waves Localized in the Edge Transport Barrier of a Tokamak during Electron Cyclotron Resonance Heating of a Plasma

JETP Letters - The possibility of the localization of longitudinal waves in the intermediate frequency range in the edge transport barrier of a toroidal nuclear fusion facility is discovered. It is...     

Numerical Study of Plasma Discharges in KTM Tokamak in Autumn Campaign 2019

Physics of Atomic Nuclei - The work presents some simulation results of discharge scenarios at the KTM facility during the autumn campaign 2019. The parameters for providing the plasma breakdown...     

Spectroscopic Study of Laser-Induced Cu Plasma With and Without the Confinement of a Substrate

Optical emission spectroscopic studies have been carried out on the laser-induced copper plasma generated in the process of laser-driven flyer (with the substrate confinement). The copper plasma in the air (without the substrate confinement) has also been researched in order to know the differences between the plasma with the confinement and that without the confinement. The plasma is assumed to be in local thermodynamic equilibrium. The result shows that, under the same laser fluence, the plasma exists a longer time with the confinement. The time-resolved electron temperature and density with the confinement are higher than those with no confinement. The substrate deposited with Cu foil plays an important role in enhancing the temperature and the density of the plasma. The electron temperature and density with confinement increase with a larger scope as the laser fluence increases than that with no confinement.