D.A. Ovsyannikov

Mathematical methods of plasma vertical stabilization in modern tokamaks

The paper presents the application of modern computational methods for tokamak plasma control system analysis. Several different approaches for feedback controller synthesis are described. General positions of the modern robust analysis theory are briefly formulated. The technique of robust features comparative analysis for feedback controllers is presented. The application of these computational methods is illustrated by the example of the MAST tokamak plasma vertical feedback control system.

BDO-RFQ code and optimization models

The software complex for step-by-step beam dynamics optimization of charged particles in RFQ structure is developed using MATLAB. The RFQ accelerating structure is one of the most common linear accelerators in the world for forming and accelerating high-current beams of charged particles at low injection energies.

Program for scientific and educational investigations on the base of small spherical tokamak Gutta

In Saint-Petersburg state University the modernization of spherical Gutta tokamak is carried out. The aim of the program is to build the research device to study plasma position, shape and current control problems in the tokamak, as well as to assist the scientific and educational programs on various plasma physics problems. Such feature of this device as a relatively small thickness of the vacuum vessel wall made as momentless shell allows changes in the magnetic field in plasma region, to measure the plasma parameters with a minimum delay using electromagnetic diagnostics and changes in toroidal field as necessary.

Analysis and Synthesis of Plasma Stabilization Systems in Tokamaks

Abstract The central problem to be investigated in this paper is plasma control in the toroidal magnetic chamber. It is well known that plasma as an object of control is a mobile non-stable dynamic system with extremely high values of physical parameters, temperature as high as millions centigrade, first of all. This fact rises very high the requirement for electromagnetic capture system control accuracy. The special attention is paid to the stabilization of the plasma to chamber walls gap in some fixed control points. Mathematical methods of stabilizing control design based on modem optimization theory are proposed.

The Experiments of the small Spherical Tokamak Gutta

GUTTA is a small spherical tokamak (R = 16cm, a = 8cm, Ip = 150kA) operating at the St. Petersburg State University since 2004 in the scope of the IAEA CRP “Joint Research using Small Tokamaks”. Main scientific activities on GUTTA include development of new and improvement of existing mathematical models of plasma control, relevant for application on large tokamaks and ITER and verification of them on GUTTA; studies on the ECRH/EBW assisted breakdown and non‐solenoid plasma formation in low aspect ratio tokamak; development of diagnostics; training and education of students.In this paper design properties of Gutta will be presented. Regimes of operation of the tokamak and plasma shape parameters are described and first results of the plasma formation and start‐up studied will be discussed.

Plasma control in tokamaks

This paper discusses and solves problems in the present-day design of the plasma control system in tokamak. The most widespread approach to the design of the magnetic plasma control involves: (i) plasma static equilibrium calculations, (ii) linear models derivation, (iii) synthesis of the controllers for the feedback control of plasma parameters, (iv) control system simulation and (v) control system optimization based on the results of the nonlinear simulations. The good performance of the plasma current discharge in tokamak is achieved by ensuring precise control of the plasma current, position and shape.

Exploring the bunching section of the Neutrino Factory

There exists now a large demand in better neutrino beams in particle physics community. Studying of such beams could reveal interesting and important properties of the observed neutrino oscillations. A high intensity source of a single flavor of neutrinos with reduced backgrounds, a known energy spectrum and intensity is needed for this research. Such intense source of neutrinos is supposed to be provided by the Neutrino Factory. A Neutrino Factory, as proposed, relies on formation and acceleration of ultra-large emittance muon beams with subsequent decay of the muons into a well-collimated, well-characterized neutrino beam. The muon beam creating section of the lattice is originally based on capturing, bunching and phase rotation in an expensive induction linac. A recently proposed different scheme bunches particles and reduces their energy spread in an array of high-frequency rf cavities whose rf frequency varies along the length of the channel. The cost reduction and simplicity of the proposed approach is extensive but is still not at its optimum. Different variations of the design paramaters leading to different properties of the beam and cost are possible. This work explores the approach, variations and develops an optimization scheme for rf parameters based on the underlying beam dynamics.

Robust features analysis for the MAST plasma vertical feedback control system

The paper covers some questions related with the problem of plasma stability in vertical direction in the MAST tokamak. General positions of the modern /spl mu/-analysis theory are briefly formulated. The technique of robust features comparative analysis for feedback controllers is presented. Along with PD controller designed earlier, the optimal LQG controllers are synthesized and used for comparison on their dynamical and robust features.

Mathematical Modeling and Optimization of Beam Dynamics 1

Abstract Nowadays mathematical methods of modeling and optimization are extensively used in many fields of science and technology. Development of specialized software for various applications is of more and more importance. A special class of the problems attracting attention of numerous researches is represented by the problems associated with the beam dynamics formation in accelerators. The paper deals with optimization problems of charged particle beam dynamics in accelerators. The optimization methods are developed for the presented functionals. They are used for solution of various beam dynamics problems in different accelerating and focusing structures. The realization of these methods shows their effectiveness. In this paper we demonstrate the power of new BDO-RFQ code. The comparative analysis of various structures: LEDA-RFQ (USA), IPHI-RFQ (France) and RFQ structure found with BDO-RFQ code (Russia) is given.

Modeling of magnetic field perturbations in electrophysical devices due to the steel reinforcement of buildings

We have proposed an effective method for modeling the steel reinforcement in the buildings for electrophysical devices to take into account the magnetic field perturbation caused by the magnetization of bars. The reinforcement lattice has been represented by one or several layers of a homogeneous isotropic material with preliminarily calculated equivalent (averaged) magnetic properties. Examples of calculating these magnetic properties have been considered using a simplified analytic approach, as well as by the numerical simulation of the magnetic field in a 3D cell of a periodic reinforcement lattice. The efficiency of the method has been demonstrated based on an important practical example of simulating the perturbation of a uniform magnetic field caused by the reinforced slab. The results have been compared with the simulation data based on different approaches.