Some Aspects of the TCABR Tokamak Performance: Modeling, Simulations and Experimental Results.

Author(s)

António Manuel Marques Fonseca

• Document type: Master's Dissertation
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Instituto de Física (IF/SBI)
• Defense date: 2000-04-11

Examining board members

Ruy Pepe da Silva; Edson Del Bosco; Jose Henrique Vuolo

• Advisor: Ruy Pepe da Silva

Abstract

In this work, some aspects of the TCABR tokamak are studied. In particular, some points concerned to the plasma breakdown, to discharge characteristics in tokamak mode and to the vertical field system are investigated. A zero-dimensional model has been developed, especially for this work, based on five differential equations involving the ohmic heating circuit and the conservation laws of energy, electrical charge and neutral particles. The model was used for simulating the TCABR plasma discharges. Therefore, time profiles of important plasma parameters like plasma current, loop voltage, electron temperature, electron density and neutral density, were obtained. Also, as a result of the simulations, was verified how the tokamak machine parameters and plasma parameters influence the behavior of the discharges. Some experimental results from the TCABR and TCA were compared with the results of the simulations. A study of the rupture of the plasma was carried out adopting a physical model that includes many physical processes. This model was used to delimit the breakdown region for TCABR tokamak machine and as a tool to understand the experimental data. Experimentally, it was observed that, for TCABR, the rupture occurs for pressures values between 1.10-5 to 3.10-4 mbar, and electric fields values between 2 and 10 V/m. The ratio electric field-pressure (E/p), in the rupture region, is between 3.107 and 5.108 V.m-1.bar-1. For the control system of the vertical field we obtained some transfer functions mainly for the non-linear blocks of the system that have been used in the experimental tests. A computer program was developed to obtain the map of the magnetic vertical field lines and the index of curvature of the field. Finally it was verified that, in the center of the vessel, the ratio between the magnetic vertical field to the electric current that flows in the vertical coils is, 3.5.10-5 T/A and the index of curvature of the field is ~0.45. (AU)