Open AccessEffects of low Z impurities during the startup phase of a large tokamak
Author(s) -
R. J. Hawryluk,
J. A. Schmidt
Publication year - 1976
Language(s) - English
Resource type - Reports
DOI - 10.2172/4066502
Subject(s) - tokamak , plasma , impurity , ionization , ohmic contact , atomic physics , materials science , phase (matter) , volume (thermodynamics) , energy balance , current (fluid) , nuclear engineering , mechanics , physics , thermodynamics , nuclear physics , ion , nanotechnology , quantum mechanics , engineering , layer (electronics)
The requirements placed on a tokamak ohmic heating system (i.e. loop voltage) to initiate the plasma become more severe as the size increases because of the current density decrease. During the startup phase even small concentrations of low Z impurities can affect the plasma energy balance very substantially and have very important effects on the evolution of the discharge. The startup phase has been studied using a simple zero dimensional computer code. Because the dominant energy loss mechanisms during startup, radiation, and ionization are a volume effect, the zero dimensional code was adequate to treat this phase. The results of this study which have been applied to TFTR indicate that the plasma evolution is a sensitive function of the applied loop voltage, impurity concentration, initial filling pressure and the manner in which gas is fed into the discharge. (auth