PROFILE EFFECTS ON IGNITION CONDITIONS IN FUSION PLASMAS

A simple and explicit burn criterion is presented, indicating whether a given temperature profile in a fusion plasma established by, for exa mple, auxiliary heating, will evolve toward ignition or quench under t he competing influence of alpha-particle heating and thermal conductio n losses. The predictions are found to compare well with numerical sim ulations. The result is also used to demonstrate that peaked density a nd/or temperature profiles are advantageous from the point of view tha t the total plasma energy to be established by auxiliary heating in or der to reach ignition is minimized.