Laser heating and ionization of magnetically confined plasmas in the presence of strong uv and x radiation

A simple one-dimensional model has been developed to describe the propagation of laser radiation into an underdense magnetically confined moderate-Z plasma. A time-dependent Coronal atomic physics code is used to calculate ionization rates and radiative losses. Radiation losses during the ionization process dominate the energy balance and set an intensity-dependent threshold laser fluence for stripping ions such as neon down to a He-like configuration. Attainment of the He-like configuration is marked by a very large reduction in the soft radiation rate plus a sharp increase in the plasma temperature and laser absorption length. This is manifested by the onset of an exponentially increasing K-shell x-radiation rate which has been observed in a small laser-heated neon theta pinch.