Non-statistical population distributions for hydrogen beams in fusion plasmas

Most atomic models for neutral hydrogen beams in fusion plasmas assume a statistical (Boltzmann) distribution of populations for excited states with the same principal quantum number n. Here we analyze population distributions for the excited magnetic sublevels of a beam under typical conditions of existing and future fusion devices. The collisional–radiative model NOMAD based on completely m-resolved parabolic states up to n = 10 is used to study this problem. The model utilizes new proton-impact excitation data calculated with the atomic-orbital close-coupling method and the Glauber approximation and takes into account electric-field-induced ionization from highly excited states. Our simulations show that the statistical assumption for a specific n is generally not valid for typical fusion conditions due to radiative processes and strong field ionization. The deviation increases considerably for higher beam energies and stronger magnetic fields. The calculated line intensities of σ and π components and beam-emission parameters are discussed in detail. (paper)