He_β emission in dense non-Maxwellian plasmas

The radiation emission of the He_β lines 1s3p ³P₁→1s^{2 1}S₀+hv and 1s3p ¹P₁→1s^{2 1}S₀+hv in dense optically thick and non-Maxwellian plasmas is found to be sensitive to higher multipole orders both for the radiation transitions and the collisional excitation cross sections. It is demonstrated that magnetic dipole and even quadrupole radiation transitions influence not only the absolute radiation line emission but also their qualitative evolution in dense plasmas. The proposed radiation model describes the He_β emission for low- and high-density plasmas and enables diagnostics under typical conditions of both magnetic and inertial fusion plasmas.