Spectroscopy of diagnostically important magnetic-dipole lines in highly charged 3dn ions of tungsten

An electron-beam ion trap (EBIT) is used to measure extreme ultraviolet spectra between 10 and 25 nm from highly charged ions of tungsten with an open 3d shell (W-XLVIII through W-LVI). We found that almost all strong lines are due to the forbidden magnetic-dipole (M1) transitions within 3d(n) ground configurations. A total of 37 previously unknown spectral lines are identified using detailed collisional-radiative (CR) modeling of the EBIT spectra. A level-merging scheme for compactification of rate equations is described. The CR simulations for Maxwellian plasmas show that several line ratios involving these M1 lines can be used to reliably diagnose temperature and density in hot fusion devices.