Spectra of W39+-W47+ in the 12-20 nm region observed with an EBIT light source

We observed spectra of highly ionized tungsten in the extreme ultraviolet with an electron beam ion trap (EBIT) and a grazing-incidence spectrometer at the National Institute of Standards and Technology. Stages of ionization were distinguished by varying the energy of the electron beam between 2.1 keV and 4.3 keV and correlating the energies with spectral line emergence. The spectra were calibrated by reference lines of highly ionized iron produced in the EBIT. Identification of the observed lines was aided by collisional-radiative modelling of the EBIT plasma. Good quantitative agreement was obtained between the modelling results and the experimental observations. Our line identifications complement recent results for W40+ - W45+ observed in a tokamak plasma by Putterich et al (2005 J. Phys. B: At. Mol. Opt. Phys. 38 3071). For most lines we agree with their assignment of ionization stage. Additionally, we present new identifications for some allowed and forbidden lines of W39+, W44+, W46+ and W47+. The uncertainties of our wavelengths range from 0.002 nm to 0.010 nm.