X-ray spectroscopy of E2 and M3 transitions in Ni-like W

The electric quadrupole (E2) and magnetic octupole (M3) ground-state transitions in Ni-like W46+ have been measured using high-resolution crystal spectroscopy at the LLNL electron-beam ion trap facility. The lines fall in the soft x-ray region near 7.93 angstrom and were originally observed as an unresolved feature in tokamak plasmas. Using flat ammonium dihydrogen phosphate and quartz crystals, the wavelengths, intensities, and polarizations of the two lines have been measured for various electron-beam energies and compared to intensity and polarization calculations performed using the Flexible Atomic Code (FAC).