Measurements of Au Ionization Using L- and M-shell X-ray Emission

An experiment has been done at the NIF using a buried layer platform to study the radiative properties of non-local thermodynamic equilibrium (NLTE) gold plasma at an electron temperature of ∼3 keV and an electron density of ∼10²¹cm^-3. The targets used consisted of a 625 μm diameter, 1900 Å, thick dot with a 1:2.25 atomic mix of gold and zinc in the center of a 2500 μm diameter, 10 μm thick beryllium tamper. Lasers heat the target from both sides for 4.0 ns. The size of the emitting volume vs time was measured side-on with x-­ray imaging. The radiant x-­ray power was measured with a low-­resolution, absolutely calibrated x-­ray spectrometer (DANTE). The Au L-shell and the Zn K-shell were measured simultaneously and time resolved with the same spectrometer and streak camera. A second spectrometer/streak camera was used to measure the M-shell emission of the Au. The electron temperature was inferred from the measured zinc K-shell emission. The ionization balance of the gold is inferred from the measured L- and M-shell emission of the gold. A comparison is made between the sensitivity of the K- and L-shell emission to conditions of the thermal plasma.