Hot Spot Evolution Measured by High-Resolution X-Ray Spectroscopy at the National Ignition Facility
Lan Gao, Brian Kraus, K. W. Hill, M. B. Schneider, A. R. Christopherson, B. Bachmann, M. Bitter, P. C. Efthimion, N. Pablant, R. Betti, C. A. Thomas, D. B. Thorn, A. G. MacPhee, S. F. Khan, R. L. Kauffman, D. A. Liedahl, H. Chen, D. K. Bradley, J. D. Kilkenny, B. Lahmann, E. Stambulchik, Y. Maron
Abstract
Evolution of the hot spot plasma conditions was measured using high-resolution x-ray spectroscopy at the National Ignition Facility. The capsules were filled with DD gas with trace levels of Kr and had either a high-density-carbon (HDC) ablator or a tungsten (W)-doped HDC ablator. Time-resolved measurement of the Kr Heβ spectra, absolutely calibrated by a simultaneous time-integrated measurement, allows inference of the electron density and temperature through observing Stark broadening and the relative intensities of dielectronic satellites. By matching the calculated hot spot emission using a collisional-radiative code to experimental observations, the hot spot size and areal density are determined. These advanced spectroscopy techniques further reveal the effect of W dopant in the ablator on the hot spot parameters for their improved implosion performance.