Diagnosing the properties of dynamic Hohlraums with tracer spectroscopy (invited)

A dynamic Hohlraum (DH) is formed when arrays of tungsten wires driven by a high current pulse implode upon a cylindrical foam target. At impact, the wire plasma launches a radiating shock in the foam and confines the radiation. This sequence of events forms an intense, similar to 200 - 250 eV Planckian x-ray source which is a prime candidate for indirect drive inertial confinement fusion. In recent DH experiments on the 20 MA Z facility, Al and MgF2 tracer layers were embedded in the cylindrical foam targets to provide K-shell lines in the keV spectral region for diagnosing the conditions of the interior Hohlraum plasma. Time-resolved K-shell spectra of both Al and Mg show mostly absorption lines. These data can be understood and quantitatively analyzed with detailed atomic and radiation transport models. The analyses show no evidence of intrinsic differences in the properties of the tops and bottoms of the Hohlraums. The interiors of the cylindrical Hohlraums are found to be hotter than the ends. (c) 2006 American Institute of Physics.