J. Maxwell, L. Rodriguez and A. Nobile
Materials Science and Technology Division, Los Alamos National Laboratory,
Los Alamos, NM 87545
Heavy ion fusion (HIF) hohlraums require high Z low density foam materials. The close-coupled HIF target (D. A. Callahan-Miller and M. Tabak, Nuclear Fusion 39(7), 883 (1997)) contains a number of low density high Z materials. Laser chemical vapor deposition (LCVD) is being investigated as a means of in-situ synthesis of these materials. With laser LCVD, high Z materials can be deposited directly into the hohlraum, which can reduce the number of assembly steps. LCVD can produce three dimensional low density lattices, and can produce low Z lattices that are doped with high Z elements, as well as pure high Z lattices. This technique also provides the capability to tailor the spatial composition of the material. An LCVD reactor system has been constructed that allows synthesis of fiber arrays and is equipped with an interferometric 2-beam system to simultaneously control fiber length and cross section. Three dimensional rods and helicies of diamond-like carbon and boron have been grown and are currently being characterized. High Z-doped (tungsten and hafnium) low Z (boron) lattices and pure high Z (tungsten and hafnium) lattices will be prepared in the near future. In-situ characterization of the composition can be performed by fourier-transform infrared spectroscopy, so dopant concentration can be controlled in real time.
