Calculations for NIF first quad gas-filled hohlraum experiments testing beryllium microstructure growth and laser plasma interaction physics

Conference · Thu Jan 01 04:00:00 EST 2004

OSTI ID:977629

Goldman, S R ^[1]; Fernández, J C ^[2]; Hoffman, N M ^[3]; Kindel, J M ^[4]; Langdon, A Bruce

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1. Sanford R.
2. Juan C.
3. Nelson M.
4. Joseph M.

The first quad of the NIF provides four nearly collinear f/20 laser beams, which can be treated as a single f/8 beam of maximum energy 16 kJ. We are designing experiments on halfraums in which the composite beam is focused in the plane of the (single) halfraum laser entry hole (LEH) with its symmetry axis collinear with the halfiaum symmetry axis. For most of the calculations, the halfraum diameter is 1.6mm, the LEH is 1.2mm, and axial length is 3.0mm. The incident laser power consists of an early foot followed by a final peak. Peak radiation temperatures for this relatively narrow hohlraum are greater than for wider hohlraums of the same length. Plasma conditions within the halfraum are calculated with Lasnex using azimuthally symmetric, (r,z) geometry, taking into account a polyimide membrane which contains the fill gas (CH{sub 2}) within the halfraum. Estimates for microstructure growth due to the volume crystalline structure within a beryllium slab mounted in the halfraum sidewall are obtained by a post-processor, which applies plasma conditions within the halfraum to an ablatively accelerated, two-dimensional beryllium slab. We present a detailed simulation of the hohlraum conditions resulting from a laser spot of diameter 500 {mu}m, with peak intensity at 3.5 x 10{sup 15} W/cm{sup 2}, a comparison with a simulation with the same power-time profile at an intensity about 1/4 as great, and a comparison with a simulation with more detailed attention to hydro coupling between the gold and gas-fill regions of the hohlraum. We are currently attempting to model the consequences of possible beam filamentation during the pulse.

• Research Organization: Los Alamos National Laboratory
• Sponsoring Organization: DOE
• OSTI ID: 977629
• Report Number(s): LA-UR-04-2994
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ABSORPTION
BERYLLIUM
GEOMETRY
GOLD
LASERS
MEMBRANES
MICROSTRUCTURE
PHYSICS
PLASMA
RADIATIONS
SIMULATION
SYMMETRY
TESTING