Foot-Pulse Radiation Drive Necessary for ICF Ignition Capsule Demonstrated on Z Generator


Summary form only given. Implosion and ignition of an indirectly-driven ICF capsule operating near a Fermi-degenerate isentrope requires initial Planckian-radiation-drive temperatures of 70-to-90 eV to be present for a duration of 10-to-15 ns prior to the main drive pulse. Such capsules are being designed for high pulsed-power generators such as X1. This foot-pulse drive capability has been recently demonstrated in a NIF-sized (6-mm 1=7-mm), gold hohlraum, using a one-sided static-wall hohlraum geometry on the Z generator. The general arrangement utilized nested tungsten-wire arrays of radii (mass) 20 mm (2 mg) and 10 mm (1 mg) that had an axial length of -10 mm. The arrays were driven by a peak current of -21 MA and were made to implode on a 2-μm-thick Cu annulus (mass=4.5 mg), which had a radius of 4 mm and was filled with a low-density CH foam, all centered about the z-axis. The gold hohlraum was mounted on axis and above the Cu/foam target. A 2.9-mm-radius axial hole between the top of the target and hohlraum permitted the X-rays generated from the implosion to enter the hohlraum. The radiation within the hohlraum was monitored by viewing the hohlraum through a 3-mm diameter hole on the lateral side of the hohlraum with a suite of diagnostics. The radiation entering the hohlraum was estimated by an additional suite of on-axis diagnostics, in a limited number of separate shots, when the hohlraum was not present. Additionally, the radiation generated outside the Cu annulus was monitored, for all shots, through a 3-mm diameter aperture located on the outside of the current return can



Keywords and Phrases

21 MA; 70 to 90 EV; Au; Cu; Cu Annulus; Fermi-Degenerate Isentrope; ICF Ignition Capsule; NIF-Sized Au Hohlraum; Planckian-Radiation-Drive Temperature; W; X-Rays Generation; Z Generator; Z Pinch; Exploding Wires; Foot-Pulse Drive Capability; Foot-Pulse Radiation Drive; High Pulsed-Power Generators; Ignition; Implosion; Low-Density CH Foam; Nested W-Wire Arrays; On-Axis Diagnostics; One-Sided Static-Wall Hohlraum Geometry; Plasma Density; Plasma Inertial Confinement; Plasma Temperature

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Article - Conference proceedings

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© 1999 Institute of Electrical and Electronics Engineers (IEEE), All rights reserved.

Publication Date

01 Jan 1999