Abstract
X-ray ablation rates have been measured in beryllium, copper-doped beryllium, germanium-doped plastic (Ge-doped CH), and diamondlike high density carbon (HDC) for radiation temperatures T in the range of 160–260 eV. In beryllium, the measured ablation rates range from 3 to 12 mg/cm2/ns; in Ge-doped CH, the ablation rates range from 2 to 6 mg/cm2/ns; and for HDC, the rates range from 2 to 9 mg/cm2/ns. The ablation rates follow an approximate T3 dependence and, for T below 230 eV, the beryllium ablation rates are significantly higher than HDC and Ge-doped CH. The corresponding implied ablation pressures are in the range of 20–160 Mbar, scaling as T3.5. The results are found to be well predicted by computational simulations using the physics packages and computational techniques employed in the design of indirect-drive inertial confinement fusion capsules. An iterative rocket model has been developed and used to compare the ablation rate data set to spherical indirect-drive capsule implosion experiments and to confirm the validity of some aspects of proposed full-scale National Ignition Facility ignition capsule designs.
Highlights
Thermonuclear ignition via indirect-drive inertial confinement fusion1 ͑ICFis the goal of the U.S National Ignition CampaignNICand is one of the primary motivations for the construction of the National Ignition FacilityNIF.2 In indirect-drive ignition experiments, the ϳ500 TW combined peak power of the 192 NIF laser beams will be absorbed in a high-Z enclosureor “hohlraum”͒ that surrounds a low-Z spherical shellor “capsule”͒ containing a layer of solid cryogenic deuterium-tritiumDTfuel
For success at the NIF, it is thought that the spherically imploding rocket must be tuned so that 90– 96% Ϯ 1% of the original ablatorthe percentage of ablated mass depends on ablator type and capsule design detailsis removed at the time when the rocket payloadthe DT fuel plus remaining ablator massreaches a peak implosion velocity, which must be in excess of 350 m / ns
Accurate knowledge of the x-ray ablation rates of low-Z capsule materials is an essential component for successful indirect-drive ICF ignition experiments
Summary
Thermonuclear ignition via indirect-drive inertial confinement fusion1 ͑ICFis the goal of the U.S National Ignition CampaignNICand is one of the primary motivations for the construction of the National Ignition FacilityNIF. In indirect-drive ignition experiments, the ϳ500 TW combined peak power of the 192 NIF laser beams will be absorbed in a high-Z enclosureor “hohlraum”͒ that surrounds a low-Z spherical shellor “capsule”͒ containing a layer of solid cryogenic deuterium-tritiumDTfuel. In indirect-drive ignition experiments, the ϳ500 TW combined peak power of the 192 NIF laser beams will be absorbed in a high-Z enclosureor “hohlraum”͒ that surrounds a low-Z spherical shellor “capsule”͒ containing a layer of solid cryogenic deuterium-tritiumDTfuel. The soft x rays emitted by the hohlraum walls freely traverse the region between the wall and the capsule and are strongly absorbed by the capsule, rapidly ablating the low-Z capsule material. As this ablated material expands outward, the remaining mass is accelerated inward by a spherical, ablationdriven rocket effect. Accurate knowledge of the x-ray ablation rates of low-Z capsule materials is an essential component for successful indirect-drive ICF ignition experiments
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
