No abstract

Hydrodynamic instability growth of capsule support membranes (or “tents”) has been recognized as one of the major contributors to the performance degradation in high-compression plastic capsule implosions at the National Ignition Facility (NIF) [E. M. Campbell et al., AIP Conf. Proc. 429, 3 (1998)]. The capsules were supported by tents because the nominal 10-μm diameter fill tubes were not strong enough to support capsules by themselves in indirect-drive implosions on NIF. After it was recognized that the tents had a significant impact of implosion's stability, new alternative support methods were investigated. While some of these methods completely eliminated tent, other concepts still used tents, but concentrated on mitigating their impact. The tent-less methods included “fishing pole” reinforced fill tubes, cantilevered fill tubes, and thin-wire “tetra cage” supports. In the “fishing pole” concept, a 10-μm fill tube was inserted inside 30-μm fill tube for extra support with the connection point located 300 μm away from the capsule surface. The cantilevered fill tubes were supported by 12-μm thick SiC rods, offset by up to 300 μm from the capsule surfaces. In the “tetra-cage” concept, 2.5-μm thick wires (carbon nanotube yarns) were used to support a capsule. Other concepts used “polar tents” and a “foam-shell” to mitigate the effects of the tents. The “polar tents” had significantly reduced contact area between the tents and the capsule compared to the nominal tents. In the “foam-shell” concept, a 200-μm thick, 30 mg/cc SiO2 foam layer was used to offset the tents away from the capsule surface in an attempt to mitigate their effects. These concepts were investigated in x-ray radiography experiments and compared with perturbations from standard tent support. The measured perturbations in the “fishing pole,” cantilevered fill tube, and “tetra-cage” concepts compared favorably with (were smaller than) nominal tent perturbations and were recommended for further testing for feasibility in layered DT implosions. The “polar tents” were tested in layered DT implosions with a relatively-stable “high-foot” drive showing an improvement in neutron yield in one experiment compared to companion implosions with nominal tents. This article reviews and summarizes recent experiments on these alternate capsule support concepts. In addition, the concept of magnetic levitation is also discussed.

In indirectly driven Inertial Confinement Fusion implosions conducted on the National Ignition Facility (NIF), the imploding capsule is supported in a laser-heated radiation enclosure (called a “hohlraum”) by a pair of very thin (∼15–45 nm) plastic films (referred to as a “tent”). Even though the thickness of these tents is a small fraction of that of the spherical capsule ablator (∼165 μm), both numerical simulations as well as experiments indicate that this capsule support mechanism results in a large areal density (ρR) perturbation on the capsule surface at the contact point where the tent departs from the capsule. As a result, during deceleration of the deuterium-tritium (DT) fuel layer, a jet of the dense ablator material penetrates and cools the fuel hot spot, significantly degrading the neutron yield (resulting in only ∼10%–20% of the unperturbed 1-D yield). In this article, we present a hypothesis and supporting design simulations of a new “polar contact” tent support system, which reduces the contact area between the tent and the capsule and results in a significant improvement in the capsule performance. Simulations predict a ∼70% increase in neutron yield over that for an implosion with a traditional tent support. An initial demonstration experiment was conducted on the NIF and produced highest ever recorded primary DT neutron yield among all layered DT implosions with plastic ablators on the NIF, though more experiments are needed to comprehensively study the effect of the polar tent on implosion performance.

El presente artículo científico trata el estudio y simulación de un radiador que se basa en un intercambiador de calor tubular de flujo cruzado, el cual tiene un propósito de refrigerar el procesador, tarjeta gráfica de una CPU o diversos hardware en los sistemas de computación. Se realizan diversas simulaciones en el programa ANSYS teniendo varias temperaturas de ingreso que van en rangos desde 75 °C hasta 90 °C y con flujos másicos diferentes.  Los resultados muestran que, al aumentar la temperatura de ingreso del fluido a refrigerar, la salida de este fluido tambien aumenta. Sin embargo, cuando se aumenta el flujo másico existe una merma en el rechazo de calor en los dispositivos computacionales.