Time-Dependent Nuclear Measurements of Mix in Inertial Confinement Fusion

Abstract

We report on observations of a series of highly-structured ionospheric plasma turbulence over Arecibo on the nights of 22/23 and 23/24 July, 2006. Incoherent scatter measurements by Arecibo radar, airglow measurements using MIT PSFC's all-sky imaging system (ASIS), together with TEC measurements from GPS satellite network provide well-integrated diagnostics of turbulent plasma conditions. Two kinds of turbulent structures were seen as slanted stripes and filaments/quasi-periodic echoes on the range-time-intensity (RTI) plots of radar measurements. Detailed analyses of radar, airglow, and GPS data allow us to determine the drift velocity/direction, the orientation/geometry, and the scale lengths of these plasma turbulence structures. They are large plasma sheets with tens of kilometer scale lengths, moving in the form of traveling ionospheric disturbances (TIDs) southward within the meridional plane or westward in zonal plane at tens of meter per second. The signatures of observed TIDs indicate that they were triggered by internal gravity waves that had reached the altitudes of ionospheric F region. All possible sources producing gravity waves have been examined. We rule out solar/geomagnetic conditions which were quiet, and the atmospheric weather anomalies which were absent, during the period of time for our experiments. It is found that the heat wave fronts, which occurred in US, were plausible sources of free energy generating intense gravity waves and triggering large plasma turbulence over Arecibo. In other words, anomalous heat sources can be responsible for the occurrence of intense space plasma turbulence all over the world. The reported research suggests that global warming may affect the space weather conditions significantly. Further GPS data analysis is outlined as our future efforts to verify some predictions based on the current research outcomes. Simulation experiments can be conducted at Gakona, Alaska using the powerful high-frequency active auroral research programs (HAARP) heating facility, to generate gravity waves for the controlled study of concerned intriguing phenomenon.

The effect of shock dynamics on compressibility of ignition-scale National Ignition Facility implosions

“…20 , and the observed downshift can be related to the implosion areal density (ρR) using a charged-particle stopping theory 21 . The shock yield observed (8.7 × 10 7 ) is related to the final merged shock strength 16,22 . The center-of-mass radius (R cm ) of the imploding shell is inferred in addition to ρR using 1-D modeling discussed in Section II.…”

“…These escaping protons are used to probe the in-flight characteristics of the shell at a radius of ∼ 250µm. D 3 He proton spectroscopy is a well-developed technique for diagnosing inertial fusion implosions [12][13][14][15][16] at the OMEGA laser facility 17 and now at the NIF. Table II for more information).…”

“…The shock preferentially heats ions over electrons 16 and in this Guderley model they are assumed to be uncoupled (τ ei long compared to dynamical timescales) 41 . We can interpret the shock proton yield via a simple model based on the Gudelery spherically-imploding shock solution 16,22 .…”

“…We can interpret the shock proton yield via a simple model based on the Gudelery spherically-imploding shock solution 16,22 . The Guderley model gives hydrodynamic profiles in a self-similar solution as a function of a single shock strength parameter, ξ.…”

Direct-drive inertial confinement fusion: A review

“…Li et al also found that the mix increased with convergence ratio. Rygg et al 289 used the time dependence of the proton yield from similar targets to show that the neutron-production time is delayed, consistent with the amount of mix increasing in time. Wilson et al 290 carried out similar experiments but with the shell filled with (nearly) pure tritium.…”