Measurements of the temperature and velocity of the dense fuel layer in inertial confinement fusion experiments
Abstract not provided.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
Engineering topics
Gopalaswamy, V.
Publications and source records attributed to Gopalaswamy, V..
Enhanced laser-energy coupling with small-spot distributed phase plates (SG5-650) in OMEGA DT cryogenic target implosions
Cryogenic deuterium–tritium ice target implosions on OMEGA with new small-spot (SG5-650) distributed phase plates (DPPs) achieved an (11 ± 4)% increase in energy coupling compared to implosions with larger-spot SG5-850 DPPs by decreasing the ratio of the laser spot diameter to the target diameter from 0.93 to 0.75. The SG5-650 DPPs provide a focus spot size of 674 μm, which is defined as the diameter that encircles 95% of the measured beam energy compared to 834 μm for the SG5-850, which are the standard DPPs in cryogenic target implosions on OMEGA. The hydrodynamic efficiency, defined as the ratio of the kinetic energy in the imploding shell to the laser energy, increased from 4.5% to 5.0% based on radiation-hydrodynamic calculations benchmarked to shell trajectory and bang-time measurements. Furthermore, the higher coupling came with a trade-off of an increased hot-electron production as well as increased hydrodynamic instabilities seeded by a larger mode-10 amplitude from the beam port geometry, both of which may have reduced the fusion neutron production and areal density.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
High yields in direct-drive inertial confinement fusion using thin-ice DT liner targets
In this work, we report simulation results that suggest record neutron yields above 3 x 10 14 can be achieved in laser-driven fusion on OMEGA by imploding large-outer-diameter targets (~1010μm) containing ice layers as thin as 34μm. Historically, the performance of thin and fast capsules is thought to be highly degraded by hydrodynamic instabilities. We present pulse designs that push implosion velocities above 650 km/s while maintaining enough ablative stabilization and low enough in-flight aspect ratios to survive the acceleration phase. We show these targets also possess improved stability during deceleration stemming from augmented core temperatures and low fuel convergence.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
Using statistical modeling to predict and understand fusion experiments
Over 300 cryogenic layered direct-drive inertial confinement fusion implosions have been successfully executed on the OMEGA Laser System in the last decade. However, extracting sufficient understanding from these experiments to develop new designs or to identify or mitigate degradation sources remains challenging. Recently, a statistical modeling approach was developed to successfully design and predict improved implosion experiments on OMEGA. Here, we show that one-dimensional simulations can be used to predict the outcomes of systematically perturbed three-dimensional simulations and that this statistical modeling approach can be used to identify or rule out physical mechanisms for some of the degradation sources observed on the OMEGA Laser System for direct-drive cryogenic inertial confinement fusion. In this instance, we investigate the fusion yield dependencies on the ion temperature asymmetries and laser beam size observed in experiments by comparing with trends in three-dimensional synthetic simulation databases. Using the statistical model on these systematically perturbed simulations, we find that the statistically inferred dependency on the measured ion temperature asymmetries is well explained by imposed ℓ =1 modes. However, we find that the dependency on the laser beam size is only dominated by the illumination non-uniformity for some extreme cases.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗