Measuring the principal Hugoniot of inertial-confinement-fusion-relevant TMPTA plastic foams
Physical Review E American Physical Society 107:2 (2023) 25206
Abstract:
Wetted-foam layers are of significant interest for inertial-confinement-fusion capsules, due to the control they provide over the convergence ratio of the implosion and the opportunity this affords to minimize hydrodynamic instability growth. However, the equation of state for fusion-relevant foams are not well characterized, and many simulations rely on modeling such foams as a homogeneous medium with the foam average density. To address this issue, an experiment was performed using the VULCAN Nd:glass laser at the Central Laser Facility. The aim was to measure the principal Hugoniot of TMPTA plastic foams at 260 mg/cm3, corresponding to the density of liquid DT-wetted-foam layers, and their “hydrodynamic equivalent” capsules. A VISAR was used to obtain the shock velocity of both the foam and an α-quartz reference layer, while streaked optical pyrometry provided the temperature of the shocked material. The measurements confirm that, for the 20–120 GPa pressure range accessed, this material can indeed be well described using the equation of state of the homogeneous medium at the foam density.Pathways towards break-even for low convergence ratio direct-drive ICF
Journal of Plasma Physics Cambridge University Press 88:3 (2022) 905880314
Abstract:
Following indirect-drive experiments which demonstrated promising performance for low convergence ratios (below 17), previous direct-drive simulations identified a fusion-relevant regime which is expected to be robust to hydrodynamic instability growth. This paper expands these results with simulated implosions at lower energies of 100 kJ and 270 kJ, and ‘hydrodynamic equivalent’ capsules which demonstrate comparable convergence ratio, implosion velocity and in-flight aspect ratio without the need for cryogenic cooling, which would allow the assumptions of 1D-like performance to be tested on current facilities. A range of techniques to improve performance within this regime are then investigated, including the use of two-colour and deep ultraviolet laser pulses. Finally, further simulations demonstrate that the deposition of electron energy into the hotspot of a low convergence ratio implosion through auxiliary heating also leads to significant increases in yield. Results include break-even for 1.1 MJ of total energy input (including an estimated 370 kJ of short-pulse laser energy to produce electron beams for the auxiliary heating), but are found to be highly dependent upon the efficiency with which electron beams can be created and transported to the hotspot to drive the heating mechanism.One-dimensional hydrodynamic simulations of low convergence ratio direct-drive inertial confinement fusion implosions
Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences The Royal Society 379:2189 (2020) 20200224
Abstract:
Indirect drive inertial confinement fusion experiments with convergence ratios below 17 have been previously shown to be less susceptible to Rayleigh-Taylor hydrodynamic instabilities, making this regime highly interesting for fusion science. Additional limitations imposed on the implosion velocity, in-flight aspect ratio and applied laser power aim to further reduce instability growth, resulting in a new regime where performance can be well represented by one-dimensional (1D) hydrodynamic simulations. A simulation campaign was performed using the 1D radiation-hydrodynamics code HYADES to investigate the performance that could be achieved using direct drive implosions of liquid layer capsules, over a range of relevant energies. Results include potential gains of 0.19 on LMJ-scale systems and 0.75 on NIF-scale systems, and a reactor-level gain of 54 for an 8.5 MJ implosion. While the use of 1D simulations limits the accuracy of these results, they indicate a sufficiently high level of performance to warrant further investigations and verification of this new low-instability regime. This potentially suggests an attractive new approach to fusion energy.Energy gain of wetted-foam implosions with auxiliary heating for inertial fusion studies
Plasma Physics and Controlled Fusion IOP Publishing 66:2 (2024) 025005
Energy gain of wetted-foam implosions with auxiliary heating for inertial fusion studies
Plasma Physics and Controlled Fusion IOP Publishing 66:2 (2023) 025005