RECENT RESEARCH PROJECTS

Our main goal is to develop a platform for the OMEGA-60 laser facility to study MHD effects in cylindrical implosions at regimes of large magnetic pressure and magnetization. 2-D simulations using the MHD code GORGON predicted that a seed B-field of 30 T can be compressed to ~30 kT owing to flux compression when imploding the cylindrical target. As a result, the characteristic conditions of the compressed core are expected to be modified by the large magnetization and magnetic pressure thereby reached at maximum compression. On a few previous magnetized cylindrical compressions at the OMEGA-60 facility, the effect of the compressed B-field was investigated using neutron measurements only. However, the neutron yield in cylindrical implosions is rather low (on the order of 10⁸-10⁹) and e.g. a small target variation can induce very large yield fluctuations, therefore strongly limiting a clear interpretation of the results. Alternatively, we propose to use Ar/Kr dopant(s) in the D₂ gas. As the core conditions are modified by the compressed magnetic field, we expect to observe systematic changes in the dopant emission spectra between unmagnetized and magnetized shots. Carrying out such magnetized implosion experiments will advance the modeling of B-field compression and diffusion, and the benchmarking of atomic kinetics and line shape calculations in magnetized plasmas relevant to complex ICF-related experiments with embedded B-fields. Simulations must include extended-MHD effects, which represent the transport of energy and magnetic flux in a plasma. Magnetized plasmas are thought to exhibit complex behavior in the electron population and, above resistive-MHD, extended-MHD additionally accounts for temperature gradient-driven transport—such as the Nernst term moving magnetic fields down electron temperature gradients—and electric-current-driven transport—such as the Hall term moving magnetic fields with the flow of charge. In this context, our goal is to obtain clear experimental data that will facilitate benchmarking of MHD codes and consequently help the modeling of magnetized HED experiments. Moreover, the interpretation of spectral emission measurements from complex magnetized experiments requires novel and accurate modeling of the detailed atomic and radiation transport physics. In this project, we are investing significant efforts to mature the spectroscopy diagnostic techniques for magnetized HED experiments.

In this project, we investigate promising concepts to enhance the peak cutoff energy and flux of short-pulse laser-accelerated ions via the synergetic effects of target transparency and continuous field acceleration. Recent studies using multi-picosecond pulses with modest laser intensities have shown promising results. Experimentally demonstrated proton energies of up to 30 MeV at quasi-relativistic intensities and 50 MeV with the double pulses are far beyond energies predicted by the well-established TNSA model scaling and experimental results for the same laser intensity with sub-ps pulses. The laser pulse interacting with an expanding under-dense plasma for multi-ps duration generates a 'super-ponderomotive' electron population and this is key to sustain electric fields for proton acceleration. This continuous ion acceleration can be further improved with the effect of target transparency by using multi-ps pulses and ultra-thin foils, suggesting a new approach to efficient ion acceleration.

The dynamics involved become more complex as the laser energy and resulting beam current increase, and as beam pulse length increases. We have been awarded OMEGA EP laser time at the Laboratory for Laser Energetics to use high energy short pulse laser beams to extend previous proton focusing/transition studies to 10 ps pulse duration. We will be collecting detailed information about the forces that affect such beams, utilizing the second EP beam to produce protons to probe conditions set up by the first EP laser beam. Energy deposition and heating of a solid foil (dense plasma) by the focused proton beam will also be characterized by measuring its induced K-shell fluorescence emission via x-ray imaging and spectroscopy techniques. Our goal is to extend our understanding of the High-Energy Density physics involved facilitating optimal source designs for various medical and energy applications and eventually experiments like NIF integrated proton fast ignition experiments with the Advanced Radiographic Capability (ARC) beam.

Despite progress, significant engineering and design challenges remain before fusion energy can transition from experiments to commercially viable power plants. A coordinated effort between academia, national laboratories, and industry is essential. The Center has adopted a multidisciplinary approach to address grand challenges in the research areas of 1) materials under extreme conditions, 2) diagnostics under extreme radiation, and 3) the tritium fuel cycle. To tackle these challenges, this Center unites experts in state-of-the-art theory, material synthesis and fusion performance testing, and diagnostics spanning both magnetic and inertial fusion. It also leverages the advanced fusion research facilities and equipment managed by participating institutions to enable the development of cutting-edge fusion technologies.

The challenges in fusion energy transcend traditional disciplinary boundaries of physical sciences and engineering, requiring an integrated approach to education and training. The Center uses a multi-front approach offering a comprehensive series of courses on fusion energy, materials, diagnostics, radiation, tritium handling and fundamentals of fusion power plants. This program is a valuable resource for students and researchers across the University of California system and by providing access to these specialized courses, we aim to equip the next generation of fusion researchers and engineers with the knowledge and skills needed to drive innovation in this rapidly evolving field in collaboration with major fusion companies in the country.

Our team recently completed the first integrated PFI campaign at the OMEGA laser facility to measure the temperature increase in the compressed core due to heating by protons and visualize where the protons deposited their energy in the compressed plasma. In these experiments, an intense proton beam was generated from a curved hemispherical foil embedded within a cobalt-coated gold cone using the OMEGA EP short-pulse beam, which was then focused and guided into a copper-doped CH spherical capsule imploded by the OMEGA long-pulse beams.

We have also been awarded two more joint shot days in FY26/27 to conduct additional integrated PFI experiments on OMEGA. We plan to utilize an identical target configuration and still primarily rely on x-ray spectroscopy to diagnose proton heating in the compressed core, but with reduced OMEGA EP pulse duration to probe higher laser intensities compared to our previous experiments. Together, these investigations represent notable contributions to our knowledge of PFI, have established a framework for evaluating the robustness of the PFI concept, and have advanced the experimental study of warm dense matter.