Matthew Robert Weis

In magnetized liner inertial fusion (MagLIF), a magnetized sample of gaseous deuterium fuel is “preheated” and subsequently compressed. Preheat is required to allow for the compression to follow a higher adiabat, thus achieving much higher end-temperatures than starting with cold fuel. This temperature enhancement is critical for achieving fusion conditions. To deposit preheat into the target with a high-energy laser, a film-covered laser-entrance hole (LEH) is required, which can confine the deuterium gas while allowing laser energy to reach the fuel. However, this thin-film window absorbs laser energy and can mix with the fuel, which degrades the fusion yield. Cryogenically cooling the deuterium fuel allows the thickness of the LEH window to be significantly reduced. Simultaneously, the implementation of a larger-diameter laser beam waist in the interaction volume allows for a reduction of the laser intensity. By reducing the overall mass of the heated window material and lowering the intensity on target, the average fraction of laser energy that is deposited in the fuel improves from 65% to 83%, without overshooting the useful depth of a MagLIF target. Informed by previous campaigns, the laser pulse length and spot profile were chosen to reduce the intensity below the threshold for losses from stimulated Brillouin scattering. Although the initial expectation was that the dominating contribution to a preheat increase should be the reduced material in the entrance window, it was found that reducing residual laser-plasma-instabilities is even more important for maximizing laser deposition despite the relatively low intensities. The increase in laser-fuel coupling presented here has contributed to the highest performing MagLIF experiments to date.

With the achievement of thermonuclear ignition, there is interest to increase the performance of inertial-confinement-fusion (ICF) systems to reach high fusion yields and high-energy gain for energy-production purposes. One approach to achieve this is magnetic-direct-drive (MDD) ICF, where magnetic fields are used to compress ICF targets to thermonuclear conditions. To study the scaling of MDD ICF to high yields, we performed experiments on the 20-MA, 100-ns Z machine to study the invariant behavior of the magneto-Rayleigh-Taylor instability when changing the magnetic-field drive. Similarity-scaled aluminum cylindrical shells with preseeded axial perturbations were imploded at two different maximum currents: 14.7 and 19.2 MA. Consistent with dynamical similarity within experimental uncertainties, the magneto-Rayleigh-Taylor growth history measured via x-ray radiography exhibits agreement at the 16% level or better for late-time growth factors of 10x to 50x. However, the early instability development is not dynamically similar due to Ohmic-heating effects, which are not conserved by the proposed scaling prescriptions. This Letter exemplifies the application of similarity scaling to rigorously investigate the scaling of MDD ICF to high yields.

We report two magnetized liner inertial fusion (MagLIF) experiments that produced record thermonuclear D–D neutron yields of 2.11×1013 and 2.33×1013. These yields are about a factor of two higher than previous MagLIF results. The experiments achieved ion temperatures of 3.0 and 3.3 keV and stagnation pressures of 1.6 and 1.3 Gbar. The inferred Lawson parameters were χ=0.2 and 0.1, which are the largest reported for MagLIF. The performance increase used a high-aspect-ratio beryllium liner with a dielectric coating and modest increases in preheat energy (∼2.2 kJ), peak current (18.5 MA), and axial magnetic field (15 T). Three-dimensional HYDRA simulations are consistent with the measured liner dynamics and fusion outputs. These results indicate a pathway to higher-yield MagLIF designs using coated, high-aspect-ratio liners and improved input parameters. Simulations further suggest that adding an ice fuel layer could increase yield by up to a factor of 2.5 by reducing liner convergence, instability feedthrough, and mix.

Analytic studies and two-dimensional “clean” radiation-magnetohydrodynamic (rad-MHD) simulations employing dynamical similarity driver-target scaling prescriptions [Ruiz et al., Phys. Plasmas 30, 032708 (2023)] suggest that Magnetized Liner Inertial Fusion (MagLIF) target implosions can scale to >10 MJ DT fusion yields when peak drive current is increased beyond 60 MA. We present results from three-dimensional (3D) rad-MHD simulations of similarity-scaled MagLIF target implosions at peak drive currents ranging from 15 to 40 MA. Simulations in this study suggest that magneto-Rayleigh–Taylor instability (MRTI) growth and feedthrough to the fuel region are more severe at higher drive current scales, which reduces the fusion yield compared to prior analytic and 2D clean simulation predictions. In contrast to standard MagLIF, simulations of current-scaled MagLIF target implosions driven by a dynamic screw pinch (DSP) demonstrate reduced MRTI feedthrough and greater fuel magnetization, resulting in improved thermonuclear performance and enhanced performance scaling with peak drive current. DSP drive enables additional scaling of the liner mass to increase liner radius but maintain implosion time, resulting in higher implosion velocities at the expense of increased susceptibility to MRTI. We present a current- and mass-scaled simulated DSP-MagLIF target implosion at the ∼ 40 MA peak current level that produces ignition scale performance, demonstrating a burn-averaged Lawson ignition parameter above unity and DT fusion yield above 1 MJ.

IFSA 2025 talk on dual current path experiments conducted on the Z facility