Matthew R. Gomez

A redesign of the inductively driven transmission line (IDTL) current monitor took place due to the discovery of the discrepancy between the magnetic field measurements of the two B-dots sensors. The IDTL redirects a small amount of Z’s magnetic energy by passively coupling to the magnetic fields of the final power feed of the machine. The monitor is composed of a pair of B-dots oppositely oriented to measure the current that is siphoned through the secondary circuit, enabling common-mode noise cancellation. The redesign of the current monitor will not only enable the diagnostic to measure comparable magnetic fields between the two monitors but also will maintain its compact design while completing common-mode noise elimination. The discrepancy measurements of the magnetic field were identified through simulations (conducted in COMSOL Multiphysics) and calibration measurements that displayed a sensitivity difference by a factor of two. The redesigned IDTL monitor will correct this discrepancy and increase accuracy on the electrical measurements for Z experiments.

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.

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