Jens Schwarz

We present a generalized theoretical framework for Second-Harmonic Orthogonally Polarized Dispersion Interferometry (SHOP-DI) and the diagnostic’s implementation for time-resolved electron areal-density measurements of pulsed-power Magnetically Insulated Transmission Line (MITL) electrode plasmas. The theoretical treatment extends standard SHOP-DI analysis by deriving the detected intensity response for arbitrary second-harmonic polarization angles, establishing a detector-bandwidth-limited criterion for the maximum trackable rate of change in electron areal density, modeling a counter-rotating phase-control-window system that enables reproducible phase-offset calibration, and introducing a power-normalized analysis method which separates refractive-index-induced phase shifts from static channel imbalance and common-mode optical-power fluctuations. Guided by these developments, the diagnostic was redesigned for operation on Sandia National Laboratories’ (SNL’s) 1 MA Mykonos accelerator, where MITL plasmas evolve on nanosecond time scales within sub-mm Anode–Cathode (A–K) gaps. The implemented system combines a 2 GHz bandwidth, corresponding to a maximum measurable areal-density rate of change of 4.8 × 1016 1/cm2/ns, with an overlapping 1/e2 probing beam waist diameter of ∼100μm. Improved optical throughput and optomechanical stiffness enabled the experiments at Mykonos to achieve a noise-limited 1σ areal-density uncertainty of 1.6 × 1014 1/cm2. These results provide design criteria for future SHOP-DI systems and demonstrate a high-bandwidth, high-sensitivity design useful for pulsed-power electrode plasma measurements.

This document summarizes the activities at the Mykonos Pulsed Power Facility during the calendar year 2025. Section 1 reports on the yearly shot statistics along with some facility highlights. Section 2 discusses the many improvements we were able to complete this year, thanks to the generous Mykonos Academic Access Programs (MAAP) funding from SSAP and Sandia strategic investments. Section 3 focuses on each individual campaign and their respective results.

We present an overview of visible self-emission and laser imaging diagnostics for the Z Machine at Sandia National Laboratories. First, we review the Self-Emission Gated Optical Imager (SEGOI) diagnostic. SEGOI utilizes the Z Line Velocity Interferometer System for Any Reflector (Z Line VISAR) imaging relay system and detectors with a modified in-chamber optical configuration that is more flexible and significantly lower in cost. Detectors include eight intensified CCD (ICCD) cameras (540–600 nm) and two streak cameras (532 nm). The choice of in-chamber lens is flexible and determines the field-of-view (6.8–14 mm) and spatial resolution (∼32–74 μm edge widths). Next, we review the Laser Imaging on Z (LIONZ) diagnostic. LIONZ injects an open-beam 532 nm laser into the Z chamber via the Z Line VISAR beam transport system. This beam is redirected to the back of the target and then collected utilizing SEGOI. An additional 4-frame ICCD camera collects laser shadowgraphs, and one or both of the SEGOI streak cameras may be configured for streaked shadowgraphy, while the eight ICCD cameras for SEGOI may be simultaneously fielded for self-emission imaging. Currently, two open beam lasers with adjustable trigger times and a full-width-half-maximum of 20 ns are injected. Together, SEGOI and LIONZ offer valuable insight into the dynamics of low density plasmas on Z.

Magnetized liner inertial fusion (MagLIF) experiments have demonstrated fusion-relevant ion temperatures up to 3.1 keV and thermonuclear production of up to 1.1 × 1013 deuterium–deuterium neutrons. This performance was enabled through platform development that provided increases in applied magnetic field, coupled preheat energy, and drive current. Advanced coil designs with internal reinforcement enabled an increase from 10 to 20 T. An improved laser pulse shape, beam smoothing, and thinner laser entrance foils increased preheat energy coupling from less than 1 to 2.3 kJ. A redesign of the final transmission line and load region increased peak load current from 16 to 20 MA. The wider range of input parameters was leveraged to study target performance trends with preheat energy, applied magnetic field, and peak load current. Ion temperature and neutron yield generally followed trends in two-dimensional clean Lasnex calculations. Stagnation performance improved with peak load current when other input parameters were also increased such that convergence was maintained. This dataset suggests that reducing convergence to less than 30 would improve predictability of target performance. Lasnex was used to identify a simulation-optimized scaling path, which suggests 10+ kJ of fusion yield is possible on the Z facility with achievable input parameters. This path also indicates >10 MJ could be generated through volume burn on a future facility with a path to high yield (>200 MJ) using cryogenic dense fuel layers. The newly developed MagLIF platform enables exploration of both this simulation optimized scaling path and a recently developed similarity-scaling path.