Session TM11: Mini-Conference: Pulsed Magnetic Fusion Energy I

Pacific Fusion’s High Gain Fusion Pulser

We describe Pacific Fusion’s Demonstration System (DS), a high-gain [1] and high-yield fusion capability. DS drives deuterium-tritium filled cylindrical targets to ignition and high target gain (GT~10), with the goal of demonstrating facility gain GF >= 1. The pulser is equipped with an extensive diagnostic suite, building upon decades of research in inertial confinement fusion. We discuss considerations for Hertz-class repetitive pulsed applications, and the unique pulse shaping capabilities that distinguish Pacific Fusion’s Demonstration System as a versatile high-gain fusion system. We will present the overall system architecture, the pulser design that delivers the required 60+ megampere, 100 nanosecond pulses to a high gain target, and the operations and safety considerations for the facility.

[1] “Opportunities in Pulsed Magnetic Fusion Energy,” C.L. Ellison et al (2024), in preparation   

Scaling pulsed magnetic fusion designs to high yield for Pacific Fusion's demonstration facility

We describe the scaling of designs for pulsed magnetic fusion experiments to Pacific Fusion’s ignition-scale Demonstration System. Pacific Fusion is building a Demonstration System to drive fusion-fueled cylindrical loads to ignition and high target gain (G_T ≈ 10), with the goal of demonstrating facility gain G_F  ≥  1. Initial design work is focused on the MagLIF concept. We show 1D and 2D simulations of MagLIF in the radiation-magnetohydrodynamics code FLASH. Comparisons between FLASH simulations of 15-20 MA MagLIF experiments on the Z facility and published results are used to validate FLASH for fusion target design. We apply similarity scaling^1,2 to predict MagLIF performance at ignition-relevant peak current. Future design directions for MagLIF are discussed in the context of recent experimental results on Z.

1. P.F. Schmit and D.E. Ruiz, Phys. Plasmas 27 062707 (2020).

2. D.E. Ruiz, P.F. Schmit, et al., Phys. Plasmas 30 032708 (2023).   

Validation of FLASH for modeling magnetically driven implosions

Multiphysics radiation hydrodynamics simulations are essential tools for designing high performance inertial confinement fusion targets. Pacific Fusion is actively developing FLASH for use as a target design code for ignition and high-gain pulsed magnetic fusion energy. To establish confidence in FLASH’s capabilities as a target design code we have been systematically validating FLASH against a suite of published data from pulsed magnetic fusion experiments at Sandia’s Z Facility. This suite includes focused physics experiments — including radiographic measurements of magneto-Rayleigh-Taylor growth and stagnation-time fusion fuel confinement — as well as fully integrated fusion platforms such as MagLIF. We demonstrate 1D and 2D FLASH simulations agree well with both experimental data and existing production design codes for pulsed magnetic fusion targets.   

Advances in FLASH for magnetized HED processes

The FLASH code has recently undergone significant development to become a robust tool to model Z-Pinch implosions [1]. These simulations present many challenges due to their multiphysics nature and the presence of external magnetic fields. Pacific Fusion is further enhancing FLASH’s capabilities to ensure accurate models of targets for pulsed magnetic fusion energy. In this talk, we discuss various improvements to FLASH’s magnetized HED capabilities including improved opacity mixture strategies for multispecies plasmas; the implementation of per-species transport models and its effect on integrated simulations; and code enhancements for multi-regime thermal conduction models. We also present two comprehensive test cases to benchmark FLASH features against analytical solutions in relevant magnetized HED scenarios. First, we demonstrate the code's ability to capture the structure of radiative shocks in different regimes encompassing disparate optical depths [2]. In the second test case we assess the effect of thermoelectric terms in Nernst thermal waves in hot-spot MagLIF-like plasmas [3]. 

[1] E.C. Hansen et al., Phys. Plasmas 31, 042712 (2024).

[2] F. Garcia-Rubio et al., Phys. Rev. E 109. 065206 (2024).

[3] A.L. Velikovich et al., Phys. Plasmas 22, 042702 (2015).   

The planned diagnostic suite for Pacific Fusion's demonstration facility

Advances in diagnostic instrumentation have fueled the experimental progress of inertial confinement fusion (ICF) and high-energy-density (HED) plasma physics efforts in recent decades. This talk describes the status of the design of the diagnostic suite for Pacific Fusion's demonstration facility, a Z-pinch driver based on the impedance-matched Marx Generator (IMG) pulsed power architecture. Figures of merit for the diagnostic suite are discussed, in terms of measurement accuracy and precision, known failure mode sensitivity, and unknown unknown discovery. Tradeoffs in specific diagnostic instrument selection are considered from a range of perspectives, including opportunities to incorporate diagnostic shielding into facility design and to draw on progress at leading HED facilities including the NIF, OMEGA, and the Z machine. Opportunities for novel diagnostic designs to increase performance beyond the current state of the art are weighed, as well as the role that machine learning may play in the design stage of a new facility.   

A multicollaborative approach to IFE facilitated by a computational approach to advanced target design

First Light Fusion have identified several fusion driver concepts, that have the potential to realise cost competitive IFE, enabled by our proprietary Amplifier technology. Our current technical strategy is to identify and solve the principal science and engineering challenges of these drivers and the powerplant fusion island, through a consortium of business partners. This approach spreads risk and allows First Light and their partners to fully contribute their unique attributes to realise fusion as a viable contribution to the addressable energy market.

First Lights Amplifier technology can reduce the power requirements on the drivers and simplify the challenges faced by the powerplant. We are currently working towards, conceptual sytems design of the drivers, and high gain driver agnostic target design aspects, coupled with our unique amplifier designs. Two of the drivers we are evaluating are pulsed power driven; a nested liner approach similar to the one of Colgate et al.[1] and an Electric Gun [2,3,4]

Amplifiers act as a shock focussing and shaping device, to drive a spherical fuel target. They are designed with our in-house computational science and engineering capabilities, a unique tool set and approach for industrial IFE. Our amplifiers have been used successfully to realise fusion on a high energy, low power driver, and to extend the operational range of existing pulsed power platforms for EoS studies.

[1] Colgate et al., LANL Technical Report. LA-UR-08-06915, Presentation to Sandia National Laboratory, October 30, (2008)

[2] R. Weingart et al., LLNL Techical. Report. UCRL-52752 TRN: 79-015919, (1979)

[3] M. Fitzgerald et al. IEEE Transactions on Plasma Science, Volume: 51, Issue: 8, p2347–2357 DOI: 10.1109/TPS.2023.3300093 (2023)

[4] M. Fitzgerald et al. International Journal of Impact Engineering, Volume 184, 104814 (2024)   

A shock amplification platform for multi-TPa equation-of-state experiments on the Z machine

First Light Fusion (FLF) is developing hydrodynamic pressure amplifiers as part of its IFE program. Through the Z fundamental Science Program, FLF have been collaborating with Sandia National Laboratories to develop these amplifiers as an equation-of-state platform.

On the Z machine, magnetically-driven flyer plates are routinely used as drivers for shock Hugoniot and release measurements at pressures of up to several TPa, depending on the sample material. In this work, we demonstrate effective coupling of a hydrodynamic pressure amplifier to a flyer plate driven by the Z machine, to increase the attainable pressure whilst maintaining a diagnostically significant sample size and hold time.

 

A 31 km/s aluminium flyer plate impacted a linear array of 4 hydrodynamic amplifiers. Amplifier spatial and temporal output was characterized via spatially resolved velocimetry of the shock front driven into a quartz sample located at each amplifier output. The experiment demonstrated a quar­­­­­tz shock pressure of 1.85 TPa over a diameter of 500 um and temporal hold of ~10 ns.  The temporal and spatial uniformity are suitable for high-precision equation of state measurements relative to a standard. This represents a 25 % increase over previously attainable quartz pressure on Z.

 

Future experiments will target quartz principle Hugoniot pressures of 3 – 5 TPa, allowing cross facility validation of high-pressure quartz Hugoniot data obtained on the NIF [M. C. Marshall et al., Phys. Rev. B 2019].   

Results from TITAN, the world's first high energy, high-power IMG driver. We then discuss using multiple TITAN modules for the 15TW Z-STAR midscale pulsed power facility and Apeiron-I concept as the next generation pulsed power facility for stockpile stewardship and fusion engineering breakeven.

TITAN is the world's first high energy and high power (1TW) impedance matched Marx generator (IMG) driver. This talk will present experiments at 6 stages of TITAN tested up to +/- 70 kV charge voltage which delivers the peak power of 330 GW to its 1.2 Ω resistive load. TITAN's brick consists of a pair of double ended 80 nF, 100 kV capacitors connected electrically in series which are insulated from each other by a normally open pressurized 200 kV field distortion gas switch (FDGS). Our next venture, Z-Star, is a 15 TW Z-Pinch driven ICF facility, leveraging TITAN's technology for high-impact HEDP science. Z STAR is a 12-MA pulsed-power machine with kJ-class laser, serving as a prototype for future facilities. Following Z-Star, we aim to construct Apeiron-I, a 300-500 TW NGPP, poised to be the most powerful pulsed power fusion facility globally. With over 50 MJ energy storage, Apeiron-I will deliver ~50 MA to its load, targeting a scientific Q: >3.   

Forging the Future: A Collaborative Path to a Pulsed Power Next-Generation High-Energy-Density Science Facility through a Public/Private Partnership Program

In an ever-changing geo-political climate, maintaining and strengthening nuclear deterrence remains a critical priority for our nation. However, achieving this objective without conducting underground testing presents a significant challenge. To address this, the U.S. requires capabilities beyond what it currently possesses, particularly in the field of high-energy-density science. A much-needed capability gap in the area of high-energy-density science is a facility that can enable high-yield fusion (>200 MJ). While laser-based technologies have made significant strides and demonstrated a historical ignition record yield of 5.2 MJ, significantly more drive energy is estimated to be needed to achieve high-yield fusion. A potential cost-effective alternative toward this goal is the construction of a pulsed-power machine larger than the existing Sandia Z-machine. The National Nuclear Security Administration (NNSA) and the national laboratories have been actively exploring options for the execution of such a machine. However, the current budget climate poses a significant hurdle in terms of affordability. To overcome this challenge, one potential approach is to pursue a cost-shared public/private partnership, leveraging resources and expertise to reduce costs and expedite facility construction. In this presentation, we will discuss options and provide an update on the progress made in developing a path towards a next-generation high-energy density science facility through a public/private partnership program.