Interview with Pacific Fusion on Goals for their Inertial Confinement Demonstrator System

Last Friday, The Fusion Report interviewed Will Regan, President of Pacific Fusion, regarding their announcement today on the progress that Pacific Fusion is making on their Demonstration System (DS) and their expectations for its performance. Let’s start out with the headlines of the press release:

• Pacific Fusion expects that their DS will achieve 1,000 times the price-performance versus what has been achieved by the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory (LLNL) by 2030.
• The company is projecting that DS will achieve a 100-fold higher facility-level energy gain than NIF, which achieved a Q (the ratio of energy produced by the fusion event versus the energy imparted to the fusion target) of 1.5 in December 2022 (NIF eventually reaching a Q of 2.44).
• The company is also projecting that the DS will cost one-tenth the cost of NIF (hence the 1000X price-performance increase).
• These projections are supported by Pacific Fusion’s completion of their Phase 1 milestones in November 2024 (significantly ahead of their schedule of June 2025).

This progress and the plan for the DS are detailed in Pacific Fusion’s white paper titled “Affordable, manageable, practical and scalable (AMPS) high-yield and high-gain inertial fusion,” which describes their pulser-based approach to inertial confinement fusion (ICF).

What is Pulser-Based ICF?

When most people think of ICF, they think of laser-based ICF like that used at NIF (we published a short history on laser ICF last week in The Fusion Report). In laser ICF, a small pellet of fusion fuel (usually deuterium-tritium, also known as “D-T”) is simultaneously hit by a large number of high-energy, short-duration laser beams (192 in the case of NIF) that cause thermal x-rays to be emitted. These thermal x-rays simultaneously heat and compress the fusion fuel, causing ignition. The image below shows how this works within a tiny enclosure known as a hohlraum; the blue beams are the lasers, while the red spots are the points where the x-rays are emitted (the fuel is the sphere in the center). For reference, the sphere is roughly 2 millimeters in diameter.

The greatest problem with laser-based ICF is that the generation of high-power laser beams (at least in the case of NIF’s lasers) is very energy-inefficient. However, lasers are not the only means of achieving ICF. Theoretically, any projectiles moving fast enough that hit the target simultaneously could do the trick, including x-rays, accelerated particles, or solid projectiles. Pulser-based ICF takes a slightly different approach to inertial confinement, however – instead of hitting the fuel with projectiles, pulser-based ICF hits the cylindrical metal fuel container with intense pulses of electrical current. This current causes extremely strong magnetic fields in and around the container, compressing it (and the fusion fuel) until it ignites.

The Architecture of the Pacific Fusion DS

Pacific Fusion’s DS generates its current pulses through the use of impedance-matched Marx generators (IMGs). In the case of the DS, there are 156 sets of pulser modules , arranged in a spherical shape around the target area as shown below (note that the diagram shows half of the DS). The dimension of the DS is projected to be 73 meters x 80 meters, slightly larger than a standard soccer field. The target area is confined in a large water tank, which is filled with de-ionized water which acts as a dielectric, and to absorb neutrons and x-rays generated by the fusion reaction.

The overall system is highly modular in its design, with each of the pulser modules being a stand-alone assembly. The IMG pulser modules, which are roughly 1.9 meters in diameter, each contains 320 bricks organized into 32 rings (also known as “stages”) of ten bricks each. 

Each brick contains two capacitors and a low-impedance spark gap switch. Each brick is charged to +/-100kV, with a capacitance of 160nF. When the switches are opened, the energy from the capacitors in the stage (800 joules per capacitor) is discharged into the anodes. Each of the oil-filled modules can store up to 0.5 MJ of energy; with 156 modules, this adds up to roughly 80 MJ of total energy stored, about 10% of which is delivered to the target area.

Target and Fusion Chamber Modularity to Speed Maintainability

One of the areas that can be a challenge for magnetic confinement fusion (MCF) is the adjacency of the super-heated fusing plasma to the inner first walls, thermal blanket, and confinement magnets in the fusion machine. The problems that this presents include high temperatures, high neutron flux, and x-ray impingement. While MCF companies continue to make significant progress on this, it is a problem that drops off with distance. One of the advantages of ICF approaches is that there is not a requirement for components to be in close proximity to the fusion reaction itself (the “insulator stack” cylinder below is 6 meters in diameter).  This “extra space” also simplifies maintenance operations by allowing new components to simply be “craned” into place during normal maintenance shutdowns, such as being able to replace the “target cassette” after every shot to improve its efficiency.

Expected Power Efficiency of The Pacific Fusion DS Machine

The greatest challenge with inertial confinement fusion is the transfer of adequate energy to the fuel target, as shown on the left of the diagram below. Laser-based ICF (as demonstrated by NIF) simply loses too much energy to achieve “facility break-even”, let alone a 2X or 3X energy production. The DS Pulser, as shown on the right side of the diagram, loses far less energy than NIF does in coupling stored energy to the fuel. This means far more energy is reaching the target, potentially improving energy to target by 50X.

The goal of the Pacific Fusion DS machine when it is completed will be to show “net facility gain”; i.e., more energy is output by the fusion reaction than is required to charge the DS machine. If achieved, this would represent a real demonstration that inertial confinement fusion can be a real means for delivering fusion energy commercially. More importantly, it would demonstrate that fusion energy (and particularly, inertial confinement fusion energy) is a viable approach to commercial fusion power. While NIF is the only fusion machine that has reached Q>1 to date, NIF is definitively not the template for a commercial fusion plant in the same way that the Commonwealth Fusion System ARC machine, currently scheduled to begin operation in 2026 is. Success with the Pacific Fusion DS machine would put “commercial-template” ICF machines only a few years behind tokamaks. Given the difficulties of fusion, having a few extra options in hand is not a bad thing!