Plasma Jet Magneto Inertial Fusion ARPA-E and Los Alamos National Lab Plans for 2027 relevant gain

PJMIF involves converging plasma jets that are launched from symmetrically distributed plasma rail-guns (or plasma guns), so as jets come in, they merge and form a plasma liner that compresses the plasmoid target (spheromak or FRC), which reaches fusion conditions at peak compression.

There appears to be a sweet spot where the burning plasma density is in the range 10^19 to 10^22 ions per cc. In this sweet spot, the stunning result of their analysis is that fusion approach exists for which breakeven fusion facility might very well cost as low as $51 million.

In 2004, an experimental research program and HyperV Technologies Corp. were initiated to build and optimize electromagnetic plasma accelerators based on the new insights developed over the prior several years. Since then, HyperV has demonstrated steady advances and set records for the combination of jet mass, density, and velocity. Their initial work focused on the larger coaxial guns with shaped electrodes suggested by Thio‘s research. In the past few years, HyperV‘s focus has shifted (temporarily) to simpler, more compact parallel plate ―mini-railguns‖ which were originally intended only to ionize and inject the plasma pre-fill into the coaxial guns. However, it was realized that the mini-railguns, much simpler and cheaper than the coaxial guns, could achieve the combination of mass (few mg), density (10^17 cm−3), and velocity (50 km/s) required for the first spherical plasma liner formation and implosion experiments to be carried out on the Plasma Liner Experiment (PLX) at Los Alamos National Laboratory (LANL). And thus, for reasons of cost and expediency, the mini-railguns are receiving most of the present research attention, although the coaxial guns will likely be needed for fusion-relevant plasma liner implosions, due to their ability to accelerate large masses to high velocities (over 100 km/s) and their better potential for forming composite jets with D-T fuel in front and a heavy high atomic number pusher species in the rear.

HyperV had a kickstarter in 2012 and delivered it in 2013. They have used minirailguns for a plasma propulsion system which can achieve 2000 to 8000 ISP.

PJMIF is an attractive approach to practical, economic fusion energy for the following reasons:

(a) Plasma guns, made of metallic alloys, are robust.
(b) The plasma guns are energy efficient and theoretically can have efficiency exceeding 50%. They are driven directly by pulsed power, which has lower cost than lasers per unit energy.
(c) Plasma guns and pulsed power supplies, being ‘low-tech’, are inexpensive making the capital cost of the fusion reactor very inexpensive.
(d) The physics of the implosion scheme is robust with respect to practical engineering variability in the fabrication of the targets, etc. The size of the implosion is relatively large. The initial target and liners are about 10 cm in diameter.
(e) The targets and liners are ordinary gases and require no special fabrication. The recycling cost is low. There is no solid debris to be removed from the chamber after each shot.
(f) PJMIF is ‗reactor friendly‘. It is compatible with the use of liquid or disposable first-wall to protect the critical components of the system from neutron damage.

Note also that, unlike some MIF approaches, no material debris is generated by the implosion in the PJMIF approach, because it uses plasma jets as drivers launched from standoff distances. And unlike laser ICF, the evacuation of the reactor chamber does not present as challenging an engineering problem as laser ICF, because firstly it is sufficiently economical to operate the reactor at a much lower repetition rate of 1 to 5 Hz, and secondly PJMIF does not requires as high a vacuum as laser ICF in the chamber, as the propagation of dense plasma jets is much more tolerant of residual gases in the chamber as laser light.

The above description of PJMIF is based on PJMIF embodiments and configurations that have been released to the public domain. Proprietary embodiments of PJMIF known to the authors of this paper exist that considerably improve on the overall reactor performance and address the key issues.

ARPA-E and Los Alamos National Lab presentation on Plasma Liners and the Potential for a Standoff Magneto-Inertial Fusion Reactor.

Less then $500 million research and development path to single shot relevant gain.

Here is a 2011 presentation by USCL corp

The main advantage of PJMIF over classical ICF and MCF is that it does well in combining the best of both concepts, namely inertial compression and strong magnetic fields. Magnetic field is embedded in the target plasmoid, so when the target compresses, the magnetic flux increases inversely proportional to the radius of the target, taking magnetic field strength to MG levels.

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