One of the biggest problems in creating a nuclear fusion reactor that mimics the sun is the ability to control the plasma fuel. Since the 1940s, scientists have been looking for ways to initiate and control fusion reactions to produce useful energy.
It has been a difficult journey because fusion reactions require temperatures of hundreds of millions of degrees, too hot to be contained by any solid chamber, making it hard to control the instability of the plasma.
Physicists, instead, sought to contain the hot plasma with magnetic fields, using, for example, the pinch effect where electric currents moving in the same direction attract each other through their magnetic fields. This approach is called “magnetic confinement.” Pinches occur naturally and are seen in lightning bolts, the Aurora, or solar flares.
Embrace the instability
However, a New Jersey fusion startup company is taking a very different tack: “Guide the plasma’s instability; don’t fight it,” says Eric Lerner, president and chief scientist at LPP Fusion, based in Middlesex, N.J.
LPP Fusion is building a Dense Plasma Focus (DPF) device. The DPF consists of a thick, hollow central anode surrounded by a ring of cathodes that are about the size and shape of candles. Using electromagnetic acceleration and compression, the device produces a short-lived plasma that is hot and dense enough to cause nuclear fusion and the emission of X-rays and neutrons.
This is how LPP Fusion’s DPF works: The device’s two cylindrical metal electrodes are nested inside each other. The outer electrode is generally no more than 6-7 inches in diameter and a foot long. The electrodes are enclosed in a vacuum chamber with a low-pressure gas filling the space between them.
Using a battery storage device, called a capacitor bank, a pulse of electricity is discharged across the DPF’s electrodes. Keep in mind, this happens for a few millionths of a second as the intense current flows from the outer to the inner electrode through the gas. The current starts heating the gas, creating an intense magnetic field.
Then guided by its own magnetic field, the current forms itself into a thin sheath of tiny filaments; little whirlwinds of hot, electrically-conducting gas called plasma. The sheath of plasma then travels to the end of the inner electrode where the magnetic fields produced by the currents pinch and twist the plasma into a tiny, dense ball only a few thousandths of an inch across called a plasmoid.
Further instabilities in the plasmoids produce electron beams, which heat up the plasmoids to the temperatures required for fusion. The work and a description of the resulting reaction are in a paper submitted to the journal Physics of Plasmas, still under peer review at this time.
The proton-boron fusion method
Lerner and his coauthors claim to have produced a confined mean ion energy of 200 kiloelectron volts, equivalent to a temperature of over 2 billion kelvins. “As far as we know, that’s a record for any fusion plasma,” Lerner says. Lerner is now sharing the results of LPP Fusion’s work with investors and the public.
“In the critical measure of how much energy out, we get per unit energy in, we’re No. 2 among all the experiments in the world,” Lerner says. “And we’re only one-third behind the JET [Joint European Torus] experiment in the United Kingdom—which has almost a thousand times our resources. In terms of results per unit dollar, we’re clearly No. 1, by a long way.”
LPP Fusion hopes to be the first facility to achieve break-even nuclear fusion by fusing simple hydrogen nuclei, with one proton, and no neutrons, with boron, which has five protons and six neutrons. This is a big difference in what other facilities are doing, including JET, the National Ignition Facility, and ITER, which fuse different isotopes of hydrogen together.
With proton-boron fusion, no neutrons are produced, meaning there is no radioactivity from the primary reaction. One down-side in this type of reaction – it requires a higher temperature and density than deuterium and tritium fusion technology.
LPP Fusion has one competitor in the proton-boron fusion race, and that is Tri-Alpha Energy, backed by Microsoft co-founder Paul Allen. In July, Digital Journal featured a story highlighting TAE’s collaboration with Google that led to the creation of the “Optometrist Algorithm.”
Heinrich Hora, emeritus professor of physics at the University of New South Wales, in Australia, said Tri-Alpha may have higher-profile collaborators, but even with that, LPP may have a better approach, according to IEEE Spectrum.
“The work of Eric Lerner may be more promising than what they do at Tri-Alpha, because [LPP] has higher densities,” Hora says. “This is an argument in favor of Eric Lerner.”
