Fusion startups have been struggling to raise funding lately, and young startup Acceleron Fusion is joining the pack, raising $15 million of its $23.7 million target investment, according to an SEC filing.
The nuclear fusion sector has recently attracted a lot of attention from investors. They may have been inspired by a groundbreaking experiment conducted two years ago at the National Ignition Facility. This demonstrates that a controlled fusion reaction can generate more power than is needed to start the fusion reaction.
The first company to build a power plant capable of generating electricity in large quantities that can be sold to the grid could begin to inch its way into the trillion-dollar global energy market. In particular, technology companies have been eyeing fusion and nuclear power startups as zero-emission solutions to AI-driven power demand.
Acceleron did not immediately respond to questions.
While most startups aim to recreate the superheated, ultra-high pressure conditions inside stars, Acceleron takes a different approach, using subatomic particles known as muons to lower the heat and pressure needed for nuclear fusion reactions to occur.
In nature, atoms tend to resist fusion because the electrons orbiting them repel other atoms. To solve this problem, most approaches to nuclear fusion follow nature’s approach. That is, by making the atoms hot and close enough that electrons can escape their orbits, lowering normal atomic inhibition. As atomic nuclei hover without electrons, some collide with each other, fusing into new nuclei and releasing enormous amounts of energy. This is what happens inside stars.
Muon-catalyzed fusion takes a different approach. Instead of heating and compressing hydrogen isotopes, muons are injected into the mixture. Muons are atomic particles similar to electrons, both have a negative charge, but are 207 times more massive. Muons bombard hydrogen isotopes, displacing electrons from some of the atoms. Muons orbit the nucleus much closer than electrons, lowering the barrier for atoms to fuse.
In muon-catalyzed nuclear fusion, the barrier is low, allowing fusion to occur at room temperature and pressure. This is why it is sometimes called cold fusion. Muon catalysts have been demonstrated under laboratory conditions, but the energy required to create muons has so far surpassed the amount of energy produced by nuclear fusion reactions.
There are several reasons why muon-catalyzed nuclear fusion hasn’t worked yet. For one thing, each muon only lasts about 2.2 microseconds before decaying into less useful subatomic particles. That’s long enough to catalyze about 100 fusion reactions, but still too short for commercial power purposes. Another problem is that in about 0.8% of cases, the muon becomes attached to another subatomic particle (alpha particle) and no longer participates in the fusion reaction. That may not seem like much, but it was high enough to ruin commercial plans.
Acceleron, a Cambridge, Mass.-based spinoff of NK Laboratories, hopes that by increasing the pressure and temperature of a mixture of hydrogen isotopes, it can reduce the rate at which muons attach to alpha particles. The hope is to keep enough muons in the mix to fuel more fusion reactions. Ideally, more than enough to offset the amount of power needed to produce a muon.
NK Laboratories received a three-year, $2 million ARPA-E grant in 2020 to investigate whether higher pressures could improve the prospects of muon-catalyzed fusion. The results, which are currently not fully disclosed, appear to have stimulated investor interest.
