Plasma and pulses
While the fission reactions that power traditional nuclear power plants split atoms apart, fusion works by forcing them together, under extremely high temperatures, to overcome the usual repulsive forces of atoms in close proximity. That produces a new atom minus a little bit of mass, the loss of which generates a whole lot of energy.
Most other labs and startups rely on powerful lasers or doughnut-shaped machines surrounded by powerful magnets, known as tokamaks, to create the conditions in which a sustained series of fusion reactions can occur—a condition known as ignition. But Helion is developing what it calls a “pulsed non-ignition fusion system,” which only requires fusion to take place for short periods.
The company’s device is a six–by-40-foot barbell-shaped “plasma accelerator.” It uses powerful magnets to heat a gas mixture to the point that the atoms break apart, creating rings of an ultra-hot state of matter known as plasma on either end of the device.
The magnets then propel those rings at each other at a million miles per hour, and further compress them in the middle of the device, which creates those temperatures of more than 100 million ?C, the company says. That triggers fusion reactions, in which nuclei collide, protons and neutrons combine, various particles are released, and energy is produced.
Other fusion approaches would require an additional step to convert that energy into electricity, through conventional methods like warming water or other working fluids into a gas that turns a turbine. But Kirtley says Helion’s process can recover electricity directly.
As the plasma continues to heat and expand, its own magnetic fields push against those created by the magnets surrounding the device. That drives a flow of charged particles, otherwise known as an electric current, through the adjacent electromagnetic coils. And that, in turn, recharges an energy storage device known as a capacitor, which powers up the magnets, readying them to deliver the next pulse.
To work as a power plant, Helion’s device will need to produce energy on top of what’s required for the pulses. That additional energy would be then converted into alternating current and routed onto the grid.
The planned commercial generator wouldn’t need to be physically larger than Helion’s latest prototype, but it will require additional systems for cooling, electricity connections, and other purposes, Kirtley says.