Seattle Company Seeks Fusion Power
In an obscure laboratory in Seattle, something potentially revolutionary is taking shape. A small team of elite scientists, with the backing of major government agencies for funding and oversight, is trying to radically reinvent power production and spaceflight through mastering one of the most coveted and challenging sources of power known to science.
If you think that sounds like something straight out of science fiction, you’d be right. Nuclear fusion-a process where highly excited atoms in a plasma are made to merge together and release astonishing amounts of energy-has been a mainstay of science fiction for decades, as a source of power or a method of driving spaceships across the universe. But despite its futuristic gloss, the process has been studied for over 80 years, both out of pure scientific curiosity and out of a desire to use this virtually inexhaustible, carbon-free source of energy to provide cheap electricity and superior space propulsion technologies to the human race.
The beginning of fusion research was intensely hopeful. Efforts at fusion for power generation began in the late 1930s, but picked up steam by the the early 1950s as governments started to take a keener interest in fusion. The classified Project Sherwood saw a profusion of different types of reactors extensively investigated, including Z-pinch reactors. These devices, created in labs on both sides of the Iron Curtain during the 1950s, sought to create fusion by passing a powerful current through the plasma to make its constituent particles compress together due to their mutual attraction from the Lorentz force, crushing together the atoms with enough energy to hopefully release fusion energy-however, researchers quickly ran into a snag. The process was wildly unstable, with the resultant energized and compressed plasma proving impossible to control. The so-called kink instability, caused when irregularities of the plasma were magnified by its self-attracting properties and caused it to oscillate and fall out of confinement, put a fast end to early hopes that fusion energy would be quickly achieved, but that was only the beginning of the problems the Z-pinch would face.
By surrounding the experimental reactors with magnets to push the unruly plasma back into line, the large-scale kink instability could be suppressed, and as competition with the Soviets loomed, scientists in the UK completed the large and ambitious ZETA reactor and found initially highly encouraging results that led them to believe they were creating significant numbers of fusion neutrons. The results made headlines in newspapers across the world and were heralded as revolutionary for energy production and a matter of national pride. But soon doubts about the nature of the detected neutrons grew among scientists due to the inconsistency of the plasma’s temperature with its alleged release of neutrons, and it was soon discovered that they were not from fusion reactions,but from unrelated electrical effects of the system’s magnetic field. In truth, other more subtle instabilities of the pinch made neutron production from fusion an impossibility for ZETA.
Although it was a useful and long used experimental plasma system, the failure of ZETA to make fusion neutrons largely ended the z-pinch being considered a valid system for high-power nuclear fusion. The USSR soon created a far more effective fusion reactor design, the tokamak. Tokamaks primarily rely on magnetically confining and compressing the plasma with a powerful external magnetic field, and these devices have succeeded in creating fusion neutrons and attaining far higher temperatures than the Z-pinch could. These have been the mainstay machines for fusion research for decades, and continue to be the best-funded and most exposed concept for fusion power production. However, for all the progress made, tokamaks are still multiple decades from putting energy into the grid. ITER, the massive international scientific project to eventually create a fusion reactor that makes more energy than it takes to heat the plasma, won’t begin its deuterium-tritium experiments that are relevant to attaining net energy until the mid 2030s at the earliest. (Several private companies seek to beat ITER to the punch of creating net energy, but even the most far-along of these designs is far off being break-even, much less commercially viable)
But the tokamak isn’t the only game in town. Over roughly the last 20 years, an increasing number of investors and scientists have sought new ways to create affordable fusion power faster than ITER, often reviving generally discarded concepts for fusion power production under the assumption that new advances in technology might give these concepts new life. Lockheed Martin’s Skunk Works is experimenting with a high-beta concept, the field-reversed configuration in being looked into by companies like Helion Energy and TAE Technologies, and at Zap Energy, the Z-Pinch is finding new life in a revised, improved form.
What’s Old is New Again
Zap Energy’s Uri Shumlak is no novice when it comes to plasma physics research. After earning a PhD from the University of California, Berkeley in Nuclear Engineering he worked for the Air Force’s Phillips Laboratory doing advanced plasma research, and has been a professor at the University of Washington’s Aeronautics & Astronautics program for over a quarter century. Shumlak has spent his time as a professor working at a variety of projects relating to advanced plasma physics, primarily investigating the concept of using sheared flow stabilization to tame the inherent instability of the Z-pinch since the early 90's.
A sheared flow refers to the plasma being physically moved at different speed depending on how far it is from the center of the linear reactor rather than being all at the same velocity. Research by Shumlak and several of his colleagues like Yue Zhang and B. A. Nelson shows that this sheared flow dramatically improves the lifespan of the resultant plasma and has suppressed the normally uncontrollable kink instabilities and other chaotic magnetohydrodynamic effects that tend to make standard Z-pinches far too unstable to be considered for net-power applications, leading them to the successful production of fusion neutrons and vastly longer confinement times for their plasma.
The most recent version of the sheared flow design, the FuZe reactor, is capable of sending three hundred thousand amps of electrical current through a plasma and maintaining that highly energized neutron emitting plasma for around 5 microseconds-a very short amount of time in human terms, but an eternity in the world of plasma physics. This success has been in part possible due to outside government funding, from ARPA-E’s ALPHA funding program and more recently a 6.8 million dollar award from the OPEN program, also run by ARPA-E. These government-sanctioned awards include strict goals for plasma performance to be met, which the team have so far successfully achieved.
Zap Energy’s ambitious goal is to create a reactor that makes as much energy from fusion as it takes to heat the plasma when fueled with deuterium and tritium by the early 2020s after building a new experimental reactor that can sustain 600 thousand amps of current. A hypothetical power plant based on this design would be run at over 1.5 million amps and use liquid metal walls surrounding the pinch system to transfer heat for power production and breed tritium using the emitted neutrons. Since the system is comparatively small next to the mammoth size of orthodox tokamaks, owing primarily to its lack of bulky and delicate superconducting magnets, the team has bold ideas about using these devices as incredibly powerful and efficient thrusters for future spacecraft, as well as small and inexpensive terrestrial power sources.
Bold predictions of net power being just around the corner are nothing new in the world of fusion, and cynicism in the face of endless failure and delay is easy to justify. At the very least,if this concept for fusion turns out to be a dud, its relative simplicity and speed to be constructed means we won’t be kept waiting on the results for agonizing decades. Speaking personally, I wish all the teams working at fusion the best of luck, and hope one day to lift a glass in celebration at the lighting of the Eternal Fire.
