Cambridge Heavy Industries Quietly Building Tabletop Fusion Device

Fusion power startup Cambridge Heavy Industries is building a small laser-driven fusion device to supply the future wave of fusion power plants.

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Fusion power usually conjures up images of massive industrial facilities with lasers or big magnets, but a startup in Cambridge, Mass., is quietly building a device that can sit on a desk.

The optics of the device were shown behind Yun Kai, co-founder and CEO of Cambridge Heavy Industries, as he chatted with me on a video call. The company operates in secret in a small lab near MIT, and Kai gave TechCrunch an exclusive look at the technology it's developing.

"We purposely built a small modular reactor. It's small, it's on the table," he told me. "Because it's small, it makes everything easier."

The compact size allows Cambridge Heavy to test and iterate quickly. "The nature of the small module can enable 50 to 80 tests, 50 to 80 shots per day," he said. Data from these tests feed simulations that use artificial intelligence to optimize the design.

This clever approach has attracted the attention of investors. The startup recently raised a seed round of $6.2 million led by Azolla Ventures with participation from Overlay, Neta Foundation, P3A, MassCEC and the Rothrock family.

The Cambridge Heavy Fusion Reactor uses lasers to compress a fuel target, similar to the groundbreaking experiment that proved controlled fusion. Reactions can produce more energy than they consume. But unlike other inertial confinement designs, Cambridge Heavy minimizes the number of lasers needed to spark fusion.

This system uses two main lasers to guide the spark. A laser is split into multiple beam lines that deliver light in concentric rings. Rings of laser light start from the outside and work inward to successively hit the flat and round fuel target. The first ring initiates a compression wave at the target that begins to travel inward. Subsequent laser rings are timed to amplify the wave at just the right moment to further compress the fuel.

As the shock wave reaches the center of the target, the laser fires at the target, producing heat and a magnetic field. With the right pressure and heat, fusion takes place.

The Cambridge Heavy design produces high pressures with relatively low laser power, Cai said. This concept emerged from the laboratory of MIT chemist Keith Nelson. There, researchers used laser pulses to study materials under extreme conditions. As they increased the pressures, they realized they were approaching fusion-ready conditions.

In about a decade, Cambridge Heavy plans to develop a power plant from this concept, although that would require an increased design. It will be larger than the current tabletop prototype, though not as large as other fusion powerhouses. It should be the size of two basketball courts, Kai said, and will test whether the approach can generate enough energy to support a power plant.

Before that happens, however, Cambridge Heavy plans to use its smaller-scale devices to make tritium, a rare isotope of hydrogen that is used in nearly all fusion power plants today. Tritium sells for about $30,000 per gram today.

Not every power plant needs that much tritium—on the order of grams per year—but the material is so rare that only about 40 kilograms exist today. A recent study predicts that without new sources, the fusion power industry will be about 28kg short in 2054. At current prices, tritium is worth $840 million.

Fusion startups are designing fuel systems that will help reactors be largely self-sufficient when it comes to tritium supplies, although they may require occasional recharging. But that process could take up to ten years, Cai said, giving Cambridge Heavi years of potential revenue while it pursues its power plant.

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Tim de Chant is a senior weather reporter at TechCrunch. He has written for a wide range of publications, including Wired magazine, the Chicago Tribune, Ars Technica, The Wire China, and NOVA Next, for which he is editor.

De Chant also teaches at MIT's Graduate Program in Science Writing, and was awarded a Knight Science Journalism Fellowship at MIT in 2018. During this time, he studied climate technologies and explored new business models for journalism. He received his PhD in environmental science, policy and management from the University of California, Berkeley, and his BA in environmental studies, English and biology from St. Olaf College.

You can contact or confirm with Tim by emailing him at [email protected].

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