Avalanche Energy Achieves Measured Apparent Ion Temperatures Above 1 keV in Compact Fusion Experiment

Milestone demonstrates the potential of rapidly iterated, small-form-factor fusion systems

SEATTLE, June 10, 2026 /PRNewswire/ -- Avalanche Energy, a fusion technology company developing compact fusion plasma devices, today announced that its compact fusion plasma device, "Jyn", has demonstrated measured ion energies corresponding to apparent ion temperatures exceeding 1 kiloelectron volt (keV), or approximately 11 million degrees Celsius—comparable to temperatures found in the core of the Sun. The achievement marks an important technical milestone in the company's effort to develop practical, manufacturable fusion systems through rapid hardware iteration.

Fusion occurs when atomic nuclei collide with sufficient energy to overcome their natural electrostatic repulsion, and as ion temperatures increase, so does the probability of those reactions occurring. Reaching temperatures above 1 keV represents a significant performance threshold for any fusion system and achieving it in a compact fusion plasma device less than five inches in diameter validates both the plasma performance and the development philosophy behind it.

Rather than relying on decade-long cycles between major experiments, Avalanche builds and tests compact systems that can be modified, rebuilt, and improved in rapid succession, carrying lessons from each machine forward to accelerate progress while reducing costs.

"Many fusion programs pursue progress through increasingly large and complex facilities," said Robin Langtry, co-founder and CEO of Avalanche Energy. "This result demonstrates the value of a different approach: building small machines, testing them quickly, learning from each iteration, and continuously improving performance. Jyn is small enough to fit on a truck, yet it has achieved ion temperatures exceeding 11 million degrees Celsius."

"This milestone is the product of hundreds of design decisions, experiments, and hardware improvements made across multiple generations of machines," said Brian Riordan, co-founder and COO of Avalanche Energy. "Our ability to rapidly iterate on compact fusion systems allows us to learn quickly, improve quickly, and push performance forward at a pace that would be impossible to achieve with larger and more capital-intensive approaches."

At less than five inches in diameter, the Jyn machine has seen over 25 iterations since it was first built last fall on its path to reaching 1keV. Avalanche has published a technical report detailing the experimental setup, diagnostic methodology, calibration procedures, assumptions, analysis techniques, and interpretation of the results that was externally reviewed by an independent technical advisor. The measurements were conducted with calibrated Optical Emission Spectrometers viewing the plasma along 5 lines-of-sight described in the company's technical report.

The company views this result as a validating step toward its long-term goal of developing compact fusion systems for defense, space, industrial, and power-generation applications.

About Avalanche Energy

Avalanche Energy is a venture-backed fusion energy company based in Seattle, Washington. The company develops compact fusion machines designed for rapid iteration, manufacturing scalability, and deployment in applications requiring high energy density, including defense systems, space missions, autonomous platforms, neutron generation, isotope production, and future fusion power systems. To learn more, visit avalanchefusion.com.

SOURCE Avalanche Energy