In a significant advancement in fusion research, scientists at Zap Energy have reported successful neutron isotropy measurements from their FuZE device, marking a pivotal milestone in the quest for sustainable fusion energy. Published on February 3, 2025, in the journal Nuclear Fusion, this research validates that the sheared-flow-stabilized Z pinches can produce stable thermal fusion, crucial for achieving higher energy yields.
Neutron isotropy indicates that neutrons generated during fusion reactions have uniform energy distribution in all directions, suggesting a thermodynamic equilibrium within the plasma. "Essentially, this measurement indicates that the plasma is in a thermodynamic equilibrium," stated Uri Shumlak, Zap's Chief Scientist. This equilibrium allows for the potential scaling of the plasma size without compromising stability.
Fusion occurs when hydrogen nuclei fuse into helium, releasing neutrons that carry 80% of the reaction's energy. Thermal fusion, the target of Zap's research, is characterized by isotropic neutron production, contrasting with beam-target fusion, which results in anisotropic neutron emissions and poses challenges for energy scalability.
Zap's team conducted 433 plasma shots using neutron detectors around the FuZE device, confirming that the neutrons produced were nearly isotropic. This result not only represents a key benchmark in fusion physics but also carries historical significance, as the Z pinch method has faced skepticism since its inception in the 1950s due to previous failures linked to instability.
Rachel Ryan, a senior scientist at Zap, emphasized the importance of these findings, stating, "If we saw neutrons primarily from a beam-target source, it would mean that our machine wouldn't be scalable." The research suggests that understanding neutron behavior could lead to enhanced stability in the fusion process, paving the way for practical applications in clean energy generation.
Looking ahead, the Zap team plans to conduct further tests at higher energies on their FuZE-Q device. Initial results are promising, and continued measurements will help determine the contribution of beam-target fusion to their energy yields.