In physics, the term "isotropy" means a system where the properties are the same in all directions. For fusion, neutron energy isotropy is an important measurement that analyzes the streams of neutrons coming from the device and how uniform they are. This is critical because so-called isotropic fusion plasmas suggest a stable, thermal plasma that can be scaled to higher fusion energy gains, whereas anisotropic plasmas, those emitting irregular neutron energies, can lead to a dead end.