Scientists in the United States identify and rectify defects in diamond-encased nuclear fuel capsules, aiming to boost energy yield

In a significant breakthrough for the field of nuclear fusion, scientists at the University of California San Diego have identified structural flaws in diamond capsules used in fusion experiments. This revelation, published in a recent study, sheds light on the behaviour of diamond under extreme conditions and its potential impact on the symmetry of implosions and the energy output of these experiments.

The study, conducted on single-crystalline diamond specimens, reveals that at a pressure of 115 GPa, defects are generated in the diamond structure due to high shear stresses. These defects are relaxed by stacking faults, dislocations, and twins. However, at a lower pressure of 69 GPa, the diamond only exhibited elastic deformation, retaining its defect-free lattice.

The experiments, which involved the use of powerful lasers to compress a diamond capsule containing deuterium and tritium fuel, also highlighted the importance of shear stresses superimposed on hydrostatic pressure in phase transformation and solid-state amorphization. This work marks the first experimental observation of shock-induced amorphization in diamond.

The atomic packing factor of diamond's cubic structure is 0.34, considerably lower than that of common metals (0.68 to 0.74). This inherent openness makes diamond a material susceptible to structural collapse under pressure. The researchers found that these defects can disrupt implosion symmetry and reduce energy yield or prevent ignition.

The findings of this study are particularly relevant to research at facilities like the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory. By understanding how and why these defects form, researchers can refine computer models simulating the implosion process, leading to improved capsule designs and models that can achieve more uniform implosions and maximize the energy output of fusion experiments.

This research not only advances our understanding of diamond's behaviour under extreme conditions but also underscores the importance of materials science in the pursuit of nuclear fusion as a viable source of energy. The study was led by researchers who made the first experimental observations of shock-induced amorphization in diamond at the University of California, Los Angeles (UCLA).

Scientists in the United States identify and rectify defects in diamond-encased nuclear fuel capsules, aiming to boost energy yield