Scientists at the University of California San Diego have identified critical structural flaws in diamond capsules used for fusion experiments, potentially hindering the advancement of fusion energy. The research, led by Boya Li and Marc Meyers, focuses on how diamond amorphization occurs under the extreme conditions required for fusion research.
Diamond capsules are crucial components in high-energy fusion experiments, such as those conducted at the National Ignition Facility (NIF). These capsules contain fuel, typically deuterium and tritium, subjected to immense pressures and temperatures generated by powerful lasers. The objective is to achieve a symmetrical implosion, a precise collapse of the capsule, which is essential for initiating and sustaining a fusion reaction.
However, the intense forces involved can cause defects within the diamond structure, ranging from minor distortions to complete structural breakdown, known as amorphization. These imperfections can disrupt the necessary symmetry of the implosion, leading to reduced energy output or a failure to achieve ignition. Research indicates that at pressures around 69 gigapascals (GPa), diamond capsules may only undergo elastic deformation. At higher pressures, such as 115 GPa, the material can develop flaws and defects.
Understanding how pressure and heat trigger amorphization is vital for refining the design and improving the performance of future fusion experiments. By addressing these inherent weaknesses in diamond materials, scientists aim to enhance the uniformity of implosions, thereby maximizing energy yield and accelerating the development of fusion as a viable energy source.
Previous experiments at NIF have underscored the importance of capsule quality. A record-breaking energy shot in August 2021, for example, was partly attributed to a high-quality diamond capsule with fewer surface imperfections and internal voids compared to earlier experiments. The presence of such defects in previous targets was thought to have contributed to material mixing into the fuel, impeding proper compression and reducing the fusion rate. The ongoing research into diamond amorphization offers valuable insights for developing more robust and reliable capsules, bringing the scientific community closer to realizing the potential of clean, virtually limitless fusion energy.