Fusion has long been hailed as an ideal energy source, mirroring the same reaction that powers the sun. Its potential to provide safe, clean, cheap, and reliable energy has captivated scientists since the 1960s. One approach explored extensively involves using high-powered lasers to compress thermonuclear material, aiming to achieve ignition. This critical point occurs when the energy output from inertial fusion exceeds the energy delivered to the target.
A significant breakthrough was accomplished in December 2022 at the National Ignition Facility, located at Lawrence Livermore National Laboratory, where scientists successfully achieved ignition. However, numerous challenges persist in making fusion energy technically and commercially viable for widespread production and consumption.
Addressing these obstacles, researchers at the University of Rochester’s Laboratory for Laser Energetics (LLE) have recently conducted an experimental study introducing a method known as dynamic shell formation. This pioneering technique has the potential to contribute to the realization of a practical fusion power plant.
The team of researchers, including Igor Igumenshchev, a senior scientist at LLE, and Valeri Goncharov, a distinguished scientist and theory division director at LLE, along with Valeri Goncharov, an assistant professor (research) in the Department of Mechanical Engineering, has outlined their findings in a paper published in Physical Review Letters.
Igumenshchev emphasizes the significance of this experiment, stating that it showcases the feasibility of an innovative target concept that is suitable for affordable mass production of inertial fusion energy.
The conventional approach to inertial fusion energy
In the traditional approach to inertial fusion energy, a target is created by freezing a small amount of hydrogen fuel, specifically deuterium and tritium isotopes, into a solid spherical shell. This target is then subjected to laser bombardment, leading to the heating of the fuel at the core to extremely high temperatures and pressures. Under these extreme conditions, the shell collapses and triggers fusion.
This fusion process releases an immense amount of energy with the potential to power a carbon-free plant. However, the realization of a fusion power plant, which remains hypothetical at this stage, necessitates the fabrication of nearly a million targets every day. The current methods employed for producing these targets involve a costly frozen preparation process, making them challenging to manufacture.
Dynamic shell formation: More feasible, less costly
Dynamic shell formation offers an alternative approach for target creation, where a liquid droplet containing deuterium and tritium is injected into a foam capsule. When exposed to laser pulses, the capsule transforms into a spherical shell, undergoing implosion and collapse, leading to ignition. Unlike conventional methods, dynamic shell formation eliminates the need for expensive cryogenic layering since it utilizes liquid targets. This makes the production of targets more feasible and cost-effective.
While Goncharov introduced the concept of dynamic shell formation in a 2020 paper, its experimental demonstration was pending. In a scaled-down proof-of-principle experiment conducted by Igumenshchev, Goncharov, and their colleagues at LLE, they employed the OMEGA laser to mold a plastic foam sphere with the same density as deuterium-tritium liquid fuel into a shell. This successful demonstration represents a crucial milestone in validating the dynamic shell concept.
To achieve fusion through dynamic shell formation, future research will require lasers with longer and more energetic pulses. Nevertheless, the current experiment signifies the potential feasibility of dynamic shell formation as a promising pathway toward practical fusion energy reactors.
Igumenshchev emphasizes that when combined with an upcoming highly efficient laser system currently being developed at LLE, this target concept presents an appealing route towards achieving fusion energy.
Source: University of Rochester