The target chamber (front) and ultra-high density laser (back) used in the micro-scale fusion experiments at CSU. Credit: Advanced Beam Laboratory
Nuclear fusion, the process that powers our sun, happens when nuclear reactions between light elements produce heavier ones. It's also happening at a smaller scale – in a Colorado State University laboratory.
Using a compact but powerful laser to heat arrays of ordered nanowires, Colorado State University (CSU) scientists and collaborators have this month demonstrated micro-scale nuclear fusion in the lab. They have achieved record-setting efficiency for the generation of neutrons – chargeless sub-atomic particles resulting from the fusion process. Their work is detailed in a paper published in Nature Communications, and is led by Jorge Rocca, University Distinguished Professor in electrical and computer engineering and physics.
Laser-driven controlled fusion experiments are typically done with multi-hundred-million-dollar lasers housed in stadium-sized buildings. Such experiments are usually geared toward harnessing fusion for clean energy applications. In contrast, Rocca's team worked with an ultra-fast, high-powered, tabletop laser they built from scratch.
The CSU team used their fast, pulsed laser to irradiate a target of nanowires and instantly create extremely hot, dense plasmas – with conditions approaching those inside the sun. These plasmas were seen to drive fusion reactions, giving off helium and flashes of energetic neutrons.
In their experiment, the team produced a record number of neutrons per unit of laser energy – about 500 times better than experiments that use conventional flat targets from the same material. Their laser's target was made of deuterated polyethylene. This material is similar to the widely-used polyethylene plastic – but its common hydrogen atoms are substituted by deuterium, a heavier kind of hydrogen atom.
These efforts were supported by intensive computer simulations conducted at the University of Dusseldorf (Germany), as well as CSU.
Making fusion neutrons efficiently, at a small scale, could lead to advances in neutron-based imaging, and neutron probes to gain insight into the structure and properties of materials. The results also contribute to understanding interactions of ultra-intense laser light with matter.
The paper is titled "Micro-scale fusion in dense relativistic nanowire array plasmas." The research was supported by the Air Force Office of Scientific Research and by Mission Support Test Services, LLC.
Top left: A scanning electron microscope image of aligned deuterated polyethylene nanowires. The other panels are 3-D simulations of the nanowires rapidly exploding following irradiation by the ultra-intense laser pulse. Credit: Advanced Beam Laboratory Source: n
