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Laser-heated nanowires produce micro-scale nuclear fusion

Record-setting efficiency for generation of neutrons

Colorado State University

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IMAGE: This is the target chamber (front) and ultra-high intensity laser (back) used in the micro-scale fusion experiment at Colorado State University view more 

Credit: Advanced Beam Laboratory/Colorado State University

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, CSU scientists and collaborators have 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. The paper's first author is Alden Curtis, a CSU graduate student.

Laser-driven controlled fusion experiments are typically done at 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 of students, research scientists and collaborators, work with an ultra fast, high-powered tabletop laser they built from scratch. They use their fast, pulsed laser to irradiate a target of invisible wires and instantly create extremely hot, dense plasmas - with conditions approaching those inside the sun. These plasmas drive fusion reactions, giving off helium and flashes of energetic neutrons.

In their Nature Communications 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 an array of nanowires made out of a material called deuterated polyethylene. The material is similar to the widely used polyethylene plastic, but its common hydrogen atoms are substituted by deuterium, a heavier kind of hydrogen atom.

The efforts were supported by intensive computer simulations conducted at the University of Dusseldorf (Germany), and at CSU.

Making fusion neutrons efficiently, at a small scale, could lead to advances in neutron-based imaging, and neutron probes to gain insight on the structure and properties of materials. The results also contribute to understanding interactions of ultra-intense laser light with matter.

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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.

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