|The target chamber used to achieve laser fusion is shown in the foreground and the laser appears in the background. (Courtesy: Advanced Beam Laboratory/Colorado State University)|
Topics: Green Tech, Nanotechnology, Nuclear Fusion
Smaller, cheaper neutron sources and new opportunities for simulating the extreme conditions at the center of stars are among the possible benefits of new research carried out by physicists in the US and Germany. The group directed rapid-fire pulses of intense blue light from a compact laser at arrays of nanostructures to generate a dense plasma yielding large numbers of neutrons created by nuclear fusion.
Scientists have built ever more energetic lasers in the quest to demonstrate nuclear fusion’s feasibility as an energy source. The National Ignition Facility (NIF) in California, for example, generates pulses with a whopping 1.8 MJ of energy, in order to compress tiny pellets of deuterium and tritium to the point where the nuclei fuse and emit copious numbers of neutrons. The aim is to achieve ignition, when the alpha particle released by the fusing nuclei provides the heat for a self-sustaining reaction – with the energy of the emitted neutrons ultimately being tapped to produce electricity. However, NIF is enormous – occupying the area of three football pitches – and, like other high-energy lasers, can only fire a handful of times a day.
Some researchers are instead working on less energetic but more rapid-fire lasers. These will never get anywhere close to ignition, but can still achieve exceptionally high intensities – thanks to the extreme brevity and hence power of their pulses. Such lasers can create plasmas with very high energy densities ideal for studying extreme astrophysical environments, for example. These devices could also potentially be used as compact sources of neutrons, which probe atomic structure in ways not possible with X-rays. Neutrons are usually produced at large accelerators or reactors and a compact source would be welcomed by scientists.
Nanowires boost nuclear fusion, Hamish Johnston, Physics World