Nuclear fusion from explosions of femtosecond laser-heated deuterium clusters

As a form of matter intermediate between molecules and bulk solids, atomic clusters have been much studied(1). Light-induced processes in dusters can lead to photo-fragmentation(2,3) and Coulombic fission(4), producing atom a nd ion fragments with a few electron volts (eV) of energy. However, recent studies of the photoionization of atomic dusters with high intensity (>10(1 6)Wcm(-2)) femtosecond laser pulses have shown that these interactions can be far more energetid(5-13)-excitation of large atomic dusters can produce a superheated microplasma that ejects ions with kinetic energies up to 1 Me V (ref. 10). This phenomenon suggests that through irradiation of deuterium dusters, it would be possible to create plasmas with sufficient average io n energy for substantial nuclear fusion. Here we report the observation of nuclear fusion from the explosions of deuterium clusters heated with a comp act, high-repetition-rate table-top laser. We achieve an efficiency of abou t 10(5) fusion neutrons per joule of incident laser energy, which approache s the efficiency of large-scale laser-driven fusion experiments. Our result s should facilitate a range of fusion experiments using: small-scale lasers , and may ultimately lead to the development of a table-top neutron source, which could potentially find wide application in materials studies.