Breaking news from my own lab:

Many people have made fusion neutron sources; unfortunately they typically involve large particle accelerators or huge, building-sized lasers. In the last ten years, table-top lasers have been developed with very high power, but much lower energy than giant glass lasers. (Power is energy/time, and the tabletop lasers have very short pulse durations, giving them high power and high peak intensity -- for a short time).

Other groups have tried shooting these short-pulse lasers at fusion targets; deuterated plastic, or CD (Carbon and Deuterium). One paper from Germany reported that this led to D+D fusion, where two Deuterium (heavy hydrogen) atoms fuse to produce Helium³ and a 2.45MeV neutron. They saw ~140 neutrons per shot, with 200mJ of laser energy for each shot. [Reference: G. Pretzler, A. Saemann, A. Pukhov et al., Physical Review E 58, p.1165 (1998)]

Our lab tried a different tack; shooting clusters of pure Deuterium. The density of deuterium atoms was much lower than in the solid-target case, but clusters have a special property: they absorb laser energy very efficiently and then "explode"! Cluster explosion is a relatively new phenomenon, and it is known to produce fast-moving ions. We hoped that if we shot deuterium clusters, the fast ions from the "explosions" would collide and fuse.

Sure enough, with only 100mJ of energy (half that of the German group) we saw over 10,000 fusion neutrons per shot -- more than two orders of magnitude efficiency increase. These results have been published in Nature and Physical Review Letters.

So what does this mean? If we took the next step and shot Deuterium-Tritium clusters, the fusion cross-sections are lower and the neutrons are more energetic. Because our laser can fire 10 times a second, it seems likely that one could make an energetic neutron source of over ten million high energy neutrons per second -- all from a table-top system! Who knows what sort of applications might result...

For more information, drop me an email.