In conclusion, we have observed the production of 2.45 MeV deute rium fusion neutrons when a gas of deuterium clusters is irradiated with a 120 ml, 35 is laser pulse. When the focal position is optimized, we have observed as many as 10~4 neutrons per laser shot. This yield is consistent with some simple estimates for the fusion yield. We also find that the fusion yield is a sensitive function of the deuterium cluster size in the target jet, a consequence of the Coulomb explosion origin of the fast deuterons. We also find that the neutron pulse duration is fast, with a characteristic burn time of well under 1 ns. This experiment may represent a means for producing a compact, table-top source of short pulse fusion neutrons for applications. Furthermore, we have measured hard x-ray yield from femtosecond laser interactions with both solid and micron scale droplet targets. Strong hard x-ray production is observed from both targets. However, the inferred electron temperature is somewhat higher in the case of irradiation of the droplets. These data are consistent with PIC simulations. This finding indicates that quite unique hot electron dynamics occur during the irradiation of wavelength scale particles by an intense laser field and likely warrants further study We would like to acknowledge many useful conversations with John Perkins and Howard Powell as well as the technical assistance of Vince Tsai, Gerry Anderson and Rich Shuttlesworth. This work was supported by the Department of Energy under contract W-7405-Eng-48.
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