A device and method for flash evaporating a reagent includes an evaporation chamber that houses a dome on which evaporation occurs. The dome is solid and of high thermal conductivity and mass, and may be heated to a temperature sufficient to vaporize a specific reagent. The reagent is supplied from an external source to the dome through a nozzle, and may be supplied as a continuous stream, as a shower, and as discrete drops. A carrier gas may be introduced into the evaporation chamber and create a vortex flow therewithin. After evaporation, the gas vapor may be removed from the evaporation chamber through a regulating valve to a reaction chamber. Another embodiment of the invention includes a plurality of evaporating domes that separately receive reagent, and may receive reagents of differing composition.