A thermal evaporation source includes: a crucible configured to contain a volume of evaporant and a vapor space above the evaporant; a manifold body having within it a hollow expansion chamber that is flowably connected to the vapor space via one or more restriction orifices; one or more effusion nozzles flowably connected to the expansion chamber and exiting an outer surface of the thermal evaporation source, the nozzle(s) oriented to direct an evaporant vapor flow out of the source vertically downward, in one or more horizontal directions, or in one or more directions intermediate between horizontal and vertically downward; and a heater capable of heating some or all of the thermal evaporation source to a temperature sufficient to produce the one or more evaporant vapor flows when a vacuum is applied to the thermal evaporation source.