An MBE effusion cell is configured to produce an inverted temperature gradient; that is, the top surface of the melt is not cooler than the bottom surface of the melt. In one embodiment, the MBE effusion cell comprises a crucible having tip, central and base regions. First filaments are located laterally adjacent the tip region; second filaments are located laterally adjacent the central region; and third filaments are located laterally adjacent all three of the regions. The radial density of the number of the heater filaments is lower adjacent the base region than adjacent the tip or central regions. In another embodiment, further tailoring of the inverted temperature gradient is obtained by reducing the amount of insulation at the base of the crucible. In another embodiment, at least one heater filament extends substantially along the longitudinal axis of the crucible and is located adjacent its lateral wall. Dielectric annular spacers are located around the lateral wall and are distributed along the longitudinal axis. The spacers having a multiplicity of holes through which the filaments pass. The filaments and spacers are located within a gas-blocking enclosure.