NOVELTY - A biomass reactor, for producing synthesis gas, has a cylindrical heat shield concentrically within the coil and above the burner in the upper one-third of the vessel. The end of the heat shield toward the burner is closed. The heat shield defines a zone of convective heating for the coil in the region where the coil is adjacent to the shield, and a radiant heating zone in the region where the coil is directly exposed to the heat.    USE - For the production of synthesis gas rich in carbon containing components, such as carbon monoxide, carbon dioxide, hydrogen or methane that may be converted into a selected and product fuel, such as methanol or ethanol, or as a feed gas for an industrial power plant.    ADVANTAGE - The novel biomass reactor can be used in varying sizes to meet local needs relating to availability of biomass feed and output gas, and feed industrial plant needs for steam or electricity.    DETAILED DESCRIPTION - A biomass reactor, for producing synthesis gas by pyrolysis of a biomass feed transported through a closed reactor coil in a reactor vessel, comprises a vertically extending cylindrical reactor vessel having a top portion and a bottom portion and a cylindrical sidewall. The top portion includes a hood and a flue vent. A helical reactor coil is vertically within the vessel below the top portion. The reactor has an input end and an output end. The input end of the reactor coil is below the top portion and the output end below the bottom portion. A burner for providing the heat for pyrolysis is in the bottom portion of the vessel. A cylindrical heat shield is concentrically within the coil and above the burner in the upper one-third of the vessel. The end of the cylindrical heat shield toward the burner is closed. The heat shield defines a zone of convective heating for the coil by the heat from the burner in the region where the coil is adjacent to the shield, and a radiant heating zone in the region where the coil is directly exposed to the heat produced by the burner.    DESCRIPTION OF DRAWING(S) - The figure shows the above biomass gasifier.