An apparatus for thermally processing a substrate includes a substrate support for holding the substrate and lamps disposed above the substrate support. The lamps are grouped into concentric lamp zones including a center zone comprised of a center lamp and peripheral lamps surrounding the center lamp. A center sleeve is coupled to the center lamp and peripheral sleeves are coupled to the peripheral lamps, respectively, for directing radiated heat to the substrate during thermal processing. The center sleeve has a higher surface roughness than that of the peripheral sleeves.