A heater including a plurality of first dielectric vanes and a plurality of second dielectric vanes arranged about a longitudinal axis, each first dielectric vane and second dielectric vane having a plurality of wire guiding grooves, a heater wire structure wound around the first and second dielectric vanes in wire guiding grooves, and wherein the heater wire structure substantially avoids contact with bottoms of the wire guiding grooves of the second dielectric vanes.
