After their ejection from the nucleation chamber the particles may need to be annealed, e.g., for thermal equilibration. As convective or conductive heating is not possible under high vacuum conditions, we have developed a light furnace for in-flight optical heating. Within this light furnace, the light of three halogene penlights is focussed through a vacuum-sealed quartz glass tube onto the free nanoparticle beam by a set of Au-plated ellicptical mirrors.
Left: Schematic cross-sectional drawing of the light furnace highlighting its construction principle: The flight path of the particles lies perpendicular to the drawing plane and conincides with the secondary foci of the three elliptical mirrors. Right: 3D sketch of the fully assembled furnace [F. Schmidt, Diploma thesis, TU Dresden (2013)].