Process chamber and method for processing a material by a directed beam of electromagnetic radiation, in particular for a laser sintering device

Method for processing a material by means of a directed beam of electromagnetic radiation having the steps:

• directing a directed beam of electromagnetic radiation through a coupling window into a process chamber, wherein the coupling window has a surface that is facing the inside of the process chamber,
• supplying a first gas flow into the process chamber such that the first gas flow coming from a first side is substantially tangentially stroking over the surface of an optical element from the first side to a second side opposite the first side, and
• supplying a second gas flow into the process chamber such that the second gas flow flows at a distance to the surface in substantially the same direction as the first gas flow,
• wherein a process chamber for a processing of a material by means of a directed beam of electromagnetic radiation is used, the process chamber comprising:
• the optical element arranged in a plane for coupling the beam into the process chamber, wherein the optical element has a surface that is facing the inside of the process chamber,
• a wall section surrounding the optical element in said plane, wherein the wall section has a first section adjoining to one side of the optical element, the first section being a slanted section, the surface of which extends under an angle from said plane or a convex section, and a second section adjoining the first section, the second section being a hollow section having the shape of a hollow cylinder section or any other shape forming a groove, an axis of the hollow cylinder section or grove extending substantially in parallel to the first side of the optical element,
• a first inlet for a gas, which is arranged at said first section at a position facing the optical element and which is directed substantially tangentially to the surface of the optical element, and
• a second inlet for gas, which is arranged at a position at said second section opposite to the position where said second section adjoins said first section and which is directed substantially in the same direction as the first inlet.