Patent Number: 
Section: claims

1. A collector mirror assembly comprising:a collector mirror having a reflective surface and a hole having an edge, the hole extending through the reflective surface;a tubular body that extends through the hole, the tubular body having an inner surface and an outer surface, the tubular body constructed and arranged to guide a main gas flow in a direction substantially transverse to the reflective surface; andan opening between the outer surface of the tubular body and the edge of the hole, the opening arranged to guide a further gas flow that diverges with respect to the main gas flow, wherein the opening is arranged to guide the further gas flow substantially along the reflective surface. 2. The assembly according to claim 1, wherein at least part of one or both of the inner surface and the outer surface of the tubular body are tapered in a direction against the main gas flow. 3. The assembly according to claim 1, wherein one or more walls are provided between the outer surface of the tubular body and the edge of the hole, the one or more walls being constructed and arranged to divide the further gas flow in one or more sub-flows. 4. The assembly according to claim 1, wherein the collector mirror is constructed to focus radiation emitted from a first focal point to a second focal point, wherein the main gas flow is directed away from the reflective surface to one or both of the first focal point and the second focal point. 5. The assembly according to claim 1, wherein the opening is formed by the outer surface of the tubular body and the edge of the hole. 6. The assembly according to claim 1, wherein the opening is arranged to guide the further gas flow away from the tubular body. 7. A module constructed to produce extreme ultraviolet radiation, the module comprising:a supply configured to supply one or more droplets of an ignition material to a predetermined target ignition position;a radiation source configured to supply a laser beam arranged to be focused on the predetermined target ignition position and to produce a plasma by hitting a droplet located at the predetermined target ignition position so as to change the droplet into an extreme ultraviolet producing plasma; anda collector mirror assembly, comprisinga collector mirror having a reflective surface and a hole having an edge, the hole extending through the reflective surface;a tubular body that extends through the hole, the tubular body having an inner surface and an outer surface, the tubular body constructed and arranged to guide a main gas flow in a direction substantially transverse to the reflective surface; and an opening between the outer surface of the tubular body and the edge of the hole, the opening arranged to guide a further gas flow that diverges with respect to the main gas flow, wherein the opening is arranged to guide the further gas flow substantially along the reflective surface. 8. The module according to claim 7, wherein the collector mirror is constructed to focus radiation emitted from a first focal point to a second focal point, wherein the main gas flow is directed away from the reflective surface to one or both of the first focal point and the second focal point, the target ignition position being the first focal point. 9. The module according to claim 7, wherein the opening is formed by the outer surface of the tubular body and the edge of the hole, the target ignition position being the first focal point, the target ignition position being the first focal point. 10. The module according to claim 7, wherein the opening is arranged to guide the further gas flow away from the tubular body. 11. A lithographic projection apparatus comprising:a collector mirror assembly, comprising:a collector mirror having a reflective surface configured to focus radiation emitted from a first focal point to a second focal point, and a hole having an edge, the hole extending through the reflective surface,a tubular body having an inner surface and an outer surface, the tubular body constructed and arranged to guide a main gas flow in a direction substantially transverse to the reflective surface, andan opening between the outer surface of the tubular body and the edge of the hole, the opening arranged to guide a further gas flow that diverges with respect to the main gas flow, wherein the opening is arranged to guide the further gas flow substantially along the reflective surface;a support configured to support a patterning device, the patterning device being configured to pattern the radiation after the radiation has passed through the second focal point to form a patterned beam of radiation; anda projection system configured to project the patterned beam of radiation onto a substrate. 12. The lithographic projection apparatus according to claim 11, wherein the opening is arranged to guide the further gas flow away from the tubular body. 13. A method for producing extreme ultraviolet radiation, comprising:directing a radiation beam, such as a laser beam, onto a droplet of an ignition material, the droplet being located at a predetermined target ignition position, so as to change the droplet into a plasma that is configured to produce an extreme ultraviolet radiation;reflecting the radiation and directing a gas flow toward the predetermined target ignition position using an collector mirror assembly, the assembly comprising:a collector mirror having a reflective surface and a hole having an edge, the hole extending through the reflective surface,a tubular body having an inner surface and an outer surface, the tubular body constructed and arranged to guide a main gas flow in a direction substantially transverse to the reflective surface, andan opening between the outer surface of the tubular body and the edge of the hole, the opening arranged to guide a further gas flow that diverges with respect to the main gas flow, wherein the opening is arranged to guide the further gas flow substantially along the reflective surface. 14. The method according to claim 13, wherein the collector mirror is constructed to focus radiation emitted from a first focal point to a second focal point. 15. The method according to claim 14, wherein the method comprises:providing the main gas flow through the tubular body and/or the further gas flow through the opening, the main gas flow being directed towards one or both of the first and second focal point. 16. The method according to claim 13, wherein the opening is arranged to guide the further gas flow away from the tubular body.