An DPP EUV source is disclosed which may comprise a debris mitigation
apparatus employing a metal halogen gas producing a metal halide from
debris exiting the plasma. The EUV source may have a debris shield that
may comprise a plurality of curvilinear shield members having inner and
outer surfaces connected by light passages aligned to a focal point,
which shield members may be alternated with open spaces between them and
may have surfaces that form a circle in one axis or rotation and an
ellipse in another. The source may have a temperature control mechanism
operatively connected to the collector and operative to regulate the
temperature of the respective shell members to maintain a temperature
related geometry optimizing the glancing angle of incidence reflections
from the respective shell members, or a mechanical positioner to position
the shell members.