Component of an optical system

An assembly, comprising:

• an optical element having a center;
• a first channel system;
• and
• a second channel system,
• wherein:
• the first channel system is within an outer enclosure for the optical element;
• relative to the center of the optical element, the first channel system is entirely outside the optical element in a radial direction that extends from the center of the optical element;
• relative to the center of the optical element, the second channel system is entirely outside the first channel system in the radial direction;
• the first channel system is configured to have cooling fluid flow therethrough to dissipate heat absorbed by the optical element due to electromagnetic radiation incident on the optical element;
• the second channel system is configured to have a cooling fluid flow therethrough to at least partially thermally shield an area of the assembly from the heat absorbed by the cooling fluid in the first channel system;
• and
• along a direction perpendicular to the radial direction:
• i) the first channel system is not above the optical element;
• and
• ii) the first channel system is not below the optical element.