Lithographic apparatus, illumination system, and connection sealing device with protective shield

A system comprising:

• a first enclosure configured to enclose a first environment, wherein the enclosure comprises a first opening and a first connection structure corresponding to the first opening;
• a second enclosure comprising a second connection structure, wherein the second connection structure is configured to couple to the first connection structure to prevent mixing of substances between the first environment and a second environment outside of the first and second enclosures;
• a sealing device configured to be disposed between the first and second connection structures to prevent the mixing of the substances, wherein a material of the sealing device is chemically reactive to the first environment;
• and
• a protective device, wherein the protective device is configured to be disposed on the sealing device proximal to the first environment to shield the sealing device from the first environment.

An illumination system comprising:

• an extreme ultraviolet radiation source;
• a first enclosure configured to enclose a first environment, wherein the enclosure comprises a first opening and a first connection structure corresponding to the first opening;
• a second enclosure comprising a second connection structure, wherein the second connection structure is configured to couple to the first connection structure to prevent mixing of substances between the first environment and a second environment outside of the first and second enclosures;
• a sealing device configured to be disposed between the first and second connection structures to prevent the mixing of the substances, wherein a material of the sealing device is configured to be chemically reactive to the first environment;
• and
• a protective device, wherein the protective device is configured to be disposed on the sealing device proximal to the first environment to shield the sealing device from the first environment.