Gas bearing assembly for an EUV light source

A gas bearing assembly for an EUV light source, comprising:

• a stator body including:
• a first annular groove:
• in fluid communication with a first portion of a space between the stator body and the spindle;
• and,
• arranged to passively vent a bearing gas from the first portion;
• a second annular groove in fluid communication with a second portion of the space;
• and,
• a third annular groove in fluid communication with a third portion of the space, wherein the third annular groove is disposed between the first and second annular grooves in an axial direction parallel to the axis of rotation;
• a spindle rotatable about the stator body with respect to an axis of rotation;
• a pump in communication with the second annular groove and arranged to inject a barrier gas into the second portion via the second annular groove;
• and,
• a vacuum pump in fluid communication with the third annular groove and arranged to extract the bearing gas and the barrier gas from a third portion of the space to a create, in the third portion, a first pressure, wherein:
• the bearing gas is injected into the first portion at a second pressure, greater than the first pressure, to support rotation of the spindle with respect to the stator body.

A method for operating a gas bearing assembly for an EUV light source, comprising:

• injecting a bearing gas at a first pressure into a first space between a spindle and a stator body;
• supporting, with the injected bearing gas, rotation the spindle with respect to the stator body;
• venting the bearing gas from a first portion of the first space through a first annular groove in the stator body or the spindle;
• injecting a barrier gas at a second pressure into a second portion of the first space via a second annular groove in the stator body or the spindle;
• extracting the bearing gas and the barrier gas from a third portion of the first space via a third annular groove, in the stator body or the spindle, wherein the third annular groove is disposed between the first and second annular grooves in an axial direction parallel to an axis of rotation of the spindle;
• and,
• creating, in the third portion, a third pressure less than the first pressure and the second pressure.