Abstract: A broadband light source includes a confocal sensor assembly configured to measure a surface of a rotatable drum coated with plasma-forming target material. The broadband light source includes a laser source configured to direct pulsed illumination to the rotatable drum for exciting the plasma-forming target material and emitting broadband light as the drum is rotated in an angular direction and translated in an axial direction. The broadband light source includes a controller configured to direct the confocal sensor assembly to transmit a confocal optical signal to the rotatable drum, record a calibration measurement of a distance from the confocal sensor assembly to the rotatable drum, direct a cryogenic cooling sub-system to cryogenically cool the rotatable drum, record one or more distance measurements from a sensor head to the rotatable drum, convert the distance measurements to temperature values, and determine whether a target process condition temperature is achieved.

Abstract: A light source includes a rotatable drum to be coated with xenon ice and illuminated by a laser beam to produce a plasma. The drum may also be translatable. The light source further includes a confocal chromatic sensor to measure distances from the confocal chromatic sensor to the rotatable drum. The confocal chromatic sensor may include a sensor head to focus light onto the rotatable drum and to detect reflected light from the rotatable drum. The sensor head and the rotatable drum may be disposed within a vacuum chamber.