The new ultraviolet spectral responsivity scale based on cryogenic radiometry at Synchrotron Ultraviolet Radiation Facility III

Abstract

The recently completed upgrade of the Synchrotron Ultraviolet Radiation Facility ͑SURF III͒ at the National Institute of Standards and Technology ͑NIST͒ has improved the accuracy of radiometric measurements over a broad spectral range from the infrared to the soft x ray. The beamline 4 at SURF III is a cryogenic-radiometer based radiometric facility for the ultraviolet ͑UV͒ spectral range. The upgrade of SURF III has allowed us to use beamline 4 to improve the detector spectral power responsivity scales in the wavelength range from 125 to 320 nm. The achieved combined relative standard uncertainty is better than 0.5% over most of this spectral range. This is a significant improvement over the more than 6% relative standard uncertainty in this spectral range of the current scales maintained at the Spectral Comparator Facility ͑SCF͒ in the Optical Technology Division and the Far UV Calibration Facility in the Electron and Optical Physics Division. The new UV scale of beamline 4 was subsequently intercompared and transferred to the SCF and to the Far UV Calibration Facility to improve their UV scales and ensure consistency within NIST. The new scale established at beamline 4 improves NIST's calibration capabilities for environmental monitoring, astrophysics, and the UV industry. The new scale also includes wavelengths such as 193 and 157 nm excimer laser wavelengths, which are of particular interest to the semiconductor photolithography industry.

Technical Report: UV and VUV Radiometry Programs at the Synchrotron Ultraviolet Radiation Facility (SURF III)

“…The relative expanded uncertainty for a typical silicon photodiode is 1% at k = 2 below 200 nm [14].…”

Ultraviolet degradation study of photomultiplier tubes at SURF III

“…Beamline 4 monochromatizes the radiation from SURF III with a 2-m monochromator and uses the resulting UV radiation for radiometric measurements of detectors [7]. In the past, beamline 4 was used primarily for the calibration of solid state UV detectors with its primary scale derived from a cryogenic radiometer [8]. Typical power of light used at beamline 4 to probe detectors is on the order of 1 µW, which, while suitable for most solid state detectors, can easily saturate low-light detectors like PMTs.…”

Characterization of an ultraviolet and a vacuum-ultraviolet irradiance meter with synchrotron radiation

“…The characterization and calibration of this new irradiance meter were performed at a detector-based radiometry beamline by use of continuously tunable synchrotron radiation from the Synchrotron Ultraviolet Radiation Facility ͑SURF͒ 3 at the National Institute of Standards and Technology ͑NIST͒. This beamline 4,5 was designed primarily to calibrate the power response of UV detectors from 130 to 320 nm. Typically, the calibration of irradiance responsivity requires radiation sources with uniform power distribution across the entrance area of the irradiance meter.…”