Title: NIST’s Beamline 2: Absolute Source-Based Radiometry for Precision Calibration
NIST’s Beamline 2 facility provides absolute source-based radiometry for calibrating solar-observing instruments and deuterium ultraviolet light sources. The 17.85 m vacuum chamber allows precise measurements of absolute irradiance using measurable operational parameters like radio frequency, magnetic flux density, electron beam current, and solid angle.
The facility includes a class 10,000 cleanroom suite with removable gimbals for angular motion, and achieves calibration accuracies ranging from 0.6% at 2 nm to 0.1% at 400 nm wavelength. Beamline 2 also performs spectral irradiance measurements traceable to the SI using a dispersive transfer detector system based on a monochromator and silicon photodiode, allowing calibration of lamps from 200 nm to 400 nm with a relative combined uncertainty typically between 7% and 6%.
The system operates at reduced electron energy of 229 MeV to protect windows, yielding a relative standard uncertainty below 0.25% in the SURF III irradiance primary standard.
Source: https://www.nist.gov/laboratories/tools-instruments/beamline-2-absolute-source-based-radiometry
Keywords: Synchrotron radiation, Absolute irradiance, Vacuum chamber
