Source Based Radiometry

Due to the possibility that synchrotron radiation generated by the electron beam in the dipole magnets of an electron storage ring can be calculated by relativistic electrodynamics, PTB can use BESSY II and in near future the Metrology Light Source (MLS) as a primary radiation source standard. Radiation sources can be calibrated against the primary source standard by spectrally resolved intercomparison.

Currently, PTB operates at BESSY II a normal-incidence-monochromator measuring station with a wavelength range from 40 nm to 400 nm. With this equipment, different UV and VUV radiation sources like deuterium lamps, tungsten ribbon lamps, hollow cathode discharge sources and specially developed sources for the calibration of space based telescopes have been calibrated. Once the MLS is operating, such tasks will be performed there at a newly designed measuring station with an enlarged spectral range from 7 nm to 400 nm.

Energy or wavelength dispersive detectors, like spectrographs or Si(Li) detectors can be calibrated by putting them directly into the undispersed calculable synchrotron radiation, using the full spectral range from the UV to the soft X-ray region.

Normal incidence monochromator measuring station for source calibration against the primary source standard BESSY II