what is barium  fluoride
While barium fluoride windows are less resistant to water than calcium fluoride, BaF 2 windows are the most resistant optical fluoride to high-energy radiation, but feature lower UV transmittance. BaF 2 has a Knoop hardness of 82. Note: These optical windows are very sensitive to thermal shock. Barium fluoride is a fast scintillator and can be used to detect X-rays, gamma rays, or other high energy particles such as 511 keV gamma photons in Positron Emission Tomography (PET).