Influence of UV absorbants on radiation stability of wave-length shifters

The additional radiation damage of PMMA based wave-length shifter Y-7 due to additives absorbing ultra-violet (Cerenkov) light has been investigated for low and high dose rate irradiations. UV absorbants with cut-off wave-lengths higher than 360 nm cause strong probably permanent reduction of the wave-length shifter attenuation length. PMMA materials show an increase of damage after the end of irradiation and a delayed recovery. Furthermore there is no recovery during for calorimeters realistic low dose rate irradiations in air down to 1 Gy/h