Radiation resistance of Nd-doped laser crystals for space application

The radiation resistance of Nd-doped laser crystals was measured using a proton beam in order to construct spaceborne laser systems. After irradiation of 30 krad, we measured the variation of transmittance for crystals. The variation for all crystals was less than 1%. Since 30 krad is the irradiation value received over 30 years in the International Space Station with a 1-mm-thick Al cover, we conclude that all of the laser crystals have sufficient resistance for a 3-year spaceborne lidar mission at the International Space Station