Laser induced damage enhancement due to stainless steel deposition on KS-4V and KU1 quartz glasses

LIDAR (light detection and ranging) diagnostic systems for fusion devices will require windows with extremely high transmission in the visible range as a consequence of the use of high power lasers. Within the ITER diagnostics programme, KU1 and KS-4V quartz glasses (OH contents: 800–900 ppm for KU1 and <0.2 ppm for KS-4V) are being examined for such applications. A comparison between the two materials has been carried out in terms of laser induced damage and it was observed that both materials exhibited almost identical behaviour. Laser induced damage enhancement due to stainless steel deposition on both materials has been studied, as well as the possibility of `in situʹ cleaning. Important differences between sputtered and evaporated layers, as well as type of material deposited, were observed.