Large Scale Damage Testing in a Production Environment

Abstract

We are using laser damage test systems on a production scale to scan large castings of laser glass for the presence of damage-causing platinum inclusions. These systems support glass melting production lines at two plants; one is in the U.S. (Schott Glass Technologies, Inc.) and the other is in Japan (Hoya Corporation). The damage test systems are designed to scan an entire glass casting using the pulsed output from a commercial Nd:YAG laser. The system is fully automated and operates unattended. Following testing, the glass casting is removed from the system and visually inspected for the presence of Pt-damage sites. We routinely test polygonally-shaped castings that are about 0.5 meter in size, weigh approximately 30 kg and contain about 7 liters of glass. It takes roughly 6 to 8 hours to test a piece of this size. To date the systems have been in use about 12 hours-per-day, up to 5 days-a-week for a period of about 15 months. Of the approximately 300 disks that have passed the damage test so far, sixty-two percent of the disks have no platinum inclusions at all and ninety-two percent have an inclusion density of less than 0.2 per liter.

High‐Power Solid‐State Lasers: a Laser Glass Perspective

“…Inspection methods have been developed and put into production to scan each piece of laser glass with a high‐fluence laser beam to detect the presence of inclusions 66 …”

“…Inspection methods have been developed and put into production to scan each piece of laser glass with a high-fluence laser beam to detect the presence of inclusions. 66 If Pt inclusions are eliminated, the next limiting factor is the damage resistance of the polished glass surface. 67 Consequently, optical material researchers have focused attention on further improving the quality of polished glass surfaces to increase the laser damage resistance.…”

The National Ignition Facility: the path to a carbon-free energy future

“…Laser glass was also pre-treated with an off-line laser scanning system [29]. Solid micrometre-sized inclusions of highly absorbing platinum are damaged during this pre-treatment process.…”

National Ignition Facility Performance Review 1999

“…Currently, we scan each piece of laser glass with a UCRL-ID-138120-99 6-10 high-fluence laser beam and measure the size of any damage site after a specified number of shots at fluences between 7 to 14 J/cm 2 (8 ns). [29][30][31] If the Pt-damage size remains below the specified size limit given in Table 6.1-2, then it is acceptable.…”