title: Comparison of two high-precision nondestructive measurement methods for evaluating thermal expansion differences in the 8.3-m ultralow-expansion Subaru primary mirror blank.
abstract: The building blocks for fabricating the 8.3-m Subaru primary mirror blank are ultralow-expansin solid hexagonal units that were subjected to rigorous ultrasonic examination to establish thermal expansion characterization as reported by Hagy [Appl. Opt. 12, 1440 (1973)]. Following assembly of the mirror by fusion and fine annealing, photoelastic analyses at hex-to-hex seals were used to calculate thermal expansion differences. These differences are found to be in excellent agreement with the ultrasonically established differences.
authors.forename: H E
authors.initials: HE
authors.lastname: Hagy
authors.forename: M E
authors.initials: ME
authors.lastname: Best