Fused Silica Lightweight Mirror Blanks

The construction of lightweight mirrors requires materials with good welding properties that also are free from creeping effects. The described construction gives a good balance between weight reduction (50 to 60 percent) and rigidity. The ability of the mirror to withstand mechanical and thermal loads is proved by measurements of surface distortion under mechanical load, during radiation heating, heating through the support system, and temperature cycling. The impact and shear strength of the fused joints are examined by several tests.