I'm sure this is an odd idea but I'm wondering if anyone knows of a material that I can fire the laser at but that won't burn. Would need it to be something I could make into a small disk shape or that I could get in that shape.

I was playing with the laser the other day and put a slab of marble on the bed. Just for grins I pulled out my FLIR camera. It was pretty interesting. I could see exactly where the beam was hitting with the thermal imager. Gave me the idea that if I could find a material that would fit the circular opening over the mirrors that I could use it to see the beam alignment.