[Peter, Tara], we assembled 2 short reference cavities today. The bonding between the spacers and mirrors are strong and holding the mirrors nicely.
I got the cavity fixtures (made from delrin) from the machine shop today, so I asked Peter to help me assembling the cavities. All picture can be found here
I tested the bond by lifting the whole cavity by handling at the mirror on top only, and wiggling it a little bit. The bonds weren't broken. The hardest part was cleaning all surfaces to make sure that there was no dust.
From hindsight, I don't really need to see the fringes to do the bond. If the surface is clean, the pieces will be bonded instantly after a light pressure. If there are particles on the surface that cause fringes, the bond will not form anyway. So for Si cavity, Dmass can try to do optical contact without a setup to see the fringes.
fig1: the mirror is placed in position by the fixture. The mirror is not pressed on the spacer yet. Fringes can be seen on the polished ring on the mirror. See the video to see how the fringes vanish after applied pressure.