Ultrafast laser welding of X-ray mirror segment stacks

Designing and building X-ray telescopes that observe the high-energy universe with large-effective area and sub-arcsecond angular resolution has proven to be a great optomechanical challenge, as thin, tightly-nested grazing-incidence mirrors are easily deformed during assembly. We are developing a bonding and alignment process in which we fabricate spacers, bond them between thin mirrors, and re-align these mirrors after assembly, using a Hartmann test for alignment metrology. We implemented a non-contact slumping method to produce smooth Eagle XG conical mirrors. Using an ultrafast laser, we weld fused silica spacers to these mirrors to create mirror segment stacks. We will present measurements of how this assembly process affects the figure of our thin mirrors, and report on progress on finite-element modeling of our mirror stack assemblies such that mirror alignment can be precisely predicted and implemented with ultrafast laser-generated strain. We will also report on progress toward building Hartmann metrology capabilities at the University of Arizona. The presented assembly process serves as a promising approach towards building next-generation X-ray telescope mirrors.