Development of Wolter I x-ray optics by diamond turning and electrochemical replication

Demonstration x-ray optics have been produced by diamond turning and replication techniques that could revolutionize the fabrication of advanced mirror assemblies. The prototype optics were developed as part of the Advanced X-ray Astrophysics Facility—Spectrographic program (AXAF-S). The initial part of the project was aimed at developing and testing the replication technique so that it could potentially be used for the production of the entire mirror array. This assembly will ultimately be comprised of up to 50 nested mirror shells. The mirrors are produced by electroforming a thin shell optic with a conical mandrel. The mandrel is diamond-turned electroless nickel over an aluminum substrate. The initial goal was to produce a surface finish on the replicated mirror shell of less than 10 Å rms (measured with a WYKO 3D at 20X). The electroformed mirror shell is made from pure nickel deposited in a state of minimum stress. A cryogenic separation technique is used to remove the finished mirror from the mandrel. The replication technology for the mirror components has the potential to revolutionize the fabrication of precision components. The extremely high precision required of x-ray optics may lead to advances in manufacturing techniques that could be utilized in the fabrication of other precision components. The key procedures of the fabrication process are presented with the appropriate testing results.