A concept for a deployable normal incidence EUV mirror based on shape memory alloy sheets

Based on the science case for the SMEX ESCAPE mission, a normal incidence EUV mirror mission would be an interesting follow on. Our provisional SmallSat/CubeSat design has a 1m diameter primary deployable mirror. The mirror would be coated with multilayers for normal incidence EUV reflectivity. The deployable mirror substrate is a shape memory alloy (SMA). The SMA needs to be over coated with a material that can be polished and then smoothed further. The combination that worked well on an aluminum cylinder is a high phosphorous content electroless nickel (eNiP) super-polished and then coated with carbon nitride (CNx). The multilayers were deposited on the eNiP+CNx stack. We report here our progress toward putting in place the pieces for a proof of concept. We discuss a scale up of previous return to shape on sheets of NiTi and the ray tracing results that demonstrate a sufficient return to shape of 1 micron. Furthermore, corrections post deployment are possible if desired.