A magnetically embedded coaxial z‐pinch configuration is proposed for the resonant photoexcitation laser at 228 A˚ in Mg ixpumped by the 48.338 A˚ line of Al xi. This laser configuration consists of an annular Al z‐pinch plasma imploded (final electron density of about 1020cm−3) onto an inner, Mg plasma (final electron density of about 1018cm−3) on the axis. The Mg plasma is confined and stabilized by an axial magneticBzfield, which is compressed to a final magnitude of about 130 T from an initially applied field of about 1 T by the Al implosion, thus serving to stabilize and physically separate the Al and Mg plasmas. Separate numerical simulations of the Al and Mg plasmas designed to guide exploratory experiments are reported. A 0D dynamic z‐pinch model captures the Al implosion, including trappedBzfield and power losses due to line radiation. Initial conditions required to produce the intense Al xipump line at 48.338 A˚ are derived assuming an 800 kA, 100 ns implosion current pulse. Assuming a pinch length of 2 cm, a pump power of 3.5 GW/eV is predicted for the 48.338 A˚ Al xiline. With the pump so defined, a separate, detailed atomic physics model is used to study the photoexcitation kinetics in the Mg ixlasant plasma. It is found that a gain of 1.0–1.5 cm−1is obtainable on the 2s3d 1D2 ‐ 2s4f 1F3transition at 228 A˚ in Mg ix.