Construction and mechanical alignment method of wide-field X-ray monitor with lobster-eye optics onboard HiZ-GUNDAM

HiZ-GUNDAM is a candidate for a Japan Aerospace Exploration Agency satellite mission expected to launch in the 2030s, aiming to detect high-redshift gamma-ray bursts (GRBs) and explore the early universe. The wide-field X-ray monitor EAGLE, onboard the HiZ-GUNDAM satellite and responsible for GRB detection and localization, employs lobster-eye-type micro-pore optics (MPOs) and a pnCCD as the focal-plane detector to focus soft X-rays in the 0.4 to 4.0 keV range. We established an alignment strategy for a modular lobster-eye MPO system, and the required alignment accuracy was derived through Monte Carlo simulations that reproduce the point spread function and localization performance. The optical characteristics of individual MPO segments were then evaluated to select and arrange four segments for a breadboard-level alignment demonstration. Subsequently, alignment tuning was performed by adjusting the angular positions of the MPO segments with actuators under X-ray irradiation in a vacuum environment, followed by an evaluation of the resulting direction-determination accuracy. The resulting angular response measurements show that the estimated incident angles derived from the focal positions achieve systematic uncertainties of less than 3 arcmin over more than 95% of the field of view. This level of performance satisfies the localization requirement for the EAGLE instrument when considering systematic errors intrinsic to the MPO-based detection system. These results demonstrate the feasibility of precise MPO alignment in a segmented lobster-eye optics system and provide practical feedback for the design, alignment strategy, and mechanical tolerance definition of future engineering and flight models of the EAGLE X-ray optics.