[en] This paper summarizes the requirement of X-ray pulsar navigation and the development of X-ray detector. The difficulties of pulsar navigation in space environment are pointed out. The lack of detectors in terms of detection efficiency, time resolution and load is discussed. Finally, some suggestions are given for future research in X-ray pulsar navigation. (paper)

[en] Ultrathin MgB₂ superconducting films with a thickness down to 7.5 nm are epitaxially grown on (0001) Al₂O₃ substrate by a hybrid physical-chemical vapor deposition method. The films are phase-pure, oxidation-free and continuous. The 7.5 nm thin film shows a T_c(0) of 34 K, which is so far the highest T_c(0) reported in MgB₂ with the same thickness. The critical current density of ultrathin MgB₂ films below 10 nm is demonstrated for the first time as J_c ∼ 10⁶ A cm^-2 for the above 7.5 nm sample at 16 K. Our results reveal the excellent superconducting properties of ultrathin MgB₂ films with thicknesses between 7.5 and 40 nm on Al₂O₃ substrate.