[en] The single-phase γ'-Fe₄N nanocrystal magnetic films with grain size of d = 40-60 nm were synthesized on single crystal NaCl (1 0 0) substrate by DC magnetron sputtering at 150 deg. C. The structure, morphology of the single-phase γ'-Fe₄N films were characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD), and the magnetic properties of samples prepared at different substrate temperatures were investigated by superconducting quantum interference device (SQUID). It is shown that substrate temperature has a significant influence on the crystalline structure and magnetic properties for Fe-N films. As substrate temperature was increased, the saturation magnetization for the deposited films increased, but the coercivity reduced

[en] A large high-altitude air-shower observatory (LHAASO) is to be built at Shangri-La, Yunnan Province, China. This observatory is intended to conduct sub-TeV gamma astronomy, and as an important component of the LHAASO project, a water Cherenkov detector array (WCDA) is proposed. To investigate engineering issues and fully understand the water Cherenkov technique for detecting air showers, a prototype array at 1% scale of the LHAASO-WCDA has been built at Yang-Ba-Jing, Tibet, China. This paper introduces the prototype array setup and studies its performance by counting rate of each photomultiplier tube (PMT), trigger rates at different PMT multiplicities, and responses to air showers. Finally, the reconstructed shower directions and angular resolutions of the detected showers for the prototype array are given. -- Highlights: • The technique of the water Cherenkov array is studied. • Engineering issues of the water Cherenkov array are investigated. • The PMTs and electronics of the water Cherenkov array are tested. • Some key parameters of the water Cherenkov array are measured