We report the first results of a light weakly interacting massive particles (WIMPs) search from the CDEX-10 experiment with a 10 kg germanium detector array immersed in liquid nitrogen at the China Jinping Underground Laboratory with a physics data size of 102.8 kg day. At an analysis threshold of 160 eVee, improved limits of 8×10^{-42} and 3×10^{-36}  cm^{2} at a 90% confidence level on spin-independent and spin-dependent WIMP-nucleon cross sections, respectively, at a WIMP mass (m_{χ}) of 5  GeV/c^{2} are achieved. The lower reach of m_{χ} is extended to 2  GeV/c^{2}.

We report results on the searches of weakly interacting massive particles (WIMPs) with sub-GeV masses (m χ) via WIMP-nucleus spin-independent scattering with Migdal effect incorporated. Analysis on time-integrated (TI) and annual modulation (AM) effects on CDEX-1B data are performed, with 737.1 kg day exposure and 160 eVee threshold for TI analysis, and 1107.5 kg day exposure and 250 eVee threshold for AM analysis. The sensitive windows in m χ are expanded by an order of magnitude to lower DM masses with Migdal effect incorporated. New limits on σ SI χN at 90% confidence level are derived as 2 × 10 −32 ∼ 7 × 10 −35 cm 2 for TI analysis at m χ ∼ 50-180 MeV=c 2 , and 3 × 10 −32 ∼ 9 × 10 −38 cm 2 for AM analysis at m χ ∼ 75 MeV=c 2-3.0 GeV=c 2 .

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In this paper, the fabrication technique of high-frequency moiré gratings with a focused ion beam (FIB) is studied thoroughly and comprehensively. The concept is proposed for the first time that the frequency and the size of the grating must be designed to meet the requirements of measurement accuracy and the view field at the same time. Some skills are summarized to get high quality gratings. To check its ability for high temperature use, a grating with a frequency of 2000 lines mm −1 is fabricated on the amorphous SiC micro-beam. SEM moiré are recorded at room temperature and after high temperature of 350 • C and 550 • C respectively. The fringes are distinct at all stages except for a contrast degradation after high temperature, which demonstrates that SEM moiré combined with the grating fabricated by FIB milling is a promising tool to measure microscopic deformation of micro-device at room temperature and high temperature.

Ultrasonic vibration cavitation erosion experiments were performed to study the erosion on a steel specimen at different pitch angles. Experimental results show that the number and size of the erosion pits decrease as the pitch angle increases. This result is thought to be related to the hydrodynamic pressures generated near the solid surface. Numerical analyses from the Reynolds equation prove that the hydrodynamic pressures are generated in the fluid film when a bubble is moving towards the surface of the specimen. Simulation of the bubble collapse process shows that the hydrodynamic pressures shorten the collapse time of a bubble and strengthen the microjet at the moment of bubble collapse. As the pitch angle of the specimen surface increases, the squeeze pressure due to normal velocity decreases, and the increased dynamic pressure due to tangential velocity cannot compensate for the loss of the squeeze pressure. Thus, the total hydrodynamic pressure decreases, and a decrement in the number and the size of the erosion pits occurs.