Production of ^(87)Rb Bose-Einstein Condensate in an Asymmetric Crossed Optical Dipole Trap

We report the production of ^(87)Rb Bose–Einstein condensate in an asymmetric crossed optical dipole trap(ACODT)without the need of an additional dimple laser.In our experiment,the ACODT is formed by two laser beams with different radii to achieve efficient capture and rapid evaporation of laser cooled atoms.Compared to the cooling procedure in a magnetic trap,the atoms are firstly laser cooled and then directly loaded into an ACODT without the pre-evaporative cooling process.In order to determine the optimal parameters for evaporation cooling,we optimize the power ratio of the two beams and the evaporation time to maximize the final atom number left in the ACODT.By loading about 6×10^(5) laser cooled atoms in the ACODT,we obtain a pure Bose–Einstein condensate with about 1.4×10^(4) atoms after 19 s evaporation.Additionally,we demonstrate that the fringe-type noises in optical density distributions can be reduced via principal component analysis,which correspondingly improves the reliability of temperature measurement.

Slurry flow characteristics control of 3D printed ceramic core layered structure:Experiment and simulation

Vat photopolymerization 3D printing ceramic technology provides a feasible process for the preparation of complex internal cooling channels for aeroengine single crystal superalloy hollow blades.However,the typical layered structure characteristics of 3D printing ceramic technology led to the anisotropy of ceramic core strength and sintering shrinkage,which greatly affects the performance and accuracy of the complex structure core and requires further research and improvement.Herein,the influence of the thickness of the slurry layer on the flow characteristics of the slurry in the process of the vat photopolymerization 3D printing slurry spreading was systematically studied by the method of simulation and experiment.The simulation results show that the positions of the turbulent zone and maximum velocity zone in the scraper front affect the redistribution of powder particles with different sizes.The layered structure was caused by the redistribution of ceramic particles of different sizes in the slurry layer.By controlling the turbulent flow zone and the maximum velocity zone of the scraper leading edge,the phenomenon of laminar flow can be weakened and the particle redistribution can be improved.With the increase of the thickness of the printing layer,the layered structure appears gradually,and the pores at the interface of the layered structure gradually concentrated into the interfacial pore lines from the uniform distribution,and the crack propagation changes from intergranular micro-crack to interlayer macro-crack.The combination of finite element simulation and experiment,through the slurry flow characteristics to control the layered structure of reductive vat photopolymerization ceramic core 3D printing,the control of crack propagation mode,element distribution and pore evolution of the core was accomplished,which lays a foundation for the performance control of ceramic 3D printing technology.