The DArk Matter Particle Explorer (DAMPE), one of the four scientific space
science missions within the framework of the Strategic Pioneer Program on Space
Science of the Chinese Academy of Sciences, is a general purpose high energy
cosmic-ray and gamma-ray observatory, which was successfully launched on
December 17th, 2015 from the Jiuquan Satellite Launch Center. The DAMPE
scientific objectives include the study of galactic cosmic rays up to $\sim 10$
TeV and hundreds of TeV for electrons/gammas and nuclei respectively, and the
search for dark matter signatures in their spectra. In this paper we illustrate
the layout of the DAMPE instrument, and discuss the results of beam tests and
calibrations performed on ground. Finally we present the expected performance
in space and give an overview of the mission key scientific goals.Comment: 45 pages, including 29 figures and 6 tables. Published in Astropart.
Phy
Human exploration of the Moon is associated with substantial risks to astronauts from space radiation. On the surface of the Moon, this consists of the chronic exposure to galactic cosmic rays and sporadic solar particle events. The interaction of this radiation field with the lunar soil leads to a third component that consists of neutral particles, i.e., neutrons and gamma radiation. The Lunar Lander Neutrons and Dosimetry experiment aboard China’s Chang’E 4 lander has made the first ever measurements of the radiation exposure to both charged and neutral particles on the lunar surface. We measured an average total absorbed dose rate in silicon of 13.2 ± 1 μGy/hour and a neutral particle dose rate of 3.1 ± 0.5 μGy/hour.
Single crystalline silicon carbide (SiC) nanowires were grown directly on the surface of bulk SiC ceramic substrate in a catalyst-assisted thermal heating process. The morphology of the nanowire film and the diameter of nanowires were found to be sensitive to the thickness of catalyst film and both of them had a strong effect on field emission performance. Very low turn-on and threshold fields for electron emission were observed with SiC nanowires of small diameter. A model is proposed to qualitatively explain the field emission findings, which assumes the occurrence of an insulator-to-metal-like transition in a field emitting nanowire.
In this work, the Ti-6Al-4V alloy and ZrB 2 -SiC ultra-high temperature ceramic joint was brazed by TiCuZrNi amorphous filler at 910℃ with varied holding time. The element diffusion, microstructure and precipitation phase of the joints were analyzed in details. Reaction products in the joints were identified as β-Ti, (Ti,Zr) 2 (Cu,Ni), TiCu, Ti 2 Cu, TiC, Ti 5 Si 3 , TiB and TiB 2. The formation schemes of reaction products were investigated. The holding time has substantial impacts on interfacial microstructure and shear strength of joints. A maximum shear strength of 345 MPa of the joint was reached under a brazing temperature of 910℃ and holding time of 1200 s. It is also found that the shear strength depends on the amount of eutectic structure and brittle compounds in the joints.
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