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

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A simple but effective method, ultrasonic vibration, has been used to prepare the nanoscale (hereafter n‐) Ga droplets. The n‐Ga droplets with average particle size of about 60–80 nm in diameter dispersed in polystyrenes (PS) have been successfully obtained. The low frequency internal friction of solid polystyrenes containing n‐Ga droplets was measured. We observed for the first time, that the internal friction peak caused by n‐Ga droplets appears around 313 K. The peak shifts to higher temperature with increasing frequency, indicating a relaxation peak. It is suggested that the internal friction peak is associated with the relaxation of n‐Ga droplets in the cavities of matrix under applied stress.