Construction and On-site Performance of the LHAASO WFCTA Camera

The focal plane camera is the core component of the Wide Field-of-view Cherenkov/fluorescence Telescope Array (WFCTA) of the Large High-Altitude Air Shower Observatory (LHAASO). Because of the capability of working under moonlight without aging, silicon photomultipliers (SiPM) have been proven to be not only an alternative but also an improvement to conventional photomultiplier tubes (PMT) in this application. Eighteen SiPM-based cameras with square light funnels have been built for WFCTA. The telescopes have collected more than 100 million cosmic ray events and preliminary results indicate that these cameras are capable of working under moonlight. The characteristics of the light funnels and SiPMs pose challenges (e.g. dynamic range, dark count rate, assembly techniques). In this paper, we present the design features, manufacturing techniques and performances of these cameras. Finally, the test facilities, the test methods and results of SiPMs in the cameras are reported here.Comment: 45 pages, 21 figures, articl

Proposals for improving the efficiency and service life of the turbines of turbo-pump assemblies in liquid-propellant rocket engines by using double-sided crest-type radial labyrinth seals

Nowadays the improvement of the design of liquid-propellant rocket engines (LPREs) depends on a variety of factors and activities, among which we can distinguish, for example, the improvement of energy characteristics of units and assemblies forming part of the LPREs. The article compares the operation of LPRE turbo-pump turbines using double-sided and single-sided labyrinth seals used in Energomash's engines. The key geometrical parameters of each seal variant, images of 3D-models of seals constructed for the calculations, the resulting computational grid for each seal variant, as well as graphs of the pressure distribution and velocity fields are presented for visual comparison. Sectoral leakage was calculated for each variant of the seal, the possibility of reducing the temperature of the turbine inlet working gas was assessed. In the future attention should be paid to a more detailed study of this type of seals with the use of modern computing powe

Constraints on Heavy Decaying Dark Matter from 570 Days of LHAASO Observations

: The kilometer square array (KM2A) of the large high altitude air shower observatory (LHAASO) aims at surveying the northern γ-ray sky at energies above 10 TeV with unprecedented sensitivity. γ-ray observations have long been one of the most powerful tools for dark matter searches, as, e.g., high-energy γ rays could be produced by the decays of heavy dark matter particles. In this Letter, we present the first dark matter analysis with LHAASO-KM2A, using the first 340 days of data from 1/2-KM2A and 230 days of data from 3/4-KM2A. Several regions of interest are used to search for a signal and account for the residual cosmic-ray background after γ/hadron separation. We find no excess of dark matter signals, and thus place some of the strongest γ-ray constraints on the lifetime of heavy dark matter particles with mass between 10^{5} and 10^{9}  GeV. Our results with LHAASO are robust, and have important implications for dark matter interpretations of the diffuse astrophysical high-energy neutrino emission