32 research outputs found
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
Reactivity of (E)-4-aryl-4-oxo-2-butenoic acid phenylamides with piperidine and benzylamine: kinetic and theoretical study
Rates of the aza-Michael addition of piperidine and benzylamine to thirteen (E)-4-aryl-4-oxo-2-butenoic acid phenylamides (AACPs) are reported. Progress of the reaction was monitored by UV/Vis spectroscopy. The 2D NMR spectra confirmed regioselectivity of the reactions. Piperidine and benzylamine provide exclusively beta-adducts in respect to the aroyl keto group. Influence of the substituents of the aroyl phenyl ring of AACPs on the rate of the reaction was quantified by Hammett substituent constants, partial atomic charges, and the energies of frontier orbitals. Good correlations between second-order rate constants and the Hammett substituent constants were obtained (r = 0.98, piperidine; r = 0.94, benzylamine) for para-, and meta-, para-substituted derivatives. Best correlations were obtained with the energies of the lowest unoccupied molecular orbitals of compounds, derived from the MP2 level of theory. Calculated UV/Vis spectra of representative AACPs and their Michael adduct with piperidine and benzylamine are in fair agreement with experimentally obtained data