On the sensitivity of the HAWC observatory to gamma-ray bursts

We present the sensitivity of HAWC to Gamma Ray Bursts (GRBs). HAWC is a very high-energy gamma-ray observatory currently under construction in Mexico at an altitude of 4100 m. It will observe atmospheric air showers via the water Cherenkov method. HAWC will consist of 300 large water tanks instrumented with 4 photomultipliers each. HAWC has two data acquisition (DAQ) systems. The main DAQ system reads out coincident signals in the tanks and reconstructs the direction and energy of individual atmospheric showers. The scaler DAQ counts the hits in each photomultiplier tube (PMT) in the detector and searches for a statistical excess over the noise of all PMTs. We show that HAWC has a realistic opportunity to observe the high-energy power law components of GRBs that extend at least up to 30 GeV, as it has been observed by Fermi LAT. The two DAQ systems have an energy threshold that is low enough to observe events similar to GRB 090510 and GRB 090902b with the characteristics observed by Fermi LAT. HAWC will provide information about the high-energy spectra of GRBs which in turn could help to understanding about e-pair attenuation in GRB jets, extragalactic background light absorption, as well as establishing the highest energy to which GRBs accelerate particles

Silver Nanoparticles Dispersed on Silica Glass for Applications as Photothermal Selective Material

AbstractSilver nanoparticles dispersed into a resin are deposited on silica glasses by the spin coating method and heated around 100°C. UV-VIS measurements show high stability of the optical spectra after heat treatment, suggesting that the morphology of the silver nanoparticles are stable. The transmission electronic microscopy images exhibit huge spherical aggregates and prolate silver nanoparticles. In order to evaluate the roughness and solar optical properties, reflectance spectra, atomic force microscopy and perfilometric measurements are performed. The chemical composition and morphology of the films are analyzed by energy-dispersive X-ray spectroscopy, EDX. The optical properties of the films show high absortance and low emissivity in the visible and near infrared range, respectively, suggesting their potential use as photothermal selective materials with good thermal stabilization. This feature is an important prerequisite of coatings for the solar collector manufacturing. The optical properties, the thin film thickness and roughness are correlated among them to understand the selective response of the coatings