Detection properties and internal activity of newly developed La-containing scintillator crystals

International audienceIn this work, we will present the characterization, in terms of gamma response and internal activity of newly developed crystals that contains Lanthanum in their chemical formula. In particular we tested two LaBr 3 :Ce,Sr, one CLLBC and two CLLB crystals with different volumes. These crystals just overcome the prototype stage and, even if the production in still not standardized at least for large optics, they have been very recently commercialized in sizes interesting for high-energy gamma-ray spectroscopy, as for application in nuclear physics experiments. In particular, we will report on the study of the decay time, light yield and energy resolution with gamma rays, on the response as a function of the gamma interaction point and on the internal activity due to the presence of Lanthanum

A single photoelectron calibration system for the NectarCAM camera of the Cherenkov Telescope Array Medium-Sized Telescopes

International audienceThis contribution aims to introduce the single photo-electron system designed to calibrate the camera of the Medium-Sized Telescopes of the Cherenkov Telescope Array (CTA). This system will allow us to measure accurately the gain of the camera’s photodetection chain and to constrain the systematic uncertainties on the energy reconstruction of gamma rays detected by CTA. The system consists of a white painted screen, a fishtail light guide, a flasher and an XY motorization to allow movement. The flashes guided by the fishtail mimic the Cherenkov radiation and illuminate the focal plane under the screen homogeneously. Then, through the XY motorisation, the screen is moved across the entire focal plane of the NectarCAM camera, which consists of 1855 photo-multiplier tubes. In this contribution, we present the calibration system and the study on its optimum scan positions required to cover the full camera effectively. Finally, we illustrate the results of the calibration data analysis and discuss the performance of the system

Study of light yield for different configurations of plastic scintillators and wavelength shifting fibers

International audienceIn the effort of the AugerPrime scintillator surface detector R&D; activity, we investigated the performances of different extruded and cast plastic scintillators that were read out with wavelength-shifting (WLS) optical fibers and then coupled to a PMT. In particular we compared the light yield of eighteen scintillator/fiber configurations, obtained combining eight different scintillator bars with six fiber types, in order to investigate which was satisfying the AugerPrime specifications in terms of light production ( >12 photoelectrons per minimum ionizing particle). In this paper, we present the results of the study on different scintillator bar geometries, scintillator production techniques, and wavelength-shifting optical fiber types. We also propose an effective way to optically couple the fibers to the PMT entrance window

Design and characterization of a single photoelectron calibration system for the NectarCAM camera of the medium-sized telescopes of the Cherenkov Telescope Array

International audienceIn this work, we describe the optical properties of the single photoelectron (SPE) calibration system designed for NectarCAM, a camera proposed for the Medium Sized Telescopes (MST) of the Cherenkov Telescope Array (CTA). One of the goals of the SPE system, as integral part of the NectarCAM camera, consists in measuring with high accuracy the gain of its photo-detection chain. The SPE system is based on a white painted screen where light pulses are injected through a fishtail light guide from a dedicated flasher. The screen – placed 15 mm away from the focal plane – is mounted on an XY motorization that allows movements over all the camera plane. This allows in-situ measurements of the SPE spectra via a complete scan of the 1855 photo-multiplier tubes (PMTs) of NectarCAM. This calibration process will enable the reduction of the systematic uncertainties on the energy reconstruction of γ -rays coming from distant astronomical sources and detected by CTA.We discuss the design of the screen used in the calibration system and we present its optical performances in terms of light homogeneity and timing of the signal