64 research outputs found
Wavelength-shifting light traps for SWGO and other applications
No full textWavelength-shifting (WLS) materials contain molecules that absorb light and reemit at longer wavelengths. They can be used for light detection because they provide a large effective area for low cost and they are able to efficiently trap and guide light because of total internal reflection processes. We are currently developing such a WLS detector, considering two main designs: A single-shift design with one wavelength shift (tile) and a double-shift design with two wavelength shifts (tile and fiber). As photodetectors we use small Silicon photomultipliers (SiPMs) with a high photon detection efficiency (PDE) and single-photon sensitivity. The double-shift layout goes at the expense of detection efficiency. In this design however, light is channeled to the two ends of a fiber, thus requiring a reduced photosensitive area compared to the single-shift layout. We will present the results of our measurements and show that light traps and SiPMs together represent a promising alternative to PMTs in case of a non-focused light beam. For the special case of SWGO, the application of light traps is also motivated by a possible improvement of the gamma/hadron separation, using a one-chamber tank with an array of wavelength-shifting light traps instead of a (two-chamber) tank with PMTs. Besides SWGO, new WLS detectors could also constitute useful and cheap technology for other experiments and use cases. The contribution summarizes our motivation and efforts to build a light trap detection module and to characterize its properties in terms of costs, temporal performance and detection efficiency
Internal microdosimetry of inhaled radon progeny in bronchial airways: Advantages and limitations
No full textInternational audienceThe objective of the present study was to identify advantages and limitations of the application of microdosimetric concepts for inhaled radon progeny activities in the lungs. The methods employed for this analysis were a recently developed Monte-Carlo microdosimetry code for the calculation of energy deposition in bronchial target cells and the Probability Per Unit Track Length (PPUTL) model, which relates these microdosimetric parameters to cellular radiation effects. The major advantages of internal microdosimetry of radon progeny in bronchial airways are: (i) quantitative characterisation of non-uniform dose distributions and identification of target sites with enhanced carcinogenic potential, (ii) quantification of low doses of alpha particles by the number of cells hit and the dose received by those cells, (iii) illustration of the random variations of cellular doses by specific energy distributions and (iv) establishment of a direct link to cellular radiobiological effects. At present, a major limitation of microdosimetry is the extrapolation of the response of individual cells to the resulting tissue response, which is still not fully explored. © The Author 2007. Published by Oxford University Press. All rights reserved
Vieillissements et territoires: participation au-delà et à travers les frontières
No full textInternational audienc
Vieillissements et territoires: participation au-delà et à travers les frontières
No full textInternational audienc
Vieillissements et territoires: participation au-delà et à travers les frontières
No full textInternational audienc
Vieillissements et territoires: participation au-delà et à travers les frontières
No full textInternational audienc
VHE γ-ray observations of bright BL Lacs with the Large-Sized Telescope prototype (LST-1) of the CTAO
No full textCherenkov Telescope Array Observatory (CTAO) is the next-generation ground-based γ-ray observatory operating in the energy range from 20GeV up to 300TeV, with two sites in La Palma (Spain) and Paranal (Chile). It will consist of telescopes of three sizes, covering different parts of the large energy range. We report on the performance of Large-Sized Telescope prototype (LST-1) in the detection and characterization of extragalactic γ-ray sources, with a focus on the reconstructed γ-ray spectra and variability of classical bright BL Lacertae objects, which were observed during the early commissioning phase of the instrument. LST-1 data from known bright γ-ray blazars ─ Markarian 421, Markarian 501, 1ES 1959+650, 1ES 0647+250, and PG 1553 + 113 ─ were collected between 2020 July 10, and 2022 May 23, covering a zenith angle range of 4∘ to 57∘. The reconstructed light curves were analysed using a Bayesian block algorithm to distinguish the different activity phases of each blazar. Simultaneous Fermi-LAT data were utilized to reconstruct the broad-band γ-ray spectra for the sources during each activity phase. High-level reconstructed data in a format compatible with gammapy are provided together with measured light curves and spectral energy distributions (SEDs) for several bright blazars and an interpretation of the observed variability in long and short time-scales. Simulations of historical flares are generated to evaluate the sensitivity of LST-1. This work represents the first milestone in monitoring bright BL Lacertae objects with a CTAO telescope
Nuits de l'armée n °2 / Présentation : Jean de Faucon
No full textTitre uniforme : [Marche de la légion étrangère]Titre uniforme : [Michel Strogoff]Titre uniforme : [Chant des Partisans]Comprend : LIBERATION / Musique et Nouba du 13e R.T.A. - Joyeux marsouins - Prélude et menuet de la suite ancienne - Hymne de l'infanterie de marine / La musique Principale de Troupes Coloniales - Bande du roi - Médaille parade - Chinon / la Fanfare de Cavalerie de la Garde Républicaine de Paris - Auprès de ma blonde / la Fanfare de l'Ecole Enfantine HERIOT - Marche de la légion étrangère / La musique de la Légion Etrangère - MICHEL STROGOFF / Fanfare de la Garde Rouge - Y' A BON / la Musique des Tirailleurs Sénégalais - Chants des partisans / La Musique et Grand orchestre de la Garde Républicaine - La marseillaise / les 2.000 Musiciens des NUITS DE L'ARMEE, dir. F.J. BRUNBnF-Partenariats, Collection sonore - BelieveContient une table des matière
Author Correction: Proton acceleration in thermonuclear nova explosions revealed by gamma rays (Nature Astronomy, (2022), 6, 6, (689-697), 10.1038/s41550-022-01640-z)
No full textIn the version of this article initially published, there was an error in the scale described in the right-hand y-axis label of Fig. 1. Flux density (Jy), now presented on a scale from “1, 10, 102”, was originally shown as “10, 102”. The image has been corrected in the HTML and PDF versions of the article. Further, the Source Data for Fig. 1 have now been replaced online
Author Correction: Proton acceleration in thermonuclear nova explosions revealed by gamma rays (Nature Astronomy, (2022), 6, 6, (689-697), 10.1038/s41550-022-01640-z)
No full textIn the version of this article initially published, there was an error in the scale described in the right-hand y-axis label of Fig. 1. Flux density (Jy), now presented on a scale from “1, 10, 102”, was originally shown as “10, 102”. The image has been corrected in the HTML and PDF versions of the article. Further, the Source Data for Fig. 1 have now been replaced online
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