Design of light concentrators for Cherenkov telescope observatories

The Cherenkov Telescope Array (CTA) will be the largest cosmic gamma ray detector ever built in the world. It will be installed at two different sites in the North and South hemispheres and should be operational for about 30 years. In order to cover the desired energy range, the CTA is composed of typically 50-100 collecting telescopes of various sizes (from 6 to 24-m diameters). Most of them are equipped with a focal plane camera consisting of 1500 to 2000 Photomultipliers (PM) equipped with light concentrating optics, whose double function is to maximize the amount of Cherenkov light detected by the photo-sensors, and to block any stray light originating from the terrestrial environment. Two different optical solutions have been designed, respectively based on a Compound Parabolic Concentrator (CPC), and on a purely dioptric concentrating lens. In this communication are described the technical specifications, optical designs and performance of the different solutions envisioned for all these light concentrators. The current status of their prototyping activities is also given

A major electronics upgrade for the H.E.S.S. Cherenkov telescopes 1-4

The High Energy Stereoscopic System (H.E.S.S.) is an array of imaging atmospheric Cherenkov telescopes (IACTs) located in the Khomas Highland in Namibia. It consists of four 12-m telescopes (CT1-4), which started operations in 2003, and a 28-m diameter one (CT5), which was brought online in 2012. It is the only IACT system featuring telescopes of different sizes, which provides sensitivity for gamma rays across a very wide energy range, from ~30 GeV up to ~100 TeV. Since the camera electronics of CT1-4 are much older than the one of CT5, an upgrade is being carried out; first deployment was in 2015, full operation is planned for 2016. The goals of this upgrade are threefold: reducing the dead time of the cameras, improving the overall performance of the array and reducing the system failure rate related to aging. Upon completion, the upgrade will assure the continuous operation of H.E.S.S. at its full sensitivity until and possibly beyond the advent of CTA. In the design of the new components, several CTA concepts and technologies were used and are thus being evaluated in the field: The upgraded read-out electronics is based on the NECTAR readout chips; the new camera front- and back-end control subsystems are based on an FPGA and an embedded ARM computer; the communication between subsystems is based on standard Ethernet technologies. These hardware solutions offer good performance, robustness and flexibility. The design of the new cameras is reported here.Comment: Proceedings of the 34th International Cosmic Ray Conference, 30 July- 6 August, 2015, The Hague, The Netherland

The camera of the fifth H.E.S.S. telescope. Part I: System description

In July 2012, as the four ground-based gamma-ray telescopes of the H.E.S.S. (High Energy Stereoscopic System) array reached their tenth year of operation in Khomas Highlands, Namibia, a fifth telescope took its first data as part of the system. This new Cherenkov detector, comprising a 614.5 m^2 reflector with a highly pixelized camera in its focal plane, improves the sensitivity of the current array by a factor two and extends its energy domain down to a few tens of GeV. The present part I of the paper gives a detailed description of the fifth H.E.S.S. telescope's camera, presenting the details of both the hardware and the software, emphasizing the main improvements as compared to previous H.E.S.S. camera technology.Comment: 16 pages, 13 figures, accepted for publication in NIM

Design concepts for the Cherenkov Telescope Array CTA: an advanced facility for ground-based high-energy gamma-ray astronomy

Ground-based gamma-ray astronomy has had a major breakthrough with the impressive results obtained using systems of imaging atmospheric Cherenkov telescopes. Ground-based gamma-ray astronomy has a huge potential in astrophysics, particle physics and cosmology. CTA is an international initiative to build the next generation instrument, with a factor of 5-10 improvement in sensitivity in the 100 GeV-10 TeV range and the extension to energies well below 100 GeV and above 100 TeV. CTA will consist of two arrays (one in the north, one in the south) for full sky coverage and will be operated as open observatory. The design of CTA is based on currently available technology. This document reports on the status and presents the major design concepts of CTA

Southern African Large Telescope Spectroscopy of BL Lacs for the CTA project

In the last two decades, very-high-energy gamma-ray astronomy has reached maturity: over 200 sources have been detected, both Galactic and extragalactic, by ground-based experiments. At present, Active Galactic Nuclei (AGN) make up about 40% of the more than 200 sources detected at very high energies with ground-based telescopes, the majority of which are blazars, i.e. their jets are closely aligned with the line of sight to Earth and three quarters of which are classified as high-frequency peaked BL Lac objects. One challenge to studies of the cosmological evolution of BL Lacs is the difficulty of obtaining redshifts from their nearly featureless, continuum-dominated spectra. It is expected that a significant fraction of the AGN to be detected with the future Cherenkov Telescope Array (CTA) observatory will have no spectroscopic redshifts, compromising the reliability of BL Lac population studies, particularly of their cosmic evolution. We started an effort in 2019 to measure the redshifts of a large fraction of the AGN that are likely to be detected with CTA, using the Southern African Large Telescope (SALT). In this contribution, we present two results from an on-going SALT program focused on the determination of BL Lac object redshifts that will be relevant for the CTA observatory

WSAVA Therapeutic Guidelines

This list of essential medicines is presented by members of the WSAVA Therapeutic Guidelines Group (TGG) following extensive internal and external peer‐review. Internal peer‐review was provided by TGG members and its subcommittees, whereas external peer‐review was performed by board‐certified individuals and other WSAVA working/guideline groups. The first draft of this document was presented at the WSAVA annual meeting in Toronto (2019) followed by a three‐month audit during which WSAVA member affiliates were asked to provide comments, suggestions and overall feedback. These were then carefully considered by the TGG. The final list is a product of several rounds of revision and based on expert consensus. This list of essential medicines should allow veterinarians to provide proper preventive care and treatment of the most frequent and important diseases in dogs and cats while maintaining appropriate animal welfare standards. The purpose of the list is to improve and facilitate regulatory oversight for ensuring appropriate medicines availability, drug quality, use and pharmacovigilance, while mitigating the growing black/counterfeit market of pharmaceutical products. The list of essential medicines is not intended to define what medicines should be always available within the clinic/hospital; rather that veterinarians should have ready access to these (medicines) if required for the prevention and treatment of specific diseases and conditions. Additionally, the committee understands that there is no “one‐size fits all” and that there may be specific medicines used for endemic/epidemic diseases in some countries that the list does not cover. For example, the essential antimicrobials were defined as those medicines that are recommended as first line agents for treatment of at least one common disease condition

Development of an ultra thin beam profiler for charged particle beams

International audienceBeam profiling during patient treatment in protontherapy requires ultra-thin monitors to preserve the high beam quality. For detectors upstream in the line, a material budget as low as ∼ 15 μ m water-equivalent is needed. In addition, the current trend of dose escalation to treat highly resistant tumors implies challenging requirements on monitor radiation hardness and dynamic range. We propose a new type of beam profiler, PEPITES, using secondary electron emission (SEE) and built with thin-film techniques. The beam is profiled by crossing a pattern or a series of patterns which emit the SEE signal and can be made ultra-thin as SEE originates from the few nanometers next to the surface. The patterns are deposited on membranes, which, in contrast with common systems like ionization chambers, are free from mechanical constraints and can then afford higher absorbed doses and be as thin as achievable. A simple demonstrator prototype has been built and successfully operated with a proton beam at the ARRONAX cyclotron at St Herblain in a wide range of currents (100 fA to 10 nA) and several energies (30 - 68 MeV). Beam profiling results from these tests are presented, and our plans for the next prototypes are mentioned

68 A new transparent beam profiler based on secondary electrons emission for hadrontherapy charged particles beams

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