Most major scientific results produced by ground-based gamma-ray telescopes in the last 30 years have been obtained by expert members of the collaborations operating these instruments. This is due to ...the proprietary data and software policies adopted by these collaborations. However, the advent of the next generation of telescopes and their operation as observatories open to the astronomical community, along with a generally increasing demand for open science, confront gamma-ray astronomers with the challenge of sharing their data and analysis tools. As a consequence, in the last few years, the development of open-source science tools has progressed in parallel with the endeavour to define a standardised data format for astronomical gamma-ray data. The latter constitutes the main topic of this review. Common data specifications provide equally important benefits to the current and future generation of gamma-ray instruments: they allow the data from different instruments, including legacy data from decommissioned telescopes, to be easily combined and analysed within the same software framework. In addition, standardised data accessible to the public, and analysable with open-source software, grant fully-reproducible results. In this article, we provide an overview of the evolution of the data format for gamma-ray astronomical data, focusing on its progression from private and diverse specifications to prototypical open and standardised ones. The latter have already been successfully employed in a number of publications paving the way to the analysis of data from the next generation of gamma-ray instruments, and to an open and reproducible way of conducting gamma-ray astronomy.
This volume celebrates the 30th anniversary of the first very-high energy (VHE) gamma-ray Source detection: the Crab Nebula, observed by the pioneering ground-based Cherenkov telescope Whipple, at ...teraelectronvolts (TeV) energies, in 1989. As we entered a new era in TeV astronomy, with the imminent start of operations of the Cherenkov Telescope Array (CTA) and new facilities such as LHAASO and the proposed Southern Wide-Field Gamma-ray Observatory (SWGO), we conceived of this volume as a broad reflection on how far we have evolved in the astrophysics topics that dominated the field of TeV astronomy for much of recent history.In the past two decades, H.E.S.S., MAGIC and VERITAS pushed the field of TeV astronomy, consolidating the field of TeV astrophysics, from few to hundreds of TeV emitters. Today, this is a mature field, covering almost every topic of modern astrophysics. TeV astrophysics is also at the center of the multi-messenger astrophysics revolution, as the extreme photon energies involved provide an effective probe in cosmic-ray acceleration, propagation and interaction, in dark matter and exotic physics searches. The improvement that CTA will carry forward and the fact that CTA will operate as the first open observatory in the field, mean that gamma-ray astronomy is about to enter a new precision and productive era.This book aims to serve as an introduction to the field and its state of the art, presenting a series of authoritative reviews on a broad range of topics in which TeV astronomy provided essential contributions, and where some of the most relevant questions for future research lie.
► The Richardson–Lucy-Algorithm was applied to very high-energy gamma-ray images. ► Systematic studies of the RLA with respect to source characteristics were performed. ► Deconvolution allows to ...study structural details below instrumental angular resolution. ► Deconvolution is applicable on 2 of the known 5 VHE shell-type SNRs.
The Richardson–Lucy deconvolution algorithm was applied to astronomical images in the very high-energy regime with photon energies above 100GeV. Through a systematic study with respect to source significance, background level and source morphology we were able to derive optimal deconvolution parameters. The results presented show that deconvolution makes it possible to study structural details well below the angular resolution of the very high-energy γ-ray experiment.
The discovery of the Crab Nebula as the first source of TeV gamma rays in 1989, using the technique of ground-based imaging air Cherenkov telescope, has marked the birthday of observational gamma ...astronomy in very high energy range. The team led by Trevor Weekes, after twenty years of trial and error, success and misfortune, step-by-step improvements in both the technique and understanding of gamma shower discrimination methods, used the 10m diameter telescope on Mount Hopkins in Arizona, and succeeded measuring a 9σ signal from the direction of Crab Nebula. As of today over 160 sources of gamma rays of very different types, of both galactic and extra-galactic origin, have been discovered due to this technique. This is a really fast evolving branch in science, rapidly improving our understanding of the most violent and energetic sources and processes in the sky.
The study of these sources provides clues to many basic questions in astrophysics, astro-particle physics, physics of cosmic rays and cosmology. Today’s telescopes, despite the young age of the technique, offer a solid performance. The technique is still maturing, leading to the next generation large instrument. This article is devoted to outlining the milestones in a long history that step-by-step have made this technique emerge and have brought about today’s successful source hunting.
Optimizing read-out of the NECTAr front-end electronics Vorobiov, S.; Feinstein, F.; Bolmont, J. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2012, Volume:
695
Journal Article
Peer reviewed
We describe the optimization of the read-out specifications of the NECTAr front-end electronics for the Cherenkov Telescope Array (CTA). The NECTAr project aims at building and testing a demonstrator ...module of a new front-end electronics design, which takes an advantage of the know-how acquired while building the cameras of the CAT, H.E.S.S.-I and H.E.S.S.-II experiments.
The goal of the optimization work is to define the specifications of the digitizing electronics of a CTA camera, in particular integration time window, sampling rate, analog bandwidth using physics simulations. We employed for this work real photomultiplier pulses, sampled at 100ps with a 600MHz bandwidth oscilloscope.
The individual pulses are drawn randomly at the times at which the photo-electrons, originating from atmospheric showers, arrive at the focal planes of imaging atmospheric Cherenkov telescopes. The timing information is extracted from the existing CTA simulations on the GRID and organized in a local database, together with all the relevant physical parameters (energy, primary particle type, zenith angle, distance from the shower axis, pixel offset from the optical axis, night-sky background level, etc.), and detector configurations (telescope types, camera/mirror configurations, etc.).
While investigating the parameter space, an optimal pixel charge integration time window, which minimizes relative error in the measured charge, has been determined. This will allow to gain in sensitivity and to lower the energy threshold of CTA telescopes. We present results of our optimizations and first measurements obtained using the NECTAr demonstrator module.
Between early 1997 and late 2002, the HEGRA collaboration operated a stereoscopic system of four (later five) imaging atmospheric Cherenkov telescopes. In this paper we present the calibration ...schemes which were developed for the system, and report on the performance of the detector over the years. In general, the telescope system was very well understood, regarding both the absolute calibration and the slight changes in performance over the years. The system had an energy threshold of 500 GeV for observations at zenith and under optimum detector conditions. With the corresponding calibration schemes, a systematic accuracy of 15% on the absolute energy scale has been achieved. The continuous sensitivity monitoring provided a relative accuracy of a few percent, and showed that the threshold did not exceed 600 GeV throughout the entire operation time. The readout electronics and the imaging quality of the dishes were well monitored and stable. The absolute pointing had an accuracy of at least 25
″; this number was guaranteed throughout the whole lifetime of the experiment.
The Cherenkov Telescope Array (CTA) is a project of a gamma-ray observatory in the Very High Energy (10
GeV–100
TeV) range. In this paper, the current status of the CTA design study is given. The ...motivations and expected performances are briefly described. The design options for several subsystems: telescopes, mirrors, front-end instrumentation and electronics are discussed.
NECTAr: New electronics for the Cherenkov Telescope Array Vorobiov, S.; Bolmont, J.; Corona, P. ...
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment,
05/2011, Volume:
639, Issue:
1
Journal Article, Conference Proceeding
Peer reviewed
The European astroparticle physics community aims to design and build the next generation array of Imaging Atmospheric Cherenkov Telescopes (IACTs), that will benefit from the experience of the ...existing H.E.S.S. and MAGIC detectors, and further expand the very-high energy astronomy domain. In order to gain an order of magnitude in sensitivity in the 10
GeV to
>
100
TeV
range, the Cherenkov Telescope Array (CTA) will employ 50–100 mirrors of various sizes equipped with 1000–4000 channels per camera, to be compared with the 6000 channels of the final H.E.S.S. array. A 3-year program, started in 2009, aims to build and test a demonstrator module of a generic CTA camera. We present here the NECTAr design of front-end electronics for the CTA, adapted to the trigger and data acquisition of a large IACTs array, with simple production and maintenance. Cost and camera performances are optimized by maximizing integration of the front-end electronics (amplifiers, fast analog samplers, ADCs) in an ASIC, achieving several GS/s and a few
μ
s
readout dead-time. We present preliminary results and extrapolated performances from Monte Carlo simulations.
Based on the Monte Carlo simulations we have studied the performance of the HEGRA system of imaging air Čerenkov telescopes (IACTs) in its present configuration of 4 IACTs as well as in its future ...final configuration of 5 IACTs. Here we present the results on the basic characteristics of the IACT system which are used in the standard data analysis procedure, i.e., the collection areas, the detection rates, the angular resolution, the energy resolution, and the γ/hadron-separation efficiency. By comparing several key Monte Carlo predictions with experimental results it is possible to check the accuracy of the simulations. The Monte Carlo results concerning hadron-nuclear showers are tested with the recorded cosmic ray events and the results concerning photon-induced showers are tested with a large data sample of γ-rays observed from BL Lac object Mkn 501 during its high flaring activity in 1997. Summarizing the simulations and current observations we give the basic recommendations of using the instrument and the major values of its sensitivity.
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