MAGIC (telescope)
Template:Short description Template:About Template:Infobox Telescope MAGIC (Major Atmospheric Gamma Imaging Cherenkov Telescopes, later renamed to MAGIC Florian Goebel Telescopes) is a system of two Imaging Atmospheric Cherenkov telescopes situated at the Roque de los Muchachos Observatory on La Palma, one of the Canary Islands, at about Template:Convert above sea level. MAGIC detects particle showers released by gamma rays, using the Cherenkov radiation, i.e., faint light radiated by the charged particles in the showers. With a diameter of Template:Convert for the reflecting surface, it was the largest in the world before the construction of H.E.S.S. II.
The first telescope was built in 2004 and operated for five years in standalone mode. A second MAGIC telescope (MAGIC-II), at a distance of Template:Convert from the first one, started taking data in July 2009. Together they integrate the MAGIC telescope stereoscopic system.<ref>Template:Cite conference</ref>
MAGIC is sensitive to cosmic gamma rays with photon energies between Template:Val (later lowered to Template:Val) and Template:Val due to its large mirror; other ground-based gamma-ray telescopes typically observe gamma energies above Template:Val. Gamma-ray astronomy also utilizes satellite-based detectors, which can detect gamma-rays in the energy range from keV up to several GeV.Template:Cn
Aims
The goals of the telescope are to detect and study primarily photons coming from:
- Accretion of black holes in active galactic nuclei
- Supernova remnants, due to their interest as sources of cosmic rays.
- Other galactic sources such as pulsar wind nebulae or X-ray binaries.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref>
- Unidentified EGRET or Fermi sources
- Gamma ray bursts
- Annihilation of dark matter
Observations
MAGIC has found pulsed gamma-rays at energies higher than Template:Val coming from the Crab Pulsar. The presence of such high energies indicates that the gamma-ray source is far out in the pulsar's magnetosphere, in contradiction with many models.<ref>Template:Cite journal</ref>
In 2006 MAGIC detected very high energy cosmic rays from the quasar 3C 279, which is 5 billion light years from Earth. This doubles the previous record distance from which very high energy cosmic rays have been detected. The signal indicated that the universe is more transparent than previously thought based on data from optical and infrared telescopes.<ref>Template:Cite journal</ref>
MAGIC did not observe cosmic rays resulting from dark matter decays in the dwarf galaxy Draco.<ref>Template:Cite journal</ref> This strengthens the known constraints on dark matter models.
A much more controversial observation is an energy dependence in the speed of light of cosmic rays coming from a short burst of the blazar Markarian 501 on July 9, 2005. Photons with energies between Template:Val arrived 4 minutes after those in a band between Template:Val. The average delay was Template:Val of energy of the photon. If the relation between the space velocity of a photon and its energy is linear, then this translates into the fractional difference in the speed of light being equal to minus the photon's energy divided by Template:Val. The researchers have suggested that the delay could be explained by the presence of quantum foam, the irregular structure of which might slow down photons by minuscule amounts only detectable at cosmic distances such as in the case of the blazar.<ref>Template:Cite journal</ref><ref>Template:Cite web</ref>
Technical specifications
Each telescope has the following specifications:
- A collecting area Template:Convert consisting of 956 Template:Convert aluminium individual reflectors
- A lightweight carbon fibre frame
- A detector consisting of 396 separate hexagonal photomultiplier detectors in the center (diameter: Template:Convert) surrounded by 180 larger photomultiplier detectors (diameter: Template:Convert).
- Data are transferred in analogue form by fibre optic cables
- Signal digitization is done via an ADC (analog-to-digital converter) with a Template:Val sampling rate
- Total weight of Template:Convert
- Reaction time to move to any position of the sky less than 22 seconds<ref name="Cortina_2004">Template:Cite journal</ref>
Each mirror of the reflector is a sandwich of an aluminum honeycomb, Template:Convert plate of AlMgSi alloy, covered with a thin layer of quartz to protect the mirror surface from aging. The mirrors have spherical shape with a curvature corresponding to the position of the plate in the paraboloid reflector. The reflectivity of the mirrors is around 90%. The focal spot has a size of roughly half a pixel size (<0.05°).
Directing the telescope to different elevation angles causes the reflector to deviate from its ideal shape due to the gravity. To counteract this deformation, the telescope is equipped with an Active Mirror Control system. Four mirrors are mounted on each panel, which is equipped with actuators that can adjust its orientation in the frame.
The signal from the detector is transmitted over Template:Convert of optical fibers. The signal is digitized and stored in a Template:Val ring buffer. The readout of the ring buffer results in a dead time of Template:Val, which corresponds to about 2% dead time at the design trigger rate of Template:Val. The readout is controlled by an FPGA (Xilinx) chip on a PCI (MicroEnable) card. The data is saved to a RAID0 disk systemTemplate:Why? at a rate up to Template:Val, which results in up to Template:Val raw data per night.<ref name="Cortina_2004"/>
Collaborating institutions
Physicists from over twenty institutions in Germany, Spain, Italy, Switzerland, Croatia, Finland, Poland, India, Bulgaria and Armenia collaborate in using MAGIC; the largest groups are at
- Institut de Física d'Altes Energies (IFAE), Spain
- Universitat Autònoma de Barcelona, Spain
- Universidad Complutense de Madrid, Spain
- Centro de Investigaciones Energéticas, MedioAmbientales y Tecnológicas (CIEMAT), Spain
- Instituto de Astrofísica de Andalucía, Spain
- Instituto de Astrofísica de Canarias, Spain
- ETHZ, Zürich, Switzerland
- UNIGE, Geneva, Switzerland
- Dipartimento di Fisica and INFN, University of Padua, Italy
- Tuorla Observatory, Piikkiö, Finland
- Dipartimento di Fisica and INFN, University of Siena, Italy
- Dipartimento di Fisica and INFN, University of Udine, Italy
- TU Dortmund University, Germany
- University of Würzburg, Germany
- Max Planck Institute for Physics, Germany
- Institute for Particle Physics, Zürich, Switzerland
- National Institute for Astrophysics (INAF), Italy
- Institute for Nuclear Research and Nuclear Energy, Sofia, Bulgaria
- Croatian MAGIC Consortium (Institute Ruđer Bošković, Zagreb; University of Split, Split; University of Rijeka, Rijeka), Croatia
See also
References
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