Mace gamma rays telescope – India
Major Atmospheric Cherenkov Experiment Telescope (MACE) is India’s largest, world’s second largest and the world’s highest gamma-ray telescope. At Hanle observatory, four booms hold the camera at a focal distance of 25 m from the reflecting surfaces of the mirror facets clamped on the mirror basket. The novel feature of the telescope is the design of the integrated imaging camera, which contain 1088 photomultiplier-based pixels and all the signal processing and data acquisition electronics.
MACE is a 21m diameter telescope installed at Hanle in Ladakh at an altitude of 4500m above sea level. This is the highest for any IACT based telescope. IACT stands for Imaging Atmospheric (or Air) Cherenkov Telescope or Technique.
The largest telescope of the same class is the 28-metre-diameter telescope, which is part of the High Energy Stereoscopic System (HESS) in Namibia.
Only a few power cables and optical fiber-based data cables links the camera to the central control room, where a computer network is housed for telescope control, monitoring and archiving the data.
The azimuthal track of the telescope is about 27 m in diameter and the overall height of the telescope is about 43 m. The overall weight of the telescope works out to about 170 tonnes, including the mirror panels and their motion control systems, which weighs about 25 tonnes.
The MACE telescope is among a very few current generations state of the art ground-based gamma-ray instruments world-wide.
Gamma rays telescope at Hanle, Ladakh (Mace Telescope)
Placed at an high altitude in Hanle, the MACE telescope will help the researchers to explore the high energy gamma radiation in the Universe.
The high energy gamma radiation is produced along with the energetic cosmic rays at various astronomical sites. Therefore, origin and propagation of the gamma ray photons provide a unique experimental tool in the Astrophysics and Cosmology research.
The MACE telescope is expected to play a very important role to study the sources of cosmic gamma radiation like Active Galactic Nuclei (AGNs), Gamma Ray Bursts (GRBs), Pulsars, Binary Star Systems, Remnants of Supernova explosions (SNR), Giant Molecular Clouds (GMC), Star Burst Galaxies and other objects in our Milky-Way Galaxy through observations of gamma rays with energies above 20 GeV.
Additionally, MACE will also assist in the discovery of new gamma-ray sources and identification of unidentified sources in the high energy Fermi catalogue.
Beyond probing the non-thermal Universe and cosmic accelerators, MACE telescope is also expected to address a range of cosmological topics such as constraining the intensity of Extragalactic Background Light (EBL) and strength of Intergalactic Magnetic Field (IGMF), cosmic ray electron spectrum, search for Dark Matter (DM) particles and some fundamental physics problems like Lorentz Invariance Violation (LIV), anamoly in photon-photon pair production and photon-Axion Like Particle (ALP) oscillations.
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Salient features of gamma rays mace telescope at Leh, Ladakh
Energy range : 20 GeV – 10 TeV
Light collector : 21 m diameter (Quasi-paraboloid shape)
Mirror facets : 356 x 4 = 1424 (diamond turned aluminium)
Tracking accuracy : 1 arc-min
Imaging camera : 1088 photomultiplier tubes
Signal digitization : 1 GSPS using Domino Ring Sampler
Data volume : 40 GB / hr
Expected Sensitivity : 5 sigma detection of the Crab Nebula in few minutes of observation (above 30 GeV).
Click to read – how to reach Hanle? (travel to Hanle, Ladakh))
Travel to Hanle, Ladakh
Hanle is a dry cold area. It is always best to carry very heavy woolen clothes and jackets. The altitude of the place is around 4270 m above sea level. The altitude at the village can be a bit lower but Indian Astronomical Observatory in this area is at an altitude of 4,500 meters. One must stay at Leh for a few days to adjust to the height, different air pressure and climate before going to Hanle.
The higher photon density along with the low background light level at this site helps in lowering the energy threshold of the Cherenkov telescope.
One can study different types of astrophysical sources with the MACE telescope such as supernova remnants, pulsar wind nebula, active galactic nuclei, gamma-ray bursts, pulsars, star burst galaxies, gamma-ray binary and dark matter.
In India, the first Imaging Atmospheric Cherenkov Technique (IACT)/ telescope TACTIC (TeV Atmospheric Cherenkov Telescope with Imaging Camera) started operating in the year 1997 at Mount Abu, Rajasthan. Now a more sensitive telescope the MACE is installed at Hanle to study the gamma-ray sky in the energy range 20 GeV – 10 TeV.
Gamma ray telescopes around the world are –
MAGIC (set of two telescopes with a diameter of 17 meters each at the Canary Island of La Palma, 2.2 km asl)
VERITAS (an array of four telescopes with a diameter of 12 meters each in Arizona, 1.3 km asl)
HESS (system of four telescopes with a diameter of 12 meters each and a much bigger fifth telescope of 28 meter diameter in Namibia, 1.8 km asl) telescopes.
What are gamma rays?
Gamma rays are a form of electromagnetic radiation. These rays have the smallest wavelengths and the most energy of any wave in the electromagnetic spectrum. Gamma rays are produced primarily by four different nuclear reactions: fusion, fission, alpha decay and gamma decay.
Unlike optical light and x-rays, gamma rays cannot be captured and reflected by mirrors. Gamma-ray wavelengths are so short that they can pass through the space within the atoms of a detector.
Interestingly, gamma rays are a form of light, whereas alpha and beta particles are made of matter.
Because of their high energy, gamma rays are ionizing, meaning they can dislodge electrons from atoms, ultimately damaging living cells and causing a hazard to health.
Because Earth’s atmosphere blocks most gamma-rays, they’re seen only with high-altitude telescopes.
Gamma rays are sometimes used to treat cancerous tumors in the body by damaging the DNA of the tumor cells. However, great care must be taken, because gamma-rays can also damage the DNA of surrounding healthy tissue cells.
(Source: Astrophysical Sciences Division, Bhabha Atomic Research Centre)