The Indian Neutrino Observatory is set to be built within this mountain in the Body West Hills Reserved Forest (Image: M. V. N. Murthy)

A major neutrino observatory set to be built in India cleared a major hurdle this week, when the Ministry of Environment and Forests formally approved the project.

The $250 million underground laboratory, called the Indian Neutrino Observatory (INO), will be built in the Bodi West Hills Reserved Forest in the state of Tamil Nadu.

The hills there rise very steeply, so workers will have to tunnel only about 2 kilometres horizontally to provide the laboratory with about 1300 metres of high-quality granite cover above. The rock cover is needed to shield the neutrino detector from particles called muons that form when cosmic rays hit the atmosphere.


INO will be made of 50,000 tonnes of magnetised iron, dwarfing the 12,500-tonne magnet in the Compact Muon Solenoid detector at CERN in Geneva, Switzerland. “It’ll be the most massive magnet [ever built],” says team member M. V. N. Murthy of the Institute of Mathematical Sciences in Chennai, Tamil Nadu.

Anti-neutrinos too

Neutrinos will interact with the iron – which will be layered in sheets – and spew out charged particles, whose paths will be bent by the iron’s magnetic field. About 30,000 detectors sandwiched between the sheets of iron will track these charged particles, providing information about the incident neutrinos.

INO will initially study atmospheric neutrinos, which are produced when cosmic rays smash into the upper atmosphere.

Unlike most neutrino detectors, such as the Super-Kamiokande in Japan or the Sudbury Neutrino Observatory in Canada, INO will be sensitive to both neutrinos and anti-neutrinos, which interact with matter in different ways.

Neutrinos and their antimatter counterparts oscillate between three types: electron, tau and muon. INO should help physicists understand which of the three types is the lightest and which is the heaviest.

Elephants and tigers

INO scientists hope the observatory will also be used to detect neutrinos beamed from specialised neutrino factories that might be built at CERN or Fermilab near Chicago, Illinois. “We are uniquely situated to look at those neutrinos,” says Murthy.

Because the source of neutrinos from those sites would be highly controlled, physicists could study how neutrinos oscillate from one type to another as they pass through the Earth to INO.

This was not the first time the INO team has tried to get environmental clearance for its laboratory. Previously, project leaders had selected a site in the Nilgiri Mountains in Tamil Nadu. The site already boasted an underground power station with 13 kilometres of tunnels, but the access road to reach it crossed an elephant corridor.

Even as physicists worked out how to minimise disruptions to wandering elephants, a wildflife sanctuary nearby was declared a tiger reserve in 2008. The observatory would have been perilously close to the reserve’s 5-kilometre-wide buffer zone, so the project was denied clearance at that site.