The Indian government has given the go-ahead for a huge underground observatory that researchers hope will provide crucial insights into neutrino physics. Construction will now begin on the Rs15bn ($236m) Indian Neutrino Observatory (INO) at Pottipuram, which lies 110 km from the temple city of Madurai in the southern Indian state of Tamil Nadu. Madurai will also host a new Inter Institutional Centre for High Energy Physics that will be used to train scientists and carry out R&D for the new lab.

Originally planned to be complete by 2012, the INO has been in limbo for a number of years. In 2010 ecologists and conservationists raised objections to the INO’s initial proposed site at Singara in Tamil Nadu, which was near an elephant corridor and a tiger reserve. Researchers then had to find a new location, with the environment ministry only approving the Pottipuram site in 2011. Funding from the government arrived three years later.

The INO will be built some 1.3 km underground, accessible via a 2 km-long tunnel. The lab will comprise three caverns, the largest being 132 m long, 26 m wide and 30 m high, which will house a 50,000 tonne Iron Calorimeter (ICAL) neutrino detector. The detector will consist of alternate layers of some 30,000 ”resistive plate chambers” and iron plates.

The outcome of this investment will be extraordinary and long term

Krishnaswamy Vijayraghavan, secretary of the Department of Science and Technology

The INO team hopes to use the detector to address the “neutrino-mass hierarchy”. Scientists know that there are three neutrino-mass states, but do not yet know which is the most massive and which is the lightest. “Understanding this will help scientists to pick the correct theory beyond the Standard Model and, along with other accelerator-based experiments worldwide, address the problem of matter–antimatter asymmetry in the universe,” says INO project director Naba Mondal, who is based at the Tata Institute of Fundamental Research in Mumbai (TIFR).

As well as housing other experiments such as those searching for dark matter and neutrino-less double-beta decay, scientists are also hopeful that the INO will provide opportunities for young students to work on all aspects of particle-physics research, such as detector development and data analysis. “Science students across the country will have the opportunity to participate in building sophisticated particle detectors and electronic data-acquisition systems from scratch,” says Mondal.

Indeed, Krishnaswamy Vijayraghavan, secretary of the Department of Science and Technology, which oversees funding for many science projects, says that the INO could “allow India to train experimental physicists and high-end engineers on a large scale” in “extremely important and competitive high-energy physics”. “INO will be the agent of transforming physics of this kind in India and will make a global impact,” he adds. “The outcome of this investment will be extraordinary and long term.”

Taking centre stage

Researchers also hope that the INO could help India to reclaim its leading position in neutrino physics and in constructing underground labs. The country led the way in the 1960s when physicists used a gold mine at Kolar in the southern state of Karnataka to create what was then the world’s deepest underground lab. Known as the Kolar Gold Field Lab, in 1965 it enabled researchers to detect neutrinos that are created when cosmic rays smash into the atmosphere. The lab later studied proton decay and was only shut down in 1992 when gold mining at the site became uneconomical.

“With the closure of the mines, we lost a unique facility for carrying out research in the field of non-accelerator-based particle physics,” rues Mondal. “With the approval of the INO facility, we are now back on the centre stage of particle-physics research.”