Neutrinos

What are neutrinos?

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Neutrinos are tiny, neutral, elementary particles which interact with matter via the weak force. The weakness of this force gives neutrinos the property that matter is almost trans- parent to them. The Sun, and all other stars, produce neutrinos copiously due to nuclear fusion and decay processes within their core. Since they rarely interact, these neutrinos pass through the Sun, and even the Earth, unhindered. There are many other natural sources of neutrinos including exploding stars (supernovae), relic neutrinos (from the birth of the uni- verse), natural radioactivity, and cosmic ray interactions in the atmosphere of the Earth. For example, the Sun produces over two hundred trillion trillion trillion neutrinos every second, and a supernova blast can unleash 1000 times more neutrinos than our Sun will produce in its 10-billion year lifetime. Billions of neutrinos stream through our body every second, yet only one or two of the higher energy neutrinos will interact with you in your lifetime.

The neutrino was proposed by Wolfgang Pauli in 1930; but it took another 26 years for it to be actually detected. In 1956 Reines and Cowan found evidence of neutrino interactions by monitoring a volume of cadmium chloride with scintillating liquid near to a nuclear reactor. Reines was jointly awarded the Nobel Prize in Physics in 1995 in part for this revolutionary work. We now know that not just one but at least three types or flavours of neutrinos and their anti-particles exist in nature. They have a tiny mass whose value is still not known. Moreover, they exhibit a quantum-mechanical phenomenon in which one type of neutrino oscillates into another as it propagates in space; this is called neutrino oscillation and this observation has generated immense excitement in the particle physics community

Why detect them ?

From recent experiments we know that the mass of the neutrino is non vanishing, but we are unsure how large the masses of the three individual neutrino types are because of the difficulty in detecting neutrinos. This is important because neutrinos are by far the most numerous of all the particles in the universe (other than photons of light) and so even a tiny mass for the neutrinos can enable them to have an effect on the evolution of the Universe through their gravitational effects. There are other recent astrophysical measurements that provide information on the evolution of the Universe and it is crucial to seek complementary information by direct determinations of the masses of neutrinos and their other properties. In a sense, neutrinos hold the key to several important and fundamental questions on the origin of the Universe and the energy production in stars. We have some partial answers but many details are still awaited from future experiments.

Yet another important possible application of neutrinos is in the area of neutrino tomography of the earth, that is detailed investigation of the structure of the Earth from core on wards. This is possible with neutrinos since they are the only particles which can probe the deep interiors of the Earth

Why should the laboratory be situated underground?

Neutrinos, as mentioned before, are notoriously difficult to detect in a laboratory because of their extremely weak interaction with matter. The background from cosmic rays (which interact much more readily than neutrinos) and natural radioactivity will make it almost

impossible to detect them on the surface of the Earth. This is the reason most neutrino observatories are located deep inside the Earth’s surface. The overburden provided by the Earth matter is transparent to neutrinos whereas most background from cosmic rays is substantially reduced depending on the depth at which the detector is located.

One of the earliest laboratories created to detect neutrinos underground in the world was located more than 2000 m deep at the Kolar Gold Field (KGF) mines in India. The first atmospheric neutrinos were detected at this laboratory in 1965. This laboratory has been closed due to the closure of the mines. Most underground laboratories around the world are located at a depth of a km or more. There are two types of underground laboratories: either located in a mine or in a road tunnel. There are now four major laboratories around the world: in Sudbury in Canada, Kamioka in Japan, under the Gran Sasso mountains in Italy and in Soudan mines in the USA. Several others are planned including INO which is an attempt to recapture the pioneering studies on neutrinos at KGF.

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What is INO?

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The India-based Neutrino Observatory (INO) is a proposed pure-Science underground laboratory. Its primary goal is to study the properties and interactions of weakly interacting, naturally occurring particles, called neutrinos.  There is world-wide interest in this field due to its implications for several diverse and allied fields such as particle physics, cosmology and the origin of the Universe, energy production mechanisms in the Sun and other stars, etc.

In fact, other neutrino labs, also underground, have been running for several years in places such as Japan, Italy, and Canada. The experiments proposed at INO will be complementary in nature to the existing ones. While many experiments have studied neutrinos from the Sun and other stars, INO will study atmospheric neutrinos that are naturally produced by the interaction of cosmic rays in Earth’s own atmosphere.

Several groups belonging to different Universities, IITs and research Institutes in India are part of the collaboration working on the research & development of all components of INO. This is an open collaboration and interested people are welcome to join. The current proposal focuses on neutrino detection with static detectors, to be placed deep underground at a suitable site.

India-based Neutrino Observatory

New INO site at West Bodi Hills near Madurai

The India-based Neutrino Observatory (INO) is an effort aimed at building a world-class underground laboratory to study fundamental issues in science. It is a mega-science project under the XII five-year plan of Government of India with an investment of about 1350 crores, jointly funded by the Department of Atomic Energy (DAE) and the Department of Science and Technology (DST).

The ambitious INO proposal has already drawn the worldwide attention of both national and international scientists. Once completed it will be the largest basic sciences project in India.

At present, nearly 26 institutions and about 100 scientists are involved in the INO collaboration with Tata Institute of Fundamental Research, Mumbai, being the host institution. This large collaboration is the first of its kind in the country and is expected to grow further.

The laboratory is to be located in Tamil Nadu as the steep slopes of the western ghats provide ideal and stable rock conditions for building a large underground cavern,

The primary goal of the laboratory is the study of neutrinos from various natural and laboratory sources using an iron calorimeter (ICAL) detector. It is envisaged that such an underground facility will develop into a centre for other studies as well, in physics, biology, geology, etc., all of which will make use of the special conditions that exist deep underground.

The ICAL detector that will be installed in the INO laboratory will be the world’s most massive detector. Such an effort will involve INO-Industry interface in a big way, in issues related to mechanical structure, electronics and detector-related technology. It is being developed completely indigenously.

Apart from pursuing neutrino physics goals, the laboratory itself will greatly aid the development of detector technology and its varied applications (which have so far been in the areas of medical imaging).

Students of science and technology within the country, particularly those residing in Tamil Nadu or neighbouring states, will have the opportunity to involve themselves in research involving cutting-edge science and technology.

INO has no strategic or defence applications. Its operation involves no radioactivity release or toxic emission

What are the highlights of the proposal?

The INO proposal consists of creating two underground laboratory caverns with a rock cover of more than 1000 metres all around to house detectors and control equipment’s. An access tunnel of length 2 km (approximate) to reach the underground laboratory will be driven under a mountain to reach the laboratory caverns. The surface facilities near the portal will consist of a laboratory and some housing for the scientists, engineers and operating staff. There will be no other tunnels and hence no disturbance on top or the sides of the mountain; the only entrance to the underground cavern will be at the bottom of the mountain.

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What will be the detector that will be housed at INO?

The detector housed in the INO laboratory initially will be a magnetised iron calorimeter detector (ICAL). It is a static device without moving parts. Just as a telescope observes the sky through visible light, the ICAL will observe the sky through neutrinos.

Charged particles produced in the rare interactions of neutrinos with the iron (constituting the 50 kton, 1.3 Tesla magnet) will be detected in glass based detectors called RPCs sandwiched between successive iron layers. The penetrating ones, such as muons, will be tracked in space and time to identify their charge (+/−) and momentum. In addition to ICAL, several small experiments may also be housed in INO.

What were the factors in deciding the location of the project?

Since the laboratory cavern needs to be more than 1000 m underground (so that there is at least 1000 m cover all-round to absorb/reduce natural cosmic radiation), the choice of site is primarily dictated by the rock quality, in order to obtain a stable safe environment for such long-term activity. Geologically, southern Indian mountains have the most compact, dense rock (mostly gneiss) while the Himalayas are mostly metamorphic sedimentary rock with pockets of gneiss. A considerable area of peninsular India, the Indian Shield, consists of Archean gneisses and schists which are the oldest rocks found in India. While the Karnataka region has more schistic type rocks, the rock found in BWH is mainly Charnockite, which is the hardest rock known. The mountains of Tamil Nadu, in general, are the most attractive possibility, offering stable dense rocks with maximum safety for locating such a laboratory. Apart from this, availability of water and power and easy access to the site for maximum work efficiency are other factors.

Where is the project located?

The proposed site for INO is located in the Bodi West Hills region, about 2 km from the nearest village Pudukottai in Pottipuram Panchayat, Theni District of Tamil Nadu. The nearest major city is Madurai about 110 km away. It is also the nearest airport and a major railway station.

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The portal is proposed to be located outside the RF boundary in puramboke (revenue) land along with surface facilities. This land, about 26.85 Ha in area, has now been acquired for INO. The Cavern will be located about 1300 metres deep under the 1589 peak.

The proposed site for INO is located in the Bodi West Hills region, about 2 km from the nearest village Pottipuram, Theni District of Tamil Nadu.  The portal (entrance to tunnel), the lab complex and the surface will be in Theni district.

A vision for INO and the challenge

INO has been conceived on a scale that no other basic sciences project in India has attempted. The MoU signed by seven institutions, that brought the Neutrino Collaboration Group into existence, is already the first of its kind. It is a testimony to the enthusiasm and collaborative spirit shown by the scientific community in India.

In the first phase of its operation a magnetised iron calorimeter detector, weighing about 50,000 tons, will be used for studying neutrinos produced from cosmic rays in Earth’s atmosphere. The aim is to make precision measurements of the parameters related to neutrino oscillations. An exciting possibility is to determine the ordering of the neutrino masses which is not very well known at present. This is one of the fundamental open questions in neutrino physics and no other detector either existing or planned except perhaps NOνA may be able to provide an answer in the next 10 years. Because of its ability to distinguish the positive and negative muons, this detector can settle this question.

This detector can also be used as the far-detector of a long-base-line (6000 to 11500 km) neutrino experiment using the neutrino beam from a neutrino factory in Japan, Europe or USA. These are neutrinos that will be produced in a future accelerator facility which are beamed towards the detectors situated in a different part of the Earth. This is envisaged as the second phase of the INO activity, and is a long-term goal, since neutrino factories are yet to become a reality. However, there is considerable interest in this possibility not only for the rich physics potential but also because the proposed detector at INO will be capable of charge identification, which is crucial for this mode of operation.

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INO will have an impact on the emerging high energy physics scenario in the country. People trained at INO will not only participate here but also have the expertise to contribute to other high energy and nuclear physics projects around the world. Over the long term INO is expected to develop into a world class underground science laboratory straddling many fields like physics, biology, geology and allied engineering fields.

Members of INO are acutely aware that the laboratory is likely to be located in an environmentally and ecologically sensitive environment. During its normal operation phase, the laboratory is not expected to cause any damage to the environment. All efforts will be made to minimise the disturbance during the construction phase.

INO is looking for scientists and engineers who will enjoy the challenge of setting up an entirely new facility to do world class research. Now is the right time to join us and make a difference!

INO Highlights

The India-based Neutrino Observatory (INO) is an effort aimed at building a world-class underground laboratory to study fundamental issues in science. It is a mega-science project under the XII five-year plan of Government of India with an investment of about 1350 crores, jointly funded by the Department of Atomic Energy (DAE) and the Department of Science and Technology (DST).

The ambitious INO proposal has already drawn the worldwide attention of both national and international scientists. Once completed it will be the largest basic sciences project in India.

At present, nearly 26 institutions and about 100 scientists are involved in the INO collaboration with Tata Institute of Fundamental Research, Mumbai, being the host institution. This large collaboration is the first of its kind in the country and is expected to grow further.

The laboratory is to be located in Tamil Nadu as the steep slopes of the western ghats provide ideal and stable rock conditions for building a large underground cavern, safely, for long-term use.

The primary goal of the laboratory is the study of neutrinos from various natural and laboratory sources using an iron calorimeter (ICAL) detector. It is envisaged that such an underground facility will develop into a centre for other studies as well, in physics, biology, geology, etc., all of which will make use of the special conditions that exist deep underground.

The ICAL detector that will be installed in the INO laboratory will be the world’s most massive detector. Such an effort will involve INO-Industry interface in a big way, in issues related to mechanical structure, electronics and detector-related technology. It is being developed completely indigenously.

Apart from pursuing neutrino physics goals, the laboratory itself will greatly aid the development of detector technology and its varied applications (which have so far been in the areas of medical imaging).

Students of science and technology within the country, particularly those residing in Tamil Nadu or neighbouring states, will have the opportunity to involve themselves in research involving cutting-edge science and technology.

INO has no strategic or defence applications. Its operation involves no radioactivity release or toxic emissions.

Benefits of Neutrino Project?

Neutrino research has immense physics potential and societal value as well. The research will have implications for astrophysics, phenomenology and particle physics. Neutrinos hold the key to several fundamental questions on the origin of the Universe and the energy production in stars. Neutrinos can be used for tomography of the earth and human body also and they are less hazardous than X-rays. Neutrinos may tell us more about dark energy and dark matter and ultimately help us exploit them as the earth is getting depleted of its material and energy sources.

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Raja Raja Cholan
About Raja Raja Cholan 615 Articles
Trainer & Mentor for aspirants preparing for civil service examination

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