Going all out for neutrino research
A. P. J. ABDUL KALAM
SRIJAN PAL SINGH
India lost its lead in neutrino studies when research tapered off in the 1990s. The India-based Neutrino Observatory can now help it reclaim this advantage and its global leadership in understanding this mysterious particle
Just a few years ago, we witnessed how a national project, the India-based Neutrino Observatory (INO), which is to study fundamental particles called neutrinos, was subject to a barrage of questions from environmentalists, politicians and others ever since it was cleared. The project, which involves the construction of an underground laboratory, was initially to be located in the Nilgiris but later, on grounds that it was too close to tiger habitat, was moved to a cavern under a rocky mountain in the Bodi West Hills region of Theni district, about 110 kilometres west of Madurai in Tamil Nadu.
The already much-delayed and important physics project needs to be explained.
Reclaiming India’s position
India has been among the pioneers in neutrino research, the first of such laboratories having been established in the 1960s. We led neutrino research when our physicists used a gold mine at Kolar in Karnataka to set up what was then the world’s deepest underground laboratory. This was called the Kolar Gold Field Lab. In 1965, it enabled researchers to detect atmospheric neutrinos. In 1992, when the mine became uneconomical, the laboratory was shut down. With that, we lost our advantage in understanding the most mysterious particle in the universe. INO may reclaim this advantage and our global leadership.
Most of the advanced countries are already working vigorously in neutrino science with dedicated labs. These include the United States, Russia, France, Italy, China, Japan and South Korea. India is set to not only join this league, but also become a key player in global efforts in neutrino science. The Magnetized Iron Calorimeter (ICAL) being set up at INO will be among the largest ever in the world, weighing over 50,000 tonnes.
In 2011, we visited the now much talked about Fermi Lab’s neutrino study laboratory. Located about 60 kilometres from the main city of Chicago, the laboratory has been pioneering some major work in understanding elementary particles including neutrinos. In this laboratory — which is deep within the ground and accessible through a large elevator — we could witness the sense of pride among the staff for having such a facility for advanced particle study which could unravel the universe. A professor said, “Fermi Lab is the pride for Chicago. We are happy to see Fermi Lab so close to the city — it makes it easily accessible to us and students.”
INO is designed to go much beyond Fermi Lab in some aspects of neutrino research; to us, this should be a moment of our national pride.
Widely occurring particle
Neutrinos, first proposed by Swiss scientist Wolfgang Pauli in 1930, are the second most widely occurring particle in the universe, only second to photons, the particle which makes up light. In fact, neutrinos are so abundant among us that every second, there are more than 100 trillion of them passing right through each of us — we never even notice them.
This is the reason why INO needs to be built deep into the earth — 1,300 metres into the earth. At this depth, it would be able to keep itself away from all the trillions of neutrinos produced in the atmosphere and which would otherwise choke an over-the-ground neutrino detector. Neutrinos have been in the universe literally since forever, being almost 14 billion years old — as much as the universe itself.
Neutrinos occur in three different types, or flavours – ve, vμ and vτ. These are separated in terms of different masses. From experiments so far, we know that neutrinos have a tiny mass, but the ordering of the neutrino mass states is not known and is one of the key questions that remain unanswered till today. This is a major challenge INO will set to resolve, thus completing our picture of the neutrino.
Neutrinos are very important for our scientific progress and technological growth for three reasons. First, they are abundant. Second, they have very feeble mass and no charge and hence can travel through planets, stars, rocks and human bodies without any interaction. In fact, a beam of trillions of neutrinos can travel thousands of kilometres through a rock before an interaction with a single atom of the rock and the neutrino occurs. Third, they hide within them a vast pool of knowledge and could open up new vistas in the fields of astronomy and astrophysics, communication and even in medical imaging, through the detector spin-offs.
While this should be a moment of joy, there is also some scepticism, partly arising due to the fact that the neutrino, though so abundant, is a silent stranger to most people.
Public misconceptions
Can neutrinos cause cancer? Not at all! Neutrinos are the least harmful of all elementary particles, as they almost never react with solid bodies. The mean free path for iron, or the average distance a neutrino will travel in say an iron rod, before interacting with an atom, is about 1 light year (9,460,730,472,580 km). Needless to say, with the human body being less than 2 metres in height, any harmful effect of neutrino is near impossible.
A few people with whom we have discussed this topic, tend to confuse the “neutrino” for the “neutron”. This has also led to the confusion that neutrinos can be weaponised, which is far from the truth. The neutron bomb, which many discuss, is dangerous but has nothing to do with harmless neutrinos and is made based on a technology around the neutrons, particles which are much heavier. To put this in perspective, the mass of a neutron is 1.67x10-27 kg while the mass of a neutrino is of the order of 1x10-37 kg . Hence, a neutrino is about 17 billion times lighter than a neutron. The two are incomparable.
There is further misconception that laboratory generated neutrinos, fancily termed as “factory made neutrinos”, are more dangerous than naturally abundant neutrinos. Scientifically, this is not true. Neutrinos are fundamental particles; there is nothing such as a natural and an artificial aspect to them. It is like saying that electricity at the same voltage, from a coal-based plant can give one a more severe shock than electricity produced by a hydroelectric plant.
What can understanding neutrinos give us? A lot, actually.
Key role in science
First, neutrinos may have a role to play in nuclear non-proliferation through the remote monitoring of nuclear reactors. The plutonium-239 which is made via nuclear transmutation in the reactor from uranium-238 can potentially be used in nuclear devices by terrorist groups. Using appropriate neutrino detectors, the plutonium content can be monitored remotely and used to detect any pilferage. Neutrino research can be our answer to ensure that no terror group ever acquires nuclear weapons.
Second, understanding neutrinos can help us detect mineral and oil deposits deep in the earth. Neutrinos tend to change their “flavour” depending on how far they have travelled and how much matter they have passed through in the way. Far more importantly, we believe that this same property might help us detect early geological defects deep within the earth, and thereby might be our answer to an early warning system against earthquakes. This is where an area of Geoneutrinos is applicable. First found in 2005, they are produced by the radioactive decay of uranium, thorium and potassium in the Earth’s crust and just below it. Rapid analysis of these Geoneutrinos by neutrino monitoring stations — a process called Neutrino Tomography — could provide us vital seismological data which can detect early disturbances and vibrations produced by earthquakes.
Data transmission
Third, as we now know, neutrinos can pass right through the earth. They may open up a faster way to send data than the current ‘around the earth’ model, using towers, cables or satellites. Such a communication system using neutrinos will be free of transmission losses as neutrinos rarely react with the atoms in their path. This can open up new vistas for telecom and Internet services. Some scientists further believe that if there is any extraterrestrial form of life, neutrinos will also be the fastest and most trusted way to communicate with them.
Fourth, neutrinos are the information bearers of the universe — which are almost never lost in their path. India’s effort in studying neutrinos at INO may help us unravel the deepest mystery of the universe — why there is more matter than antimatter in the universe.
Some scientists believe that formidable neutrino research can help us understand dark matter. Dark matter and dark energy make up 95 per cent of the universe, far more predominant than ordinary matter in the universe — but we hardly understand it. Neutrinos are the only way to detect this great mystery which may completely alter our understanding of the universe and physics. Searches for this dark matter can only be carried out in INO.
We believe that the neutrino is our mode of access to some of the most unimaginable technologies, and therefore, with INO, India is poised to take its rightful place at the helm of neutrino research. For example, the particle detectors developed for the neutrino experiment at INO can also be used to detect the photons in positron emission tomography (PET) which is used to identify cancerous tumours.
Hundreds of thousands of years ago, a species, Homo sapiens,went about rubbing two small rocks until they ended up producing the spark and then the fire which helped man master the planet. Today, we stand at a point in time when we are on the verge of manipulating fundamental particles with the possibility that they may allow us to master the universe.
