Scintillators to detect cosmic rays are spread over GRAPES-3 experiment site
For several decades now, Ooty has been playing host to a series of experiments on cosmic rays, which have given remarkable insight into the workings of the universe. In fact, the first experiment in Ooty was started way back in 1955 by the celebrated astrophysicist B V Sreekantan.
Cosmic rays are high-energy radiation, composed mainly of protons and other atomic nuclei, believed to be coming in from faraway distances in our galaxy. Scientists are not entirely certain about the origin of these cosmic rays though they are believed to be produced in supernova explosions. How these particles are accelerated to such energies is not very well understood either. Scientists across the world are studying cosmic rays in the hope of unlocking more secrets of nature.
Currently, the third generation of these cosmic rays experiments, named GRAPES-3 (Gamma Ray Astronomy PeV EnergieS), are being conducted in Ooty. One of the main objectives is to study the acceleration of cosmic rays in different astrophysical settings. Last year, this experiment gave us a result that made international headlines in most parts of the world.
We established a direct link between a solar storm on June 22, 2015, containing magnetised plasma of protons, and an unusually large amount of cosmic rays that reached Earth’s surface immediately thereafter. We could show that the increase in cosmic rays reaching Earth’s surface was caused by weakening of Earth’s magnetic field due to the solar storm. Inherent in the result was the possibility of evolving an early warning system on potentially dangerous solar storms that could disrupt power lines and much else.
The scientific contributions of the GRAPES-3 experiment have been fairly well acknowledged. What is not appreciated as well are the spinoffs that these experiments have yielded for Indian science.
These spinoffs include a large number of innovations in indigenous technology development. Most of the key detectors and electronics being used in the experiments have been developed in-house as a result of years of research and development, and of the need to find local solutions to the very unique problems posed by the experiments.
One of the most prominent examples of this success in technology development is the production of high-quality plastic scintillators that act as detectors for cosmic rays. These scintillators, housed in cone-shaped containers spread all over the facility in Ooty, are one of the most important components required for detection of charged particles. About 400 of these are installed in Ooty. Earlier, high-quality scintillators had to be imported, each costing over Rs 1 lakh. Thanks to our R&D, we are able to produce them at a fraction of that cost. The entire group of scintillators now being used are produced in-house.
The same is the case with the large-area muon detector. Muons are another of the fundamental particles, similar to electrons but with a greater mass. Nearly 4,000 large proportional counters are at the heart of this muon detector. To double the area of the muon detector, the same number of proportional counters are being produced in the laboratory. Strict quality control ensured that these proportional counters have a lifetime of 30 years.
Similarly, most of the high-end electronics in use in the experiment have also been produced by us. This indigenisation has had several benefits apart from vast reductions in cost. Scientists working at the facility were able to learn something completely new and gained confidence and expertise in instrumentation engineering. It also enabled in-house servicing and maintenance of the equipment. Malfunctioning instruments were no longer required to be sent abroad for repair.
That in turn meant that the experiments could be run uninterrupted apart from money saved. This is crucial for the kinds of experiments being run at Ooty. One does not know when a scientifically valuable celestial event might happen. The experimental setup needs to be running all the time to make the detection. Had our experiment not been ready on June 22, 2015, we would have completely missed discovering this spectacular phenomenon affecting the earth that day.
