Indian physicists first to record high-energy phenomenon

Wednesday, 27 November 2002, 20:30 IST
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NEW DELHI: A team of Indian physicists have become the first in the world to record in detail a high-energy phenomenon that could impact nuclear fusion reaction designs and systems where high magnetic fields are important. The seven-member team from the Tata Institute of Fundamental Research (TIFR) in Mumbai and the Institute of Plasma Research (IMR) in Gandhinagar recorded precisely the huge short-duration magnetic spike encountered in atoms in a sample hit by an intense laser shot. The team reported the finding on the rapid measurement of high magnetic fields in the November 25 issue of the journal "Physical Review Letters" published by the American Physical Society. Understanding the fields is important for realising laser fusion -- bringing two atomic nuclei together to produce energy by hitting them with lasers, which holds promise as an energy source for mankind. Giant magnetic fields affect the movement of very "hot" electrons that create them. The chief achievement of Indian researchers was to look at this process with "unprecedented precision" -- monitoring the rising magnetic field in intervals of a femtosecond, or millionth of a billionth of a second, the American Institute of Physics said in its Bulletin of Physics. The discovery also has bearing on areas like futuristic information storage systems and fast switching devices, where high magnetic fields are important. When high-intensity light pulses produced by lasers strike an aluminium target, the surface layer of atoms is quickly ionised, and a stream of very fast "hot" electrons is released into the body of the target. These electrons produce a very high level of current quickly induces a magnetic field, which can be roughly 50 million times the strength of the Earth's. The final stage of a violently excited state of matter created by such electron excitations is called plasma. Such magnetic fields, which exist only for extremely small time intervals, have been known for about 30 years. They typically exist inside stars and in laboratory plasmas created by ultra-short laser pulses on Earth. "What scientists did not know till our study was done, was the duration for which such fields are 'on', particularly for ultra-short pulse excitation. We have looked at the growth and decay (of such fields) in femtosecond intervals," TIFR co-researcher G. Ravindra Kumar told IANS. Other researchers involved were TIFR's Arvinder S. Sandhu, Aditya Dharmadhikari and P.P. Rajeev, and IPR's Sudip Sengupta, P.K. Kaw and Amita Das. Such studies are extremely important for understanding the behaviour of matter under extreme impulses, laboratory simulations of conditions inside stars, and nuclear magnetic resonance (NMR) studies of biological molecules, he said.
Source: IANS