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Variable Energy Cyclotron Centre, Kolkata


Tapan Kumar Rana defended his PhD thesis
Posted by: Tilak Ghosh on 12th May, 2015

For life in the universe to be possible you need sufficient amount of carbon. You can’t think about life without oxygen. These heavier elements (carbon/oxygen) were produced in stellar nucleosynthesis process in the fusion of (3/4) 4He nuclei. The production of carbon would not occur with sufficient amount (abundance) unless the probability of the formation of 12C was boosted by the presence of its excited nuclear state at about 7.65 MeV. This excited state is known as the Hoyle state that was predicted by Fred Hoyle. Today, Tapan Kumar Rana successfully defended his PhD thesis that studied the structure and decay mechanism of the Hoyle state.

(Photo adopted from Samir Kundu’s facebook post: Tapan Kumar Rana delivering his thesis seminar at the N.K. Ganguly lecture hall,VECC.)   

During his thesis work, Tapan with the other members of his group, extensively worked under the supervision of Dr. Chandana Bhattacharya, to build a charged particle detector array (CPDA) that consists of 24 telescopes, made of silicon strip and cesium iodide crystals. He used few of these telescopes to detect the alpha particles from the decay of the Hoyle state that was produced by bombarding alpha particles (from our K130 cyclotron) on 12C target.

The high statistics measurements of Tapan, revealed that the decay of the Hoyle state proceeds exclusively as a sequential two-step process via the ground state of 8Be. From detail simulation work he estimated that only less than 1% of the events proceed through the direct 3 alpha decay. This finding will have significant impact on nucleosynthesis reaction rate calculation.

Congratulations Dr. Rana!