During my stay at Optical Instrumentation Lab of Department of Mechanical Engineering, I had worked on two projects.

• Observation of laser-produced plasma-induced shockwaves: Designed and developed a Mach Zehnder interferometer to capture the propagation (and reflection of shockwaves from physical boundaries) through air and liquid (of different densities). Due to the transient and short-lived nature of the phenomena the images were captured using an intensified CCD with exposure ranging from 10 to 25 ns. A method to fabricate size-controlled nanoparticles by laser ablation of metals in liquid  has also been demonstrated.

• Cryo-SEM Imaging: I was trained on (JEOL make) crogenic-SEM for imaging biological samples. I have been doing it for 15 months and have imaged a variety of samples ranging from biological to gels to soft and hard materials. 

• Experimental observation of the non-contact crystalisation of molten chnodrules: Since the time immemorial the sky has intrigued the humans – it has been a storybook for the kids, full of characters, and an unsolved puzzle for the inquisitive minds. Almost as old is the quest to find out the truth about how this all began and the universe, albeit the known part of it, became the way we see it today. Volumes of literature documenting the findings of the extensive investigations carried out by the researchers across the globe stands as evidence to that quest.

Studies mostly involve recording and analyzing the data collected by astronomical means like telescopes (terrestrial and space-based, optical and radio) and exploratory missions sent to space. However, studying the remnants of meteors and other such objects coming from the outer space to earth surface once in a while has been of interest to physicists and earth & planetary scientists. Their chemical composition, shape, morphology, crystallinity etc. give a lot of information about the conditions under which they were formed, their age and about their journey to earth. Interestingly this information also enables us to trace back to the events that took place in the formative days of our solar system. Put in a different way these meteor-remnants; for example, give us a glimpse through the veil of time.

The study involved designing of a highly sophisticated experimental set-up with very precise control over ambient conditions like, temperature, pressure etc. to assimilate the conditions that prevail in space. Under these conditions, a compound of magnesium, silicon and oxygen known as, Forsterite (which is the major constituent of the meteorites hitting the earth surface) was first melted by heating to temperatures above 2200oC and then let to cool down and solidify. Interestingly, during the entire duration of experiment the Forsterite sample was kept floating on a gas jet and was not let to come in contact with any physical object, exactly in the same way as the planets were formed due to the cooling of molten minerals floating in space without coming in contact with any other physical entity. Also, the experiments involved partial vacuum in the ambient so as to get closer to the real conditions in space. The results of the experiments are very promising and stand as direct experimental evidence to some of the previously published theoretical and computational results in this area. The study links the formation of surface structures, which are seen in meteorite samples, to the way of cooling and the ambient conditions prevailing during the process of solidification. 

This kind of experiments, under low pressure conditions have been conducted for the first time to the best of the knowledge of the team of IIT Bombay and is believed to have suggested a new approach to experimentally verify some of the theoretical predictions made earlier based on computer simulations. It is believed that this study will interest physicist and planetary scientists to explore further in this area and help them to come up with the compelling evidences to put an end to some of the longstanding debates in the area of formation of planets. 

Publications:

• Mishra, B., Manvar, P., Choudhury, K. et al. Experiments to understand crystallization of levitated high temperature silicate melt droplets under low vacuum conditions. Sci Rep 10, 20910 (2020). https://doi.org/10.1038/s41598-020-77965-4

• Kaushik Choudhury, R.K. Singh, P. Kumar, Mukesh Ranjan, Atul Srivastava, Ajai Kumar, Effect of confined geometry on the size distribution of nanoparticles produced by laser ablation in liquid medium. Nano-Structures & Nano-Objects 17, 129 (2019). https://doi.org/10.1016/j.nanoso.2018.12.006

• Kaushik Choudhury, R. K. Singh, Mukesh Ranjan, Ajai Kumar, and Atul Srivastava "A novel method for fabrication of size-controlled metallic nanoparticles by laser ablation", Proc. SPIE 10603, Photonics, Devices, and Systems VII 1060304 (2017); https://doi.org/10.1117/12.2292804

• Choudhury, K., Singh, R.K., Narayan, S. et al. Time-resolved whole field investigation of plasma plume-induced shock wave in liquid media of different densities. Appl. Phys. B 123, 163 (2017). https://doi.org/10.1007/s00340-017-6740-9

• Kaushik Choudhury, R. K. Singh, Surya Narayan, Atul Srivastava, Ajai Kumar, Time resolved interferometric study of the plasma plume induced shock wave in confined geometry: 2D mapping of the ambient and plasma density, Physics of Plasmas 23, 042108 (2015). https://doi.org/10.1063/1.4947032