2014 Fall Physics Graduate Colloquium: Eva Kostadinova/Madhurima Bhattacharjee

DateOctober 10, 2014
Time3:35 - 5:00 pm
LocationBaylor Sciences Building, Room E.125
Eva Kostadinova

Energy Yields In Inertially Confined Fusion Implosion

Based on the article: Fuel gain exceeding unity in an inertially confined fusion implosion by O. A. Hurricane et al; Nature, 506, 343–348, 20 February 2014

In order to create self-sustaining nuclear fusion reaction to be used as a practical energy source, scientists need to achieve fusion ignition, which is the point where the energy produced by the fusion reaction exceeds the energy needed to trigger the reaction on the first place. Recently a team of scientists in the National Ignition Facility (NIF) at the Lawrence Livermore National Laboratory (LLNL) managed to obtain energy gain exceeding unity in an internally-confined fusion implosion and demonstrated the phenomenon of self-heating that is crucial for fusion ignition. In their setup the NIF researchers use a 192 ultraviolet laser, whose beams are converted into x-rays and then focused on a plastic fuel sphere containing a sample of frozen deuterium and tritium. The intense x-ray pulse hitting the capsule causes some of the plastic to blow off driving the remaining plastic and the frozen fuel in toward the center at high speed. The method produces a fuel ball hot enough and dense enough to initiate fusion. The key problems researchers needed to overcome to increase efficiency are the non-symmetric compression of the fuel pellet and the possible break up of the plastic capsule during the implosion. The energy yields produced by the NIF team were 10 times greater than yields achieved by other laboratories so far. Furthermore, the researchers demonstrated a self-heating phenomenon where the alpha particles produced by the fusion reaction helped heating the surrounding cooler fuel up to reaction temperature, which considerably facilitates ignition. This presentation aims to introduce the method used by the NIF researchers, explore its advantages over other existing techniques, and discuss its capacity of achieving self-sustaining fusion in the near future.

Madhurima Bhattacharjee

Triple Slit Experiments and the role of Non-Classical Paths in Quantum Mechanics

Most Quantum Mechanics texts assume, implicitly or explicitly, that in double-slit experiments the wave function at the screen with both slits open is equal to the sum of the two wave functions with one of the slits individually closed. However a recent study has shown that the three scenarios, with both slits open and one of the slits closed one at a time, has three different boundary conditions and as such superposition principle is not directly applicable. In this talk we will demonstrate how one can use the Feynman Path Integral formalism in quantum interference experiments to show that there are quantifiable contributions from "Non-Classical Paths" which deviates from the naive direct application of the superposition principle. Further we will discuss how a simple triple slit interference experiment can be set up where this contribution from non-Classical Paths can be tested directly.
PublisherDepartment of Physics
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