by Niti Nagar
Nuclear fusion seems to answer many concerns that we face with finding new sources of energy. Energy from fusion harnesses the powers of the Sun and provides an unlimited and cheap source of energy, while being pollution-free. Capturing the powers of the heavens has been fantasized in the past as mere science fiction, however this fiction may become a reality. Although development is still in its infant stages, a new breakthrough by lead author Omar Hurricane, from the National Ignition Facility at the federally-funded Lawrence Livermore National Laboratory, published an article in Nature that announced researchers saw a net gain in energy following a fusion reaction. The reported results show almost 2 times more energy coming out of the reaction than what went into it. What does it take to run a reaction of this sort? One hundred and ninety-two of the world’s most powerful lasers aimed at a 1 centimeter gold cylinder called a hohlarum. It is a small capsule that contains an extremely cold mixture of hydrogen isotopes. As the laser heats the capsule, the hydrogen is heated and subsequently compressed to 1/35 of its original size. Co-author Debbie Callahan described it as “compressing a basketball down to the size of a pea.” If the compression is high and uniform enough, nuclear fusion will take place and in the nanoseconds that follows the capsule implosion, neutron energy is released.
Naturally this process occurs in the cores of stars. Unlike nuclear power, which relies on fission, the splitting of atoms, fusion occurs when atoms collide at a very high speed to form a new molecule. In this case, matter is not conserved and some mass dissipates as energy. When this process occurs in large quantities, a chain reaction of fusing releases more and more energy until there is self-sustaining energy source. This process called ignition is the ultimate goal of physicists. Though physicists have obtained net energy, there is still a considerable amount of work that lies ahead before the ignition is reached. Pulse shaping, which describes how lasers hit the hohlarum needs to be further developed, as the shape of implosion is not spherical which is desired for ignition. Additionally the 192 lasers used produce exponentially more energy than what was used in the reaction. It is likely that harnessing the full energy of these lasers may result in higher net gains.
Physicists are essentially trying to create a small, controlled star, so it is no wonder such a long and difficult process. However, the payoff is a limitless power supply. And the waste produced in these reactions are not radioactive, unlike those from nuclear fission, giving it the clear advantage for being a top energy choice. However there is no telling how long it will take to achieve ignition. The most optimistic scientists predict at least few decades.
- A. Hurricane, D. A. Callahan, D. T. Casey, P. M. Celliers, C. Cerjan, E. L. Dewald, T. R. Dittrich, T. Döppner, D. E. Hinkel, L. F. Berzak Hopkins, J. L. Kline, S. Le Pape, T. Ma, A. G. MacPhee, J. L. Milovich, A. Pak, H.-S. Park, P. K. Patel, B. A. Remington, J. D. Salmonson, P. T. Springer & R. Tommasini. “Fuel Gain Exceeding Unity in an Inertially Confined Fusion Implosion.” Nature 506.7488 (2014): 343-48.
“NIF Fuel Gain Named a ‘Top Breakthrough’ of 2014.” Science & Technology. Lawrence Livermore National Laboratory, https://lasers.llnl.gov/news/science-technology
RT News (http://on.rt.com/a3co1k)