LPS Colloquium on Plasma Science & Application featuring Dr. Farhat N. Beg
Proton Fast Ignition: High Gain Inertial Confinement Fusion Scheme
Dr. Farhat N. Beg
Professor and Director of the Center for Energy Research, University of California San Diego
The recent demonstration of nuclear fusion ignition at the National Ignition Facility (NIF) is a major milestone towards harnessing the power of inertial fusion energy (IFE) . One of the main challenges to IFE application is to increase the target energy gain to make it economically viable. To address this, alternate inertial fusion schemes have garnered substantial interest due to their potential for higher gains. One such promising scheme is fast ignition, in which compression and ignition phases are separate. In this scheme, heating of a compressed fuel is accomplished using energetic particle beams. Heating with protons/ions, as compared with electrons, is particularly attractive due to their heavier mass, making them less prone to instabilities, and more localized energy deposition. The main requirements for proton fast ignition (PFI) are: beam focusing to a diameter of 35-50 μm, proton energies in the range of 5-20 MeV with a Maxwellian proton distribution, and a laser-to-proton conversion efficiency on the order of 10-15%, based on laser energy of ~100 kJ. We have carried out simulations and a series of experiments on the Omega laser facility with 0.1-1 kJ energy and 1-10 ps laser pulses to explore requirements for PFI. These simulations and experiments show that the proton energy scaling and conversion efficiency significantly varies with both laser energy and pulse length. Even with modest laser intensities of 1017-1018 W/cm2, when the pulse duration is multi-picosecond, protons can be accelerated to energies that significantly exceed those predicted by pondermotive scaling. Adding a conical structure to the hemi target enhances proton focusing to <100 μm [4] and brings the proton energy into the range required for PFI. These results have brought us closer to meeting some of the requirements (beam energy, spectrum, and beam size) for proton fast ignition. However, certain physics challenges still need to be addressed, which will be discussed.
Host: Gennady Shvets
Open talk with students – 120 Physical Sciences Building , 2:15 p.m. – 3:15 p.m.
Join us for a reception before the talk from 3:45 until 4:15 p.m.
Farhat Beg received his Ph.D. from Imperial College London. He joined Department of Mechanical and Aerospace Engineering, UC San Diego in 2003 as an Assistant Professor, where he is currently Shao-Chi and Lily Lin Chancellor’s Endowed Chair in Engineering Science and a Professor in Engineering Physics. His expertise is in the field of High Energy Density Science. He addresses important questions pertinent to matter under extreme conditions of pressure, density, temperature, and magnetic field. He has published over 280 articles in top-notch journals such as Nature, Nature Physics, Nature Communications and Physical Review Letters with an H-index of 51. He has been a recipient of several awards including Department of Energy Early Career Award, Institute of Electrical and Electronics Engineers (IEEE) Early Career Award, and IEEE Plasma Science and Applications Award. He is the fellow of three professional societies: the American Physical Society (APS), IEEE and, the American Association for the Advancement of Science.
