Speaker: Bill Heidbrink, UC-Irvine
Title: “A research program to measure the lifetime of spin polarized fuel”
Abstract: Nuclear physicists have known for decades that the fusion cross section depends upon the nuclear spin state of the reacting nuclei. For example, for deuterium-tritium (D-T) reactions, aligning the nuclear spins parallel to the magnetic field increases the cross section by a factor of 1.5. Because fusion reaction products will heat the fuel ions in a fusion reactor, a 50% increase in cross section nearly doubles the fusion power, relaxing the requirements to achieve a practical fusion reactor. Furthermore, the higher probability of a reaction substantially reduces the required tritium inventory. A key question is: will spin polarized fuel remain polarized in a fusion reactor environment? Theoretically, the two most important depolarization mechanisms are hyperfine interactions with bound electrons and resonances with electromagnetic waves at nuclear precession frequencies—the process that occurs in magnetic resonance imaging. For reasons I’ll explain, despite the rich spectrum of electromagnetic waves in the fusion environment, it is theoretically predicted that the polarization lifetime will exceed the amount of time the fuel spends in the plasma. Plans to measure the polarization lifetime on the DIII-D tokamak using cryogenic LiD and 3He shell pellets will be discussed, as well as prospects for experiments at other facilities.
Bio: William "Bill" Heidbrink is a Professor of Physics and Astronomy in the School of Physical Sciences at the University of California, Irvine. Professor Heidbrink earned his B.A. degree from the University of California, San Diego in 1977. For the next two years he performed industrial research in pulsed power at Maxwell Laboratories. In 1984, he received his Ph.D. from Princeton University. After working as a staff member on the TFTR tokamak (Princeton) and the DIII-D tokamak (General Atomics), he joined the UCI Physics Department in 1988. He also has won the UCI "Lauds and Laurels" Distinguished Teaching Award and is a Fellow of the American Physical Society. In 2004, he received the Excellence in Plasma Physics Research award from the Americal Physical Society. Professor Heidbrink's research involves studies of "fast" ions in magnetized plasma.
This talk will be offered in a hybrid format. If you wish to participate remotely, please send an email to [email protected].