Speaker
Description
As part of a Spin Polarized Fusion (SPF) program, polarized $^7$LiD pellets are being developed at Jefferson Lab (JLAB) for testing the survivability of nuclear polarization in a ∼100 million Kelvin fusion plasma. With polarized fuels in a tokamak, the cross section can increase by 50%, and the power gain of a large-scale fusion reactor, such as ITER, by 75%. However, this power gain can only be realized if the fuel polarizations survive for periods comparable or longer than the particle confinement times (at least times in the order of seconds). Recently, the initial phase of an in-situ demonstration of polarization survivability in a tokamak plasma, proposed by the SPF collaboration, has been funded to answer this crucial question. In the next few years, we plan to prepare polarized $^7$LiD pellets and $^3$He capsules for injecting into the plasma at the DIII-D tokamak of the DOE National Fusion Facility in San Diego, using the isospin-mirror reaction, D+$^3$He→$a$+p; this will mimic the standard D+T→$a$+n fusion process without introducing tritium. For the next 2 years at JLAB, $^7$LiD pellets made with fusion specifications will be irradiated with electron beams at the newly built Irradiation Beamline at the CEBAF Injector; irradiations will be carried out at ∼185K to induce paramagnetic centers, and then stored at 77K. A DNP polarizer, with a pellet handling system suitable to manipulate single $^7$LiD cylinders of ∼2 mm in size, and capable of polarizing many pellets simultaneously at ∼7 Tesla and ∼100 mK, will be designed based on a commercial dry dilution refrigerator. A prototype polarizer will be tested at room temperature to verify the mechanical and electrical functionalities. In phase−II, the full device will be built at JLAB to produce polarized $^7$LiD pellets for mating to a tokamak cryo-injection gun. The SPF experiment at DIII-D will be carried out in phase−III. In parallel, efforts are also underway at UVA, ORNL, UC-Irvine and DIII-D to prepare for the SPF experiment. Details will be discussed.
