Speaker
Description
We have carried out calculations demonstrating the benefits of having spin polarized
fuel in future tokamak fusion reactors and the viability of testing spin polarized
fuel in current tokamaks. The cross section for D-T (deuterium-tritium)
fusion is increased by 50% when the nuclei spins are parallel to the tokamak
guide field. In future magnetic confinement fusion reactor power plants the
increased reactivity of using spin polarized fuel would lessen the engineering requirements
(magnetic field, plasma current, major radius) on those reactors or
increase their power output for the same engineering parameters. Of particular
concern for future reactors is any degradation over time in capability of the various
components due to prolonged high neutron fluence from the D-T reactions;
using spin polarized fuel could mitigate the consequences of moderate degradation.
For instance, using fuel that is completely spin polarized could yield an
increase in reactivity to make up for a 13% loss in toroidal magnetic field. On
the other hand, with fixed engineering parameters, complete spin polarization
of the fuel would yield a 75% increase in power output due to non-linear stabilization
of heat transport at the higher pressures. An outstanding question for
the future viability of spin polarized fuel in magnetic confinement reactors is
whether the spin polarized fuel can retain its polarization through injection into
the plasma and then through the energy containment period. We have carried
out simulations that show that introducing spin polarized D and He3 pellets
in high performance discharges in the DIII-D tokamak will produce measurable
levels of fusion products, whose poloidal distribution and quantity can be unique
to the spin states of the fuel, and can then be used as an indicator of the retention
of polarization through the fusion process. Ongoing research at Jefferson
Lab, University of Virginia, and General Atomics is focused on refining existing
methods and technology to prepare spin polarized fuels for injection into
burning plasma scenarios in order to verify these results in existing tokamaks
