Image courtesy of Riccardo Betti
A double coil is assembled on the transmission line of the magnetic field generator (MIFEDS) by Mr. PY Chang, PhD student at the University of Rochester. The MIFEDS device discharges 50 kA of current through the coil generating a ~10 Tesla magnetic field used to magnetize laser-driven targets.
Magnetic fields can significantly alter the properties of plasmas and can be a key tool in fundamental studies of plasma dynamics. Magnetizing the high energy density (HED) plasmas created in laser-driven implosions requires ultra high magnetic fields, which are difficult to create. For the first time, those large fields have been produced and used to reduce the thermal conductivity of such plasmas.
Magnetic fields in high energy density plasmas can be used to study a variety of basic science phenomena from collisionless shocks to magnetic reconnection, as well as to improve the performance of inertial fusion implosions.
The Office of Fusion Energy Sciences (FES) has supported basic research at the University of Rochester to explore and control the properties of high energy density plasmas. Given the ultra high pressures of tens of gigabars of such plasmas, controlling their properties has always been an outstanding challenge. Using magnetic field compression as a tool to generate ultra high magnetic fields, the Rochester group has successfully produced a hotter core of a laser-driven capsule by magnetizing the central plasma heated by an imploding shell. An initial seed magnetic field is embedded in a tiny spherical shell imploded by a high energy laser. The magnetic flux is frozen in the ionized gas inside the shell and then self-amplified as the target implodes. In this way, a magnetic field of 20 megagauss is achieved from a 50 kilogauss seed field. The compressed field magnetizes the electrons and reduces the heat losses thus increasing the temperature and fusion reactivity of the compressed core. The ability to control the properties of these plasmas with a magnetic field opens the way to many exciting studies with applications to astrophysics and fusion energy. The experimental platform developed by the Rochester scientists is available to outside users for future science experiments.
Laboratory for Laser Energetics
University of Rochester
Office of Science Fusion Energy Sciences (FES) program
PY Chang et al., “Fusion Yield Enhancement in Magnetized Laser-Driven Implosions,” Phys. Rev. Lett. 107, 035006 (2011); O. Gotchev et al, “Laser-Driven Magnetic-Flux Compression in High-Energy-Density Plasmas,” Phys. Rev. Lett. 103, 215004 (2009).