New experimental setup investigates plasma’s unusual behavior in strong magnetic fields

Historically, challenges associated with coupling a short high energy laser pulse with a strong magnetic field limited plasma dynamics research. A new experimental setup, described in Review of Scientific Instruments, investigates how strong magnetic fields change plasma behavior in high-intensity laser plasma interactions. This platform features the Nevada Terawatt Facility’s synchronized 50-terrawatt “Leopard” laser and 1-mega-amp “Zebra” pulsed power generator that creates plasma in a strong magnetic field.

Although pulsed power machines with currents greater than 1 mega-amp operate at other facilities, the authors report that this research is the first of its kind to couple the generator with a 50-terawatt laser. Coupling the devices is significant because prior computer simulations showed that strong magnetic fields, like those induced by the Zebra generator, could enhance the acceleration of proton beams, collimate and confine fast electrons in plasma, and model astrophysical events.

In this setup, the Leopard laser converts a target to plasma inside a vacuum, while the Zebra generator induces a magnetic field around the devices. Meanwhile, a diagnostic laser measures the plasma’s changing behavior within the magnetic field. The plasma exhibited unusual dynamics. For example, it formed a disc in the circular magnetic field and generated long, dense jets in the axial magnetic field.

Going forward, the researchers plan on using dielectric plastic and silicon targets, rather than aluminum, to reduce the impact of the metal’s eddy currents on the plasma’s behavior. This work could reveal more about how plasma undergoes isochoric heating in a strong magnetic field. Understanding of plasmas in strong magnetic fields has implications for astrophysics, basic physics and fusion research.

Source: “Experimental platform for investigations of high-intensity laser plasma interactions in the magnetic field of a pulsed power generator,” by V. V. Ivanov, A. V. Maximov, K. J. Swanson, N. L. Wong, G. S. Sarkisov, P. P. Wiewior, A. L. Astanovitskiy, and A. M. Covington, Review of Scientific Instruments (2018). The article can be accessed at https://doi.org/10.1063/1.5016973 .

Described work was supported by the DOE grant DE-SC0016500.