Laser Gate Experiment for Magnetized Liner Inertial Fusion (MAGLIF) Utilizing a Mini-Pulser

In Magnetized Liner Inertial Fusion (MagLIF), pressurized fuel inside of a cylindrical metal tube (or “liner”) is preheated with a laser pulse. The laser enters the pressurized fuel region through a thin laser entrance window (LEW). The LEW contains the pressurized fuel inside of the liner until the few-ns preheating laser pulse is applied, which ablates the LEW and preheats the fuel. Energy losses are thought to occur at the laser entrance window (LEW) as a result of laser-plasma interactions (LPI). Additionally, simulations are presently unable to reliably model the LPI losses.
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To reduce energy losses and computational uncertainties, the LEW could be weakened and removed very early in time, well before the preheating laser pulse arrives at the LEW.
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This general concept of removing the LEW very early in time is referred to as “Laser Gate.”2 One proposed implementation of Laser Gate, which we are working on at the University of Michigan, is to break the LEW very early in time by driving an electrical current through a thin wire that is wrapped around the perimeter of the LEW.
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The electrical current heats and melts the perimeter of the LEW, allowing the fuel pressure to push open the LEW. As the LEW is broken, it opens away from the contained fuel and out of the laser path. Before a significant amount of fuel has time to escape the liner, the preheating laser pulse is applied. Doing this successfully should reduce fuel-window mixing and LPI in MagLIF. For our experiments at UM, the pulsed electrical current is driven through the thin wire by a 13-kV mini-pulser. Additionally, a laser backlighting system is being developed to image the dynamics of the LEW as it opens. We will report on our first experimental tests of this implementation of Laser Gate.