Optimization of capillary source geometry for maximum pellet exit velocity in electrothermal plasma launchers

Summary form only given. Deep fueling for large-scale tokamak fusion reactors requires the use of high-velocity fuel pellet injectors. The fuel pellets consist of deuterium or deuterium-tritium ice. Electrothermal plasma guns can be used to launch fuel pellets into the fusion plasma at a range of velocities. The plasma guns can be used to launch pellets at the velocities required for fusion reactor deep fueling or for the control of edge localized modes.Electrothermal plasma guns use a capillary tube where plasma is sparked, called the source, and an acceleration barrel. The plasma is sparked inside the source using a capacitor bank that is charged to 10 kV. A liner material inside the source is ablated and forms plasma that draws up to 40 kA of current over 100 microseconds and can propel a pellet to velocities exceeding 3 km/s. Using a one dimensional computer code called ETFLOW, a variety of computational predictions can be made on the plasma as well as the pellet as it moves through the barrel. Using this code, different geometric configurations of the source have been simulated using an input current pulse with a current peak of approximately 20 kA. The geometries studied varied in source length and source radius. To compliment these studies, the same geometries have been simulated with different input current pulses. These input current pulses have maximum currents of 10 kA, 30 kA, and 40 kA. The results from all four current pulses are presented, and computed pellet velocities are correlated to source geometry and plasma parameters. Pellet exit velocities of up to 4.4 km/s were computed. This is an increase of 10% from previous computational studies.