Simulation of FRC formation and capture as a design tool

Abstract

Summary form only given. Over the next three to five years, Los Alamos National Laboratory (LANL) and the U. S. Air Force Research Laboratory (AFRL) will form, translate, capture, and compress a field reversed configuration (FRC) of magnetized deuterium plasma using an imploding solid liner to achieve magnetic fields more than a million times that of the Earth and plasma pressures of one million atmospheres. These experiments require two pulsed power events before FRC compression: formation of the FRC and its translation to and capture in a collapsing magnetic cavity. Though the FRC must be robust enough to have a long lifetime and yet be small enough to translate quickly and to enter the collapsing magnetic cavity, its formation is a relatively well-behaved process.However, its translation and capture is at best a balancing act. The mirror field at the liner entrance must be small enough to allow the FRC to enter, and that at the exit must be large enough to reflect it back, after which the entrance mirror field must be large enough to keep it from bouncing back out again. This is complicated by the fact that the liner implosion will begin before FRC formation in order for the FRC to last through compression. Hence, the relevant mirror fields are dynamically created by partial liner compression. Working in close coordination with the electromechanical design team, NumerEx has performed integrated simulations of the FRC formation, translation, capture and compression to aid in the choice of field strengths, coil placement, and timing. We will describe this process by showing simulations of successful and unsuccessful designs. We will also describe improvements we made to our models to increase their fidelity and flexibility, so that as new coil designs and experimental measurements of translation and mirror fields have become available, we could quickly incorporate them.