Dense Plasma Focus Controlled by Plasma and Gas Injection

Dense plasma focus (DPF) is a pulsed power plasma device in which the pinch is formed at the end of a cylindrical anode. Usually DPFs are filled with gas and the plasma parameters can only be controlled by the pressure of this gas fill. NRL DPF experiments explored the alternative - local plasma and gas injection into the DPF device, which prevents breakdown and short-circuiting of the generator at later times. Such injection gives a bigger control over implosion timing, independent of the device geometry. This will allow quick finetuning during the run of the experiment. In a series of MHD simulations using the Athena code, we study how different types of plasma and gas injection affect the implosion. For example, one may inject a plasma column perpendicular to the axis or at an angle, to counteract inhomogeneity of the jxB force. While injecting less gas, this produces longer delay times before the implosion as well as the different location for the implosion. Injecting the gas along the axis allows control of pinch density that is almost independent of the implosion time.