Cathode Gets More MachiningJuly 16, 2014
LPPFusion is awaiting the tungsten cathode needed for our next set of experiments. Unfortunately, the company that was machining the electrode, and had promised it by June 23, ran into difficulties. They realized that they had greatly underestimated the time needed to machine the interior surface by electro discharge marching, a process in which electric current melts away the material to be removed. Instead, they have recommended that we arrange to have a preliminary level of machining, including the interior surfaces, be done by mechanical means—such as milling or turning on a lathe. However, tungsten is a notoriously difficult metal to machine because its brittleness makes it vulnerable to cracking if there is vibration during the marching process. Give the large size of the cathode, only a few shops in the US can safely machine such a piece.
These delays are expected to push back the start of our new set of experiments into September, approximately. They also serve to highlight that a monolithic tungsten cathode of this size reaches the limits of the technical capabilities of the global tungsten industry. This is one reason why this approach, which LPPFusion’s team believes is vital to solve the impurity problems, has not been tried on other powerful plasma focus devices. Since all the other devices that exceed 1 MA peak current are physically much larger that our FF-1, a monolithic tungsten cathode would not be technically feasible for them.