Tungsten Anode Goes Into FF-1; Aluminum Cathode Model Is CheckedOctober 22, 2014
October 10, LPPFusion team members Eric Lerner, Hamid Yousefi and Tony Ellis lifted the tungsten anode into place on top of the FF-1 dense plasma focus experimental device (figure 1). The anode had previously been attached to its steel connecting plate (see September report) and was temporarily attached to a metal carrying rod for insertion through the Mylar insulating layers. It was then unbolted form the rod and the steel connecting plate was carefully aligned and bolted to the upper outer bus plate, connecting it into the FF-1 main circuit.
Figure 1. The new monolithic tungsten anode rests inside FF-1.Its base is surrounded by the insulating layers of Mylar that will keep the current from shorting out to the cathode, to be mounted below it.
The same week, Lerner and Yousefi carefully measured an aluminum model (Figure 2) shipped to us by Tungsten Heavy Powder, the firm producing the tungsten cathode. Due to the cathode’s complexity, THP wanted us to check the aluminum model before cutting the tungsten piece. Sure enough, a few errors were found, including excessive variation in the distance between the vanes that will carry the current filaments. THP has estimated that higher accuracy will be obtained only with slower cutting of the tungsten. This will unfortunately lead to a further two- or three- month delay in our long-delayed tungsten cathode. However, it will be worth the wait to ensure the symmetry needed for good compression of the plasma and the high density we are aiming for.
Figure 2. The shape of things to come: the aluminum model of the monolithic cathode (silvery object with numbered vanes) surrounds that actual tungsten monolithic anode before it is mounted on FF-1. Aside from the silvery color of the aluminum, this is what the finished electrodes will look like. The inner ring of holes is part of the vacuum flange that will form part of the vacuum chamber wall. The outer ring of holes is for the bolts that will connect the cathode into the FF-1 circuit. Since both electrodes will be connected outside the chamber, no arcing can contaminate the plasma.