The long-awaited tungsten cathode is finally nearing completion in a Chinese factory. According to the latest reports by California-based Tungsten Heavy Powder(THP), which is performing the work in China, machining will be complete within a few weeks and delivery to LPPFusion should occur by mid-February. The 99.95% pure tungsten piece has been in the machining process for nearly two months. Because pure tungsten is as brittle as ceramic and liable to cracking, the part must be removed from machining frequently and heat-treated to relieve internal stress.
Given the extreme difficult of making the tungsten cathode, why does LPPFusion not go directly to the final beryllium electrodes? The answer is that tungsten, with its extreme resistance to heat, is the lowest risk material for the next step of our experiment. We need to eliminate evaporation of the electrode and the resulting impurities to get a jump in the density of our plasmoid, and in the resulting fusion energy output or yield. We have firm experimental evidence that tungsten does not erode under the condition FF-1 is currently running. While we have developed and published well-founded theories of how pre-ionization can stop erosion of much less heat-resistant materials like beryllium, we still need to test those theories experimentally. That we can do safely with tungsten, with risking damage to the electrodes or disappointing fusion results. In this way we will confirm or refine the theories and technique, paving the way for the beryllium electrodes.
Those beryllium electrodes will be ready when we need them. We expect to order them in January, with delivery in the first half of 2015.
LPPFusion, Inc. has made available on our website the data in ourProcessed Data Base to all researchers, both professional and amateur. This data provides the key observations for each shot from the start of operation of Focus Fusion-1 in 2009 through the end of 2013 for four instruments: the Main Rogowski coil (MRC), High Voltage Probe (HVP), the Near Time of Flight (NTF) and Far Time of Flight (FTF) detectors. This gives data on the current and voltage produced during a shot and the neutrons and x-rays emitted. We are making this data publically available in the expectation that other researchers will be able to use the data to provide new insights into the functioning of the Dense Plasma Focus device and advance the field generally.
Physics of Plasmas, the leading journal in the field of plasma physics, has published LPPFusion’s new paper on “Runaway electrons as a source of impurity and reduced fusion yield in the dense plasma focus”. The paper, by Chief Scientist Eric J. Lerner and Chief Research Officer Hamid R. Yousefi, was published online October 22, 2014 less than a month after it was submitted for peer-review. Physics of Plasmas had published a previous LPPFusion paper on record-breaking ion energies in 2012.
The new paper describes the evidence that runaway electrons are a key cause of vaporization of electrodes in the dense plasma focus device, an idea first reported on LPPFusion’s website in April of this year. Runaway electrons occur when very strong electric fields, such as in lightning bolts, accelerate electrons moving through a mainly neutral gas. If the field is strong enough the electrons gain more energy between each collision with an atom than they lose in the collision, thus speeding up to high energy.