FF-1 resumed firing on April 11 after a bake-out that had removed the vast majority of the oxygen in the device’s vacuum chamber. Unfortunately, three unforeseen circumstances increased impurities far above their plans.
1. a leaky valve introduced about 100 mg of water vapor into the chamber right before the first shot, creating a thin layer of oxides.
2. some oxides may have been formed during the heating phase of the bake-out itself, due to a somewhat too rapid rise in temperature.
3. their initial effort at preionization by small pulses of current itself eroded tiny particles from the tungsten anode, allowing them to vaporize into the plasma.
Despite this rocky start, the LPPF research team had reason for optimism. The oxide layer was clearly much thinner than that which we dealt with in 2015, before their bake-out. Then, the layer was iopaque to light and the golden color of tungsten bronze, indicating a thickness of at least one micron. But in April, the layer’s color ran in a spectrum from red to violet, indicating interference coloring like that of a soap bubble, and thus a thickness of less than about 0.3 microns, or about 100 mg of oxygen.
Even more important, they could anticipate that FF-1 would be self-cleaning in its current configuration. When fired, the device’s hot plasma would vaporize the oxide layer, breaking up the molecules and releasing free oxygen. Some of that oxygen would be trapped in the titanium nitride coating that we had added to the chamber surface, and bonded too tightly to be released in future shots. Another part of the oxygen would combine with the deuterium gas filling the chamber, becoming water vapor, which could then be pumped out. In that way, the oxides would be reduced shot by shot.
As they fired, they saw clear evidence of this cleaning effect, as the pressure “pop” after each shot, measuring how much oxygen was released, steadily declined by about 10% per shot. We also observed the fading of the colored deposits and the reduction of tungsten bands in the optical spectra for the plasma.
To improve preionization, they switched, on the suggestion of LPPFusion Research Physicist Dr. Syed Hassan, to a gentler method: a glow discharge. The aim of preionization is to create an electron “traffic jam”—enough free electrons before the main pulses, so that the electrons will move slowly and have too little energy to vaporize the anode when they enter it. While in an arc discharge, a medium current—about 100 amps—is suddenly discharged to create the free electrons, in a glow discharge a much smaller current, of about 40 microamps, flows continuously through the gas. Which type takes place depends on how much current is supplied in the preionization phase that precedes a FF-1 shot. Again they saw clear visual evidence that the glow discharge did not create new dust and allowed the shots to smooth away the erosion previously created.
After April 26, fusion yield started an accelerating rise, shot by shot. They still had too much impurity to run well with our planned nitrogen-deuterium mix. (The tungsten impurities combined with the nitrogen require too much ionization energy to strip off all their electrons during the compression phase of the shot, preventing even compression.) So we switched to pure deuterium. From May 11 to May 18, fusion yield doubled, and then doubled again.
As fusion yield rose, they got several additional indications that with fewer impurities, compression was more symmetrical.
These shots are a record not just for LPP Fusion. For all researchers working with this type of device, a dense plasma focus or DPF, their May 23 shot is 50% more than any previous shot at this peak current of 1.1 MA (million amps) and double the previous record for their total input energy of 60 kJ. This is important, as this shows they are moving back towards the steep scaling law that predicts energy increasing as the fourth power of the peak current. In previous work, this scaling curve has leveled off for current over 1 MA.
With much of that maintenance out of the way, they hope to get closer to 100 shots per month. In addition, in the past week, as they moved to lower fill pressures, the preionization discharge stopped working correctly. they will adjust the preionization current next week and monitor it more closely to ensure optimal function. They expect that this change, in addition to further self-cleaning, will again increase yield.
They plotted the latest published results of various fusion experiments. Right now the best plasmas have been obtained with the new Chinese tokamak experiment, EAST, and the giant US laser facility NIF. In a second group, about a factor of ten lower, is the new German stellarator W7X, the JET tokamak in the UK and the LPP fusion's own FF-1 in fifth place. Spread out a factor of hundreds to thousands below the second group are the other privately financed efforts, EMC2, Tri Alpha and General Fusion. These efforts are much better funded than FF-1 but at the moment have far cooler and less dense plasmas.
A better way to look at overall performance of these various devices is what is called ”wall-plug efficiency”—the ratio of the fusion output to the total energy put into the machine from the grid (the “wall plug.”) This combines how good the plasma is at producing fusion yield with how good the device is in getting energy into the plasma. For consistency we are comparing only results running with deuterium as a fuel, not the much more reactive deuterium-tritium mix.
Here the picture is different. The other private efforts drop out, as they don’t have measurable fusion yield from their machines (or in the case of EMC2 have not published any). NIF drops back to 4th place, because its lasers are extremely inefficient in converting input energy into plasma energy. FF-1 moves up to second place, nipping at the heels of JET, and EAST is in third, right behind FF-1. This is in part due to FF-1’s high efficiency in coupling electrical input into the plasmoid that produces the fusion.
Here is the full experiment project plan in planned test firings.
Summary of Lawrenceville Plasma Physics
LPP have their Tungsten electrode and then later switch to a berrylium electrode.
If successful with their research and then commercialization they will achieve commercial nuclear fusion at the cost of $400,000-1 million for a 5 megawatt generator that would produce power for about 0.3 cents per kwh instead of 6 cents per kwh for coal and natural gas.
LPP’s mission is the development of a new environmentally safe, clean, cheap and unlimited energy source based on hydrogen-boron fusion and the dense plasma focus device, a combination we call Focus Fusion.
This work was initially funded by NASA’s Jet Propulsion Laboratory and is now backed by over forty private investors including the Abell Foundation of Baltimore. LPP’s patented technology and peer-reviewed science are guiding the design of this technology for this virtually unlimited source of clean energy that can be significantly cheaper than any other energy sources currently in use. Non-exclusive licenses to government agencies and manufacturing partners will aim to ensure rapid adoption of Focus Fusion generators as the primary source of electrical power worldwide.
SOURCE - LPP Fusion