LPP Fusion explains why Tungsten and Beryllium electrodes for their dense plasma fusion reactor work

The LPP Fusion research team is still working with the tungsten electrodes but they know the beryllium electrodes will be needed soon. Tungsten is being used now because of its extreme resistance to the heat generated by runaway electrons during the early stages of FF-1’s pulse. They are combining that thermal resistance with a technique called “pre-ionization” to prevent vaporization of the electrodes and the resulting impurities in the plasma (see earlier report here.) This, they expect, will greatly increase the density of the tiny plasmoid the device produces and thus the fusion energy yield.

If LPP Fusion is successful they could reduce the cost of energy to 10-20 times.

Two cylinders of nearly pure beryllium metal were delivered to LPPFusion’s Middlesex, NJ lab on January 14. The cylinders, weighing together 35 kg, are to be machined over the next five months into two anodes and a cathode for experiments in the second half of 2016. They were fabricated from 97.8% pure beryllium at the Ulba Metallurgical Plant in Kazakhstan. The two anodes will be machined in California and the cathode in Massachusetts, after acceptance testing for purity and strength, which were guaranteed by Ulba.

The Beryllium cylinders

As the plasma density increases, so will the intensity of the x-ray pulse emitted by the plasmoid. In tungsten, the x-rays will be absorbed in the outermost micron of the metal. When they are strong enough, the x-rays will start to vaporize even tungsten. Before we reach that point, LPP Fusion wants to switch to beryllium. Beryllium, a far lighter metal with only four electrons per atom, is almost transparent to x-rays. What x-rays beryllium does absorb will be spread out harmlessly throughout the bulk of the electrodes.

Tungsten electrode pictures

LPP Fusion did not want to use beryllium first because they need to test and perfect the pre-ionization technique on the tougher tungsten. Beryllium is much less resistant to the runaway electrons than tungsten. Once they get the pre-ionization to work well, we’ll test it further using a silver-coated electrode to simulate the less thermally resistant beryllium. Then they can switch to beryllium.

They have to be sure that the beryllium will not significantly erode because vaporized beryllium could recondense as beryllium dust. While bulk beryllium is harmless, beryllium dust is dangerous. If inhaled in air at above 0.1 parts per billion, it can set off an immune reaction that leads to serious or fatal lung disease. By comparison, the decaborane fuel we will be using later this year is harmful only at concentrations in air of 50 ppb, 500 times as much as beryllium dust. As a result, the beryllium is being machined at specialized facilities with high levels of safety protections. Because of this safety hazard LPPFusion will have to use special precautions, including a sealed glove box, if they do anything to the electrodes that could create dust. However, with tests to ensure no dust is produced, careful monitoring and careful safety procedures, we will be able to ensure our own safety around the beryllium.

Since only 400 tons of beryllium is currently produced world-wide, some of the LPP Fusion newsletter readers have asked if supplies will be adequate for production of millions of focus fusion generators. In fact, beryllium is as abundant in the Earth’s crust as lead, whose global production is 4 million tons per year. Beryllium production at the moment is limited by low demand, and strict regulations relating to its use in fission reactors and nuclear weapons. As focus fusion production gears up, it will be technically easy to ramp beryllium production up to the roughly 40,000 tons per year needed. Changes to regulations should also be possible, as focus fusion generators would make fission power obsolete and could lead to the cessation of uranium production, firmly closing the door to more nuclear weapons and obviating the need for controlling beryllium.

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The key to LPP Fusion progress is taking shots with our machine, Focus Fusion-1 or FF-1 for short, which gives us the experimental data to test our theories and demonstrate progress towards net energy. We estimate that to accomplish net energy demonstration we have to do 1,500 more shots. So far they have carried out 1,900 shots. Each shot costs us about $900.

For $75 you can fund the charging of one of their 12 capacitors for one shot, for $150, two capacitors and so on up to $900 for a full shot. Everyone who funds a given shot will be recognized in a list kept permanently on the website.