This article outlines the next few steps in the development of the Focus Fusion energy experiment. We are not really a long ways from success and the design lends itself to stability even as the input climbs.
I also think that larger more robust systems could simply work better. I may be wrong, but with energy feeding into the central core, all advantage goes to larger design elements.
In the meantime we have a test platform that is a clear evolution from previous work in the area. The does feel like evolution of design will work and should be fully supported.
How Will We Get There From Here?
FFI (Focus Fusion 1), LPP’s experimental device, has achieved higher fusion yields than have been achieved with any other DPF at the same peak current.
Though remarkable, this yield is still 5 orders of magnitude short of the fusion yield required to prove scientific feasibility of focus fusion. How does the team hope to make up the difference?
Step by experimental step: stairway to fusion
How will LPP go from their current 1/12 of a Joule of fusion energy to 33,000 Joules of fusion energy?
Figure 1 depicts LPP’s past and planned fusion yields per shot in Joules. The team will need to get over 10,000 Joules per shot to demonstrate scientific feasibility of net energy production. Their theory predicts that they may ultimately get as high as ~33,000 Joules per shot. (”~” means “approximately”. Pointing this out because if the font is small, it looks like a minus sign.)
Figure 1. LPP’s past and planned fusion energy yields per shot in Joules
The pink points in the chart above correspond to yields actually achieved so far.
The blue points correspond to LPP’s goals based on the theories they are testing.
This is a simplified representation of what LPP plans to do, and should give a rough idea of the jump in yield for each experimental stage. The time given for each step is also an estimate. Things don’t always go smoothly as we know from the switch delays.
Research parameters and anticipated yields
Each of the blue points in Figure 1 is plotted based on the theories being tested by the LPP experiment. Figure 2 below shows the variables that are expected to cause an increase in the fusion yield (left column), and the factors by which the yield is expected to increase (right column).
Factor of increase
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Scaling with increased current, I^5 scaling to 1.4 MA
Scaling with increased current, I^4 scaling from 1.4 MA to 2.8 MA
Optimization of axial magnetic field
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Change in fuel to pB11:
Increase in energy yield per reaction pB11 vs. DD
Increase in reaction rate pB11@600keV vs. DD@100 Kev
Additional compression for pB11
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Total increase expected
Ultimate fusion yield
Figure 2. Variable/cause and corresponding factor of increase
The points in Figure 1 were obtained by taking LPP’s recent yield and multiplying by the factors at each step of the way. Multiplying the factors gives an expected increase of 422,000 times. Taking the current level of ~1/12 of a Joule that LPP has achieved and multiplying it by 422,000 yield gives us ~33,000. If all goes well, the experiment will validate this theory and follow the points.
Theoretical basis for anticipated yield
The first two variables in Figure 2 above (increasing current) are based on LPP’s theory, but they are backed up by extensive experiment . So far, LPP has been achieving much faster scaling, almost I^7.
The third item (optimization of axial magnetic field) is also based on LPP’s theory, but requires experimental verification.
For changing the fuel to pB11, the first two variables LPP is certain of, and are based on well-established measurements by others.
The third item (additional compression for pB11 with a DPF) is also based on LPP’s theory, which has to be experimentally verified.
Why are 10,000 Joules required for scientific feasibilitiy?
As noted, we need at least 10,000 Joules per shot. The team hopes that they will ultimately get ~33,000 Joules per shot and that this will demonstrate scientific feasibility of net energy production with this device and pB11 fuel.
The 33,000 Joule yield was derived based on the idea of firing at full capacity for a capacitor bank of 100,000 Joules.
Some of you may be wondering why a yield of 33,000 Joules from a shot of 100,000 Joules represents scientific feasibility. Doesn’t that indicate a loss of 67,000 Joules?
33,000 Joules is the “fusion energy yield”. This is how much additional energy comes into the system from fusion reactions. This means you start with 100,000 Joules and you get a yield of ~33,000 Joules of fusion energy. Well then – that means you now have 133,000 Joules, right? Sounds like a 33% increase in energy! Net energy and beyond! Sounds like you can afford to lose an order of magnitude. After all, 103,000 Joules would be 3,000 Joules of net energy, no?
Sadly, no. Energy is lost to inefficiencies. The goal for fusion yield has to be high enough to make up for losses of the system. Assuming 80% efficiency, (80% x 133,000 Joules) gives you 106,400 Joules – 6,400 Joules of net energy. Electric energy recovery efficiency is a variable that can be increased to a certain extent by more careful engineering.
It was stated above that scientific feasibility could be had with a minimum of 10,000 Joules of fusion yield. 10,000 joules would require a system efficiency of at least 91%.
Here is the hypothetical sequence
[Volunteers required to animate this]
· A shot is fired.
· An initial current of 100,000 Joules enters the system.
· About 70,000 go toward generating the “pinch” and making fusion happen.
· The other 30,000 are not lost. They are recovered/recycled – stored in a second capacitor bank called the mirror capacitors that is charging up for the next shot.
· The 70,000 Joules in the pinch will theoretically yield 33,000 Joules of fusion-generated energy.
· 70,000 + 33,000 gives us 103,000 Joules of energy to be recovered in the ion beam conversion device. 103,000 Joules from the ion beam conversion device + 30,000 recovered from the shot gives us 133,000 Joules.
· Less ~20% energy lost by inefficiencies and you end up with the 106,400 Joules.
· And, of course, “your mileage may vary”.
“Scientific feasibility of net energy production” vs. “net energy”
This phase of the LPP experiment measures “fusion yields,” not “net energy”.
We speak of “scientific feasibility of net energy production” and not “net energy” because the experiment will demonstrate if net energy is feasible, without actually generating net energy.
The shots LPP fires do not need to produce net energy. All they need is fusion energy that is a big enough fraction of our total input – over 10% and probably 30%, depending on recovery efficiency.
“Net energy” itself awaits Phase II, the prototype reactor phase, in which a team of engineers determines how to recover energy and crank up the efficiency. And of course, this all depends on the success of this Phase I – proof of concept. Stay tuned!