New Calibration Confirms FF-1’s High Fusion Yields


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Posted by Lerner on Jun 10, 2010 at 12:44 AM
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Tests in early June have confirmed that FF-1 is producing higher fusion yields than have been achieved with any other DPF at the same peak current.

The new tests were calibrated with LPP’s silver activation detector and our new commercially-purchased bubble detectors, which had been calibrated to within 25% accuracy by the manufacturer, BTI.  The bubble detectors are small tubes of a liquid that is above its boiling point at the pressure in the tube. The interaction of neutrons with charged particles in the liquid creates a nucleation seed for a bubble of vapor to form.  Counting the bubbles gives an excellent measure of the number of neutrons generated.

In our tests, two calibration shots were taken so far.  Since we were only using four capacitors (see switch section below), we did not expect a lot of neutrons and placed the bubble detectors directly on the outside of the vacuum chamber.  We then compared the neutrons count derived from the calibrated bubble detector with that derived from our silver activation counter, which was built to the same specifications as a design which had been calibrated by other scientists 20 years ago.  The agreement was excellent, well with the 25% accuracy of the bubble detector.  (A technical report on the calibration will be sent out shortly.)

We can now confidently use our previous measurements of neutron yields to compare our results with those of other DPF devices.  Figure 1 shows two of the best shots from FF-1 (red dots) compared with the best shots for all non-LPP DPFs (blue dots).  The FF-1 results are as much as a factor of ten above the other results and show a sharper increase with higher current. The green dot shows LPP results from 1994, which also lie above the main body of results.

Figure 1.  Neutron yield in various DPFs in world.  Derived from J.O. Pouzo, M.M. Milano in Current Trends in International Fusion Research:  Proceedings of Fourth Symposiium.  NRC Canada pp 33.  (2007)

We cannot say for sure yet if this improvement in performance is due to our use of the Axial Field Coil or to the small radius of our electrodes or both.  Further experiments are needed to determine this.

The calibration also allows us to confidently chart our own progress so far in 2010 (achieved yield).  Figure 2 shows the increase of fusion yield from FF-1 so far this year.  Each point represents a new “record” for FF-1 yield.  The figure shows that we have traveled a bit less than half way to our goal of demonstrating scientific feasibility which would involve a yield of 10,000 to 100,000 joules. If we can continue at the rate of progress of the spring, we should reach our goal by year-end.

Figure 2.  LPP’s past and planned energy yield per shot in joules.

 


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This sounds like excellent news. 

But I wonder if there could be further clarification—what exactly does it mean when talking of the “goal ... of scientific feasibility”?  Does that mean breakeven?


AaronB's avatar

Short answer: yes.
Long answer: Breakeven is a complicated word. Phase 1 is where we attempt to demonstrate at least as much fusion energy production than electrical energy input, or breakeven. We hope to reach this point by the end of the year. Phase 2 is where we do the engineering to capture that output energy in the most efficient way possible to reach positive net energy. This is where we will work on the “onion” to capture X-rays and the ion-beam capture coil and switch. We will also work on rapid firing of the device using the captured energy from the last shot. The subsystems to remove waste heat, injecting new fuel, etc, will be attached at that point. The goal of Phase 2 is positive net energy output, which is a form of breakeven after taking into account subsystem losses. Phase 3 then turns these laboratory-based systems into refined, customer-ready, prepackaged, deliverable, commercial fusion generators. The goal of Phase 3 is positive net cash flow, which is yet another form of breakeven.


Aeronaut's avatar

Has any design work been done for Phase 2 yet?


Will Phase 1 breakeven involve pB11 fuel?


AaronB's avatar

Aeronaut, we’re working on basic Phase 1-stage electrode design and construction at this point, and recently de-magnetized the vacuum chamber after its unintentional magnetization, so Phase 2 design work is still on the far distant horizon. However, the future comes quickly, and we do discuss it occasionally.

Tulse, Phase 1 does involve pB11. It is part of our 8 goals, as explained here: http://focusfusion.org/index.php/site/article/lpp_experiment_8_goals_and_timeline/
We’ve almost achieved #5 of the 8 goals, and using pB11 fuel is part of goals #7 and #8.


Ivy Matt's avatar

If the FF-1 capacitor bank holds about 100,000 joules, per the latest milestone update, shouldn’t demonstrating scientific feasibility involve a fusion yield of at least 100,000 joules?


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