Lawrenceville Plasma Physics November update on Nuclear Fusion project

Summary of the November update on the Focus Fusion project:

* Two tests indicate that a new design for a Tungsten component should succeed in solving current inpurity problems
* Pinch timing measures impurities and sparks international project
* Laser experiment gives new visibility to pB11 fusion
* Italian physicist analyses Focus Fusion, sees promise
* Motherboard features LPP’s role in fusion race

New laboratory tests on the existing tungsten plate in FF-1’s (Focus Fusion-1 is the prototype fusion machine) cathode (outer electrode) have increased LPP (Lawrenceville Plasma Physics) researchers’ confidence that the planned all-tungsten electrodes will both cure the impurity problem and survive many shots. In the first test, the LPP team measured how much erosion had occurred on the tips of the tungsten teeth where the current starts to flow. These tips suffer from the highest erosion of any parts of the cathode, because of the high concentration of current to which they are exposed. The team compared enlargements of photographs of the tip of the teeth taken when the plate was first installed in November, 2012, with photographs taken this month, after some 340 shots had been fired.

Photos of several different teeth failed to show any measurable erosion. If erosion from the anode is approximately as great, an upper limit on total impurity from the tungsten amounts to only about one tungsten ion for every 8,000 deuterium ions, well within the limits that LPP has calculated will be acceptable and have no significant effect on the plasma’s properties. By contrast, the present silver-plated copper electrodes erode so rapidly that there is about one impurity ion for every 50-70 deuterium ions. So the tungsten electrode is expected to lead to a 100-fold drop in impurity levels.

A second test was to see if the tungsten plate suffered small-scale microcracks due to the thermal shock of being heated suddenly by the plasma. To increase the total energy that the tungsten was exposed to, the LPP team attached four more capacitors to the FF-1 circuit, bringing it back up to the maximum of 12 capacitors. We fired four shots at 35 kV and then disassembled the electrodes. We observed no microcracking. Others’ research with tungsten has shown that microcracking either starts in the first few shots, or is postponed for several hundred shots. So
this test is also encouraging. However, we will soon do another round of tests at 40 kV, close to the 45 kV maximum power of FF-1.

We have now received a bid on the manufacture of our tungsten electrodes, so we expect to have them in hand by February, 2014, assuming adequate finances.

What caused the impurities to suddenly turn up? At that time, improvements in switch functioning were increasing FF-1’s current. When current density (current per unit area) passed a critical threshold, around 2 MA/cm2, electrode evaporation started to occur, releasing the impurities

Analysis of past pulses showed that “short pulses”, which we now understand were those without large impurities, had ten times the fusion yields of the “long pulses” which did have impurities.

While FF-1 is still some steps away from switching to pB11 fuel, other approaches are proving the reality of hydrogen-boron fusion, which produces no neutrons in the main reaction and no radioactive waste. In a report published in Nature Communications and summarized in an October news item, a French and American team of researchers announced that they had succeed in increasing the fusion yield in a laser-driven pB11 experiment about 100,000-fold from earlier experiments in 2009. While the yield of about 0.3 millijoules was small compared with the 400 J of laser energy delivered and even smaller compared with the energy needed to drive the lasers, it was a step towards demonstrating the potential for pB11 fusion energy, and the publication in Nature Communications gave some needed visibility to aneutronic fuels.

My [Brian Wang] interview with Motherboard was included as well. The quote where I discuss that if Lawrenceville Plasma Physics can succeed that they could reduce the cost of energy to 0.1 cents per kilowatt and change the world be reducing the cost of energy by 10-50 times.

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