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April 24, 2010

Dense Plasma Focus Fusion Status and Targets

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Eric Lerner is the driving personality behind Lawrenceville Plasma Physics who are trying to achieve commercial nuclear fusion using dense plasma focus fusion. Here are 19 pages of slides from a 2005 presentation which list the calculated energies needed for commercial net energy.

* DPF extremely economical, equipment costs ~$150,000

* Two-to-three-year, two million dollar program can accomplish next steps, test theoretical predictions, scaling laws, determine if break-even feasible (funded and doing the experiments now)
* Goal-- if break-even obtainable, DPF can produce energy output in ion beam. With inductive and electrostatic conversion, cost of energy conversion could be slashed.
* Conceptual design of DPF reactor indicates capital cost of <$200,000 for >5MW unit
* Energy costs less than 1/10 of present

Need for high efficiency of energy transfer to plasmoid:
Existing route (2005): Reduce anode radius or taper to increase speed of run-down, collapse-higher dB/dT, larger azimuthal current

Possible new (2005 route, current experiments are showing good results) route: Induce initial angular momentum with helical electrodes to generate azimutal bulk flow

Hydrogen Boron Fusion Advantages: Charged particles only, direct conversion to electric power Potential large reduction in cost of energy p + B11⇒3 He4 Only 0.2% Energy in neutrons, He4 + B11⇒n + N14

* too low energy for activation,
* no long- or medium-term radioactivity


Two Basic Challenges
1) Achieve greater than 300keV

(March 2010 experiments Since mid-month, we have increased that to 90% good shots. In addition, we have increased the current FF1 is producing at 24 kV capacitor charge from the 500-600 kA range of February to the 650-850 kA range.


Anode erosion and electron beam energy estimates of current experiments

Total magnetic energy at 0.7 MA: 5 nH, 1.2 kJ, total energy 2.4 kJ and estimated average electron energy of 140 keV. In their best shots, ion energies were measured in the range of 40-60 keV (the equivalent of 0.4-0.6 billion degrees K). The electron beam carried about 0.5 kJ of energy and the plasmoid held about 1 kJ of energy, nearly half that stored in the magnetic field of the device.

For commercial goals- they need to get about three to 3.5 times the current (MA million amps) and increase the total energy to ten to fifty times (18-80 kJ range) and a little more than double the average electron energy from 140 keV to 300+ keV. For breakeven, they need current of about 1.5 MA and energy production per pulse of about 3-4 kJ.

nτ greater than 2x10^15 sec/cm^3

2)Fusion power greater than x-ray bremsstrahlung


Business Plan and Break Even there is a copy of a Focus Fusion business plan online

Holding the final magnetic (B) field at 6GG (giga-gauss), the simulation showed that the ratio of fusion yield/gross input energy rose from 0.067% at 0.75MA to 5% at 1M to 24% at 1.5MA. This indicates the break-even point requires only a 24% fusion yield.


So a little less than double the experimental current (amperage) with a sufficiently strong magnetic field will achieve breakeven.

The net result is that for the examples studied some recovery of the x-ray energy, as well as of the ion beam energy is desirable for net energy production. The optimum case studied is for a current of 2.0 MA, cathode radius 3.3 cm, and final magnetic field 12 GG. This simulation case produced a beam that carried 97% of input energy and x-rays that carry 57% of input energy. In practical terms this means that if the beam energy recovery efficiency is 90%, which is reasonable, net energy production occurs with x-ray energy recovery rates above 22%, which is easily achievable. A 54% thermonuclear fusion yield ratio to gross input energy is expected to be the threshold for net energy production. Another practical energy-producing combination simulated used a 80% beam recovery and 80% x-ray recovery for an overall efficiency of 43%. In this example, the net electric energy production is 3.1 kJ per pulse or 3.1 MW for a 1kHz pulse rate, exceeding the planned 2 MW prototype generator.


Direct conversion of Ion Beam and X-ray Pulse to Electric Power Applications

* For power production: 80% conversion efficiency yield 49% overall efficiency of conversion of fusion energy to output power.

* UV losses minimized by greater than 1 kHz pulsing
* 5-20 MW/ electrode limited by cooling of electrodes ~ 2% total
* For space propulsion, ion beam produces thrust at 10^6 sec ISP(10,000 km/sec)
*With 80% x-ray recovery + 46% efficiency beam recovery:
* 78% energy to useful thrust
* Thrust-to-mass ratios of 0.1 N/kg, specific power of 500 kW/kg
* Six month transit time to Jupiter, 2-1 total mass/payload ratio

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