There was work (37 page pdf) done by Jan S. Brzosko, “High Efficiency Plasma Focus: Fusion and Applications” which showed 500 repeated firings of a Dense Plasma Focus (DPF) device (H/T Culled from links at Focusfusion.org which collected this and other relevant research)
This is related to the work of Lawrenceville plasma Focus to develop cheap nuclear fusion. If they are successful, then energy costs can be lowered by 50 times from 5 cents per kwh for coal down to 0.1 cents.
A Focus Fusion reactor would produce electricity very differently. The energy from fusion reactions is released mainly in the form of a high-energy, pulsed beam of helium nuclei. Since the nuclei are electrically charged, this beam is already an electric current. All that is needed is to capture this electric energy into an electric circuit. This can be done by allowing the pulsed beam to generate electric currents in a series of coils as it passes through them. This is much the same way that a transformer works, stepping electric power down from the high voltage of a transmission line to the low voltage used in homes and factories. It is also like a particle accelerator run in reverse. Such an electrical transformation can be highly efficient, probably around 70%. What is most important is that it is exceedingly cheap and compact. The steam turbines and electrical generators are eliminated. A 5 MW Focus Fusion reactor may cost around $300,000 and produce electricity for 1/10th of a cent per kWh. This is fifty times less than current electric costs. Fuel costs will be negligible because a 5 MW plant will require only five pounds of fuel per year. [About 40 million kWh per year from a 5 MWe plant and 5 MWe is equal to 6705 horsepower]
The LPP experiment will be carried out in an experimental facility in New Jersey using a newly-built DPF device capable of reaching peak currents of more than 2 MA. The LPP power level of 2+ MA is higher than the Brzosko peak of 0.95 MA.
In a presentation to the Seventh Symposium on Current Trends in International Fusion research, in 2007, Dr. Jan Brzosko reported that in 500 shots a DPF functioning at a peak current of 0.95 MA had neutron yields that had a standard deviation of only about 15%. The experiments were preformed at DianaHitech’s laboratory in Jersey City, NJ. Unfortunately, DianaHitech no longer exists, so this experimental work is not continuing. But the results are confirmation that the DPF can run reliably.
Conclusions from the Brzosko work:
* Pulsed Power:: PF-50kJ can be build to work without failure for 107shots at 1 Hz; limiting factors: energy and life time.
*Reproducibility of pulses (yield, duration): very good.
* Electrode erosion:: not limiting factor;
* Deuterium or Tritium circulation:: not limiting factor;
* Cooling:: not limiting factor;
* Tritium/deuterium leak:: requirement for certain temperature window (for chamber).
* System ready for engineering version.
Other Related Work: Russian Pb11 from Lasers
A Russian team of researcher reported observing pB11 fusion using a laser. The yield was only about 1,000 reactions, about 7 billion-fold short of breakeven, but the experiment did show that pb11 fuel will burn more or less as expected.
The team exposed a solid target of borated plastic to a 1.5 picoseconds, 10-joule laser pulse concentrated in an area 7 microns in radius. A very thin, 0.024 micron layer was heated to an electron temperature of about 100keV and an ion temperature of 30 kegs. The confinement-time-density product was 1.1×1011, much smaller than the nearly 1014 we achieved with an ion temperature of 55 keV. However we did not use pB11 but instead used deuterium fuel.
The laser approach can not be easily scaled up to breakeven. Higher laser intensities will increase yield, relative to input energy, by only about a factor of 300 at solid densities. For breakeven, compression to densities more than 5,000 times solid density would be required. Decades of efforts on laser fusion show that such high compression is just about impossible to achieve
Other Related Work: Singapore Group Demonstrated 50% Efficient Energy Transfer to Plasmoid
A research group in Singapore, using electrodes quite similar to those proposed for the next set of focus fusion experiments, have demonstrated efficiency of energy transfer into plasmoid of at least 50%.
The energy transfer from the magnetic field in the DPF to the tiny plasmoid is a key parameter for focus fusion, since it is only in the plasmoid where the fusion reactions take place and the ion beams that carry the output energy originate. The Singapore group, whose work was reported in IEEE Transaction on Plasma Science (vol. 32, p.2227), were applying the DPF to x-ray production for lithography, but the results are relevant to fusion.
Texas A&M: One billion Degrees
Controlled fusion with advanced fuels requires average electron and ion energies above 100 keV (equivalent to 1.1 billion K) in a dense plasma. We have met this requirement and demonstrated electron and ion energies over 100 keV in a compact and inexpensive dense plasma focus device. We have achieved this in plasma “hot spots” or plasmoids that, in our best results, had a densityconfinement-
time-energy product of 5.0 x1015 keVsec/cm3, a record for any fusion experiment. We measured the electron energies with an X-ray detector instrument that demonstrated conclusively that the hard X-rays were generated by the hot spots.
Lawrenceville Plasma Physics Patent
The dense plasma focus (DPF) has been studied as a possible solution to the problem of instabilities. In this device, natural plasma instabilities are used to create confinement in a dense plasmoid, rather than being minimized as in other fusion devices. One such method and apparatus for a dense plasma focus radiation source for generating EUV radiation including a coaxially disposed anode and cathode is taught in U.S. Pat. No. 7,002,168 issued to Jacob, et al. The methods and apparatuses for enhancing the efficiency of EUV radiation production, for protecting, cooling and extending the life of the anode and cathode, for protecting and shielding collecting optics from debris and pressure disturbances in the discharge chamber, and for feeding Lithium into the discharge chamber.
Another plasma focus radiation source for generating radiation at a selected wavelength is taught in U.S. Pat. No. 6,172,324 issued to Birx, which teaches producing a high energy plasma sheathe that moves down an electrode column at high speed and is pinched at the end of the column to form a very high temperature spot. An ionizable gas introduced at the pinch can produce radiation at the desired wavelength. In order to prevent separation of the plasma sheathe from the pinch, and therefore to prolong the pinch and prevent potentially damaging restrike, a shield of a high temperature nonconducting material is positioned a selected distance from the center electrode and shaped to redirect the plasma sheathe to the center electrode, preventing separation thereof. An opening is provided in the shield to permit the desired radiation to pass substantially unimpeded
To use pB11 fuel the ion energies must be in excess of 100 KeV, simultaneously with density-confinement time products of more than 3.times.10.sup.15 particle-sec/cc. The higher atomic change, Z, of B11 greatly increases the x-ray emission rate, which is proportional to Z.sup.2 making it difficult to achieve ignition, e.g., the point at which the thermonuclear power exceeds the x-ray emission.
Using neon as the working gas, the team was able to produce as much as 140 J of x-rays from a single shot. With an outer electrode (cathode) radius of 4.7 cm and peak current of 360kA, the device had stored magnetic field energy of about 600 J. Since the electron beam generated by the plasmoid provides the heat for the electrons and thus for the x-rays, e-beam energy must be at least 140 J. Total energy in the plasmoid is twice the electron beam energy (the ions carry the same energy) so total plasmoid energy must exceed 280 J, or very nearly half the magnetic field energy.
The device used an anode with a base radius of 1.6 cm, tapering at the end to 1 cm. These dimensions are quite similar to those we plan to use for the copper electrodes on the next set of experiments, and add to the evidence that we will be able to achieve a high efficiency.
The present invention also provides a plasma generator to enable nuclear fusion that includes an anode and a cathode positioned coaxially and at least partially within a reaction chamber. The anode has an anode radius and the cathode has a cathode radius that imparts a high magnetic field. Generally, the anode radius is between about 0.25 cm and about 1.5 cm times the peak current measured in mega-amperes in the device and the cathode radius is between about 0.5 cm and about 3 cm times the peak current measured in mega-amperes in the device.
Nextbigfuture focus fusion category of articles
Eric Lerner, Lawrenceville Plasma Physics, Google Talk 64 minutes