Singapore DPF group demonstrates high efficiency
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.
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.