A high resolution plasmoid image

Posted by Rezwan on Feb 10, 2011 at 02:43 AM
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The whole report as a pdf

Note, this post refers to “the second piece of evidence.”  The “first piece” is described here.

The second piece of evidence for high-efficiency energy transfer into the plasmoid and then into the beam is from the ICCD image we obtained Jan. 24 of a fully-formed plasmoid. We believe this is the highest-resolution image of a DPF plasmoid ever achieved, with a spatial resolution of 30 microns and a time resolution of 200 ps (Figure 3). As with the beam shot, there are a number of things to note about this image, in addition to our energy calculations.

First, the image clearly shows the tightly coiled core of the plasmoid, closely resembling the coil of a telephone cord (for those of you still with landlines!) This confirms our basic model of the kinking of the pinched filament to form the plasmoid. Also note the fainter filaments in the outer parts of the plasmoid looping around to connect one end of the core with the other.

Second, we can see from the lack of motion-blurring that the plasmoid is moving fairly slowly, less than a pixel (or 30 microns) during the 200 ps exposure. This works out to 15 cm/microsec, not much faster than the speed of the current sheath. So any angular momentum in the plasmoid—which may be considerable—is confined to the motion of ions along the coiled filaments, and not to the motion of the filaments themselves.

Third, the size of the plasmoid core is measurable from the image as 180 microns in radius and 2 mm in length. On the one hand, this shows considerable compression from the kinking filament stage that we imaged back in October, which was 500 microns in radius and 3 mm in length. On the other hand, this is still considerably larger, by a factor of 3, than the dimensions our theory predicts for the plasmoid.

From the spacing of the helical coils and the volume of the plasmoid core in this shot, we can determine that the inductance of the plasmoid is 8.5 nH, which is two-thirds that of the kinking filament in the October shot. With the peak current of 1 MA, this would mean a magnetic energy in the plasmoid of 4.2 kJ, and a total energy, assuming equal kinetic energy, of 8.4 kJ. So for this shot 01241103, producing a fusion yield similar to that of 01121103 discussed above—0.7x1011 neutrons—we again have evidence that about a quarter of the energy available at the time of the pinch is transferred into the plasmoid. Of course, there is still room for a factor of four improvement, but this relatively high efficiency is very encouraging.