Anisotropy measurements as evidence for plasmoid

Posted by Rezwan on Feb 10, 2011 at 03:41 PM
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The whole report as a pdf

As detailed in last month’s report and our press release, it is extremely important to resolve the debate of where the fusion reactions in a DPF mainly occur—in the plasmoid or in an unconfined beam. We now have even stronger evidence for the plasmoid hypothesis.

For over a month, LPP researchers have been collecting neutron measurements from bubble detectors located at three locations near the axis of the device—one 12.5 degrees from the axis, 28.5 cm from the anode, and two at 128 cm from the anode, at the end of the drift tube, one on axis, and the other 4 degrees from the axis. New analysis of the data showed that the neutron flux per unit solid angle was double the rate observed perpendicular to the axis for the two detectors at 128 cm. But it was exactly the same as the horizontal measurement (no anisotropy) for the detector at 28.5 degrees.

This pattern has been repeated over many shots, including shot 01241103, the shot with the good plasmoid image. This is particularly significant as this shot also had a record 180 keV average ion energy as measured with our time-of-flight detectors.

If any large fraction of the neutrons had been produced by a beam, the 12.5-degree detector would have had a significantly increased neutron flux, as the cross section for neutron emission is over three times grater in the direction of the beam than perpendicular to it. So this alone is strong evidence against a beam target as the main mechanism—rather it is the energetic confined ions that are producing the reactions.

How do the far detectors get a large neutron dose? If even a small fraction of a beam penetrates all the way down the drift tube, fusion reactions generated in the background gas will be far closer to the detectors than is the plasmoid. In this case, the flux per unit area, which we are measuring, will be greatly intensified, as it increases inversely with the square of the distance. A beam generating only few percent of the total neutrons observed could double the flux at the end of the drift tube, producing the results observed.