Experimental demonstration of a new radiation mechanism: emission by an oscillating, accelerated, superluminal polarization current

摘要

We describe the experimental implementation of a superluminal ({\it i.e.}faster than light {\it in vacuo}) polarization current distribution that bothoscillates and undergoes centripetal acceleration. Theoretical treatments leadone to expect that the radiation emitted from each volume element of such apolarization current will comprise a \v{C}erenkov-like envelope with two sheetsthat meet along a cusp. The emission from the experimental machine is in goodagreement with these expectations, the combined effect of the volume elementsleading to tightly-defined beams of a well-defined geometry, determined by thesource speed and trajectory. In addition, over a restricted range of angles, wedetect the presence of cusps in the emitted radiation. These are due to thedetection over a short time period (in the laboratory frame) of radiationemitted over a considerably longer period of source time. Consequently, theintensity of the radiation at these angles was observed to decline more slowlywith increasing distance from the source than would the emission from aconventional antenna. The angular distribution of the emitted radiation and theproperties associated with the cusps are in good {\it quantitative} agreementwith theoretical models of superluminal sources once the effect of reflectionsfrom the earth's surface are taken into account.