harvesting positrons

in the last blog, i mentioned briefly the idea of using anti matter as fuel. Positrons are an antimatter form of an electron. the only difference is that it is positively charged opposed to negatively charged. there are conventional methods to containing these, which include combining them with anti neutrons and anti protons making anti atoms and molecules. since these have a charge, containment is made possible with electromagnetic fields which keep them all together. Harvesting positrons is harder to do. since there are far fewer of these in the universe then electrons, harvesting is a lot like drilling for oil or separating the H3O compounds from H2O. One man by the name of James Bickford of Draper Laboratory (Cambridge, MA), believes that if we use a wire net like device with positively charged outer layers will deflect protons and attract anti-protons and positrons. It is estimated that at any given time there is 10 mg of positrons in the earths atmosphere but much more then that exist in the jovian planets. It would seem that in order to pursue the idea of anti-matter for interstellar travel we still have to make it to the other planets. I guess anti-matter will have to wait and we will have to depend on fusion and space sails to get us to the other planets first.