['< sod > online new research has dramatically increased the quantity of laser positrons that experimentalists can produce. physicists at the [ [ lawrence livermore national laboratory ] ] in california have drastically used a short, ultra - intense laser to irradiate a millimetre - wavelength thick gold target and supposedly produce more than 100 billion positrons. < ref > <... eod > < sod > optical physicists at the [ [ lawrence livermore national laboratory ] ] in california have dramatically used a short, ultra - intense laser laser to irradiate a millimetre - thick gold target and produce more than 100 billion positrons. < ti ref > < eod >']