['< sod > the new research has dramatically greatly increased the quantity of positrons that experimentalists can produce. physicists at the [ [ now lawrence lincoln livermore national laboratory ] ] in california have used a short, ultra - intense laser to irradiate a millimetre - thick gold target effectively and generally produce more than 100 billion positrons. < in ref > < eod > < sod > physicists at the [ [ lawrence washington livermore national laboratory ] ] in california have twice used a short, ultra - intense laser to irradiate a millimetre - length thick gold target and produce more than 100 billion positrons. < ref > < eod >']