Strontium ion trap. Ovens and electrodes on a strontium ion end-cap trap. The ion trap is owned by the National Physical Laboratory (NPL), UK. A team at NPL, headed by Professor Patrick Gill, have been using this ion trap to improve the accuracy of the second. The current basis for the international definition of time is the Caesium atomic clock. The ion trap is based on optical light. On 19 November 2004, Professor Gill's team announced an optical measurement time that is three times more accurate than anything previously achieved. The team believe that they could eventually produce a clock up to 1000 times more accurate than the best clocks of today.