 Loomis and DuBridge recruited physicists for the new laboratory at an Applied Nuclear Physics conference at MIT in October 1940 . Among those who volunteered was Rabi . His assignment was to study the magnetron , which was so secret that it had to be kept in a safe . The Radiation Laboratory scientists set their sights on producing a microwave radar set by 6 January 1941 , and having a prototype installed in a Douglas A @-@ 20 Havoc by March . This was done ; the technological obstacles were gradually overcome , and a working microwave radar set was produced . The magnetron was developed to permit a reduction in wavelength from 150 cm to 10 cm , and then to 3 cm . The laboratory went on to develop air @-@ to @-@ surface radar to detect submarines , the SCR @-@ 584 radar for fire control , and LORAN , a long @-@ range radio navigation system . At Rabi 's instigation , a branch of the Radiation Laboratory was located at Columbia , with Rabi in charge . 
