An investigation has been made of the possibility of using an oxide‐coated cathode as an electron source for the M.I.T. 320‐Mev electron synchrotron. A button cathode originally designed by Sperry Gyroscope Company was redesigned slightly to meet our specifications. With this new cathode, we have obtained an average lifetime of 330 hrs, operated at peak‐pulsed current of 200 ma in vacuums as poor as about 10−5mm Hg. This represents a factor of about 20 improvement in lifetime‐current product over directly heated cathodes.