A method for characterizing an electron beam in a liquid metal jet X-ray source. The method includes providing the electron beam and directing the electron beam to an interaction region; providing an electron beam dump connected to ground potential for receiving the electron beam after it has traversed the interaction region; scanning the electron beam over at least part of the interaction region; measuring X-ray radiation generated by interaction between the electron beam and the electron beam dump during the scanning to obtain an X-ray profile; and calculating an electron beam characteristic based on the X-ray profile. Also a corresponding liquid metal jet X-ray source.