The present specification discloses a high power continuous X-ray source having a rotating target assembly that is cooled by circulation of a liquid material in contact with the target assembly, whereby the target assembly has a front surface being impinged by electrons and a mechanism for rotating the target assembly. The cooling liquid is always in contact with at least one surface of the target for dissipating the heat generated by the energy deposited by the stream of electrons, thereby lowering the temperature of the target to allow for continuous operation.