Abstract: A system for irradiating material used in transfusions. The material can be pre-transfused blood, blood components and marrow. The system includes a vacuum chamber with a plate cathode inside. The cathode has a large beam electrode field-electron emissive surface with a selected cross-sectional shaped area. A power supply is connected to the cathode for generating negative high-voltage pulses and causing a selected cross-sectional shaped beam of electrons to be emitted. An electron window is also disposed inside the vacuum chamber and made of thin metal foil. The electron window receives the selected cross-sectional shaped beam of electrons therethrough and onto an electron target disposed outside the vacuum chamber. The electron target receives the selected cross-sectional shaped beam of electrons thereon and generates a selected cross-sectional shaped X-ray beam. A cathode filter is disposed next to the electron target and eliminates low energy beams from the spectrum of the X-ray beam.