Enhanced electron beam generation

A method for forming a three-dimensional article through successively depositing individual layers of powder material that are fused together with an electron beam from an electron beam source so as to form the article, the method comprising the steps of:

• arranging a contraction aperture between an anode and at least one deflection coil, where the contraction aperture is aligned with an aperture in the anode with respect to a cathode of the electron beam source and where the contraction aperture is smaller than the aperture of the anode;
• arranging a first vacuum pump between the contraction aperture and the anode and a second vacuum pump above the anode;
• conducting a first crossover of the electron beam above the anode,
• conducting a second crossover at or in close proximity to the contraction aperture,
• injecting a gas into the electron beam source, wherein a gas inlet is arranged between the contraction aperture and the at least one deflection coil.

A computer program product comprising at least one non-transitory computer-readable storage medium having computer-readable program code portions embodied therein, the computer-readable program code portions comprising one or more executable portions configured for:

• directing an electron beam from the at least one electron beam source over the work table to fuse in first selected locations according to the model to form a first cross section of the three-dimensional article
• conducting a first crossover of the electron beam above an anode of the at least one electron beam source,
• conducting a second crossover at or in close proximity to a contraction aperture, which contraction aperture is arranged between the anode and means for deflecting the electron beam, and
• injecting a gas into the electron beam source, wherein a gas inlet is arranged between the contraction aperture and means for deflecting the electron beam and where the contraction aperture is smaller than an aperture of the anode.