Abstract: An apparatus (200) for accelerating an ion beam comprising: a) a first electrode (202) having a proximal side and a distal side and having at least one aperture (201) therethrough, the wall of the aperture being shaped such that the radius of the aperture on the distal side of the first electrode is greater than that on the proximal side of the electrode; b) a second electrode (204) located such that it is adjacent to but spaced from the distal side of the first electrode and having at least one aperture therethrough; and c) a third electrode (206) located such that it is adjacent to and spaced from the second electrode and having at least one aperture therethrough, said at least one apertures in each electrode being aligned with corresponding apertures in the other electrodes; wherein the electrodes are arranged such that there is a potential difference between the first and second electrodes and a potential difference between the second and third electrodes.

Abstract: An apparatus (200) for accelerating an ion beam comprising: a) a first electrode (202) having a proximal side and a distal side and having at least one aperture (201) therethrough, the wall of the aperture being shaped such that the radius of the aperture on the distal side of the first electrode is greater than that on the proximal side of the electrode; b) a second electrode (204) located such that it is adjacent to but spaced from the distal side of the first electrode and having at least one aperture therethrough; and c) a third electrode (206) located such that it is adjacent to and spaced from the second electrode and having at least one aperture therethrough, said at least one apertures in each electrode being aligned with corresponding apertures in the other electrodes; wherein the electrodes are arranged such that there is a potential difference between the first and second electrodes and a potential difference between the second and third electrodes.

Abstract: An ion implanter has an ion source (10) and an ion beam extraction assembly (50) for extracting the ions. The extraction assembly (50) is a tetrode structure and one of the pairs of extraction electrodes (51) has left and right ports (54, 55) located in opposite sides of the ion beam emerging from the ion source (10). The left and right electrode ports (54, 55) are electrically isolated from each other and connected to independent voltage sources (210, 230). The ion implanter also has a baffle plate (60) at the entrance to a mass analyser (90) downstream of the extraction assembly (50). The baffle plate (60) is also split into two halves (60? and 60?). By measuring the beam current incident on the two halves (60?, 60?) of the baffle (60), the relative voltages supplied to the left and right electrode parts (54, 55) may be adjusted so as to steer the ion beam and adjust the angle of incidence of the longitudinal axis thereof relative to the input of the analysing magnet (90).