| 摘要 |
<p>An ion beam generation apparatus comprising an ion source (20) for generating ions, and a tetrode extraction assembly (11) comprising four electrodes for extracting and accelerating ions from the ion source. The extraction assembly comprises a source electrode (22) at the potential of the ion source, an extraction electrode (23) adjacent to the source electrode to extract ions from the ion source (20), a ground electrode (25), and a suppression electrode (24) between the extraction electrode and the ground electrode. Each electrode has an aperture to allow the ion beam to pass therethrough. The gap between the extraction (23) and suppression (24) electrodes is variable in the direction of ion beam travel.</p> |
