Hexapole corrector for LVEM

In recent years, aberration correction has slowly become standard in high-end conventional transmission electron microscopy (50-200 kV). However, the integration of correctors to low voltage transmission systems (5-25 kV) has proved to be difficult. The hexapole corrector based on permanent magnet technology seems to be a promising solution for the correction of the primary spherical aberration. Especially if the compact dimensions and low complexity are to be preserved. However, the high importance of chromatic aberration with respect to the microscope resolution still remains a serious obstacle. It must be taken into account when the design is made. The following presented concept is intended exclusively for STEM mode to avoid additional chromatic deterioration caused by electron passage through the sample. The design of the key segment (transfer lens doublet) is discussed in detail, including its compensation systems, which guarantees proper alignment.