Abstract
As reported previously, slowly varying stray magnetic fields and, recently, additional 50 Hz fields deteriorate the lateral resolution in the low current mode of the high-energy ion nanoprobe LIPSION. Therefore, the active stray magnetic field compensation system AMK_5 has been installed in the LIPSION laboratory. This system utilizes six coils in a Helmholtz-arrangement and advanced technology for magnetic field sensing and signal processing for its operation and allows to reduce the stray field fluctuations to excellent ±10 nT in all three directions for frequencies from true DC up to the kHz range. A compensation factor >100 was obtained for the vertical direction. The compensation system was also used to determine the sensitivity of LIPSION to stray magnetic fields. It was found that the sensitivity is largest for stray fields along the beam direction leading to a beam spot movement of 1.1 m/T in both horizontal and vertical direction. Thus, the residual stray field fluctuations of ±10 nT result in beam spot movements of ±13 nm assuming a homogeneous stray field and no contribution from stray fields outside the shielded volume. It is demonstrated that the lateral resolution of LIPSION is significantly improved by the active compensation system. However, there are still beam spot fluctuations in both vertical and horizontal direction dominated by 50 Hz components which limit the resolution in the low current mode to approximately 130 nm. The source of these fluctuations is still unclear.
Published Version
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