Performance with flexibility

Today, if you purchase a new transmission electron microscope (TEM), you can specify a choice of objective-lens pole-pieces. Pole-pieces with the smallest pole-gaps exhibit the lowest spherical and chromatic aberrations, and will produce images with better resolution. Unfortunately, these small gaps will have less space for sample tilting, x-ray detectors, or in-situ holders. Conversely, large gap pole-pieces will offer more flexible space for experimental applications but won’t reach the ultimate optical performance.

For instruments in shared microscopy facilities, the pole-piece might then be optimised for one usage scenario (to the detriment of others), or a middle-ground compromise that is optimised for no one. The significant cost of a flagship TEM, perhaps €5M, means that having two instruments side by side is not economical.

Instead, we propose a User Adjustable Pole-piece (UAP) where the pole-piece gap can be adjusted by the TEM operator without the need for engineer support or losing the column vacuum.

This project was initiated in April 2018 to explore the feasibility of constructing an adjustable lens. The research includes studies of the design, construction, and magnetic performance of modern objective lenses.

We have designed a replacement pole-piece for the JEOL architecture of TEM platforms with an initial focus on a 200/300kV design. The pole-gap adjustment is achieved by a sliding concentric mechanism (patent pending). The initial results were submitted to the European Microscopy Congress (EMC) proceedings: Patrick McBean, David O’Mahony and Lewys Jones, “Development of a User Adjustable Pole-piece Gap Objective-lens”, DOI:10.22443/rms.emc2020.322.

This research is part of the “RetroTEM” project supported by a Science Foundation Ireland (SFI) and Royal Society University Research Fellowship (grant no. URF/RI/191637), and the SFI Advanced Materials and BioEngineering Research centre (AMBER).

Initial Community Feedback

“This new pole-piece will be beneficial not only for users but also for those who run shared facilities. We can customize our microscope easily and perform many different experiments with one microscope.”

The UAP concept refreshes a very old idea of adjustable pole pieces for TEM/STEM/AEM but brings this into today’s era of multi-modal characterization. The ability to alternatively perform high-resolution imaging using a small gap, followed by analysis with a large gap, without removing the holder or venting the column, creates opportunities for new experimental configurations. Based on the UAP spec’s (and my recent discussions visiting the group in Dublin!) not only will good XEDS capabilities be possible, but also the development of new systems facilitating a wide range of future analytical and operational modes.

“The new concept of the ‘user adjustable pole-piece’ will free microscopists from the chronic pain of pole-piece selection. The pole-piece gap will be a new free parameter to optimize the respective experimental design, like defocus!”

“The successful production of this variable gap pole-piece will seriously enhance the flexibility of the instrument into which it is installed. I’m quite excited to see the outcome of this endeavor!”

“A great idea for making JEOL microscopes more versatile! High resolution and analytical setups when needed.”

The UAP is supported by