Electron microscope site survey data interpretation – part 2

Underground train systems 

Both vibrations and magnetic fields should be measured when studying the effects of an underground system. As the frequency of public transport systems increases due to demand, so does the level of interference. Cancelling systems are frequently needed to overcome the effects of the world becoming busier. 

It is often tricky to determine how close you are to a lift. It might seem as if you’ve walked along a few corridors to get to a microscopy room, but, in fact, you may have simply looped round in a square, bringing you back within metres of a lift. As lifts move up and down floors, they trigger interference gradients that constantly change over different heights, causing images to wander and jump around the screen due to large changes in magnetic fields. The interference is often so apparent that it is even possible for site survey readings to pinpoint which floor a lift is on. Lifts provide essential accessibility and ease of movement around facilities, so they are often unavoidable. In these instances, a cancelling system is the only solution. 

Vehicles 

The movement of vehicles in close proximity to microscopy rooms can create varied levels of interference, with larger magnetic field peaks coming from heavier vehicles, such as lorries or buses. A magnetic field cancelling system is often required to overcome these disturbances, as it is increasingly difficult to find areas that are not in the immediate vicinity to busy roads. 

Although it may seem obvious that magnets have magnetic fields, large systems built around magnets – such as NMR platforms – are designed to keep as much field inside as possible, and therefore the extent of their effect should, in theory, be minimal. In reality, it is unknown without conducting a site survey. In the situation even at a distance of 25 metres the field is multiple orders of magnitude above what can be tolerated by an electron microscope, and it is advisable to move the instrument and magnet further apart. 

Site surveys commonly uncover unexpected causes of interference. There was significant interference from an unknown source, and a survey was able to locate the source of interference as coming from a hearing loop that had been left behind ceiling tiles. In this case, the problem was easily rectified by renovation work.

As the world becomes a busier place and more technology is incorporated into laboratories, there are undoubtedly challenges in setting up and maintaining a stable microscopy environment, but measures can be put in place to ensure these are mitigated. The key is to think ahead and engage in discussions with microscopy suppliers, site surveyors and, in the case of a new build, architects, at the earliest possible opportunity. Having an experienced site surveyor with the right equipment is vital to identify common and unusual causes of interference and understand the magnitude of their effects. They can then advise on the best way to counteract these problems. This will allow electron microscopy to be installed in the most stable environment possible, whether it is in an existing facility or a newly set-up laboratory, ensuring the highest quality imaging is maintained.

For further information on Spicer site survey services and cancelling systems, contact us here.

Since it was established in 1988, Spicer Consulting has built a world-wide reputation in magnetic field cancelling for Electron Microscopes and similar instruments. Today, working with equipment manufacturers and users alike, the company is recognised as an industry expert in maximising the performance of electron microscopes, electron beam lithography systems, CD metrology and focused ion beam tools. 

Spicer Consulting magnetic field cancelling systems protect sensitive equipment in the world's leading laboratories, universities and semiconductor manufacturing plants, as well as in the test facilities of electron and ion beam equipment manufacturers. Its magnetic field, vibration and acoustic analysis systems have been adopted as standard equipment for the conduct of site surveys by leading equipment manufacturers. Spicer Consulting is located in Stewartby, Bedfordshire, within the United Kingdom’s Golden Triangle of elite universities in London, Cambridge and Oxford.