Table top SEM microscopes are small sized Scanning Electron Microscopes used in earth science, electronics, manufacturing, in life sciences and even in forensics. There are many models available, however, they all share the same scanning principle with the use of a electron beam.
Compared to the big brothers of electron microscopes, like TEM's, table top microscopes are much less sensitive to electromagnetic interference. However, while the large TEM's have the luxury of site surveys performed before room selection, table top microscopes are placed nearly anywhere without taking to much effort to check the room conditions first.
Sources of magnetic stray fields:
Mostly, the existing magnetic stray fields do not affect the electron beam, however, we have met several sites where the magneitc fields present are well over the specs. Consequently, scanning quality is very limited. Typical sources of magnetic fields: Sub way, trains, tram ways, electrical cables, electrical distribution panels or nearby magnets.
How are magnetic stray fields detected? The first indication is the microscope itself. When scanning quality issues are present, chances are good that magnetic stray fields are present, too. With the aid of gauss meters, the presence could be confirmed and sometimes the source can be found. However, often it's impossible to find the source and even if founded, in many cases it's impossible to eliminate it. Systron also offers measurements on site and is thus able to suggest best possible measures.
With Systron LabShield®, magnetic shielding enclosures can be offered to block those background stray fields to ensure maximum performance of the SEM. The shields are mu-metal based and offer high attenuation against DC and AC fields. The enclosures come either as standardized enclosures or are tailord to the specific microscope shape and use.