Research today deals with microscopically small parts, often even with dimensions in the range of a few nanometres. The devices used for this, react particularly sensitive to electromagnetic fields. Therefore, appropriately protected laboratories are needed in which such fields are reduced. These can be reduced with two different techniques: either with passive magnetic room shielding or with active cancellation systems. Often the two techniques are also combined.
Systron designs, manufactures and installs room shields and shielding booths based on Systron LabShield®, the Mu-Metal shielding system, to protect electron beam equipment from low frequency magnetic fields.
With Systron LabShield®, a passive magnetic room shielding system based on mu-metal, entire rooms are protected against static, slowly changing and electromagnetic AC and DC fields. This effectively protects the sensitive electron beam equipment operated in the rooms, such as electron microscopes or electron beam lithography, from the interference fields. Such interference fields are caused by magnets, vehicles, lifts, and electrical components such as transformers, cables, high-voltage lines, railway systems or trams.
Instead of room shielding, free-standing, magnetically shielded booths, EMF shielding booths, are also used to protect sensitive equipment. Such devices are for example electron microscopes, electron beam lithography, mask inspection devices but also medical, electrophysiological devices for electroencephalography (EEG) or electromyography (EMG).
The shielding booths are based on a frame construction that can be set up free-standing or integrated in the room. Depending on the application, mu-metal or silicon iron-based metal alloys are used to shield the magnetic interference fields. This effectively reduces slowly changing direct fields and/or electromagnetic alternating fields. These fields are caused by magnets, vehicles, lifts and electrical components such as transformers, cables, high-voltage lines, railway systems or trams.
Active magnetic field compensation systems are specially designed to reduce low-frequency magnetic fields to the lowest possible values. Compensation systems are used to keep interference fields away from electron beam based equipment.
Compensation systems reduce low-frequency magnetic fields caused by vehicles, lifts, railways, electrical installations or other sources of interference, in real time. With a sensitive sensor, the interference fields are measured and actively compensated by counter fields. The prerequisite for effective compensation is a homogeneous interference field with a low gradient. This is usually the case for distant field sources such as high-voltage power lines, trams and railway installations. If the sources are close by, such as power rails or electric cables, the compensation effect is reduced.
Shielding housings for tabletop microscopes are manufactured individually according to the microscope. This effectively reduces even strong, local interference fields. The tabletop microscopes can therefore also be operated in electromagnetically unfavourable locations.
SEM tabletop microscopes are smaller “Scanning Electron Microscopes”, SEM’s, which are used in many scientific fields such as electronics, production, life sciences and even forensics. Tabletop microscopes are available in many different designs, but they all share the scanning principle, which is based on an electron beam.
Compared to large microscopes, such as TEMs, tabletop microscopes are far less sensitive to electromagnetic influences. On the other hand, the locations where tabletop microscopes are used are not examined beforehand with regard to electromagnetic interference fields. As a result, tabletop microscopes are often located in places with strong stray electromagnetic fields. The operation of the microscopes in such environments is thus severely restricted or even made impossible. Typical electromagnetic sources that interfere with tabletop microscopes are building-internal electrical installations such as electrical cables in parapet ducts, risers, cable trays, the building’s internal transformer station, but also magnetic lifts, trams or DC magnets.
The shielding housings for tabletop microscopes are made of heat-treated mu-metal and effectively reduce magnetic AC alternating and DC direct fields.
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