Magnetic fields can be the most disruptive and noticeable form of environmental noise, commonly affecting transmission electron microscopes (TEMs) and scanning electron microscopes (SEMs).
Image Credit: Herzan LLC
DC fields are often presented as wavy lines in the image, while AC Fields are commonly create sharp jagged edges in the image. This level of disturbance can either limit the ability of the TEM and SEM to retain clarity from the sample being measured or require a mitigation solution.
Thankfully, a number of mitigation solutions are available based on what best suits the researcher or lab.
Solutions for Cancelling Magnetic Fields
Removing Magnetic Fields at the Source
If available, addressing magnetic fields at the source can be the most immediate and cost effective solution.
Often, DC Field issues result from large metal objects moving within the earth’s magnetic field, while AC Field issues originate from unintentional currents in loops (i.e. ground conductors), current-carrying power lines, or air conditioning and lighting systems.
Re-conditioning or removing these sources from the room can have a huge imapct on the imaging resolution of a SEM/TEM, allowing the lab to meet environmental specifications and the researcher to focus on what matters most: their research.
Current-carrying power lines. Image Credit: Herzan LLC
Moving Rooms for TEMs/SEMs
A free and simple solution can be moving the lab location for a TEM/SEM to a lab with lower magnetic fields. Site surveys are helpful to establish the ambient AC/DC Field levels of multiple rooms, where researchers are able to compare the measured AC/DC Fields with the specification set by the manufacturer for their SEM/TEM.
SEM/TEM manufacturers almost universally need a site survey to be carried out at the customer site before installation. Often, their team of field service engineers capture this data, or partners such as Herzan are asked to carry out local site surveys for their customers.
Selecting the right lab room is crucial, and can save significant time and money not having to mitigate magnetic fields from the lab.
Room Chosen for TEM. Image Credit: Herzan LLC
Magnetic Field Cancellation System
When researchers are set on a specific lab room to operate their SEM/TEM, and cannot improve the local AC/DC fields in their lab, magnetic field cancellation systems are recommended.
Magnetic field cancellation systems provide dynamic cancellation to AC and/or DC fields for almost every SEM/TEM. Magnetic field cancellation systems are a lot less expensive than passive shielding solutions like placing mu metal throughout the lab.
SC22 Controller. Image Credit: Herzan LLC
SC24 Controller. Image Credit: Herzan LLC
The SC24 System provides high-performance AC/DC field cancellation, while the SC 22 System supplies a cost-effective solution for addressing AC fields. Both of these solutions are provided by Herzan to customers in North America and are manufactured by Spicer Consulting: the world’s leader in magnetic field cancellation.
This information has been sourced, reviewed and adapted from materials provided by Herzan LLC.
For more information on this source, please visit Herzan LLC.