Magnetic Shield FAQ

Thinking about purchasing a Twinleaf magnetic shield? Here is a list of the most commonly asked questions related to the MS series. If the answer to your question isn't below, get in touch with us at info@twinleaf.com.

Why use a Twinleaf shield?

A Twinleaf magnetic shield has been thoroughly designed and tested to provide high shielding factor and high field uniformity. The internal magnetic field coils provide a controlled magnetic environment, both near zero field to above Earth's field. A high performance experimental apparatus can be quickly assembled with a Twinleaf shield at its core. The cage plates and the internal breadboard offer flexible mounting options.

What magnetic shields do you offer?

There are three models of MS shields:

MS-1L is a compact, 4 layer mu metal shield.
MS-1LF is a version of the MS-1L with a ferrite inner for lower thermal magnetic noise.
MS-2 is a larger, though still desktop-sized, four layer shield.

What is the lead time?

Lead times vary depending on what we have in stock. MS-1L and MS-2 are typically available in 6-8 weeks or less. MS-1LF (ferrite) shields may have significantly longer lead times. Get in touch (info@twinleaf.com) for up to date information about stock and lead times.

What does shipping cost?

Mu metal is extremely sensitive to physical shocks. Its magnetic shielding properties can be sharply reduced by poor handling. As such, our shields are shipped in large, double-enclosed 20 cube boxes with lots of foam padding. The large size of the shipping box and comparatively heavy weight may result in substantial shipping costs, especially for overseas shipments.

The MS-2 shield is large enough to necessitate shipping in a palletized wooden crate. The crate must be sent via freight carrier, which may add the lead time for deliveries.

Do I need a ferrite shield for my application?

Probably not. The MS-1LF's primary benefit is a lower intrinsic magnetic noise floor: about 10 times lower. That is, there is less thermal magnetic noise inside the shield. Unless you are building extremely sensitive optical magnetometers, or doing other experiments that require below 10-15 fT/rt(Hz) magnetic noise, an MS-1L is probably a better choice.

What is the field inside of an MS when it's closed?

There are two points to answering this question: Noise, and static fields.

External fields include mains (50/60 Hz) noise, Earth's field, nearby ferromagnetic objects, etc. With a DC shielding factor greater than 10⁶, Earth's field is attenuated below 1 nT. AC signals are shielded even more; mains noise is reduced far below 1 pT.

The magnetic field inside an MS shield depends on how well it has been degaussed. If the shield components are exposed to strong external fields while disassembled, those components can be magnetized and the residual field will affect the interior when the shield is closed again. Degaussing is the process of removing this external magnetization.

The built-in field coils of MS shields can be used to offset internal fields well enough to operate SERF magnetometers, which typically require less than 10 nT of residual field.

How do I degauss?

Please see our DG user guide

Why are there so many holes?!

Don't worry about the holes! Although they may appear numerous, our shields are designed using the latest available finite element and field homogeneity simulations. The holes are carefully placed and sized such that they will not affect the field homogeneity or shielding inside the shield.

What is the maximum field that can be achieved in your shield?/What is the maximum current that can be applied to the internal field/gradient coils?

The maximum recommended current for any coil is 1 amp. Above this input, significant heating of the field coil traces can occur. The limiting factor is the vias in the field coil flex circuit.