Magnetic Shielding

Our Guaranteed Magnetic and Radio Frequency Shielding Systems.

What is Passive Magnetic Shielding?

Rigid (passive) magnetic shielding is divided into two fundamental types based upon the magnetic and conductive properties of the shielding materials: flux-entrapment shields and lossy shields:

A flux-entrapment or flux ducting shield is constructed with a permeable (μ) ferromagnetic material such as low-carbon steel, silicon-iron steel (oriented and non-oriented) and nickel-iron alloy which either surrounds (cylinder or rectangular box) or separates (“U” shaped or flat-plate) the victim (i.e., people or equipment) from the magnetic field source.  Ideally, magnetic flux lines incident upon the flux entrapment shield prefer to enter the permeable (μ) material via the path of least magnetic reluctance ℜ, rather than pass into the protected (shielded) space. The higher the permeability the more magnetic flux lines will prefer to travel within the material rather than a lower permeable material including air (or vacuum) which has the lowest mu (μ) of 1.

Lossy shielding depends on the eddy-current losses that occur within highly conductive copper and aluminum materials, and higher permeable (μ) ferromagnetic materials that are also less conductive.  When a highly conductive materials are subjected to a time-varying (60Hz) magnetic fields, currents are induced within the material that flow in closed circular paths, perpendicular to the inducing field.  According to Lenz’s Law, these eddy-currents oppose changes in the inducing field, therefore the magnetic fields produced by the circulating eddy-currents attempt to cancel the larger external fields near the conductive surface, thereby generating a very effective shielding effect.

What’s Your Shielding Factor?

Shielding Factor (SF) is the ratio between the unperturbed magnetic field Bo and the shielded magnetic field Bi as expressed in: SF = Bi/Bo The final shielding design depends on several critical factors: maximum predicted worst-case 60-Hz magnetic field intensity (magnitude and polarization) and the geomagnetic (DC static) field at that location- whichever is greater; shield geometry and volumetric area; type of materials, permeability, induction & saturation; and, number of shield layers.

To Shield or Not to Shield?

It is usually not desirable, especially if office or living space is limited, to evacuate an entire room or several rooms exposed to very high magnetic field levels. So, when space is at a premium the only other alternative is magnetic field shielding. To shield or not to shield the source? That is the question! Generally, when physically practical, source shielding is the most effective and least expensive alternative. However, if there are multiple magnetic field sources (i.e., parallel transformer vaults, network protectors, secondary feeders, etc.) it may not be economically feasible to separately shield each source. In that case shielding the room, and consequently the victims, is the preferred solution.

Guaranteed and Cost Effective Mitigation Solutions.

Vitatech specializes in research, scientific and medical diagnostic shielded enclosures. For more than 25 years, Vitatech has shielded high magnetic field sources such as substations, network protectors, switchgears, electrical rooms, risers, busways, cable trays and more.

Upon client approval of our magnetic field management recommendation and quote for services, Vitatech prepares a detailed, engineered design and project management schedule, implements corrective measures, manages subcontractors, and provides a final ELF EMF survey to verify the results.

Low Frequency Magnetic Shielding

RF, EMP, & HEMP Shielding.

The other invisible threat we know all about Radio Frequency Interference (RFI), is increasingly an issue for siting sensitive instruments, communications system design and operation, and human RF exposure safety.

Vitatech has shielding design expertise measuring and simulating radio-frequency (RF) threats and designing cost-effect RF shielding solutions to attenuate (reduce) elevated and high E-Field and H-Field electric field, planewave and microwave environments from 14 kHz to 26 GHz. Besides our standard and special wideband RF expertise, we simulate, design and install specialized High Altitude Electromagnetic Plus (HEMP) / EMP shielded facilities for military command centers, commercial and university research projects.

RF Shielding & RFI Mitigation

Vitatech designs and installs medium to high performance -50 dB to over -100 dB RF shielded rooms from 14 kHz to 10 GHz for human and animal research MRIs (1.5T, 3T, 7T, 9.4T, 11.7T), scientific / medical instrumentation, biomedical (EEGs, EKGs, MEGs, etc.) research, secure computer rooms, and TEMPEST / SCIF facilities. For specialized wide-band shielding projects we can integrate low frequency DC to 14 kHz static DC, quasi-static DC and time-varying 16 Hz, 25 Hz, 50 Hz & 60 Hz magnetic shielding into any type of RF (14 kHz to 10 GHz) shielded room design for maximum bandwidth, attenuation and performance.

_

EMP/HEMP Shielding

Vitatech has designed several medium to large EMP /HEMP shielded facilities, written detailed specification documents, reviewed bids & proposal, provided construction administration during on-site fabrication, and reviewed third-party HEMP / EMP final testing documentation for certification. All HEMP shielded projects were classified. EMP shielded test facility was designed to contain high-voltage EMI / RFI transient and wideband pulse emissions during controlled discharges / simulated lightning strikes.