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Dipoles

Dipoles consist of a pair of magnets across a gap.  They come in many shapes/sizes and the magnets are usually mounted on a steel frame (also called a yoke) for magnetic efficiency, magnetic shielding and/or mechanical strength.  Dipoles are used when an application requires a specific magnetic field strength and uniformity over a specific volume.  Pole pieces are sometimes used to enhance uniformity within the gap.

Dexter has built hundreds of different types of dipoles, each optimized for a particular application.  Field strengths have ranged as high as 3.0 Tesla (30,000 Gauss).  Generally, higher fields are associated with small air gaps.  Higher uniformity is generally associated with large air gaps.

Dipoles are used to:

  • Calibrate/initialize magnetic sensors
  • Erase computer hard disk drives
  • Orient thin layers of magnetic material as they are deposited as thin films
  • Divert or focus beams of energized particles
Dexter_MRI_Dipole_2 Dexter_Dipole_Wireframe_Flux_Line_Image
 

We've utilized the dipole principle in our following designs:

When working with our engineering group, you might be asked:

  1. What is the minimum magnetic field strength required?
  2. How large a volume?
  3. How large can the dipole be, does it have to fit within other devices?
  4. Will the dipole be exposed to elevated or cryogenic temperatures?
  5. Will the dipole be exposed to vacuum or corrosive gases/fluids?
  6. Do you need the polarity marked?

Neodymium Iron Boron and Samarium Cobalt are often used when large magnetic fields are required.  Hard ferrite is used if cost is more important than large magnetic fields. Alnico is generally used if dipole is to be used in high temperature environment (>300°C).

  1. What is the strongest magnetic field you can create?
  2. How large can the magnet be?
  3. I need a dipole to work in an oven, is this possible?

1.  To date, the strongest magnetic field we have created is 3 Tesla (30,000 Gauss) across a 5mm air gap.

2.  Our largest magnet to date is cube shaped, approximately 2 meters per side.

3.  One typically uses Alnico materials for high temperature applications.  If Alnico material is not strong enough, then the dipole should be designed around the exterior of the oven.

Feasibility Study Required: No
Typical Design Time: 1-2 Days
Typical Material Acquisition & Build Time:
2 Weeks, if material is available
6-8 Weeks, if material is not available.

 

A simple dipole can be designed within 1 to 2 days.  If materials are immediately available, it can be constructed and shipped within 2 weeks, otherwise 6 to 8 weeks is the norm.  Complex designs will involve more time on the design/construction phases.  Magnetic field mapping can be done to ensure the design meets specifications.