Why Proper Electromagnet Specification Matters
Many electromagnet projects fail for one simple reason:
the specification was incomplete or ambiguous.
Researchers often describe the target magnetic field very clearly.
However, key geometric parameters are missing.
As a result:
- The field uniformity is worse than expected
- The sample does not fit inside the magnet
- The working distance is insufficient
- Redesign becomes unavoidable
This article explains how to specify an electromagnet correctly, using four essential parameters:
pole gap, pole face, aperture, and working distance.
Pole Gap: Defining the Magnetic Field Space
The pole gap is the distance between the two magnetic poles.
It directly determines:
- Maximum achievable field
- Field uniformity
- Available space for the sample
A smaller gap allows higher magnetic fields at lower power.
A larger gap increases flexibility but reduces field strength.
Common mistake:
Specifying the field strength without defining the required pole gap.
Practical tip:
Always specify the required field at the actual pole gap, not at an idealized value.
Pole Face: Controlling Field Uniformity
The pole face refers to the shape and size of the pole surfaces.
Pole face geometry affects:
- Field homogeneity
- Edge effects
- Sensitivity to misalignment
Typical pole face options include:
- Flat pole faces for general use
- Chamfered or profiled faces for improved uniformity
Key question to answer:
What is the required uniform volume, and how is it defined?
Uniformity should always be expressed with:
- Percentage (±1%, ±0.5%, etc.)
- Spatial definition (diameter, cube, or plane)
Aperture: Ensuring Mechanical Compatibility
The aperture is the clear opening available for the sample and fixtures.
It must account for:
- Sample size
- Sample holder
- Probes, wiring, or cryostats
A common oversight is ignoring future upgrades.
Today’s experiment may require more space tomorrow.
Best practice:
Specify the minimum required aperture, plus reasonable margin.
Working Distance: The Hidden Constraint
The working distance is the usable space between the pole face and the sample.
This parameter is critical for:
- Optical access
- Probe clearance
- Motion stages
Many users confuse working distance with pole gap.
They are not the same.
Working distance must consider:
- Sample thickness
- Mounting hardware
- Adjustment tolerance
If working distance is not specified, the magnet may be unusable for the intended setup.
Putting It All Together: A Simple Specification Template
When requesting an electromagnet quotation, include the following:
- Target magnetic field and stability
- Pole gap at which the field is required
- Pole face shape and uniformity definition
- Required aperture
- Minimum working distance
- Duty cycle and cooling preference
👉 Product link placeholder: Cryomagtech Custom Electromagnet Solutions
Cryomagtech supports both standard and fully customized electromagnet designs, helping users translate experimental needs into manufacturable systems.
References
- Wikipedia – Electromagnet
https://en.wikipedia.org/wiki/Electromagnet - IEEE – Magnetic field design and electromagnet engineering
https://ieeexplore.ieee.org/
Final Thoughts
An electromagnet is not defined by field strength alone.
Geometry defines whether the field is usable.
Clear specifications save:
- Time
- Cost
- Iterations
Most importantly, they ensure the delivered system matches the experiment.