The Simplicity of Solenoids

After working through the spherical solenoid models yesterday, I did a few more models on plain-old solenoids to see how well we could do by just extending the length of the solenoid. Given that your Dewar is about five feet tall and our sample is at most six inches in diameter, we have plenty of room to wrap a solenoid that is several times longer than the sample. The graphs below show the percent variance between the maximum field at the center of the solenoid and the field at the edge of the spherical lead sample for the direction parallel to the solenoid, (second picture), and the direction perpendicular to the solenoid, (third picture).

So, for the amount of effort required, the solenoids look like the easiest thing to construct with better results than the spherical coil. The downside is that the 4 X long solenoid will require more superconducting wire and more liquid helium to fill the Dewar, both of which are sort of pricey.

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