Nah - not required.
A couple of facts for EMP generated by Nuclear devices in the atmosphere. According to an Air Force officer who gave a talk some 30 years ago - you can expect to see something like 30KV/m2 from DC to many Ghz. The pulse will be several nanoseconds in duration.
The officer wasn’t sure ANYTHING would be sufficient to shield against such a pulse.
That being said - from some other things I’ve read/heard - you aren’t going to have any significant effect on a magnetic field. A professor in EE told me about his brother having a contract to create the equivalent to a Faraday cage for Magnetic fields from the Navy. The brother set up an experiment where he created a Mu-metal cage around a detector on the theory that the cage would route the field around the detector. He placed a record player with a bar-magnet 100 feet away. Real nice sine-wave detected inside said cage... so much for Mu Metal..
If you were to discover a way to shield against a magnetic field you could use that tech to quickly create a magnetic perpetual motion machine.
This means that magnetic shielding is impossible.
Gravity based perpetual motion machines are also impossible because there is no such thing as a gravity shield.
Magnetism and gravity can only be negated by another magnetic or gravity field...at least in a Newtonian universe. :-)
You say even mu-metal wouldn't work, but RFEngineer says even steel is good enough to work. One of you is clearly wrong (or both). However, I think that you are probably correct. A high-current pulse with a very short pulse-length is bound to produce a very high magnetic field.
The unclassified EMP states up to 50,000 V/m from about 5kHz to 1GHz
The pulse rise time is about a nanosecond (that’s where the top end 1 GHz comes from)
“The officer wasn’t sure ANYTHING would be sufficient to shield against such a pulse.”
Steel will do it - low frequency permeability ducts magnetic flux around the shield. At higher frequencies it’s conductive enough to suffice.
“The brother set up an experiment where he created a Mu-metal cage around a detector on the theory that the cage would route the field around the detector.”
Not at the very low frequencies, low magnitudes involved in your described test scenario - the low-level magnetic pulse will blow through the shielding because there isn’t enough magnetization energy. This is a big problem for sensitive instruments such as newer electron microscopes.
At even slightly higher frequencies, passive eddy current shielding works very well for magnetic fields (such as 60Hz)