If FoFu is to work, it will require Gigagauss fields. I don’t know if the filaments are the only way to do it.
The proton measurement technique I referred to measures the fields by deflecting protons using the field. It is a measurement that requires reconstruction but it can be done pretty accurately on paper. The practical reconstruction will be done next year by a group at UC San Diego working with a group at UN-Reno at the ~1MA level. I am optimistic the technique will work with reasonable accuracy. I will see if I can find any papers on it and report back.
