We removed the large eddy current damper magnets from the UIM blade spring in the quads, and there remains a question about whether we can use a small magnet to attach a tuned mechanical damper to the blade spring. I have measured the relative permeability of a blade to be greater than 6 (here), so it is possible that the blade spring will “amplify” the moment of the magnet. For this reason, I attached a magnet to the blade spring at the proposed location and measured the magnetic moment of the blade spring in my moment balance (Figure 1).

Adding the 0.013 J/T 2x6 mm magnet to the blade spring increased the moment of a single blade spring by 0.12 J/T in the beamline direction. The resulting displacement noise of the test mass from ambient fields acting on a single such blade spring would be about 3.1 e-20 m/sqrt(Hz) at 10 Hz (assuming 2e-11 T/ sqrt(Hz) ambient magnetic field).  For this reason, I think that we should not use 2x6 or 2x3 magnets on the blade springs without a cancelation scheme. As a comparison, the large magnets used by the BOSEMs have a moment of 0.72 J/T, but with all of the cancelations from orientation, I have estimated that the remaining moment (with no orientation errors) would be about 0.2 J/T (here). If there are no other ways of attachment, I can try cancellation schemes, but they may not be very successful because one of the magnets is in contact with the ferromagnetic material.