Suppose we have a Stern-Gerlach apparatus through which we send spin-1/2 particles and subsequently measure their position. If a passing particle "collapses" to the spin up state about X, it moves "up" and is registered by detector U, otherwise it "collapses" to the spin down state about X and moves "down" and is found by detector D. Now I'm wondering if it's possible to embed the passing particles within another detector S which measures the spin about Y (orthogonal to X) without affecting the net EM field from the Stern-Gerlach magnets around the particle? So a particle along with an "attached" detector S would move through the Stern-Gerlach together. I also want to assume (1) the detector S itself has no magnetic moment (if that's possible) and (2) the detector S can be programmed to measure the spin about Y at a fixed frequency F. If this setup is somehow feasible, I wonder what would happen when F is large? If we repeatedly measure the spin about Y I assume we must get an answer "up" or "down," but in that case it seems the spin cannot spend time in the states with spin up or down about X and hence it would go straight through the Stern-Gerlach, right? But is it possible for such a particle to go through a Stern-Gerlach detector and not "collapse" to the spin up or spin down state about X?