Wall Relaxation of Polarised Helium-3 in Storage Cells as a Bound on Spin-Dependent Gradients

This paper examines how the hundred-hour storage lifetime of polarised helium-3 in coated cells limits any spin-dependent gradient that would relax the polarisation. The system considered is polarised helium-3 stored for of order one hundred hours in a five-centimetre coated cell, and the observable is relaxation rate, per-spin energy sensitivity and gradient limit. Evaluating the ordinary behaviour of the system and the spin-torsion contribution under explicit assumptions about polarisation and uniformity, and inverting the comparison at the stated laboratory precision, gives a quantitative bound rather than a qualitative assertion of smallness. The computed record is: T1_s = 3.600e+05; relaxation_rate_per_s = 2.778e-06; energy_J = 2.929e-40; torsion_bound_per_m = 9.266e-15; gradient_bound_per_m2 = 1.853e-13; cell_size_m = 0.05. The torsion-related contribution is far below the level that would alter the ordinary behaviour of the system at current precision, and the value that would have produced a visible residual is stated so that future improvements can be assessed against it directly. No new measurement is reported. This study is simulated and computed from stated assumptions, not measured.