The calibration of the gradient strength is usually performed by:
Measuring the diffusion rate for the residual proton water line in the calibration sample at 25C, and back calculating G. This assumes that D(HDO) in D
2
O is 1.90*10
-5
cm
2
/s.
Acquiring an spin-echo FID with the z-axis gradient on during acquisition. This yields a spatial profile of the sample, which is function of the sample height and the gradient strength.
