Feedback schemes for radiation damping suppression in NMR: a control-theoretical perspective
C. Altafini, P. Cappellaro and D. Cory.
Systems and Control Letters, 59 (12):782–86, 2010.
In NMR spectroscopy, the collective measurement is weakly invasive and its back-action is called radiation damping.
The aim of this paper is to provide a control-theoretical analysis of the problem of suppressing this radiation damping.
It is shown that the two feedback schemes commonly used in the NMR practice correspond one to a high gain oputput feedback for the simple case of maintaining the spin 1/2 in its inverted state, and the second to a 2-degree of freedom control design with a prefeedback that exactly cancels the radiation damping field. A general high gain feedback stabilization design not requiring the knowledge of the radiation damping time constant is also investigated.