On The Effect of a Negative Resistence Circuit On a Nuclear Magnetic Resonance Sample

It was found that a rather simple transistor circuit, in a way similar to a crystal controlled oscillator, can be made to oscillate using a liquid sample of hydrogeneous material inmersed in a homogeneous magnetic field as the frequency determining device. The oscillations are intermittent, with a period of tens of seconds, the duration depending on the sample used (tetramethylsilane, benzene, water). It can be made continuous using a simple AGC (automatic gain control) circuit. Once a certain mechanism of the oscillations was assumed Bloch's equations were modified by the addition of feed-back and pumping terms. Numerical integration showed that the equations can reproduce well the behavior of the magnetization vector under the influence of the circuit; its path in space and time; the reason of the intermittency; the amount of maser effect amplification achieved and also, after a further modification, the effect of the AGC circuit. I