= Hahn spin echo experiment
{c}
<Erwin Louis Hahn>'s 1950 apparatus enclosed <liquid> samples in the coil of a tuned <LC circuit>, coupled to a gated <radio transmitter> and <radio receiver>. One transmitter quadrupled a crystal <oscillator>'s 7.5 MHz to 30 MHz. A separate <proton> resonance regulator stabilized the static <magnetic field>.<Spin Echoes by Erwin Louis Hahn>[§IV, Figs. 12–13: transmitter, coil, receiver and regulator]{ref}
Waiting for <thermal equilibrium> prepared <nuclear polarization>. <Oscilloscope> photographs compared <glycerol> <proton> echoes at different field homogeneity: echo width changed; echo time followed twice the pulse separation. Receiver saturation obscured early <free induction decay>; transmitter leakage required care. The delayed <signal> tested refocusing; <diffusion> could still attenuate it.<Spin Echoes by Erwin Louis Hahn>[§II(B), Fig. 2, §IV: preparation, timing, homogeneity comparison and readout limits]{ref}
Hahn analyzed equal pulses as well as noting improved recovery with a second pulse twice as long; the ideal sequence above isolates that latter case.<Spin Echoes by Erwin Louis Hahn>[§III(B), Fig. 1; footnote discussing a doubled second pulse and drive inhomogeneity]{ref}
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