< Longitudinal field | Index | Setup >
The muon spin precesses in a plane perpendicular to the external magnetic field, describing an angle {$\theta= \gamma B t$} and the probability distribution lobe for the emission of the positrons from the decay precesses with it. An ensemble of muons will then modulate armonically the decay rate detected in a given direction
{$ dN(t)\, =\, N_0 \,e^{-t/\tau} (1\, + \,A \,\cos\gamma B t) dt\,d\theta $}
|
|
|
The animation shows the oscillations in the muon asymmetry, as the muon spin precesses, sweeping the probability lobe past the detector. Count rate may be e.g. in counts per ns.
|
|
Actually the muon decay counts are acquired vs. time elapsed from implantation, over a large ensemble of muons. Muons are implanted either one by one, at continuous sources, or in bunches of hundreds, at pulsed sources. Individual lifetimes are thus recorded for milions of muon events, each contributing with one count in one time bin. All these events are accumulated independently, over long times, minutes to hours. Coherence is guaranteed by the fact that all muons at implantation (time zero in the plot) have the same spin polarization.
|
< Longitudinal field | Index | Setup >
