Perturbed Angular Correlation (PAC)
Perturbed Angular Correlation (PAC)
Perturbed Angular Correlation (PAC)
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<strong>Perturbed</strong> <strong>Angular</strong> <strong>Correlation</strong><br />
(<strong>PAC</strong>)
<strong>Perturbed</strong> <strong>Angular</strong> <strong>Correlation</strong> (<strong>PAC</strong>)<br />
Applying the method of perturbed γγ-angular correlation (<strong>PAC</strong>) one<br />
measures in contrast to the Mößbauer effect not an energetic shift of a γ-line<br />
which characterizes the state of the probe, but one measures the time<br />
variable γ-angular emission characteristic. One can also say that the γ-<br />
angular correlation distribution rotates or precesses like the fire of a<br />
lighthouse. The cause for this effect is the hyperfine interaction of a nucleus<br />
in an excited state which has a finite lifetime, long enough, that the<br />
precession can work. Precondition for this effect is the anisotropic emission<br />
of γ’s from that specific level. The corresponding nucleus must be polarized<br />
or at least aligned, which means the M-sublevels differ in their population<br />
probability. The measurement of <strong>PAC</strong> requires the preparation of specific<br />
probes and the application of very fast timing measurement methods.
Fast<br />
Preamp 1<br />
CFD 1<br />
Preamp 1<br />
Main Amp<br />
1<br />
TSCA<br />
Computer<br />
Det 1<br />
Delay<br />
Source<br />
Det 2<br />
HV<br />
Power<br />
Supply<br />
Coincidence<br />
Gate<br />
TAC<br />
Canberra<br />
Multiport II<br />
Det 2<br />
Changeable<br />
Preamp 2<br />
Main Amp<br />
2<br />
TSCA<br />
Delay<br />
Fast<br />
Preamp 2<br />
CFD 2
<strong>Perturbed</strong> <strong>Angular</strong> <strong>Correlation</strong> (<strong>PAC</strong>) : Required Knowledge<br />
‣ Gam<br />
‣ Tun<br />
‣ Comp<br />
‣ Gei<br />
‣ Comp<br />
‣ Int<br />
‣ Bet<br />
‣ TRI<br />
‣ Principles of<br />
‣ Principles of<br />
‣ What ?<br />
‣ What?<br />
‣ Tech<br />
‣ Comp<br />
‣ Principles of
<strong>Perturbed</strong> <strong>Angular</strong> <strong>Correlation</strong> (<strong>PAC</strong>) : Tasks and Goals<br />
‣ Set-up<br />
‣ Produce<br />
‣ Set-up<br />
‣ Determine<br />
‣ Determine<br />
‣ Determine energy<br />
‣ Determine the<br />
‣ Measure energy<br />
‣ Determine<br />
‣ Compare energy<br />
WARNINGS<br />
‣ Be careful.<br />
‣ Shut down<br />
‣ Never touch<br />
‣ Remove source after measurement
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