Perturbed angular correlation: Difference between revisions

Revision as of 18:28, 26 November 2019

Revision as of 22:47, 26 November 2019

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[[File:Pacaufbau.png|thumb|right|Instrumental setup of detectors around the probe.]]

[[File:Energywiki.png|thumb|right|Energy spectrum of ¹⁴⁹Gd with energy windows for start and stop.]]

In the typical PAC spectrometer, a setup of four 90° and 180° planar arrayed detectors or six octahedral arrayed detectors are placed around the radioactive source sample. The detectors used are scintillation crystals of BaF₂ or NaI. For modern instruments today mainly LaBr₃:Ce or CeBr₃ are used. Photomultipliers convert the weak flashes of light into electrical signals generated in the scintillator by gamma radiation. In classical instruments these signals are amplified and processed in logical AND/OR circuits in combination with time windows the different detector combinations (for 4 detectors: 12, 13, 14, 21, 23, 24, 31, 32, 34, 41, 42, 43) assigned and counted. Modern digital spectrometers use digitizer cards that directly use the signal and convert it into energy and time values ​​andand store them on hard drives. These are then searched by software for coincidences. Whereas in classical instruments, "windows" limiting the respective γ-energies must be set before processing, this is not necessary for the digital PAC during the recording of the measurement. The analysis only takes place in the second step. In the case of probes with complex cascades, this makes it makes it possible to perform a data optimization or to evaluate several cascades in parallel, as well as measuríng different probes simultaneously. The resulting data volumes can be between 60 and 300 GB per measurement.

== Sample materials ==