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- Pandemonium_effect abstract "The Pandemonium effect is a problem that may appear when high resolution detectors (usually germanium detectors) are used in beta decay studies. It can affect the correct determination of the feeding to the different levels of the daughter nucleus. It was first introduced in 1977 paper by J.C. Hardy et al.The general picture of the problem is schematically this: when a parent nucleus decays into its daughter, the energy levels of the daughter can be populated in two ways: either by direct feeding from the decay (Iβ), or by de-excitation of higher energy levels also beta-populated in the decay (ΣIi).When one of these levels decays, the total gamma rays emitted by the level (IT) should be equal to the sum of these two contributions (neglecting internal conversion). As the magnitude that can be measured are the gamma intensities (ΣIi and IT), the beta feeding (that is, how many times a level is populated by direct feeding) has to be extracted indirectly by subtracting the contribution from de-excitations of higher energy levels (ΣIi) to the total gamma intensity that leaves the level (IT), that is: Iβ = IT - ΣIi. But sometimes the daughter nucleus has a large Q value, allowing the existence of many levels. This means that the total feeding will be fragmented, as it will spread over all of them (with a certain distribution given by the strength, the level densities, the selection rules, etc.). Then, the gamma intensity emitted from the less populated levels will be weak, and it will be weaker as we go to higher energies where the level density can be huge. Also, the energy of the gammas de-excitating this high density level zone can be high.Measuring these gamma rays with high resolution detectors may present two problems: First, these detectors have a very low efficiency of the order of 1-5%, and will be blind to a weak radiation in most of the cases. Second, the efficiency curve drops to very low values as it goes to higher energies, starting from energies of the order of 1-2 MeV. This means that most of the information coming from the high energy gamma rays will be lost.The consequence of these two effects is that much of the beta feeding at high excitation energy is not detected so less ΣIi is subtracted from the IT, and the levels are incorrectly assigned more Iβ than they really have. When this happens, the low-lying energy levels are the more affected ones. Some of the level schemes of nuclei that appear in the nuclear databases suffer from this Pandemonium effect and are not reliable until better measurements are done. The knowledge of the beta feeding, (Iβ) is important for different applications, like for example, the calculation of the residual heat in nuclear reactors.One possible solution is to use a calorimeter like the Total Absorption Spectrometer (TAS). It has been shown that even with a high efficiency array of Germanium detectors in a very close geometry (the CLUSTER CUBE), about 57% of the total B(GT) observed with the TAS technique is lost.".
- Pandemonium_effect thumbnail Schematic_diagram_showing_the_Pandemonium_effect.png?width=300.
- Pandemonium_effect wikiPageExternalLink 94.
- Pandemonium_effect wikiPageID "30831718".
- Pandemonium_effect wikiPageRevisionID "606759285".
- Pandemonium_effect above "Pandemonium effect alt=Schematic diagram showing how the Pandemonium effect can affect the results in an imaginary decay to a nucleus that has 3 levels. If this effect is large, feeding to high lying levels is not detected, and more beta feeding is assigned to the low-lying energy levels.".
- Pandemonium_effect hasPhotoCollection Pandemonium_effect.
- Pandemonium_effect name "Pandemonium effect".
- Pandemonium_effect subheader "Schematic diagram showing how the Pandemonium effect can affect the results in an imaginary decay to a nucleus that has 3 levels. If this effect is large, feeding to high lying levels is not detected, and more beta feeding is assigned to the low-lying energy levels.".
- Pandemonium_effect subject Category:Nuclear_physics.
- Pandemonium_effect comment "The Pandemonium effect is a problem that may appear when high resolution detectors (usually germanium detectors) are used in beta decay studies. It can affect the correct determination of the feeding to the different levels of the daughter nucleus. It was first introduced in 1977 paper by J.C.".
- Pandemonium_effect label "Pandemonium effect".
- Pandemonium_effect sameAs m.0gh8fpf.
- Pandemonium_effect sameAs Q7130580.
- Pandemonium_effect sameAs Q7130580.
- Pandemonium_effect wasDerivedFrom Pandemonium_effect?oldid=606759285.
- Pandemonium_effect depiction Schematic_diagram_showing_the_Pandemonium_effect.png.
- Pandemonium_effect isPrimaryTopicOf Pandemonium_effect.
