Stellar Neutron Capture on Promethium: Implications for the<i>s</i>‐Process Neutron Density

Reifarth, R.; Arlandini, C.; Heil, M.; Käppeler, F.; Sedyshev, P.; Mengoni, A.; Herman, M.; Rauscher, T.; Gallino, R.; Travaglio, C.

doi:10.1086/344718

Cited by 72 publications

(62 citation statements)

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“…For suppression of the still dominant background from the decay of 147 Pm (t 1/2 = 2.62 yr), one had to go a step further, using the eight-fold geometry of the two Clover detectors for the coincident detection of the (915+550) keV cascade in the decay of 148 Pm. In this way, the dominant 40 K background could be su ciently reduced to determine the stellar cross section of 147 Pm with an uncertainty of 14%, leading to a mean neutron density of n n = 4.9 ± 0.6 cm 3 [44].…”

Section: Branchings As Diagnostic Tools: 147 Pmmentioning

confidence: 99%

Stellar neutron capture rates – key data for thesprocess

Käppeler

2013

EPJ Web of Conferences

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Abstract. Neutron reactions are responsible for the formation of the elements heavier than iron. The corresponding scenarios relate to the He-and C-burning phases of stellar evolution (s process) and to supernova explosions (r and p processes). The s process, which is characterized by low neutron densities, operates in or near the valley of stability and has produced about half of the elemental abundances between Fe and Bi in the solar system and in the Universe. Because the s abundances are essentially determined by the (n, ) cross sections along the reaction path, accurate neutron data constitute the key input for s process studies. Important constraints for the physical conditions at the stellar sites can be inferred by comparison of the abundance patterns from current s-process models with solar system material or presolar grains. The experimental methods for the determination of stellar (n, ) rates are outlined at the example of recent cross section measurements and remaining quests will be discussed with respect to existing laboratory neutron sources and new developments.

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Section: Branchings As Diagnostic Tools: 147 Pmmentioning

confidence: 99%

Stellar neutron capture rates – key data for thesprocess

Käppeler

2013

EPJ Web of Conferences

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“…At higher energies, the detection of the stronger lines at 1027 and 1205 keV was limited by the lower detection efficiency and natural background. This problem could be overcome by making use of the eight-fold segmentation of the Ge clover array [51]. Requiring coincidence detection of the 298/1027 keV cascade transitions provided excellent background suppression.…”

Section: Experiments On 60 Fe: Technological Frontiersmentioning

confidence: 99%

Stellar neutron capture rates and thesprocess

Käppeler

2012

EPJ Web of Conferences

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Abstract. Neutron reactions are responsible for the formation of the elements heavier than iron. The corresponding scenarios relate to helium burning in Red Giant stars (s process) and to supernova explosions (r and p processes). The s process, which operates in or near the valley of β-stability, has produced about half of the elemental abundances between Fe and Bi. Accurate (n, γ) cross sections are the essential input for s process studies, because they determine the abundances produced by that process. Following a brief summary of the neutron capture processes, the focus will be set on the s process in massive stars, where the role of reliable cross section information is particularly important. Eventually, the intriguing aspects of the origin of 60 Fe will be addressed. Attempts to determine the stellar cross section of that isotope are pushing experimental possibilities to their limits and present a pertinent challenge for future facilities.

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“…The last setup at FZK for ToF measurements had a flight path of about 80 cm and about 10 4 neutrons s −1 cm −2 at the sample position with proton currents of ≈2 µA (Wisshak et al 1990;Reifarth et al 2002). During activation measurements (DC) 10 9 s −1 at proton currents of ≈100 µA are typically produced (Reifarth et al 2003).…”

Section: Franzmentioning

confidence: 99%

“…Depending on the actual neutron density during the s process, the 'line of interest' is closer to or farther away from the valley of stability. In a recent estimate the neutron density within the classical s-process model (Käppeler et al 1989) was estimated to be n n = 4.94(+0.60, −0.50) × 10 8 cm −3 (Reifarth et al 2003). Figure 1 shows a summary of the neutron-capture and β − decay times for radioactive isotopes on the neutron rich side of the valley of stability, under the condition that the classical neutron capture occurs than the terrestrial β − decay.…”

Section: Introductionmentioning

confidence: 99%