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Wisshak, K.; Voß, F.; Käppeler, F.; Reffo, G.

doi:10.1103/physrevc.42.1731

Cited by 44 publications

(68 citation statements)

References 35 publications

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“…[1,2,14). In the present experiment most of the uncertainties are very similar to those of the samarium cross sections [2).…”

Section: Discussion Of Uncertaintiessupporting

confidence: 79%

“…Since the experimental method has been published in detail [1,2,13,14], only a more general description is given here, complemented with the specific features of the present measurement. Neutrons were produced via the 7 Li(p,n) 7 Be reaction by bombarding metallic Li targets with the pulsed proton beam of the Karlsruhe 3.75 MV Van de Graaff accelerator.…”

Section: Experimental Methodsmentioning

confidence: 99%

“…The data analysis was carried out analoguously to the procedure described previously [1,2,14). All events stored on dat tape were sorted into two-dimensional spectra containing 128 sum energy versus 4096 TOF channels according to various event multiplicities (Evaluation 1).…”

Section: Capture Cross Sectionsmentioning

confidence: 99%

“…7 The fraction of unobserved capture events, f, and the correction factor F 1 were calculated as described in detail in Ref. [14]. The required input for this calculation are the individual neutron capture cascades and their relative contributions to the total capture cross section as well as the detector efficiency for monoenergetic [-rays in the energy range up to 10 MeV.…”

Section: Capture Cross Sectionsmentioning

confidence: 99%

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Stellar neutron capture cross sections of the Gd isotopes

Wisshak¹,

Voß²,

Käppeler³

et al. 1995

Phys. Rev. C

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The neutron capture cross sections of 152 Gd, 154 Gd, 155 Gd, 156 Gd, 157 Gd, and 158 Gd were measured in the energy range from 3 to 225 keV at the Karlsruhe 3.75 MV Van de Graaff accelerator. Neutrons were produced via the 7 Li(p,n)1Be reaction by bombarding metallic Li targets with a pulsed protori beam. Capture events were registered with the Karlsruhe 47r Barium Fluoride Detector, which was improved by replacing crystals with high a background and by introducing a pierced crystal at zero degrees with respect to the beam axis. These changes resulted in a significantly increased efficiency for capture events. The main experimental problern was that the samples of the two s-only isotopes 152 Gd and 154 Gd showed only relatively low enrichment, but the spectroscopic quality of the BaF 2 detector allowed to determine the resulting corrections for isotopic impurities reliably. The cross section ratios could be determined with an overall uncertainty of typically 1%, an improvement by factors of five to ten compared to existing data. Severe discrepancies were found with respect to previous results. Maxwellian averaged neutron capture cross sections were calculated forthermal energies between kT = 10 keV and 100 keV. The new stellar cross sections were used for an updated analysis of the s-process reaction flow in the mass region between samarium and gadolinium, which is characterized by branchings at 151 Sm, 154 Eu, and 155 Eu. With the classical approach, the s-process temperature could be constrained corresponding to a range of thermal energies between kT=28 ke V and 33 keV. The 152 Gd production in low mass starswas found to depend strongly on the neutron freeze-out at the end of the heliumshell burning episodes.

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“…[1,2,14). In the present experiment most of the uncertainties are very similar to those of the samarium cross sections [2).…”

Section: Discussion Of Uncertaintiessupporting

confidence: 79%

Section: Experimental Methodsmentioning

confidence: 99%

Section: Capture Cross Sectionsmentioning

confidence: 99%

Section: Capture Cross Sectionsmentioning

confidence: 99%

See 2 more Smart Citations

Stellar neutron capture cross sections of the Gd isotopes

Wisshak¹,

Voß²,

Käppeler³

et al. 1995

Phys. Rev. C

Self Cite

View full text Add to dashboard Cite

show abstract

“…Sinee the experimental method has been published in detail [1] [3] [5] [23], only a more general description is given here, complemented with the specific features of the present measurement. Neutrons were produced via the 7 Li(p,n?Be reaction by bombarding metallic Li targets with the pulsed proton beam of the Karlsruhe 3.…”

Section: Experimental Methodsmentioning

confidence: 99%

Stellar neutron capture cross sections of the Ba isotopes

et al. 1994

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The neutron capture cross sections of 134 Ba, 135 Ba, 136 Ba, and 137 Ba were measured in the energy range from 5 to 225 keV at the Karlsruhe 3.75 MV Van de Graaff accelerator. Neutrons were produced via the 7 Li(p,nfBe reaction by bombarding metallic Li targets with a pulsed proton beam. Capture events were registered with the Karlsruhe 47r Barium Fluoride Detector. Several runs have been performed under different experimental conditions to study the systematic uncertainties, which resulted mainly from the large ratios of total to capture cross sections of up to 400. The cross section ratios were determined with an overall uncertainty of "'3%, an improvement by factors of five to eight compared to existing data. Severe discrepancies were found with respect to previous results. Maxwellian averaged neutron capture cross sections were calculated for thermal energies between kT = 10 ke V and 100 ke V. These stellar cross sections were used in an s-process analysis. For the s-only isotopes 134 Ba and 136 Ba the Nsratio was determined to 0.875±0.025. Hence, a significant brauehing of the s-process path at 134 Cs can be claimed for the first time, in cantrast to predictions from the classical approach. This brauehing yields information on the s-process temperature, indicating values araund T 8 = 2. The new cross sections arealso important for the interpretation of barium isotopic anomalies, which were recently discovered in SiC grains of carbonaceous chondrite meteorites. Tagether with the results from previous experiments on tellurium and samarium, a general improvement of the Nssystematics in the mass range A = 120 to 150 is achieved. This allows for a more reliable separation of s-and r-process yields, resulting in an improved assignment of the respective contributions to eiemental barium that is required for comparison with stellar observations. ZUSAMMENFASSUNG

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