WISSHAK , K.

The (n,γ) reaction of the radioactive isotope 93Zr has been measured at the n-TOF high-resolution time-of-flight facility at CERN. Resonance parameters have been extracted in the neutron energy range up to 8 keV, yielding capture widths smaller (14%) than reported in an earlier experiment. These results are important for detailed...

The (n,γ) cross section of 96Zr has been investigated at the CERN n-TOF spallation neutron source. High-resolution time-of-flight measurements using an enriched ZrO2 sample allowed us to analyze 15 resonances below 40 keV with improved accuracy. On average, the capture widths were found to be 25% smaller than reported in earlier experiments. If...

The neutron capture cross sections for Zr isotopes have important implications in nuclear technologies as well in the field of nuclear astrophysics. The innovative features of the n_TOF CERN facility allowed for an accurate determination of the capture cross sections for these isotopes. The preliminary results of the measurements show...

The neutron Time-of-Flight facility at CERN was built to measure the neutron capture and fission cross sections. A short description of the facility, the detectors and the data analysis techniques will be illustrated. A short review of the preliminary results on the fission cross sections is presented together with the implications in...

The neutron-induced fission cross section of 234U has been measured at the CERN n-TOF facility relative to the standard fission cross section of 235U from 20 keV to 1.4 MeV and of 238U from 1.4 to 200 MeV. A fast ionization chamber (FIC) was used as a fission fragment detector with a detection efficiency of no less than 97%. The high...

The neutron capture cross sections of the Zr isotopes are relevant to studies in nuclear structure, nuclear astrophysics, and nuclear technology. The valence neutron of 91Zr with respect to the neutron magic nucleus 90Zr has interesting implications for the statistical analysis in the proximity of shell closures. In stellar nucleosynthesis, the...

Because the relatively small neutron capture cross sections of the zirconium isotopes are difficult to measure, the results of previous measurements are often not adequate for a number of problems in astrophysics and nuclear technology. Therefore, the 92Zr(n,γ) cross section has been remeasured at the CERN n-TOF facility, providing a set of...

The neutron capture cross sections of the Zr isotopes play an important role in nucleosynthesis studies. The s-process reaction flow between the Fe seed and the heavier isotopes passes through the neutron magic nucleus Zr90 and through Zr91,92,93,94, but only part of the flow extends to Zr96 because of the branching point at Zr95. Apart from...

The neutron capture cross sections of the Zr isotopes have important implications in nuclear astrophysics and for reactor design. The small cross section of the neutron magic nucleus 90Zr, which accounts for more than 50% of natural zirconium represents one of the key isotopes for the stellar s-process, because it acts as a bottleneck in the...

The capture cross section of the 139La has been measured relative to 197Au standard at n_TOF. We provide here a short description of the experimental apparatus and of the data analysis procedures. The extracted resonance parameters allow to calculate the fundamental nuclear quantities such as average spacing l=0 = 268 ± 22 eV, l=1 < 250 eV...

The radioactive decay of 187Re → 187Os (t 1/2 = 43 Gyr) is suited for dating the onset of heavy-element nucleosynthesis. The radiogenic contribution to the 187Os abundance is the difference between the natural abundance and the corresponding s-process component. This component can be obtained via the well-established σN systematics using the...

The neutron Time of Flight (n_TOF) facility at CERN is a source of a wide-range (1 eV

The accurate knowledge of the 151Sm(n,γ) cross section has important implications for the nuclear technologies as well as for fundamental studies. Due to its radioactivity, the only experimental data available on 151Sm were derived from a transmission measurement [1]. Nowadays thanks to the innovative features of neutron time-of-flight facility...

A series of measurements of 237Np fission cross section have been performed at the CERN spallation neutron facility n_TOF which covers a wide energy range from 1 eV up to 250 MeV. A fast ionization chamber (FIC) was used as a fission fragment detector with registration efficiency of not less than 97 %. Particular attention was paid to correct...

The precise determination of the neutron capture cross sections of 186Os and 187Os is important to define the s-process abundance of 187Os at the formation of the solar system. This quantity can be used to evaluate the radiogenic component of the abundance of 187Os due to the decay of the unstable 187Re (t1/2=41.2 Gyr) and from this to infer...

Neutron resonance analyses have been performed for the capture cross sections of 186Os, 187Os, and 188Os measured at the n-TOF facility at cern. Resonance parameters have been extracted up to 5, 3, and 8 keV, respectively, using the sammy code for a full R-matrix fit of the capture yields. From these results average resonance parameters were...

Accurate and reliable neutron capture cross section data for actinides are necessary for the proper design, safety regulation and precise performance assessment of transmutation devices such as Fast Critical Reactors or Accelerator Driven Systems. In particular, the neutron capture cross sections of 237Np, 240Pu and 243Am play a key role in the...

Accurate and reliable neutron-capture cross-section data for actinides are necessary for the proper design, safety regulation, and precise performance assessment of transmutation devices such as Fast Critical Reactors or Accelerator Driven Systems. In particular, the neutron-capture cross sections of 237Np, 240Pu, and 243Am play a key role in...

The neutron-induced fission cross section of 237 Np was experimentally determined at the high-resolution and high-intensity facility n TOF , at CERN, in the energy range 100 keV to 9 MeV, using the 235 U ( n,f )and 238 U ( n,f ) cross section standards below and above 2 MeV, respectively. A fast ionization chamber was used in order to detect...

All the stable lead isotopes and 209Bi have been recently measured at n_TOF [1] (CERN) in the range from 1 eV up to 1 MeV, using an optimized experimental setup. A set of two homemade C6D6 detectors with carbon-fibre canning was designed to greatly reduce the sensitivity to scattered neutrons. Surrounding elements like the sample holder and the...

During the 2004 campaign, the n_TOF collaboration measured neutron fission cross sections for 233U, 241,243Am, 245Cm, as well as the fission standards 235,238U, using a sealed Fission Ionization Chamber (FIC). The setup included a total of 16 targets and 18 electrodes mounted together in a 50-cm length chamber, allowing the measurements of all...

We have measured the neutron capture cross sections of the stable magnesium isotopes 24 ,25 ,26Mg in the energy range of interest to the s process using the neutron time-of-flight facility n-TOF at CERN. Capture events from a natural metal sample and from samples enriched in 25Mg and 26Mg were recorded using the total energy method based on C...

The nuclear resonance parameters and the capture cross section of the neutron magic isotope La139 have been measured relative to Au197 in the energy range of 0.6 eV to 9 keV at the neutron time-of-flight (n_TOF) facility at CERN. We describe the experimental apparatus and the data analysis procedures, which concerned mainly the efficiency...

A high-resolution measurement of the neutron-induced fission cross section of 234U and 237Np has been performed at the CERN Neutron Time-of-Flight facility. The cross sections have been determined in a wide energy range from 1 eV to 1 GeV using the evaluated 235U cross section as reference. In these measurements the energy determination for the...