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- Oberstedt, Andreas, et al.
(författare)
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Recent results on the neutron-induced fission cross-section of 231Pa
- 2005
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Ingår i: Proceedings of the 3rd international workshop on nuclear fission and fission-product spectroscopy. - : American Institute of Physics. - 0735402884 ; , s. 27-30
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Konferensbidrag (refereegranskat)abstract
- The cross-section for the neutron-induced fission of 231Pa has recently been measured from the threshold to En = 3.5 MeV. The experimental results are described in terms of extended statistical model calculations.
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| 2. |
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| 3. |
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| 4. |
- Oberstedt, Stephan, et al.
(författare)
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Research on isomer decay with the NEPTUNE spectrometer
- 2008
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Ingår i: ND-2007 International Conference on Nuclear Data for Science and Technology, Nice, France. - Les Ulis Cedex A, France : EDP Sciences. - 9782759800902 - 9782759800919 ; , s. 53-56
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Konferensbidrag (refereegranskat)abstract
- A new spectrometer has been built at the EC-JRC IRMM to investigate isomer decay in the millisecond range and activation cross sections of isotopes, where isomeric states exist and are populated. The spectrometer is equipped with high-resolution gamma-ray detectors and an ionisation chamber for the measurement of charged particles, e.g., fission fragments. NEPTUNE provides pulsed quasi mono-energetic neutrons at pulse repetition frequencies up to 5 kHz and tuneable neutron pulse widths ranging from 10 µs into the ms-region. For this purpose a beam chopper based on a parallel-plate capacitor has been integrated into the accelerator beam line in order to deflect the charged-particle beam onto a tantalum beam dump. First research has been performed with the NEPTUNE spectrometer dedicated to the shape isomer search in the odd-A uranium isotopes 235U, 237U and 239U. In further experiments the population of long-lived spin isomers was investigated.
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| 5. |
- Oberstedt, Stephan, et al.
(författare)
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Shape isomers : a key to fission barriers
- 2008
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Ingår i: Seminar on Fission VI, Corsendonk Priory, Belgium, September 18-21, 2007. - : WORLD SCIENTIFIC. - 9789812791061 ; , s. 233-240
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Konferensbidrag (refereegranskat)abstract
- Quantitative predictions of fission product yields are relevant for the reliable operation of different modern nuclear applications. This concerns the realistic characterizations of the radio-toxicity of the fuel elements after the envisaged extended irradiation, as well as sub-critical assemblies, where the number of delayed neutrons from minor actinides is determined by the characteristic emission yields of the corresponding so-called pre-cursor isotopes. However, to be able to make more reliable quantitative predictions of fission characteristics requires the better understanding of the fission process itself. For this purpose a better knowledge about the distinct structure of the nuclear energy landscape around the fission barrier is indispensable. In particular, the question should be answered, whether the fission barrier is either double- or triple-humped or even multi-humped as been proposed within the multi-modal neck rupture model. Despite quite some effort based on different experimental techniques and theoretical approaches, this question remains still unanswered. There is still no consistent picture of the fission barrier available and hence, different sets of barrier parameters are in use, unable to describe the different observed phenomena in a coherent way. With the systematic investigation of shape isomer population, its decay modes as well as the branching ratio, precise information can be obtained to resolve the puzzling situation. The experimental approach will be discussed and results from first experiments presented.
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