JAEA-Conf 2011-002 - 日本原子力研究開発機構

Fig. 1 A conceptural picture of the surrogate reaction. This particular example shows
a way to determine neutron cross sections of short-lived nucleus 239 U (T1/2=23 min.) by
populating the same compound nucleus 240 U via 238 U( 18 O, 16 O) 240 U reaction.
These problems are fundamental in nature, so reseach from the viewpoint of nuclear
physics is necessary to understand the underlying physics and to really yield the desired
neutron cross section data by the surrogate method.
In this paper, a JAEA-based activity on the installation of equipments for the
surrogate method and its physical justification will be explained briefly below.
2. Strategy
By using the surrogate method, we plan to determine primalily 1) fission cross
sections, 2) capture cross sections, and subsequently 3) fission-fragment mass
distributions and 4) number of prompt neutrons per fission, of minor actinides. Also,
capture cross sections of LLFPs and some nuclei relevant to the s-process nucleosynthesis
are in our scope. Therefore, our detection system must involve i) charged-particle
detercters to identify the populated nuclear species and their excitation energies, ii)
fission fragment detectors, iii) -ray detectors and iv) neutron counters. The system is
Fig.2 A schematic layout of the surrogate
detection system under plan
JAEA-Conf 2011-002
Fig.3 Charged-particle spectra obtained by a
silicon E-E deterctor