Program - Brookhaven National Laboratory

DB 5 5:00 PM
Thermal Neutron Capture Cross-Section Measurements of 50 Ti, 51 V and 98 Mo
V. H. Tan
Vietnam Agency for Radiation and Nuclear Safety (VARANS), 70-Tran Hung Dao, Ha Noi, Vietnam
P. N. Son
Nuclear Research Institute, 01-Nguyen Tu Luc, Dalat, Vietnam
Thermal neutron capture cross sections for 50 Ti, 51 V and 98 Mo were measured by the activation method
using the filtered thermal neutron beam at the Channel No.2 of Dalat research reactor. An optimal
composition of Si and Bi single crystals has been used as neutron filters to create the high purity filtered
thermal neutron beam with Cadmium ratio up to 700. The cyclic activation mode was applied for the cases
of 50 Ti and 51 V because of short half lives of their neutron capture products. The induced activities in the
irradiated samples were measured by a high resolution HPGe digital gamma-ray spectrometer. The present
results of thermal neutron capture cross sections for 50 Ti, 51 V and 98 Mo have been obtained relative to
the reference values of 197 Au standard, with σ0 = 98.65 ± 0.09 barn. The necessary correction factors for
gamma-ray true coincidence summing, and thermal neutron self-shielding effects were taken into account
in the determinations. The present results are discussed and compared with previous measurements.
Corresponding author: P. N. Son
DB 6 5:15 PM
Measuring Light-Ion Production and Fission Cross Sections Versus Elastic np-Scattering at
the Upcoming NFS Facility
Kaj Jansson, Cecilia Gustavsson, Anders Hjalmarsson, Stephan Pomp, Giovanni Scian, Diego Tarrio
Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden
Alexander Prokofiev
The Svedberg Laboratory, Uppsala University, Uppsala, Sweden
The Medley setup has been used in many measurements at the Svedberg Laboratory (TSL) in Uppsala
mainly with a quasi-mono-energetic neutron beam at 96 and 175 MeV [1,2]. Medley has eight detector
telescopes each consisting of two silicon detectors and a CsI(Tl) detector at the back providing ∆E-∆E-E
data. The whole telescope setup is rotatable and can be made to cover any angle. Medley is now planned
to be moved to and used at the new, currently under construction, neutron facility NFS [3] in Ganil
where measurements of light-ion production as well as fission cross-sections are planned at 1-40 MeV. The
light-ion production plays an important role in e.g. single-events effects in electronics. The 238 U fission is
particularly important as a standard for high-energy neutron monitoring but also in nuclear power related
areas and to understand the fission phenomena itself. At low and high neutron energies these cross-sections
are fairly well known but at intermediate energies, especially above 20 MeV, there are large discrepancies
among reported cross-sections. Our measurements will thus provide data in a much needed energy region.
Our main goal is measuring U-238 and Th-232. However, we plan to extend the measurements also to
other actinides. The fission cross-section is planned to be measured relative the standard np-cross-section
by simultaneously measure protons in the forward angles and fission fragments in the backwards angles.
The energy dependent anisotropy factor can also be measured. To be able to do these new measurements
at NFS, which will have a high intensity white neutron beam coming from a full stop Be-target, Medley
needs to detect the reaction products with a high temporal resolution providing the ToF of the primary
neutron. In this paper we discuss the design of the Medley upgrade and experiments along with simulations
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