Abstract. Numerous domains, in fundamental research as well as in applications, require the study of reactions induced by neutrons with energies from few MeV up to few tens of MeV. Reliable measurements also are necessary to improve the evaluated databases used by nuclear transport codes. This energy range covers a large number of topics like transmutation of nuclear waste, design of future fission and fusion reactors, nuclear medicine or test and development of new detectors. A new facility called Neutrons For Science (NFS) is being built for this purpose on the GANIL site at Caen (France). NFS is composed of a pulsed neutron beam for time-of-flight facility as well as irradiation stations for cross-section measurements. Neutrons will be produced by the interaction of deuteron and proton beams, delivered by the SPIRAL-2 linear accelerator, with thick or thin converters made of beryllium or lithium. Continuous and quasi-mono-energetic spectra will be available at NFS up to 40 MeV. In this fast energy region, the neutron flux is expected to be up to 2 orders of magnitude higher than at other existing time-of-flight facilities. In addition, irradiation stations for neutron-, proton-and deuteron-induced reactions will allow performing cross-section measurements by the activation technique. After a description of the facility and its characteristics, the experiments to be performed in the short and medium term will be presented.
In this work, we measure the hole mobility in the model polymer system poly(3-hexylthiophene-2,5-diyl) by using different measurement techniques. Our main purpose is to determine how the recently developed charge extraction by a linearly increasing voltage technique for metal–insulator–metal devices (MIM-CELIV) compares to other commonly used methods, such as space charge limited currents and time-of-flight. Our findings suggest that the MIM-CELIV technique gives a slightly lower mobility than the other techniques, which is understandable given that the method measures the mobility of relaxed charge carriers in the dark unlike, for example, time-of-flight where charge carriers are photogenerated. In addition, we scrutinize the accuracy and reliability of the techniques used, showing that differences in mobility smaller than a factor of two are not detectable unless statistics from many devices are available.
Abstract. The 6 Li(n,α) reaction cross-section is commonly used as a reference cross section. However, it is only considered a neutron standard up to 1 MeV. For higher energies, there are discrepancies of several per cents between recent measurements and evaluated data files. In order to extend and establish 6 Li(n,α) as a neutron standard above 1 MeV these discrepancies must be resolved. Our measurement at the GELINA facility at JRC-IRMM in Geel, Belgium is ongoing. We are using a double twin Frisch-grid setup to detect both α-particles from two 6 Li targets and fission products from two 235 U reference targets. Our targets have thick backings but are employed in pairs, one forward facing and one backward facing. In this way we still cover, in principle, a solid angle of 4π. We present some preliminary results showing that the existing cross-section data is well reproduced around the resonance at 240 keV. The final data taking will start in the beginning of 2016, when the GELINA facility goes online again after a few months of shut down.
Abstract. An investigation of the stopping efficiency of fission products, in the new ion guide designed for ion production through neutron-induced fission at IGISOL in Jyväskylä, Finland, has been conducted. Our simulations take into account the new neutron converter, enabling measurements of neutron-induced fission yields, and thereby provide estimates of the obtained yields as a function of primary proton beam current. Different geometries, targets, and pressures, as well as models for the effective charge of the stopped ions were tested, and optimisations to the setup for higher yields are suggested. The predicted number of ions stopped in the gas lets us estimate the survival probability of the ions reaching the downstream measurements stations.
The neutrons for science (NFS) facility is a component of SPIRAL-2, the new superconducting linear accelerator built at GANIL in Caen (France). The proton and deuteron beams delivered by the accelerator will allow producing intense neutron fields in the 100 keV-40 MeV energy range. Continuous and quasi-mono-kinetic energy spectra, respectively, will be available at NFS, produced by the interaction of a deuteron beam on a thick Be converter and by the 7Li(p,n) reaction on thin converter. The pulsed neutron beam, with a flux up to two orders of magnitude higher than those of other existing time-of-flight facilities, will open new opportunities of experiments in fundamental research as well as in nuclear data measurements. In addition to the neutron beam, irradiation stations for neutron-, proton- and deuteron-induced reactions will be available for cross-sections measurements and for the irradiation of electronic devices or biological cells. NFS, whose first experiment is foreseen in 2018, will be a very powerful tool for physics, fundamental research as well as applications like the transmutation of nuclear waste, design of future fission and fusion reactors, nuclear medicine or test and development of new detectors.
Abstract. This paper presents the ongoing analysis of two fission experiments. Both projects are part of the collaboration between the nuclear reactions group at Uppsala and the JRC-IRMM. The first experiment deals with the prompt fission neutron multiplicity in the thermal neutron induced fission of 235 U(n,f). The second, on the fission fragment properties in the thermal fission of 234 U(n,f). The prompt fission neutron multiplicity has been measured at the JRC-IRMM using two liquid scintillators in coincidence with an ionization chamber. The first experimental campaign focused on 235 U(n th ,f) whereas a second experimental campaign is foreseen later for the same reaction at 5.5 MeV. The goal is to investigate how the so-called sawtooth shape changes as a function of fragment mass and excitation energy. Some harsh experimental conditions were experienced due to the large radiation background. The solution to this will be discussed along with preliminary results. In addition, the analysis of thermal neutron induced fission of 234 U(n,f) will be discussed. Currently analysis of data is ongoing, originally taken at the ILL reactor. The experiment is of particular interest since no measurement exist of the mass and energy distributions for this system at thermal energies. One main problem encountered during analysis was the huge background of 235 U(n th ,f). Despite the negligible isotopic traces in the sample, the cross section difference is enormous. Solution to this parasitic background will be highlighted.
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