At the n_TOF experiment at CERN a dedicated single-crystal chemical vapor deposition (sCVD) Diamond Mosaic-Detector has been developed for (n,α) cross-section measurements. The detector, ...characterized by an excellent time and energy resolution, consists of an array of 9 sCVD diamond diodes. The detector has been characterized and a cross-section measurement has been performed for the 59Ni(n,α)56Fe reaction in 2012. The characteristics of the detector, its performance and the promising preliminary results of the experiment are presented.
•A large-area detector of 3 ×3 sCVD diamonds was built for (n, α) measurements.•The 59Ni(n, α)56Fe cross-section was measured successfully at n_TOF/CERN.•The energy resolution of the detector meets the expectations from simulations.•The reaction products during the measurement at n_TOF could clearly be separated.•The detector is suitable for (n, α) measurements in a heterogeneous beam.
The vast majority of children will undergo their first exposure to common allergenic foods at home. However, the first exposure may lead to clinical reactions. It has been proposed to introduce ...allergenic foods gradually into the diets of children at risk for food allergy, but no practical dietary advice has been devised. The aim of this study was to devise safe introduction schedules for common allergenic foods for use at home, based on the challenge doses as administered in double-blind, placebo-controlled food challenge (DBPCFCs) in children who were never exposed previously to these foods. Seventy-two DBPCFCs were performed in 63 children as a first known exposure. The incrementing challenge doses were converted into equivalent portions of these foods in their usual household form and incorporated in introduction schedules. The feasibility of the introduction scales was tested in parents of the children attending our clinic. Based on the results of the positive challenges (37) in which severe reactions did not occur, detailed introduction schedules and a reference photograph of the required increasing amounts of food were devised for use at home. Feasibility testing showed that, when using these introduction schedules, parents portioned the initial doses significantly lower than without detailed instructions. The introduction schedules and reference photograph provide information for parents to introduce the required amounts of allergenic foods in initial low doses at home. This is expected to improve the safety of this procedure.
Compilation of experimental uncertainty and covariance information in the EXFOR Library is discussed. Following the presentation of a brief history of information provided in the EXFOR Library, the ...current EXFOR Formats and their limitations are reviewed. Proposed extensions for neutron-induced reaction cross sections in the fast neutron region and resonance region are also presented.
A new experimental set-up for a simultaneous measurement of neutron induced capture and fission cross sections was designed, assembled and optimized. The measurements will be performed at GEel LINear ...Accelerator (GELINA) neutron time-of-flight facility in Belgium, where neutron cross sections can be measured over a wide energy range with high energy resolution. The fission events detector consists of a dedicated multi-plate high efficiency fission ionization chamber (IC). The γ-rays produced in capture reaction are detected by an efficient array of C6D6 scintillators. Fission γ-rays events are distinguished from capture events by the anticoincidence signals from the IC and the C6D6 detectors. For the undetected fission events a correction has to be applied with respect to the efficiency of the IC that should be high and known with a high precision. Another important issue is the good separation between fission-fragment (FF) and the high alpha pile-up. The performances of the IC during test experiments are presented, focusing in particular on the detection efficiency.
The MetroFission project, a Joint Research Project within the European Metrology Research Program, aims at addressing a number of metrological problems involved in the design of proposed Generation ...IV nuclear reactors. As part of this project a secondary neutron fluence standard is being developed and tested at the neutron time-of-flight facility GELINA of the JRCs Institute for Reference Materials and Measurements. Such a secondary standard will help to arrive at the neutron cross section measurement uncertainties required for the design and safety assessment of new generation power plants and fuel cycles. Such a neutron fluence device contains targets for which the neutron induced cross section is considered to be a standard. A careful preparation and characterization of these samples is an essential part of the development of the secondary standard. In this framework a set of
235
U targets has been produced by vapour deposition of UF
4
on aluminium backings by IRMMs target preparation laboratory. These targets have been characterized for both their total mass and mass distribution over the sample area.
Neutron elastic scattering measurements were carried out at the nELBE neutron time-of-flight facility at a 6 m flight path. Energies below 2 MeV were studied using a setup consisting of eight ...6Li-glass detectors placed at nominal angles of 15∘ and 165∘ with respect to the incident neutron beam. A deuterated polyethylene sample with 99.999% enrichment in deuterium was used. These angles were chosen since an earlier study showed that the ratio of the differential cross section at these angles is the most sensitive to differences in evaluated files and model calculations. Accurate 165∘/15∘ angle ratios were obtained. Above 1 MeV these are somewhat larger than given by ENDF/B-VII. Simultaneously the early day experiments using a proportional counter to infer angular distributions from deuterium recoil pulse height distributions are being studied through a new experiment with such a device at the Physikalisch-Technische Bundesanstalt (PTB). At 500 keV this experiment favors ENDF/B-VII over JENDL-4.0, while at lower energies agreement with the data is similar.
Studies for advanced reactor systems such as sodium-cooled fast reactors designed for recycling of high level waste, accelerator driven systems for transmutation, and systems envisioning the use of ...the Th/U fuel cycle impose tight requirements on nuclear data for accurate predictions of their operation and safety characteristics. Among the identified needs established by sensitivity studies, neutron inelastic scattering on the main structural materials and actinides and some (n,xn) cross sections for actinides feature prominently. Prompt-gamma spectroscopy and time-of-flight techniques were used to measure (n,xnγ) cross-sections of interest. Experiments were performed at the GELINA neutron time-of-flight facility of IRMM. Results for 235U and 23Na are briefly recalled; pertaining theoretical discussions are mentioned to explain observations concerning 238U. The status of studies on 76Ge, Zr and Mo is also reported.
The OECD-NEA High Priority Request List (HPRL) is a point of reference to guide and stimulate the improvement of nuclear data for nuclear energy and other applications, and a tool to bridge the gap ...between data users and producers. The HPRL is application-driven and the requests are submitted by nuclear data users or representatives of the user’s communities. A panel of international experts reviews and monitors the requests in the framework of an Expert Group mandated by the NEA Nuclear Science Committee Working Party on International Nuclear Data Evaluation Cooperation (WPEC). After approval, individual requests are classified to three categories: high priority requests, general requests, and special purpose requests (e.g., dosimetry, standards). The HPRL is hosted by the NEA in the form of a relational database publicly available on the web. This paper provides an overview of HPRL entries, status and outlook. Examples of requests successfully completed are given and new requests are described with emphasis on updated nuclear data needs in the fields of nuclear energy, neutron standards and dosimetry.
The n_TOF facility at CERN has been designed for the measurement of neutron capture, fission and (
n
,
×
n
) cross-sections with high accuracy. This requires a flexible and—due to the high ...instantaneous neutron flux—almost dead time free data acquisition system. A scalable and versatile data solution has been designed based on 8-bit flash-ADCs with sampling rates up to 2
GHz and 8
Mbyte memory buffer. The software is written in C and
C
++
and is running on PCs equipped with RedHat Linux.
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