Study of (n,xng) reactions on 238U

Prompt-gamma spectroscopy and time-of-flight techniques were used to measure (n,xn gamma) cross-sections on several nuclei of interest for nuclear reactors. Experiments were performed at the GELINA facility which provides a pulsed white neutron beam of maximum energy about 20 MeV. Preliminary results concerning 238U will be presented. This work was supported by PACEN/GEDEPEONand by the European Commission within the Sixth Framework Programme through I3-EFNUDAT (EURATOMcontract no. 036434) and NUDAME (Contract FP6-516487), and within the Seventh Framework Programme through EUFRAT (EURATOM contract no. FP7-211499) and through ANDES (EURATOM contract no. FP7-249671).JRC.D.4-Standards for Nuclear Safety, Security and Safeguard

Measurement of Neutron Inelastic Scattering Cross Sections for 209Bi from Threshold up to 18 MeV

The interest in 209Bi, the only stable isotope of this element, originates from its proposed use in the spallation module and as moderator/coolant of an accelerator driven system (ADS). Inelastic scattering that constitutes 30% of the total neutron cross section of 209Bi is a major contributor to uncertainties in predicted ADS parameters. New data were obtained for production cross sections of 19 transitions up to about 18 MeV, incident energy. One transition was observed per excited level for the first 8 levels. From the measured gamma-ray production cross sections, total and level inelastic cross sections were deduced. The experiment was performed at GELINA, with a white neutron spectrum, at 200 m flight path length using the time-of-flight method. The gamma rays from the 209Bi(n,n/gamma )209Bi reaction were detected with two large volume HPGe detectors and the neutron flux was monitored with a multilayer 235U fission chamber. For the main transitions the inelastic cross section is given with an incident neutron energy resolution ranging from 1.1 keV at 1 MeV to 35.7 keV at 10 MeV within overall statistical error of less than 5%JRC.D.5-Neutron physic

Neutron inelastic scattering measurements for background assessment in neutrinoless double beta decay experiments

The inelastic scattering of neutrons on structural materials constitutes a major concern for the design of neutrinoless double beta decay experiments. We explore our neutron inelastic scattering data on 206Pb, 56Fe, 28Si, 24Mg, and 12C, searching for possible contributors to the background in the energy region where neutrinoless double beta decay signals would be produced.JRC.D.4-Standards for Nuclear Safety, Security and Safeguard

Data Acquisition with a Fast Digitizer for Large Volume HPGe Detectors

A 12-bits and 420 MSample/s waveform digitizer was used with large volume High Purity Germanium (HPGe) detectors for measurements of gamma-ray production cross-section from inelastic neutron scattering. For these time-of-flight measurements at the GELINA white neutron source, the use of a fast digitizer significantly increases the efficiency compared with a conventional data-acquisition system. First, the pulse processing time required to obtain the amplitude with high resolution, is significantly reduced so that pulse pile-up with the prompt gamma-burst is eliminated for neutron-induced events. Second, an improved time response is obtained for which the amplitude and rise time dependence is strongly reduced compared to that of a conventional constant fraction discriminator. Excellent energy and time resolution is obtained with algorithms suitable for on-line signal processing, so that data storage is under control. Bench tests are presented that compare methods of signal processing. For the best method, the data acquisition system based on the fast digitizer was tested during measurements of gamma-production cross-sections for 206Pb and 208Pb. A direct comparison was made with results obtained with conventional electronics operated in parallel.JRC.D.5-Neutron physic

Neutron Inelastic Scattering Experiments using GAINS at GELINA

A considerable effort was dedicated during last years to the upgrade of the setup used for measurements of neutron inelastic cross sections at GELINA. The completely renewed setup called GAINS (Gamma Array for Inelastic Neutron Scattering) is now operational at a 200 m flight path of the white neutron source GELINA. GAINS consists of eight high-efficiency HPGe detectors placed at 110o and 150o in close geometry around the sample. The acquisition system is based on four 12 bits, 420 MHz digitizers with two input channels each. The reliability of the system was already proven for 206Pb data (based on a comparison with a former measurement) and is now under further investigation via a 56Fe measurement. The present contribution describes the new system together with the analysis method. It further emphasizes the difficulties of a highly accurate 56Fe(n, n¿¿) measurement and shows the preliminary available results.JRC.D.5-Neutron physic

Cross Sections for Neutron Inelastic Scattering on 28Si

A measurement of the neutron inelastic cross sections on 28Si was performed at the GELINA (Geel Linear Accelerator) white neutron source of EC-JRC-IRMM, Belgium. The GAINS (Gamma Array for Inelastic Neutron Scattering) detection system was used to determine the production cross sections of the most intense gamma rays. The neutron flux was monitored with a 238U fission chamber. Using the level scheme from the ENSDF database, the total inelastic cross section and the level production cross section of the first levels were determined. A few gamma production cross sections from the (n,p) and (n,alpha) channels were also measured. The results are compared with previous existing data and with the results of theoretical calculations performed with the TALYS 1.2 reaction code.JRC.DG.D.5-Nuclear physic

Gamma-ray Production Cross Sections for Evaluated Nuclear Data

Cross sections for gamma-rays produced in inelastic scattering, (n,2n) and (n,3n) cross sections are measured at the Geel Electron LINear Accelerator (Gelina) from threshold to 20 MeV. Total inelastic nd level inelastic cross sections are deduced and the measured primary data can be used to improve nuclear modelling of the inelastic and (n,xn) process. Here we show examples of 52Cr and 209 Bi compared with the recent JEFF-3.1 evaluation and TALYS model code calculations to illustrate the potential of this approach.JRC.D.5-Neutron physic