Papers by P. Schillebeeckx
Journal of Instrumentation, 2012
The resonance structure in neutron induced reaction cross sections can be used to determine the e... more The resonance structure in neutron induced reaction cross sections can be used to determine the elemental compositions of materials or objects. The occurrence of resonances is the basis of neutron resonance capture analysis (NRCA) and neutron resonance transmission analysis (NRTA). NRCA and NRTA are fully non-destructive methods to determine the bulk elemental composition without the need of any sample preparation
Measurement of the Subthermal Neutron Induced Fission Cross Section of 241Pu
Research Reports in Physics, 1992
by V. Vlachoudis, Christina Weiss, Alberto Ventura, C. Guerrero, P. Schillebeeckx, H. Leeb, Isabel Gonçalves, E. Chiaveri, José Manuel Quesada Molina, Alberto Mengoni, Carlos Paradela, M. Barbagallo, Andrea Tsinganis, N. Colonna, and J. Alcantara-nunez Physical Review C, 2014
The integral cross section of the 12 C(n, p) 12 B reaction has been determined for the first time... more The integral cross section of the 12 C(n, p) 12 B reaction has been determined for the first time in the neutron energy range from threshold to several GeV at the n TOF facility at CERN. The
Data reduction and uncertainty propagation of time-of-flight spectra with AGS
Journal of Instrumentation, 2012
ABSTRACT Results of neutron time-of-flight measurements are commonly used to parameterize neutron... more ABSTRACT Results of neutron time-of-flight measurements are commonly used to parameterize neutron induced reaction cross sections in the resonance region based on the R-matrix reaction theory. Reaction yields or transmission as well as their covariance information are derived starting from measured counting spectra. They are then used in a least squares adjustment for obtaining model parameters. In this paper, a compact formalism is presented to propagate both the correlated and uncorrelated uncertainty components. Full information on the origin of each correlated component of the covariance matrix is maintained. This is particularly important in order to avoid a bias on the model parameters through a phenomenon known as Peelle's Pertinent Puzzle (PPP). This compact formalism was implemented into the data reduction code AGS (Analysis of Geel Spectra).
Absolute determination of small samples of Pu and Am by calorimetry
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2012
ABSTRACT An extensive measurement campaign has been carried in order to recalibrate and assess th... more ABSTRACT An extensive measurement campaign has been carried in order to recalibrate and assess the performance of the small sample calorimeter (SSCAL) that was recently upgraded. The measurements have been performed in the Performance Laboratory of the Joint Research Centre's (JRC) Nuclear Security Unit in Ispra (Italy) using calibrated electric heat sources and standard reference nuclear materials. The SSCAL is a heat flow calorimeter which works by measuring the voltage generated by a heat-emitting sample across a thermal gap based on a thermopile cup technology. Results of calorimetry measurements carried out, both inside and outside a well-controlled environment of a climatic chamber, on reference Pu–Ga samples and well-characterised 241Am samples are presented and discussed. The latter samples were produced at the JRC-ITU to be used by the JRC-IRMM for various cross-section measurements (total, neutron capture and 241Am(n,2n) 240Am).
Investigations for the use of the fast digitizers with detectors for radiative capture measurements at GELINA
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2009
ABSTRACT The relatively long dead time in conventional data acquisition systems that provide simu... more ABSTRACT The relatively long dead time in conventional data acquisition systems that provide simultaneously the pulse height and the time information for the detected events hinders cross-section measurements with high count rates. This is the case for capture cross-section measurements at the time-of-flight facility GELINA using high radioactive samples or thick samples of materials having strong resonances. Either the high average count rate (e.g. due to the radioactivity of the sample) or the high instantaneous count rate for strong resonances results in a large dead time correction. One solution to reduce the impact of the dead time is the use of a data acquisition system based on fast digitizers. The performances of two commercial digitizers (CAEN N172B and Acqiris DC282), coupled to a C6D6 scintillator, have been tested in terms of pulse height linearity and resolution, dead time and time resolution. The signal processing was done on-line obtaining simultaneously the pulse height and time information for each detected event. With both digitizers a comparable pulse height linearity and resolution has been obtained as with a conventional system. The total dead time of both digital systems is at least a factor 5 shorter than the one for the conventional system. The main difference in performance between the two digitizers is the time resolution. For a relatively large scintillator, a time resolution of about 2 ns has been achieved with the DC282 module and the conventional system while the time resolution was limited to 15 ns with the CAEN N1728B module. For most nuclei a 15 ns time resolution is sufficient to perform resonance shape analysis. Therefore, the CAEN N1728B module can be used for the majority of capture cross-section measurements at GELINA. However, for nuclei with low level density, for which the resolved resonance region extends to the keV-region, a better time resolution is required and the Acqiris DC282 module has to be used.
Neutron Capture on ^209Bi: Determination of the Production Ratio of ^210mBi/^210gBi
Journal of the Korean Physical Society, 2011
ABSTRACT Neutron capture on Bi-209 produces either an isomeric state Bi-210m with a half life of ... more ABSTRACT Neutron capture on Bi-209 produces either an isomeric state Bi-210m with a half life of 3 x 106 years, or the ground state Bi-210g which decays with a half life of 5 days to the alpha emitter Po-210. Therefore the neutron capture cross section ratio Bi-209(n,gamma)Bi-210m/Bi-210g plays an important role in predicting the short- and long-term radio-toxicity produced by Bi-209 under neutron irradiation. This ratio is dependent on the neutron energy. We have measured this ratio for cold neutrons at the cold neutron beam facility of the Budapest Neutron Centre by observing the population of the ground-and the metastable state using high resolution gamma-ray spectroscopy. The same technique has been used at the pulsed white neutron source GELINA of the IRMM, Geel in combination with the neutron time-of-flight technique. Results for the neutron-energy dependent branching ratio will be presented. In addition we performed simulations using a statistical decay code.
Investigation of mass, charge and energy of 241Pu (nth, f) fragments with the Cosi-Fan-Tutte spectrometer
Nuclear Physics A, 1994
The mass, charge and energy distributions and their correlations have been studied for the fragme... more The mass, charge and energy distributions and their correlations have been studied for the fragments from thermal neutron-induced fission of 241 Pu, using the fission-fragment spectrometer Cosi-Fan-Tutte. The mass and charge distributions obtained agree with the ...
Comparative study of the fragments' mass and energy characteristics in the spontaneous fussion of 238Pu, 240Pu and 242Pu and in the thermal-neutron-induced …
Nuclear Physics A, 1992
... Phys. A491 (1989) 56 26) A. Ruben and H. Marten, Proc. Seminar of Fission Pont d'Oye II,... more ... Phys. A491 (1989) 56 26) A. Ruben and H. Marten, Proc. Seminar of Fission Pont d'Oye II, ed. C. Wagemans, HabaylaNeuve, Belgium (1991) p. 24 27) B. Wilkins, E. Steinberg and R. Chasman, Phys. Rev. r.14 (!976) 1832 281' U. Mosel and H. Schmitt, Phys. Rev. ...
by V. Vlachoudis, Christina Weiss, Alberto Ventura, C. Guerrero, P. Schillebeeckx, H. Leeb, Isabel Gonçalves, E. Chiaveri, José Manuel Quesada Molina, C. Lampoudis, Carlos Paradela, Daniel Cano Ott, M. Barbagallo, and Andrea Tsinganis The neutron time-of-flight facility n TOF features a white neutron source produced by spallation ... more The neutron time-of-flight facility n TOF features a white neutron source produced by spallation through 20 GeV/c protons impinging on a lead target. The facility, aiming primarily at the measurement of neutron-induced reaction cross sections, was operating at CERN between 2001 and 2004, and then underwent a major upgrade in 2008. This paper presents in detail all the characteristics of the new neutron beam in the currently available configurations, which correspond to two different collimation systems and two choices of neutron moderator. The characteristics discussed include the intensity and energy dependence of the neutron flux, the spatial profile of the beam, the in-beam background components and the energy resolution/broadening. The discussion of these features is based on dedicated measurements and Monte Carlo simulations, and includes estimations of the systematic uncertainties of the mentioned quantities.
Neutron resonances are the signature signals of a non-destructive elemental and isotopic analysis... more Neutron resonances are the signature signals of a non-destructive elemental and isotopic analysis technique in archaeological sciences. We report on Neutron Resonance Transmission Analysis and its capabilities as a bulk elemental imaging technique to test the homogeneity of samples and to localize elements of interest in archaeological samples and museum objects. A high neutron flux is required for imaging in order to achieve reasonable spatial resolution and to keep measurement times within realistic limits. A modular system for neutron resonance transmission analysis has been designed and installed at the INES beamline of the ISIS spallation neutron source as a part of the ANCIENT CHARM project. The main component is a neutron position sensitive transmission detector which is based on a 10 Â 10 array of 6 Li-glass crystals mounted on a pitch of 2.5 mm, resulting in a 25 Â 25 mm 2 active area. Transmission spectra are obtained by a measurement of the flight time of epithermal neutrons passing through an object. The transmission dips observed in a time-of-flight spectrum can be used to identify and quantify specific nuclides. In this paper the technique is described together with the data reduction and analysis procedures. In addition, preliminary results obtained from measurements on cultural heritage samples are discussed.
Annals of Nuclear Energy, 2013
A review of the experimental data for nat C(n, c) and 12 C(n, c) was made to identify the origin ... more A review of the experimental data for nat C(n, c) and 12 C(n, c) was made to identify the origin of the nat C capture cross sections included in evaluated data libraries and to clarify differences observed in neutronic calculations for graphite moderated reactors using different libraries. The performance of the JEFF-3.1.2 and ENDF/B-VII.1 libraries was verified by comparing results of criticality calculations with experimental results obtained for the BR1 reactor. This reactor is an air-cooled reactor with graphite as moderator and is located at the Belgian Nuclear Research Centre SCKCEN in Mol (Belgium). The results of this study confirm conclusions drawn from neutronic calculations of the High Temperature Engineering Test Reactor (HTTR) in Japan. Furthermore, both BR1 and HTTR calculations support the capture cross section of 12 C at thermal energy which is recommended by Firestone and Révay. Additional criticality calculations were carried out in order to illustrate that the nat C thermal capture cross section is important for systems with a large amount of graphite. The present study shows that only the evaluation carried out for JENDL-4.0 reflects the current status of the experimental data.
Neutron activation analysis k 0 standardisation method Thermal and epithermal self-shielding fact... more Neutron activation analysis k 0 standardisation method Thermal and epithermal self-shielding factors Rh foils a b s t r a c t Rhodium foils of about 5 mm diameter were obtained from IRMM. One foil had thickness of 0.006 mm and three were 0.112 mm thick. They were irradiated in the pneumatic transfer system and in the carousel facility of the TRIGA reactor at the Jožef Stefan Institute. The foils were irradiated bare and enclosed in small cadmium boxes (about 2 g weight) of 1 mm thickness to minimise the perturbation of the local neutron flux. They were co-irradiated with 5 mm diameter and 0.2 mm thick Al-Au (0.1%) alloy monitor foils. The resonance self-shielding corrections for the 0.006 and 0.112 mm thick samples were calculated by the Monte Carlo simulation and amount to about 10% and 60%, respectively. The consistency of measurements confirmed the validity of self-shielding factors. Trial estimates of Q 0 and k 0 factors for the 555.8 keV gamma line of 104 Rh were made and amount to 6.65 7 0.18 and (6.61 7 0.12) Â 10 -2 , respectively.
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Papers by P. Schillebeeckx