Determination of the ratios of the average plutonium-239 and neptunium-237 fission cross-sections to the average uranium-235 fission cross-section in quinta neutron field

Measurements of neutron-induced cross sections to generate nuclear data are a core activity of the JRC-Directorate G Standards for Nuclear Safety, Security and Safeguards unit in Geel. Thin 10B layers are of great importance in this activity as they are used to measure the absolute neutron flux in the beam using the standard 10B(n,α)7Li reaction cross-section as a reference. After a period of reduced activity and in line with a renewed interest for nuclear data, the demand for high quality 10B targets increased. In this paper we describe the design and features of a new e-beam evaporator specifically customized for the preparation of boron targets as replacement of the old dysfunctional equipment. Several 10B targets of varying thicknesses were prepared and characterized as part of the factory acceptance tests and implementation in the JRC-Geel target preparation laboratory. Differential substitution weighing was applied for mass determination and in order to calibrate the thickness monitor. Comparative time-of-flight measurements relative to 10B and 235U standard targets were conducted at the GELINA neutron time-of-flight facility at the JRC-Geel site as second methodology for the determination of 10B areal density. The morphology of the layers was assessed by means of Scanning Electron Microscopy (SEM). The determination of impurities was realized by means of Energy Dispersive X-ray (EDX). Finally, two boron targets were prepared in the frame of the measurement of the neutron induced fission cross-section of 230Th at the n_TOF neutron time-of-flight facility at CERN.

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Covariance generation for the prompt neutron multiplicity of 239Pu including the (n,γf) process

EPJ Web of Conferences ◽

10.1051/epjconf/202023912002 ◽

2020 ◽

Vol 239 ◽

pp. 12002

Author(s):

Esther Leal-Cidoncha ◽

Gilles Noguere ◽

Olivier Bouland ◽

Olivier Serot

Keyword(s):

Covariance Matrix ◽

Cross Section ◽

Cross Sections ◽

Matrix Theory ◽

Fission Cross Section ◽

Reaction Cross ◽

Partial Width ◽

R Matrix ◽

Reaction Cross Sections

Fission cross section of 239Pu can be seen as a sum of the “immediate" fission and “two-step" (n,γf) reactions. In the Resolved Resonance Range of the reaction cross sections, the contribution of the (n,γf) process has an impact on the determination of the partial widths magnitude involved in the Reich-Moore approximation of the R-matrix theory. The present work aims to investigate this impact by using the CONRAD code and the partial width Γγf for the (n,γf) reaction calculated by Lynn et al. [1]. A special attention will be paid to the covariance matrix obtained on νp.

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Determination of absolute fission cross section ratios using the method of threshold cross sections

10.2172/4385976 ◽

1973 ◽

Cited By ~ 2

Author(s):

J.W. Behrens

Keyword(s):

Cross Section ◽

Cross Sections ◽

Fission Cross Section

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A quantitative approach to inner shell losses

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010010977x ◽

1978 ◽

Vol 36 (1) ◽

pp. 526-527 ◽

Cited By ~ 2

Author(s):

R.D. Leapman ◽

P. Rez ◽

D.F. Mayers

Keyword(s):

Energy Transfer ◽

Cross Section ◽

Cross Sections ◽

Accurate Determination ◽

Background Intensity ◽

Core Excitation ◽

Quantitative Basis ◽

Cross Section Differential ◽

Bound Electrons

Microanalysis by EELS has been developing rapidly and though the general form of the spectrum is now understood there is a need to put the technique on a more quantitative basis (1,2). Certain aspects important for microanalysis include: (i) accurate determination of the partial cross sections, σx(α,ΔE) for core excitation when scattering lies inside collection angle a and energy range ΔE above the edge, (ii) behavior of the background intensity due to excitation of less strongly bound electrons, necessary for extrapolation beneath the signal of interest, (iii) departures from the simple hydrogenic K-edge seen in L and M losses, effecting σx and complicating microanalysis. Such problems might be approached empirically but here we describe how computation can elucidate the spectrum shape.The inelastic cross section differential with respect to energy transfer E and momentum transfer q for electrons of energy E0 and velocity v can be written as

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Study of the 232Th(n,f) Cross section at NCSR ‘Demokritos’ using Micromegas Detectors

HNPS Proceedings ◽

10.12681/hnps.2994 ◽

2020 ◽

Vol 27 ◽

pp. 106

Author(s):

Sotirios Chasapoglou ◽

A. Tsantiri ◽

A. Kalamara ◽

M. Kokkoris ◽

V. Michalopoulou ◽

...

Keyword(s):

Cross Section ◽

Cross Sections ◽

Nuclear Reactions ◽

Detection Efficiency ◽

High Energy ◽

Tandem Accelerator ◽

Line Detector ◽

Accelerator Driven Systems ◽

The Masses

The accurate knowledge of neutron-induced fission cross sections in actinides, is of great importance when it comes to the design of fast nuclear reactors, as well as accelerator driven systems. Specifically for the 232Th(n,f) case, the existing experimental datasets are quite discrepant in both the low and high energy MeV regions, thus leading to poor evaluations, a fact that in turn implies the need for more accurate measurements.In the present work, the total cross section of the 232Th(n,f) reaction has been measured relative to the 235U(n,f) and 238U(n,f) ones, at incident energies of 7.2, 8.4, 9.9 MeV and 14.8, 16.5, 17.8 MeV utilizing the 2H(d,n) and 3H(d,n) reactions respectively, which generally yield quasi-monoenergetic neutron beams. The experiments were performed at the 5.5 MV Tandem accelerator laboratory of N.C.S.R. “Demokritos”, using a Micromegas detector assembly and an ultra thin ThO2 target, especially prepared for fission measurements at n_ToF, CERN during its first phase of operations, using the painting technique. The masses of all actinide samples were determined via α-spectroscopy. The produced fission yields along with the results obtained from activation foils were studied in parallel, using both the NeusDesc [1] and MCNP5 [2] codes, taking into consideration competing nuclear reactions (e.g. deuteron break up), along with neutron elastic and inelastic scattering with the beam line, detector housing and experimental hall materials. Since the 232Th(n,f) reaction has a relatively low energy threshold and can thus be affected by parasitic neutrons originating from a variety of sources, the thorough characterization of the neutron flux impinging on the targets is a prerequisite for accurate cross-section measurements, especially in the absence of time-of-flight capabilities. Additional Monte-Carlo simulations were also performed coupling both GEF [3] and FLUKA [4] codes for the determination of the detection efficiency.

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Activation cross section of the (n,2n) reaction on Hf isotopes

HNPS Proceedings ◽

10.12681/hnps.1906 ◽

2019 ◽

Vol 23 ◽

pp. 47

Author(s):

A. Kalamara ◽

M. Serris ◽

A. Spiliotis ◽

D. Sigalos ◽

N. Patronis ◽

...

Keyword(s):

Cross Section ◽

Cross Sections ◽

Reaction Cross Section ◽

Beam Energy ◽

Reaction Cross ◽

Activation Technique ◽

Incident Neutron ◽

Activation Cross Section ◽

Reference Reaction

Cross sections of the 174Hf(n,2n)173Hf and 176Hf(n,2n)175Hf reactions have been experimentally determined relative to the 27Al(n,α)24Na reference reaction at incident neutron energies of 15.3 and 17.1 MeV by means of the activation technique. The irradiations were carried out at the 5 MV tandem T11/25 Accelerator Laboratory of NCSR "Demokritos" with monoenergetic neutron beams provided via the 3H(d,n)4He reaction, using a new Ti-tritiated target of 373 GBq activity. In the determination of the 176Hf(n,2n)175Hf reaction cross section the contamination of the 174Hf(n,γ)175Hf and 177Hf(n,3n)175Hf reactions has been taken into account. Moreover, the neutron beam energy has been studied by means of Monte Carlo simulation codes and the neutron flux has been determined via the 27Al(n,α)24Na reference reaction.

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Determination of the absorption cross-sections of higher order iodine oxides at 355 nm and 532 nm

10.5194/acp-2020-456 ◽

2020 ◽

Cited By ~ 1

Author(s):

Thomas R. Lewis ◽

Juan Carlos Gómez Martin ◽

Mark A. Blitz ◽

Carlos A. Cuevas ◽

John M. C. Plane ◽

...

Keyword(s):

Cross Section ◽

Cross Sections ◽

Atmospheric Chemistry ◽

Absorption Cross Section ◽

Absorption Cross ◽

Time Resolved ◽

Flight Mass Spectrometry ◽

Iodine Oxides ◽

Photo Ionization

Abstract. Iodine oxides (IxOy) play an important role in the atmospheric chemistry of iodine. They are initiators of new particle formation events in the coastal and polar boundary layer and act as iodine reservoirs in tropospheric ozone-depleting chemical cycles. Despite the importance of the aforementioned processes, the photochemistry of these molecules has not been studied in detail previously. Here, we report the first determination of the absorption cross sections of IxOy, x = 2, 3, 5, y = 1–12 at λ = 355 nm by combining pulsed laser photolysis of I2/O3 gas mixtures in air with time-resolved photo-ionization time-of-flight mass spectrometry, using NO2 actinometry for signal calibration. The oxides selected for absorption cross section determinations are those presenting the strongest signals in the mass spectra, where signals containing 4 iodine atoms are absent. The method is validated by measuring the absorption cross section of IO at 355 nm, σ355 nm, IO = (1.2 ± 0.1) × 10–18 cm2, which is found to be in good agreement with the most recent literature. The results obtained are: σ355 nm, I2O3

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Quantitative Ausmessung des Brom-Affinitätskontinuums und Bestimmung der Detachment-und Attachment-Querschnitte

Zeitschrift für Naturforschung A ◽

10.1515/zna-1970-1111 ◽

1970 ◽

Vol 25 (11) ◽

pp. 1617-1626 ◽

Cited By ~ 19

Author(s):

H. Frank ◽

M. Neiger ◽

H.-P. Popp

Keyword(s):

Cross Section ◽

Cross Sections ◽

Electron Affinity ◽

Elastic Cross Section ◽

Electron Atom ◽

Intensity Measurements ◽

Long Wave ◽

The Mean ◽

Intense Electron

Abstract A wall stabilized low-current cylindric arc was used to produce the radiation of the negative Bromine-ions. The radiation consists of an affinity-continuum with a long-wave threshold of 3682 Å, yielding an electron affinity for Bromine of 3.366 eV, and of an intense electron-atom Bremsstrahlung in the visible. Intensity measurements of the continua allow the determination of the photo-detachment-and attachment-cross-sections of Bromine and also the determination of the mean elastic cross-section of electrons against Bromine atoms.

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The determination of the cross sections for the reactions 27 Al( n , α ) and 56 Fe( n , p ) for 14 MeV neutrons by an absolute method

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1966.0127 ◽

1966 ◽

Vol 292 (1429) ◽

pp. 180-192 ◽

Cited By ~ 5

Keyword(s):

Cross Section ◽

Cross Sections ◽

Standard Error ◽

Particle Method ◽

Systematic Errors ◽

Aluminium Foil ◽

The Mean ◽

The Cross ◽

Experimental Values

Measurements of the cross sections for the reactions 27 Al( n , α ) 24 Na and 56 Fe( n, p ) 56 Mn for neutrons of energy 13.5 ± 0.1 MeV have been made by a radioactivation method. The neutron flux was determined by a variant of the 'associated particle’ method, in which the α -particles produced concurrently with the neutrons from the D + T reaction were estimated in terms of the volume of helium which accumulated when they were brought to rest in an aluminium foil. Cross section values obtained at 13.5 MeV were: for 27 Al( n , α ): 118.1 ± 6.0 mb : for 56 Fe( n, p ): 106.7 ± 4.7 mb. The errors quoted include both the standard error on the mean of the experimental values and an estimate of possible residual systematic errors. The excitation functions for both reactions in the energy region 13.5 to 14.8 MeV have also been investigated, in order to provide secondary cross section values over this range of energies. At 14.8 MeV the values found were: 27 Al( n , α )103.6 ± 5.5 mb; 56 Fe( n, p )96.7 ± 4.5 mb.

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