The thermal neutron absorption cross-sections, resonance integrals and resonance parameters of silicon and its stable isotopes

International Nuclear Information System (INIS)

Story, J.S.

1969-09-01

The data available up to the end of November 1968 on the thermal neutron absorption cross-sections, resonance absorption integrals, and resonance parameters of silicon and its stable isotopes are collected and discussed. Estimates are given of the mean spacing of the energy levels of the compound nuclei near the neutron binding energy. It is concluded that the thermal neutron absorption cross-section and resonance absorption integral of natural silicon are not well established. The data on these two parameters are somewhat correlated, and three different assessments of the resonance integral are presented which differ over-all by a factor of 230. Many resonances have been detected by charged particle reactions which have not yet been observed in neutron cross-section measurements. One of these resonances of Si 2 8, at E n = 4 ± 5 keV might account for the large resonance integral which is derived, very uncertainly, from integral data. The principal source of the measured resonance integral of Si 3 0 has not yet been located. The thermal neutron absorption cross-section of Si 2 8 appears to result mainly from a negative energy resonance, possibly the resonance at E n = - 59 ± 5 keV detected by the Si 2 8 (d,p) reaction. (author)

γ-transitions from neutron resonances and many-quasiparticle configurations

International Nuclear Information System (INIS)

Soloviev, V.G.

1991-01-01

One should answer the question posed in 1972: Are there large many-quasiparticle components in the wave functions of highly excited low-spin states and, in particular, of neutron resonances? With increasing excitation energy the structure of states becomes more complex; the contribution of few-quasiparticle components to wave function normalization decreases exponentially and for the neutron resonances of heavy nuclei it equals 10 -6 . It is obvious that the wave function of neutron resonances contain many thousands of various quasiparticle components. Two extreme cases are possible. In the first case all the components are small and distributed according to statistical laws. In the second case among many components there is one or a few large many-quasiparticle components. There are many-quasiparticle isomers with high spins whose large life-time is due to the absence of few-quasiparticle components. This indicates a small fragmentation of these states. Low-spin states are fragmented more strongly than high-spin ones. What experiments are to be performed to answer the question about the existence are to be performed to answer the question about the existence of many-quasiparticle components of the wave functions of neutron resonances? It seems that the most straight way for observing large many-quasiparticle components is many-nucleon transfer reactions. However, in this way one faces great difficulties. The author thinks it to be more convenient to study γ transitions from neutron resonances to the states with energies by 1-2 MeV less than the energies of neutron resonances

Non-destructive studies of fuel pellets by neutron resonance absorption radiography and thermal neutron radiography

Energy Technology Data Exchange (ETDEWEB)

Tremsin, A.S., E-mail: ast@ssl.berkeley.edu [University of California, Berkeley, CA 94720 (United States); Vogel, S.C.; Mocko, M.; Bourke, M.A.M.; Yuan, V.; Nelson, R.O.; Brown, D.W. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Feller, W.B. [NOVA Scientific, Inc., 10 Picker Rd., Sturbridge, MA 01566 (United States)

2013-09-15

Many isotopes in nuclear materials exhibit strong peaks in neutron absorption cross sections in the epithermal energy range (1–1000 eV). These peaks (often referred to as resonances) occur at energies specific to particular isotopes, providing a means of isotope identification and concentration measurements. The high penetration of epithermal neutrons through most materials is very useful for studies where samples consist of heavy-Z elements opaque to X-rays and sometimes to thermal neutrons as well. The characterization of nuclear fuel elements in their cladding can benefit from the development of high resolution neutron resonance absorption imaging (NRAI), enabled by recently developed spatially-resolved neutron time-of-flight detectors. In this technique the neutron transmission of the sample is measured as a function of spatial location and of neutron energy. In the region of the spectra that borders the resonance energy for a particular isotope, the reduction in transmission can be used to acquire an image revealing the 2-dimensional distribution of that isotope within the sample. Provided that the energy of each transmitted neutron is measured by the neutron detector used and the irradiated sample possesses neutron absorption resonances, then isotope-specific location maps can be acquired simultaneously for several isotopes. This can be done even in the case where samples are opaque or have very similar transmission for thermal neutrons and X-rays or where only low concentrations of particular isotopes are present (<0.1 atom% in some cases). Ultimately, such radiographs of isotope location can be utilized to measure isotope concentration, and can even be combined to produce three-dimensional distributions using tomographic methods. In this paper we present the proof-of-principle of NRAI and transmission Bragg edge imaging performed at Flight Path 5 (FP5) at the LANSCE pulsed, moderated neutron source of Los Alamos National Laboratory. A set of urania mockup

Experiments at the GELINA facility for the validation of the self-indication neutron resonance densitometry technique

Directory of Open Access Journals (Sweden)

Rossa Riccardo

2017-01-01

Full Text Available Self-Indication Neutron Resonance Densitometry (SINRD is a passive non-destructive method that is being investigated to quantify the 239Pu content in a spent fuel assembly. The technique relies on the energy dependence of total cross sections for neutron induced reaction. The cross sections show resonance structures that can be used to quantify the presence of materials in objects, e.g. the total cross-section of 239Pu shows a strong resonance close to 0.3 eV. This resonance will cause a reduction of the number of neutrons emitted from spent fuel when 239Pu is present. Hence such a reduction can be used to quantify the amount of 239Pu present in the fuel. A neutron detector with a high sensitivity to neutrons in this energy region is used to enhance the sensitivity to 239Pu. This principle is similar to self-indication cross section measurements. An appropriate detector can be realized by surrounding a 239Pu-loaded fission chamber with appropriate neutron absorbing material. In this contribution experiments performed at the GELINA time-of-flight facility of the JRC at Geel (Belgium to validate the simulations are discussed. The results confirm that the strongest sensitivity to the target material was achieved with the self-indication technique, highlighting the importance of using a 239Pu fission chamber for the SINRD measurements.

Neutron detection in the frame of spatial magnetic spin resonance

Energy Technology Data Exchange (ETDEWEB)

Jericha, Erwin, E-mail: jericha@ati.ac.at [TU Wien, Atominstitut, Stadionallee 2, 1020 Wien (Austria); Bosina, Joachim [TU Wien, Atominstitut, Stadionallee 2, 1020 Wien (Austria); Austrian Academy of Sciences, Stefan Meyer Institute, Boltzmanngasse 3, 1090 Wien (Austria); Institut Laue–Langevin, 71 Avenue des Martyrs, 38042 Grenoble (France); Geltenbort, Peter [Institut Laue–Langevin, 71 Avenue des Martyrs, 38042 Grenoble (France); Hino, Masahiro [Kyoto University, Research Reactor Institute, Kumatori, Osaka 590-0494 (Japan); Mach, Wilfried [TU Wien, Atominstitut, Stadionallee 2, 1020 Wien (Austria); Oda, Tatsuro [Kyoto University, Department of Nuclear Engineering, Kyoto 615-8540 (Japan); Badurek, Gerald [TU Wien, Atominstitut, Stadionallee 2, 1020 Wien (Austria)

2017-02-11

This work is related to neutron detection in the context of the polarised neutron optics technique of spatial magnetic spin resonance. By this technique neutron beams may be tailored in their spectral distribution and temporal structure. We have performed experiments with very cold neutrons (VCN) at the high-flux research reactor of the Institut Laue Langevin (ILL) in Grenoble to demonstrate the potential of this method. A combination of spatially and temporally resolving neutron detection allowed us to characterize a prototype neutron resonator. With this detector we were able to record neutron time-of-flight spectra, assess and minimise neutron background and provide for normalisation of the spectra owing to variations in reactor power and ambient conditions at the same time.

Radiative neutron capture: Hauser Feshbach vs. statistical resonances

Energy Technology Data Exchange (ETDEWEB)

Rochman, D., E-mail: dimitri-alexandre.rochman@psi.ch [Reactor Physics and Systems Behavior Laboratory, Paul Scherrer Institute, Villigen (Switzerland); Goriely, S. [Institut d' Astronomie et d' Astrophysique, CP-226, Université Libre de Bruxelles, 1050 Brussels (Belgium); Koning, A.J. [Nuclear Data Section, IAEA, Vienna (Austria); Uppsala University, Uppsala (Sweden); Ferroukhi, H. [Reactor Physics and Systems Behavior Laboratory, Paul Scherrer Institute, Villigen (Switzerland)

2017-01-10

The radiative neutron capture rates for isotopes of astrophysical interest are commonly calculated on the basis of the statistical Hauser Feshbach (HF) reaction model, leading to smooth and monotonically varying temperature-dependent Maxwellian-averaged cross sections (MACS). The HF approximation is known to be valid if the number of resonances in the compound system is relatively high. However, such a condition is hardly fulfilled for keV neutrons captured on light or exotic neutron-rich nuclei. For this reason, a different procedure is proposed here, based on the generation of statistical resonances. This novel technique, called the “High Fidelity Resonance” (HFR) method is shown to provide similar results as the HF approach for nuclei with a high level density but to deviate and be more realistic than HF predictions for light and neutron-rich nuclei or at relatively low sub-keV energies. The MACS derived with the HFR method are systematically compared with the traditional HF calculations for some 3300 neutron-rich nuclei and shown to give rise to significantly larger predictions with respect to the HF approach at energies of astrophysical relevance. For this reason, the HF approach should not be applied to light or neutron-rich nuclei. The Doppler broadening of the generated resonances is also studied and found to have a negligible impact on the calculated MACS.

Partial radiative capture of resonance neutrons; Capture radiative partielle des neutrons de resonance

Energy Technology Data Exchange (ETDEWEB)

Samour, C [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1969-07-01

The radiative capture of resonance neutrons has been studied near the Saclay linac between 0.5 and 700 eV with time-of-flight method and a Ge(Li) detector. {sup 195}Pt + n and {sup 183}W + n allow the study of the distribution of partial radiative widths and their eventual correlation and also the variation of < {gamma}{sub {gamma}{sub i}} > with E{sub {gamma}}. The mean values of Ml and El transition intensities are compared in several tin isotopes. Interference effects, either between resonances or between direct capture and resonant capture are found in {sup 195}Pt + n, {sup 197}Au + n and {sup 59}Co + n. The excited level schemes of a great deal of nuclei are obtained and compared with theoretical predictions. This study has been completed by an analysis of thermal spectrum. (author) [French] La capture radiative des neutrons de resonance a ete etudiee pres de l'accelerateur lineaire de Saclay entre 0,5 et 700 eV a l'aide de la methode du temps-de-vol et d'un detecteur Ge(Li). Les noyaux {sup 195}Pt + n et {sup 183}W + n permettent l'analyse de la distribution de resonance en resonance des largeurs radiatives partielles {gamma}{sub {gamma}{sub i}} et de leur eventuelle correlation, ainsi que l'etude de la variation de < {gamma}{sub {gamma}{sub i}} > en fonction de E{sub {gamma}}. Les intensites moyennes des transitions Ml et El sont comparees pour quelques isotopes de l'etain. Des effets d'interference, soit entre resonances, soit entre capture directe et capture resonnante sont mis en evidence dans {sup 195}Pt + n, {sup 197}Au + n et {sup 59}Co + n. Enfin les schemas des etats excites d'un grand nombre de noyaux sont obtenus et compares avec les predictions theoriques. Cette etude a ete completee par une analyse des spectres thermiques. (auteur)

Partial radiative capture of resonance neutrons; Capture radiative partielle des neutrons de resonance

Energy Technology Data Exchange (ETDEWEB)

Samour, C. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1969-07-01

The radiative capture of resonance neutrons has been studied near the Saclay linac between 0.5 and 700 eV with time-of-flight method and a Ge(Li) detector. {sup 195}Pt + n and {sup 183}W + n allow the study of the distribution of partial radiative widths and their eventual correlation and also the variation of < {gamma}{sub {gamma}{sub i}} > with E{sub {gamma}}. The mean values of Ml and El transition intensities are compared in several tin isotopes. Interference effects, either between resonances or between direct capture and resonant capture are found in {sup 195}Pt + n, {sup 197}Au + n and {sup 59}Co + n. The excited level schemes of a great deal of nuclei are obtained and compared with theoretical predictions. This study has been completed by an analysis of thermal spectrum. (author) [French] La capture radiative des neutrons de resonance a ete etudiee pres de l'accelerateur lineaire de Saclay entre 0,5 et 700 eV a l'aide de la methode du temps-de-vol et d'un detecteur Ge(Li). Les noyaux {sup 195}Pt + n et {sup 183}W + n permettent l'analyse de la distribution de resonance en resonance des largeurs radiatives partielles {gamma}{sub {gamma}{sub i}} et de leur eventuelle correlation, ainsi que l'etude de la variation de < {gamma}{sub {gamma}{sub i}} > en fonction de E{sub {gamma}}. Les intensites moyennes des transitions Ml et El sont comparees pour quelques isotopes de l'etain. Des effets d'interference, soit entre resonances, soit entre capture directe et capture resonnante sont mis en evidence dans {sup 195}Pt + n, {sup 197}Au + n et {sup 59}Co + n. Enfin les schemas des etats excites d'un grand nombre de noyaux sont obtenus et compares avec les predictions theoriques. Cette etude a ete completee par une analyse des spectres thermiques. (auteur)

Neutron resonance absorption theory

International Nuclear Information System (INIS)

Reuss, P.

1991-11-01

After some recalls on the physics of neutron resonance absorption during their slowing down, this paper presents the main features of the theoretical developments performed by the french school of reactor physics: the effective reaction rate method so called Livolant-Jeanpierre theory, the generalizations carried out by the author, and the probability table method [fr

Neutron resonance analysis for nuclear safeguards and security applications

Science.gov (United States)

Paradela, Carlos; Heyse, Jan; Kopecky, Stefan; Schillebeeckx, Peter; Harada, Hideo; Kitatani, Fumito; Koizumi, Mitsuo; Tsuchiya, Harufumi

2017-09-01

Neutron-induced reactions can be used to study the properties of nuclear materials of interest in the fields of nuclear safeguards and security. The elemental and isotopic composition of these materials can be determined by using the presence of resonance structures. This idea is the basis of two non-destructive analysis techniques which have been developed at the GELINA neutron time-of-flight facility at JRC-Geel: Neutron Resonance Capture Analysis (NRCA) and Neutron Resonance Transmission Analysis (NRTA). A combination of NRTA and NRCA has been proposed for the characterisation of particle-like debris of melted fuel formed in severe nuclear accidents. In this work, we present a quantitative validation of the NRTA technique which was used to determine the areal densities of Pu enriched reference samples used for safeguards applications. Less than 2% bias has been obtained for the fissile isotopes, with well-known total cross sections.

Determination of contraband using fast neutron resonance technique

Energy Technology Data Exchange (ETDEWEB)

Bae, J.; Whang, J. [Kyunghee Univ., Dept. of Nuclear Engineering, Yongin-shi, Kyongki-do (Korea, Republic of)

2004-07-01

'Full-text:' Resonance technique with monoenergetic fast neutron beam is able to map features in bulk samples in a way that is sensitive to their elemental composition. It has a number of potential applications, for example, in mining and in the detection of contraband materials such as illicit drugs and explosives. By moving around the neutron detector experiences neutrons in the form of narrow line beam with different energies as the angle to the neutron source changes. Projection data was obtained using the Monte Carlo code MCNP4C. Therefore the fast neutrons scattered from an unknown object are used to determine the elemental content of the object and hence lead to its identification. Scattered features simulated for various test materials are analyzed using the HEPRO program system (PTB, Braunschweig) to determine the atom weight fractions for H. C. N, O and other elements in the materials. Atom weight fractions determined from scattering features are insensitive to neutron interactions in interfering materials surrounding the object. The simulations demonstrate that the fast neutron resonance technique (FNRT) provides reliable elemental characterization of bulk materials and has the necessary sensitivity to distinguish between drugs, explosives and other materials. (author)

Determination of contraband using fast neutron resonance technique

International Nuclear Information System (INIS)

Bae, J.; Whang, J.

2004-01-01

'Full-text:' Resonance technique with monoenergetic fast neutron beam is able to map features in bulk samples in a way that is sensitive to their elemental composition. It has a number of potential applications, for example, in mining and in the detection of contraband materials such as illicit drugs and explosives. By moving around the neutron detector experiences neutrons in the form of narrow line beam with different energies as the angle to the neutron source changes. Projection data was obtained using the Monte Carlo code MCNP4C. Therefore the fast neutrons scattered from an unknown object are used to determine the elemental content of the object and hence lead to its identification. Scattered features simulated for various test materials are analyzed using the HEPRO program system (PTB, Braunschweig) to determine the atom weight fractions for H. C. N, O and other elements in the materials. Atom weight fractions determined from scattering features are insensitive to neutron interactions in interfering materials surrounding the object. The simulations demonstrate that the fast neutron resonance technique (FNRT) provides reliable elemental characterization of bulk materials and has the necessary sensitivity to distinguish between drugs, explosives and other materials. (author)

Neutron resonance spectroscopy for the characterization of materials and objects

International Nuclear Information System (INIS)

Schillebeeckx, P; Borella, A; Emiliani, F; Kopecky, S; Lampoudis, C; Gorini, G; Cippo, E Perelli; Kockelmann, W; Rhodes, N J; Schooneveld, E M; Moxon, M; Postma, H; Van Beveren, C

2012-01-01

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 and resulting in a negligible residual activity. They have been applied to determine the elemental composition of archaeological objects and to characterize reference materials used for cross section measurements. For imaging applications a position sensitive neutron detector has been developed within the ANCIENT CHARM project. The detector is based on a 10 × 10 array of 6 Li-glass scintillators mounted on a pitch of 2.5 mm, resulting in a 25 × 25 mm 2 active area. The detector has been tested at the time-of-flight facility GELINA and used at the ISIS spallation source to study cultural heritage objects.

Neutron resonance spectroscopy for the characterization of materials and objects

Science.gov (United States)

Schillebeeckx, P.; Borella, A.; Emiliani, F.; Gorini, G.; Kockelmann, W.; Kopecky, S.; Lampoudis, C.; Moxon, M.; Perelli Cippo, E.; Postma, H.; Rhodes, N. J.; Schooneveld, E. M.; Van Beveren, C.

2012-03-01

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 and resulting in a negligible residual activity. They have been applied to determine the elemental composition of archaeological objects and to characterize reference materials used for cross section measurements. For imaging applications a position sensitive neutron detector has been developed within the ANCIENT CHARM project. The detector is based on a 10 × 10 array of 6Li-glass scintillators mounted on a pitch of 2.5 mm, resulting in a 25 × 25 mm2 active area. The detector has been tested at the time-of-flight facility GELINA and used at the ISIS spallation source to study cultural heritage objects.

Two-dimensional thermometry by using neutron resonance absorption spectrometer DOG

International Nuclear Information System (INIS)

Kamiyama, T.; Noda, H.; Kiyanagi, Y.; Ikeda, S.

2001-01-01

We applied the neutron resonance absorption spectroscopy to thermometry of a bulk object. The measurement was done by using the neutron resonance absorption spectrometer, DOG, installed at KENS, High Energy Accelerator Research Organization Neutron Source, which enables us to investigate effective temperature of a particular element by analyzing line width of resonance absorption spectrum. The effective temperature becomes consistence with the sample temperature above room temperature. For the analysis we applied the computed tomography method to reconstruct the temperature distribution on the object cross section. The results and the calculated distribution by the heat conducting equation are well agreed on the temperature difference inside the object. (author)

GEANT4 simulation study of a gamma-ray detector for neutron resonance densitometry

International Nuclear Information System (INIS)

Tsuchiya, Harufumi; Harada, Hideo; Koizumi, Mitsuo; Kitatani, Fumito; Takamine, Jun; Kureta, Masatoshi; Iimura, Hideki

2013-01-01

A design study of a gamma-ray detector for neutron resonance densitometry was made with GEANT4. The neutron resonance densitometry, combining neutron resonance transmission analysis and neutron resonance capture analysis, is a non-destructive technique to measure amounts of nuclear materials in melted fuels of the Fukushima Daiichi nuclear power plants. In order to effectively quantify impurities in the melted fuels via prompt gamma-ray measurements, a gamma-ray detector for the neutron resonance densitometry consists of cylindrical and well type LaBr 3 scintillators. The present simulation showed that the proposed gamma-ray detector suffices to clearly detect the gamma rays emitted by 10 B(n, αγ) reaction in a high environmental background due to 137 Cs radioactivity with its Compton edge suppressed at a considerably small level. (author)

The feasibility study of Dragon Ⅰ using for temperature measurement of resonance neutron

International Nuclear Information System (INIS)

Xiang Yanjun; Ma Jingfang; Ai Jie; Fan Ruifeng

2010-01-01

The temperature measurement using neutron resonance spectrum can be used for temperature measurement of shock wave, but the high intensity pulsed neutron source is needed. This paper calculates the neutron transmission spectrum through resonance sample (contained 182 W), which produced by the current electron beam of Dragon Ⅰ impacting uranium target. The 4.155 eV and 21.06 eV resonance drop of 182 W can be seen from the transmission spectrum. Then, according to the experiment condition of Los Alamos, the neutron resonance spectrum of Dragon Ⅰ have been computed. Dragon Ⅰ can be used for temperature measurement using neutron spectrum, comparing this simulated result and the experiment result of Los Alamos. (authors)

Neutron Resonance Theory for Nuclear Reactor Applications: Modern Theory and Practices.

Energy Technology Data Exchange (ETDEWEB)

Hwang, Richard N. [Argonne National Lab. (ANL), Argonne, IL (United States); Blomquist, Roger N. [Argonne National Lab. (ANL), Argonne, IL (United States); Leal, Luiz C. [Inst. de Radioprotection et de Sûrete Nucleaire (ISRN), Fontenay-aux-Roses (France); Yang, Won Sik [Purdue Univ., West Lafayette, IN (United States)

2016-09-24

The neutron resonance phenomena constitute one of the most fundamental subjects in nuclear physics as well as in reactor physics. It is the area where the concepts of nuclear interaction and the treatment of the neutronic balance in reactor fuel lattices become intertwined. The latter requires the detailed knowledge of resonance structures of many nuclides of practical interest to the development of nuclear energy. The most essential element in reactor physics is to provide an accurate account of the intricate balance between the neutrons produced by the fission process and neutrons lost due to the absorption process as well as those leaking out of the reactor system. The presence of resonance structures in many major nuclides obviously plays an important role in such processes. There has been a great deal of theoretical and practical interest in resonance reactions since Fermi’s discovery of resonance absorption of neutrons as they were slowed down in water. The resonance absorption became the center of attention when the question was raised as to the feasibility of the self-sustaining chain reaction in a natural uranium-fueled system. The threshold of the nuclear era was crossed almost eighty years ago when Fermi and Szilard observed that a substantial reduction in resonance absorption is possible if the uranium was made into the form of lumps instead of a homogeneous mixture with water. In the West, the first practical method for estimating the resonance escape probability in a reactor cell was pioneered by Wigner et al in early forties.

Four-wave neutron-resonance spin echo

International Nuclear Information System (INIS)

Grigoriev, S.V.; Kraan, W.H.; Rekveldt, M.Th.

2004-01-01

We develop a technique of scattering from many-body systems. It is based on the principle of the neutron spin echo (SE), where a neutron wave in the magnetic field splits into two waves, which are separated in space or in time after propagation in this field. The neutron thus prepared as a probe passes through the sample to test its properties on a space R or time t scale. This separation in space or in time can be measured using coherence of these two waves as a phase shift φ between them. These two waves are collected or focused and compensated by the SE technique in order to compare their phases after interaction with the sample. In this way one studies interference between these waves and thus can directly measure the pair-correlation function in space or in time. Instead of two-wave SE we propose to realize the four-wave neutron-resonance spin-echo (NRSE). In our experiments, spin precession produced by a couple of the neutron-resonance coils in one arm is compensated by an identical couple of other NR coils in a second arm of a spin-echo machine. The neutron spin-flip probability ρ in the resonance coils is a key parameter of the NRSE arm. The limiting cases, ρ=0 and ρ=1, provide, in quantum terms, a two-level-two-wave k splitting of the neutron and result in the separation of the split waves into two different lengths in space (R 1 ,R 2 ) or in time (t 1 ,t 2 ). These two cases correspond to Larmor precession with phase φ 1 in the static magnetic fields of the NR flippers or to NRSE precession with φ 2 , respectively. The intermediate case, 0 1 ,R 2 ,R 3 ) or in time (t 1 ,t 2 ,t 3 ). The interference of each pair of waves after compensation results in three different echos with phases φ 1 , φ 2 , and φ 3 =(φ 1 +φ 2 )/2. Focusing or compensating all four waves into a single point of the phase-of-waves diagram produces quantum interference of all newly created waves. This task of focusing is experimentally performed. Different options for the

Neutron resonance transmission spectroscopy with high spatial and energy resolution at the J-PARC pulsed neutron source

Energy Technology Data Exchange (ETDEWEB)

Tremsin, A.S., E-mail: ast@ssl.berkeley.edu [University of California at Berkeley, 7 Gauss Way, Berkeley, CA 94720 (United States); Shinohara, T.; Kai, T.; Ooi, M. [Japan Atomic Energy Agency, 2–4 Shirakata-shirane, Tokai-mura, Naka-gun, Ibaraki 319-1195 (Japan); Kamiyama, T.; Kiyanagi, Y.; Shiota, Y. [Hokkaido University, Kita 13 Nishi 8 Kita-ku, Sapporo-shi, Hokkaido 060-8628 (Japan); McPhate, J.B.; Vallerga, J.V.; Siegmund, O.H.W. [University of California at Berkeley, 7 Gauss Way, Berkeley, CA 94720 (United States); Feller, W.B. [NOVA Scientific, Inc., 10 Picker Rd., Sturbridge, MA 01566 (United States)

2014-05-11

The sharp variation of neutron attenuation at certain energies specific to particular nuclides (the lower range being from ∼1 eV up to ∼1 keV), can be exploited for the remote mapping of element and/or isotope distributions, as well as temperature probing, within relatively thick samples. Intense pulsed neutron beam-lines at spallation sources combined with a high spatial, high-timing resolution neutron counting detector, provide a unique opportunity to measure neutron transmission spectra through the time-of-flight technique. We present the results of experiments where spatially resolved neutron resonances were measured, at energies up to 50 keV. These experiments were performed with the intense flux low background NOBORU neutron beamline at the J-PARC neutron source and the high timing resolution (∼20 ns at epithermal neutron energies) and spatial resolution (∼55 µm) neutron counting detector using microchannel plates coupled to a Timepix electronic readout. Simultaneous element-specific imaging was carried out for several materials, at a spatial resolution of ∼150 µm. The high timing resolution of our detector combined with the low background beamline, also enabled characterization of the neutron pulse itself – specifically its pulse width, which varies with neutron energy. The results of our measurements are in good agreement with the predicted results for the double pulse structure of the J-PARC facility, which provides two 100 ns-wide proton pulses separated by 600 ns, broadened by the neutron energy moderation process. Thermal neutron radiography can be conducted simultaneously with resonance transmission spectroscopy, and can reveal the internal structure of the samples. The transmission spectra measured in our experiments demonstrate the feasibility of mapping elemental distributions using this non-destructive technique, for those elements (and in certain cases, specific isotopes), which have resonance energies below a few keV, and with lower

The problem of resonance self-shielding effect in neutron multigroup calculations

International Nuclear Information System (INIS)

Wang Qingming; Huang Jinghua

1991-01-01

It is not allowed to neglect the resonance self-shielding effect in hybrid blanket and fast reactor neutron designs. The authors discussed the importance as well as the method of considering the resonance self-shielding effect in hybrid blanket and fast reactor neutron multigroup calculations

Resonance analysis and evaluation of the 235U neutron induced cross sections

International Nuclear Information System (INIS)

Leal, L.C.

1990-06-01

Neutron cross sections of fissile nuclei are of considerable interest for the understanding of parameters such as resonance absorption, resonance escape probability, resonance self-shielding,and the dependence of the reactivity on temperature. In the present study, new techniques for the evaluation of the 235 U neutron cross sections are described. The Reich-Moore formalism of the Bayesian computer code SAMMY was used to perform consistent R-matrix multilevel analyses of the selected neutron cross-section data. The Δ 3 -statistics of Dyson and Mehta, along with high-resolution data and the spin-separated fission cross-section data, have provided the possibility of developing a new methodology for the analysis and evaluation of neutron-nucleus cross sections. The results of the analysis consists of a set of resonance parameters which describe the 235 U neutron cross sections up to 500 eV. The set of resonance parameters obtained through a R-matrix analysis are expected to satisfy statistical properties which lead to information on the nuclear structure. The resonance parameters were tested and showed good agreement with the theory. It is expected that the parametrization of the 235 U neutron cross sections obtained in this dissertation represents the current state of art in data as well as in theory and, therefore, can be of direct use in reactor calculations. 44 refs., 21 figs., 8 tabs

Electron-volt spectroscopy at a pulsed neutron source using a resonance detector technique

CERN Document Server

Andreani, C; Senesi, R; Gorini, G; Tardocchi, M; Bracco, A; Rhodes, N; Schooneveld, E M

2002-01-01

The effectiveness of the neutron resonance detector spectrometer for deep inelastic neutron scattering measurements has been assessed by measuring the Pb scattering on the eVS spectrometer at ISIS pulsed neutron source and natural U foils as (n,gamma) resonance converters. A conventional NaI scintillator with massive shielding has been used as gamma detector. A neutron energy window up to 90 eV, including four distinct resonance peaks, has been assessed. A net decrease of the intrinsic width of the 6.6 eV resonance peak has also been demonstrated employing the double difference spectrum technique, with two uranium foils of different thickness.

Neutron absorbers and detector types for spent fuel verification using the self-interrogation neutron resonance densitometry

International Nuclear Information System (INIS)

Rossa, Riccardo; Borella, Alessandro; Labeau, Pierre-Etienne; Pauly, Nicolas; Meer, Klaas van der

2015-01-01

The Self-Interrogation Neutron Resonance Densitometry (SINRD) is a passive non-destructive assay (NDA) technique that is proposed for the direct measurement of 239 Pu in a spent fuel assembly. The insertion of neutron detectors wrapped with different neutron absorbing materials, or neutron filters, in the central guide tube of a PWR fuel assembly is envisaged to measure the neutron flux in the energy region close to the 0.3 eV resonance of 239 Pu. In addition, the measurement of the fast neutron flux is foreseen. This paper is focused on the determination of the Gd and Cd neutron filters thickness to maximize the detection of neutrons within the resonance region. Moreover, several detector types are compared to identify the optimal condition and to assess the expected total neutron counts that can be obtained with the SINRD measurements. Results from Monte Carlo simulations showed that ranges between 0.1–0.3 mm and 0.5–1.0 mm ensure the optimal conditions for the Gd and Cd filters, respectively. Moreover, a 239 Pu fission chamber is better suited to measure neutrons close to the 0.3 eV resonance and it has the highest sensitivity to 239 Pu, in comparison with a 235 U fission chamber, with a 3 He proportional counter, and with a 10 B proportional counter. The use of a thin Gd filter and a thick Cd filter is suggested for the 239 Pu and 235 U fission chambers to increase the total counts achieved in a measurement, while a thick Gd filter and a thin Cd filter are envisaged for the 3 He and 10 B proportional counters to increase the sensitivity to 239 Pu. We concluded that an optimization process that takes into account measurement time, filters thickness, and detector size is needed to develop a SINRD detector that can meet the requirement for an efficient verification of spent fuel assemblies

Neutron absorbers and detector types for spent fuel verification using the self-interrogation neutron resonance densitometry

Energy Technology Data Exchange (ETDEWEB)

Rossa, Riccardo, E-mail: rrossa@sckcen.be [SCK-CEN, Belgian Nuclear Research Centre, Boeretang, 200, B2400 Mol (Belgium); Université libre de Bruxelles, Ecole polytechnique de Bruxelles, Service de Métrologie Nucléaire (CP 165/84), Avenue F.D. Roosevelt, 50, B1050 Brussels (Belgium); Borella, Alessandro, E-mail: aborella@sckcen.be [SCK-CEN, Belgian Nuclear Research Centre, Boeretang, 200, B2400 Mol (Belgium); Labeau, Pierre-Etienne, E-mail: pelabeau@ulb.ac.be [Université libre de Bruxelles, Ecole polytechnique de Bruxelles, Service de Métrologie Nucléaire (CP 165/84), Avenue F.D. Roosevelt, 50, B1050 Brussels (Belgium); Pauly, Nicolas, E-mail: nipauly@ulb.ac.be [Université libre de Bruxelles, Ecole polytechnique de Bruxelles, Service de Métrologie Nucléaire (CP 165/84), Avenue F.D. Roosevelt, 50, B1050 Brussels (Belgium); Meer, Klaas van der, E-mail: kvdmeer@sckcen.be [SCK-CEN, Belgian Nuclear Research Centre, Boeretang, 200, B2400 Mol (Belgium)

2015-08-11

The Self-Interrogation Neutron Resonance Densitometry (SINRD) is a passive non-destructive assay (NDA) technique that is proposed for the direct measurement of {sup 239}Pu in a spent fuel assembly. The insertion of neutron detectors wrapped with different neutron absorbing materials, or neutron filters, in the central guide tube of a PWR fuel assembly is envisaged to measure the neutron flux in the energy region close to the 0.3 eV resonance of {sup 239}Pu. In addition, the measurement of the fast neutron flux is foreseen. This paper is focused on the determination of the Gd and Cd neutron filters thickness to maximize the detection of neutrons within the resonance region. Moreover, several detector types are compared to identify the optimal condition and to assess the expected total neutron counts that can be obtained with the SINRD measurements. Results from Monte Carlo simulations showed that ranges between 0.1–0.3 mm and 0.5–1.0 mm ensure the optimal conditions for the Gd and Cd filters, respectively. Moreover, a {sup 239}Pu fission chamber is better suited to measure neutrons close to the 0.3 eV resonance and it has the highest sensitivity to {sup 239}Pu, in comparison with a {sup 235}U fission chamber, with a {sup 3}He proportional counter, and with a {sup 10}B proportional counter. The use of a thin Gd filter and a thick Cd filter is suggested for the {sup 239}Pu and {sup 235}U fission chambers to increase the total counts achieved in a measurement, while a thick Gd filter and a thin Cd filter are envisaged for the {sup 3}He and {sup 10}B proportional counters to increase the sensitivity to {sup 239}Pu. We concluded that an optimization process that takes into account measurement time, filters thickness, and detector size is needed to develop a SINRD detector that can meet the requirement for an efficient verification of spent fuel assemblies.

The resonance neutron fission on heavy nuclei

International Nuclear Information System (INIS)

Kopach, Yu.N.; Popov, A.B.; Furman, V.I.; Alfimenkov, V.P.; Lason', L.; Pikel'ner, L.B.; ); Gonin, N.N.; Kozlovskij, L.K.; Tambovtsev, D.I.; Gagarskij, A.M.; Petrov, G.A.; Sokolov, V.E.

2001-01-01

A new approach to the description of the fission, similar to the well-known reaction theory and based on the helicity representation for the exit fission channels, is briefly summarized. This approach allows one to connect the multimodal fission representation with A. Bohr's concept of the fission transition states and to obtain formulae for the partial and differential fission cross sections. The formulae are used for analysis of the angular anisotropy of fragments in the neutron resonance induced fission of aligned 235 U nuclei and of the P-even angular forward-backward and right-left correlations of fragments oe the P-odd correlations caused by the interference of s- and p-wave neutron resonances [ru

The direct neutron decay of giant resonances in 208Pb

International Nuclear Information System (INIS)

Bracco, A.

1988-01-01

The neutron decay of the giant multipole resonance region from 9 to 15 MeV of excitation energy in 208 Pb has been studied. Neutron branching ratios for the decay to the ground state and to the low-lying excited states of 207 Pb were measured as a function of the excitation energy of 208 Pb and compared to Hauser-Feshbach calculations. While the neutron branching ratios from the energy region of the isoscalar giant quadrupole resonance are reproduced by the calculations, the ratios from the energy region of the isoscalar giant monopole resonance show a conspicuous excess with respect to the statistical model predictions. The neutron yield from this energy region was analysed in terms of a multistep model of the compound nucleus which includes collective doorway channels. The total direct escape width as well as the associated direct partial escape widths to the lowest five valence hole states of 207 Pb were determined. (orig.)

Measurements and applications of neutron multiple scattering in resonance region

International Nuclear Information System (INIS)

Ohkubo, Makio

1977-02-01

Capture yield of neutrons impinging on a thick material is complicated due to self-shielding and multiple scattering, especially in the resonance region. When the incident neutron energy is equal to a resonance energy of the material, capture probability of the neutron increases with sample thickness and reaches a saturation value P sub(CO). There is a simple relation between P sub(CO) and GAMMA sub(n)/GAMMA and the recoil energy by the Monte-Carlo calculation. To examine validity of the relation, P sub(CO) was measured for 19 resonances in 12 nuclides with thick samples, using a JAERI linac time-of-flight spectrometer with Moxon-Rae type gamma ray detector and transmission type neutron flux monitor. Results of the measurements confirmed the validity. With this relation, the GAMMA sub(n)/GAMMA or GAMMA sub(γ)/GAMMA value can be obtained from the measured P sub(CO), and also the level spins be determined by combining the transmission data. Because of the definition of P sub(CO), determination of the resonance parameters is not sensitive to the sample thickness as far as it is sufficiently thick. (auth.)

Spatially resolved remote measurement of temperature by neutron resonance absorption

Energy Technology Data Exchange (ETDEWEB)

Tremsin, A.S., E-mail: ast@ssl.berkeley.edu [Space Sciences Laboratory, University of California at Berkeley, 7 Gauss Way, Berkeley, CA 94720 (United States); Kockelmann, W.; Pooley, D.E. [STFC, Rutherford Appleton Laboratory, ISIS Facility, Didcot OX11 0QX (United Kingdom); Feller, W.B. [NOVA Scientific, Inc., 10 Picker Road, Sturbridge, MA 01566 (United States)

2015-12-11

Deep penetration of neutrons into most engineering materials enables non-destructive studies of their bulk properties. The existence of sharp resonances in neutron absorption spectra enables isotopically-resolved imaging of elements present in a sample, as demonstrated by previous studies. At the same time the Doppler broadening of resonance peaks provides a method of remote measurement of temperature distributions within the same sample. This technique can be implemented at a pulsed neutron source with a short initial pulse allowing for the measurement of the energy of each registered neutron by the time of flight technique. A neutron counting detector with relatively high timing and spatial resolution is used to demonstrate the possibility to obtain temperature distributions across a 100 µm Ta foil with ~millimeter spatial resolution. Moreover, a neutron transmission measurement over a wide energy range can provide spatially resolved sample information such as temperature, elemental composition and microstructure properties simultaneously.

Resonance effects in neutron scattering lengths

Energy Technology Data Exchange (ETDEWEB)

Lynn, J.E.

1989-06-01

The nature of neutron scattering lengths is described and the nuclear effects giving rise to their variation is discussed. Some examples of the shortcomings of the available nuclear data base, particularly for heavy nuclei, are given. Methods are presented for improving this data base, in particular for obtaining the energy variation of the complex coherent scattering length from long to sub-/angstrom/ wave lengths from the available sources of slow neutron cross section data. Examples of this information are given for several of the rare earth nuclides. Some examples of the effect of resonances in neutron reflection and diffraction are discussed. This report documents a seminar given at Argonne National Laboratory in March 1989. 18 refs., 18 figs.

Resonance effects in neutron scattering lengths

International Nuclear Information System (INIS)

Lynn, J.E.

1989-01-01

The nature of neutron scattering lengths is described and the nuclear effects giving rise to their variation is discussed. Some examples of the shortcomings of the available nuclear data base, particularly for heavy nuclei, are given. Methods are presented for improving this data base, in particular for obtaining the energy variation of the complex coherent scattering length from long to sub-angstrom wave lengths from the available sources of slow neutron cross section data. Examples of this information are given for several of the rare earth nuclides. Some examples of the effect of resonances in neutron reflection and diffraction are discussed. This report documents a seminar given at Argonne National Laboratory in March 1989. 18 refs., 18 figs

Evaluation of Cm-247 neutron cross sections in the resonance region

International Nuclear Information System (INIS)

Martinelli, T.; Menapace, E.; Motta, M.; Vaccari, M.

1980-01-01

The neutron cross sections of Cm-247 are evaluated in the resonance (resolved and unresolved) region up to 10 keV. Average resonance parameters (i.e. spacing D, fission and radiative widths, neutron strength functions) are determined for unresolved region calculations. Moreover for a better comparison with the experimental data, fission cross section is calculated up to 10 MeV. In addition, the average number of neutrons emitted per fission as a function of energy is estimated

MCRTOF, Multiple Scattering of Resonance Region Neutron in Time of Flight Experiments

International Nuclear Information System (INIS)

Ohkubo, Mako

1984-01-01

1 - Description of program or function: Multiple scattering of neutrons in the resonance energy region impinging on a disk with an arbitrary angle. 2 - Method of solution: The Monte Carlo method is employed to simulate the path of an incident neutron in a medium for which macroscopic cross sections are determined by resonance parameters. By tracing a large number of neutrons, probabilities for capture, transmission, front-face scattering, rear-face scattering and side-face scattering are determined and printed out as function of incident neutron energy. Optionally, the distribution of capture locations in the disk can be printed. The incident neutron energy is swept to fit a situation as encountered in time-of-flight experiments. 3 - Restrictions on the complexity of the problem: The cross section file is constructed from input resonance parameters with a single- level Breit-Wigner formula. The following restrictions and simplifications apply: - The maximum number of resonances is five. - Reactions other than capture and scattering are neglected. - The angular scattering distribution in the center-of-mass system is assumed to be uniform. - Chemical binding effects are neglected

Development of resonant detectors for epithermal neutron spectroscopy at pulsed neutron sources

International Nuclear Information System (INIS)

Tardocchi, M.; Pietropaolo, A.; Senesi, R.; Andreani, C.; Gorini, G.

2004-01-01

New perspectives for epithermal neutron spectroscopy are opened by the development of new detectors for inverse geometry time of flight spectrometers at pulsed neutron sources. One example is the Very Low Angle Detector (VLAD) bank planned to be delivered, within the next 4 years, within the eVERDI project, on the neutron spectrometer VESUVIO, at the ISIS pulsed neutron source (UK). VLAD will extend the (q,ω) kinematical region for neutron scattering to low wavefactor transfer (q -1 ) still keeping energy transfer >1 eV, thus allowing the investigations of new experimental studies in condensed matter systems. The technique being developed for detection of epithermal neutrons, within this low q and high-energy transfer region, is the Resonance Detection Technique. In this work, the state of the detector development will be presented with special focus on the results obtained with some prototype detectors, namely YAP scintillators and cadmium-zinc-telluride semiconductors

Continuous neutron slowing down theory applied to resonances

International Nuclear Information System (INIS)

Segev, M.

1977-01-01

Neutronic formalisms that discretize the neutron slowing down equations in large numerical intervals currently account for the bulk effect of resonances in a given interval by the narrow resonance approximation (NRA). The NRA reduces the original problem to an efficient numerical formalism through two assumptions: resonance narrowness with respect to the scattering bands in the slowing down equations and resonance narrowness with respect to the numerical intervals. Resonances at low energies are narrow neither with respect to the slowing down ranges nor with respect to the numerical intervals, which are usually of a fixed lethargy width. Thus, there are resonances to which the NRA is not applicable. To stay away from the NRA, the continuous slowing down (CSD) theory of Stacey was invoked. The theory is based on a linear expansion in lethargy of the collision density in integrals of the slowing down equations and had notable success in various problems. Applying CSD theory to the assessment of bulk resonance effects raises the problem of obtaining efficient quadratures for integrals involved in the definition of the so-called ''moderating parameter.'' The problem was solved by two approximations: (a) the integrals were simplified through a rationale, such that the correct integrals were reproduced for very narrow or very wide resonances, and (b) the temperature-broadened resonant line shapes were replaced by nonbroadened line shapes to enable analytical integration. The replacement was made in such a way that the integrated capture and scattering probabilities in each resonance were preserved. The resulting formalism is more accurate than the narrow-resonance formalisms and is equally as efficient

Neutron resonances in the compound nucleus: Parity nonconservation to dynamic temperature measurements

International Nuclear Information System (INIS)

Yuan, V.W.

1997-08-01

Experiments using epithermal neutrons that interact to form compound-nuclear resonances serve a wide range of scientific applications. Changes in transmission which are correlated to polarization reversal in incident neutrons have been used to study parity nonconservation in the compound nucleus for a wide range of targets. The ensemble of measured parity asymmetries provides statistical information for the extraction of the rms parity-violating mean-square matrix element as a function of mass. Parity nonconservation in neutron resonances can also be used to determine the polarization of neutron beams. Finally the motion of target atoms results in an observed temperature-dependent Doppler broadening of resonance line widths. This broadening can be used to determine temperatures on a fast time scale of one microsecond or less

Neutron strength functions: the link between resolved resonances and the optical model

International Nuclear Information System (INIS)

Moldauer, P.A.

1980-01-01

Neutron strength functions and scattering radii are useful as energy and channel radius independent parameters that characterize neutron scattering resonances and provide a connection between R-matrix resonance analysis and the optical model. The choice of R-matrix channel radii is discussed, as are limitations on the accuracies of strength functions. New definitions of the p-wave strength function and scattering radius are proposed. For light nuclei, where strength functions display optical model energy variations over the resolved resonances, a doubly reduced partial neutron width is introduced for more meaningful statistical analyses of widths. The systematic behavior of strength functions and scattering radii is discussed

Neutron slowing down in the resonance region

International Nuclear Information System (INIS)

Matausek, M.V.

1971-01-01

This paper describes the procedure for solving space, lethargy and angular dependent transport equation for resonant neutrons in cylindrical infinite reactor lattice cell. The procedure is suitable for practical application on its own or in combination with some more complex procedure

Investigation of neutron resonances of 247Cm in the 0.5-20 eV energy range

International Nuclear Information System (INIS)

Belanova, T.S.; Kolesov, A.G.; Klinov, A.V.; Nikol'skij, S.N.; Poruchikov, V.A.; Nefedov, V.N.; Artamonov, V.S.; Ivanov, R.N.; Kalebin, S.M.

1979-01-01

The neutron resonance parameters of 247 Cm were calculated from the transmission of a curium sample measured by the time-of-flight method. The neutron resonance parameters were calculated by the shape method using the single-level Breit-Wigner formula. Since the neutron resonance parameters of 244 Cm, 245 Cm, 246 Cm, 248 Cm, 243 Am and 240 Pu are well known, it was possible to identify the neutron resonances of 247 Cm from the measured transmission and calculate their parameters. We identified only five neutron resonances of 247 Cm with high values of 2gGAMMAsub(n). This is due to the fact that the 247 Cm content of the sample is low (1.7mg) and the resonances of this isotope are identified against the background of a large number of resonances of 244 Cm, 245 Cm, 246 Cm, 248 Cm, 243 Am and 240 Pu situated in the energy range in question

Neutron-neutron-resonance logging of boron in boreholes with the use of the PRKS-2 radiometer

International Nuclear Information System (INIS)

Vakhtin, B.S.; Ivanov, V.S.; Filippov, E.M.; Novoselov, A.V.

1973-01-01

The well rig of the PRKS-2 logging radiometer is supplemented with a probe device for neutron measurements permitting to vary the probe size from 20 to 45 cm. To decrease the natural gamma radiation effect an external lead shield 7-mm thick having 50-mm outer diameter is fixed on the instrument sleeve. The instrument is provided with a NaI detector and a set of foils of Cd, Ag, Rh, Tu, In, Ta, and a Pu-Be source of 1x10 6 n/sec strength. The optimal size of the probe is assumed as 25 cm. From the results of well measurements a better differentiation of neutron resonance logging was noticed in comparison with neutron gamma logging. Comparing the data obtained with those of kern analysis a calibration curve was derived of neutron resonance logging versus B for wells of 59 mm dia

Energy-resolved fast neutron resonance radiography at CSNS

Science.gov (United States)

Tan, Zhixin; Tang, Jingyu; Jing, Hantao; Fan, Ruirui; Li, Qiang; Ning, Changjun; Bao, Jie; Ruan, Xichao; Luan, Guangyuan; Feng, Changqin; Zhang, Xianpeng

2018-05-01

The white neutron beamline at the China Spallation Neutron Source will be used mainly for nuclear data measurements. It will be characterized by high flux and broad energy spectra. To exploit the beamline as a neutron imaging source, we propose a liquid scintillator fiber array for fast neutron resonance radiography. The fiber detector unit has a small exposed area, which will limit the event counts and separate the events in time, thus satisfying the requirements for single-event time-of-flight (SEToF) measurement. The current study addresses the physical design criteria for ToF measurement, including flux estimation and detector response. Future development and potential application of the technology are also discussed.

YAP scintillators for resonant detection of epithermal neutrons at pulsed neutron sources

International Nuclear Information System (INIS)

Tardocchi, M.; Gorini, G.; Pietropaolo, A.; Andreani, C.; Senesi, R.; Rhodes, N.; Schooneveld, E. M.

2004-01-01

Recent studies indicate the resonance detector (RD) technique as an interesting approach for neutron spectroscopy in the electron volt energy region. This work summarizes the results of a series of experiments where RD consisting of YAlO 3 (YAP) scintillators were used to detect scattered neutrons with energy in the range 1-200 eV. The response of YAP scintillators to radiative capture γ emission from a 238 U analyzer foil was characterized in a series of experiments performed on the VESUVIO spectrometer at the ISIS pulsed neutron source. In these experiments a biparametric data acquisition allowed the simultaneous measurements of both neutron time-of-flight and γ pulse height (energy) spectra. The analysis of the γ pulse height and neutron time of flight spectra permitted to identify and distinguish the signal and background components. These measurements showed that a significant improvement in the signal-to-background ratio can be achieved by setting a lower level discrimination on the pulse height at about 600 keV equivalent photon energy. Present results strongly indicate YAP scintillators as the ideal candidate for neutron scattering studies with epithermal neutrons at both very low (<5 deg.) and intermediate scattering angles

Neutron resonance spectroscopy on 113Cd: The p-wave levels

International Nuclear Information System (INIS)

Frankle, C.M.; Bowman, C.D.; Bowman, J.D.; Seestrom, S.J.; Sharapov, E.I.; Popov, Y.P.; Roberson, N.R.

1992-01-01

Weak levels in the compound nucleus 114 Cd were located by neutron time-of-flight spectroscopy techniques. Neutron capture measurements were performed with both a natural cadmium target and a highly enriched 113 Cd target. A total of 22 new resonances were located in the neutron energy interval 20-500 eV and were assumed to be p-wave. Resonance parameters, E 0 and gΓ n , are given for the newly identified levels. The p-wave strength function was determined to be 10 4 S 1 =2.8±0.8 and the average level spacing left-angle D 1 right-angle=14 eV. Comparison of the reduced widths with a Porter-Thomas distribution is consistent with having missed 15% of the p-wave levels

Neutron multiwave interference with many resonance coils: a test experiment

Energy Technology Data Exchange (ETDEWEB)

Chetverikov, Yu.O.; Axelrod, L.A.; Syromyatnikov, A.V.; Kraan, W.H.; Rekveldt, M.Th.; Grigoriev, S.V

2004-07-15

A test experiment on neutron multiwave interference based on Ramsey's resonance method of 'separated oscillating fields' has been performed. A neutron passes through N successive resonant coils (h{omega}{sub 0}=2{mu}{sub n}B{sub 0}), which flip the neutron spin with a probability {rho} smaller than 1. These coils are separated by path lengths L, over which a homogeneous field B{sub 1} is present. Since the spin-flip probability {rho} is smaller than 1, the number of waves for a neutron is doubled after each flipper, so as to produce 2{sup N} neutron waves at the end of the setup. The phase difference between any pair of waves is a multiple of a 'phase quantum' determined by the line integral of the field difference B{sub 1}-B{sub 0} over the length L. Highly regular patterns of the quantum mechanical probability R in (B{sub 1},{rho})--space appear owing to pairwise interference between individual waves.

Neutron resonance radiography: Report of a workshop, Los Alamos, NM: July 27-29, 1987

International Nuclear Information System (INIS)

1988-07-01

Neutron resonance radiography is a new technique with great potential for non-destructive analysis and testing. This technique has been under research and development in a number of major research laboratories for some time. Unlike thermal neutron radiography, which is primarily oriented towards imaging hydrogen and a number of other highly neutron-absorptive materials without necessarily distinguishing between them, neutron resonance radiography has the capability of uniquely identifying many kinds of chemical elements and their individual isotopes. It also has the potential for temperature imaging in materials containing heavy elements and for certain dynamic features such as stroboscopic imaging. Although neutron resonance radiography has not yet been taken up in a systematic way for technological applications, significant development of ideas and instrumentation at the research level has blossomed. There have also been major developments in the availability of powerful pulsed-neutron sources. In light of these developments, the Los Alamos Neutron Scattering Center sponsored a workshop with the general aims of reviewing scientific and technical progress, discussing and highlighting future developments, and stimulating interest in technological exploitation of the methods. In addition to the techniques and instrumentation required for the field, the applications of neutron resonance radiography in some of the following industrial and manufacturing areas were discussed: nuclear fuel assay; nuclear safeguards in general; aerospace development (aeroengine blade temperature, stroboscopic techniques); diagnostics; non-nuclear industry (especially metallurgy); temperature imaging; use of mobile pulsed-neutron sources; and practical use of major pulsed-neutron facilities

The measurements of parity violation in resonant neutron-capture reactions

International Nuclear Information System (INIS)

Sharapov, E.I.; Popov, Y.P.; Wender, S.A.; Seestrom, S.J.; Bowman, C.D.; Postma, H.; Gould, C.R.; Wasson, A.

1990-01-01

The study of parity violation in total (n,γ) cross sections on 139 La and 117 Sn targets was performed at the LANSCE pulsed neutron source using longitudinally polarized neutrons and a BaF 2 detector. The effect of parity nonconservation in the 139 La(n,γ) reaction for the resonance at E n =0.73 eV was confirmed. New results for p-wave resonances in the 117 Sn(n, γ) reaction were obtained. A comparison between the capture and transmission techniques is presented. 12 refs., 5 figs., 1 tab

Overlapping β decay and resonance neutron spectroscopy

International Nuclear Information System (INIS)

Raman, S.; Fogelberg, B.

1984-01-01

By carrying out a detailed study of 87 Kr levels, we have shown that delayed neutron spectroscopy can be a viable method for studying individual levels and that a broad resonance-like structure is present in the β-strength distribution. 12 refs., 1 fig

Partial radiative capture of resonance neutrons

International Nuclear Information System (INIS)

Samour, C.

1969-01-01

The radiative capture of resonance neutrons has been studied near the Saclay linac between 0.5 and 700 eV with time-of-flight method and a Ge(Li) detector. 195 Pt + n and 183 W + n allow the study of the distribution of partial radiative widths and their eventual correlation and also the variation of γ i > with E γ . The mean values of Ml and El transition intensities are compared in several tin isotopes. Interference effects, either between resonances or between direct capture and resonant capture are found in 195 Pt + n, 197 Au + n and 59 Co + n. The excited level schemes of a great deal of nuclei are obtained and compared with theoretical predictions. This study has been completed by an analysis of thermal spectrum. (author) [fr

Research of isolated resonances using the average energy shift method for filtered neutron beam

International Nuclear Information System (INIS)

Gritzay, O.O.; Grymalo, A.K.; Kolotyi, V.V.; Mityushkin, O.O.; Venediktov, V.M.

2010-01-01

This work is devoted to detailed description of one of the research directions in the Neutron Physics Department (NPD), namely, to research of resonance parameters of isolated nuclear level at the filtered neutron beam on the horizontal experimental channel HEC-8 of the WWR-M reactor. Research of resonance parameters is an actual problem nowadays. This is because there are the essential differences between the resonance parameter values in the different evaluated nuclear data library (ENDL) for many nuclei. Research of resonance parameter is possible due to the set of the neutron cross sections received at the same filter, but with the slightly shifted filter average energy. The shift of the filter average energy is possible by several processes. In this work this shift is realized by neutron energy dependence on scattering angle. This method is provided by equipment.

Neutron Capture and Transmission Measurements and Resonance Parameter Analysis of Samarium

International Nuclear Information System (INIS)

Leinweber, G.; Burke, J.A.; Knox, H.D.; Drindak, N.J.; Mesh, D.W.; Haines, W.T.; Ballad, R.V.; Block, R.C.; Slovacek, R.E.; Werner, C.J.; Trbovich, M.J.; Barry, D.P.; Sato, T.

2001-01-01

The purpose of the present work is to accurately measure the neutron cross sections of samarium. The most significant isotope is 149 Sm, which has a large neutron absorption cross section at thermal energies and is a 235 U fission product with a 1% yield. Its cross sections are thus of concern to reactor neutronics. Neutron capture and transmission measurements were performed by the time-of-flight technique at the Rensselaer Polytechnic institute (RPI) LINAC facility using metallic and liquid Sm samples. The capture measurements were made at the 25 meter flight station with a multiplicity-type capture detector, and the transmission total cross-section measurements were performed at 15- and 25-meter flight stations with 6 Li glass scintillation detectors. Resonance parameters were determined by a combined analysis of six experiments (three capture and three transmission) using the multi-level R-matrix Bayesian code SAMMY version M2. The significant features of this work are as follows. Dilute samples of samarium nitrate in deuterated water (D 2 O) were prepared to measure the strong resonances at 0.1 and 8 eV without saturation. Disk-shaped spectroscopic quartz cells were obtained with parallel inner surfaces to provide a uniform thickness of solution. The diluent feature of the SAMMY program was used to analyze these data. The SAMMY program also includes multiple scattering corrections to capture yield data and resolution functions specific to the RPI facility. Resonance parameters for all stable isotopes of samarium were deduced for all resonances up to 30 eV. Thermal capture cross-section and capture resonance integral calculations were made using the resultant resonance parameters and were compared to results obtained using resonance parameters from ENDF/B-VI updated through release 3. Extending the definition of the capture resonance integral to include the strong 0.1 eV resonance in 149 Sm, present measurements agree within estimated uncertainties with En

Method for analysis of averages over transmission energy of resonance neutrons

International Nuclear Information System (INIS)

Komarov, A.V.; Luk'yanov, A.A.

1981-01-01

Experimental data on transmissions on iron specimens in different energy groups have been analyzed on the basis of an earlier developed theoretical model for the description of resonance neutron averages in transmission energy, as the functions of specimen thickness and mean resonance parameters. The parameter values obtained agree with the corresponding data evaluated in the theory of mean neutron cross sections. The method suggested for the transmission description permits to reproduce experimental results for any thicknesses of specimens [ru

Determination of space-energy distribution of resonance neutrons in reactor lattice cell and calculation of resonance integrals

International Nuclear Information System (INIS)

Zmijarevic, I.

1980-01-01

Space-energy distribution of resonance neutrons in reactor lattice cell was determined by solving the Boltzmann equation by spherical harmonics method applying P-3 approximation. Computer code SPLET used for these calculations is described. Resonance absorption and calculation of resonance integrals are described as well. Effective resonance integral values for U-238 resonance at 6.7 Ev are calculated for heavy water reactor cell with metal, oxide and carbide fuel elements

Resonantly scattering crystals and surfaces

International Nuclear Information System (INIS)

Gunn, J.M.F.; Mahon, P.J.

1990-12-01

We examine coherence effects from forming a crystal of resonant scatterers by generalising the Fano model for autoionising resonances in electron scattering from atoms to a lattice of such scatterers. (We have in mind the case of neutron scattering from nuclei.) We solve this problem to yield two branches to the dispersion relation for the neutron in general and three when the resonance coincides with a Brillouin Zone boundary. The 'width' of the resonance is enhanced over the isolated nucleus, the best candidate for observation being the 2eV 185 Re resonance near the Bragg condition. We use these results to calculate the reflection coefficient from a surface, revealing total external reflection near resonance. We discuss experimental feasibility in both the neutron and electron cases. (author)

Resonant enhancement in leptogenesis

Science.gov (United States)

Dev, P. S. B.; Garny, M.; Klaric, J.; Millington, P.; Teresi, D.

2018-02-01

Vanilla leptogenesis within the type I seesaw framework requires the mass scale of the right-handed neutrinos to be above 109 GeV. This lower bound can be avoided if at least two of the sterile states are almost mass degenerate, which leads to an enhancement of the decay asymmetry. Leptogenesis models that can be tested in current and upcoming experiments often rely on this resonant enhancement, and a systematic and consistent description is therefore necessary for phenomenological applications. In this paper, we give an overview of different methods that have been used to study the saturation of the resonant enhancement when the mass difference becomes comparable to the characteristic width of the Majorana neutrinos. In this limit, coherent flavor transitions start to play a decisive role, and off-diagonal correlations in flavor space have to be taken into account. We compare various formalisms that have been used to describe the resonant regime and discuss under which circumstances the resonant enhancement can be captured by simplified expressions for the CP asymmetry. Finally, we briefly review some of the phenomenological aspects of resonant leptogenesis.

Neutron resonance parameters of 96Zr below 100 keV

International Nuclear Information System (INIS)

Musgrove, A.R.D.

1977-08-01

Transmission data taken at the 80 m station of the Oak Ridge Electron Linear Accelerator have provided resonance parameters for 96 Zr to 100 keV. The average level spacing and neutron strength function for s-wave neutrons were as follows: = 8 +- 2 keV and S 0 = (0.21 +- 0.10) x 10 -4 . The average p-wave neutron strength function was S 1 = (7.4 +- 2.0) x 10 -4 . (Author)

Neutron Spin Resonance in the 112-Type Iron-Based Superconductor

Science.gov (United States)

Xie, Tao; Gong, Dongliang; Ghosh, Haranath; Ghosh, Abyay; Soda, Minoru; Masuda, Takatsugu; Itoh, Shinichi; Bourdarot, Frédéric; Regnault, Louis-Pierre; Danilkin, Sergey; Li, Shiliang; Luo, Huiqian

2018-03-01

We use inelastic neutron scattering to study the low-energy spin excitations of the 112-type iron pnictide Ca0.82La0.18Fe0.96Ni0.04As2 with bulk superconductivity below Tc=22 K . A two-dimensional spin resonance mode is found around E =11 meV , where the resonance energy is almost temperature independent and linearly scales with Tc along with other iron-based superconductors. Polarized neutron analysis reveals the resonance is nearly isotropic in spin space without any L modulations. Because of the unique monoclinic structure with additional zigzag arsenic chains, the As 4 p orbitals contribute to a three-dimensional hole pocket around the Γ point and an extra electron pocket at the X point. Our results suggest that the energy and momentum distribution of the spin resonance does not directly respond to the kz dependence of the fermiology, and the spin resonance intrinsically is a spin-1 mode from singlet-triplet excitations of the Cooper pairs in the case of weak spin-orbital coupling.

Design of a boron neutron capture enhanced fast neutron therapy assembly

Energy Technology Data Exchange (ETDEWEB)

Wang, Zhonglu [Georgia Inst. of Technology, Atlanta, GA (United States)

2006-12-01

The use of boron neutron capture to boost tumor dose in fast neutron therapy has been investigated at several fast neutron therapy centers worldwide. This treatment is termed boron neutron capture enhanced fast neutron therapy (BNCEFNT). It is a combination of boron neutron capture therapy (BNCT) and fast neutron therapy (FNT). It is believed that BNCEFNT may be useful in the treatment of some radioresistant brain tumors, such as glioblastoma multiform (GBM). A boron neutron capture enhanced fast neutron therapy assembly has been designed for the Fermilab Neutron Therapy Facility (NTF). This assembly uses a tungsten filter and collimator near the patient's head, with a graphite reflector surrounding the head to significantly increase the dose due to boron neutron capture reactions. The assembly was designed using Monte Carlo radiation transport code MCNP version 5 for a standard 20x20 cm² treatment beam. The calculated boron dose enhancement at 5.7-cm depth in a water-filled head phantom in the assembly with a 5x5 cm² collimation was 21.9% per 100-ppm ¹⁰B for a 5.0-cm tungsten filter and 29.8% for a 8.5-cm tungsten filter. The corresponding dose rate for the 5.0-cm and 8.5-cm thick filters were 0.221 and 0.127 Gy/min, respectively; about 48.5% and 27.9% of the dose rate of the standard 10x10 cm² fast neutron treatment beam. To validate the design calculations, a simplified BNCEFNT assembly was built using four lead bricks to form a 5x5 cm² collimator. Five 1.0-cm thick 20x20 cm² tungsten plates were used to obtain different filter thicknesses and graphite bricks/blocks were used to form a reflector. Measurements of the dose enhancement of the simplified assembly in a water-filled head phantom were performed using a pair of tissue-equivalent ion chambers. One of the ion chambers is loaded with 1000-ppm natural boron (184-ppm ¹⁰B) to measure dose due to boron neutron capture. The

Expected total counts for the Self-Interrogation Neutron Resonance Densitometry measurements of spent nuclear fuel

Energy Technology Data Exchange (ETDEWEB)

Rossa, Riccardo [Belgian nuclear research centre SCK.CEN (Belgium); Universite Libre de Bruxelles (Belgium); Borella, Alessandro; Van der Meer, Klaas [Belgian nuclear research centre SCK.CEN. Boeretang 200, 2400 Mol (Belgium); Labeau, Pierre-Etienne; Pauly, Nicolas [Universite Libre de Bruxelles. Av. F. D. Roosevelt 50, B1050 Brussels (Belgium)

2015-07-01

The Self-Interrogation Neutron Resonance Densitometry (SINRD) is a passive neutron technique that aims at a direct quantification of {sup 239}Pu in spent fuel assemblies by measuring the attenuation of the neutron flux in the energy region close to the 0.3 eV resonance of {sup 239}Pu. The {sup 239}Pu mass is estimated by calculating the SINRD signature, that is the ratio between the neutron counts in the fast energy region and around the 0.3 eV resonance region. The SINRD measurement approach in this study consisted in introducing a small neutron detector in the central guide tube of a PWR 17x17 fuel assembly. In order to measure the neutron flux in the energy regions defined in the SINRD signature, different detector types were used. The response of a bare {sup 238}U fission chamber is considered for the determination of the fast neutron flux, while other thermal-epithermal detectors wrapped in neutron absorbers are envisaged to measure the neutron flux around the resonance region. This paper provides an estimation of the total neutron counts that can be achieved with the detector types proposed for the SINRD measurement. In the first section a set of detectors are evaluated in terms of total neutron counts and sensitivity to the {sup 239}Pu content, in order to identify the optimal measurement configuration for each detector type. Then a study is performed to increase the total neutron counts by increasing the detector size. The study shows that the highest total neutron counts are achieved by using either {sup 3}He or {sup 10}B proportional counters because of the high neutron efficiency of these detectors. However, the calculations indicate that the biggest contribution to the measurement uncertainty is due to the measurement of the fast neutron flux. Finally, similar sensitivity to the {sup 239}Pu content is obtained by using the different detector types for the measurement of the neutron flux close to the resonance region. Therefore, the total neutron counts

Thermal neutron capture and resonance integral cross sections of {sup 45}Sc

Energy Technology Data Exchange (ETDEWEB)

Van Do, Nguyen; Duc Khue, Pham; Tien Thanh, Kim [Institute of Physics, Vietnam Academy of Science and Technology, 10 Dao Tan, Hanoi (Viet Nam); Thi Hien, Nguyen [Institute of Physics, Vietnam Academy of Science and Technology, 10 Dao Tan, Hanoi (Viet Nam); Department of Physics and Center for High Energy Physics, Kyungpook National University, Daegu 702-701 (Korea, Republic of); Kim, Guinyun, E-mail: gnkim@knu.ac.kr [Department of Physics and Center for High Energy Physics, Kyungpook National University, Daegu 702-701 (Korea, Republic of); Kim, Kwangsoo [Department of Physics and Center for High Energy Physics, Kyungpook National University, Daegu 702-701 (Korea, Republic of); Shin, Sung-Gyun; Cho, Moo-Hyun [Department of Advanced Nuclear Engineering, Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of); Lee, Manwoo [Research Center, Dongnam Institute of Radiological and Medical Science, Busan 619-953 (Korea, Republic of)

2015-11-01

The thermal neutron cross section (σ{sub 0}) and resonance integral (I{sub 0}) of the {sup 45}Sc(n,γ){sup 46}Sc reaction have been measured relative to that of the {sup 197}Au(n,γ){sup 198}Au reaction by means of the activation method. High-purity natural scandium and gold foils without and with a cadmium cover of 0.5 mm thickness were irradiated with moderated pulsed neutrons produced from the Pohang Neutron Facility (PNF). The induced activities in the activated foils were measured with a high purity germanium (HPGe) detector. In order to improve the accuracy of the experimental results the counting losses caused by the thermal (G{sub th}) and resonance (G{sub epi}) neutron self-shielding, the γ-ray attenuation (F{sub g}) and the true γ-ray coincidence summing effects were made. In addition, the effect of non-ideal epithermal spectrum was also taken into account by determining the neutron spectrum shape factor (α). The thermal neutron cross-section and resonance integral of the {sup 45}Sc(n,γ){sup 46}Sc reaction have been determined relative to the reference values of the {sup 197}Au(n,γ){sup 198}Au reaction, with σ{sub o,Au} = 98.65 ± 0.09 barn and I{sub o,Au} = 1550 ± 28 barn. The present thermal neutron cross section has been determined to be σ{sub o,Sc} = 27.5 ± 0.8 barn. According to the definition of cadmium cut-off energy at 0.55 eV, the present resonance integral cross section has been determined to be I{sub o,Sc} = 12.4 ± 0.7 barn. The present results are compared with literature values and discussed.

New evaluation of 238U neutron resonance parameters

International Nuclear Information System (INIS)

Derrien, Herve; Leal, Luiz C.; Larson, Nancy M.

2003-01-01

The neutron resonance parameters of 238 U were obtained in the energy range 1 keV to 20 keV from a SAMMY Reich-Moore analysis of high resolution transmission measurements performed at ORELA. In the energy range 1 keV to 10 keV, the analysis used as prior values the ENDF/B-VI resonance parameters. The analysis in the energy range 10 keV to 20 keV resulted in the creation of a set of resonance parameters for the representation of the cross section in this energy range. The results are compared to the ENDF/B-VI evaluation. Some statistical properties of the new resonance parameters are examined. (author)

Formalism for neutron cross section covariances in the resonance region using kernel approximation

Energy Technology Data Exchange (ETDEWEB)

Oblozinsky, P.; Cho,Y-S.; Matoon,C.M.; Mughabghab,S.F.

2010-04-09

We describe analytical formalism for estimating neutron radiative capture and elastic scattering cross section covariances in the resolved resonance region. We use capture and scattering kernels as the starting point and show how to get average cross sections in broader energy bins, derive analytical expressions for cross section sensitivities, and deduce cross section covariances from the resonance parameter uncertainties in the recently published Atlas of Neutron Resonances. The formalism elucidates the role of resonance parameter correlations which become important if several strong resonances are located in one energy group. Importance of potential scattering uncertainty as well as correlation between potential scattering and resonance scattering is also examined. Practical application of the formalism is illustrated on {sup 55}Mn(n,{gamma}) and {sup 55}Mn(n,el).

Hafnium Resonance Parameter Analysis Using Neutron Capture and Transmission Experiments

International Nuclear Information System (INIS)

MJ Trbovich; DP Barry; RE Slovacck; Y Danon; RC Block; JA Burke; NJ Drindak; G Leinweber; RV Ballad

2004-01-01

The focus of this work is to determine resonance parameters for stable hafnium isotopes in the 0.005-200 eV region, with special emphasis on the overlapping 176 Hf and 178 Hf resonances near 8 eV. The large neutron cross section of hafnium, combined with its corrosion resistance and excellent mechanical properties, make it a useful material for controlling nuclear reactions. Experiments measuring neutron capture and transmission were performed at the Rensselaer Polytechnic Institute (RPI) electron linear accelerator (LINAC) using the time of flight method. 6 Li glass scintillation detectors were used for transmission experiments at flight path lengths of 15 and 25 m. Capture experiments were done using a sixteen section NaI(Tl) multiplicity detector at a flight path length of 25 m. These experiments utilized various thicknesses of metallic and isotopically-enriched liquid samples. The liquid samples were designed to provide information on the 176 Hf and 178 Hf contributions to the 8 eV doublet without saturation. Data analysis was done using the R-matrix Bayesian code SAMMY version M6 beta. SAMMY is able to account for experimental resolution effects for each of the experimental setups at the RPI LINAC, and also can correct for multiple scattering effects in neutron capture yield data. The combined capture and transmission data analysis yielded resonance parameters for all hafnium isotopes from 0.005-200 eV. Resonance integrals were calculated along with errors for each hafnium isotope using the NJOY [1] and INTER [2] codes. The isotopic resonance integrals calculated were significantly different than previously published values; however the calculated elemental hafnium resonance integral changed very little

Determination of the neutron resonance parameters for 206Pb and of the thermal neutron capture cross section for 206Pb and 209Bi

International Nuclear Information System (INIS)

Borella, A.

2005-01-01

Chapter 1 describes the motivation of the measurements (accelerator driven systems, stellar nucleosynthesis, neutron induced reactions on 206 Pb), the present status of the neutron capture data for 206 Pb and 209 Bi and the structure of this work. In Chapter 2 the basic reaction theory underlying this work is described. The neutron induced reaction mechanism and formalism are explained. The parameterisation of the cross section in terms of R-matrix theory is discussed and we put particular emphasis on the statistical behaviour of the resonance parameters and the impact of the angular distribution of gamma rays following neutron capture. The relation between experimental observables and the resonance parameters is discussed together with general comments related to resonance shape analysis. Chapter 3 is focused on the determination of resonance parameters for 206 Pb. We performed high-resolution transmission and capture measurements at the Time-Of-Flight (TOF) facility GELINA of the IRMM at Geel (B) and determined the resonance parameters. For nuclei like 206 Pb, where the total width is dominated by Γ n , the capture area allows to determine G . Transmission measurements were carried out to determine Γ n , and the statistical factor g of resonances. Before performing a Resonance Shape Analysis (RSA) on the transmission and capture data, we verified the neutron flux and resolution at GELINA. We also compared the characteristics of GELINA with those of the n-TOF facility at CERN. A special emphasis is placed on the total energy detection technique using C 6 D 6 detectors. This technique was applied for the determination of the capture cross section. To reduce systematic bias effects on the capture cross section, the response of the detectors was determined by Monte Carlo simulations, which has been validated by experiments. Using these response functions the partial capture cross sections for individual resonances of 206 Pb have been deduced, by unfolding the

A computer code for calculating neutron cross-sections from resonance parameter data

International Nuclear Information System (INIS)

Mill, A.J.

1979-08-01

A computer code, XSEC, has been written which calculates neutron cross-sections from resonance data. Although the program was originally written in order to identify neutron 'windows' in enriched nuclides, it may be used to evaluate the total neutron cross-section of any medium mass nuclide at intermediate energies. XSEC has proved very useful in identifying suitable nuclides for use as neutron filters at intermediate energies. (author)

Neutron flux calculations for criticality safety analysis using the narrow resonance approximations. Vol. 2

Energy Technology Data Exchange (ETDEWEB)

Hathout, A M [National Center for Nuclear Safety and Radiation Control, NC-NSRC, Atomic Energy Authority, Cairo (Egypt)

1996-03-01

The narrow resonance approximation is applicable for all low-energy resonances and the heaviest nuclides. It is of great importance in neutron calculations, hence, fertile isotopes do not undergo fission at resonance energies. The effect of overestimating the self shielded group averaged cross-section data for a given resonance nuclide can be fairly serious. In the present work, a detailed study, and derivation of the problem of self-shielding are carried-out through the information of Hansen-roach library which is used for criticality safety analysis. The intermediate neutron flux spectrum is analyzed, using the narrow resonance approximation. The resonance self-shielded values of various cross-sections are determined. 4 figs., 3 tabs.

Electron volt spectroscopy on a pulsed neutron source using resonance absorption filters

International Nuclear Information System (INIS)

Newport, R.J.; Williams, W.G.

1983-05-01

The design aspects of an inelastic neutron spectrometer based on energy selection by the resonance absorption filter difference method are discussed. Detailed calculations of the accessible dynamical range (Q, ω), energy and momentum transfer resolutions and representative count rates are presented for Sm and Ta resonance filters in an inverse geometry spectrometer on a high intensity pulsed source such as the RAL Spallation Neutron Source (SNS). A discussion is given of the double-difference method, which provides a means of improving the resonance attenuation peak shape. As a result of this study, as well as preliminary experimental results, recommendations are made for the future development of the technique. (author)

New neutron-based isotopic analytical methods; An explorative study of resonance capture and incoherent scattering

NARCIS (Netherlands)

Perego, R.C.

2004-01-01

Two novel neutron-based analytical techniques have been treated in this thesis, Neutron Resonance Capture Analysis (NRCA), employing a pulsed neutron source, and Neutron Incoherent Scattering (NIS), making use of a cold neutron source. With the NRCA method isotopes are identified by the

Neutron Resonance Transmission Analysis (NRTA): Initial Studies of a Method for Assaying Plutonium in Spent Fuel

Energy Technology Data Exchange (ETDEWEB)

David L. Chichester; James W. Sterbentz

2011-05-01

Neutron Resonance Transmission Analysis (NRTA) is an analytical technique that uses neutrons to assay the isotopic content of bulk materials. The technique uses a pulsed accelerator to produce an intense, short pulse of neutrons in a time-of-flight configuration. These neutrons, traveling at different speeds according to their energy, can be used to interrogate a spent fuel (SF) assembly to determine its plutonium content. Neutron transmission through the assembly is monitored as a function of neutron energy (time after the pulse), similar to the way neutron cross-section data is often collected. The transmitted neutron intensity is recorded as a function of time, with faster (higher-energy) neutrons arriving first and slower (lower-energy) neutrons arriving later. The low-energy elastic scattering and absorption resonances of plutonium and other isotopes modulate the transmitted neutron spectrum. Plutonium content in SF can be determined by analyzing this attenuation. Work is currently underway at Idaho National Laboratory, as a part of United States Department of Energy's Next Generation Safeguards Initiative (NGSI), to investigate the NRTA technique and to assess its feasibility for quantifying the plutonium content in SF and for determining the diversion of SF pins from assemblies. Preliminary results indicate that NRTA has great potential for being able to assay intact SF assemblies. Operating in the 1-40 eV range, it can identify four plutonium isotopes (239, 240, 241, & 242Pu), three uranium isotopes (235, 236, & 238U), and six resonant fission products (99Tc, 103Rh, 131Xe, 133Cs, 145Nd, and 152Sm). It can determine the areal density or mass of these isotopes in single- or multiple-pin integral transmission scans. Further, multiple observables exist to allow the detection of material diversion (pin defects) including fast-neutron and x-ray radiography, gross-transmission neutron counting, plutonium resonance absorption analysis, and fission

Future prospects of superfine structure of neutron resonance levels

International Nuclear Information System (INIS)

Ideno, Kazumi

1996-01-01

Neutron resonance spectra appear simply and regularly in the light of superfine structure (SFS). It is found that the relative shifts (i.e. the relative distances) between the SFSs for groups of nuclei have definite values and are closely interrelated to the symmetry properties of the compound systems if we treat neutron zero energy as a common reference point. An origin of the SFSs and its possible application to an evaluation of nuclear data are discussed. (author)

The isovector quadrupole resonance in yttrium excited by neutron radiative capture

International Nuclear Information System (INIS)

Zorro, R.; Bergqvist, I.

1987-01-01

In order to investigate the properties of the isovector giant quadrupole resonance (ΔT=1, ΔS=0) in the A=90 mass region, gamma-ray spectra from the reaction 89 Y(n,γ) 90 Y were recorded at several neutron energies in the energy range 12 to 27 MeV at 55 0 , 90 0 and 125 0 . The measured fore-aft asymmetry for the ground-state transition is very small in the low-energy region, but becomes appreciable above a neutron energy of 18 MeV. The observed asymmetry is attributed to interference between radiation from the isovector giant quadrupole resonance and radiation of opposite parity (from the high-energy tail of the giant dipole resonance and direct E1 capture). The data obtained in the present work, interpreted in terms of the direct-semidirect capture model, indicate that the excitation energy of the isovector E2 resonance in 90 Y is 26 ± 1 MeV. The data are consistent with a resonance width of 10 ± 2 MeV and with complete exhaustion of the energy-weighted sum rule for the lower isospin component of the resonance. (orig.)

Expected count rate for the Self- Interrogation Neutron Resonance Densitometry measurements of spent nuclear fuel

Energy Technology Data Exchange (ETDEWEB)

Rossa, Riccardo [SCK.CEN, Belgian Nuclear Research Centre, Boeretang, 200 - B2400 Mol (Belgium); Universite libre de Bruxelles, Ecole polytechnique de Bruxelles - Service de Metrologie Nucleaire, CP 165/84, Avenue F.D. Roosevelt, 50 - B1050 Brussels (Belgium); Borella, Alessandro; Van der Meer, Klaas [SCK.CEN, Belgian Nuclear Research Centre, Boeretang, 200 - B2400 Mol (Belgium); Labeau, Pierre-Etienne; Pauly, Nicolas [Universite libre de Bruxelles, Ecole polytechnique de Bruxelles - Service de Metrologie Nucleaire, CP 165/84, Avenue F.D. Roosevelt, 50 - B1050 Brussels (Belgium)

2015-07-01

The Self-Interrogation Neutron Resonance Densitometry (SINRD) is a passive neutron technique that aims at a direct quantification of {sup 239}Pu in the fuel assemblies by measuring the attenuation of the neutron flux in the energy region close to the 0.3 eV resonance of {sup 239}Pu. The {sup 239}Pu mass is estimated by calculating the SINRD signature, that is the ratio between the neutron flux integrated over the fast energy region and around the 0.3 eV resonance region. The SINRD measurement approach considered in this study consists in introducing a small neutron detector in the central guide tube of a PWR 17x17 fuel assembly. In order to measure the neutron flux in the energy regions defined in the SINRD signature, different detector types are used. The response of a bare {sup 238}U fission chamber is considered for the determination of the fast neutron flux, while other thermal-epithermal detectors wrapped in neutron absorbers are envisaged to measure the neutron flux around the resonance region. This paper provides an estimation of the count rate that can be achieved with the detector types proposed for the SINRD measurement. In the first section a set of detectors are evaluated in terms of count rate and sensitivity to the {sup 239}Pu content, in order to identify the optimal measurement configuration for each detector type. Then a study is performed to increase the count rate by increasing the detector size. The study shows that the highest count rate is achieved by using either {sup 3}He or {sup 10}B proportional counters because of the high neutron efficiency of these detectors. However, the calculations indicate that the biggest contribution to the measurement uncertainty is due to the measurement of the fast neutron flux. Finally, similar sensitivity to the {sup 239}Pu content is obtained by using the different detector types for the measurement of the neutron flux close to the resonance region. Therefore, the count rate associated to each detector type

Evaluation of thermal neutron cross-sections and resonance integrals of protactinium, americium, curium, and berkelium isotopes

International Nuclear Information System (INIS)

Belanova, T.S.

1994-12-01

Data on the thermal neutron fission and capture cross-sections as well as their corresponding resonance integrals are reviewed and analysed. The data are classified according to the form of neutron spectra under investigation. The weighted mean values of the cross-sections and resonance integrals for every type of neutron spectra were adopted as evaluated data. (author). 87 refs, 2 tabs

Study of the fluctuations of the partial and total radiative widths by neutron capture resonance method; Etude des fluctuations des largeurs radiatives partielles et totales par la capture des neutrons de resonance

Energy Technology Data Exchange (ETDEWEB)

Huynh, V D [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1965-06-01

Radiative capture experiments by neutron time-of-flight methods have been made for following studies: distribution of partial radiative widths, effects of correlation between different radiative transitions, fluctuations of total radiative widths {gamma}{sub {gamma}} from resonance to resonance, variation of {gamma}{sub {gamma}} with number of mass and the search for the existence of potential capture. Also, some other experiments with the use of neutron capture gamma-rays spectra have been investigated. (author) [French] Par la capture des neutrons de resonance dont les energies sont selectionnees a l'aide de la technique du temps de vol, differents types d'experiences ont ete realisees concernant les etudes des distributions des largeurs radiatives partielles, des effets de correlation entre differentes voies de desexcitation, de la fluctuation des largeurs radiatives totales {gamma}{sub {gamma}} de resonance a resonance, de la variation de la quantite {gamma}{sub {gamma}} en fonction du nombre de masse et de la mise en evidence de l'existence du processus de capture potentielle. Quelques autres applications de l'emploi du spectre de rayons gamma ont egalement ete presentees. (auteur)

ESTIMA, Neutron Width Level Spacing, Neutron Strength Function of S- Wave, P-Wave Resonances

International Nuclear Information System (INIS)

Fort, E.

1982-01-01

1 - Description of problem or function: ESTIMA calculates level spacing and neutron strength function of a mixed sequence of s- and p-wave resonances given a set of neutron widths as input parameters. Three algorithms are used, two of which calculate s-wave average parameters and assume that the reduced widths obey a Porter-Thomas distribution truncated by a minimum detection threshold. The third performs a maximum likelihood fit to a truncated chi-squared distribution of any specified number of degrees of freedom, i.e. it can be used for calculating s-wave or p-wave average parameters. Resonances of undeclared angular orbital momentum are divided into groups of probable s-wave and probable p-wave by a simple application of Bayes' Theorem. 2 - Method of solution: Three algorithms are used: i) GAMN method, based on simple moments properties of a Porter-Thomas distribution. ii) Missing Level Estimator, a simplified version of the algorithm used by the program BAYESZ. iii) ESTIMA, a maximum likelihood fit. 3 - Restrictions on the complexity of the problem: A maximum of 400 resonances is allowed in the version available from NEADB, however this restriction can be relaxed by increasing array dimensions

Modified model of neutron resonance widths distribution. Results of total gamma-widths approximation

International Nuclear Information System (INIS)

Sukhovoj, A.M.; Khitrov, V.A.

2011-01-01

Functional dependences of probability to observe given Γ n 0 value and algorithms for determination of the most probable magnitudes of the modified model of resonance parameter distributions were used for analysis of the experimental data on the total radiative widths of neutron resonances. As in the case of neutron widths, precise description of the Γ γ spectra requires a superposition of three and more probability distributions for squares of the random normally distributed values with different nonzero average and nonunit dispersion. This result confirms the preliminary conclusion obtained earlier at analysis of Γ n 0 that practically in all 56 tested sets of total gamma widths there are several groups noticeably differing from each other by the structure of their wave functions. In addition, it was determined that radiative widths are much more sensitive than the neutron ones to resonance wave functions structure. Analysis of early obtained neutron reduced widths distribution parameters for 157 resonance sets in the mass region of nuclei 35 ≤ A ≤ 249 was also performed. It was shown that the experimental values of widths can correspond with high probability to superposition of several expected independent distributions with their nonzero mean values and nonunit dispersion

The applicability of detailed process for neutron resonance absorption to neutronics analyses in LWR next generation fuels to extend burnup

International Nuclear Information System (INIS)

Kameyama, Takanori; Nauchi, Yasushi

2004-01-01

Neutronics analyses with detail processing for neutron resonance absorption in LWR next generation UOX and MOX fuels to extend burnup were performed based on the neutronic transport and burnup calculation. In the detailed processing, ultra-fine energy nuclear library and collision probabilities between neutron and U, Pu nuclides (actinide nuclides) are utilized for two-dimension geometry. In the usual simple processing (narrow resonance approximation), shielding factors and compensation equations for neutron resonance absorption are utilized. The results with detailed and simple processing were compared to clarify where the detailed processing is needed. The two processing caused difference of neutron multiplication factor by 0.5% at the beginning of irradiation, while the difference became smaller as burnup increased and was not significant at high burnup. The nuclide compositions of the fuel rods for main actinide nuclides were little different besides Cm isotopes by the processing, since the neutron absorption rate of 244 Cm became different. The detail processing is needed to evaluate the neutron emission rate in spent fuels. In the fuel assemblies, the distributions of rod power rates were not different within 0.5%, and the peak rates of fuel rod were almost the same by the two processing at the beginning of irradiation when the peak rate is the largest during the irradiation. The simple processing is also satisfied for safety evaluation based on the peak rate of rod power. The difference of local power densities in fuel pellets became larger as burnup increased, since the neutron absorption rate of 238 U in the peripheral region of pellets were significantly different by the two processing. The detail processing is needed to evaluate the fuel behavior at high burnup. (author)

Neutron cross sections in the unresolved resonance region

International Nuclear Information System (INIS)

Janeva, N.; Lukyanov, A.; Koyumdjieva, N.; Volev, K.

2005-01-01

In this work a development of the characteristic function model, created to reveal the resonance cross section structure in the unresolved resonance region is presented. The main advantage of this model is the calculation of resonance averaged self-shielding factors analytically. To determine average values of the cross sections and their functionals the function of joint statistical distribution of the R-matrix real and imaginary parts should be used. The characteristic function of such distribution is determined and the resonance ladder for the unresolved region is optimized to calculate the group averaged functionals in the same way as it is in the resolved resonance region. The main advantage of this model is the calculation of resonance averaged self-shielding factors analytically. The neutron width energy dependence leads to some deformation in the shape of resonances. This deformation is most apparent near the inelastic scattering threshold. For the case when the inelastic channel momentum is zero we present the formula for level shape bellow and over the inelastic threshold and the calculated resonance deformation in dependence of the position of the resonance in respect to the threshold. (authors)

Nano-structured Fabry–Pérot resonators in neutron optics and tunneling of neutron wave-particles

International Nuclear Information System (INIS)

Maaza, M.; Hamidi, D.

2012-01-01

Correlated to the quantum mechanics wave-particle duality, the optical analogy between electromagnetic waves and cold neutrons manifests itself through several interference phenomena particularly the so called Frustrated Total Reflection i.e., the tunneling process in Fabry–Pérot nano-structured cavities. Prominent resonant situations offered by this configuration allow the attainment of numerous fundamental investigations and surface-interface studies as well as to devise new kinds of neutron optics devices. This review contribution reports such possibilities in addition to the recently observed peculiar Goos–Hänchen longitudinal shift of neutron wave-particles which was predicted by Sir Isaac Newton as early as 1730.

The evaluated neutron cross sections and resonance integrals of fission products with Z = 57-62

International Nuclear Information System (INIS)

Fedorova, A.F.; Pisanko, Zh.I.; Novoselov, G.M.

1976-01-01

Neutron cross sections at a neutron velocity of V=2200 m/s, and resonance integrals for fission products with Z=57-71 are estimated. In obtaining the recommended values the results of the neutron cross sections and resonance integrals for elements used as references were normalized in accordance with the latest adjusted values. In the course of estimation, preference was given to the more accurate methods for obtaining the measured values and to the more recent investigations

The evaluated neutron cross sections and resonance integrals of fission products with Z=63-71

International Nuclear Information System (INIS)

Fedorova, A.F.; Pisanko, Zh.I.; Novoselov, G.M.

1976-01-01

Neutron cross sections at a neutron velocity of V=2200 m/s, and the resonance integrals for fission products with Z=63-71 are estimated. In obtaining the recommended values the results were normalized of the neutron cross sections and resonance integrals for elements used as references in accordance with the latest adjusted values. In the course of estimation, preference was given to the more accurate measuring methods and the more recent investigations. Scientific publications up to 1975 have been used

Study of the fluctuations of the partial and total radiative widths by neutron capture resonance method; Etude des fluctuations des largeurs radiatives partielles et totales par la capture des neutrons de resonance

Energy Technology Data Exchange (ETDEWEB)

Huynh, V.D. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1965-06-01

Radiative capture experiments by neutron time-of-flight methods have been made for following studies: distribution of partial radiative widths, effects of correlation between different radiative transitions, fluctuations of total radiative widths {gamma}{sub {gamma}} from resonance to resonance, variation of {gamma}{sub {gamma}} with number of mass and the search for the existence of potential capture. Also, some other experiments with the use of neutron capture gamma-rays spectra have been investigated. (author) [French] Par la capture des neutrons de resonance dont les energies sont selectionnees a l'aide de la technique du temps de vol, differents types d'experiences ont ete realisees concernant les etudes des distributions des largeurs radiatives partielles, des effets de correlation entre differentes voies de desexcitation, de la fluctuation des largeurs radiatives totales {gamma}{sub {gamma}} de resonance a resonance, de la variation de la quantite {gamma}{sub {gamma}} en fonction du nombre de masse et de la mise en evidence de l'existence du processus de capture potentielle. Quelques autres applications de l'emploi du spectre de rayons gamma ont egalement ete presentees. (auteur)

The resonant detector and its application to epithermal neutron spectroscopy

International Nuclear Information System (INIS)

Gorini, G.; Perelli-Cippo, E.; Tardocchi, M.; Andreani, C.; D'Angelo, A.; Pietropaolo, A.; Senesi, R.; Imberti, S.; Bracco, A.; Previtali, E.; Pessina, G.; Rhodes, N.J.; Schooneveld, E.M.

2004-01-01

New perspectives for epithermal neutron spectroscopy are being opened by the development of the resonant detector (RD) and its use on inverse geometry time of flight spectrometers at spallation sources. The RD was first proposed in the 1980s and was recently brought to a performance level exceeding conventional neutron-sensitive Li-glass scintillator detectors. It features a photon counter coupled to a neutron analyzer foil. Resonant neutron absorption in the foil results in the emission of prompt gamma rays that are detected in the photon counter. The dimensions of the RD set the spatial resolution that can be achieved, ranging from a fraction of a cm to several cm. It can thus be tailored to the construction of detector arrays of different geometry. The main results of the research on this kind of detector are reported leading to the present optimized RD design based on a combination of YAP scintillation photon counter and uranium or gold analyzer foils. This detector has already been selected for application in the upgrade of the VESUVIO spectrometer on ISIS. A special application is the Very Low Angle Detector (VLAD) bank, which will extend the kinematical region for neutron scattering to low momentum transfer ( -1 ) whilst still keeping energy transfer >1 eV, thus allowing new experimental studies in condensed matter systems. The first results of tests made with prototype VLAD detectors are presented, confirming the usefulness of the RD for measurements at scattering angles as low as 2-5 deg

Analysis of the 235U neutron cross sections in the resolved resonance range

International Nuclear Information System (INIS)

Leal, L.C.; de Saussure, G.; Perez, R.B.

1989-01-01

Using recent high-resolution measurements of the neutron transmission of 235 U and the spin-separated fission cross-section data of Moore et al., a multilevel analysis of the 235 U neutron cross sections was performed up to 300 eV. The Dyson Metha Δ 3 statistics were used to help locate small levels above 100 eV where resonances are not clearly resolved even in the best resolution measurements available. The statistical properties of the resonance parameters are discussed

Quantum recurrence and integer ratios in neutron resonances

Energy Technology Data Exchange (ETDEWEB)

Ohkubo, Makio

1998-03-01

Quantum recurrence of the compound nucleus in neutron resonance reactions are described for normal modes which are excited on the compound nucleus simultaneously. In the structure of the recurrence time, integer relations among dominant level spacings are derived. The `base modes` are assumed as stable combinations of the normal modes, preferably excited in many nuclei. (author)

Analysis of the 235U neutron cross sections in the resolved resonance range

International Nuclear Information System (INIS)

Leal, L.C.; de Saussure, G.; Perez, R.B.

1989-01-01

Using recent high-resolution measurements of the neutron transmission of 235 U and the spin-separated fission cross-section data of Moore et al., a multilevel analysis of the 235 U neutron cross sections was performed up to 300 eV. The Dyson Metha Δ 3 statistics were used to help locate small levels above 100 eV where resonances are not clearly resolved even in the best resolution measurements available. The statistical properties of the resonance parameters are discussed. 13 refs., 8 figs., 1 tab

Enhancing neutron beam production with a convoluted moderator

Energy Technology Data Exchange (ETDEWEB)

Iverson, E.B., E-mail: iversoneb@ornl.gov [Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Baxter, D.V. [Center for the Exploration of Energy and Matter, Indiana University, Bloomington, IN 47408 (United States); Muhrer, G. [Lujan Neutron Scattering Center, Los Alamos National Laboratory, P.O. Box 1663, Los Alamos, NM 87545 (United States); Ansell, S.; Dalgliesh, R. [ISIS Facility, Rutherford Appleton Laboratory, Chilton (United Kingdom); Gallmeier, F.X. [Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Kaiser, H. [Center for the Exploration of Energy and Matter, Indiana University, Bloomington, IN 47408 (United States); Lu, W. [Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States)

2014-10-21

We describe a new concept for a neutron moderating assembly resulting in the more efficient production of slow neutron beams. The Convoluted Moderator, a heterogeneous stack of interleaved moderating material and nearly transparent single-crystal spacers, is a directionally enhanced neutron beam source, improving beam emission over an angular range comparable to the range accepted by neutron beam lines and guides. We have demonstrated gains of 50% in slow neutron intensity for a given fast neutron production rate while simultaneously reducing the wavelength-dependent emission time dispersion by 25%, both coming from a geometric effect in which the neutron beam lines view a large surface area of moderating material in a relatively small volume. Additionally, we have confirmed a Bragg-enhancement effect arising from coherent scattering within the single-crystal spacers. We have not observed hypothesized refractive effects leading to additional gains at long wavelength. In addition to confirmation of the validity of the Convoluted Moderator concept, our measurements provide a series of benchmark experiments suitable for developing simulation and analysis techniques for practical optimization and eventual implementation at slow neutron source facilities.

Impact of neutron resonance treatments on reactor calculation

International Nuclear Information System (INIS)

Leszczynski, F.

1988-01-01

The neutron resonance treatment on reactor calculation is one of the not completely resolved problems of reactor theory. The calculation required on design, fuel management and accident analysis of nuclear reactors contains adjust coefficients and semi-empirical values introduced on the computer codes; these values are obtained comparing calculation results with experimental values and more exact calculation results. This is made when the characteristics of the analyzed system are such that this type of comparisons are possible. The impact that one fixed resonance treatment method have on the final evaluation of physics reactor parameters, reactivity, power distribution, etc., is useful to know. In this work, the differences between calculated parameters with two different methods of resonance treatment in cell calculations are shown. It is concluded that improvements on resonance treatment are necessary for growing the reliability on core calculations results. Finally, possible improvements, easy to implement in current computer codes, are presented. (Author) [es

Neutron production enhancements for the Intense Pulsed Neutron Source.

Energy Technology Data Exchange (ETDEWEB)

Iverson, E. B.

1999-01-04

The Intense Pulsed Neutron Source (IPNS) was the first high energy spallation neutron source in the US dedicated to materials research. It has operated for sixteen years, and in that time has had a very prolific record concerning the development of new target and moderator systems for pulsed spallation sources. IPNS supports a very productive user program on its thirteen instruments, which are oversubscribed by more than two times, meanwhile having an excellent overall reliability of 95%. Although the proton beam power is relatively low at 7 kW, the target and moderator systems are very efficient. The typical beam power which gives an equivalent flux for long-wavelength neutrons is about 60 kW, due to the use of a uranium target and liquid and solid methane moderators, precluded at some sources due to a higher accelerator power. The development of new target and moderator systems is by no means stagnant at IPNS. They are presently considering numerous enhancements to the target and moderators that offer prospects for increasing the useful neutron production by substantial factors. Many of these enhancements could be combined, although their combined benefit has not yet been well established. Meanwhile, IPNS is embarking on a coherent program of study concerning these improvements and their possible combination and implementation. Moreover, any improvements accomplished at IPNS would immediately increase the performance of IPNS instruments.

Neutron production enhancements for the Intense Pulsed Neutron Source

International Nuclear Information System (INIS)

Iverson, E. B.

1999-01-01

The Intense Pulsed Neutron Source (IPNS) was the first high energy spallation neutron source in the US dedicated to materials research. It has operated for sixteen years, and in that time has had a very prolific record concerning the development of new target and moderator systems for pulsed spallation sources. IPNS supports a very productive user program on its thirteen instruments, which are oversubscribed by more than two times, meanwhile having an excellent overall reliability of 95%. Although the proton beam power is relatively low at 7 kW, the target and moderator systems are very efficient. The typical beam power which gives an equivalent flux for long-wavelength neutrons is about 60 kW, due to the use of a uranium target and liquid and solid methane moderators, precluded at some sources due to a higher accelerator power. The development of new target and moderator systems is by no means stagnant at IPNS. They are presently considering numerous enhancements to the target and moderators that offer prospects for increasing the useful neutron production by substantial factors. Many of these enhancements could be combined, although their combined benefit has not yet been well established. Meanwhile, IPNS is embarking on a coherent program of study concerning these improvements and their possible combination and implementation. Moreover, any improvements accomplished at IPNS would immediately increase the performance of IPNS instruments

Experimental study of neutron-optical potential with absorption using Fabry-Perot magnetic resonator

International Nuclear Information System (INIS)

Hino, M.; Tasaki, S.; Ebisawa, T.; Kawai, T.; Achiwa, N.; Yamazaki, D.

1999-01-01

Complete text of publication follows. Recently spin precession angles of neutrons tunneling and non-tunneling through [Permalloy45(PA)-germanium(Ge)]-PA Fabry-Perot magnetic resonator have been observed [1]. The spin precession angle is well reproduced by the theoretical phase difference of up and down spin neutron wave function based on one-dimensional Schroedinger equation using optical potential model [2]. Spin precession angle and transmission probability of neutron through PA-(Ge/Gd)-PA Fabry-Perot magnetic resonator are presented, where the gap(Ge/Gd) layer consists of germanium and gadolinium atoms, and the optical potential model for magnetic multilayer system with absorption is discussed. (author) [1] M. Hino, et al., Physica B 241-243, 1083 (1998).; [2] S. Yamada, et al., Annu. Rep. Res. Reactor Inst. Kyoto Univ. 11, 8 (1978)

Fusion enhancement in the reactions of neutron-rich nuclei

International Nuclear Information System (INIS)

Bian Baoan; Zhang Fengshou; Zhou Hongyu

2009-01-01

The neutron-rich fusion reactions are investigated systematically using the improved isospin dependent quantum molecular dynamics model. By studying the systematic dependence of fusion barrier on neuron excess, we find the enhancement of the fusion cross sections for neutron-rich nuclear reactions that give the lowered static Coulomb barriers. The calculated fusion cross sections agree quantitatively with the experimental data. We further discuss the mechanism of the fusion enhancement of the cross sections for neutron-rich nuclear reactions by analyzing the dynamical lowering of the Coulomb barrier that is attributed to the enhancement of the N/Z ratio at the neck region.

Resonance structure of 32S+n from measurements of neutron total and capture cross sections

International Nuclear Information System (INIS)

Halperin, J.; Johnson, C.H.; Winters, R.R.; Macklin, R.L.

1980-01-01

Neutron total and capture cross sections of 32 S have been measured up to 1100 keV neutron energy [E/sub exc/( 33 S) =9700 keV]. Spin and parity assignments have been made for 28 of the 64 resonances found in this region. Values of total radiation widths, reduced neutron widths, level spacings, and neutron strength functions have been evaluated for s/sub 1/2/, p/sub 1/2/, p/sub 3/2/, and d/sub 5/2/ levels. Single particle contributions using the valency model account for a significant portion of the total radiation width only for the p/sub 1/2/-wave resonances. A significant number of resonances can be identified with reported levels excited in 32 S(d,p) and 29 Si(α,n) reactions. A calculation of the Maxwellian average cross section appropriate to stellar interiors indicates an average capture cross section at 30 keV, sigma-bar approx. = 4.2(2) mb, a result that is relatively insensitive to the assumed stellar temperature. Direct (potential) capture and the s-wave resonance capture contributions to the thermal capture cross section do not fully account for the reported thermal cross section (530 +- 40 mb) and a bound state is invoked to account for the discrepancy

Sensitivity Analysis and Requirements for Temporally and Spatially Resolved Thermometry Using Neutron Resonance Spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Fernandez, Juan Carlos [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Barnes, Cris William [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Mocko, Michael Jeffrey [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Zavorka, Lukas [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2018-01-31

This report is intended to examine the use of neutron resonance spectroscopy (NRS) to make time- dependent and spatially-resolved temperature measurements of materials in extreme conditions. Specifically, the sensitivities of the temperature estimate on neutron-beam and diagnostic parameters is examined. Based on that examination, requirements are set on a pulsed neutron-source and diagnostics to make a meaningful measurement.

Measurement and resonance analysis of neutron transmissions through four samples of 238U

International Nuclear Information System (INIS)

Olsen, D.K.; de Saussure, G.; Perez, R.B.; Difilippo, F.C.; Ingle, R.W.

1977-01-01

Accurate total and partial cross sections for 238 U are important for nuclear reactor design. In the resolved resonance region, energies below 4.0 keV, these cross sections are described in terms of individual resonance parameters of which the neutron widths in the 1.5 to 4.0 keV region from various workers appear discrepant. In order to determine these widths, (0.880 to 100.0 keV) neutron transmissions through 0.076, 0.254, 1.080, and 3.620 cm thick enriched 238 U samples were measured, and (0.880 to 100.0 keV) range transmissions were analyzed

Compact extended model for doppler broadening of neutron absorption resonances in solids

International Nuclear Information System (INIS)

Villanueva, A. J; Granada, J.R

2009-01-01

We present a simplified compact model for calculating Doppler broadening of neutron absorption resonances in an incoherent Debye solid. Our model extends the effective temperature gas model to cover the whole range of energies and temperatures, and reduces the information of the dynamical system to a minimum content compatible with a much better accuracy of the calculation. This model is thus capable of replacing the existing algorithm in standard codes for resonance cross sections preparation aimed at neutron and reactor physics calculations. The model is applied to the 238 U 6.671 eV effective broadened cross section. We also show how this model can be used for thermometry in an improved fashion compared to the effective temperature gas model. Experimental data of the same resonance at low and high temperatures are also shown and the performances of each model are put to the test on this basis. [es

Enhanced NIF neutron activation diagnostics.

Science.gov (United States)

Yeamans, C B; Bleuel, D L; Bernstein, L A

2012-10-01

The NIF neutron activation diagnostic suite relies on removable activation samples, leading to operational inefficiencies and a fundamental lower limit on the half-life of the activated product that can be observed. A neutron diagnostic system measuring activation of permanently installed samples could remove these limitations and significantly enhance overall neutron diagnostic capabilities. The physics and engineering aspects of two proposed systems are considered: one measuring the (89)Zr/(89 m)Zr isomer ratio in the existing Zr activation medium and the other using potassium zirconate as the activation medium. Both proposed systems could improve the signal-to-noise ratio of the current system by at least a factor of 5 and would allow independent measurement of fusion core velocity and fuel areal density.

Low dimensional neutron moderators for enhanced source brightness

DEFF Research Database (Denmark)

Mezei, Ferenc; Zanini, Luca; Takibayev, Alan

2014-01-01

In a recent numerical optimization study we have found that liquid para-hydrogen coupled cold neutron moderators deliver 3–5 times higher cold neutron brightness at a spallation neutron source if they take the form of a flat, quasi 2-dimensional disc, in contrast to the conventional more voluminous...... for cold neutrons. This model leads to the conclusions that the optimal shape for high brightness para-hydrogen neutron moderators is the quasi 1-dimensional tube and these low dimensional moderators can also deliver much enhanced cold neutron brightness in fission reactor neutron sources, compared...... to the much more voluminous liquid D2 or H2 moderators currently used. Neutronic simulation calculations confirm both of these theoretical conclusions....

Resonance Raman Optical Activity and Surface Enhanced Resonance Raman Optical Activity analysis of Cytochrome C

DEFF Research Database (Denmark)

Johannessen, Christian; Abdali, Salim; White, Peter C.

2007-01-01

High quality Resonance Raman (RR) and resonance Raman Optical Activity (ROA) spectra of cytochrome c were obtained in order to perform full assignment of spectral features of the resonance ROA spectrum. The resonance ROA spectrum of cytochrome c revealed a distinct spectral signature pattern due...... to resonance enhanced skeletal porphyrin vibrations, more pronounced than any contribution from the protein back-bone. Combining the intrinsic resonance enhancement of cytochrome c with surface plasmon enhancement by colloidal silver particles, the Surface Enhanced Resonance Raman Scattering (SERRS) and Chiral...... Enhanced Raman Spectroscopy (ChERS) spectra of the protein were successfully obtained at very low concentration (as low as 1 µM). The assignment of spectral features was based on the information obtained from the RR and resonance ROA spectra. Excellent agreement between RR and SERRS spectra is reported...

Neutron components of isoscalar giant quadrupole resonance states in 58,60,62,64Ni

International Nuclear Information System (INIS)

Antalik, R.

1989-01-01

The neutron-proton matrix element ratios (η) for isoscalar giant quadrupole resonance states of even Ni isotopes are investigated within the framework of the shell model quasiparticle random-phase approximation. The dependence of η ratios on radial neutron and proton ground state density distribution differences (Δ np ) is found to be about 1.0-1.5 Δ np . The theoretical η ratios are 14-23% lower than the hydrodynamical limit. The agreement between theoretical and experimental η ratios is observed for 58 Ni and 60 Ni isotopes. The η ratios for 62 Ni and 64 Ni suggested by the resonance π ± inelastic scattering cannot be interpreted even including the radial variations of the neutron fields. 18 refs.; 3 tabs

Coherent enhancement of resonance-mediated multiphoton absorption

International Nuclear Information System (INIS)

Zhang, Shian; Zhang, Hui; Jia, Tianqing; Wang, Zugeng; Sun, Zhenrong

2010-01-01

In this paper, we theoretically investigate the coherent enhancement of resonance-mediated (2+2) four-photon absorption. It is found that by shaping the spectral phase with a π phase step, the resonance-mediated (2+2) four-photon transition probability can be enhanced. Furthermore, the coherent enhancement dependences on the detuning between the two two-photon absorptions, laser spectral bandwidth and laser centre frequency are explicitly discussed and analysed. We believe these theoretical results may play an important role in enhancing more complex resonance-mediated multiphoton absorption processes.

Resonance self-shielding methodology of new neutron transport code STREAM

International Nuclear Information System (INIS)

Choi, Sooyoung; Lee, Hyunsuk; Lee, Deokjung; Hong, Ser Gi

2015-01-01

This paper reports on the development and verification of three new resonance self-shielding methods. The verifications were performed using the new neutron transport code, STREAM. The new methodologies encompass the extension of energy range for resonance treatment, the development of optimum rational approximation, and the application of resonance treatment to isotopes in the cladding region. (1) The extended resonance energy range treatment has been developed to treat the resonances below 4 eV of three resonance isotopes and shows significant improvements in the accuracy of effective cross sections (XSs) in that energy range. (2) The optimum rational approximation can eliminate the geometric limitations of the conventional approach of equivalence theory and can also improve the accuracy of fuel escape probability. (3) The cladding resonance treatment method makes it possible to treat resonances in cladding material which have not been treated explicitly in the conventional methods. These three new methods have been implemented in the new lattice physics code STREAM and the improvement in the accuracy of effective XSs is demonstrated through detailed verification calculations. (author)

Modeling the neutron spin-flip process in a time-of-flight spin-resonance energy filter

CERN Document Server

Parizzi, A A; Klose, F

2002-01-01

A computer program for modeling the neutron spin-flip process in a novel time-of-flight (TOF) spin-resonance energy filter has been developed. The software allows studying the applicability of the device in various areas of spallation neutron scattering instrumentation, for example as a dynamic TOF monochromator. The program uses a quantum-mechanical approach to calculate the local spin-dependent spectra and is essential for optimizing the magnetic field profiles along the resonator axis. (orig.)

Test of parity and time reversal invariance with low energy polarized neutrons

International Nuclear Information System (INIS)

Masaike, Akira

1996-01-01

Measurements of helicity asymmetries in slow neutron reactions on nuclei have been performed by transmission and capture γ-ray detection. Large enhancements of parity-violation effects have been observed on p-wave resonances of various medium and heavy nuclei. The weak matrix elements in hadron reactions have been deduced from these experimental results. Neutron spin precession near the p-wave resonance has been measured. In recent years violation of time reversal invariance is being searched for in the neutron reactions in which large enhancements of the parity violation effects have been observed. The measurement of the term σ n ·(k n x I) in a neutron reaction using polarized neutrons and a polarized target is an example of the test of T-violation. Polarizations of the neutron and lanthanum nucleus for these experiments are also presented. (author)

Density of Resonance Neutrons in Hydrogenous Media Near the Source

Energy Technology Data Exchange (ETDEWEB)

Broda, E.

1944-07-01

This report was written by D.V. Booker, E. Broda and L. Kowarski at the Cavendish Laboratory (Cambridge) in January 1944 and is about the density of resonance neutrons in hydrogenous media near the source. Neutron-absorbing properties of a medium sometimes cannot be studied by the usual density integration technique because the amount of medium, or the intensity far from the source is insufficient. In such cases many useful deductions can be made from single-point activation measurements in a medium of known behaviour provided the differences between the scattering properties of the two media are negligible, insofar as they influence the observed activations, or can be allowed for. The relevant properties of a hydrogenous medium are discussed in this report and the activation of resonance detectors in H{sub 3}BO{sub 3} is compared to the activation in C{sub 10}H{sub 8}, used as a reference medium. (nowak)

NRSC, Neutron Resonance Spectrum Calculation System

International Nuclear Information System (INIS)

Leszczynski, Francisco

2004-01-01

1 - Description of program or function: The NRSC system is a package of four programs for calculating detailed neutron spectra and related quantities, for homogeneous mixtures of isotopes and cylindrical reactor pin cells, in the energy resonance region, using ENDF/B evaluated nuclear data pre-processed with NJOY or Cullen's codes up to the Doppler Broadening and unresolved resonance level. 2 - Methods: NRSC consists of four programs: GEXSCO, RMET21, ALAMBDA and WLUTIL. GEXSCO prepares the nuclear data from ENDF/B evaluated nuclear data pre-processed with NJOY or Cullen's codes up to the Doppler Broadening or unresolved resonance level for RMET21 input. RMET21 calculates spectra and related quantities for homogeneous mixtures of isotopes and cylindrical reactor pin cells, in the energy resonance region, using slowing-down algorithms and, in the case of pin cells, the collision probability method. ALAMBDA obtains lambda factors (Goldstein-Cohen intermediate resonance factors in the formalism of WIMSD code) of different isotopes for including on WIMSD-type multigroup libraries for WIMSD or other cell-codes, from output of RMET21 program. WLUTIL is an auxiliary program for extracting tabulated parameters related with RMET21 program calculations from WIMSD libraries for comparisons, and for producing new WIMSD libraries with parameters calculated with RMET21 and ALAMBDA programs. 3 - Restrictions on the complexity of the problem: GEXSCO program has fixed array dimensions that are suitable for processing all reasonable outputs from nuclear data pre-processing programs. RMET21 program uses variable dimension method from a fixed general array. ALAMBDA and WLUTIL programs have fixed arrays that are adapted to standard WIMSD libraries. All programs can be easily modified to adapt to special requirements

Non-destructive bulk analysis of the Buggenum sword by neutron resonance capture analysis and neutron diffraction

International Nuclear Information System (INIS)

Postma, H.; Clarijs, M.; Borella, A.; Schillebeeckx, P.; Kamermans, H.

2010-01-01

Two neutron based techniques, neutron resonance capture analysis (NRCA) and time-of-flight neutron-diffraction (TOF-ND) have been used to determine the elemental composition and structure of a precious and very well preserved all-metal sword from the Bronze Age. This Buggenum sword was on loan from the National Museum of Antiquities (NMA) in Leiden (NL). NRCA and TOF-ND experiments have been carried out at a number of more or less identical positions of the sword. The tin-bronze ratio and the relative amounts of some minor elements (Sb, As, Ag, In) have been determined. The results of neutron diffraction measurements showed considerable tin-segregation, and clear indications of hardening on the edges of the blade. In addition, radiographs using Bremsstrahlung revealed the construction of the hilt-blade connection. The work was carried out at the EC Joint Research Centre IRMM in Geel (B) and at the ISIS facility of the Rutherford Appleton Laboratory (UK). (author)

Image enhancement using MCNP5 code and MATLAB in neutron radiography

International Nuclear Information System (INIS)

Tharwat, Montaser; Mohamed, Nader; Mongy, T.

2014-01-01

This work presents a method that can be used to enhance the neutron radiography (NR) image for objects with high scattering materials like hydrogen, carbon and other light materials. This method used Monte Carlo code, MCNP5, to simulate the NR process and get the flux distribution for each pixel of the image and determines the scattered neutron distribution that caused image blur, and then uses MATLAB to subtract this scattered neutron distribution from the initial image to improve its quality. This work was performed before the commissioning of digital NR system in Jan. 2013. The MATLAB enhancement method is quite a good technique in the case of static based film neutron radiography, while in neutron imaging (NI) technique, image enhancement and quantitative measurement were efficient by using ImageJ software. The enhanced image quality and quantitative measurements were presented in this work. - Highlights: • This work is applicable for static based film neutron radiography and digital neutron imaging. • MATLAB is a useful tool for imaging enhancement in radiographic film. • Advanced imaging processing is available in the ETRR-2 for imaging processing and data extraction. • The digital imaging system is suitable for complex shapes and sizes, while MATLAB technique is suitable for simple shapes and sizes. • Quantitative measurements are available

Status of neutron cross sections of transactinium isotopes in the resonance region - linear accelerator measurements

International Nuclear Information System (INIS)

James, G.D.

1976-01-01

A review of the status of transactinium isotope cross sections in the resonance region and of resolved resonance parameters is given by summarising the work submitted by fourteen contributors and also by highlighting other work where notable progress has been made in our knowledge of neutron resonance phenomena. (author)

Multilevel resonance analysis of sup 59 Co neutron transmission measurements

Energy Technology Data Exchange (ETDEWEB)

De Saussure, G.; Larson, N.M.; Harvey, J.A.; Hill, N.W. (Oak Ridge National Lab., TN (United States))

1992-07-01

Large discrepancies exist between the recent high-resolution neutron transmission data of {sup 59}Co measured at the Oak Ridge Electron Linear Accelerator (ORELA) and transmissions computed from the resolved resonance parameters of the nuclear data collection ENDF/B-VI. In order to provide new resonance parameters consistent with these data, the transmission measurements have been analyzed with the computer code SAMMY in the energy range 200 eV to 100 keV. The resonance parameters reported in this paper provide an accurate total cross section from 10{sup -5} eV to 100 keV and correctly reproduce the thermal capture cross section. Thermal cross-section values and related quantities are also reviewed here. (author).

Measurement of thermal neutron cross-section and resonance integral for the 165Ho(n,γ) 166gHo reaction using electron linac-based neutron source

Science.gov (United States)

Nguyen, Van Do; Pham, Duc Khue; Kim, Tien Thanh; Kim, Guinyun; Lee, Manwoo; Kim, Kyung Sook; Kang, Heung-Sik; Cho, Moo-Hyun; Ko, In Soo; Namkung, Won

2011-01-01

The thermal neutron cross-section and the resonance integral of the 165Ho(n,γ) 166gHo reaction have been measured by the activation method using a 197Au(n,γ) 198Au monitor reaction as a single comparator. The high-purity natural Ho and Au foils with and without a cadmium shield case of 0.5 mm thickness were irradiated in a neutron field of the Pohang neutron facility. The induced activities in the activated foils were measured with a calibrated p-type high-purity Ge detector. The correction factors for the γ-ray attenuation ( Fg), the thermal neutron self-shielding ( Gth), the resonance neutron self-shielding ( Gepi) effects, and the epithermal neutron spectrum shape factor ( α) were taken into account. The thermal neutron cross-section for the 165Ho(n,γ) 166gHo reaction has been determined to be 59.7 ± 2.5 barn, relative to the reference value of 98.65 ± 0.09 barn for the 197Au(n,γ) 198Au reaction. By assuming the cadmium cut-off energy of 0.55 eV, the resonance integral for the 165Ho(n,γ) 166gHo reaction is 671 ± 47 barn, which is determined relative to the reference value of 1550 ± 28 barn for the 197Au(n,γ) 198Au reaction. The present results are, in general, good agreement with most of the previously reported data within uncertainty limits.

A comparison of neutron resonance absorption in thermal reactor lattices in the AUS neutronics code system with Monte Carlo calculations

International Nuclear Information System (INIS)

Robinson, G.S.

1985-08-01

The calculation of resonance shielding by the subgroup method, as incorporated in the MIRANDA module of the AUS neutronics code system, is compared with Monte Carlo calculatons for a number of thermal reactor lattices. For the large range of single rod and rod cluster lattices considered, AUS results for resonance absorption were high by up to two per cent

Using the Δ3 statistic to test for missed levels in mixed sequence neutron resonance data

International Nuclear Information System (INIS)

Mulhall, Declan

2009-01-01

The Δ 3 (L) statistic is studied as a tool to detect missing levels in the neutron resonance data where two sequences are present. These systems are problematic because there is no level repulsion, and the resonances can be too close to resolve. Δ 3 (L) is a measure of the fluctuations in the number of levels in an interval of length L on the energy axis. The method used is tested on ensembles of mixed Gaussian orthogonal ensemble spectra, with a known fraction of levels (x%) randomly depleted, and can accurately return x. The accuracy of the method as a function of spectrum size is established. The method is used on neutron resonance data for 11 isotopes with either s-wave neutrons on odd-A isotopes, or p-wave neutrons on even-A isotopes. The method compares favorably with a maximum likelihood method applied to the level spacing distribution. Nuclear data ensembles were made from 20 isotopes in total, and their Δ 3 (L) statistics are discussed in the context of random matrix theory.

Results from the TARC experiment: spallation neutron phenomenology in lead and neutron-driven nuclear transmutation by adiabatic resonance crossing.

CERN Document Server

Abánades, A; Andriamonje, Samuel A; Angelopoulos, Angelos; Apostolakis, Alcibiades J; Arnould, H; Belle, E; Bompas, C A; Brozzi, Delecurgo; Bueno, J; Buono, S; Carminati, F; Casagrande, Federico; Cennini, P; Collar, J I; Cerro, E; Del Moral, R; Díez, S; Dumps, Ludwig; Eleftheriadis, C; Embid, M; Fernández, R; Gálvez, J; García, J; Gelès, C; Giorni, A; González, E; González, O; Goulas, I; Heuer, R D; Hussonnois, M; Kadi, Y; Karaiskos, P; Kitis, G; Klapisch, Robert; Kokkas, P; Lacoste, V; Le Naour, C; Lèpez, C; Loiseaux, J M; Martínez-Val, J M; Méplan, O; Nifenecker, H; Oropesa, J; Papadopoulos, I M; Pavlopoulos, P; Pérez-Enciso, E; Pérez-Navarro, A; Perlado, M; Placci, A; Poza, M; Revol, Jean Pierre Charles; Rubbia, Carlo; Rubio, J A; Sakelliou, L; Saldaña, F; Savvidis, E; Schussler, F; Sirvent, C; Tamarit, J; Trubert, D; Tzima, A; Viano, J B; Vieira, S L; Vlachoudis, V; Zioutas, Konstantin; CERN. Geneva. SPS and LEP Division

2000-01-01

The results of the TARC experiment are summarized herewith, whose main purpose is to demonstrate the possibility of using Adiabatic Resonance Crossing (ARC) to destroy efficiently Long-Lived Fission Fragments (LLFFs) in accelerator-driven systems and to validate a new simulation developed in the framework of the Energy Amplifier programme. An experimental set-up was installed in a CERN PS proton beam line to study how neutrons, produced by spallation at relatively high energy (En * 1 MeV), slow down quasi adiabatically, with almost flat isolethargic energy distribution and reach the capture resonance energy of an element to be transmuted where they will have a high probability of being captured. Precision measurements of energy and space distributions of spallation neutrons (using 2.5 GeV/c and 3.5 GeV/c protons) slowing down in a 3.3 m x 3.3 m x 3 m lead volume and of neutron capture rates on LLFFs 99Tc, 129I, and several other elements were performed. An appropriate formalism and appropriate computational t...

Image enhancement using MCNP5 code and MATLAB in neutron radiography.

Science.gov (United States)

Tharwat, Montaser; Mohamed, Nader; Mongy, T

2014-07-01

This work presents a method that can be used to enhance the neutron radiography (NR) image for objects with high scattering materials like hydrogen, carbon and other light materials. This method used Monte Carlo code, MCNP5, to simulate the NR process and get the flux distribution for each pixel of the image and determines the scattered neutron distribution that caused image blur, and then uses MATLAB to subtract this scattered neutron distribution from the initial image to improve its quality. This work was performed before the commissioning of digital NR system in Jan. 2013. The MATLAB enhancement method is quite a good technique in the case of static based film neutron radiography, while in neutron imaging (NI) technique, image enhancement and quantitative measurement were efficient by using ImageJ software. The enhanced image quality and quantitative measurements were presented in this work. Copyright © 2014 Elsevier Ltd. All rights reserved.

Contribution to analytical theory of neutron resonance absorption in heterogeneous reactor systems with cylindrical geometry

International Nuclear Information System (INIS)

Slipicevic, K.

1968-12-01

Following a review of the existing theories od resonance absorption this thesis includes a new approach for calculating the effective resonance integral of absorbed neutrons, new approximate formula for the penetration factor, an analysis of the effective resonance integral and the correction of the resonance integral taking into account the interference of potential and resonance dissipation. A separate chapter is devoted to calculation of the effective resonance integral for the regular reactor lattice with cylindrical fuel elements

Non-destructive assay of 242Pu by resonance neutron capture

International Nuclear Information System (INIS)

Kane, W.R.; Lu, Ming-Shih; Aronson, A.; Forman, L.; Vanier, P.E.

1995-01-01

For the accurate assay of plutonium by neutron correlation measurements, especially for material derived from high-burnup reactor fuel, the content of 242 Pu in a sample must be determined. Since 242 Pu has a long half-life (387,000 yr) and decays to 238 U by alpha particle emission with the accompanying emission of only weak, low-energy gamma rays, gamma-ray spectrometry methods which are ordinarily employed to determine the isotopic composition of a plutonium sample are not feasible for 242 Pu. The existence of a resonance in the neutron capture cross section of 242 Pu at an energy of 2.67 electron volts (eV) with a large (72, 000 barn) cross section affords the possibility for the quantitative assay of this isotope by epithermal neutron capture. Essential for this purpose is an appropriately designed geometry of neutron moderators and absorbers which will provide maximum flux in the eV region while suppressing thermal neutron capture by the fissile plutonium isotopes. Signatures for neutron capture in 242 Pu include the decay of 243 Pu (4.9 hr), prompt capture gamma rays (total energy 5.034 MeV), and the decay of an isomeric state (330 nanosecond). Experiments to determine the feasibility of this approach are currently in progress

Contribution to the study of the unresolved resonance range of the neutrons cross sections

International Nuclear Information System (INIS)

Noguere, Gilles

2014-01-01

This document presents the statistical description of neutron cross sections in the unresolved resonance range. The modeling of the total cross section and of the 'shape - elastic' cross section is based on the 'average R-Matrix' formalism. The partial cross sections describing the radiative capture, elastic scattering, inelastic scattering and fission process are calculated using the Hauser-Feshbach formalism with width fluctuation corrections. In the unresolved resonance range, these models depend on the average resonance parameters (neutron strength function Sc, mean level spacing D c , average partial reaction widths Γ c , channel radius a c , effective radius R' and distant level parameter R-bar c ∞ ). The codes (NJOY, CALENDF...) dedicated to the processing of nuclear data libraries (JEFF, ENDF/B, JENDL, CENDL, BROND... ) use the average parameters to take into account the self-shielding phenomenon for the simulation of the neutron transport in Monte-Carlo (MCNP, TRIPOLI... ) and deterministic (APOLLO, ERANOS...) codes. The evaluation work consists in establishing a consistent set of average parameters as a function of the total angular momentum J of the system and of the orbital moment of the incident neutron l. The work presented in this paper aims to describe the links between the S-Matrix and the 'average R-Matrix' formalism for the calculation of Sc, R-bar c ∞ , ac and R'. (author) [fr

Some Notes on Neutron Up-Scattering and the Doppler-Broadening of High-Z Scattering Resonances

Energy Technology Data Exchange (ETDEWEB)

Parsons, Donald Kent [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2017-09-28

When neutrons are scattered by target nuclei at elevated temperatures, it is entirely possible that the neutron will actually gain energy (i.e., up-scatter) from the interaction. This phenomenon is in addition to the more usual case of the neutron losing energy (i.e., down-scatter). Furthermore, the motion of the target nuclei can also cause extended neutron down-scattering, i.e., the neutrons can and do scatter to energies lower than predicted by the simple asymptotic models. In recent years, more attention has been given to temperature-dependent scattering cross sections for materials in neutron multiplying systems. This has led to the inclusion of neutron up-scatter in deterministic codes like Partisn and to free gas scattering models for material temperature effects in Monte Carlo codes like MCNP and cross section processing codes like NJOY. The free gas scattering models have the effect of Doppler Broadening the scattering cross section output spectra in energy and angle. The current state of Doppler-Broadening numerical techniques used at Los Alamos for scattering resonances will be reviewed, and suggestions will be made for further developments. The focus will be on the free gas scattering models currently in use and the development of new models to include high-Z resonance scattering effects. These models change the neutron up-scattering behavior.

Neutron Imaging Developments at LANSCE

Science.gov (United States)

Nelson, Ron; Hunter, James; Schirato, Richard; Vogel, Sven; Swift, Alicia; Ickes, Tim; Ward, Bill; Losko, Adrian; Tremsin, Anton

2015-10-01

Neutron imaging is complementary to x-ray imaging because of its sensitivity to light elements and greater penetration of high-Z materials. Energy-resolved neutron imaging can provide contrast enhancements for elements and isotopes due to the variations with energy in scattering cross sections due to nuclear resonances. These cross section differences exist due to compound nuclear resonances that are characteristic of each element and isotope, as well as broader resonances at higher energies. In addition, multi-probe imaging, such as combined photon and neutron imaging, is a powerful tool for discerning properties and features in materials that cannot be observed with a single probe. Recently, we have demonstrated neutron imaging, both radiography and computed tomography, using the moderated (Lujan Center) and high-energy (WNR facility) neutron sources at LANSCE. Flat panel x-ray detectors with suitable scintillator-converter screens provide good sensitivity for both low and high neutron energies. Micro-Channel-Plate detectors and iCCD scintillator camera systems that provide the fast time gating needed for energy-resolved imaging have been demonstrated as well. Examples of recent work will be shown including fluid flow in plants and imaging through dense thick objects. This work is funded by the US Department of Energy, National Nuclear Security Administration, and performed by Los Alamos National Security LLC under Contract DE-AC52-06NA25396.

Neutron cross section covariances in the resonance region: 52Cr, 56Fe, 58Ni

Energy Technology Data Exchange (ETDEWEB)

Oblozinsky, P.; Cho, Y.-S.; Mattoon, C.M.; Mughabghab, S.F.

2010-08-03

We evaluated covariances for neutron capture and elastic scattering cross sections on major structural materials, {sup 52}Cr, {sup 56}Fe and {sup 58}Ni, in the resonance region which extends beyond 800 keV for each of them. Use was made of the recently developed covariance formalism based on kernel approximation along with data in the Atlas of Neutron Resonances. The data of most interest for AFCI applications, elastic scattering cross section uncertainties at energies above about few hundred keV, are on the level of about 12% for {sup 52}Cr, 7-8% for {sup 56}Fe and 5-6% for {sup 58}Ni.

Testing T-odd, p-even interactions with gamma-rays from neutron p-wave resonances

International Nuclear Information System (INIS)

Barabanov, A.L.

1992-01-01

A new method for the study of time reversal violation is described. It consists of measurements of the forward-backward asymmetry in individual gamma-ray transitions resulting from unpolarized neutron capture in p-wave resonance. An experiment with a 113 Cd target performed at the Dubna pulsed neutron source has been analyzed and a limit on the time reversal odd, parity even interaction extracted. The possibilities of experiments using the powerful pulsed neutron source at Los Alamos are considered. 23 refs.; 2 figs

Investigation of the 232Th neutron cross-sections in resonance energy range

International Nuclear Information System (INIS)

Grigoriev, Yu.V.; Kitaev, V.Ya.; Sinitsa, V.V.; Zhuravlev, B.V.; Borzakov, S.B.; Faikov-Stanchik, H.; Ilchev, G.L.; Panteleev, Ts.Ts.; Kim, G.N.

2001-01-01

The alternative path in the development of atomic energy is the uranium-thorium cycle. In connection with this, the measurements of the 232 Th neutron capture and total cross-sections and its resonance self-shielding coefficients in resonance energy range are necessary because of their low accuracy. In this work, the results of the investigations of the thorium-232 neutron cross-sections are presented. The measurements have been carried out on the gamma-ray multisection liquid detector and neutron detector as a battery of boron counters on the 120 m flight path of the pulsed fast reactor IBR-30. As the filter samples were used the metallic disks of various thickness and diameter of 45 mm. Two plates from metallic thorium with thickness of 0.2 mm and with the square of 4.5x4.5 cm 2 were used as the radiator samples. The group neutron total and capture cross-sections within the accuracy of 2-7% in the energy range of (10 eV-10 keV) were obtained from the transmissions and the sum spectra of g-rays from the fourth multiplicity to the seventh one. The neutron capture group cross-sections of 238 U were used as the standard for obtaining of thorium ones. Analogous values were calculated on the GRUCON code with the ENDF/B-6, JENDL-3 evaluated data libraries. Within the limits of experimental errors an agreement between the experiment and calculation is observed, but in some groups the experimental values are larger than the calculated ones. (author)

Dipole resonances in light neutron-rich nuclei studied with time-dependent calculations of antisymmetrized molecular dynamics

International Nuclear Information System (INIS)

Kanada-En'yo, Y.; Kimura, M.

2005-01-01

To study isovector dipole responses of neutron-rich nuclei, we applied a time-dependent method of antisymmetrized molecular dynamics. The dipole resonances in Be, B, and C isotopes were investigated. In 10 Be, 15 B, and 16 C, collective modes of the vibration between a core and valence neutrons cause soft resonances at the excitation energy E x =10-15 MeV below the giant dipole resonance (GDR). In 16 C, we found that a remarkable peak at E x =14 MeV corresponds to the coherent motion of four valence neutrons against a 12 C core, whereas the GDR arises in the E x >20 MeV region because of vibration within the core. In 17 B and 18 C, the dipole strengths in the low-energy region decline compared with those in 15 B and 16 C. We also discuss the energy-weighted sum rule for the E1 transitions

56Fe resonance parameters for neutron energies up to 850 keV

International Nuclear Information System (INIS)

Perey, C.M.; Perey, F.G.; Harvey, J.A.; Hill, N.W.; Larson, N.M.

1990-12-01

High-resolution neutron measurements for 56 Fe-enriched iron targets were made at the Oak Ridge Electron Linear Accelerator (ORELA) in transmission below 20 MeV and in differential elastic scattering below 5 MeV. Transmission measurements were also performed with a natural iron target below 160 keV. The transmission data were analyzed from 5 to 850 keV with the multilevel R-matrix code SAMMY which uses Bayes' theorem for the fitting process. This code provides energies and neutron widths of the resonances inside the 5- to 850-keV energy region, as well as possible parameterization for resonances external to the analyzed region to describe the smooth cross section from a few eV to 850 keV. The resulting set of resonance parameters yields the accepted values for the thermal total and capture cross sections. The differential elastic-scattering data at several scattering angles were compared to theoretical calculations from 40 to 850 keV using the R-matrix code RFUNC based on the Blatt-Biedenharn formalism. Various combinations of spin and parity were tried to predict cross sections for the well defined ell > 0 resonances; comparison of these predictions with the data allowed us to determine the most likely spin and parity assignments for these resonances. The results of a capture data analysis by Corvi et al. (COR84), from 2 to 350 keV, were combined with our results to obtain the radiation widths of the resonances below 350 keV observed in transmission, capture, and differential elastic-scattering experiments

Enhancement of thermal neutron attenuation of nano-B4C, -BN dispersed neutron shielding polymer nanocomposites

International Nuclear Information System (INIS)

Kim, Jaewoo; Lee, Byung-Chul; Uhm, Young Rang; Miller, William H.

2014-01-01

Highlights: • Preparation of B 4 C and BN nanopowders using a simple ball milling process. • Homogeneous dispersion and strong adhesion of nano-B 4 C and -BN with polymer matrix. • Enhancement of mechanical properties of the nanocomposites compared to their micro counterparts. • Enhancement of thermal neutron attenuation of the nanocomposites. - Abstract: Nano-sized boron carbide (B 4 C) and boron nitride (BN) powder were prepared using ball milling. Micro- and milled nano-powders were melt blended with high density polyethylene (HDPE) using a polymer mixer followed by hot pressing to fabricate sheet composites. The tensile and flexural strengths of HDPE nanocomposites were ∼20% higher than their micro counterparts, while those for latter decreased compared to neat HDPE. Thermal neutrons attenuation of the prepared HDPE nanocomposites was evaluated using a monochromatic ∼0.025 eV neutron beam. Thermal neutron attenuation of the HDPE nanocomposites was greatly enhanced compared to their micro counterparts at the same B-10 areal densities. Monte Carlo n-Particles (MCNP) simulations based on the lattice structure modeling also shows the similar filler size dependent thermal neutron absorption

Effects of pairing correlation on low-lying quasi-particle resonance in neutron drip-line nuclei

OpenAIRE

Kobayashi, Yoshihiko; Matsuo, Masayuki

2015-01-01

We discuss effects of pairing correlation on quasi-particle resonance. We analyze in detail how the width of low-lying quasi-particle resonance is governed by the pairing correlation in the neutron drip-line nuclei. We consider the 46Si + n system to discuss low-lying p wave quasi-particle resonance. Solving the Hartree-Fock-Bogoliubov equation in the coordinate space with scattering boundary condition, we calculate the phase shift, the elastic cross section, the resonance width and the reson...

Analysis of resonance oscillation of the neutron flow in a BWR-core

International Nuclear Information System (INIS)

Storm, J.

1987-09-01

This is a thesis which has been made within the institution of automatic control in Lund. Two programs, 'Blackie' and 'Test' have been written in Fortran. These two programs are to be used for the evaluation of ASEA-ATOMs resonance test in different nuclear reactors. In these tests the condition of the reactor becomes more and more unstable because the coolant flow decreases at the same time as the power gradually increases. This leads to resonance in the neutron flow. This flow is measured by detectors placed in different parts of the reactor core. 'Blackie' receives and stores the values sampled by the detectors. The same program also carries out a Fourier analysis. Amplitudes and phase angles from the different oscillations are calculated. These results are then used as inputs for 'Test'. 'Test' is a plotting program. It draws the reactor and plots arrows where the detectors are situated. The size and direction of the arrows are measurements of the amplitudes and phase angles of the neutron flow oscillations. From these arrow diagrams you can come to conclusions about the oscillations in the neutron flow and how the affect the reactor. (author)

Ultraviolet Resonant Raman Enhancements in the Detection of Explosives

Energy Technology Data Exchange (ETDEWEB)

Short Jr., Billy Joe [Naval Postgraduate School, Monterey, CA (United States)

2009-06-01

Raman-based spectroscopy is potentially militarily useful for standoff detection of high explosives. Normal (non-resonance) and resonance Raman spectroscopies are both light scattering techniques that use a laser to measure the vibrational spectrum of a sample. In resonance Raman, the laser is tuned to match the wavelength of a strong electronic absorbance in the molecule of interest, whereas, in normal Raman the laser is not tuned to any strong electronic absorbance bands. The selection of appropriate excitation wavelengths in resonance Raman can result in a dramatic increase in the Raman scattering efficiency of select band(s) associated with the electronic transition. Other than the excitation wavelength, however, resonance Raman is performed experimentally the same as normal Raman. In these studies, normal and resonance Raman spectral signatures of select solid high explosive (HE) samples and explosive precursors were collected at 785 nm, 244 nm and 229 nm. Solutions of PETN, TNT, and explosive precursors (DNT & PNT) in acetonitrile solvent as an internal Raman standard were quantitatively evaluated using ultraviolet resonance Raman (UVRR) microscopy and normal Raman spectroscopy as a function of power and select excitation wavelengths. Use of an internal standard allowed resonance enhancements to be estimated at 229 nm and 244 nm. Investigations demonstrated that UVRR provided ~2000-fold enhancement at 244 nm and ~800-fold improvement at 229 nm while PETN showed a maximum of ~25-fold at 244 nm and ~190-fold enhancement at 229 nm solely from resonance effects when compared to normal Raman measurements. In addition to the observed resonance enhancements, additional Raman signal enhancements are obtained with ultraviolet excitation (i.e., Raman scattering scales as !4 for measurements based on scattered photons). A model, based partly on the resonance Raman enhancement results for HE solutions, is presented for estimating Raman enhancements for solid HE samples.

Study of the influence of chemical binding on resonant absorption and scattering of neutrons; Etude de l'influence des liaisons chimiques sur l'absorption et la diffusion des neutrons aux energies de resonance

Energy Technology Data Exchange (ETDEWEB)

Naberejnev, D G [Aix-Marseille-1 Univ., 13 - Marseille (France)

1999-02-01

At present time the problem of taking into account of the crystalline binding in the heavy nuclei resonance range is not correctly treated in nuclear data processing codes. The present work deals separately with resonant absorption and scattering of neutrons. The influence of crystalline binding is considered for both types of reactions in the harmonic crystal frame work. The harmonic crystal model is applied to the study of resonant absorption cross sections to show the inconsistency of the free gas model widely in use in reactor neutronics. The errors due to the use of the latter were found to be non negligible. These errors should be corrected by introducing a more elaborated harmonic crystal model in codes for resonances analysis and on the nuclear data processing stage. Currently the influence of crystalline binding on transfer cross section in the resonance domain is taken into account in a naive manner using the model of the free nucleus at rest in the laboratory system. In this work I present a formalism (Uncoupled Phonon Approximation) which permits to consider in more detail the crystalline structure of the nuclear fuel. This formalism shows new features in comparison with the static model. (author)

Study of high-spin analog resonances near the N=50 neutron shell

International Nuclear Information System (INIS)

Gales, S.; El Hage, Y.; Schapira, J.P.; Fortier, S.; Laurent, H.; Maison, J.M.

1979-01-01

The 96 Zr( 3 He,d) 97 Nb and the 92 Mo( 3 He,d) 93 Tc reactions, investigated at, respectively 39.0 and 28.5 MeV incident energies, were used to selectively populate high-spin analog resonances in the 97 Nb and 93 Tc nuclei. Angular distributions were measured for the dsub(3/2), gsub(7/2) and hsub(11/2) analog states of the low-lying levels in 97 Zr. A DWBA analysis of the data for these unbound levels (using Gamov functions as form factors) was carried out and spectroscopic strengths extracted. The 96 Zr( 3 He,dp) and 92 Mo( 3 He,dp) reactions were performed, respectively, at 37.5 and 30 MeV incident energies. The angular distributions of the emitted protons were measured in coincidence using method II of Litherland and Ferguson with 0 0 detection of deuteron groups. Spins, population parameters and proton branching ratios to the ground state and excited states of the targets were determined from the analysis of the angular correlation data. The position of the neutron threshold as compared with the excitation energies of the analog states in 97 Nb and 93 Tc is found to be an important parameter in the extraction of the structure informations on core-excited components in the parent levels wave functions. Neutron particle-hole multiplets are observed for the first time in 96 Zr through the decay of the gsub(7 /2) and hsub(11/2) analog resonances. The limitation of the present method due to the neutron threshold or to the energy resolution in the proton channel is discussed and compared with the results of inelastic resonant scattering through isobaric analog resonances

Analysis of Current-mode Detectors For Resonance Detection In Neutron Optics Time Reversal Symmetry Experiment

Science.gov (United States)

Forbes, Grant; Noptrex Collaboration

2017-09-01

One of the most promising explanations for the observed matter-antimatter asymmetry in our universe is the search for new sources of time-reversal (T) symmetry violation. The current amount of violation seen in the kaon and B-meson systems is not sufficient to describe this asymmetry. The Neutron Optics Time Reversal Experiment Collaboration (NOPTREX) is a null test for T violation in polarized neutron transmission through a polarized 139La target. Due to the high neutron flux needed for this experiment, as well as the ability to effectively subtract background noise, a current-mode neutron detector that can resolve resonances at epithermal energies has been proposed. In order to ascertain if this detector design would meet the requirements for the eventual NOPTREX experiment, prototypical detectors were tested at the NOBORU beam at the Japan Proton Accelerator Research Complex (JPARC) facility. Resonances in In and Ta were measured and the collected data was analyzed. This presentation will describe the analysis process and the efficacy of the detectors will be discussed. Department of Energy under Contract DE-SC0008107, UGRAS Scholarship.

Synthetic model for Doppler broadening of neutron absorption resonances in molecular fluids

Energy Technology Data Exchange (ETDEWEB)

Villanueva, Alejandro J., E-mail: villanueva@cab.cnea.gov.a [Comision Nacional de Energia Atomica, Centro Atomico Bariloche and Instituto Balseiro, 8400 S.C. de Bariloche (RN) (Argentina); Consejo Nacional de Investigaciones Cientificas y Tecnicas (Argentina); Granada, J.R. [Comision Nacional de Energia Atomica, Centro Atomico Bariloche and Instituto Balseiro, 8400 S.C. de Bariloche (RN) (Argentina); Consejo Nacional de Investigaciones Cientificas y Tecnicas (Argentina)

2010-08-15

A general and systematic approach expressed in modern language, accounting for molecular motion effects on Doppler Broadening of Neutron Absorption Resonances (DBNAR) is given the form of a new model. It relies on well validated hypothesis: The separability of atomic from nuclear degrees of freedom, the use of the Van Hove scattering formalism and the fact that a conceptually identical approach produced experimentally proved predictions when applied to DBNAR in solid systems. We treat the molecular internal degrees of freedom approximately as harmonic oscillators. As a second contribution of this work, a synthetic model is presented in order to make the more complete model mentioned above suitable for neutron calculation codes. This second synthetic model reduces to the exact expressions of the complete model in the low and high neutron energy regimes and provides a plausible transition in between. Numerical results are presented for a general hypothetical case to show its strengths and limitations. Also, both models are applied to a real case of the {sup 238}U 6.674 eV resonant effective broadened absorption cross-section in UF6 (uranium hexafluoride). A direct experimental validation of our models is still necessary for which a special high resolution neutron transmission experiment ought to be devised at low temperatures and pressures on a gaseous system. It is showed how the synthetic model can be used to make thermometric predictions in an improved fashion in comparison to the effective temperature gas model at low temperatures.

Neutron capture in s-wave resonances of 56Fe, 58Ni, and 60Ni

International Nuclear Information System (INIS)

Wisshak, F.; Kaeppeler, F.; Reffo, G.; Fabbri, F.

1983-07-01

The neutron capture widths of s-wave resonances in 56 Fe (27.7 keV), 58 Ni(15.4 keV) and 60 Ni (12.5 keV) have been determined using a setup completely different from previous experiments. A pulsed 3-MV Van de Graaff accelerator and a kinematically collimated neutron beam, produced via the 7 Li (p,n) reaction, was used in the experiments. Capture gamma-rays were observed by three Moxon-Rae detectors with graphite-, bismuth-graphite-, and bismuth-converters, respectively. The samples were positioned at a neutron flight path of only 8 cm. Thus events due to capture of resonance scattered neutrons in the detectors or in surrounding materials are completely discriminated by their additional time of flight. The high neutron flux at the sample position allowed the use of very thin samples (0.15 mm-0.45 mm), avoiding large multiple scattering corrections. The data obtained with the individual detectors were corrected for the efficiency of the respective converter materials. For that purpose, detailed theoretical calculations of the capture gamma-ray spectra of the measured isotopes and of gold, which was used as a standard, were performed. The final results are: GAMMAsub(γ)(27.7 keV, 56 Fe) = 1.06 +- 0.05 eV, GAMMAsub(γ)(15.4 keV, 58 Ni) = 1.53 +- 0.10 eV and GAMMAsub(γ)(12.5 keV, 60 Ni) = 2.92 +- 0.19 eV. The accuracy obtained with the present experimental method represents an improvement of a factor 3-6 compared to previous experiments. The investigated s-wave resonances contribute 10-40% to the total capture rate of the respective isotopes in a typical fast reactor. (orig.) [de

Electron spin resonance in neutron-irradiated graphite. Dependence on temperature and effect of annealing; Resonance paramagnetique du graphite irradie aux neutrons. Variation en fonction de la temperature et experiences de recuit

Energy Technology Data Exchange (ETDEWEB)

Kester, T [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires, Laboratoire de resonance magnetique

1967-09-01

The temperature dependence of the electron spin resonance signal from neutron irradiated graphite has been studied. The results lead to an interpretation of the nature of the paramagnetic centers created by irradiation. In annealing experiments on graphite samples, which had been irradiated at low temperature, two annealing peaks and one anti-annealing peak were found. Interpretations are proposed for these peaks. (author) [French] Le graphite irradie aux neutrons a ete etudie par resonance paramagnetique electronique en fonction de la temperature. La nature des centres paramagnetiques crees par irradiation est interpretee a l'aide des resultats. Des experiences de recuit sur des echantillons de graphite irradie a 77 deg. K ont permis de mettre en evidence deux pics de recuit et un pic d'anti-recuit, pour lesquels des interpretations sont proposees. (auteur)

Neutron Cross section Covariances in the Resonance region: 50,53Cr, 54,57Fe and 60Ni

Energy Technology Data Exchange (ETDEWEB)

Oblozinsky, P.; Cho,Y.-S.; Mattoon,C.M.; Mughabghab,S.F.

2010-11-23

We evaluated covariances in the neutron resonance region for capture and elastic scattering cross sections on minor structural materials, {sup 50,53}Cr, {sup 54,57}Fe and {sup 60}Ni. Use was made of the recently developed covariance formalism based on kernel approximation along with data in the Atlas of Neutron Resonances. Our results of most interest for advanced fuel cycle applications, elastic scattering cross section uncertainties at energies around 100 keV, are on the level of about 7-10%.

Thermal neutron cross sections and resonance integrals for the 1994 handbook of chemistry and physics

International Nuclear Information System (INIS)

Holden, N.E.

1994-01-01

A re-evaluation of all thermal neutron cross sections and neutron resonance integrals has been performed, utilizing the previous database of the ''Barn Book'' and all of the more recently published experiments. Only significant changes or previously undetermined values are recorded in this report. The source for each value is also recorded in the accompanying table

Enhancement of thermal neutron attenuation of nano-B{sub 4}C, -BN dispersed neutron shielding polymer nanocomposites

Energy Technology Data Exchange (ETDEWEB)

Kim, Jaewoo, E-mail: kimj@kaeri.re.kr [Nuclear Materials Research Division, Korea Atomic Energy Research Institute, 111-989 Daeduck-daero, Yuseong-gu, Daejeon-si 305-353 (Korea, Republic of); WCI Quantum Beam based Radiation Research Center, Korea Atomic Energy Research Institute, 111-989 Daeduck-daero, Yuseong-gu, Daejeon-si 305-353 (Korea, Republic of); Missouri University Research Reactor, University of Missouri-Columbia, Columbia, MO 65211 (United States); Lee, Byung-Chul [Nuclear Reactor Core Design Division, Korea Atomic Energy Research Institute, 111-989 Daeduck-daero, Yuseong-gu, Daejeon-si 305-353 (Korea, Republic of); Uhm, Young Rang [Radioisotopes Research Division, Korea Atomic Energy Research Institute, 111-989 Daeduck-daero, Yuseong-gu, Daejeon-si 305-353 (Korea, Republic of); Miller, William H. [Missouri University Research Reactor, University of Missouri-Columbia, Columbia, MO 65211 (United States)

2014-10-15

Highlights: • Preparation of B{sub 4}C and BN nanopowders using a simple ball milling process. • Homogeneous dispersion and strong adhesion of nano-B{sub 4}C and -BN with polymer matrix. • Enhancement of mechanical properties of the nanocomposites compared to their micro counterparts. • Enhancement of thermal neutron attenuation of the nanocomposites. - Abstract: Nano-sized boron carbide (B{sub 4}C) and boron nitride (BN) powder were prepared using ball milling. Micro- and milled nano-powders were melt blended with high density polyethylene (HDPE) using a polymer mixer followed by hot pressing to fabricate sheet composites. The tensile and flexural strengths of HDPE nanocomposites were ∼20% higher than their micro counterparts, while those for latter decreased compared to neat HDPE. Thermal neutrons attenuation of the prepared HDPE nanocomposites was evaluated using a monochromatic ∼0.025 eV neutron beam. Thermal neutron attenuation of the HDPE nanocomposites was greatly enhanced compared to their micro counterparts at the same B-10 areal densities. Monte Carlo n-Particles (MCNP) simulations based on the lattice structure modeling also shows the similar filler size dependent thermal neutron absorption.

Investigation of (3, 3) resonance effects on the properties of neutron ...

Indian Academy of Sciences (India)

Home; Journals; Pramana – Journal of Physics; Volume 76; Issue 4. Investigation of (3,3) resonance effects on the properties of neutron-rich double magic spherical finite nucleus, 132Sn, in the ground state and under compression. Mohammed H E Abu-Sei'leek. Volume 76 Issue 4 April 2011 pp 573-589 ...

Study of the influence of chemical binding on resonant absorption and scattering of neutrons; Etude de l'influence des liaisons chimiques sur l'absorption et la diffusion des neutrons aux energies de resonance

Energy Technology Data Exchange (ETDEWEB)

Naberejnev, D.G. [Aix-Marseille-1 Univ., 13 - Marseille (France)

1999-02-01

At present time the problem of taking into account of the crystalline binding in the heavy nuclei resonance range is not correctly treated in nuclear data processing codes. The present work deals separately with resonant absorption and scattering of neutrons. The influence of crystalline binding is considered for both types of reactions in the harmonic crystal frame work. The harmonic crystal model is applied to the study of resonant absorption cross sections to show the inconsistency of the free gas model widely in use in reactor neutronics. The errors due to the use of the latter were found to be non negligible. These errors should be corrected by introducing a more elaborated harmonic crystal model in codes for resonances analysis and on the nuclear data processing stage. Currently the influence of crystalline binding on transfer cross section in the resonance domain is taken into account in a naive manner using the model of the free nucleus at rest in the laboratory system. In this work I present a formalism (Uncoupled Phonon Approximation) which permits to consider in more detail the crystalline structure of the nuclear fuel. This formalism shows new features in comparison with the static model. (author)

Basis for calculating cross sections for nuclear magnetic resonance spin-modulated polarized neutron scattering.

Science.gov (United States)

Kotlarchyk, Michael; Thurston, George M

2016-12-28

In this work we study the potential for utilizing the scattering of polarized neutrons from nuclei whose spin has been modulated using nuclear magnetic resonance (NMR). From first principles, we present an in-depth development of the differential scattering cross sections that would arise in such measurements from a hypothetical target system containing nuclei with non-zero spins. In particular, we investigate the modulation of the polarized scattering cross sections following the application of radio frequency pulses that impart initial transverse rotations to selected sets of spin-1/2 nuclei. The long-term aim is to provide a foundational treatment of the scattering cross section associated with enhancing scattering signals from selected nuclei using NMR techniques, thus employing minimal chemical or isotopic alterations, so as to advance the knowledge of macromolecular or liquid structure.

Resonant vibrations of self-interstitials in fcc metals with application to specific heat and neutron scattering

International Nuclear Information System (INIS)

Ram, P.N.; Dederichs, P.H.

1981-07-01

Some aspects of resonant vibrations of self-interstitials in the 100-dumbbell configuration in fcc-metals are discussed by extending previous calculations of Zeller et al. and Schober et al. Employing a simple defect model with nearest-neighbour interaction the local frequency spectrum of the defect is calculated showing several localized modes and low-frequency resonant modes. The change in the total density of states due to the defects is expressed as the derivative of a generalized phase shift which is used to calculate the change in the lattic specific heat due to single interstitials. Inelastic neutron scattering away from the one-phonon lines is proposed as a method to observe the resonant modes induced by self-interstitials. The model calculation in Cu shows that the well defined resonant modes due to dumbbell vibrations have appreciable intensity and could presumably be detected in neutron scattering measurements. The effect of di-interstitials on the phonon dispersion in Al is also discussed. (orig./GSCH)

n+235U resonance parameters and neutron multiplicities in the energy region below 100 eV

Directory of Open Access Journals (Sweden)

Pigni Marco T.

2017-01-01

Full Text Available In August 2016, following the recent effort within the Collaborative International Evaluated Library Organization (CIELO pilot project to improve the neutron cross sections of 235U, Oak Ridge National Laboratory (ORNL collaborated with the International Atomic Energy Agency (IAEA to release a resonance parameter evaluation. This evaluation restores the performance of the evaluated cross sections for the thermal- and above-thermal-solution benchmarks on the basis of newly evaluated thermal neutron constants (TNCs and thermal prompt fission neutron spectra (PFNS. Performed with support from the US Nuclear Criticality Safety Program (NCSP in an effort to provide the highest fidelity general purpose nuclear database for nuclear criticality applications, the resonance parameter evaluation was submitted as an ENDF-compatible file to be part of the next release of the ENDF/B-VIII.0 nuclear data library. The resonance parameter evaluation methodology used the Reich-Moore approximation of the R-matrix formalism implemented in the code SAMMY to fit the available time-of-flight (TOF measured data for the thermal induced cross section of n+235U up to 100 eV. While maintaining reasonably good agreement with the experimental data, the validation analysis focused on restoring the benchmark performance for 235U solutions by combining changes to the resonance parameters and to the prompt resonance v̅ below 100 eV.

Demonstration of Neutron Resonance capture applied to a Cultural Heritage study of Antique Benin Bronzes

International Nuclear Information System (INIS)

Blaauw, M.; Postma, H.; Mutti, P.

2001-01-01

In many cases of historical and archaeological studies physical techniques Instrumental Neutron Activation Analysis (INAA) X-Ray Fluorescence (XRF) and Proton Induced X-ray Emission (PIXE) are used to get information about the element composition of objects. INAA is usually carried out using small samples taken from the object . XRF and PIXE only yield surface information, and require cleaning of the surface to suppress the effect of external contamination. Such actions on artefacts are unwanted. Recently neutron capture resonances have been used to identify elements in artefacts using a set of γray detectors and a time-of flight system at the GELINA facility. This allows identification and quantification of elements of precious artefacts in an fully non-destructive way and with very little activation Because of the novelly of the method the principles of neutron resonance capture analysis (NRC A) will be discussed and the results of an applications to a comparative study of two Benin Bronzes presented

Resonance neutron capture in 23Na and 27Al from 3 to 600 keV

International Nuclear Information System (INIS)

Musgrove, A.R. de L.; Allen, B.J.; Macklin, R.L.

1978-01-01

The radiative capture cross sections of 23 Na and 27 Al were measured with the high resolution facility at the 40 m station of the Oak Ridge Electron Linear Accelerator. Resonance parameters for the individual resonances below 600 keV are given. Particular care was taken to correct the data for prompt neutron scattering effects by Monte Carlo methods

Neutron Transmission and Capture Measurements and Resonance Parameter Analysis of Neodymium from 1eV to 500 eV

International Nuclear Information System (INIS)

DP Barry; MJ Trbovich; Y Danon; RC Block; RE Slovacek

2005-01-01

Neodymium is a 235 U fission product and is important for reactor neutronic calculations. The aim of the present work is to improve upon the existing neutron cross section data of neodymium. Neutron capture and transmission measurements were performed by the time-off-light technique at the Rensselaer Polytechnic Institute LINAC laboratory using metallic neodymium samples. The capture measurements were made at the 25-m flight station with a 16-segment NaI multiplicity detector, and the transmission measurements were performed at 15-m and 25-m flight stations, respectively, with 6 Li glass scintillation detectors. After the data were collected and reduced, resonance parameters were determined by combined fitting of the transmission and capture data with the multilevel R-matrix Bayesian code SAMMY. The resonance parameters for all naturally occurring neodymium isotopes were deduced within the energy range of 1 eV to 500 eV. The resulting resonance parameters were used to calculate the capture resonance integrals from this energy. The RPI parameters gave a resonance integral value of 32 ± 1 barns that is approximately 7% lower than that obtained with the ENDF-B/VI parameters. The current measurements significantly reduce the uncertainties on the resonance parameters when compared with previously published parameters

Dependence of the Ratio between the Resonance Integral and Thermal Neutron Cross Section on the Deviation of the Epithermal Neutron Spectrum from the 1/E Law

International Nuclear Information System (INIS)

Soliman, N.F.

2012-01-01

In k 0 - Neutron Activation Analysis (k 0 -NAA), the conversion from the tabulated Q 0 (ratio of the resonance integral to thermal neutron cross-section)to Q 0 (α) (α is the shape factor of the epithermal neutron flux, indicating the deviation of the epithermal neutron spectrum from the ideal 1/E shape) are calculated using a FORTRAN program. The calculations are done for most elements that can be detected by neutron activation using different values of the parameter (α) ranging from -0.1≤α≤+0.1. The obtained data are used to study the dependence of the values (α) on the irradiation position factor in (k 0 -NAA)equation for some selected isotopes differ in their resonance energy and its Q 0 values. The results show that, the irradiation factor is affective mainly for low thermal tro epithermal flux ratio f especially for Q 0 value greater than 50. so consequently determining the irradiation parameters α value is not needed for irradiation positions that rich with thermal neutron. But for high f values the irradiation position factor should be taken into account. On the other hand the constructed FORTRAN program can be used to calculate the value Q 0 (α) directly for different value of α

Resonant production of $\\gamma$ rays in jolted cold neutron stars

CERN Document Server

Kusenko, A

1998-01-01

Acoustic shock waves passing through colliding cold neutron stars can cause repetitive superconducting phase transitions in which the proton condensate relaxes to its equilibrium value via coherent oscillations. As a result, a resonant non-thermal production of gamma rays in the MeV energy range with power up to 10^(52) erg/s can take place during the short period of time before the nuclear matter is heated by the shock waves.

Neutron Capture and Transmission Measurements and Resonance Parameter Analysis of Niobium

International Nuclear Information System (INIS)

NJ Drindak; JA Burke; G Leinweber; JA Helm; JG Hoole; RC Block; Y Danon; RE Slovacek; BE Moretti; CJ Werner; ME Overberg; SA Kolda; MJ Trbovich; DP Barry

2005-01-01

Epithermal neutron capture and transmission measurements were performed using the time-of-flight method at the RPI linac using metallic Nb samples. The capture measurements were made at the 25-meter flight station with a 16-section sodium iodide multiplicity detector and the transmission measurements at the 25-meter flight station with a Li-6 glass scintillation detector. Resonance parameters were determined for all resonances up to 500eV with a combined analysis of capture and transmission data using the multi-level R-matrix Bayesian code SAMMY. The present results are compared to those presented in ENDF/B-VI, updated through Release 3

Resonance amplification of oscillations between νμ and ντ

International Nuclear Information System (INIS)

Pal'gi, L.D.

1988-01-01

Resonance enhancement of ν μ ↔ ν τ in collasping nuclei is considered using distribution of density and neutron and proton ratio according to Imshennik and Madjozhin model. Under a strong neutronization degree the radiation corrections of Gα 2 order are suppressed and η μ and ν τ scattering amplitude difference is determined quite exactly. Condition for ν-bar μ ↔ ν-bar τ oscillation resonance strengthening is recorded. Though there are conditions for ν-bar μ ↔ ν-bar τ oscillation resonance amplification in collasping stars as ν-bar μ and ν-bar τ fluxes in them are equal, ν-bar μ ↔ ν-bar μ resonance strengthening does not lead to the effects o bserved

Contribution to analytical theory of neutron resonance absorption in heterogeneous reactor systems with cylindrical geometry; Prilog analitickoj teoriji rezonzntne apsorpcije neutron u heterogenom reaktorskim sistemima sa cilindricnom geometrijom

Energy Technology Data Exchange (ETDEWEB)

Slipicevic, K [Institute of Nuclear Sciences Boris Kidric, Vinca, Beograd (Yugoslavia)

1968-07-01

Following a review of the existing theories od resonance absorption this thesis includes a new approach for calculating the effective resonance integral of absorbed neutrons, new approximate formula for the penetration factor, an analysis of the effective resonance integral and the correction of the resonance integral taking into account the interference of potential and resonance dissipation. A separate chapter is devoted to calculation of the effective resonance integral for the regular reactor lattice with cylindrical fuel elements.

Demonstration of a single-crystal reflector-filter for enhancing slow neutron beams

DEFF Research Database (Denmark)

Muhrer, G.; Schonfeldt, T.; Iverson, E. B.

2016-01-01

The cold polycrystalline beryllium reflector-filter concept has been used to enhance the cold neutron emission of cryogenic hydrogen moderators, while suppressing the intermediate wavelength and fast neutron emission at the same time. While suppressing the fast neutron emission is often desired, ......-filter benefits arise from its interaction with fast (background) neutrons, not with intermediate wavelength neutrons of potential interest in many types of neutron scattering. (C) 2016 Elsevier B.V. All rights reserved....

Results from the TARC experiment: spallation neutron phenomenology in lead and neutron-driven nuclear transmutation by adiabatic resonance crossing

Science.gov (United States)

Abánades, A.; Aleixandre, J.; Andriamonje, S.; Angelopoulos, A.; Apostolakis, A.; Arnould, H.; Belle, E.; Bompas, C. A.; Brozzi, D.; Bueno, J.; Buono, S.; Carminati, F.; Casagrande, F.; Cennini, P.; Collar, J. I.; Cerro, E.; Del Moral, R.; Díez, S.; Dumps, L.; Eleftheriadis, C.; Embid, M.; Fernández, R.; Gálvez, J.; García, J.; Gelès, C.; Giorni, A.; González, E.; González, O.; Goulas, I.; Heuer, D.; Hussonnois, M.; Kadi, Y.; Karaiskos, P.; Kitis, G.; Klapisch, R.; Kokkas, P.; Lacoste, V.; Le Naour, C.; López, C.; Loiseaux, J. M.; Martínez-Val, J. M.; Méplan, O.; Nifenecker, H.; Oropesa, J.; Papadopoulos, I.; Pavlopoulos, P.; Pérez-Enciso, E.; Pérez-Navarro, A.; Perlado, M.; Placci, A.; Poza, M.; Revol, J.-P.; Rubbia, C.; Rubio, J. A.; Sakelliou, L.; Saldaña, F.; Savvidis, E.; Schussler, F.; Sirvent, C.; Tamarit, J.; Trubert, D.; Tzima, A.; Viano, J. B.; Vieira, S.; Vlachoudis, V.; Zioutas, K.

2002-02-01

We summarize here the results of the TARC experiment whose main purpose is to demonstrate the possibility of using Adiabatic Resonance Crossing (ARC) to destroy efficiently Long-Lived Fission Fragments (LLFFs) in accelerator-driven systems and to validate a new simulation developed in the framework of the Energy Amplifier programme. An experimental set-up was installed in a CERN PS proton beam line to study how neutrons produced by spallation at relatively high energy ( E n⩾1 MeV) slow down quasi-adiabatically with almost flat isolethargic energy distribution and reach the capture resonance energy of an element to be transmuted where they will have a high probability of being captured. Precision measurements of energy and space distributions of spallation neutrons (using 2.5 and 3.5 GeV/ c protons) slowing down in a 3.3 m×3.3 m×3 m lead volume and of neutron capture rates on LLFFs 99Tc, 129I, and several other elements were performed. An appropriate formalism and appropriate computational tools necessary for the analysis and understanding of the data were developed and validated in detail. Our direct experimental observation of ARC demonstrates the possibility to destroy, in a parasitic mode, outside the Energy Amplifier core, large amounts of 99Tc or 129I at a rate exceeding the production rate, thereby making it practical to reduce correspondingly the existing stockpile of LLFFs. In addition, TARC opens up new possibilities for radioactive isotope production as an alternative to nuclear reactors, in particular for medical applications, as well as new possibilities for neutron research and industrial applications.

Collinear Resonance Ionization Spectroscopy of Neutron-Deficient Francium Isotopes

CERN Document Server

Flanagan, K T; Ruiz, R F Garcia; Budincevic, I; Procter, T J; Fedosseev, V N; Lynch, K M; Cocolios, T E; Marsh, B A; Neyens, G; Strashnov, I; Stroke, H H; Rossel, R E; Heylen, H; Billowes, J; Rothe, S; Bissell, M L; Wendt, K D A; de Groote, R P; De Schepper, S

2013-01-01

The magnetic moments and isotope shifts of the neutron-deficient francium isotopes Fr202-205 were measured at ISOLDE-CERN with use of collinear resonance ionization spectroscopy. A production-to-detection efficiency of 1\\% was measured for Fr-202. The background from nonresonant and collisional ionization was maintained below one ion in 10(5) beam particles. Through a comparison of the measured charge radii with predictions from the spherical droplet model, it is concluded that the ground-state wave function remains spherical down to Fr-205, with a departure observed in Fr-203 (N = 116).

Review of Non-Neutron and Neutron Nuclear Data, 2004

International Nuclear Information System (INIS)

Holden, Norman E.

2005-01-01

Review articles are in preparation for the 2004 edition of the CRC Handbook of Chemistry and Physics dealing with the evaluation of both non-neutron and neutron nuclear data. Data on the discovery of element 110, Darmstadtium, and element 111 have been officially accepted, while data on element 118 have been withdrawn. Data to be presented include revised values for very short-lived nuclides, long-lived nuclides, and beta-beta decay measurements. There has been a reassessment of the spontaneous fission (sf) half-lives, which distinguishes between sf decay half-lives and cluster decay half-lives, and with cluster-fission decay. New measurements of isotopic abundance values for many elements will be discussed with an emphasis on the minor isotopes of interest for use in neutron activation analysis measurements. Neutron resonance integrals will be discussed emphasizing the differences between the calculated values obtained from the analytical integration over neutron resonances and the measured values in a neutron reactor-spectrum, which does not quite conform to the assumed 1/E neutron energy spectrum. The method used to determine the neutron resonance integral from measurement, using neutron activation analysis, will be discussed

Depolarisation effects in resonance absorption neutron polarising filters

International Nuclear Information System (INIS)

Mayers, J.

1982-06-01

The depolarisation of a neutron beam passing through a system of magnetically misaligned single domain particles is examined and simulated using a Monte-Carlo programme. The results of the simulations are in excellent agreement with those of analytic calculations within the regimes where such calculations are applicable. The simulations have been used in the estimation of the polarising efficiency and transmittance of a resonance absorption filter containing partially aligned particles of SmCo 5 . It is shown that the application of strong magnetic fields (approximately equal to 2T) should significantly improve the filter performance. A method of measuring this improvement is suggested. (author)

Introduction to theory and analysis of resolved (and unresolved) neutron resonances via SAMMY

Energy Technology Data Exchange (ETDEWEB)

Larson, N.M.

1998-07-01

Neutron cross-section data are important for two distinct purposes: first, they provide insight into the nature of matter, thus assisting in the understanding of fundamental physics; second, they are needed for practical applications (e.g., for calculating when and how a reactor will become critical, or how much shielding is needed for storage of nuclear materials, and for medical applications). Neutron cross section data in the resolved-resonance region are generally obtained by time-of-flight experiments, which must be carefully analyzed if they are to be properly understood and utilized. In this paper, important features of the analysis process are discussed, with emphasis on the particular technique used in the analysis code SAMMY. Other features of the code are also described; these include such topics as calculation of group cross sections (including covariance matrices), generation and fitting of integral quantities, and extensions into the unresolved-resonance region and higher-energy regions.

238U neutron-induced fission cross section for incident neutron energies between 5 eV and 3.5 MeV

International Nuclear Information System (INIS)

Difilippo, F.C.; Perez, R.B.; de Saussure, G.; Olsen, D.K.; Ingle, R.W.

1979-01-01

A measurement of the 238 U neutron-induced fission cross section was performed at the ORELA Linac facility in the neutron energy range between 5 eV and 3.5 MeV. The favorable signal-to-background ratio and high resolution of this experiment resulted in the identificaion of 85 subthreshold fission resonances or clusters of resonances in the neutron energy region between 5 eV and 200 keV. The fission data below 100 keV are characteristic of a weak coupling situation between Class I and Class II levels. The structure of the fission levels at the 720 eV and 1210 eV fission clusters is discussed. There is an apparent enhancement of the fission cross section at the opening of the 2 + neutron inelastic channel in 238 U at 45 keV. An enhancement of the subthreshold fission cross section between 100 keV and 200 keV is tentatively interpreted in terms of the presence of a Class II, partially damped vibrational level. There is a marked structure in the fission cross section above 200 keV up to and including the plateau between 2 and 3.5 MeV. 11 figures and 6 tables

An investigation of the reaction mechanism for resonance neutron capture in 54Fe and 62Ni

International Nuclear Information System (INIS)

Mason, J.P.

1986-01-01

The gamma-ray spectra produced following neutron capture in the low energy resonances of 54 Fe and 62 Ni have been observed, using the Harwell 136 MeV electron linear accelerator facility, HELIOS, as a source of pulsed neutrons. The work indicated that, for s-wave capture in the mass region A approx. 55, single particle effects may only be apparent if the size of the valence component is about an order of magnitude larger than the compound nuclear component, and that this may limit the importance of such effects to a few nuclides. In addition, some information was obtained on the radiative decay of p-wave resonances of 54 Fe and 62 Ni. (author)

Influence of fuel composition on the spent fuel verification by Self‑Interrogation Neutron Resonance Densitometry

International Nuclear Information System (INIS)

Rossa, Riccardo; Borella, Alessandro; Van der Meer, Klaas; Labeau, Pierre‑Etienne; Pauly, Nicolas

2015-01-01

The Self‑Interrogation Neutron Resonance Densitometry (SINRD) is a passive Non‑Destructive Assay (NDA) that is developed for the safeguards verification of spent nuclear fuel. The main goal of SINRD is the direct quantification of 239Pu by estimating the SINRD signature, which is the ratio between the neutron flux in the fast energy region and in the region close to the 0.3 eV resonance of 239 Pu. The resonance region was chosen because the reduction of the neutron flux within 0.2-0.4 eV is due mainly to neutron absorption from 239 Pu, and therefore the SINRD signature can be correlated to the 239Pu mass in the fuel assembly. This work provides an estimate of the influence of 239 Pu and other nuclides on the SINRD signature. This assessment is performed by Monte Carlo simulations by introducing several nuclides in the fuel material composition and by calculating the SINRD signature for each case. The reference spent fuel library developed by SCK CEN was used for the detailed fuel compositions of PWR 17x17 fuel assemblies with different initial enrichments, burnup, and cooling times. The results from the simulations show that the SINRD signature is mainly correlated to the 239 Pu mass, with significant influence by 235 U. Moreover, the SINRD technique is largely insensitive to the cooling time of the assembly, while it is affected by the burnup and initial enrichment of the fuel. Apart from 239 Pu and 235 U, many other nuclides give minor contributions to the SINRD signature, especially at burnup higher than 20 GWd/tHM.

Measurements of gamma rays from keV-neutron resonance capture by odd-Z nuclei in the 2s-1d shell region

Energy Technology Data Exchange (ETDEWEB)

Igashira, Masayuki; Lee, Sam Yol; Mizuno, Satoshi; Hori, Jun-ichi [Tokyo Inst. of Tech. (Japan). Research Lab. for Nuclear Reactors; Kitazawa, Hideo

1998-03-01

Measurements of gamma rays from keV-neutron resonance capture by {sup 19}F, {sup 23}Na, and {sup 27}Al, which are odd-Z nuclei in the 2s-1d shell region, were performed, using an anti-Compton HPGe spectrometer and a pulsed neutron source by the {sup 7}Li(p,n){sup 7}Be reaction. Capture gamma rays from the 27-, 49-, and 97-keV resonances of {sup 19}F, the 35- and 53-keV resonances of {sup 23}Na, and the 35-keV resonance of {sup 27}Al were observed. Some results are presented. (author)

Study of some properties of bound levels and virtual levels excited with resonance neutrons; Etude de quelques proprietes de niveaux lies et de niveaux virtuels excites a l'aide de neutrons de resonance

Energy Technology Data Exchange (ETDEWEB)

Alves, R N [Commissariat a l' Energie Atomique, 91 - Saclay (France). Centre d' Etudes Nucleaires

1968-05-01

Many neutron resonance parameters of some nuclei with a spin value I 3/2 ({sup 35}Cl, {sup 37}Cl, {sup 63}Cu, {sup 65}Cu, {sup 197}Au) are determined to find the strength function S{sub 0} with accuracy. For those nuclei, the S{sub 0} value seems not to depend on the spin value J=1 or 2 but could be depend on neutron energy for {sup 197}Au. Total radiative width variation against mass number A and spacing distributions between resonances (for {sup 197}Au) are studied and discussed. Analysis methods of neutron capture experiments are described in detail and level schemes of Cl, Mn, Fe, Co, Cu, Tm, Hg are presented sometimes with the spin value. Intensities of E{sub 1} and M{sub 1} transitions with direct capture and interference effects are discussed in view of experimental results. (author) [French] On determine les parametres des resonances de quelques noyaux de spin I 3/2 ({sup 35}Cl, {sup 37}Cl, {sup 63}Cu, {sup 65}Cu, {sup 197}Au) en nombre suffisant pour obtenir la fonction densite S{sub 0} avec precision. Cette valeur S{sub 0} apparat pour ces noyaux etre independante de la valeur du spin J=1 ou 2 mais para?t, dans le cas de {sup 197}Au, dependre de l'energie. On etudie et on essaie d'interpreter la variation de la largeur radiative totale {gamma}{sub {gamma}} en fonction du nombre de masse A et les distributions des espacements entre resonances pour {sup 197}Au. On expose en detail les methodes d'analyse des experiences de capture et on presente les schemas des niveaux des noyaux: Cl, Mn, Fe, Co, Cu, Tm, Hg. Les intensites des transitions de type E{sub 1} et M{sub 1} ainsi que les effets d'interference et de capture directe sont discutes. (auteur)

Electric and magnetic dipole transitions from broad s-wave neutron resonance in even-even sd-shell nuclei

International Nuclear Information System (INIS)

Kitazawa, H.; Igashira, M.; Shimizu, M.; Muto, K.; Oda, T.; Achiha, Y.; Lee, Y.; Mukai, N.

1992-01-01

Observations have been performed for electromagnetic transitions from the broad s-wave neutron resonances at 658 keV in 24 Mg, at 180 keV in 28 Si, and at 103 keV in 32 S. Capture gamma rays were measured with an anti-Compton NaI(Tl) detector, using a neutron time-of-flight technique. E1 and M1 transitions from those resonances to low-lying states with a strong single-particle character were found. The deduced partial radiative widths for E1 transition are in excellent agreement with the Lane-Mughabghab valence-capture model calculations taking the neutron effective charge, -Ze/A. Moreover, it is shown that essential features of the observed E1 and M1 transitions can be well explained by assuming a configuration-mixing wave function, Ψ i (1/2 + )=a(0 + direct-product 1/2 + )+b(1 + direct-product 1/2 + )+c(1 + direct-product 3/2 + ), for each resonance. The M1 transition strengths are compared also with more detailed shell model calculations in the model space of full (sd) n configurations, using the Wildenthal effective interaction

Mirror and Bragg reflections of neutrons at a nuclear resonance: [Final technical report

International Nuclear Information System (INIS)

Batigun, C.M.; Brugger, R.M.

1987-01-01

These experiments have observed the mirror reflection and Bragg diffraction of neutrons at the energy of a low lying nuclear resonance of 115 In. The reflector was a mirror of In metal with the resonance at 1.457 eV. The mirror reflection for different angles of incidence has been measured and sets of data showing the relative reflectivities have been obtained. For the Bragg diffraction, the crystal was a wafer of InP and several examples of Bragg reflections near 1.455 eV were measured. 4 refs., 12 figs

Enhanced energy storage in chaotic optical resonators

KAUST Repository

Liu, Changxu; Di Falco, Andrea; Molinari, Diego P.; Khan, Yasser; Ooi, Boon S.; Krauss, Thomas F.; Fratalocchi, Andrea

2013-01-01

Chaos is a phenomenon that occurs in many aspects of contemporary science. In classical dynamics, chaos is defined as a hypersensitivity to initial conditions. The presence of chaos is often unwanted, as it introduces unpredictability, which makes it difficult to predict or explain experimental results. Conversely, we demonstrate here how chaos can be used to enhance the ability of an optical resonator to store energy. We combine analytic theory with ab initio simulations and experiments in photonic-crystal resonators to show that a chaotic resonator can store six times more energy than its classical counterpart of the same volume. We explain the observed increase by considering the equipartition of energy among all degrees of freedom of the chaotic resonator (that is, the cavity modes) and discover a convergence of their lifetimes towards a single value. A compelling illustration of the theory is provided by enhanced absorption in deformed polystyrene microspheres. © 2013 Macmillan Publishers Limited. All rights reserved.

Enhanced energy storage in chaotic optical resonators

KAUST Repository

Liu, Changxu

2013-05-05

Chaos is a phenomenon that occurs in many aspects of contemporary science. In classical dynamics, chaos is defined as a hypersensitivity to initial conditions. The presence of chaos is often unwanted, as it introduces unpredictability, which makes it difficult to predict or explain experimental results. Conversely, we demonstrate here how chaos can be used to enhance the ability of an optical resonator to store energy. We combine analytic theory with ab initio simulations and experiments in photonic-crystal resonators to show that a chaotic resonator can store six times more energy than its classical counterpart of the same volume. We explain the observed increase by considering the equipartition of energy among all degrees of freedom of the chaotic resonator (that is, the cavity modes) and discover a convergence of their lifetimes towards a single value. A compelling illustration of the theory is provided by enhanced absorption in deformed polystyrene microspheres. © 2013 Macmillan Publishers Limited. All rights reserved.

Directional effects in transitional resonance spectra and group constants

International Nuclear Information System (INIS)

Hill, R.N.; Oh, K.O.; Rhodes, J.D.

1989-01-01

Analytical exploratory investigations indicate that transition effects such as streaming cause a considerable spatial variation in the neutron spectra across resonances; streaming leads to opposite effects in the forward and backward directions. The neglect of this coupled spatial/angular variations of the transitory resonance spectra is an approximation that is common to all current group constant generation methodologies. This paper presents a description of the spatial/angular coupling of the neutron flux across isolated resonances. It appears to be necessary to differentiate between forward-and backward-directed neutron flux components or even to consider components in narrower angular cones. The effects are illustrated for an isolated actinide resonance in a simplified fast reactor blanket problem. The resonance spectra of the directional flux components φ + and φ - , and even more so the 90-deg cone components, are shown to deviate significantly from the infinite medium approximation, and the differences increase with penetration. The charges in φ + lead to a decreasing scattering group constant that enhances neutron transmission; the changes in φ - lead to an increasing group constant inhibiting backward scattering. Therefore, the changes in the forward-and backward-directed spectra both lead to increased neutron transmission. Conversely, the flux (φ = φ + +φ - ) is shown to agree closely with the infinite medium approximation both in the analytical formulas and in the numerical solution. The directional effect cancel in the summation. The forward-and backward-directed flux components are used as weighting spectra to illustrate the group constant changes for a single resonance

Examination of total cross section resonance structure of niobium and silicon in neutron transmission experiments

Science.gov (United States)

Andrianova, Olga; Lomakov, Gleb; Manturov, Gennady

2017-09-01

The neutron transmission experiments are one of the main sources of information about the neutron cross section resonance structure and effect in the self-shielding. Such kind of data for niobium and silicon nuclides in energy range 7 keV to 3 MeV can be obtained from low-resolution transmission measurements performed earlier in Russia (with samples of 0.027 to 0.871 atom/barn for niobium and 0.076 to 1.803 atom/barn for silicon). A significant calculation-to-experiment discrepancy in energy range 100 to 600 keV and 300 to 800 keV for niobium and silicon, respectively, obtained using the evaluated nuclear data library ROSFOND, were found. The EVPAR code was used for estimation the average resonance parameters in energy range 7 to 600 keV for niobium. For silicon a stochastic optimization method was used to modify the resolved resonance parameters in energy range 300 to 800 keV. The improved ROSFOND evaluated nuclear data files were tested in calculation of ICSBEP integral benchmark experiments.

Resonance analysis of the {sup 12}C,{sup 13}C({alpha},n) reactions and evaluation of neutron yield data of the reaction

Energy Technology Data Exchange (ETDEWEB)

Murata, Toru [AITEL Corp., Tokyo (Japan)

1998-03-01

The {sup 12}C({alpha},n){sup 15}O reaction and the {sup 13}C({alpha},n){sup 16}O reaction were analyzed with a resonance formula in the incident {alpha}-particle energy range of 1.0 to 16.0 MeV. With the obtained resonance parameters, branching ratios of the emitted neutrons to the several levels of the residual nucleus and their angular distributions were calculated to obtain the energy spectrum of emitted neutrons. Thick target neutron yield of carbon were also calculated and compared with the experimental data. (author)

Modified model of neutron resonances widths distributions. Results of reduced neutron widths approximation for mass region 35 ≤ A ≤ 249

International Nuclear Information System (INIS)

Sukhovoj, A.M.; Khitrov, V.A.

2011-01-01

The distributions of the reduced neutron widths of s-, p- and d-resonances of nuclei of any type from nuclear mass region 35 ≤ A ≤ 249 were approximated with maximal precision by the model which presents experimental data set as a superposition of a maximum of four independent neutron amplitudes. Under the assumption that each of these amplitudes has the Gauss distribution with the unique maximum there were determined the most probable values of contribution of each amplitude in summary width distribution, their most probable mean values and dispersions. Comparison of the obtained χ 2 values with value χ 2 at description of the experimental data by one distribution of neutron amplitudes with best fitted parameters shows that all widths from more than 157 analyzed data sets can have different types of wave functions

Europium resonance parameters from neutron capture and transmission measurements in the energy range 0.01–200 eV

International Nuclear Information System (INIS)

Leinweber, G.; Barry, D.P.; Burke, J.A.; Rapp, M.J.; Block, R.C.; Danon, Y.; Geuther, J.A.; Saglime III, F.J.

2014-01-01

Highlights: • Metal samples were sealed and imaged with X-rays to determine sample uniformity. • Eleven new resonances were identified below 100 eV. • The resonance regions of 151 Eu and 153 Eu have been extended from 100 to 200 eV. • The thermal total cross section for 151 Eu was measured, up (9 ± 3)% from ENDF/B-VII.1. • Radiation widths were assigned for all resonances from experimental data. - Abstract: Europium is a good absorber of neutrons suitable for use as a nuclear reactor control material. It is also a fission product in the low-yield tail at the high end of the fission fragment mass distribution. Measurements have been made of the stable isotopes with natural and enriched samples. The linear electron accelerator center (LINAC) at the Rensselaer Polytechnic Institute (RPI) was used to explore neutron interactions with europium in the energy region from 0.01 to 200 eV. Neutron capture and transmission measurements were performed by the time-of-flight technique. Two transmission measurements were performed at flight paths of 15 and 25 m with 6 Li glass scintillation detectors. The neutron capture measurements were performed at a flight path of 25 m with a 16-segment sodium iodide multiplicity detector. Resonance parameters were extracted from the data using the multilevel R-matrix Bayesian code SAMMY. A table of resonance parameters and their uncertainties is presented. To prevent air oxidation metal samples were sealed in airtight aluminum cans in an inert environment. Metal samples of natural europium, 47.8 atom% 151 Eu, 52.2 atom% 153 Eu, as well as metal samples enriched to 98.77 atom% 153 Eu were measured. The measured neutron capture resonance integral for 153 Eu is (9.9 ± 0.4)% larger than ENDF/B-VII.1. The capture resonance integral for 151 Eu is (7 ± 1)% larger than ENDF/B-VII.1. Another significant finding from these measurements was a significant increase in thermal total cross section for 151 Eu, up (9 ± 3)% from ENDF/B-VII.1

Magnetic neutron scattering resonance of high-¤Tc¤ superconductors in external magnetic fields: An SO(5) study

DEFF Research Database (Denmark)

Mortensen, Asger; Rønnow, Henrik Moodysson; Bruus, Henrik

2000-01-01

The magnetic resonance at 41 meV observed in neutron scattering studies of YBa2Cu3O7 holds a key position in the understanding of high-T-c, superconductivity. Within the SO(5) model for superconductivity and antiferromagnetism, we have calculated the effect of an applied magnetic field on the neu......The magnetic resonance at 41 meV observed in neutron scattering studies of YBa2Cu3O7 holds a key position in the understanding of high-T-c, superconductivity. Within the SO(5) model for superconductivity and antiferromagnetism, we have calculated the effect of an applied magnetic field...

The production of radioisotopes for medical applications by the adiabatic resonance crossing (ARC) technique

CERN Document Server

Froment, P; Delbar, T; Ryckewaert, G; Tilquin, I; Vervier, J

2002-01-01

The Transmutation by Adiabatic Resonance Crossing (TARC) technique has been proposed by Rubbia (Resonance enhanced neutron captures for element activation and waste transmutation, CERN-LHC/97-0040EET, 1997; TARC collaboration, Neutron-driven nuclear transmutation by adiabatic resonance crossing, CERN-SL-99-036EET, 1999; Abanades et al., Nucl. Instr. and Meth. A 487 (2002) 577) for element activation and waste transmutation. We investigate the possibility to use this technique for the industrial production of **9**9Mo and **1**2**5Xe by resonance neutron capture in **9**8Mo and **1**2**4Xe, respectively. Their daughters, i.e. **9**9**mTc and **1**2**5I, are widely used in medical applications. The high neutron flux needed is produced by bombarding a thick Be target with 65 or 75 MeV proton beam (few microamperes). This target is placed at the centre of a large cubic lead assembly (1.6 m side, purity: 99.999%). The neutrons are progressively slowed down by elastic scattering on lead, and their energies "scan" t...

Intense resonance neutron source (IREN) - new pulsed source for nuclear physical and applied investigations

International Nuclear Information System (INIS)

Anan'ev, V.D.; Furman, W.I.; Kobets, V.V.; Meshkov, I.N.; Pyataev, V.G.; Shirkov, G.D.; Shvets, V.A.; Sumbaev, A.P.; Kuatbekov, R.P.; Tret'yakov, I.T.; Frolov, A.R.; Gurov, S.M.; Logachev, P.V.; Pavlov, V.M.; Skarbo, B.A.

2005-01-01

An accelerator-driven subcritical system (200 MeV electron linac + metallic plutonium subcritical core) IREN is constructed at the Joint Institute for Nuclear Research (JINR). The new pulsed neutron source IREN is optimized for maximal yield of resonance neutrons (1-10 5 eV). The S-band electron linac with a pulse duration near 200 ns, repetition rate up to 150 Hz and the mean beam power 10 kW delivers 200-MeV electrons onto a specially designed tungsten target (an electron-neutron converter) situated in the center of a very compact and fast subcritical assembly with K eff 15 per second. A mean fission power of the multiplying target is planned to be near 15 kW. The current status of the project is presented

The TARC experiment (PS211): neutron-driven nuclear transmutation by adiabatic resonance crossing

International Nuclear Information System (INIS)

Revol, J.P.; Arnould, H.; Bompas, C.A.

1999-01-01

The main purpose of the TARC experiment is to demonstrate the possibility of using Adiabatic Resonance Crossing (ARC) to destroy efficiently Long-Lived Fission Fragments (LLFFs) in accelerator-driven systems and to validate a new simulation developed in the framework of the Energy Amplifier programme. An experimental set-up was installed in a CERN PS beam line to study how neutrons produced by spallation at relatively high energy (E n ≥1 MeV) slow down quasi adiabatically with almost flat isolethargic energy distribution and reach the capture resonance energy of an element to be transmuted where they will have a high probability of being captured. Precision measurements of energy and space distributions of spallation neutrons (using 2.5 GeV/c and 3.5 GeV/c protons) slowing down in a 3.3 m x 3.3 m x 3 m lead volume and of neutron capture rates of LLFFs 99 Tc, 129 I, and several other elements were performed. An appropriate formalism and appropriate computational tools necessary for the analysis and understanding of the data were developed and validated in detail. Our direct experimental observation of ARC demonstrates the possibility to destroy, in a parasitic mode, outside the Energy Amplifier core, large amounts of 99 Tc or 129 I at a rate exceeding the production rate, thereby making it practical to reduce correspondingly the existing stockpile of LLFFs. In addition, TARC opens up new possibilities for radioactive isotope production as an alternative to nuclear reactors, in particular for medical applications, as well as new possibilities for neutron research and industrial applications. (orig.)

Enhanced THz extinction in arrays of resonant semiconductor particles.

Science.gov (United States)

Schaafsma, Martijn C; Georgiou, Giorgos; Rivas, Jaime Gómez

2015-09-21

We demonstrate experimentally the enhanced THz extinction by periodic arrays of resonant semiconductor particles. This phenomenon is explained in terms of the radiative coupling of localized resonances with diffractive orders in the plane of the array (Rayleigh anomalies). The experimental results are described by numerical calculations using a coupled dipole model and by Finite-Difference in Time-Domain simulations. An optimum particle size for enhancing the extinction efficiency of the array is found. This optimum is determined by the frequency detuning between the localized resonances in the individual particles and the Rayleigh anomaly. The extinction calculations and measurements are also compared to near-field simulations illustrating the optimum particle size for the enhancement of the near-field.

Neutron spectometers

International Nuclear Information System (INIS)

Poortmans, F.

1977-01-01

Experimental work in the field of low-energy neutron physics can be subdivided into two classes: 1)Study of the decay process of the compound-nucleus state as for example the study of the capture gamma rays and of the neutron induced fission process; 2)Study of the reaction mechanism, mainly by measuring the reaction cross-sections and resonance parameters. These neutron cross-sections and resonance parameters are also important data required for many technological applications especially for reactor development programmes. In general, the second class of experiments impose other requirements on the neutron spectrometer than the first class. In most cases, a better neutron energy resolution and a broader neutron energy range are required for the study of the reaction mechanism than for the study of various aspects of the decay process. (author)

Beta-decay measurements of neutron-rich thallium, lead, and bismuth by means of resonant laser ionisation

Science.gov (United States)

Franchoo, S.; de Witte, H.; Andreyev, A. N.; Cederka¨Ll, J.; Dean, S.; de Smet, A.; Eeckhaudt, S.; Fedorov, D. V.; Fedosseev, V. N.; G´Rska, M.; Huber, G.; Huyse, M.; Janas, Z.; Ko¨Ster, U.; Kurcewicz, W.; Kurpeta, J.; Mayer, P.; Płchocki, A.; van de Vel, K.; van Duppen, P.; Weissman, L.; Isolde Collaboration

2004-04-01

Neutron-rich thallium, lead, and bismuth isotopes were investigated at the ISOLDE facility. After mass separation and resonant laser ionisation of the produced activity, new spectroscopic data were obtained for 215,218Bi and 215Pb. An attempt to reach heavy thallium had to be abandoned because of a strong francium component in the beam that gave rise to a neutron background through (α,n) reactions on the aluminium walls of the experimental chamber.

Resonance-enhanced optical forces between coupled photonic crystal slabs.

Science.gov (United States)

Liu, Victor; Povinelli, Michelle; Fan, Shanhui

2009-11-23

The behaviors of lateral and normal optical forces between coupled photonic crystal slabs are analyzed. We show that the optical force is periodic with displacement, resulting in stable and unstable equilibrium positions. Moreover, the forces are strongly enhanced by guided resonances of the coupled slabs. Such enhancement is particularly prominent near dark states of the system, and the enhancement effect is strongly dependent on the types of guided resonances involved. These structures lead to enhancement of light-induced pressure over larger areas, in a configuration that is directly accessible to externally incident, free-space optical beams.

Symmetry of neutron-induced 235U fission at individual resonances. III

Energy Technology Data Exchange (ETDEWEB)

Cowan, G A; Bayhurst, B P; Prestwood, R J; Gilmore, J S; Knobeloch, G W [Los Alamos Scientific Laboratory, University of California, Los Alamos, NM (United States)

1970-05-15

A number of experiments have been described in recent years which document variations in the yields of symmetric or near-symmetric fission products at resonances in 235-U and 239-Pu neutron-induced fission. In the case of 239-Pu fission it has been demonstrated in a statistically significant sample of s-wave neutron resonances (J{sup {pi}} = 0{sup +} or 1{sup +}) that the 0{sup +} levels have a characteristic 115Cd yield which is a factor of four higher than the yield at 1{sup +} levels. The fission widths of the J = 0 levels are larger than the J = 1 levels by a factor of ten. The populations of the two groups are in reasonable agreement with the expected (2J + 1) distributions. Previous efforts to obtain equally detailed data in 235-U fission and 233-U fission by the 'wheel' technique have not been entirely successful due in large part to the high level densities in the epithermal excitation functions of these nuclides and the consequent difficulty in characterizing fission yields in a sufficiently large and well-resolved sample of levels. In a recent 'wheel' experiment (late summer, 1969) vith a 235-U target the energy resolution was sufficiently improved in the region 20 eV-60 eV to allow characterization of a sample of 38 reasonably well-resolved levels by their relative symmetry of fission. (author)

What Do s- and p-Wave Neutron Average Radiative Widths Reveal

Energy Technology Data Exchange (ETDEWEB)

Mughabghab, S.F.

2010-04-30

A first observation of two resonance-like structures at mass numbers 92 and 112 in the average capture widths of the p-wave neutron resonances relative to the s-wave component is interpreted in terms of a spin-orbit splitting of the 3p single-particle state into P{sub 3/2} and P{sub 1/2} components at the neutron separation energy. A third structure at about A = 124, which is not correlated with the 3p-wave neutron strength function, is possibly due to the Pygmy Dipole Resonance. Five significant results emerge from this investigation: (i) The strength of the spin-orbit potential of the optical-model is determined as 5.7 {+-} 0.5 MeV, (ii) Non-statistical effects dominate the p-wave neutron-capture in the mass region A = 85 - 130, (iii) The background magnitude of the p-wave average capture-width relative to that of the s-wave is determined as 0.50 {+-} 0.05, which is accounted for quantitatively in tenns of the generalized Fermi liquid model of Mughabghab and Dunford, (iv) The p-wave resonances arc partially decoupled from the giant-dipole resonance (GDR), and (v) Gamma-ray transitions, enhanced over the predictions of the GDR, are observed in the {sup 90}Zr - {sup 98}Mo and Sn-Ba regions.

Experimental verification of neutron phenomenology in lead and transmutation by adiabatic resonance crossing in accelerator driven systems

CERN Document Server

Arnould, H; Del Moral, R; Lacoste, V; Vlachoudis, V; Aleixandre, J; Bueno, J; Cerro, E; González, O; Tamarit, J; Andriamonje, Samuel A; Brozzi, Delecurgo; Buono, S; Carminati, F; Casagrande, Federico; Cennini, P; Collar, J I; Dumps, Ludwig; Gelès, C; Goulas, I; Fernández, R; Kadi, Y; Klapisch, Robert; Oropesa, J; Placci, Alfredo; Revol, Jean Pierre Charles; Rubbia, Carlo; Rubio, Juan Antonio; Saldaña, F; Embid, M; Gálvez, J; López, C; Pérez-Enciso, E; Poza, M; Sirvent, C; Vieira, S L; Abánades, A; García, J; Martínez-Val, J M; Perlado, M; González, E; Hussonnois, M; Le Naour, C; Trubert, D; Belle, E; Giorni, A; Heuer, R D; Loiseaux, J M; Méplan, O; Nifenecker, H; Schussler, F; Viano, J B; Angelopoulos, Angelos; Apostolakis, Alcibiades J; Karaiskos, P; Sakelliou, L; Kokkas, P; Pavlopoulos, P; Eleftheriadis, C; Kitis, G; Papadopoulos, I M; Savvidis, E; Tzima, A; Zioutas, Konstantin; Díez, S; Pérez-Navarro, A

1999-01-01

Energy and space distributions of spallation neutrons (from 2.5 and 3.57 GeV/c CERN proton beams) slowing down in a 3.3*3.3*3 m/sup 3/ lead volume and neutron capture rates on long-lived fission fragments /sup 99/Tc and /sup 129/I demonstrate that Adiabatic Resonance Crossing (ARC) can be used to eliminate efficiently such nuclear waste and validate innovative simulation. (17 refs).

Intensity enhancement of cold neutrons from a coupled liquid-hydrogen moderator for pulsed cold neutron sources

International Nuclear Information System (INIS)

Ogawa, Y.; Kiyanagi, Y.; Kosugi, N.; Iwasa, H.; Furusaka, M.; Watanabe, N.

1999-01-01

In order to obtain higher cold neutron intensity from a coupled liquid-hydrogen moderator with a premoderator for pulsed cold neutron sources, we examined a partial enhancement method, namely, narrow beam extraction for both a flat liquid-hydrogen moderator and a single-groove one. Combined with the narrow beam extraction, which is especially suitable for small-angle scattering and neutron reflectometry experiments, a single-groove moderator provides higher intensity, by about 30%, than a flat-surface moderator at the region of interest on a viewed surface. The effect of double-side beam extraction from such moderators on the intensity gain factor is also discussed. (author)

Nuclear-structure aspects of theoretical neutron physics

International Nuclear Information System (INIS)

Soloviev, V.G.

1976-01-01

The structure of neutron resonances is studied on the basis of the semimicroscopic nuclear theory. Few-quasiparticle components of the wave functions of neutron resonances are calculated which determine the neutron and radiational strength functions. It is stated that it is necessary to clarify the role of their many-quasiparticle components. The structure of neutron resonances is studied within the framework of the general approach based on the operator form of the wave functions. The role of three-quasiparticle components in the wave functions of neutron resonances is studied and the cases of validity of the valence neutron model are pointed out. It is shown that the experimental information about the structure of neutron resonances is limited to few-quasiparticle components which are of 10 -3 -10 -6 part of the normalization of their wave functions. To study the structure of neutron resonances it is necessary to find the values of many-quasiparticle components of the wave functions. The ways of experimental finding of these components based on the study of γ-transitions between highly excited states are discussed. The fragmentation of single-particle states in deformed nuclei is studied within the framework of the model based on the quasiparticle--phonon interactions. The S-, p-, and α-wave neutron strength functions are determined

Reaction rate of the 13C(α,n)16O neutron source using the ANC of the -3 keV resonance measured with the THM

International Nuclear Information System (INIS)

La Cognata, M; Spitaleri, C; Trippella, O; Kiss, G G; Guardo, G L; Puglia, S M R; Romano, S; Spartà, R; Rogachev, G V; Avila, M; Koshchiy, E; Kuchera, A; Santiago, D; Mukhamedzhanov, A M; Lamia, L

2016-01-01

The s-process is responsible of the synthesis of most of the nuclei in the mass range 90 ≤ A ≤ 208. It consists in a series of neutron capture reactions on seed nuclei followed by β-decays, since the neutron accretion rate is slower than the β-decay rate. Such small neutron flux is supplied by the 13 C(α,n) 16 O reaction. It is active inside the helium-burning shell of asymptotic giant branch stars, at temperatures < 10 8 K, corresponding to an energy interval of 140–230 keV. In this region, the astrophysical S (E)-factor is dominated by the −3 keV sub-threshold resonance due to the 6.356 MeV level in 17 O. In this work, we have applied the Trojan Horse Method (THM) to the 13 C( 6 Li,n 16 O)d quasi-free reaction to extract the 6.356 MeV level resonance parameters, in particular the asymptotic normalization coefficient . A preliminary analysis of a partial data set has lead to , slightly larger than the values in the literature. However, the deduced 13 C(α, n) 16 O reaction rate is in agreement with most results in the literature at ∼ 10 8 K, with enhanced accuracy thanks to our innovative approach merging together ANC and THM. (paper)

Automation on computers of the partial area method for the analysis of 's' neutron induced resonances. I. Without interference terms. (1962); Automatisation sur ordinateur de la methode des aires partielle dans l'analyse des resonances induites par les neutrons 's'. I. sans terme d'interference. (1962)

Energy Technology Data Exchange (ETDEWEB)

Bianchi, G; Corge, C R [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1962-07-01

This report deals with numerical analysis of transmission resonances induced by 's' wave neutrons in time of flight experiments. The analysis method used is the partial area one. The only case treated here, in this first part, is the one when the interference term can be neglected. Programs and subroutines are thoroughly described, which determine from experimental raw data the resonant transmission, the partial areas, and the resonance parameters. (authors) [French] Le present rapport a pour objet l'analyse numerique sur ordinateur IBM 7090, des resonances dues aux neutrons 's' dans les experiences de transmission par temps de vol, la methode d'analyse utilisee etant la methode des aires partielles. Dans cette premiere partie, seul a ete envisage le cas ou le terme d'interference peut etre neglige. On y trouvera une description detaillee des programmes et sous programmes elabores pour determiner les transmissions resonantes avec leur trace, a partir des donnees experimentales brutes, les aires partielles afferentes ainsi que les parametres caracteristiques des resonances. (auteurs)

Photon strength functions in Gd isotopes studied from radiative capture of resonance neutrons

Directory of Open Access Journals (Sweden)

Kroll J.

2014-04-01

Full Text Available The experimental spectra of γ rays following radiative neutron capture on isolated resonances of stable 152,154–158Gd targets were measured by the DANCE calorimeter installed at the Los Alamos Neutron Scattering Center in New Mexico, USA. These spectra were analyzed within the extreme statistical model to get new information on the photon strength functions. Special emphasis was put on study of the scissors vibrational mode present in these isotopes. Our data show that the scissors-mode resonances are built not only on the ground states but also on the excited levels of all studied Gd isotopes. The scissors mode strength observed in 157,159Gd products is significantly higher than in neighboring even-even nuclei 156,158Gd. Such a difference indicates the existence of an odd-even effect in the scissors mode strength. Moreover, there exists no universal parameter-free model of the electric dipole photon strength function describing the experimental data in all of the Gd isotopes studied. The results for the scissors mode are compared with the (γ, γ′ data for the ground-state transitions and with the results from 3He-induced reactions.

Resonance parameters for measured keV neutron capture cross sections

Energy Technology Data Exchange (ETDEWEB)

Musgrove, A.R. de L

1969-05-01

All available neutron capture cross sections in the keV region ({approx} to 100 keV) have been fitted with resonance parameters. Capture cross sections for nuclides with reasonably well known average s-wave parameters, but no measured cross section, have been calculated and tabulated using p-and d- wave strength functions interpolated between fitted values. Several of these nuclides are of interest in the theory of slow nucleosynthesis of heavy elements in stars, and the product of cosmic abundance (due to the s-process) and capture cross section at 30 keV has been plotted versus mass number. (author)

Super-radiance and the widths of neutron resonances in the compound nucleus

International Nuclear Information System (INIS)

Auerbach, N

2012-01-01

In the 1950s the possibility of forming a 'super-radiant' (SR) state in a gas of atoms confined to a volume of a size smaller than the wave length of radiation was suggested by Dicke. During the years this mechanism was applied to many phenomena in many different fields. Here it is used in the discussion of the statistics of resonance widths in a many-body system with open decay channels. Depending on the strength of the coupling to the continuum such systems show deviations from the Porter-Thomas distribution. In the limit of very strong coupling this leads to super-radiance. The results presented are important for the understanding of recent experimental data concerning the widths distribution of neutron resonances in nuclei.

Threshold enhancement of diphoton resonances

CERN Document Server

Bharucha, Aoife; Goudelis, Andreas

2016-10-10

The data collected by the LHC collaborations at an energy of 13 TeV indicates the presence of an excess in the diphoton spectrum that would correspond to a resonance of a 750 GeV mass. The apparently large production cross section is nevertheless very difficult to explain in minimal models. We consider the possibility that the resonance is a pseudoscalar boson $A$ with a two--photon decay mediated by a charged and uncolored fermion having a mass at the $\\frac12 M_A$ threshold and a very small decay width, $\\ll 1$ MeV; one can then generate a large enhancement of the $A\\gamma\\gamma$ amplitude which explains the excess without invoking a large multiplicity of particles propagating in the loop, large electric charges and/or very strong Yukawa couplings. The implications of such a threshold enhancement are discussed in two explicit scenarios: i) the Minimal Supersymmetric Standard Model in which the $A$ state is produced via the top quark mediated gluon fusion process and decays into photons predominantly through...

Applications of resonance ionization spectroscopy in neutron dosimetry

International Nuclear Information System (INIS)

Whitaker, T.J.; Hurst, G.S.

1982-01-01

Resonance Ionization Spectroscopy (RIS) is a new analytical technique which is orders of magnitude more sensitive than previous methods of atomic analysis. In this method, lasers are used to selectively excite specific electronic transitions in the element being analyzed. A second laser photon can then ionize the excited atoms. Commercial lasers have sufficient intensity to assure that every atom located in the central portion of the laser beam will be ionized, and therefore can be detected. In this paper the concept of a xenon-containing matrix (XCM) which would release xenon atoms when exposed to neutrons is explored. Accumulated xenon would be measured using RIS to determine total dose. The total dosimeter would consist of an XCM, a radiator, and an encapsulation around both to contain released xenon atoms

Study of some properties of bound levels and virtual levels excited with resonance neutrons; Etude de quelques proprietes de niveaux lies et de niveaux virtuels excites a l'aide de neutrons de resonance

Energy Technology Data Exchange (ETDEWEB)

Alves, R.N. [Commissariat a l' Energie Atomique, 91 - Saclay (France). Centre d' Etudes Nucleaires

1968-05-01

Many neutron resonance parameters of some nuclei with a spin value I 3/2 ({sup 35}Cl, {sup 37}Cl, {sup 63}Cu, {sup 65}Cu, {sup 197}Au) are determined to find the strength function S{sub 0} with accuracy. For those nuclei, the S{sub 0} value seems not to depend on the spin value J=1 or 2 but could be depend on neutron energy for {sup 197}Au. Total radiative width variation against mass number A and spacing distributions between resonances (for {sup 197}Au) are studied and discussed. Analysis methods of neutron capture experiments are described in detail and level schemes of Cl, Mn, Fe, Co, Cu, Tm, Hg are presented sometimes with the spin value. Intensities of E{sub 1} and M{sub 1} transitions with direct capture and interference effects are discussed in view of experimental results. (author) [French] On determine les parametres des resonances de quelques noyaux de spin I 3/2 ({sup 35}Cl, {sup 37}Cl, {sup 63}Cu, {sup 65}Cu, {sup 197}Au) en nombre suffisant pour obtenir la fonction densite S{sub 0} avec precision. Cette valeur S{sub 0} apparat pour ces noyaux etre independante de la valeur du spin J=1 ou 2 mais para?t, dans le cas de {sup 197}Au, dependre de l'energie. On etudie et on essaie d'interpreter la variation de la largeur radiative totale {gamma}{sub {gamma}} en fonction du nombre de masse A et les distributions des espacements entre resonances pour {sup 197}Au. On expose en detail les methodes d'analyse des experiences de capture et on presente les schemas des niveaux des noyaux: Cl, Mn, Fe, Co, Cu, Tm, Hg. Les intensites des transitions de type E{sub 1} et M{sub 1} ainsi que les effets d'interference et de capture directe sont discutes. (auteur)

Enhanced finite difference scheme for the neutron diffusion equation using the importance function

International Nuclear Information System (INIS)

Vagheian, Mehran; Vosoughi, Naser; Gharib, Morteza

2016-01-01

Highlights: • An enhanced finite difference scheme for the neutron diffusion equation is proposed. • A seven-step algorithm is considered based on the importance function. • Mesh points are distributed through entire reactor core with respect to the importance function. • The results all proved that the proposed algorithm is highly efficient. - Abstract: Mesh point positions in Finite Difference Method (FDM) of discretization for the neutron diffusion equation can remarkably affect the averaged neutron fluxes as well as the effective multiplication factor. In this study, by aid of improving the mesh point positions, an enhanced finite difference scheme for the neutron diffusion equation is proposed based on the neutron importance function. In order to determine the neutron importance function, the adjoint (backward) neutron diffusion calculations are performed in the same procedure as for the forward calculations. Considering the neutron importance function, the mesh points can be improved through the entire reactor core. Accordingly, in regions with greater neutron importance, density of mesh elements is higher than that in regions with less importance. The forward calculations are then performed for both of the uniform and improved non-uniform mesh point distributions and the results (the neutron fluxes along with the corresponding eigenvalues) for the two cases are compared with each other. The results are benchmarked against the reference values (with fine meshes) for Kang and Rod Bundle BWR benchmark problems. These benchmark cases revealed that the improved non-uniform mesh point distribution is highly efficient.

Trampoline metamaterial: Local resonance enhancement by springboards

Science.gov (United States)

Bilal, Osama R.; Hussein, Mahmoud I.

2013-09-01

We investigate the dispersion characteristics of locally resonant elastic metamaterials formed by the erection of pillars on the solid regions in a plate patterned by a periodic array of holes. We show that these solid regions effectively act as springboards leading to an enhanced resonance behavior by the pillars when compared to the nominal case of pillars with no holes. This local resonance amplification phenomenon, which we define as the trampoline effect, is shown to cause subwavelength bandgaps to increase in size by up to a factor of 4. This outcome facilitates the utilization of subwavelength metamaterial properties over exceedingly broad frequency ranges.

Comparative measurements of independent yields of 239Pu fission fragments induced by thermal and resonance neutrons

International Nuclear Information System (INIS)

Gundorin, N.A.; Kopach, Y.N.; Telezhnikov, S.A.

1994-01-01

The independent yields of 239 Pu fission fragments by means of gamma-spectroscopy method were measured for light and heavy groups on the IBR-30 reactor in Dubna. Comparative analysis of experimental data for fission induced by thermal and resonance neutrons was performed. The possibilities to increase the measurement's precision consist of the employment of a HPGe detector with high efficiency and its open-quotes activeclose quotes shielding in the gamma spectrometer, as well as a high speed electronics system. In this way the number of identified fragments will be increased and independent yields will be measured to a precision of 1-3%. Measurements at the source with shorter neutron pulse duration to increase neutron energy resolution will be possible after the reconstruction of a modern neutron source in Dubna in accordance with the IREN project

The description of neutron and giant resonances within the quasiparticle-phonon nuclear model

International Nuclear Information System (INIS)

Soloviev, V.G.

1978-01-01

The general assumptions of the quasiparticle-phonon model of complex nuclei are given. The choice of the model Hamiltonian as an average field and residual forces is discussed. The phonon description and quasiparticle-phonon interaction are presented. The system of basic equations and their approximate solutions are obtained. The approximation is chosen so as to obtain the most correct description of few-quasiparticle components rather than of the whole wave function. The method of strength functions is presented, which plays a decisive role in practical realization of the quasiparticle-phonon model for the description of some properties of complex nuclei. The range of applicability of the quasiparticle-phonon nuclear model is determined as few-quasiparticle components of the wave functions at low, intermediate and high excitation energies averaged in a certain energy interval. The fragmentation of single-particle states in deformed nuclei is studied within this model. The dependence of neutron strength functions on the excitation energy is investigated for the transfer reactions of the type (d,p) and (d,t). The s - ,p - , and d-wave neutron strength functions are calculated at the neutron binding energy Bsub(n). A satisfactory agreement with experiment is obtained. A correct description of the radiative strength functions in spherical nuclei is obtained. The influence of the tail of the giant dipole resonance on the E1-strength functions is studied. The energies and EΛ-strength functions for giant multipole resonances in spherical and deformed nuclei are calculated. A correct description of their widths is obtained. (author)

Threshold enhancement of diphoton resonances

Directory of Open Access Journals (Sweden)

Aoife Bharucha

2016-10-01

Full Text Available We revisit a mechanism to enhance the decay width of (pseudo-scalar resonances to photon pairs when the process is mediated by loops of charged fermions produced near threshold. Motivated by the recent LHC data, indicating the presence of an excess in the diphoton spectrum at approximately 750 GeV, we illustrate this threshold enhancement mechanism in the case of a 750 GeV pseudoscalar boson A with a two-photon decay mediated by a charged and uncolored fermion having a mass at the 12MA threshold and a small decay width, <1 MeV. The implications of such a threshold enhancement are discussed in two explicit scenarios: i the Minimal Supersymmetric Standard Model in which the A state is produced via the top quark mediated gluon fusion process and decays into photons predominantly through loops of charginos with masses close to 12MA and ii a two Higgs doublet model in which A is again produced by gluon fusion but decays into photons through loops of vector-like charged heavy leptons. In both these scenarios, while the mass of the charged fermion has to be adjusted to be extremely close to half of the A resonance mass, the small total widths are naturally obtained if only suppressed three-body decay channels occur. Finally, the implications of some of these scenarios for dark matter are discussed.

Resonantly enhanced collisional ionization measurements of radionuclides

International Nuclear Information System (INIS)

Whitaker, T.J.; Bushaw, B.A.; Gerke, G.K.

1986-01-01

The authors developed a new laser technique to analyze for radionuclides at extremely low levels. The technique, called resonantly enhanced collisional ionization (RECI), uses two nitrogen-laser pumped dye lasers to excite the target isotope to a high-energy Rydberg state. Atoms in these Rydberg states (within a few hundred wavenumbers in energy from the ionization threshold) efficiently ionize upon colliding with an inert gas and the ions can be detected by conventional means. The principal advantage of resonantly-enhanced collisional ionization is the extreme sensitivity coupled with its relative simplicity and low cost. Actinides typically have an ionization potential of about 6eV (uranium I.P. = 6.2 eV, plutonium I.P. = 5.7 eV). Two-step laser excitation to a state just below threshold requires wavelengths in the blue region of the visible spectrum. They showed that when both steps in the excitation process are resonant steps, relatively low-power lasers can populate the Rydberg state with almost unit efficiency. This is because the resonant excitations have much larger cross-sections than do photoionization processes. They also demonstrated that a few torr of a buffer gas will cause most of the excited-state atoms to be ionized

MIRANDA - a module based on multiregion resonance theory for generating cross sections within the AUS neutronics code system

International Nuclear Information System (INIS)

Robinson, G.S.

1985-12-01

MIRANDA is the cross-section generation module of the AUS neutronics code system used to prepare multigroup cross-section data which are pertinent to a particular study from a general purpose multigroup library of cross sections. Libraries have been prepared from ENDF/B which are suitable for thermal and fast fission reactors and for fusion blanket studies. The libraries include temperature dependent data, resonance cross sections represented by subgroup parameters and may contain photon as well as neutron data. The MIRANDA module includes a multiregion resonance calculation in slab, cylinder or cluster geometry, a homogeneous B L flux solution, and a group condensation facility. This report documents the modifications to an earlier version of MIRANDA and provides a complete user's manual

Non-resonant terahertz field enhancement in periodically arranged nanoslits

DEFF Research Database (Denmark)

Novitsky, Andrey; Ivinskaya, Aliaksandra; Zalkovskij, Maksim

2012-01-01

We analyze ultra strong non-resonant field enhancement of THz field in periodic arrays of nanoslits cut in ultrathin metal films. The main feature of our approach is that the slit size and metal film thickness are several orders of magnitude smaller than the wavelength λ of the impinging radiatio...... by the microscopic Drude-Lorentz model taking into account retardation processes in the metal film and validated by the finite difference frequency domain method. We expect sensor and modulation applications of the predicted giant broadband field enhancement.......We analyze ultra strong non-resonant field enhancement of THz field in periodic arrays of nanoslits cut in ultrathin metal films. The main feature of our approach is that the slit size and metal film thickness are several orders of magnitude smaller than the wavelength λ of the impinging radiation...... approaches the THz wavelength but before entering the Raleigh-Wood anomaly, the field enhancement in nanoslit stays close to that in a single isolated slit, i.e., the well-known inversefrequency dependence. Both regimes are non-resonant and thus extremely broadband for P

Resonance-enhanced electron-impact excitation of Cu-like gold

Science.gov (United States)

Xia, L.; Zhang, C. Y.; Si, R.; Guo, X. L.; Chen, Z. B.; Yan, J.; Li, S.; Chen, C. Y.; Wang, K.

2017-09-01

Employing the independent-process and isolated-resonance approximations using distorted-waves (IPIRDW), we have performed a series of calculations of the resonance-enhanced electron-impact excitations (EIE) among 27 singly excited levels from the n ≤ 6 configurations of Cu-like gold (Au, Z = 79). Resonance excitation (RE) contributions from both the n = 4 → 4 - 7 and n = 3 → 4 core excitations have been considered. Our results demonstrate that RE contributions are significant and enhance the effective collision strengths (ϒ) of certain excitations by up to an order of magnitude at low temperature (106.1 K), and are still important at relatively high temperature (107.5 K). Results from test calculations of the resonance-enhanced EIE processes among 16 levels from the n ≤ 5 configurations using both the Dirac R-matrix (DRM) and IPIRDW approaches agree very well with each other. This means that the close-coupling effects are not important for this ion, and thus warrants the reliability of present resonance-enhanced EIE data among the 27 levels. The results from the collisional-radiative model (CRM) show that, at 3000 eV, near where Cu-like Au is most abundant, RE contributions have important effects (up to 25%) on the density diagnostic line intensity ratios, which are sensitive near 1020 cm-3. The present work is the first EIE research including RE contributions for Cu-like Au. Our EIE data are more accurate than previous results due to our consideration of RE contributions, and the data should be helpful for modeling and diagnosing a variety of plasmas.

Representation of the neutron cross sections of several fertile and fissile nuclei in the resonance regions

Energy Technology Data Exchange (ETDEWEB)

de Saussure, G.; Perez, R.B. (Oak Ridge National Lab., TN (USA))

1982-01-01

Several problems related to the measurement, analysis and evaluation of the neutron cross sections of the main fertile and fissile nuclides in the resonance region are reviewed. In particular the ENDF/B-V representation of these cross sections is discussed. In recent years little progress has been made in improving our knowledge of the resolved resonance parameters of the fertile nuclei. It is suggested that this absence of progress is due to a lack of adequate methodologies to deal with the systematic errors arising from uncertainties in the analysis of the measurements. The ENDF/B treatment of the unresolved resonance region is commented on and the authors recommend the validation of the unresolved resonance range evaluations with appropriate transmission and self-indication measurements.

Enhanced THz extinction in arrays of resonant semiconductor particles

NARCIS (Netherlands)

Schaafsma, M. C.; Georgiou, G.; J. Gomez Rivas,

2015-01-01

We demonstrate experimentally the enhanced THz extinction by periodic arrays of resonant semiconductor particles. This phenomenon is explained in terms of the radiative coupling of localized resonances with diffractive orders in the plane of the array (Rayleigh anomalies). The experimental results

Evidence for valence neutron capture in s-wave neutron capture in 38Ar and 54Fe

International Nuclear Information System (INIS)

Mughabghab, S.F.

1975-01-01

The valence and channel neutron model of Lane and Lynn remarkably account for partial radiative widths of neutron resonances in the 3p-giant resonance. Evidence is presented for valence neutron capture at and in the neighborhood of the 3s-giant resonance in target nuclei 36 Ar and 54 Fe. In addition, the variation of the correlation coefficient rho with the reduction power factor n of the γ ray energy is studied. (4 figures, 1 table) (U.S.)

Measurements of the thermal neutron cross-section and resonance integral for the 108Pd(n,γ)109Pd reaction

Science.gov (United States)

Hien, Nguyen Thi; Kim, Guinyun; Kim, Kwangsoo; Do, Nguyen Van; Khue, Pham Duc; Thanh, Kim Tien; Shin, Sung-Gyun; Cho, Moo-Hyun

2018-06-01

The thermal neutron capture cross-section (σ0) and resonance integral (I0) of the 108Pd(n,γ)109Pd reaction have been measured relative to that of the monitor reaction 197Au(n,γ)198Au. The measurements were carried out using the neutron activation with the cadmium ratio method. Both the samples and monitors were irradiated with and without cadmium cover of 0.5 mm thickness. The induced activities of the reaction products were measured with a well calibrated HPGe γ-ray detector. In order to improve the accuracy of the results, the necessary corrections for the counting losses were made. The thermal neutron capture cross-section and resonance integral of the 108Pd(n,γ)109Pd reaction were determined to be σ0,Pd = 8.68 ± 0.41 barn and I0,Pd = 245.6 ± 24.8 barn, respectively. The obtained results are compared with literature values and discussed.

Combined neutron imaging techniques for cultural heritage purpose

International Nuclear Information System (INIS)

Materna, T.

2009-01-01

This article presents the different new neutron techniques developed by the Ancient Charm collaboration to image objects of cultural heritage importance: Prompt-gamma-ray activation imaging (PGAI) coupled to cold/thermal neutron transmission tomography, Neutron Resonance Capture Imaging (NRCI) and Neutron Resonance Tomography.

Resonances in odd-odd 182Ta

Directory of Open Access Journals (Sweden)

Brits C.P.

2017-01-01

Full Text Available Enhanced γ-decay on the tail of the giant electric dipole resonance, such as the scissors or pygmy resonances, can have significant impact on (n,γ reaction rates. These rates are important input for modeling processes that take place in astrophysical environments and nuclear reactors. Recent results from the University of Oslo indicate the existence of a significant enhancement in the photon strength function for nuclei in the actinide region due to the scissors resonance. Further, the M1 strength distribution of the scissors resonances in rare earth nuclei has been studied extensively over the years. To investigate the evolution and persistence of the scissor resonance in other mass regions, an experiment was performed utilizing the NaI(Tl γ-ray detector array (CACTUS and silicon particle telescopes (SiRi at the University of Oslo Cyclotron laboratory. Particle-γ coincidences from the 181Ta(d,p182Ta and 181Ta(d,d'181Ta reactions were used to measure the nuclear level density and photon strength function of the well-deformed 181Ta and 182Ta systems, to investigate the existence of resonances below the neutron separation energy.

Novel Chiroptical Analysis of Hemoglobin by Surface Enhanced Resonance Raman Optical Activity Spectroscopy

DEFF Research Database (Denmark)

Brazhe, Nadezda; Brazhe, Alexey; Sosnovtseva, Olga

2010-01-01

The metalloprotein hemoglobin (Hb) was studied using surface enhanced resonance Raman spectroscopy (SERRS) and surface enhanced resonance Raman optical activity (SERROA). The SERROA results are analyzed and compared with the SERRS, and the later to the resonance Raman (RRS) performed on Hb...

Resonant metallic nanostructures for enhanced terahertz spectroscopy

KAUST Repository

Toma, A.; Tuccio, S.; Prato, M.; De Donato, F.; Perucchi, A.; Di Pietro, P.; Marras, S.; Liberale, Carlo; Zaccaria, R. Proietti; De Angelis, F.; Manna, L.; Lupi, S.; Di Fabrizio, Enzo M.; Razzari, L.

2015-01-01

We present our recent studies on terahertz resonant dipole nanoantennas. Exploiting the localization and enhancement capabilities of these devices, we introduce an effective method to perform terahertz spectroscopy on an extremely small number

Ideal Gas Resonance Scattering Kernel Routine for the NJOY Code

International Nuclear Information System (INIS)

Rothenstein, W.

1999-01-01

In a recent publication an expression for the temperature-dependent double-differential ideal gas scattering kernel is derived for the case of scattering cross sections that are energy dependent. Some tabulations and graphical representations of the characteristics of these kernels are presented in Ref. 2. They demonstrate the increased probability that neutron scattering by a heavy nuclide near one of its pronounced resonances will bring the neutron energy nearer to the resonance peak. This enhances upscattering, when a neutron with energy just below that of the resonance peak collides with such a nuclide. A routine for using the new kernel has now been introduced into the NJOY code. Here, its principal features are described, followed by comparisons between scattering data obtained by the new kernel, and the standard ideal gas kernel, when such comparisons are meaningful (i.e., for constant values of the scattering cross section a 0 K). The new ideal gas kernel for variable σ s 0 (E) at 0 K leads to the correct Doppler-broadened σ s T (E) at temperature T

The effect of the 238U neutron strength function uncertainty on resonance structure calculations in unresolved regions

International Nuclear Information System (INIS)

Koshcheev, V.N.; Manturov, G.N.; Sinitsa, V.V.

1991-01-01

The effects of the neutron strength function uncertainties on the calculated values of the self-shielding factors and energy dependence of the total and capture 238 U cross-sections in the unresolved resonance region are investigated. (author). 26 refs, 5 figs

High-efficiency resonant rf spin rotator with broad phase space acceptance for pulsed polarized cold neutron beams

Directory of Open Access Journals (Sweden)

P.-N. Seo

2008-08-01

Full Text Available High precision fundamental neutron physics experiments have been proposed for the intense pulsed spallation neutron beams at JSNS, LANSCE, and SNS to test the standard model and search for new physics. Certain systematic effects in some of these experiments have to be controlled at the few ppb level. The NPDGamma experiment, a search for the small parity-violating γ-ray asymmetry A_{γ} in polarized cold neutron capture on parahydrogen, is one example. For the NPDGamma experiment we developed a radio-frequency resonant spin rotator to reverse the neutron polarization in a 9.5  cm×9.5  cm pulsed cold neutron beam with high efficiency over a broad cold neutron energy range. The effect of the spin reversal by the rotator on the neutron beam phase space is compared qualitatively to rf neutron spin flippers based on adiabatic fast passage. We discuss the design of the spin rotator and describe two types of transmission-based neutron spin-flip efficiency measurements where the neutron beam was both polarized and analyzed by optically polarized ^{3}He neutron spin filters. The efficiency of the spin rotator was measured at LANSCE to be 98.8±0.5% for neutron energies from 3 to 20 meV over the full phase space of the beam. Systematic effects that the rf spin rotator introduces to the NPDGamma experiment are considered.

Neutron slowing-down time in matter

Energy Technology Data Exchange (ETDEWEB)

Chabod, Sebastien P., E-mail: sebastien.chabod@lpsc.in2p3.fr [LPSC, Universite Joseph Fourier Grenoble 1, CNRS/IN2P3, Institut Polytechnique de Grenoble, 38000 Grenoble (France)

2012-03-21

We formulate the neutron slowing-down time through elastic collisions in a homogeneous, non-absorbing, infinite medium. Our approach allows taking into account for the first time the energy dependence of the scattering cross-section as well as the energy and temporal distribution of the source neutron population in the results. Starting from this development, we investigate the specific case of the propagation in matter of a mono-energetic neutron pulse. We then quantify the perturbation on the neutron slowing-down time induced by resonances in the scattering cross-section. We show that a resonance can induce a permanent reduction of the slowing-down time, preceded by two discontinuities: a first one at the resonance peak position and an echo one, appearing later. From this study, we suggest that a temperature increase of the propagating medium in presence of large resonances could modestly accelerate the neutron moderation.

Neutron flux enhancement in the NRAD reactor

International Nuclear Information System (INIS)

Weeks, A.A.; Heidel, C.C.; Imel, G.R.

1988-01-01

In 1987 a series of experiments were conducted at the NRAD reactor facility at Argonne National Laboratory - West (ANL-W) to investigate the possibility of increasing the thermal neutron content at the end of the reactor's east beam tube through the use of hydrogenous flux traps. It was desired to increase the thermal flux for a series of experiments to be performed in the east radiography cell, in which the enhanced flux was required in a relatively small volume. Hence, it was feasible to attempt to focus the cross section of the beam to a smaller area. Two flux traps were constructed from unborated polypropylene and tested to determine their effectiveness. Both traps were open to the entire cross-sectional area of the neutron beam (as it emerges from the wall and enters the beam room). The sides then converged such that at the end of the trap the beam would be 'focused' to a greater intensity. The differences in the two flux traps were primarily in length, and hence angle to the beam as the inlet and outlet cross-sectional areas were held constant. The experiments have contributed to the design of a flux trap in which a thermal flux of nearly 10 9 was obtained, with an enhancement of 6.61

New experimental determination of the neutronic resonance parameters of {sup 237}Np below 500 eV; Nouvelle determination experimentale des parametres de resonances neutroniques de {sup 237}Np en dessous de 500 eV

Energy Technology Data Exchange (ETDEWEB)

Gressier, V

1999-10-01

For studies of future nuclear reactors dedicated to nuclear waste transmutation, an improvement of the accuracy of the neutron radiative capture cross section of {sup 237}Np appears necessary. In the framework of a collaboration between the Commissariat a l'Energie atomique (CEA) and Institute for Reference Materials and Measurement (IRMM, Geel, Bergium), a new determination of the resonance parameters of {sup 237}Np has been performed. Two types of experiments are carried out at GELINA, the IRMM pulsed neutron source, using the time of flight method: a transmission experiment which is related to the neutron total cross section and a capture experiment which gives the neutron radiative capture cross section. The resonance parameters presented in this work are extracted from the transmission data between 0 and 500 eV with the least square code REFIT, using the Reich-Moore formalism. In parallel, the Doppler effect is investigated. The commonly used free gas model appears inadequate below 20 eV for neptunium dioxide at room temperature. By the use of the program DOPUSH, which calculates the Doppler broadening with a harmonic crystal model according to Lamb's theory, we are able to produce abetter fit of the experimental data for the resonances of {sup 237}Np in NpO{sub 2} at low energy or temperatures. In addition to the resonance parameters, a study of their mean value and distribution is included in this work. (authors)

Magnetic resonance image enhancement using V-filter

International Nuclear Information System (INIS)

Yamamoto, H.; Sugita, K.; Kanzaki, N.; Johja, I.; Hiraki, Y.

1990-01-01

The purpose of this study is to present a method of boundary enhancement algorithms for magnetic resonance images using a V-filter. The boundary of the brain tumor was precisely extracted by the region segmentation techniques

Resonant metallic nanostructures for enhanced terahertz spectroscopy

KAUST Repository

Toma, A.

2015-11-12

We present our recent studies on terahertz resonant dipole nanoantennas. Exploiting the localization and enhancement capabilities of these devices, we introduce an effective method to perform terahertz spectroscopy on an extremely small number of nano-objects.

Analysis of average radiation widths of neutron resonances

International Nuclear Information System (INIS)

Malezki, H.; Popov, A.B.; Trzeciak, K.

1982-01-01

On the basis of the available data on parameters of neutron resonances average values of radiation widths (GITAsub(γ)) are calculated for a wide range of nuclei in the 50 upto 250 atomic weight range. Experimental values are compared with different variants of theoretical estimates of GITAsub(γ) which are reduced to the GITAsub(γ) dependence upon atomic weight A, excitation energy U and level density parameter a as GITAsub(γ)=CAsup(α)Usup(β)asup(γ). Besides, empirical values C, α, β, γ are selected satisfying the experimental data best of all. It is determined that the use of a=kA hypothesis leads to a sufficiently better agreement between all theoretical estimates of GITAsub(γ) and experimental values. It turned out that the estimations by Weisskopf, Bondarenko-Urin or with empirically chosen parameters give an approximately similar correspondence of calculated values GITAsub(γ)sup(p) to experimental data [ru

Neutron capture in the 1.15-keV resonance of /sup 56/Fe using Moxon-Rae detectors

International Nuclear Information System (INIS)

Corvi, F.; Bastian, C.; Wisshak, K.

1986-01-01

The capture area in the 1.15-keV neutron resonance of /sup 56/Fe was measured with Moxon-Rae detectors with converters of bismuth, bismuth-graphite, and graphite. The data were normalized to gold capture at 4.91 eV using the saturated resonance method. Two separate measurements were performed: the first with the detector axis at 120 deg with respect to the neutron beam direction and the second with the axis at 90 deg. The average of the results over the three detectors is gΓ/sub n/Γγ/sub / Γ=(64.9 + .2.4) MeV for the 120-deg run and gΓn/Γγ/Γ=(63.5 + .2.1) MeV for the 90-deg run. These values are 14 to 16% larger than the corresponding one from transmission data. No reason is found for such a discrepancy

The upgraded cold neutron triple-axis spectrometer FLEXX – enhanced capabilities by new instrumental options

Directory of Open Access Journals (Sweden)

Habicht Klaus

2015-01-01

Full Text Available The upgrade of the cold neutron triple axis spectrometer FLEXX, a work-horse instrument for inelastic neutron scattering matching the sample environment capabilities at Helmholtz-Zentrum Berlin, has been successfully accomplished. Experiments confirmed an order of magnitude gain in flux now allowing for intensity demanding options to be fully exploited at FLEXX. In this article, we describe the layout and design of two newly available FLEXX instrument options in detail. The new Heusler analyzer gives an increase of the detected polarized neutron flux due to its superior focusing properties, significantly improving the feasibility of future polarized and neutron resonance spin echo experiments. The MultiFLEXX option provides simultaneous access to large regions in wavevector and energy space for inelastic excitations thus adding mapping capabilities to the spectrometer.

Neutron flux enhancement in the NRAD reactor

International Nuclear Information System (INIS)

Weeks, A.A.; Heidel, C.C.; Imel, G.R.

1988-01-01

In 1987 a series of experiments were conducted at the NRAD reactor facility at Argonne National Laboratory - West (ANL-W) to investigate the possibility of increasing the thermal neutron content at the end of the reactor's east beam tube through the use of hydrogenous flux traps. It was desired to increase the thermal flux for a series of experiments to be performed in the east radiography cell, in which the enhanced flux was required in a relatively small volume. Hence, it was feasible to attempt to focus the cross section of the beam to a smaller area. Two flux traps were constructed from unborated polypropylene and tested to determine their effectiveness. Both traps were open to the entire cross-sectional area of the neutron beam (as it emerges from the wall and enters the beam room). The sides then converged such that at the end of the trap the beam would be 'focused' to a greater intensity. The differences in the two flux traps were primarily in length, and hence angle to the beam as the inlet and outlet cross-sectional areas were held constant. It should be noted that merely placing a slab of polypropylene in the beam will not yield significant multiplication as neutrons are primarily scattered away

Resonant cyclotron scattering in pulsar magnetospheres and its application to isolated neutron stars

International Nuclear Information System (INIS)

Tong Hao; Peng Qiuhe; Xu, Ren-Xin; Song Liming

2010-01-01

Resonant cyclotron scattering (RCS) in pulsar magnetospheres is considered. The photon diffusion equation (Kompaneets equation) for RCS is derived. The photon system is modeled three dimensionally. Numerical calculations show that there exist not only up scattering but also down scattering of RCS, depending on the parameter space. RCS's possible applications to spectral energy distributions of magnetar candidates and radio quiet isolated neutron stars (INSs) are pointed out. The optical/UV excess of INSs may be caused by the down scattering of RCS. The calculations for RX J1856.5-3754 and RX J0720.4-3125 are presented and compared with their observational data. In our model, the INSs are proposed to be normal neutron stars, although the quark star hypothesis is still possible. The low pulsation amplitude of INSs is a natural consequence in the RCS model. (letters)

Covariance Evaluation Methodology for Neutron Cross Sections

Energy Technology Data Exchange (ETDEWEB)

Herman,M.; Arcilla, R.; Mattoon, C.M.; Mughabghab, S.F.; Oblozinsky, P.; Pigni, M.; Pritychenko, b.; Songzoni, A.A.

2008-09-01

We present the NNDC-BNL methodology for estimating neutron cross section covariances in thermal, resolved resonance, unresolved resonance and fast neutron regions. The three key elements of the methodology are Atlas of Neutron Resonances, nuclear reaction code EMPIRE, and the Bayesian code implementing Kalman filter concept. The covariance data processing, visualization and distribution capabilities are integral components of the NNDC methodology. We illustrate its application on examples including relatively detailed evaluation of covariances for two individual nuclei and massive production of simple covariance estimates for 307 materials. Certain peculiarities regarding evaluation of covariances for resolved resonances and the consistency between resonance parameter uncertainties and thermal cross section uncertainties are also discussed.

Impact of the Improved Resonance Scattering Kernel on HTR Calculations

International Nuclear Information System (INIS)

Becker, B.; Dagan, R.; Broeders, C.H.M.; Lohnert, G.

2008-01-01

The importance of an advanced neutron scattering model for heavy isotopes with strong energy dependent cross sections such as the pronounced resonances of U 238 has been discussed in various publications where the full double differential scattering kernel was derived. In this study we quantify the effect of the new scattering model for specific innovative types of High Temperature Reactor (HTR) systems which commonly exhibit a higher degree of heterogeneity and higher fuel temperatures, hence increasing the importance of the secondary neutron energy distribution. In particular the impact on the multiplication factor (k ∞ ) and the Doppler reactivity coefficient is presented in view of the packing factors and operating temperatures. A considerable reduction of k ∞ (up to 600 pcm) and an increased Doppler reactivity (up to 10%) is observed. An increase of up to 2.3% of the Pu 239 inventory can be noticed at 90 MWd/tHM burnup due to enhanced neutron absorption of U 238 . Those effects are more pronounced for design cases in which the neutron flux spectrum is hardened towards the resolved resonance range. (authors)

Neutron capture resonances in 56Fe and 58Fe in the energy range from 10 to 100 keV

International Nuclear Information System (INIS)

Kaeppeler, F.; Wisshak, K.; Hong, L.D.

1982-11-01

The neutron capture cross section of 56 Fe and 58 Fe has been measured in the energy range from 10 to 250 keV relative to the gold standard. A pulsed 3 MV Van de Graaff accelerator and the 7 Li(p, n) reaction served as a neutron source. Capture gamma rays were detected by two C 6 D 6 detectors, which were operated in coincidence and anticoincidence mode. Two-dimensional data acquisition allowed to apply the pulse height weighting technique off-line. The samples were located at a flight path of 60 cm. The total time resolution was 1.2 ns thus allowing for an energy resolution of 2 ns/m. The experimental set-up was optimized with respect to low background and low neutron sensitivity. The additional flight path of 4 cm from the sample to the detector was sufficient to discriminate capture of sample scattered neutrons by the additional time of flight. In this way reliable results were obtained even for the strong s-wave resonances of both isotopes. The experimental capture yield was analyzed with the FANAC code. The energy resolution allowed to extract resonance parameters in the energy range from 10 to 100 keV. The individual systematic uncertainties of the experimental method are discussed in detail. They were found to range between 5 and 10% while the statistical uncertainty is 3-5% for most of the resonances. A comparison to the results of other authors exhibits in case of 56 Fe systematic differences of 7-11%. For 58 Fe the present results differ up to 50% from the only other measurement for this isotope. (orig.) [de

Relative measurement of the fluxes of thermal, resonant and rapid neutrons in reactor G1

International Nuclear Information System (INIS)

Carle, R.; Mazancourt, T. de

1957-01-01

We sought to determine the behavior of the thermal, resonant and rapid neutron fluxes in the multiplier-reflector transition region, in the two principal directions of the system. We have also measured the variation of these different fluxes in the body of the multiplier medium in a canal filled with graphite and in an empty canal. The results are given in the form of curves representing: - the variation of the ratio of the thermal flux to the rapid flux in axial and radial transitions - the behavior of the thermal and resonant fluxes and the variation of their ratio in the same regions. (author) [fr

Analysis of resonances due to 'S' neutrons in experiments on transmission by time-of-flight. 1. without the interference term; Analyse des resonances dues aux neutrons 'S' dans les experiences de transmission par temps de vol. 1. sans terme d'interference

Energy Technology Data Exchange (ETDEWEB)

Corge, C R [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1961-07-01

Various methods of transmission resonance analysis for 's' wave neutrons in time of flight experiments are described in this report. Only the case when the interference term can be neglected is treated in this first part. Results are given relative to a more complete partial area method and also to a new method so-called the width at half depth method. (author) [French] Le present rapport est consacre a l'expose de differentes methodes d'analyse des resonances dues aux neutrons d'ondes 's' dans les experiences de transmission par temps de vol, cette premiere partie traitant uniquement le cas ou l'on peut negliger le terme d'interference. Y figurent en particulier sous forme de reseaux de courbes, les resultats relatifs a une methode des aires partielles amelioree et ceux relatifs a une nouvelle methode dite de la largeur a mi-profondeur. (auteur)

Electron paramagnetic resonance of isolated Assub(Ga)+ antisite defect in neutron-transmutation doped semi-insulating GaAs

International Nuclear Information System (INIS)

Manasreh, M.O.; McDonald, P.F.; Kivlighn, S.A.; Minton, J.T.; Covington, B.C.

1988-01-01

The isolated Assub(Ga) antisite defect produced by the neutron-transmutation doping in semi-insulating GaAs was studied using the electron paramagnetic resonance technique. The results show that the optically induced quenching of the isolated Assub(Ga) + antisite defect is quite different from that of the EL2 center. Illumination with white light seems to always reduce the electron paramagnetic resonance spectrum suggesting that depopulation of the EL2 center does not introduce a noticeable change in the Assub(Ga) + antisite concentration. (author)

A method for solving the spherical harmonics equations applied for space-energy transport of fast and resonance neutrons

International Nuclear Information System (INIS)

Matausek, M.

1972-01-01

A new proposed method for solving the space-energy dependent spherical harmonics equations represents a methodological contribution to neutron transport theory. The proposed method was applied for solving the problem of spec-energy transport of fast and resonance neutrons in multi-zone, cylindrical y symmetric infinite reactor cell and is related to previously developed procedure for treating the thermal energy region. The advantages of this method are as follows: a unique algorithm was obtained for detailed determination of spatial and energy distribution of neutrons (from thermal to fast) in the reactor cell; these detailed distributions enable more precise calculations of criticality conditions, obtaining adequate multigroup data and better interpretation of experimental data; computing time is rather short

Gd-EOB-DTPA-enhanced magnetic resonance imaging features of hepatic hemangioma compared with enhanced computed tomography

OpenAIRE

Tateyama, Akihiro; Fukukura, Yoshihiko; Takumi, Koji; Shindo, Toshikazu; Kumagae, Yuichi; Kamimura, Kiyohisa; Nakajo, Masayuki

2012-01-01

AIM: To clarify features of hepatic hemangiomas on gadolinium-ethoxybenzyl-diethylenetriaminpentaacetic acid (Gd-EOB-DTPA)-enhanced magnetic resonance imaging (MRI) compared with enhanced computed tomography (CT).

Resonances in odd-odd 182Ta

Science.gov (United States)

Brits, C. P.; Wiedeking, M.; Bello Garrote, F. L.; Bleuel, D. L.; Giacoppo, F.; Görgen, A.; Guttormsen, M.; Hadynska-Klek, K.; Hagen, T. W.; Ingeberg, V. W.; Kheswa, B. V.; Klintefjord, M.; Larsen, A. C.; Malatji, K. L.; Nyhus, H. T.; Papka, P.; Renstrøm, T.; Rose, S.; Sahin, E.; Siem, S.; Tveten, G. M.; Zeiser, F.

2017-09-01

Enhanced γ-decay on the tail of the giant electric dipole resonance, such as the scissors or pygmy resonances, can have significant impact on (n,γ) reaction rates. These rates are important input for modeling processes that take place in astrophysical environments and nuclear reactors. Recent results from the University of Oslo indicate the existence of a significant enhancement in the photon strength function for nuclei in the actinide region due to the scissors resonance. Further, the M1 strength distribution of the scissors resonances in rare earth nuclei has been studied extensively over the years. To investigate the evolution and persistence of the scissor resonance in other mass regions, an experiment was performed utilizing the NaI(Tl) γ-ray detector array (CACTUS) and silicon particle telescopes (SiRi) at the University of Oslo Cyclotron laboratory. Particle-γ coincidences from the 181Ta(d,p)182Ta and 181Ta(d,d')181Ta reactions were used to measure the nuclear level density and photon strength function of the well-deformed 181Ta and 182Ta systems, to investigate the existence of resonances below the neutron separation energy. Note to the reader: the title of this article has been corrected on September 19, 2017.

Robust upward dispersion of the neutron spin resonance in the heavy fermion superconductor Ce1−xYbxCoIn5

Science.gov (United States)

Song, Yu; Van Dyke, John; Lum, I. K.; White, B. D.; Jang, Sooyoung; Yazici, Duygu; Shu, L.; Schneidewind, A.; Čermák, Petr; Qiu, Y.; Maple, M. B.; Morr, Dirk K.; Dai, Pengcheng

2016-01-01

The neutron spin resonance is a collective magnetic excitation that appears in the unconventional copper oxide, iron pnictide and heavy fermion superconductors. Although the resonance is commonly associated with a spin-exciton due to the d(s±)-wave symmetry of the superconducting order parameter, it has also been proposed to be a magnon-like excitation appearing in the superconducting state. Here we use inelastic neutron scattering to demonstrate that the resonance in the heavy fermion superconductor Ce1−xYbxCoIn5 with x=0, 0.05 and 0.3 has a ring-like upward dispersion that is robust against Yb-doping. By comparing our experimental data with a random phase approximation calculation using the electronic structure and the momentum dependence of the -wave superconducting gap determined from scanning tunnelling microscopy (STM) for CeCoIn5, we conclude that the robust upward-dispersing resonance mode in Ce1−xYbxCoIn5 is inconsistent with the downward dispersion predicted within the spin-exciton scenario. PMID:27677397

Neutron capture widths of s-wave resonances in 56Fe, 5860Ni and 27Al

International Nuclear Information System (INIS)

Wisshak, K.; Kaeppeler, F.; Reffo, G.; Fabbri, F.

1982-01-01

The neutron capture widths of s-wave resonances in 56 Fe (27.7 keV), 58 Ni (15.4 keV), 60 Ni (12.5 keV) and 27 Al (35.3 keV) have been determined, using a setup completely different from LINAC experiments. A pulsed 3 MV Van de Graaff accelerator and the 7 Li(p,n) reaction served as a neutron source. The proton energy was adjusted just above the reaction threshold to obtain a kinematically collimated neutron beam. This allowed to position the samples at a flight path as short as approx. 90 mm. Capture events were detected by three Moxon-Rae detectors with graphite, bismuth-graphite and pure bismuth converter, respectively. The measurements were performed relative to a gold standard. The setup allows to discriminate capture of scattered neutrons completely by time of flight and to use very thin samples (0.15 mm) in order to reduce multiple scattering. After correction for deviations of the detector efficiency from a linear increase with gamma-ray energy, the results obtained with different detectors agree within their remaining systematic uncertainty of approx. 5%. Only preliminary results are presented

Resonance Enhanced Multi-photon Spectroscopy of DNA

Science.gov (United States)

Ligare, Marshall Robert

For over 50 years DNA has been studied to better understand its connection to life and evolution. These past experiments have led to our understanding of its structure and function in the biological environment but the interaction of DNA with UV radiation at the molecular level is still not very well understood. Unique mechanisms in nucleobase chromaphores protect us from adverse chemical reactions after UV absorption. Studying these processes can help develop theories for prebiotic chemistry and the possibility of alternative forms of DNA. Using resonance enhanced multi-photon spectroscopic techniques in the gas phase allow for the structure and dynamics of individual nucleobases to be studied in detail. Experiments studying different levels of structure/complexity with relation to their biological function are presented. Resonant IR multiphoton dissociation spectroscopy in conjunction with molecular mechanics and DFT calculations are used to determine gas phase structures of anionic nucleotide clusters. A comparison of the identified structures with known biological function shows how the hydrogen bonding of the nucleotides and their clusters free of solvent create favorable structures for quick incorporation into enzymes such as DNA polymerase. Resonance enhanced multi-photon ionization (REMPI) spectroscopy techniques such as resonant two photon ionization (R2PI) and IR-UV double resonance are used to further elucidate the structure and excited state dynamics of the bare nucleobases thymine and uracil. Both exhibit long lived excited electronic states that have been implicated in DNA photolesions which can ultimately lead to melanoma and carcinoma. Our experimental data in comparison with many quantum chemical calculations suggest a new picture for the dynamics of thymine and uracil in the gas phase. A high probability of UV absorption from a vibrationally hot ground state to the excited electronic state shows that the stability of thymine and uracil comes from

Neutron radiation capture

International Nuclear Information System (INIS)

1986-01-01

For all stable and experimentally studied radionuclides evaluated data are presented on cross sections of thermal neutrons, on resonance integrals and medium neutron cross sections with energy of 30 KeV. Refs, figs and tabs

Analytical approximations for wide and narrow resonances

International Nuclear Information System (INIS)

Suster, Luis Carlos; Martinez, Aquilino Senra; Silva, Fernando Carvalho da

2005-01-01

This paper aims at developing analytical expressions for the adjoint neutron spectrum in the resonance energy region, taking into account both narrow and wide resonance approximations, in order to reduce the numerical computations involved. These analytical expressions, besides reducing computing time, are very simple from a mathematical point of view. The results obtained with this analytical formulation were compared to a reference solution obtained with a numerical method previously developed to solve the neutron balance adjoint equations. Narrow and wide resonances of U 238 were treated and the analytical procedure gave satisfactory results as compared with the reference solution, for the resonance energy range. The adjoint neutron spectrum is useful to determine the neutron resonance absorption, so that multigroup adjoint cross sections used by the adjoint diffusion equation can be obtained. (author)

Analytical approximations for wide and narrow resonances

Energy Technology Data Exchange (ETDEWEB)

Suster, Luis Carlos; Martinez, Aquilino Senra; Silva, Fernando Carvalho da [Universidade Federal, Rio de Janeiro, RJ (Brazil). Coordenacao dos Programas de Pos-graduacao de Engenharia. Programa de Engenharia Nuclear]. E-mail: aquilino@lmp.ufrj.br

2005-07-01

This paper aims at developing analytical expressions for the adjoint neutron spectrum in the resonance energy region, taking into account both narrow and wide resonance approximations, in order to reduce the numerical computations involved. These analytical expressions, besides reducing computing time, are very simple from a mathematical point of view. The results obtained with this analytical formulation were compared to a reference solution obtained with a numerical method previously developed to solve the neutron balance adjoint equations. Narrow and wide resonances of U{sup 238} were treated and the analytical procedure gave satisfactory results as compared with the reference solution, for the resonance energy range. The adjoint neutron spectrum is useful to determine the neutron resonance absorption, so that multigroup adjoint cross sections used by the adjoint diffusion equation can be obtained. (author)

A Resonant Scanning Dipole-Antenna Probe for Enhanced Nanoscale Imaging

NARCIS (Netherlands)

Neumann, L.; van 't Oever, Jan Joannes Frederik; van Hulst, N.F.

2013-01-01

We present a scanning antenna probe that provides 35 nm optical hotspots with a 16-fold excitation enhancement. A resonant optical antenna, tuned to operation in the visible, is carved into the aluminum-coated scanning probe. The antenna resonances, field localization, excitation, and polarization

Effect of large neutron excess in the region of the Giant Dipole and Quadrupole Resonance

CERN Document Server

Lanza, E G

1999-01-01

We study the dipole and quadrupole modes of neutron rich nuclei within the selfconsistent HF + RPA. The presence of neutron skin enhances the mixing of isoscalar and isovector modes. Then it is possible to excite modes of isovector character by an isoscalar probe. In particular we analize the excitation of dipole modes by alpha scattering. The excitation of compressional isoscalar mode is also studied.

Approximation for the adjoint neutron spectrum; Aproximacao para o espectro adjunto de neutrons

Energy Technology Data Exchange (ETDEWEB)

Suster, Luis Carlos; Martinez, Aquilino Senra; Silva, Fernando Carvalho da [Universidade Federal, Rio de Janeiro, RJ (Brazil). Coordenacao dos Programas de Pos-graduacao de Engenharia. Programa de Engenharia Nuclear

2002-07-01

The proposal of this work is the determination of an analytical approximation which is capable to reproduce the adjoint neutron flux for the energy range of the narrow resonances (NR). In a previous work we developed a method for the calculation of the adjoint spectrum which was calculated from the adjoint neutron balance equations, that were obtained by the collision probabilities method, this method involved a considerable quantity of numerical calculation. In the analytical method some approximations were done, like the multiplication of the escape probability in the fuel by the adjoint flux in the moderator, and after these approximations, taking into account the case of the narrow resonances, were substituted in the adjoint neutron balance equation for the fuel, resulting in an analytical approximation for the adjoint flux. The results obtained in this work were compared to the results generated with the reference method, which demonstrated a good and precise results for the adjoint neutron flux for the narrow resonances. (author)

The choice of the optimum terms for semi-empirical description of s-wave neutron resonance level densities

Energy Technology Data Exchange (ETDEWEB)

Kaczmarczyk, Maria; Lason, Lech [Division of Nuclear Physics, University of Lodz, ul Pomorska 149/153, 90-236 Lodz (Poland)

2006-04-01

This paper presents a function describing the dependence of the neutron resonance level density {rho} on the neutron number N in the target nucleus. The function describes quite well, with an accuracy of one order, the experimental data for 284 nuclides. Moreover, it adequately describes the general tendency and shell model effects for magic nuclei and for nuclei close to magic ones. The achieved agreement between the values obtained from the proposed description and the experimental data {rho}{sub exp} can be improved if the {rho}{sub exp} values are normalized energetically and reduced to a narrow range of angular momentum J.

Thermal neutron capture cross-section and resonance integral measurements of {sup 139}La(n, γ){sup 140}La and {sup 140}Ce(n, γ){sup 141}Ce using a Am-Be neutron source

Energy Technology Data Exchange (ETDEWEB)

Panikkath, Priyada; Mohanakrishnan, P. [Manipal University, Manipal Centre for Natural Sciences, Karnataka (India)

2017-03-15

Thermal neutron capture cross-sections and resonance integrals of {sup 139}La(n, γ){sup 140}La and {sup 140}Ce (n, γ){sup 141}Ce are measured with respect to reference reactions {sup 197}Au(n, γ){sup 198}Au and {sup 55}Mn(n, γ){sup 56}Mn using the neutron activation technique. Measurements are carried out using neutrons from an Am-Be source located inside a concrete bunker. Two different methods are used for determining self-shielding factors of activation foils as well as for finding the epithermal neutron spectrum shape factor. For {sup 139}La with reference to {sup 197}Au and {sup 55}Mn the measured thermal cross sections are 9.24 ± 0.25 b and 9.28 ± 0.37 b, respectively, while the measured resonance integrals are 12.18 ± 0.67 b and 11.81 ± 0.94 b, respectively. For {sup 140}Ce with reference to {sup 197}Au and {sup 55}Mn the measured thermal cross sections are 0.44 ± 0.01 b and 0.44 ± 0.02 b, respectively, while the measured resonance integrals are 0.55 ± 0.03 b and 0.54 ± 0.04 b, respectively. The present measurements are compared with earlier measurements and evaluations. Presently estimated values confirm the established {sup 139}La(n, γ){sup 140}La cross-sections. The presently measured thermal capture cross-section {sup 140}Ce(n, γ){sup 141}Ce, though lower than the evaluated data, is having higher accuracy compared to previous measurements with large uncertainties. The resonance integral measured is higher (like most previous measurements) than most evaluations requiring a revision of the evaluated data. (orig.)

Oxygen enhancement ratio (OER) to Neutron and Co-60 γ ray

International Nuclear Information System (INIS)

Kim, Mi Sook; Ji, Young Hoon; Lee, Yong Min; Kim Kyeoung Jung

1997-01-01

Experiments in vitro, using human cell lines was carried out in order to establish whether or not there was a difference between oxygen enhancement ratio (OER) of neutron and Co-60 γ-ray and to determine OER dependence on radiation dose. MG-63 cell line and H-460 cell line were defined as the most sensitive cell line to neutron among our laboratory holding cell lines through preliminary study. Anoxia as was produced in glove box. The box was flushed for one hour with a mixture of 5 % CO 2 in ultrapure N 2 (total oxygen concentration < 10 ppm) and irradiated with neutron and Co-60 γ-ray. Oxic condition was same as anoxic condition except being irradiated in general air condition. The lower OER was observed in neutron than in Co-60 γ-ray. The dose dependence of OER was observed in neutron and Co-60 γ-ray all. But the dose dependence of the OER is somewhat larger for Co-60 γ-ray than for neutron. In the range of 1 to 8 Gy, the OER for photon and neutron range from 1.54 to 1.94 and 1.23 to 1.26 in MG-63 cell line. In case of H-460 the OER for Co-60 γ-ray and neutron range from 1.24 to 1.60 and 1.06 to 1.07 respectively. (author). 19 refs., 5 tabs., 5 figs

Characterization of the enhancing lesions on dynamic contrast enhanced magnetic resonance imaging in patients with interstitial mammoplasty

International Nuclear Information System (INIS)

Kim, Tae Yun; Kim, Sung Hun; Kang, Bong Joo; Kim, Hyeon Sook; Cha, Eun Suk; Kim, Ji Youn; Song, Byung Joo

2013-01-01

Purpose: The purpose of this study was to categorize the morphologic and kinetic features of enhancing lesions in breasts with interstitial mammoplasty using dynamic contrast-enhanced magnetic resonance imaging and to assess factors predictive of breast cancer. Materials and methods: We retrospectively reviewed the clinical and radiological data of 21 enhancing lesions in 19 patients with interstitial mammoplasty, who underwent breast magnetic resonance imaging and biopsy or an operation in our hospital from September 2008 to July 2012. These lesions were sorted by morphological and kinetic features and final assessment category according to the BI-RADS lexicon. Results: Nine cases were confirmed to be ductal carcinoma in situ (n = 2) and invasive ductal carcinoma (n = 7), and the remaining 12 cases were fibrocystic disease (n = 2), fibroadenoma (n = 2), fat necrosis (n = 1), foreign body granuloma (n = 3) and silicone mastitis (n = 1). Common features of malignancy included irregular shape (50.0%), spiculated margins (75.0%), heterogeneous enhancement (50.0%) and type III kinetic pattern (87.5%). The correlations of margins and kinetic curve pattern with benignity and malignancy approached statistical significance (p = 0.02, respectively). We found no correlation for shape (p = 0.33) or internal enhancement (p = 0.42) between lesion types. The malignancy rate of enhancing lesions was 42.8% (9/21). The sensitivity and specificity of dynamic contrast-enhanced magnetic resonance imaging were 100% and 16.67%, respectively. The positive predictive value, negative predictive value and accuracy of magnetic resonance imaging were 47.38%, 100% and 52.38%. Overall inter-observer agreement for the kinetic curve pattern was good (κ = 0.67). Moderate agreement was seen in describing the shape, margin, enhancement and assessing the final category (κ = 0.59, 0.46, 0.58 and 0.49, respectively). Conclusion: Dynamic contrast-enhanced magnetic resonance imaging had a high

Characterization of the enhancing lesions on dynamic contrast enhanced magnetic resonance imaging in patients with interstitial mammoplasty

Energy Technology Data Exchange (ETDEWEB)

Kim, Tae Yun [Department of Radiology, Seoul St. Mary' s Hospital, The Catholic University of Korea (Korea, Republic of); Kim, Sung Hun, E-mail: rad-ksh@catholic.ac.kr [Department of Radiology, Seoul St. Mary' s Hospital, The Catholic University of Korea (Korea, Republic of); Kang, Bong Joo [Department of Radiology, Seoul St. Mary' s Hospital, The Catholic University of Korea (Korea, Republic of); Kim, Hyeon Sook [Department of Radiology, St. Paul Hospital, The Catholic University of Korea (Korea, Republic of); Cha, Eun Suk [Department of Radiology, Ewha Womans University, School of Medicine, Mokdong Hospital (Korea, Republic of); Kim, Ji Youn [Department of Radiology, Yeouido St. Mary' s Hospital, The Catholic University of Korea (Korea, Republic of); Song, Byung Joo [Department of Surgery, Seoul St. Mary' s Hospital, The Catholic University of Korea, Seoul (Korea, Republic of)

2013-12-01

Purpose: The purpose of this study was to categorize the morphologic and kinetic features of enhancing lesions in breasts with interstitial mammoplasty using dynamic contrast-enhanced magnetic resonance imaging and to assess factors predictive of breast cancer. Materials and methods: We retrospectively reviewed the clinical and radiological data of 21 enhancing lesions in 19 patients with interstitial mammoplasty, who underwent breast magnetic resonance imaging and biopsy or an operation in our hospital from September 2008 to July 2012. These lesions were sorted by morphological and kinetic features and final assessment category according to the BI-RADS lexicon. Results: Nine cases were confirmed to be ductal carcinoma in situ (n = 2) and invasive ductal carcinoma (n = 7), and the remaining 12 cases were fibrocystic disease (n = 2), fibroadenoma (n = 2), fat necrosis (n = 1), foreign body granuloma (n = 3) and silicone mastitis (n = 1). Common features of malignancy included irregular shape (50.0%), spiculated margins (75.0%), heterogeneous enhancement (50.0%) and type III kinetic pattern (87.5%). The correlations of margins and kinetic curve pattern with benignity and malignancy approached statistical significance (p = 0.02, respectively). We found no correlation for shape (p = 0.33) or internal enhancement (p = 0.42) between lesion types. The malignancy rate of enhancing lesions was 42.8% (9/21). The sensitivity and specificity of dynamic contrast-enhanced magnetic resonance imaging were 100% and 16.67%, respectively. The positive predictive value, negative predictive value and accuracy of magnetic resonance imaging were 47.38%, 100% and 52.38%. Overall inter-observer agreement for the kinetic curve pattern was good (κ = 0.67). Moderate agreement was seen in describing the shape, margin, enhancement and assessing the final category (κ = 0.59, 0.46, 0.58 and 0.49, respectively). Conclusion: Dynamic contrast-enhanced magnetic resonance imaging had a high

Study of the neutron slowing-down in graphite; Etude du ralentissement des neutrons dans le graphite

Energy Technology Data Exchange (ETDEWEB)

Martelly, J [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires; Duggal, V P [Commission a l' Energie atomique indienne (India)

1955-07-01

Study of the slowing-down age of neutrons in graphite. In the aim to eliminate the effect of resonance neutrons on the detector, neutrons captured by cadmium are studied with a classic method consisting of calculating the difference between the activity measured with and without screens. This method is described and screening properties of cadmium and gadolinium are compared. The experimental parameters and detectors details are described. The radioactive source is Ra-{alpha}-Be. The experimental results are given and the experimental distribution is compared with theoretical formula. In a second part, the spatial distribution of resonance neutrons in indium is discussed. Finally, the neutron slowing-down between the indium resonance and the thermal equilibrium is discussed as well as the research for the effective value of slowing-down age. The slowing-down age definition is given before calculating its effective value. It compared the slowing-down law with the experiment and the Gurney theory. (M.P.)

New experimental determination of the neutron resonance parameters of {sup 99}Tc; Nouvelle determination experimentale des parametres de resonances neutroniques de {sup 99}Tc

Energy Technology Data Exchange (ETDEWEB)

Brienne-Raepsaet, C. [CEA Bruyeres-le-Chatel, 91 (France). Dept. de Physique Theorique et Appliquee]|[Aix-Marseille-1 Univ., 13 - Marseille (France)

1999-04-01

In order to improve nuclear data for nuclear waste transmutation cross-sections of Tc{sup 99} in the resonance energy region have been performed using the time-of-flight method at the pulsed white neutron source GELINA of the Institute for Reference Materials and Measurements, Geel, Belgium. The energy range studied spreads from 3 eV to 100 KeV. 2 kinds of measurements have been performed: capture and transmission measurements. In the energy range between 0 and 2 KeV, more than 220 resonances have been analyzed. About 130 resonances which had stayed previously undiscovered, have been detected and analyzed. Because of instability problems concerning the process of measuring itself, the systematic error is not yet determined. The accuracy which takes into account statistical and systematic errors is expected to be between 4 and 5%.

Enhancement of four-wave mixing induced by interacting dark resonances

International Nuclear Information System (INIS)

Yang Weifeng; Gong Shangqing; Niu Yueping; Jin Shiqi; Xu Zhizhan

2005-01-01

We analyse a four-wave mixing (FWM) scheme in a five-level atomic system in which double-dark resonances are present. It is found that the enhancement of FWM in both electromagnetically induced transparency (EIT) windows can be obtained even without the condition of multiphoton resonance. Moreover, the conversion efficiency of FWM in one EIT window can be much larger than that in the other due to the presence of interacting dark resonances

Surface plasmon enhanced interfacial electron transfer and resonance Raman, surface-enhanced resonance Raman studies of cytochrome C mutants

Energy Technology Data Exchange (ETDEWEB)

Zheng, Junwei [Iowa State Univ., Ames, IA (United States)

1999-11-08

Surface plasmon resonance was utilized to enhance the electron transfer at silver/solution interfaces. Photoelectrochemical reductions of nitrite, nitrate, and CO₂ were studied on electrochemically roughened silver electrode surfaces. The dependence of the photocurrent on photon energy, applied potential and concentration of nitrite demonstrates that the photoelectrochemical reduction proceeds via photoemission process followed by the capture of hydrated electrons. The excitation of plasmon resonances in nanosized metal structures resulted in the enhancement of the photoemission process. In the case of photoelectrocatalytic reduction of CO₂, large photoelectrocatalytic effect for the reduction of CO₂ was observed in the presence of surface adsorbed methylviologen, which functions as a mediator for the photoexcited electron transfer from silver metal to CO₂ in solution. Photoinduced reduction of microperoxidase-11 adsorbed on roughened silver electrode was also observed and attributed to the direct photoejection of free electrons of silver metal. Surface plasmon assisted electron transfer at nanostructured silver particle surfaces was further determined by EPR method.

Enhanced Faraday rotation in one dimensional magneto-plasmonic structure due to Fano resonance

Science.gov (United States)

Sadeghi, S.; Hamidi, S. M.

2018-04-01

Enhanced Faraday rotation in a new type of magneto-plasmonic structure with the capability of Fano resonance, has been reported theoretically. A magneto-plasmonic structure composed of a gold corrugated layer deposited on a magneto-optically active layer was studied by means of Lumerical software based on finite-difference time-domain. In our proposed structure, plasmonic Fano resonance and localized surface plasmon have induced enhancement in magneto-optical Faraday rotation. It is shown that the influence of geometrical parameters in gold layer offers a desirable platform for engineering spectral position of Fano resonance and enhancement of Faraday rotation.

Enhancing optical response of graphene through stochastic resonance

Science.gov (United States)

Ying, Lei; Huang, Liang; Lai, Ying-Cheng

2018-04-01

Enhancing the optical response of graphene is a topic of interest with applications in optoelectronics. Subject to light irradiation, graphene can exhibit nontrivial topologically insulating states, effectively turning itself into a Floquet topological insulator due to the time periodicity of the external driving. We find that, when random disorder is present, its interplay with the topologically insulating states can have a dramatic effect on electronic transport through graphene. In particular, we consider the prototypical setting where a graphene nanoribbon is irradiated by circularly polarized light, where the length of the nanoribbon is sufficiently long so that evanescent states have little effect on transport. We uncover a resonance phenomenon in which the conductance is enhanced as the disorder strength is increased from zero, reaches a maximum value for an optimal level of disorder, and decreases as the disorder is strengthened further. With respect to its value at the zero-disorder strength, the maximum conductance value can be as much as 50 % higher. Qualitatively, this can be understood as a result of the dynamical interplay between disorder and Floquet states (channels) generated by light irradiation. Quantitatively, the resonance phenomenon can be explained in the framework of Born theory, where the disorder reorganizes the Floquet Hamiltonian and enhances the effective coupling between the adjacent Floquet conducting channels. That is, disorder is capable of promoting both photon absorption and emission, leading to significant enhancement of nonequilibrium electronic transport. We demonstrate the robustness of the resonance phenomenon by investigating the effects of spatial symmetry breaking on transport and provide an understanding based on analyzing the behavior of the density of states of the Floquet channels.

Analysis methods of neutrons induced resonances in the transmission experiments by time-of-flight and automation of these methods on IBM 7094 II computer; Methode d'analyse des resonances induites par les neutrons dans les experiences de transmission par temps-de-vol et automatisation de ces methodes sur ordinateur IBM-7094 II

Energy Technology Data Exchange (ETDEWEB)

Corge, C

1967-07-01

The neutron induced resonances analysis aims to determine the neutrons characteristics, leading to the excitation energies, de-excitation probabilities by gamma radiation emission, by neutron emission or by fission, their spin, their parity... This document describes the methods developed, or adapted, the calculation schemes and the algorithms implemented to realize such analysis on a computer, from data obtained during time-of-flight experiments on the linear accelerator of Saclay. (A.L.B.)

Analysis methods of neutrons induced resonances in the transmission experiments by time-of-flight and automation of these methods on IBM 7094 II computer; Methode d'analyse des resonances induites par les neutrons dans les experiences de transmission par temps-de-vol et automatisation de ces methodes sur ordinateur IBM-7094 II

Energy Technology Data Exchange (ETDEWEB)

Corge, C

1967-07-01

The neutron induced resonances analysis aims to determine the neutrons characteristics, leading to the excitation energies, de-excitation probabilities by gamma radiation emission, by neutron emission or by fission, their spin, their parity... This document describes the methods developed, or adapted, the calculation schemes and the algorithms implemented to realize such analysis on a computer, from data obtained during time-of-flight experiments on the linear accelerator of Saclay. (A.L.B.)

Surface-Enhanced Raman Scattering Using Silica Whispering-Gallery Mode Resonators

Science.gov (United States)

Anderson, Mark S.

2013-01-01

The motivation of this work was to have robust spectroscopic sensors for sensitive detection and chemical analysis of organic and molecular compounds. The solution is to use silica sphere optical resonators to provide surface-enhanced spectroscopic signal. Whispering-gallery mode (WGM) resonators made from silica microspheres were used for surface-enhanced Raman scattering (SERS) without coupling to a plasmonic mechanism. Large Raman signal enhancement is observed by exclusively using 5.08-micron silica spheres with 785-nm laser excitation. The advantage of this non-plasmonic approach is that the active substrate is chemically inert silica, thermally stable, and relatively simple to fabricate. The Raman signal enhancement is broadly applicable to a wide range of molecular functional groups including aliphatic hydrocarbons, siloxanes, and esters. Applications include trace organic analysis, particularly for in situ planetary instruments that require robust sensors with consistent response.

Measurement of thermal neutron cross-sections and resonance integrals for sup 7 sup 1 Ga(n,gamma) sup 7 sup 2 Ga and sup 7 sup 5 As(n,gamma) sup 7 sup 6 As by using sup 2 sup 4 sup 1 Am-Be isotopic neutron source

CERN Document Server

Karadag, M; Tan, M; Oezmen, A

2003-01-01

Thermal neutron cross-sections and resonance integrals for the sup 7 sup 1 Ga(n,gamma) sup 7 sup 2 Ga and sup 7 sup 5 As(n,gamma) sup 7 sup 6 As reactions were measured by the activation method. The experimental samples with and without a cylindrical Cd shield case in 1 mm wall thickness were irradiated in an isotropic neutron field of the sup 2 sup 4 sup 1 Am-Be neutron source. The induced activities in the samples were measured by high-resolution gamma-ray spectrometry with a calibrated reverse-electrode germanium detector. Thermal neutron cross-sections for 2200 m/s neutrons and resonance integrals for the sup 7 sup 1 Ga(n,gamma) sup 7 sup 2 Ga and sup 7 sup 5 As(n,gamma) sup 7 sup 6 As reactions have been obtained relative to the reference values, sigma sub 0 =13.3+-0.1 b and I sub 0 =14.0+-0.3 b for the sup 5 sup 5 Mn(n,gamma) sup 5 sup 6 Mn reaction as a single comparator. The necessary correction factors for gamma attenuation, thermal neutron and resonance neutron self-shielding effects were taken into...

Analysis of neutron data in the resonance region via the computer code SAMMY

International Nuclear Information System (INIS)

Larson, N.M.

1985-01-01

Procedures for analysis of resonance neutron cross-section data have been implemented in a state-of-the-art computer code SAMMY, developed at the Oak Ridge Electron Linear Accelerator (ORELA) at Oak Ridge National Laboratory. A unique feature of SAMMY is the use of Bayes' equations to determine ''best'' values of parameters, which permits sequential analysis of data sets (or subsets) while giving the same results as would be given by a simultaneous analysis. Another important feature is the inclusion of data-reduction parameters in the fitting procedure. Other features of SAMMY are also described

Numerical analysis of resonances induced by s wave neutrons in transmission time-of-flight experiments with a computer IBM 7094 II; Methodes d'analyse des resonances induites par les neutrons s dans les experiences de transmission par temps de vol et automatisation de ces methodes sur ordinateur IBM 7094 II

Energy Technology Data Exchange (ETDEWEB)

Corge, Ch [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1969-01-01

Numerical analysis of transmission resonances induced by s wave neutrons in time-of-flight experiments can be achieved in a fairly automatic way on an IBM 7094/II computer. The involved computations are carried out following a four step scheme: 1 - experimental raw data are processed to obtain the resonant transmissions, 2 - values of experimental quantities for each resonance are derived from the above transmissions, 3 - resonance parameters are determined using a least square method to solve the over determined system obtained by equalling theoretical functions to the correspondent experimental values. Four analysis methods are gathered in the same code, 4 - graphical control of the results is performed. (author) [French] L'automatisation, sur ordinateur IBM 7094/II, de l'analyse des resonances induites par les neutrons s dans les experiences de transmission par temps de vol a ete accomplie en la decomposant selon un schema articule en quatre phases: 1 - le traitement des donnees experimentales brutes pour obtenir les transmissions interfero-resonnantes, 2 - la determination des grandeurs d'analyse a partir des transmissions precedentes, 3 - l'analyse proprement dite des resonances dont les parametres sont obtenus par la resolution d'un systeme surabondant. Quatre methodes d'analyse sont groupees en un meme programme, 4 - la procedure de verification graphique. (auteur)

Analysis methods of neutrons induced resonances in the transmission experiments by time-of-flight and automation of these methods on IBM 7094 II computer

International Nuclear Information System (INIS)

Corge, C.

1967-01-01

The neutron induced resonances analysis aims to determine the neutrons characteristics, leading to the excitation energies, de-excitation probabilities by gamma radiation emission, by neutron emission or by fission, their spin, their parity... This document describes the methods developed, or adapted, the calculation schemes and the algorithms implemented to realize such analysis on a computer, from data obtained during time-of-flight experiments on the linear accelerator of Saclay. (A.L.B.)

Observation of low-lying resonances in the quasicontinuum of 195,196Pt and enhanced astrophysical reaction rates

Directory of Open Access Journals (Sweden)

Giacoppo F.

2015-01-01

Full Text Available An excess of strength on the low-energy tail of the giant dipole resonance recently has been observed in the γ-decay from the quasicontinuum of 195,196Pt. The nature of this phenomenon is not yet fully investigated. If this feature is present also in the γ-ray strength of the neutron-rich isotopes, it can affect the neutron-capture reactions involved in the formation of heavy-elements in stellar nucleosynthesis. The experimental level density and γ-ray strength function of 195,196Pt are presented together with preliminary calculations of the corresponding neutron-capture cross sections.

The LIPAR-5 resonance parameter library

International Nuclear Information System (INIS)

Abagyan, L.P.

1997-08-01

The LIPAR-5 neutron resolved resonance parameter library has been elaborated. It contains data for 94 isotopes. The author's evaluations are included in LIPAR. Other authors' results are also included after re-evaluation. The codes used for the evaluation are described briefly. Tables of results are included for every isotope: the boundaries of the resolved resonance region, the numbers of s- and p-resonances, the thermal neutron partial cross-sections and the resonance integrals. The parameters are presented in ENDF/B-6 format. LIPAR is part of the nuclear data library of the MCU Monte Carlo code for neutron transport calculations. LIPAR was verified by comparing the benchmark experiment and Monte Carlo calculation results. (author). 44 refs, 6 tabs

Direct observation of effective temperature of Ta atom in layer compound TaS2 by neutron resonance absorption spectrometer

International Nuclear Information System (INIS)

Tokuda, Koji; Kamiyama, Takashi; Kiyanagi, Yoshiaki; Moreh, R.; Ikeda, Susumu

2001-01-01

A neutron resonance absorption spectrometer, DOG has been installed at KENS, High Energy Accelerator Research Organization Neutron Source, which enables us to investigate the motions of a particular element by analyzing the line width of resonance absorption spectrum. We measured the temperature dependence of the effective temperature of Ta motion in TaS 2 as well as in Ta metal using DOG. The effective temperatures extracted from the observed absorption spectrum agree well with the calculated values from the phonon density of states of Ta metal over a wide temperature range of 10 to 300 K. We also succeeded in measuring both the angular dependence and the temperature dependence of effective temperatures of Ta in a layer compound TaS 2 . Based on the temperature dependence of the effective temperature, the partial phonon density of states of Ta in TaS 2 was discussed. (author)

Measurement of the 3He Spin Structure Functions in the Resonance Region: A Test of Quark-Hadron Duality on the Neutron

International Nuclear Information System (INIS)

Patricia Solvignon

2006-01-01

One of the biggest challenges in the study of the nucleon structure is the understanding of the transition from partonic degrees of freedom to hadronic degrees of freedom. In 1970, Bloom and Gilman noticed that structure function data taken at SLAC in the resonance region average to the scaling curve of deep inelastic scattering (DIS). Early theoretical interpretations suggested that these two very different regimes can be linked under the condition that the quark-gluon and quark-quark interactions are suppressed. Substantial efforts are ongoing to investigate this phenomenon both experimentally and theoretically. Quark-hadron duality has been confirmed for the unpolarized structure function F 2 of the proton and the deuteron using data from the experimental Hall C at Jefferson Lab (JLab). Indications of duality have been seen for the proton polarized structure function g 1 and the virtual photon asymmetry A 1 at JLab Hall B and HERMES. Because of the different resonance behavior, it is expected that the onset of duality for the neutron will happen at lower momentum transfer than for the proton. Now that precise spin structure data in the DIS region are available at large x, data in the resonance region are greatly needed in order to test duality in spin-dependent structure functions. The goal of experiment E01-012 was to provide such data on the neutron ( 3 He) in the moderate momentum transfer (Q 2 ) region, 1.0 2 2 ), where duality is expected to hold. The experiment ran successfully in early 2003 at Jefferson Lab in Hall B. It was an inclusive measurement of longitudinally polarized electrons scattering from a longitudinally or transversely polarized 3 He target. Asymmetries and cross section differences were measured in order to extract the 3 He spin structure function g 1 and virtual photon asymmetry A 1 in the resonance region. A test of quark-hadron duality has then been performed for the 3 He and neutron structure functions. The study of spin duality for

Comparison of neutron and gamma irradiation effects on KU1 fused silica monitored by electron paramagnetic resonance

Energy Technology Data Exchange (ETDEWEB)

Bravo, D. [Department Fisica de Materiales, Universidad Autonoma de Madrid, E-28049 Madrid (Spain)], E-mail: david.bravo@uam.es; Lagomacini, J.C. [Department Fisica de Materiales, Universidad Autonoma de Madrid, E-28049 Madrid (Spain); Leon, M.; Martin, P. [Materiales para Fusion, CIEMAT, Avda. Complutense 22, E-28040 Madrid (Spain); Martin, A. [Department Fisica e Instalaciones, ETS Arquitectura UPM, E-28040 Madrid (Spain); Lopez, F.J. [Department Fisica de Materiales, Universidad Autonoma de Madrid, E-28049 Madrid (Spain); Ibarra, A. [Materiales para Fusion, CIEMAT, Avda. Complutense 22, E-28040 Madrid (Spain)

2009-06-15

Electron paramagnetic resonance (EPR) studies have been carried out on KU1 fused silica irradiated with neutrons at fluences 10{sup 21} and 10{sup 22} n/m{sup 2}, and gamma-ray doses up to 12 MGy. The effects of post-irradiation thermal annealing treatments, up to 850 deg. C, have also been investigated. Paramagnetic oxygen-related defects (POR and NBOHC) and E'-type defects have been identified and their concentration has been measured as a function of neutron fluence, gamma dose and post-irradiation annealing temperature. It is found that neutrons at the highest fluence generate a much higher concentration of defects (mainly E' and POR, both at concentrations about 5 x 10{sup 18} spins/cm{sup 3}) than gamma irradiations at the highest dose (mainly E' at a concentration about 4 x 10{sup 17} spins/cm{sup 3}). Moreover, for gamma-irradiated samples a lower treatment temperature (about 400 deg. C) is required to annihilate most of the observed defects than for neutron-irradiated ones (about 600 deg. C)

Cavity-enhanced resonant tunneling photodetector at telecommunication wavelengths

International Nuclear Information System (INIS)

Pfenning, Andreas; Hartmann, Fabian; Langer, Fabian; Höfling, Sven; Kamp, Martin; Worschech, Lukas

2014-01-01

An AlGaAs/GaAs double barrier resonant tunneling diode (RTD) with a nearby lattice-matched GaInNAs absorption layer was integrated into an optical cavity consisting of five and seven GaAs/AlAs layers to demonstrate cavity enhanced photodetection at the telecommunication wavelength 1.3 μm. The samples were grown by molecular beam epitaxy and RTD-mesas with ring-shaped contacts were fabricated. Electrical and optical properties were investigated at room temperature. The detector shows maximum photocurrent for the optical resonance at a wavelength of 1.29 μm. At resonance a high sensitivity of 3.1×10 4 A/W and a response up to several pA per photon at room temperature were found

Wavelength modulated surface enhanced (resonance) Raman scattering for background-free detection.

Science.gov (United States)

Praveen, Bavishna B; Steuwe, Christian; Mazilu, Michael; Dholakia, Kishan; Mahajan, Sumeet

2013-05-21

Spectra in surface-enhanced Raman scattering (SERS) are always accompanied by a continuum emission called the 'background' which complicates analysis and is especially problematic for quantification and automation. Here, we implement a wavelength modulation technique to eliminate the background in SERS and its resonant version, surface-enhanced resonance Raman scattering (SERRS). This is demonstrated on various nanostructured substrates used for SER(R)S. An enhancement in the signal to noise ratio for the Raman bands of the probe molecules is also observed. This technique helps to improve the analytical ability of SERS by alleviating the problem due to the accompanying background and thus making observations substrate independent.

Kondo resonance in the neutron spectra of intermediate-valent YbAl3

International Nuclear Information System (INIS)

Walter, U.; Holland-Moritz, E.; Fisk, Z.

1991-01-01

We have measured the dynamic susceptibility of intermediate-valent YbAl 3 by means of cold-neutron scattering. We find two intense magnetic excitations below 40 meV. One of these, with location around 18 meV at helium temperatures, shifts steadily toward 0 meV with increasing temperatures. While crystal field interactions are unable to account for such a behavior, this excitation is in good agreement with a transition from the f ground state to a Kondo resonance as described by the Anderson model. In particular, it definitely excludes a gaplike magnetic response with gap width Δ=30 meV as asserted earlier

Determination of the neutron magnetic moment

International Nuclear Information System (INIS)

Greene, G.L.; Ramsey, N.F.; Mampe, W.; Pendlebury, J.M.; Smith, K.; Dress, W.B.; Miller, P.D.; Perrin, P.

1981-01-01

The neutron magnetic moment has been measured with an improvement of a factor of 100 over the previous best measurement. Using a magnetic resonance spectrometer of the separated oscillatory field type capable of determining a resonance signal for both neutrons and protons (in flowing H 2 O), we find μ/sub n//μ/sub p/ = 0.68497935(17) (0.25 ppM). The neutron magnetic moment can also be expressed without loss of accuracy in a variety of other units

Numerical analysis of resonances induced by s wave neutrons in transmission time-of-flight experiments with a computer IBM 7094 II

International Nuclear Information System (INIS)

Corge, Ch.

1969-01-01

Numerical analysis of transmission resonances induced by s wave neutrons in time-of-flight experiments can be achieved in a fairly automatic way on an IBM 7094/II computer. The involved computations are carried out following a four step scheme: 1 - experimental raw data are processed to obtain the resonant transmissions, 2 - values of experimental quantities for each resonance are derived from the above transmissions, 3 - resonance parameters are determined using a least square method to solve the over determined system obtained by equalling theoretical functions to the correspondent experimental values. Four analysis methods are gathered in the same code, 4 - graphical control of the results is performed. (author) [fr

Experimental verification of neutron phenomenology in lead and of transmutation by adiabatic resonance crossing in accelerator driven systems a summary of the TARC project at CERN

CERN Document Server

Abánades, A; Andriamonje, Samuel A; Angelopoulos, Angelos; Apostolakis, Alcibiades J; Arnould, H; Belle, E; Bompas, C A; Brozzi, Delecurgo; Bueno, J; Buono, S; Carminati, F; Casagrande, Federico; Cennini, P; Collar, J I; Cerro, E; Del Moral, R; Díez, S; Dumps, Ludwig; Eleftheriadis, C; Embid, M; Fernández, R; Gálvez, J; García, J; Gelès, C; Giorni, A; González, E; González, O; Goulas, I; Heuer, R D; Hussonnois, M; Kadi, Y; Karaiskos, P; Kitis, G; Klapisch, Robert; Kokkas, P; Lacoste, V; Le Naour, C; López, C; Loiseaux, J M; Martínez-Val, J M; Méplan, O; Nifnecker, H; Oropesa, J; Papadopoulos, I M; Pavlopoulos, P; Pérez-Enciso, E; Pérez-Navarro, A; Perlado, M; Placci, Alfredo; Poza, M; Revol, Jean Pierre Charles; Rubbia, Carlo; Rubio, Juan Antonio; Sakelliou, L; Saldaña, F; Savvidis, E; Schussler, F; Sirvent, C; Tamarit, J; Trubert, D; Tzima, A; Viano, J B; Vieira, S L; Vlachoudis, V; Zioutas, Konstantin

2001-01-01

The Transmutation by Adiabatic Resonance Crossing (TARC) experiment was carried out as PS211 at the CERN PS from 1996 to 1999. Energy and space distributions of spallation neutrons (produced by 2.5 and 3.57 GeV/c CERN proton beams) slowing down in a 3.3*3.3*3 m/sup 3/ lead volume and neutron capture rates on long-lived fission fragments /sup 99/Tc and /sup 129/I demonstrate that Adiabatic Resonance Crossing (ARC) can be used to eliminate efficiently such nuclear waste and validate innovative simulation. (9 refs).

Gadolinium-DTPA-enhanced magnetic resonance imaging of musculoskeletal infectious processes

International Nuclear Information System (INIS)

Hopkins, K.L.; Li, K.C.P.; Bergman, G.

1995-01-01

The purpose of this study was to assess whether gadolinium-enhanced magnetic resonance imaging (MRI) provides diagnostic information beyond that given by nonenhanced imaging in the evaluation of musculoskeletal infectious processes and whether it can be used for differentiating infectious from noninfectious inflammatory lesions. Magnetic resonance images performed with and without intravenous gadolinium-DTPA in 34 cases in which musculoskeletal infection had been clinically suspected were reviewed. Infectious lesions-including osteomyelitis, pyarthrosis, abscess, and cellulitis-were confirmed in a total of 22 cases: in 15 by biopsy or drainage and in 7 by clinical course. Our results show that gadolinium-DTPA-enhanced MRI is a highly sensitive technique in diagnosing musculoskeletal infectious lesions. It is especially useful in distinguishing abscesses from surrounding cellulitis/myositis. Lack of contrast enhancement rules out infection with a high degree of certainty. However, contrast enhancement cannot be used to reliably distinguish infectious from noninfectious inflammatory conditions. (orig.)

Gadolinium-DTPA-enhanced magnetic resonance imaging of musculoskeletal infectious processes

Energy Technology Data Exchange (ETDEWEB)

Hopkins, K.L. [Dept. of Diagnostic Radiology, Stanford Univ. Medical Center, CA (United States); Li, K.C.P. [Dept. of Diagnostic Radiology, Stanford Univ. Medical Center, CA (United States); Bergman, G. [Dept. of Diagnostic Radiology, Stanford Univ. Medical Center, CA (United States)

1995-07-01

The purpose of this study was to assess whether gadolinium-enhanced magnetic resonance imaging (MRI) provides diagnostic information beyond that given by nonenhanced imaging in the evaluation of musculoskeletal infectious processes and whether it can be used for differentiating infectious from noninfectious inflammatory lesions. Magnetic resonance images performed with and without intravenous gadolinium-DTPA in 34 cases in which musculoskeletal infection had been clinically suspected were reviewed. Infectious lesions-including osteomyelitis, pyarthrosis, abscess, and cellulitis-were confirmed in a total of 22 cases: in 15 by biopsy or drainage and in 7 by clinical course. Our results show that gadolinium-DTPA-enhanced MRI is a highly sensitive technique in diagnosing musculoskeletal infectious lesions. It is especially useful in distinguishing abscesses from surrounding cellulitis/myositis. Lack of contrast enhancement rules out infection with a high degree of certainty. However, contrast enhancement cannot be used to reliably distinguish infectious from noninfectious inflammatory conditions. (orig.)

Absorption enhancement in graphene with an efficient resonator

DEFF Research Database (Denmark)

Xiao, Binggang; Gu, Mingyue; Qin, Kang

2017-01-01

Graphene can be utilized in designing tunable terahertz (THz) devices due to its tunability of sheet conductivity, suffering however with weak light-graphene interactions. In this paper, an absorption enhancement in graphene using a Fabry–Perot resonator is presented, and its performance has been...

Solid-state effects on thermal-neutron cross sections and on low-energy resonances

International Nuclear Information System (INIS)

Harvey, J.A.; Mook, H.A.; Hill, N.W.; Shahal, O.

1982-01-01

The neutron total cross sections of several single crystals (Si, Cu, sapphire), several polycrystalline samples (Cu, Fe, Be, C, Bi, Ta), and a fine-powder copper sample have been measured from 0.002 to 5 eV. The Cu powder and polycrystalline Fe, Be and C data exhibit the expected abrupt changes in cross section. The cross section of the single crystal of Si is smooth with only small broad fluctuations. The data on two single Cu crystals, the sapphire crystal, cast Bi, and rolled samples of Ta and Cu have many narrow peaks approx. 10 -3 eV wide. High resolution (0.3%) transmission measurements were made on the 1.057-eV resonance in 240 Pu and the 0.433-eV resonance in 180 Ta, both at room and low temperatures to study the effects of crystal binding. Although the changes in Doppler broadening with temperature were apparent, no asymmetries due to a recoilless contribution were observed

Neutron scattering. Experiment manuals

International Nuclear Information System (INIS)

Brueckel, Thomas; Heger, Gernot; Richter, Dieter; Roth, Georg; Zorn, Reiner

2012-01-01

The following topics are dealt with: The thermal triple-axis spectrometer PUMA, the high-resolution powder diffractometer SPODI, the hot single-crystal diffractometer HEiDi for structure analysis with neutrons, the backscattering spectrometer SPHERES, the neutron polarization analyzer DNS, the neutron spin-echo spectrometer J-NSE, the small-angle neutron diffractometers KWS-1/-2, the very-small-angle neutron diffractometer with focusing mirror KWS-3, the resonance spin-echo spectrometer RESEDA, the reflectometer TREFF, the time-of-flight spectrometer TOFTOF. (HSI)

Subgroup approximation in Monte Carlo neutron transport calculation in resonance region; Primena podgrupe aproksimacije u Monte Carlo proracunima transporta neutrona u rezonantnoj oblasti energije

Energy Technology Data Exchange (ETDEWEB)

Belicev, P [Vojnotehnicki Inst., Belgrade (Yugoslavia)

1988-07-01

An outline of the problems encountered in the multigroup calculations of the neutron transport in the resonance region is given. The difference between subgroup and multigroup approximation is described briefly. The features of the Monte Carlo code SUBGR are presented. The results of the calculations of the neutron transmission and albedo for infinite iron slabs are given. (author)

Delayed enhancement of peripheral zone of neurofibromas at magnetic resonance imaging

Energy Technology Data Exchange (ETDEWEB)

Kurosaki, Y. [Dept. of Radiology, Inst. of Clinical Medicine, Univ. of Tsukuba (Japan); Kuramoto, K. [Dept. of Radiology, Inst. of Clinical Medicine, Univ. of Tsukuba (Japan); Itai, Y. [Dept. of Radiology, Inst. of Clinical Medicine, Univ. of Tsukuba (Japan)

1996-02-01

It is well known that bizonal histologic appearance characteristic of neurofibromas are reflected on magnetic resonance (MR) images. We report a case in which a delayed enhanced MR image showed that the entire mass enhanced homogeneously resulting in loss of zonal distinction on early enhanced MR image. (orig.)

Resonance phase and sings of P-odd and P-even effects, observable in the reactions with neutrons

International Nuclear Information System (INIS)

Smotritskij, L.M.

2002-01-01

It is shown that introduction of the resonance phase for two quasistationary states with a similar spin and counter parity makes it possible to correlate the sing dependence of both the P-odd and P-even effects, experimentally observed in the reactions with neutrons. The common description of such effects enables determination of the theory unknown (free) parameters from the experiment [ru

Enhanced photoluminescence from ring resonators in hydrogenated amorphous silicon thin films at telecommunications wavelengths.

Science.gov (United States)

Patton, Ryan J; Wood, Michael G; Reano, Ronald M

2017-11-01

We report enhanced photoluminescence in the telecommunications wavelength range in ring resonators patterned in hydrogenated amorphous silicon thin films deposited via low-temperature plasma enhanced chemical vapor deposition. The thin films exhibit broadband photoluminescence that is enhanced by up to 5 dB by the resonant modes of the ring resonators due to the Purcell effect. Ellipsometry measurements of the thin films show a refractive index comparable to crystalline silicon and an extinction coefficient on the order of 0.001 from 1300 nm to 1600 nm wavelengths. The results are promising for chip-scale integrated optical light sources.

Numerical analysis of resonances induced by s wave neutrons in transmission time-of-flight experiments with a computer IBM 7094 II; Methodes d'analyse des resonances induites par les neutrons s dans les experiences de transmission par temps de vol et automatisation de ces methodes sur ordinateur IBM 7094 II

Energy Technology Data Exchange (ETDEWEB)

Corge, Ch. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1969-01-01

Numerical analysis of transmission resonances induced by s wave neutrons in time-of-flight experiments can be achieved in a fairly automatic way on an IBM 7094/II computer. The involved computations are carried out following a four step scheme: 1 - experimental raw data are processed to obtain the resonant transmissions, 2 - values of experimental quantities for each resonance are derived from the above transmissions, 3 - resonance parameters are determined using a least square method to solve the over determined system obtained by equalling theoretical functions to the correspondent experimental values. Four analysis methods are gathered in the same code, 4 - graphical control of the results is performed. (author) [French] L'automatisation, sur ordinateur IBM 7094/II, de l'analyse des resonances induites par les neutrons s dans les experiences de transmission par temps de vol a ete accomplie en la decomposant selon un schema articule en quatre phases: 1 - le traitement des donnees experimentales brutes pour obtenir les transmissions interfero-resonnantes, 2 - la determination des grandeurs d'analyse a partir des transmissions precedentes, 3 - l'analyse proprement dite des resonances dont les parametres sont obtenus par la resolution d'un systeme surabondant. Quatre methodes d'analyse sont groupees en un meme programme, 4 - la procedure de verification graphique. (auteur)

Extension of the AUS reactor neutronics system for application to fusion blanket neutronics

International Nuclear Information System (INIS)

Robinson, G.S.

1984-03-01

The AUS modular code scheme for reactor neutronics computations has been extended to apply to fusion blanket neutronics. A new group cross-section library with 200 neutron groups, 37 photon groups and kerma factor data has been generated from ENDF/B-IV. The library includes neutron resonance subgroup parameters and temperature-dependent data for thermal neutron scattering matrices. The validity of the overall calculation system for fusion applications has been checked by comparison with a number of published conceptual design studies

The structure of the Gamow-Teller giant resonance and consequences for beta-delayed neutron spectra and element synthesis

International Nuclear Information System (INIS)

Klapdor, H.V.

1976-01-01

Recent results in β-delayed neutron emission are interpreted by structure of the Gamow-Teller giant resonance not included in the 'gross-theory' of β-decay. Inclusion of this structure of the β-decay function is important for calculations of β-decay production rates for heavy nuclides by astrophysical processes and thermonuclear explosions. (Auth.)

The magnetic order of GdMn₂Ge₂ studied by neutron diffraction and x-ray resonant magnetic scattering.

Science.gov (United States)

Granovsky, S A; Kreyssig, A; Doerr, M; Ritter, C; Dudzik, E; Feyerherm, R; Canfield, P C; Loewenhaupt, M

2010-06-09

The magnetic structure of GdMn₂Ge₂ (tetragonal I4/mmm) has been studied by hot neutron powder diffraction and x-ray resonant magnetic scattering techniques. These measurements, along with the results of bulk experiments, confirm the collinear ferrimagnetic structure with moment direction parallel to the c-axis below T(C) = 96 K and the collinear antiferromagnetic phase in the temperature region T(C) < T < T(N) = 365 K. In the antiferromagnetic phase, x-ray resonant magnetic scattering has been detected at Mn K and Gd L₂ absorption edges. The Gd contribution is a result of an induced Gd 5d electron polarization caused by the antiferromagnetic order of Mn-moments.

Resonant cavity enhanced multi-analyte sensing

Science.gov (United States)

Bergstein, David Alan

Biological research and medicine increasingly depend on interrogating binding interactions among small segments of DNA, RNA, protein, and bio-specific small molecules. Microarray technology, which senses the affinity for target molecules in solution for a multiplicity of capturing agents fixed to a surface, has been used in biological research for gene expression profiling and in medicine for molecular biomarker detection. Label-free affinity sensing is preferable as it avoids fluorescent labeling of the target molecules, reducing test cost and variability. The Resonant Cavity Imaging Biosensor (RCIB) is a label-free optical inference based technique introduced that scales readily to high throughput and employs an optical resonant cavity to enhance sensitivity by a factor of 100 or more. Near-infrared light centered at 1512.5 nm couples resonantly through a cavity constructed from Si/SiO2 Bragg reflectors, one of which serves as the binding surface. As the wavelength is swept 5 nm, an Indium-Gallium-Arsenide digital camera monitors cavity transmittance at each pixel with resolution 128 x 128. A wavelength shift in the local resonant response of the optical cavity indicates binding. Positioning the sensing surface with respect to the standing wave pattern of the electric field within the cavity, one can control the sensitivity of the measurement to the presence of bound molecules thereby enhancing or suppressing sensitivity where appropriate. Transmitted intensity at thousands of pixel locations are recorded simultaneously in a 10 s, 5 nm scan. An initial proof-of-principle setup was constructed. A sample was fabricated with 25, 100 mum wide square regions, each with a different density of 1 mum square depressions etched 12 nm into the S1O 2 surface. The average depth of each etched region was found with 0.05 nm RMS precision when the sample remains loaded in the setup and 0.3 nm RMS precision when the sample is removed and replaced. Selective binding of the protein

Comparison of the Porter-Thomas distribution with neutron resonance data of even-even nuclei

International Nuclear Information System (INIS)

Camarda, H.S.

1994-01-01

The low-energy neutron resonance data of the even-even nuclei 152 Sm, 158 Gd, 162 Dy, 166,168 Er, 182 W, 232 Th, and 236,238 U have been examined in order to test the validity of the Porter-Thomas distribution of the reduced neutron widths---a chi-squared distribution with one degree of freedom (v=1). In an attempt to circumvent the ever-present problems of missed or spurious s wave levels as well as extra p wave levels, a maximum likelihood statistic was employed which used only measured widths greater than some minimum value. A Bayes-theory test applied to the data helped to ensure that p wave contamination of the s wave level population was not significant. The error-weighted value of the number of degrees of freedom for the nine nuclei studied, left-angle v right-angle=0.98±0.10, is consistent with the theoretical expectation of v=1

Raman scattering enhancement in photon-plasmon resonance mediated metal-dielectric microcavity

International Nuclear Information System (INIS)

Guddala, Sriram; Narayana Rao, D.; Dwivedi, Vindesh K.; Vijaya Prakash, G.

2013-01-01

Here, we report the photon-plasmon interaction scheme and enhanced field strengths resulted into the amplification of phonon in a novel microcavity. A metal-dielectric microcavity, with unified cavity photonic mode and localized surface plasmon resonances, is visualized by impregnating the gold nanoparticles into the deep see-through nano-sized pores of porous silicon microcavity. The intense optical field strengths resulting from the photon-plasmon interactions are probed by both resonant and non-resonant Raman scattering experiments. Due to photon-plasmon-phonon interaction mechanism, several orders of enhancement in the intensity of scattered Raman Stokes photon (at 500 cm −1 ) are observed. Our metal nanoparticle-microcavity hybrid system shows the potential to improve the sensing figure of merit as well as the applications of plasmonics for optoelectronics, photovoltaics, and related technologies

High resolution neutron spectroscopy for helium isotopes

International Nuclear Information System (INIS)

Abdel-Wahab, M.S.; Klages, H.O.; Schmalz, G.; Haesner, B.H.; Kecskemeti, J.; Schwarz, P.; Wilczynski, J.

1992-01-01

A high resolution fast neutron time-of-flight spectrometer is described, neutron time-of-flight spectra are taken using a specially designed TDC in connection to an on-line computer. The high time-of-flight resolution of 5 ps/m enabled the study of the total cross section of 4 He for neutrons near the 3/2 + resonance in the 5 He nucleus. The resonance parameters were determined by a single level Breit-Winger fit to the data. (orig.)

THE INTERMEDIATE NEUTRON-CAPTURE PROCESS AND CARBON-ENHANCED METAL-POOR STARS

Energy Technology Data Exchange (ETDEWEB)

Hampel, Melanie [Zentrum für Astronomie der Universität Heidelberg, Landessternwarte, Königstuhl 12, D-69117 Heidelberg (Germany); Stancliffe, Richard J. [Argelander-Institut für Astronomie, University of Bonn, Auf dem Hügel 71, D-53121 Bonn (Germany); Lugaro, Maria [Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, Hungarian Academy of Sciences, H-1121 Budapest (Hungary); Meyer, Bradley S., E-mail: mhampel@lsw.uni-heidelberg.de [Department of Physics and Astronomy, Clemson University, Clemson, SC 29634-0978 (United States)

2016-11-10

Carbon-enhanced metal-poor (CEMP) stars in the Galactic Halo display enrichments in heavy elements associated with either the s (slow) or the r (rapid) neutron-capture process (e.g., barium and europium, respectively), and in some cases they display evidence of both. The abundance patterns of these CEMP- s / r stars, which show both Ba and Eu enrichment, are particularly puzzling, since the s and the r processes require neutron densities that are more than ten orders of magnitude apart and, hence, are thought to occur in very different stellar sites with very different physical conditions. We investigate whether the abundance patterns of CEMP- s / r stars can arise from the nucleosynthesis of the intermediate neutron-capture process (the i process), which is characterized by neutron densities between those of the s and the r processes. Using nuclear network calculations, we study neutron capture nucleosynthesis at different constant neutron densities n ranging from 10{sup 7}–10{sup 15} cm{sup -3}. With respect to the classical s process resulting from neutron densities on the lowest side of this range, neutron densities on the highest side result in abundance patterns, which show an increased production of heavy s -process and r -process elements, but similar abundances of the light s -process elements. Such high values of n may occur in the thermal pulses of asymptotic giant branch stars due to proton ingestion episodes. Comparison to the surface abundances of 20 CEMP- s / r stars shows that our modeled i -process abundances successfully reproduce observed abundance patterns, which could not be previously explained by s -process nucleosynthesis. Because the i -process models fit the abundances of CEMP- s / r stars so well, we propose that this class should be renamed as CEMP- i .

Resonant Dipole Nanoantenna Arrays for Enhanced Terahertz Spectroscopy

KAUST Repository

Toma, A.

2015-08-04

Our recent studies on dipole nanoantenna arrays resonating in the terahertz frequency range (0.1 – 10 THz) will be presented. The main near- and far-field properties of these nanostructures will be shown and their application in enhanced terahertz spectroscopy of tiny quantities of nanomaterials will be discussed.

Program RECENT (version 79-1): reconstruction of energy-dependent neutron cross sections from resonance parameters in the ENDF/B format

International Nuclear Information System (INIS)

Cullen, D.E.

1979-01-01

Program RECENT reconstructs energy-dependent neutron total, elastic, capture, and fission cross sections from a combination of resonance parameters and tabulated background cross sections in the ENDF/B format. Entire evaluations, not just cross sections, are written to the result file, which is in ENDF/B format. The output includes the original resonance parameters in a form that can be used in Doppler broadening and self-shielding calculations. A listing of the source deck is available on request. 5 figures, 5 tables

Nuclear Resonance Fluorescence to Measure Plutonium Mass in Spent Nuclear Fuel

Energy Technology Data Exchange (ETDEWEB)

Ludewigt, Bernhard A; Quiter, Brian J.; Ambers, Scott D.

2011-01-14

The Next Generation Safeguard Initiative (NGSI) of the U.S Department of Energy is supporting a multi-lab/university collaboration to quantify the plutonium (Pu) mass in spent nuclear fuel (SNF) assemblies and to detect the diversion of pins with non-destructive assay (NDA) methods. The following 14 NDA techniques are being studied: Delayed Neutrons, Differential Die-Away, Differential Die-Away Self-Interrogation, Lead Slowing Down Spectrometer, Neutron Multiplicity, Passive Neutron Albedo Reactivity, Total Neutron (Gross Neutron), X-Ray Fluorescence, {sup 252}Cf Interrogation with Prompt Neutron Detection, Delayed Gamma, Nuclear Resonance Fluorescence, Passive Prompt Gamma, Self-integration Neutron Resonance Densitometry, and Neutron Resonance Transmission Analysis. Understanding and maturity of the techniques vary greatly, ranging from decades old, well-understood methods to new approaches. Nuclear Resonance Fluorescence (NRF) is a technique that had not previously been studied for SNF assay or similar applications. Since NRF generates isotope-specific signals, the promise and appeal of the technique lies in its potential to directly measure the amount of a specific isotope in an SNF assay target. The objectives of this study were to design and model suitable NRF measurement methods, to quantify capabilities and corresponding instrumentation requirements, and to evaluate prospects and the potential of NRF for SNF assay. The main challenge of the technique is to achieve the sensitivity and precision, i.e., to accumulate sufficient counting statistics, required for quantifying the mass of Pu isotopes in SNF assemblies. Systematic errors, considered a lesser problem for a direct measurement and only briefly discussed in this report, need to be evaluated for specific instrument designs in the future. Also, since the technical capability of using NRF to measure Pu in SNF has not been established, this report does not directly address issues such as cost, size

Gold split-ring resonators (SRRs) as substrates for surface-enhanced raman scattering

KAUST Repository

Yue, Weisheng

2013-10-24

We used gold split ring resonators (SRRs) as substrates for surface-enhanced Raman scattering (SERS). The arrays of SRRs were fabricated by electron-beam lithography in combination with plasma etching. In the detection of rhodamine 6G (R6G) molecules, SERS enhancement factors of the order of 105 was achieved. This SERS enhancement increased as the size of the split gap decrease as a consequence of the matching between the resonance wavelength of the SRRs and the excitation wavelength of SERS. As the size of the split gap decreased, the localized surface plasmon resonance shifted to near the excitation wavelength and, thus, resulted in the increase in the electric field on the nanostructures. We used finite integration method (FIT) to simulate numerically the electromagnetic properties of the SRRs. The results of the simulation agreed well with our experimental observations. We anticipate this work will provide an approach to manipulate the SERS enhancement by modulating the size of split gap with SRRs without affecting the area and structural arrangement. © 2013 American Chemical Society.

Gold split-ring resonators (SRRs) as substrates for surface-enhanced raman scattering

KAUST Repository

Yue, Weisheng; Yang, Yang; Wang, Zhihong; Chen, Longqing; Wang, Xianbin

2013-01-01

We used gold split ring resonators (SRRs) as substrates for surface-enhanced Raman scattering (SERS). The arrays of SRRs were fabricated by electron-beam lithography in combination with plasma etching. In the detection of rhodamine 6G (R6G) molecules, SERS enhancement factors of the order of 105 was achieved. This SERS enhancement increased as the size of the split gap decrease as a consequence of the matching between the resonance wavelength of the SRRs and the excitation wavelength of SERS. As the size of the split gap decreased, the localized surface plasmon resonance shifted to near the excitation wavelength and, thus, resulted in the increase in the electric field on the nanostructures. We used finite integration method (FIT) to simulate numerically the electromagnetic properties of the SRRs. The results of the simulation agreed well with our experimental observations. We anticipate this work will provide an approach to manipulate the SERS enhancement by modulating the size of split gap with SRRs without affecting the area and structural arrangement. © 2013 American Chemical Society.

Surface-enhanced Raman scattering (SERS) of riboflavin on nanostructured Ag surfaces: The role of excitation wavelength, plasmon resonance and molecular resonance

Science.gov (United States)

Šubr, Martin; Kuzminova, Anna; Kylián, Ondřej; Procházka, Marek

2018-05-01

Optimization of surface-enhanced Raman scattering (SERS)-based sensors for (bio)analytical applications has received much attention in recent years. For optimum sensitivity, both the nanostructure fabrication process and the choice of the excitation wavelength used with respect to the specific analyte studied are of crucial importance. In this contribution, detailed SERS intensity profiles were measured using gradient nanostructures with the localized surface-plasmon resonance (LSPR) condition varying across the sample length and using riboflavin as the model biomolecule. Three different excitation wavelengths (633 nm, 515 nm and 488 nm) corresponding to non-resonance, pre-resonance and resonance excitation with respect to the studied molecule, respectively, were tested. Results were interpreted in terms of a superposition of the enhancement provided by the electromagnetic mechanism and intrinsic properties of the SERS probe molecule. The first effect was dictated mainly by the degree of spectral overlap between the LSPR band, the excitation wavelength along with the scattering cross-section of the nanostructures, while the latter was influenced by the position of the molecular resonance with respect to the excitation wavelength. Our experimental findings contribute to a better understanding of the SERS enhancement mechanism.

Resonance self-shielding effect analysis of neutron data libraries applied for the dual-cooled waste transmutation blanket of the fusion-driven subcritical system

International Nuclear Information System (INIS)

Liu Haibo; Wu Yican; Zheng Shanliang; Zhang Chunzao

2004-01-01

Based on the Fusion-Driven Subcritical System (FDS-I), the 25 groups, 175 groups and 620 groups neutron nuclear data libraries with/without resonance self-shielding correction are made with the Njoy and Transx codes, and the K eff and reaction rates are calculated with the Anisn code. The conclusion indicates that the resonance self-shielding effect affects the reaction rates strongly. (authors)

Oxygen-enhanced magnetic resonance ventilation imaging of lung

International Nuclear Information System (INIS)

Ohno, Yoshiharu; Chen Qun; Hatabu, Hiroto

2001-01-01

The oxygen-enhanced magnetic resonance (MR) ventilation imaging is a new technique, and the full extent of its physiological significance has not been elucidated. This review article includes background on (1) respiratory physiology; (2) mechanism and optimization of oxygen-enhanced MR imaging technique; (3) recent applications in animal and human models; and (4) merits and demerits of the technique in comparison with hyperpolarized noble gas MR ventilation imaging. Application of oxygen-enhanced MR ventilation imaging to patients with pulmonary diseases has been very limited. However, we believe that further basic studies, as well as clinical applications of this new technique will define the real significance of oxygen-enhanced MR ventilation imaging in the future of pulmonary functional imaging and its usefulness for diagnostic radiology

Approximation for the adjoint neutron spectrum

International Nuclear Information System (INIS)

Suster, Luis Carlos; Martinez, Aquilino Senra; Silva, Fernando Carvalho da

2002-01-01

The proposal of this work is the determination of an analytical approximation which is capable to reproduce the adjoint neutron flux for the energy range of the narrow resonances (NR). In a previous work we developed a method for the calculation of the adjoint spectrum which was calculated from the adjoint neutron balance equations, that were obtained by the collision probabilities method, this method involved a considerable quantity of numerical calculation. In the analytical method some approximations were done, like the multiplication of the escape probability in the fuel by the adjoint flux in the moderator, and after these approximations, taking into account the case of the narrow resonances, were substituted in the adjoint neutron balance equation for the fuel, resulting in an analytical approximation for the adjoint flux. The results obtained in this work were compared to the results generated with the reference method, which demonstrated a good and precise results for the adjoint neutron flux for the narrow resonances. (author)

Measurement of the ROT effect in the neutron induced fission of 235U in the 0.3 eV resonance at a hot source of polarized neutrons

Science.gov (United States)

Kopatch, Yuri; Novitsky, Vadim; Ahmadov, Gadir; Gagarsky, Alexei; Berikov, Daniyar; Danilyan, Gevorg; Hutanu, Vladimir; Klenke, Jens; Masalovich, Sergey

2018-03-01

The TRI and ROT asymmetries in fission of heavy nuclei have been extensively studied during more than a decade. The effects were first discovered in the ternary fission in a series of experiments performed at the ILL reactor (Grenoble) by a collaboration of Russian and European institutes, and were carefully measured for a number of fissioning nuclei. Later on, the ROT effect has been observed in the emission of prompt gamma rays and neutrons in fission of 235U and 233U, although its value was an order of magnitude smaller than in the α-particle emission from ternary fission. All experiments performed so far are done with cold polarized neutrons, what assumes a mixture of several spin states, the weights of these states being not well known. The present paper describes the first attempt to get "clean" data by performing the measurement of gamma and neutron asymmetries in an isolated resonance of 235U at the POLI instrument of the FRM2 reactor in Garching.

Neutron scattering. Experiment manuals

Energy Technology Data Exchange (ETDEWEB)

Brueckel, Thomas; Heger, Gernot; Richter, Dieter; Roth, Georg; Zorn, Reiner (eds.)

2010-07-01

The following topics are dealt with: The thermal triple axis spectrometer PUMA, the high-resolution powder diffractometer SPODI, the hot single-crystal diffractometer HEiDi for structure analysis with neutrons, the backscattering spectrometer SPHERES, neutron polarization analysis with tht time-of-flight spectrometer DNS, the neutron spin-echo spectrometer J-NSE, small-angle neutron scattering with the KWS-1 and KWS-2 diffractometers, the very-small-angle neutron scattering diffractrometer with focusing mirror KWS-3, the resonance spin-echo spectrometer RESEDA, the reflectometer TREFF, the time-of-flight spectrometer TOFTOF. (HSI)

Neutron scattering. Experiment manuals

International Nuclear Information System (INIS)

Brueckel, Thomas; Heger, Gernot; Richter, Dieter; Roth, Georg; Zorn, Reiner

2010-01-01

The following topics are dealt with: The thermal triple axis spectrometer PUMA, the high-resolution powder diffractometer SPODI, the hot single-crystal diffractometer HEiDi for structure analysis with neutrons, the backscattering spectrometer SPHERES, neutron polarization analysis with tht time-of-flight spectrometer DNS, the neutron spin-echo spectrometer J-NSE, small-angle neutron scattering with the KWS-1 and KWS-2 diffractometers, the very-small-angle neutron scattering diffractrometer with focusing mirror KWS-3, the resonance spin-echo spectrometer RESEDA, the reflectometer TREFF, the time-of-flight spectrometer TOFTOF. (HSI)

A neutron beam polarizer for study of parity violation in neutron-nucleus interactions

International Nuclear Information System (INIS)

Penttilae, S.I.; Bowman, J.D.; Frankle, C.M.; Seestrom, S.J.; Yen, Yi-Fen; Delheij, P.P.J.; Haase, D.G.; Postma, H.

1994-01-01

A dynamically-polarized proton target operating at 5 Tesla and 1 K has been built to, neutron beam for studies of parity violation in compound-nuclear resonances. Nearly 0.9 proton polarization was obtained in an electron-beam irradiated ammonia target. This was used to produce a neutron beam polarization of 0.7 at epithermal energies. The combination of the polarized proton target and the LANSCE spallation neutron source produces the most intense pulsed polarized epithermal neutron beam in the world. The neutron-beam polarizer is described and methods to determine neutron beam polarization are presented

Nanoscale imaging of photocurrent enhancement by resonator array photovoltaic coatings

Science.gov (United States)

Ha, Dongheon; Yoon, Yohan; Zhitenev, Nikolai B.

2018-04-01

Nanoscale surface patterning commonly used to increase absorption of solar cells can adversely impact the open-circuit voltage due to increased surface area and recombination. Here, we demonstrate absorptivity and photocurrent enhancement using silicon dioxide (SiO2) nanosphere arrays on a gallium arsenide (GaAs) solar cell that do not require direct surface patterning. Due to the combined effects of thin-film interference and whispering gallery-like resonances within nanosphere arrays, there is more than 20% enhancement in both absorptivity and photocurrent. To determine the effect of the resonance coupling between nanospheres, we perform a scanning photocurrent microscopy based on a near-field scanning optical microscopy measurement and find a substantial local photocurrent enhancement. The nanosphere-based antireflection coating (ARC), made by the Meyer rod rolling technique, is a scalable and a room-temperature process; and, can replace the conventional thin-film-based ARCs requiring expensive high-temperature vacuum deposition.

Unexpected enhancements and reductions of rf spin resonance strengths

Directory of Open Access Journals (Sweden)

M. A. Leonova

2006-05-01

Full Text Available We recently analyzed all available data on spin-flipping stored beams of polarized protons, electrons, and deuterons. Fitting the modified Froissart-Stora equation to the measured polarization data after crossing an rf-induced spin resonance, we found 10–20-fold deviations from the depolarizing resonance strength equations used for many years. The polarization was typically manipulated by linearly sweeping the frequency of an rf dipole or rf solenoid through an rf-induced spin resonance; spin-flip efficiencies of up to 99.9% were obtained. The Lorentz invariance of an rf dipole’s transverse ∫Bdl and the weak energy dependence of its spin resonance strength E together imply that even a small rf dipole should allow efficient spin flipping in 100 GeV or even TeV storage rings; thus, it is important to understand these large deviations. Therefore, we recently studied the resonance strength deviations experimentally by varying the size and vertical betatron tune of a 2.1  GeV/c polarized proton beam stored in COSY. We found no dependence of E on beam size, but we did find almost 100-fold enhancements when the rf spin resonance was near an intrinsic spin resonance.

Resonance-enhanced laser-induced plasma spectroscopy: ambient gas effects

International Nuclear Information System (INIS)

Lui, S.L.; Cheung, N.H.

2003-01-01

When performing laser-induced plasma spectroscopy for elemental analysis, the sensitivity could be significantly enhanced if the plume was resonantly rekindled by a dye laser pulse. The extent of the enhancement was found to depend on the ambient gas. Air, nitrogen, helium, argon and xenon at pressures ranging from vacuum to 1 bar were investigated. In vacuum, the analyte signal was boosted because of reduced cooling, but it soon decayed as the plume freely expanded. By choosing the right ambient gas at the right pressure, the expanding plume could be confined as well as thermally insulated to maximize the analyte signal. For instance, an ambient of 13 mbar xenon yielded a signal-to-noise ratio of 110. That ratio was 53 when the pellet was ablated in air, and decreased further to 5 if the dye laser was tuned off resonance

The pygmy quadrupole resonance and neutron-skin modes in 124Sn

Directory of Open Access Journals (Sweden)

M. Spieker

2016-01-01

Full Text Available We present an extensive experimental study of the recently predicted pygmy quadrupole resonance (PQR in Sn isotopes, where complementary probes were used. In this study, (α,α′γ and (γ,γ′ experiments were performed on 124Sn. In both reactions, Jπ=2+ states below an excitation energy of 5 MeV were populated. The E2 strength integrated over the full transition densities could be extracted from the (γ,γ′ experiment, while the (α,α′γ experiment at the chosen kinematics strongly favors the excitation of surface modes because of the strong α-particle absorption in the nuclear interior. The excitation of such modes is in accordance with the quadrupole-type oscillation of the neutron skin predicted by a microscopic approach based on self-consistent density functional theory and the quasiparticle-phonon model (QPM. The newly determined γ-decay branching ratios hint at a non-statistical character of the E2 strength, as it has also been recently pointed out for the case of the pygmy dipole resonance (PDR. This allows us to distinguish between PQR-type and multiphonon excitations and, consequently, supports the recent first experimental indications of a PQR in 124Sn.

Low temperature and neutron physics studies

International Nuclear Information System (INIS)

Shull, C.G.

1989-01-01

A search for a novel coupling interaction between the Pendelloesung periodicity which is formed in a diffracting crystal and the Larmor precession of neutrons in a magnetic field has been carried out. This interaction is expected to exhibit a resonant behavior when the two spatial periodicities become matched upon scanning the magnetic field being applied to the crystal. Observations on a diffracting, perfect crystal of silicon with neutrons of wavelength 1 Angstrom show the expected resonant action but some discrepancy between the observed magnitude of the resonance effects remains for interpretation. 16 refs

Simultaneous measurement of neutron-induced fission and capture cross sections for {sup 241}Am at neutron energies below fission threshold

Energy Technology Data Exchange (ETDEWEB)

Hirose, K., E-mail: hirose.kentaro@jaea.go.jp [Advanced Science Research Center, Japan Atomic Energy Agency (JAEA), Tokai, Ibaraki 319-1195 (Japan); Nishio, K.; Makii, H.; Nishinaka, I.; Ota, S. [Advanced Science Research Center, Japan Atomic Energy Agency (JAEA), Tokai, Ibaraki 319-1195 (Japan); Nagayama, T. [Advanced Science Research Center, Japan Atomic Energy Agency (JAEA), Tokai, Ibaraki 319-1195 (Japan); Graduate School of Science and Engineering, Ibaraki University, Mito 310-0056 (Japan); Tamura, N. [Advanced Science Research Center, Japan Atomic Energy Agency (JAEA), Tokai, Ibaraki 319-1195 (Japan); Graduate School of Science and Technology, Niigata University, Niigata 950-2181 (Japan); Goto, S. [Graduate School of Science and Technology, Niigata University, Niigata 950-2181 (Japan); Andreyev, A.N. [Advanced Science Research Center, Japan Atomic Energy Agency (JAEA), Tokai, Ibaraki 319-1195 (Japan); Department of Physics, University of York, Heslington, York YO10 5DD (United Kingdom); Vermeulen, M.J. [Advanced Science Research Center, Japan Atomic Energy Agency (JAEA), Tokai, Ibaraki 319-1195 (Japan); Gillespie, S.; Barton, C. [Department of Physics, University of York, Heslington, York YO10 5DD (United Kingdom); Kimura, A.; Harada, H. [Nuclear Science and Engineering Center, JAEA, Tokai, Ibaraki 319-1195 (Japan); Meigo, S. [J-PARC Center, JAEA, Tokai, Ibaraki 319-1195 (Japan); Chiba, S. [Research Laboratory for Nuclear Reactors, Tokyo Institute of Technology, Tokyo 152-8550 (Japan); Ohtsuki, T. [Research Reactor Institute, Kyoto University, Kumatori-cho S' ennangun,Osaka 590-0494 (Japan)

2017-06-01

Fission and capture reactions were simultaneously measured in the neutron-induced reactions of {sup 241}Am at the spallation neutron facility of the Japan Proton Accelerator Research Complex (J-PARC). Data for the neutron energy range of E{sub n}=0.1–20 eV were taken with the TOF method. The fission events were observed by detecting prompt neutrons accompanied by fission using liquid organic scintillators. The capture reaction was measured by detecting γ rays emitted in the deexcitation of the compound nuclei using the same detectors, where the prompt fission neutrons and capture γ rays were separated by a pulse shape analysis. The cross sections were obtained by normalizing the relative yields at the first resonance to evaluations or other experimental data. The ratio of the fission to capture cross sections at each resonance is compared with those from an evaluated nuclear data library and other experimental data. Some differences were found between the present values and the library/literature values at several resonances.

Fully non-destructive elemental analyses of copper-alloy artefacts with neutron resonance capture between 1 eV and 10 keV

International Nuclear Information System (INIS)

Postma, H.; Blaauw, M.; Corvi, F.

2002-01-01

Neutron capture resonance analysis (NRCA) using a pulsed neutron beam and the time-of-flight (ToF) technique is a new method to determine the elemental compositions of artifacts. Neutron capture by an object can be observed by detecting the prompt capture gamma-radiation. Energies of resonance peaks in the ToF spectrum are the 'fingerprints' for elements. Since it is not necessary to determine the energy of the gamma-rays with any precision, it is possible to use a detector system with high detection efficiency. It is not necessary to take parts from an object for the analysis or to clean the surface or to do other things which might damage the object. Therefore NRCA is especially of interest for studying fragile, small or valuable objects from which one does not want to, or cannot take samples, or for which cleaning of even a small part of a surface is not desirable. Knowledge of the elemental composition of artifacts might be useful for archaeological or historical studies or to check the authenticity of an artifact. Recent experiments at the GELINA facility in Geel, Belgium show that indeed NRCA is a useful way to recognize elements on the basis of the energies of resonance in the ToF spectrum. We applied NRCA to several copper-alloy artifacts. In the studied objects very little activity was induced, which also disappeared quickly. Thus resonance energies allow us to recognize elements of an object. In addition, a quantitative analysis is possible on the basis of resonance areas. In the case of our artefacts the amounts of several elements (notably Sn, As, Zn, Fe, Sb, Ag, Au) were determined as ratios to copper. For a strong resonance it is necessary to take self-shielding into account. The effect of self-shielding made it possible to determine the absolute amount of copper by comparing the areas of a weak and a strong copper resonance, and thus also absolute amounts of the other components could be determined. The method of NRCA is discussed in relation to the

Connection factor calculation for isotopic neutron flux measurements with foil detectors

International Nuclear Information System (INIS)

Avila L, J.

1987-01-01

Thermal and resonance neutron self-shielding factors, neutron flux distortion and edge effects as well as a connection factor for neutron flux profile around a foil detector have been calculated. A general expression for resonance self shielding factor is presented in order to take into account the most important resonances for a given isotope. A computer program SPRESYTER.BAS was written and results for In-115 and Au-197 foils are given

Information about the properties of highly-excited states of nuclei, obtained in the reaction (n, α) with resonance neutrons

International Nuclear Information System (INIS)

Balabanov, N.P.

1980-01-01

The results measurements of total α-widths in the reaction (n, α) using resonance neutrons have been analysed. The data obtained have been compared with the predictions of the statistical theory and the cluster model. Attention has been paid to some possible deviations from the statistical relationships in the behaviour of total α-widths

Treatment of External Levels in Neutron Resonance Fitting: Application to the Nonfissile Nuclide 52Cr

International Nuclear Information System (INIS)

Froehner, Fritz H.; Bouland, Olivier

2001-01-01

Measured neutron resonance cross sections are usually analyzed and parametrized by fitting theoretical curves to high-resolution point data. Theoretically, the cross sections depend mainly on the 'internal' levels inside the fitted energy range but also on the 'external' levels outside. Although the external levels are mostly unknown, they must be accounted for. If they are simply omitted, the experimental data cannot be fitted satisfactorily. Especially with elastic scattering and total cross-section data, one gets troublesome edge effects and difficulties with the potential cross section between resonances. Various ad hoc approaches to these problems are still being used, involving replacement of the unknown levels by equidistant ('picket fence') or Monte Carlo-sampled resonance sequences, or replication of the internal level sequence; however, more convenient, better working, and theoretically sound techniques have been available for decades. These analytical techniques are reviewed. They describe the contribution of external levels to the R matrix concisely in terms of average resonance parameters (strength function, effective radius, etc.). A more recent, especially convenient approximation accounts for the edge effects by just one fictitious pair of very broad external resonances. Fitting the thermal region, including accurately known thermal cross sections, is often done by adjusting a number of bound levels by trial and error, although again a simple analytical recipe involving just one bound level has been available for a long time. For illustration, these analytical techniques are applied to the resolved resonance region of 52 Cr. The distinction between channel radii and effective radii, crucial in the present context, is emphasized

The role fo the Pygmy resonance in the synthesis of heavy elements with radioactive beams

International Nuclear Information System (INIS)

Hussein, M.S.

1990-12-01

It is suggested that the inclusion of the virtual excitation of the soft giant dipole (pygmy) resonance in the calculation of the cross-section for very neutron-rich radioactive beam-induced fusion reactions may enhance the formation probability of the heavy compound nucleus produced at low excitation energy. (author)

URR [Unresolved Resonance Region] computer code: A code to calculate resonance neutron cross-section probability tables, Bondarenko self-shielding factors, and self-indication ratios for fissile and fertile nuclides

International Nuclear Information System (INIS)

Leal, L.C.; de Saussure, G.; Perez, R.B.

1990-01-01

The URR computer code has been developed to calculate cross-section probability tables, Bondarenko self-shielding factors, and self-indication ratios for fertile and fissile isotopes in the unresolved resonance region. Monte Carlo methods are utilized to select appropriate resonance parameters and to compute the cross sections at the desired reference energy. The neutron cross sections are calculated by the single-level Breit-Wigner formalism with s-, p-, and d-wave contributions. The cross-section probability tables are constructed by sampling by Doppler broadened cross-sections. The various self-shielding factors are computer numerically as Lebesgue integrals over the cross-section probability tables

A neutron beam polarizer for study of parity violation in neutron-nucleus interactions

International Nuclear Information System (INIS)

Penttilae, S.I.; Bowman, J.D.; Delheij, P.P.; Frankle, C.M.; Haase, D.G.; Postma, H.; Seestrom, S.J.; Yen, Y.

1995-01-01

A dynamically-polarized proton target operating at 5 Tesla and 1 K has been built to polarize an epithermal neutron beam for studies of parity violation in compound-nuclear resonances. Nearly 0.9 proton polarization was obtained in an electron-beam irradiated ammonia target. This was used to produce a neutron beam polarization of 0.7 at epithermal energies. The combination of the polarized proton target and the LANSCE spallation neutron source produces the most intense pulsed polarized epithermal neutron beam in the world. The neutron-beam polarizer is described and methods to determine neutron beam polarization are presented. copyright 1995 American Institute of Physics

Temperature imaging using epithermal neutrons

International Nuclear Information System (INIS)

Fowler, P.H.; Taylor, A.D.

1987-08-01

The paper concerns the temperature measurement of suitable targets, both remotely and non-invasively, using epithermal neutrons. The text was presented at the Neutron Resonance Radiography Workshop, Los Alamos, U.S.A., 1987. The technique is demonstrated for tantalum foils at different temperatures, using a pulsed beam of epithermal neutrons, at both Los Alamos and ISIS (United Kingdom). Results on the measured time-of-flight spectra and the tantalum resonances are presented. Beam properties and fluxes at ISIS are discussed. Features of the proposed detectors suitable for the temperature technique are outlined, along with the data analysis, the moving targets, the cyclic temperature variations and transients, and the usefulness of the technique. (U.K.)

Gadolinium-enhanced magnetic resonance imaging in acute myocardial infarction

International Nuclear Information System (INIS)

Dijkman, P.R.M. van; Wall, E.E. van der; Roos, A. de; Doornbos, J.; Laarse, A. van der; Voorthuisen, A.E. van; Bruschke, A.V.G.; Rossum, A.C. van

1990-01-01

To evaluate he usefulness of the paramagnetic contrast agent Gadolinium-DTPA (diethylenetriaminepentaacetic acid) in Magnetic Resonance. Imaging of acute myocardial infarction, we studied a total of 45 patients with a first acute myocardial infarction by ECG-gated magnetic resonance imaging before and after intravenous administration of 0.1 mmol/kg Gadolinium-DTPA. All patients received thrombolytic treatment by intravenous streptokinase. The magnetic resonance imaging studies were preformed after a meam of 88 h (range 15-241) after the acute onset of acute myocardial infarction. Five patients without evidence of cardiac disease served as controls. Spin-echo measurements (TE 30 ms) were made using a Philips Gyroscan (0.5 Tesla) or a Teslacon II (0.6 Tesla). The 45 patients were divided into four groups of patients. In Group I( patients) Gadolinium-DTPA improved the detection of myocardial infarction by Gadolinium-DTPA. In Group II (20 patients) the magnetic resonance imaging procedure was repeated every 10 min for up to 40 min following administration of Gadolinium-DTPA. Optimal contrast enhancement was obtained 20-25 min after Gadolinium-DTPA. In Group III (27 patients) signal intensities were significantly higher in the patients who underwent the magnetic resonance imaging study more than 72 h (mean 120) after the acute event, suggesting increased acculumation of Gadolinium-DTPA in a more advanced stage of the infarction process. In Group IV (45 patients) Gadolinium-DTPA was administered in an attempt to distinguish between reperfused and nonreperfused myocardial areas after thrombolytic treatment for acute myocardial infarction. The signal intensities did not differ, but reperfused areas showed a more homogeneous aspect whereas nonreperfused areas were visualized as a more heterogeneous contrast enhancement. It is concluded that magnetic resonance imaging using the contrast agent Gadolinium-DTPA significantly improves the detection of infarcted myocardial areas

Direct evidence for inelastic neutron 'acceleration' by 177Lum

International Nuclear Information System (INIS)

Roig, O.; Meot, V.; Rosse, B.; Belier, G.; Daugas, J.-M.; Morel, P.; Letourneau, A.; Menelle, A.

2011-01-01

The inelastic neutron acceleration cross section on the long-lived metastable state of 177 Lu has been measured using a direct method. High-energy neutrons have been detected using a specially designed setup placed on a cold neutron beam extracted from the ORPHEE reactor in Saclay. The 146±19 b inelastic neutron acceleration cross section in the ORPHEE cold neutron flux confirms the high cross section for this process on the 177 Lu m isomer. The deviation from the 258±58 b previously published obtained for a Maxwellian neutron flux at a 323 K temperature could be explained by the presence of a low energy resonance. Resonance parameters are deduced and discussed.

Multilevel resonance parameters of 241Pu

International Nuclear Information System (INIS)

Weston, L.W.; Todd, J.H.

1978-01-01

The data previously reported by the authors on the neutron fission and capture cross sections of 241 Pu were simultaneously fit with the Adler formalism to obtain multilevel resonance parameters. The neutron energy range of the fit was 0.01 to 100 eV. The 241 Pu cross sections in the resonance region of neutron energies are complex, and the Adler parameters present an efficient method of representing these cross sections, which are important for plutonium-fueled reactors. The parameters represent the data to an accuracy within the quoted experimental errors. 5 figures, 2 tables

The Resonance Integral of Gold

Energy Technology Data Exchange (ETDEWEB)

Jirlow, K; Johansson, E

1959-04-15

The resonance activation integral of gold has been determined, by means of cadmium ratio measurements of thin foils in a neutron beam. Comparison was made with a 1/v detector, and the neutron spectra were measured with a chopper. The resonance integral, RI, is defined as {integral}{sub 0.5}{sup {infinity}}{sigma}{sub r}(E)dE/E, where {sigma}{sub r}(E) is the differenc between the total absorption cross section and the 1/v part. An experimental value of 1490 {+-} 40 barns has been obtained. RI has also been computed from resonance parameter data with the result 1529 {+-} 70 barns.

Interaction of magnetic resonators studied by the magnetic field enhancement

Directory of Open Access Journals (Sweden)

Yumin Hou

2013-12-01

Full Text Available It is the first time that the magnetic field enhancement (MFE is used to study the interaction of magnetic resonators (MRs, which is more sensitive than previous parameters–shift and damping of resonance frequency. To avoid the coherence of lattice and the effect of Bloch wave, the interaction is simulated between two MRs with same primary phase when the distance is changed in the range of several resonance wavelengths, which is also compared with periodic structure. The calculated MFE oscillating and decaying with distance with the period equal to resonance wavelength directly shows the retardation effect. Simulation also shows that the interaction at normal incidence is sensitive to the phase correlation which is related with retardation effect and is ultra-long-distance interaction when the two MRs are strongly localized. When the distance is very short, the amplitude of magnetic resonance is oppressed by the strong interaction and thus the MFE can be much lower than that of single MR. This study provides the design rules of metamaterials for engineering resonant properties of MRs.

Endogenous fields enhanced stochastic resonance in a randomly coupled neuronal network

International Nuclear Information System (INIS)

Deng, Bin; Wang, Lin; Wang, Jiang; Wei, Xi-le; Yu, Hai-tao

2014-01-01

Highlights: • We study effects of endogenous fields on stochastic resonance in a neural network. • Stochastic resonance can be notably enhanced by endogenous field feedback. • Endogenous field feedback delay plays a vital role in stochastic resonance. • The parameters of low-passed filter play a subtle role in SR. - Abstract: Endogenous field, evoked by structured neuronal network activity in vivo, is correlated with many vital neuronal processes. In this paper, the effects of endogenous fields on stochastic resonance (SR) in a randomly connected neuronal network are investigated. The network consists of excitatory and inhibitory neurons and the axonal conduction delays between neurons are also considered. Numerical results elucidate that endogenous field feedback results in more rhythmic macroscope activation of the network for proper time delay and feedback coefficient. The response of the network to the weak periodic stimulation can be notably enhanced by endogenous field feedback. Moreover, the endogenous field feedback delay plays a vital role in SR. We reveal that appropriately tuned delays of the feedback can either induce the enhancement of SR, appearing at every integer multiple of the weak input signal’s oscillation period, or the depression of SR, appearing at every integer multiple of half the weak input signal’s oscillation period for the same feedback coefficient. Interestingly, the parameters of low-passed filter which is used in obtaining the endogenous field feedback signal play a subtle role in SR

Analysis of statistical distributions of partial γ-widths of 98Mo neutron 3 2-resonances

International Nuclear Information System (INIS)

Knat'ko, V.A.; Rudak, Eh.A.; Shimanovich, E.A.

1978-01-01

Width distributions for E1 γ-transitions from the 98 Mo neutron 3/2 resonances to the 99 Mo low-lying levels with 1/2 + , 3/2 2 and 5/2 + spins are desribed. Considered are sets of widths corresponding to γ-transitions to the levels with 3/2 spin and positioned in the energy range from 12 to 5268 eV. On the basis of the results obtained a conclusion has been drawn that the width distribution of γ-transitions to the 3/2 + level differs from the Porter-Thomas distribution

Strong guided mode resonant local field enhanced visible harmonic generation in an azo-polymer resonant waveguide grating.

Science.gov (United States)

Lin, Jian Hung; Tseng, Chun-Yen; Lee, Ching-Ting; Young, Jeff F; Kan, Hung-Chih; Hsu, Chia Chen

2014-02-10

Guided mode resonance (GMR) enhanced second- and third-harmonic generation (SHG and THG) is demonstrated in an azo-polymer resonant waveguide grating (RWG), comprised of a poled azo-polymer layer on top of a textured SU8 substrate with a thin intervening layer of TiO2. Strong SHG and THG outputs are observed by matching either in-coming fundamental- or out-going harmonic-wavelength to the GMR wavelengths of the azo-polymer RWG. Without the azo-polymer coating, pure TiO2 RWGs, do not generate any detectable SHG using a fundamental beam peak intensity of 2 MW/cm(2). Without the textured TiO2 layer, a planar poled azo-polymer layer results in 3650 times less SHG than the full nonlinear RWG structure under identical excitation conditions. Rigorous coupled-wave analysis calculations confirm that this enhancement of the nonlinear conversion is due to strong local electric fields that are generated at the interfaces of the TiO2 and azo-polymer layers when the RWG is excited at resonant wavelengths associated with both SHG and THG conversion processes.

Resonance-enhanced laser-induced plasma spectroscopy for sensitive elemental analysis: Elucidation of enhancement mechanisms

International Nuclear Information System (INIS)

Lui, S.L.; Cheung, N.H.

2002-01-01

When performing laser-induced plasma spectroscopy for elemental analysis, the analyte signal-to-noise ratio increased from four to over fifty if the plume was reheated by a dye laser pulse tuned to resonant absorption. Time-resolved studies showed that the enhancement was not due to resonance photoionization. Rather, efficient and controlled rekindling of a larger plume volume was the key mechanism. The signal-to-noise ratio further increased to over a hundred if the atmosphere was replaced by a low-pressure heavy inert gas. The ambient gas helped confine and thermally insulate the expanding vapor

Neutron transport. Physics and calculation of nuclear reactors with applications to pressurized water reactors and fast neutron reactors. 2 ed.

International Nuclear Information System (INIS)

Bussac, J.; Reuss, P.

1985-01-01

This book presents the main physical bases of neutron theory and nuclear reactor calculation. 1) Interactions of neutrons with matter and basic principles of neutron transport; 2) Neutron transport in homogeneous medium and the neutron field: kinetic behaviour, slowing-down, resonance absorption, diffusion equation, processing methods; 3) Theory of a reactor constituted with homogeneous zones: critical condition, kinetics, separation of variables, calculation and neutron balance of the fundamental mode, one-group and multigroup theories; 4) Study of heterogeneous cell lattices: fast fission factor, resonance absorption, thermal output factor, diffusion coefficient, computer codes; 5) Operation and control of reactors: perturbation theory, reactivity, fuel properties evolution, poisoning by fission products, calculation of a reactor and fuel management; 6) Study of some types of reactors: PWR and fast breeder reactors, the main reactor types of the present French program [fr

Automation on computer of the partial area method in the analysis of resonances induced by 'S' neutrons 2. with an interference term and extension of the method to the treatment of multi resonances (1963); Automatisation sur ordinateur de la methode des aires partielles dans l'analyse des resonances induites par les neutrons ''S''. 2, avec terme d'interference et extension de la methode au traitement des multiresonances (1963)

Energy Technology Data Exchange (ETDEWEB)

Bianchi, G; Corge, C R [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1963-07-01

This report deals with the numerical analysis on an I.B.M. 7090 computer of transmission resonances induced by 's' wave neutrons in time of flight experiments. The analysis method used is the partial area one. In this second part the interference term is taken into account. Modifications have been made in the programs and subroutines described in the first part, to determine the resonant transmissions from experimental raw data, and the relating partial areas. Also programs and subroutines are thoroughly described, which estimate the resonance parameters. The field of the partial area method has been extended to cover the case where several resonances have to be treated simultaneously, provided they do not interfere. (authors) [French] Le pretent rapport a pour objet l'analyse numerique sur ordinateur I.B.M. 7090 des resonances dues aux neutrons ''s'' dans les experiences de transmission par temps de vol, la methode d'analyse utilisee etant la methode dea aires partielles. Dans cette deuxieme partie il a ete tenu compte du terme d'interference. On y trouvera une description des amenagements apportes aux programmes et sous-programmes decrits dans la premiere partie pour determiner les transmissions interfero-resonnantes a partir des donnees experimentales brutes et les aires partielles afferentes. Sont egalement decrits les programmes et sous-programmes necessaires au calcul des parametres caracteristiques des resonances. Le domaine d'application de la methode a ete etendu au traitement simultane de plusieurs resonances groupees n'interferant pas entre elles. (auteurs)

Measurement of the ROT effect in the neutron induced fission of 235U in the 0.3 eV resonance at a hot source of polarized neutrons

Directory of Open Access Journals (Sweden)

Kopatch Yuri

2018-01-01

Full Text Available The TRI and ROT asymmetries in fission of heavy nuclei have been extensively studied during more than a decade. The effects were first discovered in the ternary fission in a series of experiments performed at the ILL reactor (Grenoble by a collaboration of Russian and European institutes, and were carefully measured for a number of fissioning nuclei. Later on, the ROT effect has been observed in the emission of prompt gamma rays and neutrons in fission of 235U and 233U, although its value was an order of magnitude smaller than in the α-particle emission from ternary fission. All experiments performed so far are done with cold polarized neutrons, what assumes a mixture of several spin states, the weights of these states being not well known. The present paper describes the first attempt to get “clean” data by performing the measurement of gamma and neutron asymmetries in an isolated resonance of 235U at the POLI instrument of the FRM2 reactor in Garching.

Neutron Beam Filters

International Nuclear Information System (INIS)

Adib, M.

2011-01-01

The purpose of filters is to transmit neutrons with selected energy, while remove unwanted ones from the incident neutron beam. This reduces the background, and the number of spurious. The types of commonly used now-a-day neutron filters and their properties are discussed in the present work. There are three major types of neutron filters. The first type is filter of selective thermal neutron. It transmits the main reflected neutrons from a crystal monochromate, while reject the higher order contaminations accompanying the main one. Beams coming from the moderator always contain unwanted radiation like fast neutrons and gamma-rays which contribute to experimental background and to the biological hazard potential. Such filter type is called filter of whole thermal neutron spectrum. The third filter type is it transmits neutrons with energies in the resonance energy range (En . 1 KeV). The main idea of such neutron filter technique is the use of large quantities of a certain material which have the deep interference minima in its total neutron cross-section. By transmitting reactor neutrons through bulk layer of such material, one can obtain the quasimonochromatic neutron lines instead of white reactor spectrum.

Neutron radiation capture; Radiatsionnyj zakhvat nejtronov

Energy Technology Data Exchange (ETDEWEB)

NONE

1987-12-31

For all stable and experimentally studied radionuclides evaluated data are presented on cross sections of thermal neutrons, on resonance integrals and medium neutron cross sections with energy of 30 KeV. Refs, figs and tabs.

Oxygen enhancement ratio as a function of neutron energy with mammalian cells in culture

International Nuclear Information System (INIS)

Rini, F.J.; Hall, E.J.; Marino, S.A.

1979-01-01

Chinese hamster cells (V79) in culture under oxic and hypoxic conditions were irradiated with several neutron beams spanning a wide energy range to determine the oxygen enhancement ratio (OER). Eight essentially monoenergetic neutron beams, ranging from 0.22 to 13.6 MeV and a 0.11-MeV neutron spectrum, were produced at the Radiological Research Accelerator Facility (RARAF) at Brookhaven National Laboratory. Additional experiments were performed at the Naval Research Laboratory, Washington, DC, where neutrons are produced for radiotherapy by bombarding a beryllium target with 35-MeV deuterons. This beam has a broad energy spectrum with a mean energy of about 15 MeV. A maximum OER of about 1.9 was observed for 13.6-MeV neutrons. The OER values of the monoenergetic neutrons decreased with energy, plateaued at about 1.45 for the energy range from 0.22 to 2.0 MeV and increased slightly to about 1.55 for lower energy spectrum. In the light of microdosimetric data obtained for the neutron beams at RARAF, the OER appears to depend primarily on the intermediate-LET secondaries produced by neutrons in tissue, such as protons, while in contrast high LET-secondaries, such as α-particles and recoil ions, play a minor role. The studies using the NRL neutron beam resulted in a lower OER of about 1.67 as compared to the monoenergetic 13.6-MeV beam. This is a consequence of the fact that more of the dose is deposited by intermediate LET secondaries for the NRL neutron beam

Measurement of resonance parameters of cross-sections affecting fast-neutron propagation in various media; Mesure des parametres de resonance de sections efficaces lies a la propagation des neutrons dans differents milieux; Izmerenie parametrov rezonansnoj struktury sechenij, vliyayushchikh na rasprostranenie bystrykh nejtronov v sredakh; Medicion de los parametros de resonancia de las secciones eficaces que afectan a la propagacion de los neutrones rapidos en distintos medios

Energy Technology Data Exchange (ETDEWEB)

Nikolaev, M N; Filippov, V V; Bondarenko, I I [Academy of Sciences, Moscow, Union of Soviet Socialist Republics (Russian Federation)

1962-03-15

In compiling a system of multi-group constants for fast- and intermediate-reactor calculations, it is frequently necessary to account for the self-shielding effect associated with the resonance structure of the cross-sections. The energy region in which the resonance structure has a considerable influence on neutron propagation in the material extends up to several decades of kilo-electron- volts for heavy nuclei and to several mega-electron-volts for intermediate nuclei. To compute resonance effects in calculating group parameters, it is essential to know not only the average interaction cross-sections between neutrons and materials, but also values such as (1/{Sigma}{sub t}), (1/{Sigma}{sub t}{sup 2}), etc. - the brackets signify averaging over the energy group. Present information about resonance parameters for fast neutrons is not sufficient to calculate these values with the necessary precision. In this connection it is interesting to take direct measurements of the values (1/{Sigma}{sub t}), (1/{Sigma}{sub t}{sup 2}) and other analogous characteristics. The paper describes the results obtained from measurements of a number of parameters such as ({Sigma}{sub t}), ({Sigma}{sub t}{sup 2}), (1/{Sigma}{sub t}), (1/{Sigma}{sub t}{sup 2}), (1/{Sigma}{sub t}{sup 3}), etc. which characterize the cross-section structure of a number of intermediate nuclei within the range from 300 keV to 3 MeV. These values were arrived at by an analysis of transmission curves obtained by good geometry for transmissions up to {approx}10{sup -2}. The data show that resonance effects exercise a strong influence on the diffusion characteristics of the material. (author) [French] Lorsqu'on etablit un systeme de constantes multi-groupes pour les calculs de reacteurs a neutrons rapides et intermediaires, il est souvent necessaire de tenir compte de l'effet d'auto-protectio n lie a la structure de resonance des sections efficaces. Le domaine d'energie dans lequel la structure de resonance a

Fundamental of neutron radiography and the present of neutron radiography in Japan

International Nuclear Information System (INIS)

Sekita, Junichiro

1988-01-01

Neutron radiography refers to the application of transmitted neutrons to analysis. In general, thermal neutron is used for neutron radiography. Thermal neutron is easily absorbed by light atoms, including hydrogen, boron and lithium, while it is not easily absorbed by such heavy atoms as tungsten, lead and uranium, permitting detection of impurities in heavy metals. Other neutrons than thermal neutron can also be applied. Cold neutron is produced from fast neutron using a moderator to reduce its energy down to below that of thermal neutron. Cold neutron is usefull for analysis of thick material. Epithermal neutron can induce resonance characteristic of each substance. With a relatively small reaction area, fast neutron permits observation of thick samples. Being electrically neutral, neutrons are difficult to detect by direct means. Thus a substance that releases charged particles is put in the path of neutrons for indirect measurement. X-ray film combined with converter screen for conversion of neutrons to charge particles is placed behind the sample. Photographing is carried out by a procedure similar to X-ray photography. Major institues and laboratories in Japan provided with neutron radiography facilities are listed. (Nogami, K.)

Enhanced resonant second harmonic generation in plasma based on density transition

Directory of Open Access Journals (Sweden)

Kant Niti

2015-06-01

Full Text Available Resonant second harmonic generation of a relativistic self-focusing laser in plasma with density ramp profile has been investigated. A high intense Gaussian laser beam generates resonant second harmonic beam in plasma with density ramp profile. The second harmonic undergoes periodic focusing in the plasma channel created by the fundamental wave. The normalized second harmonic amplitude varies periodically with distance and attains maximum value in the focal region. Enhancement in the second harmonic amplitude on account of relativistic self-focusing of laser based on plasma density transition is seen. Plasma density ramp plays an important role to make self-focusing stronger which leads to enhance the second harmonic generation in plasma.

Array-Enhanced Coherence Resonance: Nontrivial Effects of Heterogeneity and Spatial Independence of Noise

International Nuclear Information System (INIS)

Zhou, Changsong; Kurths, Juergen; Hu, Bambi

2001-01-01

We demonstrate the effect of coherence resonance in a heterogeneous array of coupled Fitz Hugh--Nagumo neurons. It is shown that coupling of such elements leads to a significantly stronger coherence compared to that of a single element. We report nontrivial effects of parameter heterogeneity and spatial independence of noise on array-enhanced coherence resonance; especially, we find that (i) the coherence increases as spatial correlation of the noise decreases, and (ii) inhomogeneity in the parameters of the array enhances the coherence. Our results have the implication that generic heterogeneity and background noise can play a constructive role to enhance the time precision of firing in neural systems

URR [Unresolved Resonance Region] computer code: A code to calculate resonance neutron cross-section probability tables, Bondarenko self-shielding factors, and self-indication ratios for fissile and fertile nuclides

International Nuclear Information System (INIS)

Leal, L.C.; de Saussure, G.; Perez, R.B.

1989-01-01

The URR computer code has been developed to calculate cross-section probability tables, Bondarenko self-shielding factors, and self- indication ratios for fertile and fissile isotopes in the unresolved resonance region. Monte Carlo methods are utilized to select appropriate resonance parameters and to compute the cross sections at the desired reference energy. The neutron cross sections are calculated by the single-level Breit-Wigner formalism with s-, p-, and d-wave contributions. The cross-section probability tables are constructed by sampling the Doppler broadened cross-section. The various shelf-shielded factors are computed numerically as Lebesgue integrals over the cross-section probability tables. 6 refs

Suppression of two-photon resonantly enhanced nonlinear processes in extended media

International Nuclear Information System (INIS)

Garrett, W.R.; Moore, M.A.; Payne, M.G.; Wunderlich, R.K.

1988-11-01

On the basis of combined experimental and theoretical studies of nonlinear processes associated with two-photon excitations near 3d and 4d states in Na, we show how resonantly enhanced stimulated hyper-Raman emission, parametric four-wave mixing processes and total resonant two-photon absorption can become severely suppressed through the actions of internally generated fields on the total atomic response in extended media. 7 refs., 3 figs

Measurement of the ³He Spin Structure Functions in the Resonance Region: A Test of Quark-Hadron Duality on the Neutron

Energy Technology Data Exchange (ETDEWEB)

Solvignon, Patricia [Temple Univ., Philadelphia, PA (United States)

2006-08-01

One of the biggest challenges in the study of the nucleon structure is the understanding of the transition from partonic degrees of freedom to hadronic degrees of freedom. In 1970, Bloom and Gilman noticed that structure function data taken at SLAC in the resonance region average to the scaling curve of deep inelastic scattering (DIS). Early theoretical interpretations suggested that these two very different regimes can be linked under the condition that the quark-gluon and quark-quark interactions are suppressed. Substantial efforts are ongoing to investigate this phenomenon both experimentally and theoretically. Quark-hadron duality has been confirmed for the unpolarized structure function F₂ of the proton and the deuteron using data from the experimental Hall C at Jefferson Lab (JLab). Indications of duality have been seen for the proton polarized structure function g₁ and the virtual photon asymmetry A₁ at JLab Hall B and HERMES. Because of the different resonance behavior, it is expected that the onset of duality for the neutron will happen at lower momentum transfer than for the proton. Now that precise spin structure data in the DIS region are available at large x, data in the resonance region are greatly needed in order to test duality in spin-dependent structure functions. The goal of experiment E01-012 was to provide such data on the neutron (³He) in the moderate momentum transfer (Q²) region, 1.0 < Q² < 4.0 (GeV/c²), where duality is expected to hold. The experiment ran successfully in early 2003 at Jefferson Lab in Hall B. It was an inclusive measurement of longitudinally polarized electrons scattering from a longitudinally or transversely polarized ³He target. Asymmetries and cross section differences were measured in order to extract the ³He spin structure function g₁ and virtual photon asymmetry A₁ in the resonance region. A test

The spectral energy distributions of isolated neutron stars in the resonant cyclotron scattering model

Science.gov (United States)

Tong, Hao; Xu, Renxin

2013-03-01

The X-ray dim isolated neutron stars (XDINSs) are peculiar pulsar-like objects, characterized by their very well Planck-like spectrum. In studying their spectral energy distributions, the optical/UV excess is a long standing problem. Recently, Kaplan et al. (2011) have measured the optical/UV excess for all seven sources, which is understandable in the resonant cyclotron scattering (RCS) model previously addressed. The RCS model calculations show that the RCS process can account for the observed optical/UV excess for most sources. The flat spectrum of RX J2143.0+0654 may due to contribution from bremsstrahlung emission of the electron system in addition to the RCS process.

The optical/ultraviolet excess of isolated neutron stars in the resonant cyclotron scattering model

Science.gov (United States)

Tong, Hao; Xu, Ren-Xin; Song, Li-Ming

2011-12-01

X-ray dim isolated neutron stars are peculiar pulsar-like objects, characterized by their Planck-like spectrum. In studying their spectral energy distributions, optical/ultraviolet (UV) excess is a long standing problem. Recently Kaplan et al. measured the optical/UV excess for all seven sources, which is understandable in the resonant cyclotron scattering (RCS) model previously addressed. The RCS model calculations show that the RCS process can account for the observed optical/UV excess for most sources. The flat spectrum of RX J2143.0+0654 may be due to contributions from the bremsstrahlung emission of the electron system in addition to the RCS process.

$\\beta$-decay study of neutron-rich Tl, Pb, and Bi by means of the pulsed-release technique and resonant laser ionisation

CERN Multimedia

Lettry, J

2002-01-01

It is proposed to study new neutron-rich nuclei around the Z = 82 magic shell closure, with major relevance for understanding the evolution of nuclear structure at extreme isospin values. Following the IS354 experiment, $\\beta$-decay studies of neutron-rich thallium, lead and bismuth isotopes will be performed for 215 $\\leqslant$ A $\\leqslant$ 219. To this purpose the pulsed-release technique, which was pioneered at ISOLDE, will be optimised. It will be complemented with the higher element selectivity that can be obtained by the unique features of resonant laser ionisation, available at ISOLDE from the RILIS source.

Dipole-dipole dispersion interactions between neutrons

OpenAIRE

Babb, James F.; Higa, Renato; Hussein, Mahir S.

2016-01-01

We investigate the long-range interactions between two neutrons utilizing recent data on the neutron static and dynamic electric and magnetic dipole polarizabilities. The resulting long-range potentials are used to make quantitative comparisons between the collisions of a neutron with a neutron and a neutron with a proton. We also assess the importance of the first pion production threshold and first excited state of the nucleon, the $\\Delta$-resonance ($J^{\\pi}$ = + 3/2, I = 3/2). We found b...

Decay properties of the key resonant states in 8Li(α,n)11B for primordial nucleosynthesis

International Nuclear Information System (INIS)

Kubono, S.; Ikeda, N.; Tanaka, M.H.; Nomura, T.; Katayama, I.; Fuchi, Y.; Kawashima, H.; Kajino, T.

1991-01-01

The particle decay property of the key resonant states in the reaction 8 Li(α, n) 11 B for the inhomogeneous big bang models was studied experimentally. The sum of the branching ratios of the 10.572 MeV state for the neutron decays to the excited states in 11 B is as large as for the ground state, indicating that the neutron decays to excited states are crucial and enhance the reaction rate for heavy element synthesis considerably. (orig.)

Opportunities for TRIGA reactors in neutron radiography

International Nuclear Information System (INIS)

Barton, John P.

1978-01-01

In this country the two most recent installations of TRIGA reactors have both been for neutron radiography, one at HEDL and the other at ANL. Meanwhile, a major portion of the commercial neutron radiography is performed on a TRIGA fueled reactor at Aerotest. Each of these installations has different primary objectives and some comparative observations can be drawn. Another interesting comparison is between the TRIGA reactors for neutron radiography and other small reactors that are being installed for this purpose such as the MIRENE slow pulse reactors in France, a U-233 fueled reactor for neutron radiography in India and the L88 solution reactor in Denmark. At Monsanto Laboratory, in Ohio, a subcritical reactor based on MTR-type fuel has recently been purchased for neutron radiography. Such systems, when driven by a Van de Graaff neutron source, will be compared with the standard TRIGA reactor. Future demands on TRIGA or competitive systems for neutron radiography are likely to include the pulsing capability of the reactor, and also the extraction of cold neutron beams and resonance energy beams. Experiments recently performed on the Oregon State TRIGA Reactor provide information in each of these categories. A point of particular current concern is a comparison made between the resonance energy beam intensity extracted from the edge of the TRIGA core and from a slot which penetrated to the center of the TREAT reactor. These results indicate that by using such slots on a TRIGA, resonance energy intensities could be extracted that are much higher than previously predicted. (author)

Production of narrowband tunable extreme-ultraviolet radiation by noncollinear resonance-enhanced four-wave mixing

NARCIS (Netherlands)

Hannemann, S.; Hollenstein, U.; van Duijn, E.J.; Ubachs, W.M.G.

2005-01-01

Fourier-transform-limited extreme-ultraviolet (XUV) radiation (bandwidth ≲300 MHz) tunable around 91 nm is produced by use of two-photon resonance-enhanced four-wave mixing on the Kr resonance at 94 093 cm

Physical particularities of nuclear reactors using heavy moderators of neutrons

Energy Technology Data Exchange (ETDEWEB)

Kulikov, G. G., E-mail: ggkulikov@mephi.ru; Shmelev, A. N. [National Research Nuclear University MEPhI (Moscow Engineering Physics Institute) (Russian Federation)

2016-12-15

In nuclear reactors, thermal neutron spectra are formed using moderators with small atomic weights. For fast reactors, inserting such moderators in the core may create problems since they efficiently decelerate the neutrons. In order to form an intermediate neutron spectrum, it is preferable to employ neutron moderators with sufficiently large atomic weights, using {sup 233}U as a fissile nuclide and {sup 232}Th and {sup 231}Pa as fertile ones. The aim of the work is to investigate the properties of heavy neutron moderators and to assess their advantages. The analysis employs the JENDL-4.0 nuclear data library and the SCALE program package for simulating the variation of fuel composition caused by irradiation in the reactor. The following main results are obtained. By using heavy moderators with small neutron moderation steps, one is able to (1) increase the rate of resonance capture, so that the amount of fertile material in the fuel may be reduced while maintaining the breeding factor of the core; (2) use the vacant space for improving the fuel-element properties by adding inert, strong, and thermally conductive materials and by implementing dispersive fuel elements in which the fissile material is self-replenished and neutron multiplication remains stable during the process of fuel burnup; and (3) employ mixtures of different fertile materials with resonance capture cross sections in order to increase the resonance-lattice density and the probability of resonance neutron capture leading to formation of fissile material. The general conclusion is that, by forming an intermediate neutron spectrum with heavy neutron moderators, one can use the fuel more efficiently and improve nuclear safety.

Physical particularities of nuclear reactors using heavy moderators of neutrons

International Nuclear Information System (INIS)

Kulikov, G. G.; Shmelev, A. N.

2016-01-01

In nuclear reactors, thermal neutron spectra are formed using moderators with small atomic weights. For fast reactors, inserting such moderators in the core may create problems since they efficiently decelerate the neutrons. In order to form an intermediate neutron spectrum, it is preferable to employ neutron moderators with sufficiently large atomic weights, using "2"3"3U as a fissile nuclide and "2"3"2Th and "2"3"1Pa as fertile ones. The aim of the work is to investigate the properties of heavy neutron moderators and to assess their advantages. The analysis employs the JENDL-4.0 nuclear data library and the SCALE program package for simulating the variation of fuel composition caused by irradiation in the reactor. The following main results are obtained. By using heavy moderators with small neutron moderation steps, one is able to (1) increase the rate of resonance capture, so that the amount of fertile material in the fuel may be reduced while maintaining the breeding factor of the core; (2) use the vacant space for improving the fuel-element properties by adding inert, strong, and thermally conductive materials and by implementing dispersive fuel elements in which the fissile material is self-replenished and neutron multiplication remains stable during the process of fuel burnup; and (3) employ mixtures of different fertile materials with resonance capture cross sections in order to increase the resonance-lattice density and the probability of resonance neutron capture leading to formation of fissile material. The general conclusion is that, by forming an intermediate neutron spectrum with heavy neutron moderators, one can use the fuel more efficiently and improve nuclear safety.

Interaction of neutrons with the matter in the laser field

International Nuclear Information System (INIS)

Zaretskij, D.F.; Lomonosov, V.V.

1980-01-01

The interactions of neutrons with the molecules, atoms and nuclei in the presence of the coherent electromagnetic radiation are considered. There are two effects which are discussed in detail: 1) the ''acceleration'' of thermal neutrons passed through the excited by the resonance laser wave molecular gas; 2) the induced by the laser field the slow neutron capture accompanied by the compound nucleus level excitation. The given effects, if they are experimentally detected, give the possibility to control the neutron flux (spectrum change, polarization, spatial modulation and etc.) and change the interaction cross sections of thermal and resonance neutrons with nuclei due to excitation of p levels of the compound nucleus [ru

High-temperature superconductors, as seen through the eyes of neutrons

Directory of Open Access Journals (Sweden)

Z. Yamani

2006-09-01

Full Text Available   Neutron scattering is proved to be a vital probe in unveiling the magnetic properties of high temperature superconductors (HTSC. Detailed information about the energy and momentum dependence of the magnetic dynamics of HTSC have been obtained directly by this technique. Over the past decade by improving the crystal growth methods, large and high quality single crystals of HTSC, which are essential for a neutron scattering experiment, have become available. The results of neutron scattering measurements on such crystals have considerably enhanced our understanding of the magnetism in HTSC both in the superconducting (SC and normal states. In this review, the neutron scattering results on two main HTSC families, La2-xSrxCuO4 (LSCOx and YBa2CuO3O6+x (YBCO6+x, are considered with an emphasis on the most prominent properties of these materials that are now widely accepted. These include the presence of strong antiferromagnetic (AF fluctuations even in optimally doped region of the phase diagram, neutron resonance peak that scales with SC transition temperature, Tc, incommensurate magnetic fluctuations (stripes, and a pseudogap in the normal state of underdoped materials.

Enhancement of the Accelerating Gradient in Superconducting Microwave Resonators

Energy Technology Data Exchange (ETDEWEB)

Checchin, Mattia [Fermilab; Grassellino, Anna [Fermilab; Martinello, Martina [IIT, Chicago; Posen, Sam [Fermilab; Romanenko, Alexander [Fermilab; Zasadzinski, John [IIT, Chicago (main)

2017-05-01

The accelerating gradient of superconducting resonators can be enhanced by engineering the thickness of a dirty layer grown at the cavity's rf surface. In this paper the description of the physics behind the accelerating gradient enhancement by meaning of the dirty layer is carried out by solving numerically the the Ginzburg-Landau (GL) equations for the layered system. The calculation shows that the presence of the dirty layer stabilizes the Meissner state up to the lower critical field of the bulk, increasing the maximum accelerating gradient.

Mid-Infrared Tunable Resonant Cavity Enhanced Detectors

Directory of Open Access Journals (Sweden)

Hans Zogg

2008-09-01

Full Text Available Mid-infrared detectors that are sensitive only in a tunable narrow spectral band are presented. They are based on the Resonant Cavity Enhanced Detector (RCED principle and employing a thin active region using IV-VI narrow gap semiconductor layers. A Fabry-Pérot cavity is formed by two mirrors. The active layer is grown onto one mirror, while the second mirror can be displaced. This changes the cavity length thus shifting the resonances where the detector is sensitive. Using electrostatically actuated MEMS micromirrors, a very compact tunable detector system has been fabricated. Mirror movements of more than 3 μm at 30V are obtained. With these mirrors, detectors with a wavelength tuning range of about 0.7 μm have been realized. Single detectors can be used in mid-infrared micro spectrometers, while a detector arrangement in an array makes it possible to realize Adaptive Focal Plane Arrays (AFPA.

Reflection of neutrons from a helicoidal system

International Nuclear Information System (INIS)

Aksenov, V.L.; Ignatovich, V.K.; Nikitenko, Yu.V.

2006-01-01

Analytical solution for neutron reflection and transmission of magnetic mirrors with helicoidal magnetization is found. The dependence of neutron speed of reflection and transmission curves is shown. Resonant properties of helicoidal systems are found

Cadmium-Zinc-Telluride photon detector for epithermal neutron spectroscopy--pulse height response characterisation

International Nuclear Information System (INIS)

Tardocchi, M.; Pietropaolo, A.; Andreani, C.; Bracco, A.; D'Angelo, A.; Gorini, G.; Imberti, S.; Senesi, R.; Rhodes, N.J.; Schooneveld, E.M.

2004-01-01

The Resonance Detector Spectrometer was recently revised for neutron spectroscopic studies in the eV energy region. In this technique one makes use of a photon detector to record the gamma emission from analyser foils used as neutron-gamma converters. The pulse-height response of a Cadmium-Zinc-Telluride photon detector to neutron capture emission from 238 U and 197 Au analyser foils was characterised in the neutron energy range 1-200 eV. The experiment was performed on the VESUVIO spectrometer at the ISIS neutron-pulsed source. A biparametric data acquisition, specifically developed for these measurements, allowed the simultaneous measurements of both the neutron time of flight and γ pulse-height spectra. Through the analysis of the γ pulse-height spectra the main components of the signal associated with resonant and non-resonant neutron absorption were identified. It was also shown that, in principle, energy discrimination can be used to improve the signal to background ratio of the neutron time-of-flight measurement

CFRMF neutron flux gradient and spectral determinations

International Nuclear Information System (INIS)

Rogers, J.W.; Turk, E.H.; Hogg, C.H.

1976-01-01

Recently more accurate and complete measurements of the flux gradient have been measured by the activation of 235 U and Au samples. Neutron spectrum characteristics were studied by making activation measurements with and without the ends of the CFRMF test region plugged with 10 B. These measurements define the flux gradient to +-1 to 2% and indicate there is no detectable streaming of thermal or resonance neutrons from the ends in the central 30 cm of the CFRMF test region. Measurements of the Cd ratio of Au foil activations were conducted and these results also indicate there is no streaming of thermal and resonance neutrons into the CFRMF test region

Methods for Probing Magnetic Films with Neutrons

Science.gov (United States)

Kozhevnikov, S. V.; Ott, F.; Radu, F.

2018-03-01

We review various methods in the investigation of magnetic films with neutrons, including those based on the effects of Larmor precession, Zeeman spatial splitting of the beam, neutron spin resonance, and polarized neutron channeling. The underlying principles, examples of the investigated systems, specific features, applications, and perspectives of these methods are discussed.

Exploring Neutron-Rich Oxygen Isotopes with MoNA

International Nuclear Information System (INIS)

Frank, N.; Gade, A.; Peters, W. A.; Thoennessen, M.; Baumann, T.; Bazin, D.; Lecouey, J.-L.; Scheit, H.; Schiller, A.; Brown, J.; DeYoung, P. A.; Finck, J. E.; Hinnefeld, J.; Howes, R.; Luther, B.

2007-01-01

The Modular Neutron Array (MoNA) was used in conjunction with a large-gap dipole magnet (Sweeper) to measure neutron-unbound states in oxygen isotopes close to the neutron dripline. While no excited states were observed in 24 O, a resonance at 45(2) keV above the neutron separation energy was observed in 23 O

Resonantly Enhanced Axion-Photon Regeneration

CERN Document Server

Sikivie, P; Van Bibber, K; Bibber, Karl van

2007-01-01

We point out that photon regeneration-experiments that search for the axion, or axion-like particles, may be resonantly enhanced by employing matched Fabry-Perot optical cavities encompassing both the axion production and conversion magnetic field regions. Compared to a simple photon regeneration experiment, which uses the laser in a single-pass geometry, this technique can result in a gain in rate of order ${\\cal F}^2$, where ${\\cal F}$ is the finesse of the cavities. This gain could feasibly be $10^{(10-12)}$, corresponding to an improvement in sensitivity in the axion-photon coupling, $g_{a\\gamma\\gamma}$ , of order ${\\cal F}^{1/2} \\sim 10^{(2.5-3)}$, permitting a practical purely laboratory search to probe axion-photon couplings not previously excluded by stellar evolution limits, or solar axion searches.

Spallation Neutron Source Drift Tube Linac Resonance Control Cooling System Modeling

CERN Document Server

Tang, Johnny Y; Champion, Marianne M; Feschenko, Alexander; Gibson, Paul; Kiselev, Yuri; Kovalishin, A S; Kravchuk, Leonid V; Kvasha, Adolf; Schubert, James P

2005-01-01

The Resonance Control Cooling System (RCCS) for the warm linac of the Spallation Neutron Source was designed by Los Alamos National Laboratory. The primary design focus was on water cooling of individual component contributions. The sizing the RCCS water skid was accomplished by means of a specially created SINDA/FLUINT model tailored to these system requirements. A new model was developed in Matlab Simulink and incorporates actual operational values and control valve interactions. Included is the dependence of RF input power on system operation, cavity detuning values during transients, time delays that result from water flows through the heat exchanger, the dynamic process of water warm-up in the cooling system due to dissipated RF power on the cavity surface, differing contributions on the cavity detuning due to drift tube and wall heating, and a dynamic model of the heat exchanger with characteristics in close agreement to the real unit. Because of the Matlab Simulink model, investigation of a wide range ...

Measurements of Relative Biological Effectiveness and Oxygen Enhancement Ratio of Fast Neutrons of Different Energies

Energy Technology Data Exchange (ETDEWEB)

Barendsen, G. W.; Broerse, J. J. [Radiobiological Institute of the Health Research Council TNO, Rijswijk (ZH) (Netherlands)

1968-03-15

Impairment of the reproductive capacity of cultured cells of human kidney origin (T-l{sub g} cells) has been measured by the Puck cloning technique. From the dose-survival curves obtained in these experiments by irradiation of cells in equilibrium with air and nitrogen, respectively, the relative biological effectiveness (RBE) and the oxygen enhancement ratios (OER) were determined for different beams of fast neutrons. Monoenergetic neutrons of 3 and 15 MeV energy, fission spectrum fast neutrons (mean energy about 1.5 MeV), neutrons produced by bombarding Be with cyclotron-accelerated 16 MeV deuterons (mean energy about 6 MeV) and neutrons produced by bombarding Be with cyclotron- accelerated 20 MeV {sup 3}He ions (mean energy about 10 MeV) have been compared with 250 kVp X-rays as a standard reference. The RBE for 50% cell survival varies from 4.7 for fission-spectrum fast neutrons to 2.7 for 15 MeV monoenergetic neutrons. The OER is not strongly dependent on the neutron energy for the various beams investigated. For the neutrons with the highest and lowest energies used OER values of 1.6 {+-} 0.2 and 1.5 {+-} 0.1 were measured. An interpretation of these data on the basis of the shapes of the LET spectra is proposed and an approximate verification of this hypothesis is provided from measurements in which secondary particle equilibrium was either provided for or deliberately eliminated. (author)

Confident Diagnosis of Bronchobiliary Fistula Using Contrast-Enhanced Magnetic Resonance Cholangiography

Energy Technology Data Exchange (ETDEWEB)

Karabulut, Nevzat; Cakmak, Vefa; Kiter, Go ksel [Pamukkale University Medical Center, Denizli (Turkmenistan)

2010-08-15

We report the utility of contrast-enhanced magnetic resonance cholangiography (MRC) using gadoxetic acid (Gd-EOB-DTPA) in the diagnosis of bronchobiliary fistula associated with liver hydatid cyst. Contrast-enhanced MRC clearly delineated the leakage of contrast agent from the biliary duct and its communication with the bronchial tree. Providing functional information about physiologic or pathologic biliary flow in addition to the display of biliary anatomy, contrast enhanced MRC stands as a robust technique in confidently detecting bronchobiliary fistula and bile leaks

Boron neutron capture therapy (BNCT) using fast neutrons: Effects in two human tumor cell lines

International Nuclear Information System (INIS)

Sauerwein, W.; Ziegler, W.; Szypniewski, H.; Streffer, C.

1990-01-01

The results demonstrate that the effect of fast neutrons on cell survival in cell culture can be enhanced by boron neutron capture reaction. Even with lower enhancement ratios, the concept of NCT assisted fast neutron therapy may successfully be applied for tumor treatment with the Essen cyclotron. (orig.)

The perturbation of backscattered fast neutrons spectrum caused by the resonances of C, N and O for possible use in pyromaterial detection

Energy Technology Data Exchange (ETDEWEB)

Abedin, Ahmad Firdaus Zainal, E-mail: firdaus087@gmail.com; Ibrahim, Noorddin; Zabidi, Noriza Ahmad; Abdullah, Abqari Luthfi Albert [Department of Defence Science, Universiti Pertahanan Nasional Malaysia, Kem Sungai Besi, Kuala Lumpur 57000 (Malaysia)

2015-04-29

Neutron radiation is able to determine the signature of land mine detection based on backscattering energy spectrum of landmine. In this study, the Monte Carlo simulation of backscattered fast neutrons was performed on four basic elements of land mine; hydrogen, nitrogen, oxygen and carbon. The moderation of fast neutrons to thermal neutrons and their resonances cross-section between 0.01 eV until 14 MeV were analysed. The neutrons energies were divided into 29 groups and ten million neutrons particles histories were used. The geometries consist of four main components: neutrons source, detectors, landmine and soil. The neutrons source was placed at the origin coordinate and shielded with carbon and polyethylene. Americium/Beryllium neutron source was placed inside lead casing of 1 cm thick and 2.5 cm height. Polyethylene was used to absorb and disperse radiation and was placed outside the lead shield of width 10 cm and height 7 cm. Two detectors were placed between source with distance of 8 cm and radius of 1.9 cm. Detectors of Helium-3 was used for neutron detection as it has high absorption cross section for thermal neutrons. For the anomaly, the physical is in cylinder form with radius of 10 cm and 8.9 cm height. The anomaly is buried 5 cm deep in the bed soil measured 80 cm radius and 53.5 cm height. The results show that the energy spectrum for the four basic elements of landmine with specific pattern which can be used as indication for the presence of landmines.

The perturbation of backscattered fast neutrons spectrum caused by the resonances of C, N and O for possible use in pyromaterial detection

International Nuclear Information System (INIS)

Abedin, Ahmad Firdaus Zainal; Ibrahim, Noorddin; Zabidi, Noriza Ahmad; Abdullah, Abqari Luthfi Albert

2015-01-01

Neutron radiation is able to determine the signature of land mine detection based on backscattering energy spectrum of landmine. In this study, the Monte Carlo simulation of backscattered fast neutrons was performed on four basic elements of land mine; hydrogen, nitrogen, oxygen and carbon. The moderation of fast neutrons to thermal neutrons and their resonances cross-section between 0.01 eV until 14 MeV were analysed. The neutrons energies were divided into 29 groups and ten million neutrons particles histories were used. The geometries consist of four main components: neutrons source, detectors, landmine and soil. The neutrons source was placed at the origin coordinate and shielded with carbon and polyethylene. Americium/Beryllium neutron source was placed inside lead casing of 1 cm thick and 2.5 cm height. Polyethylene was used to absorb and disperse radiation and was placed outside the lead shield of width 10 cm and height 7 cm. Two detectors were placed between source with distance of 8 cm and radius of 1.9 cm. Detectors of Helium-3 was used for neutron detection as it has high absorption cross section for thermal neutrons. For the anomaly, the physical is in cylinder form with radius of 10 cm and 8.9 cm height. The anomaly is buried 5 cm deep in the bed soil measured 80 cm radius and 53.5 cm height. The results show that the energy spectrum for the four basic elements of landmine with specific pattern which can be used as indication for the presence of landmines

Measurement of thermal neutron cross section and resonance integral of the reaction {sup 135}Cs(n,{gamma}){sup 136}Cs

Energy Technology Data Exchange (ETDEWEB)

Katoh, Toshio; Nakamura, Shoji; Harada, Hideo [Power Reactor and Nuclear Fuel Development Corp., Tokyo (Japan); Hatsukawa, Yuichi; Shinohara, Nobuo; Hata, Kentaro; Kobayashi, Katsutoshi; Motoishi, Shoji; Tanase, Masakazu

1997-03-01

The thermal neutron(2,200 m/s neutron) capture cross section({sigma}{sub 0}) and the resonance integral(I{sub 0}) of the reaction {sup 135}Cs(n,{gamma}){sup 136}Cs were measured by an activation method. Targets of radioactive cesium, which include {sup 135}Cs, {sup 137}Cs and stable {sup 133}Cs, were irradiated with reactor neutrons within or without a Cd shield case. The ratio of the number of nuclei of {sup 135}Cs to that of {sup 137}Cs was measured with a quadrupole mass spectrometer. This ratio and the ratio of activity of {sup 136}Cs to that of {sup 137}Cs were used for deduction of the {sigma}{sub 0} and the I{sub 0} of {sup 135}Cs. The {sigma}{sub 0} and the I{sub 0} of the reaction {sup 135}Cs(n,{sigma}){sup 136}Cs were 8.3 {+-} 0.3 barn and 38.1 {+-} 2.6 barn, respectively. (author)

Transfer reactions at the neutron dripline with triton target

CERN Multimedia

Two-neutron transfer to $^{9}$Li will populate the ground state of $^{11}$Li as well as low-lying resonances in a way that is complementary to studies of these states performed at higher beam energies. We aim at detecting the charged particles from the transfer reactions as well as neutrons coming from the decay of possible $^{11}$Li resonances.

Transfer reactions at the neutron dripline with triton target

CERN Document Server

Borge, M J G; Fynbo, H O U; Gomez Camacho, J; Johansen, J; Johansson, H T; Jonson, B; Krücken, R; Kurcewicz, J; Martel, I; Moro, A; Mücher, D; Nilsson, T; Nyman, G; Raabe, R; Randisi, G; Riisager, K; Sambi, S; Sanchez-Benitez, AM; Tengblad, O

2012-01-01

Two-neutron transfer to $^{9}$Li will populate the ground state of $^{11}$Li as well as low-lying resonances in a way that is complementary to studies of these states performed at higher beam energies. We aim at detecting the charged particles from the transfer reactions as well as neutrons coming from the decay of possible $^{11}$Li resonances.

Physical basis for prompt-neutron activation analysis

International Nuclear Information System (INIS)

Chrien, R.E.

1982-01-01

The technique called prompt ν-ray neutron activation analysis has been applied to rapid materials analysis. The radiation following the neutron radiation capture is prompt in the sense that the nuclear decay time is on the order of 10 - 15 second, and thus the technique is not strictly activation, but should be called radiation neutron capture spectroscopy or neutron capture ν-ray spectroscopy. This paper reviews the following: sources and detectors, theory of radiative capture, nonstatistical capture, giant dipole resonance, fast neutron capture, and thermal neutron capture ν-ray spectra. 14 figures

Experimental study of time-reversal invariance in neutron-nucleus interactions

International Nuclear Information System (INIS)

Shaparov, E.I.; Shimizu, H.M.

1996-01-01

Experimental approaches for the test of time-reversal invariance in neutron-nucleus interactions are reviewed. Possible transmission experiments with polarized neutron beams and polarized or aligned targets are discussed as well as neutron capture experiments with unpolarized resonance neutrons. 102 refs., 13 figs., 3 tabs

Multipolarity analysis for 14C high-energy resonance populated by (18O,16O) two-neutron transfer reaction

International Nuclear Information System (INIS)

Carbone, D.; Cavallaro, M.; Bondì, M.; Agodi, C.; Cunsolo, A.; Cappuzzello, F.; Azaiez, F.; Franchoo, S.; Khan, E.; Bonaccorso, A.; Fortunato, L.; Foti, A.; Linares, R.; Lubian, J.; Scarpaci, J. A.; Vitturi, A.

2015-01-01

The 12 C( 18 O, 16 O) 14 C reaction at 84 MeV incident energy has been explored up to high excitation energy of the residual nucleus thanks to the use of the MAGNEX spectrometer to detect the ejectiles. In the region above the two-neutron separation energy, a resonance has been observed at 16.9 MeV. A multipolarity analysis of the cross section angular distribution indicates an L = 0 character for such a transition

Neutron capture cross section of ^243Am

Science.gov (United States)

Jandel, M.

2009-10-01

The Detector for Advanced Neutron Capture Experiments (DANCE) at Los Alamos National Laboratory (LANL) was used for neutron capture cross section measurement on ^243Am. The high granularity of DANCE (160 BaF2 detectors in a 4π geometry) enables the efficient detection of prompt gamma-rays following neutron capture. DANCE is located on the 20.26 m neutron flight path 14 (FP14) at the Manuel Lujan Jr. Neutron Scattering Center at the Los Alamos Neutron Science Center (LANSCE). The methods and techniques established in [1] were used for the determination of the ^243Am neutron capture cross section. The cross sections were obtained in the range of neutron energies from 0.02 eV to 400 keV. The resonance region was analyzed using SAMMY7 and resonance parameters were extracted. The results will be compared to existing evaluations and calculations. Work was performed under the auspices of the U.S. Department of Energy at Los Alamos National Laboratory by the Los Alamos National Security, LLC under Contract No. DE-AC52-06NA25396 and at Lawrence Livermore National Laboratory by the Lawrence Livermore National Security, LLC under Contract No. DE-AC52-07NA27344. [4pt] [1] M. Jandel et al., Phys. Rev. C78, 034609 (2008)

Testing neutron cross-section files from the BROND-2 and ENDF/B-6 libraries in benchmark experiments on neutron transmission through spherical layers

International Nuclear Information System (INIS)

Androsenko, A.A.; Androsenko, P.A.; Blokhin, A.I.; Kulagin, N.T.; Pronyaev, V.G.; Simakov, S.P.

1997-01-01

The effect of angular anisotropy in inelastic secondary neutron scattering on neutron leakage spectra from the surface of spherical specimens is investigated. It is shown how inadequate representation of the cross-section structure in the neutron energy resonance region can affect the neutron leakage spectrum. (author). 19 refs, 5 figs, 6 tabs

Testing neutron cross-section files from the BROND-2 and ENDF/B-6 libraries in benchmark experiments on neutron transmission through spherical layers

Energy Technology Data Exchange (ETDEWEB)

Androsenko, A A; Androsenko, P A; Blokhin, A I; Kulagin, N T; Pronyaev, V G; Simakov, S P [Institute of Physics and Power Engineering, Obninsk (Russian Federation)

1997-06-01

The effect of angular anisotropy in inelastic secondary neutron scattering on neutron leakage spectra from the surface of spherical specimens is investigated. It is shown how inadequate representation of the cross-section structure in the neutron energy resonance region can affect the neutron leakage spectrum. (author). 19 refs, 5 figs, 6 tabs.

Prominent porto-systemic collateral pathways in patients with portal hypertension: demonstration by gadolinium-enhanced magnetic resonance angiography

International Nuclear Information System (INIS)

Caldana, Rogerio Pedreschi; Bezerra, Alexandre Araujo Sergio; Cecin, Alexnadre Oliveira; Souza, Luis Ronan Marques Ferreira de; Goldman, Susan Menasce; D'Ippolito, Giuseppe; Szejnfeld, Jacob

2003-01-01

To demonstrate the usefulness of gadolinium-enhanced magnetic resonance angiography in the evaluation of prominent porto-systemic collateral pathways. We reviewed the images from 40 patients with portal hypertension studied with gadolinium-enhanced magnetic resonance angiography and selected illustrative cases of prominent porto-systemic collateral pathways. The scans were performed using high field equipment (1.5 Tesla) and a 3 D volume technique. Image were obtained after intravenous injection of paramagnetic contrast media using a power injector. Magnetic resonance angiography demonstrated with precision the porto-systemic collateral pathways, particularly when investigating extensive territories or large vessels. The cases presented show the potential of this method in the investigation of patients with portal hypertension. Gadolinium-enhanced magnetic resonance angiography is a useful method for the evaluation of patients with portal hypertension and prominent collateral pathways. (author)

Applications of a surveillance and diagnostics methodology using neutron noise from a pressurized-water reactor

International Nuclear Information System (INIS)

Wood, R.T.; Miller, L.F.; Perez, R.B.

1992-01-01

Two applications of a noise diagnostic methodology were performed with ex-core neutron detector data from a pressurized-water reactor (PWR). A feedback dynamics model of the neutron power spectral denisty was derived from a low-order whole-plant physical model made stochastic with the Langevin technique. From a functional fit to plant data, the response of the dynamic system to changes in important physical parameters was evaluated by a direct sensitivity analysis. In addition, changes in monitored spectra were related to changes in physical parameters, and detection thresholds using common surveillance discriminants were determined. A resonance model was developed from perturbation theory to give the ex-core neutron detector response for small in-core mechanical motions in terms of a pole-strength factor, a resonance asymmetry (or skewness) factor, a vibration damping factor, and a frequency of vibration. The mechanical motion paramters for several resonances were determined by a functional fit of the model to plant data taken at various times during a fuel cycle and were tracked to determined trends that indicated vibrational changes of reactor internals. In addition, the resonance model gave the ability to separate the resonant components of the power spectral density after the parameters had been identified. As a result, the behavior of several vibration peaks was monitored over a fuel cycle. The noise diagnostic methodology illustrated by these applications can be used in monitoring the condition of the reactor system. Early detection of degraded mechanical components or undesirable operating conditions by using such surveillance and diagnostic techniques would enhance plant safety. 15 refs., 6 figs., 1 tab

Nanoantennas for surface enhanced infrared spectroscopy: Effects of interaction and higher order resonant excitations

Directory of Open Access Journals (Sweden)

J. Aizpurua

2011-09-01

Full Text Available The sensitivity in surface enhanced infrared spectroscopy (SEIRS strongly depends on where the resonant excitation is spectrally located compared to the molecular vibration that is to be enhanced. In this contribution, we study the effect of coupling in the electromagnetic properties of 2D gold nanorod arrays in the IR. We also study the SEIRS activity of higher order resonant excitations in long nanoantennas to identify polaritonic signals of a supporting SiO2 layer with nanometer thickness (3 nm on a silicon substrate.

Hard X ray lines from neutron stars

Energy Technology Data Exchange (ETDEWEB)

Polcaro, V.F.; Bazzano, A.; La Padula, C.; Ubertini, P.

1982-01-01

Experimental evidence is presented and evaluated concerning the features of the hard X-ray spectra detected in a number of cosmic X-ray sources which contain a neutron star. The strong emission line at cyclotron resonance detected in the spectrum of Her XI at an energy of 58 keV is evaluated and the implications of this finding are discussed. Also examined is the presence of spectral features in the energy range 20-80 keV found in the spectra of gamma-ray bursts, which have been interpreted as cyclotron resonance from interstellar-gas-accreting neutron stars. The less understood finding of a variable emission line at approximately 70 keV in the spectrum of the Crab Pulsar is considered. It is determined that several features varying with time are present in the spectra of cosmic X-ray sources associated with neutron stars. If these features are due to cyclotron resonance, it is suggested that they provide a direct measurement of neutron star magnetic fields on the order of 10 to the 11th-10 to the 13th Gauss. However, the physical condition of the emitting region and its geometry are still quite obscure.

Neutron capture reactions on Lu isotopes at DANCE

CERN Document Server

Roig, O

2010-01-01

The DANCE (Detector for Advanced Neutron Capture Experiments) array located at the Los Alamos national laboratory has been used to obtain the neutron capture cross sections for 175Lu and 176Lu with neutron energies from thermal up to 100 keV. Both isotopes are of current interest for the nucleosynthesis s-process in astrophysics and for applications as in reactor physics or in nuclear medicine. Three targets were used to perform these measurements. One was natLu foil and the other two were isotope-enriched targets of 175Lu and 176Lu. The cross sections are obtained for now through a precise neutron flux determination and a normalization at the thermal neutron cross section value. A comparison with the recent experimental data and the evaluated data of ENDF/B-VII.0 will be presented. In addition, resonances parameters and spin assignments for some resonances will be featured.

The optimization of scan timing for contrast-enhanced magnetic resonance angiography

International Nuclear Information System (INIS)

Lee, Jong Min; Chang, Yong Min; Ryeom, Hun Kyu; Lee, Sang Kwon; Kim, Yong Sun; Kang, Duk Sik; Tirman, Philip J.

2000-01-01

To determine the optimal scan timing for contrast-enhanced magnetic resonance angiography and to evaluate a new timing method based on the arteriovenous circulation time. Eighty-nine contrast-enhanced magnetic resonance angiographic examinations were performed mainly in the extremities. A 1.5T scanner with a 3-D turbo-FLASH sequence was used, and during each study, two consecutive arterial phases and one venous phase were acquired. Scan delay time was calculated from the time-intensity curve by the traditional (n = 48) and/or the new (n = 41) method. This latter was based on arteriovenous circulation time rather than peak arterial enhancement time, as used in the traditional method. The numbers of first-phase images showing a properly enhanced arterial phase were compared between the two methods. Mean scan delay time was 5.4 sec longer with the new method than with the traditional. Properly enhanced first-phase images were found in 65% of cases (31/48) using the traditional timing method, and 95% (39/41) using the new method. When cases in which there was mismatch between the target vessel and the Time-intensity curve acquisition site are excluded, erroneous acquisition occurred in seven cases with the traditional method, but in none with the new method. The calculation of scan delay time on the basis of arteriovenous circulation time provides better timing for arterial phase acquisition than the traditional method

Dynamic optical bistability in resonantly enhanced Raman generation

International Nuclear Information System (INIS)

Novikova, I.; Phillips, D.F.; Zibrov, A.S.; Andre, A.; Walsworth, R.L.

2004-01-01

We report observations of novel dynamic behavior in resonantly enhanced stimulated Raman scattering in Rb vapor. In particular, we demonstrate a dynamic hysteresis of the Raman scattered optical field in response to changes of the drive laser field intensity and/or frequency. This effect may be described as a dynamic form of optical bistability resulting from the formation and decay of atomic coherence. We have applied this phenomenon to the realization of an all-optical switch

Epithermal neutron activation analysis using a boron carbide irradiation filter

International Nuclear Information System (INIS)

Ehmann, W.D.; Brueckner, J.

1980-01-01

The use of boron carbide as a thermal neutron filter in epithermal neutron activation (ENAA) analysis has been investigated. As compared to the use of a cadmium filter, boron provides a greater reduction of activities from elements relatively abundant in terrestrial rocks and fossil fuels, such as Na, La, Sc and Fe. These elements have excitation functions which follow the 1/v law in the 1 to 10 eV lower epithermal region. This enhances the sensitivity of ENAA for elements such as U, Th, Ba and etc. which have strong resonances in the higher epithermal region above 10 eV. In addition, a boron carbide filter has the advantages over cadmium of acquiring a relatively low level of induced activity which poses minimal radiation safety problems, when used for ENAA. (author)

Expectations for neutrons as microscopic probes

International Nuclear Information System (INIS)

Date, M.

1993-01-01

Neutrons have been used as microscopic probes to study structural and dynamical properties of various materials. In this paper I shall give a comparative study of the neutron research in the condensed matter physics with other typical microscopic methods such as X-rays, laser optics, magnetic resonances, Moessbauer effect and μSR. It is emphasized that the neutron study will extensively be important in future beyond the condensed matter physics. Chemistry, biology, earth sciences, material engineerings and medical sciences will become new frontiers for neutron study. (author)

Electric and magnetic dipole moments of the neutron

International Nuclear Information System (INIS)

Ramsey, N.F.

1977-01-01

Experiments to measure the electric and magnetic dipole moments of the neutron are described. The apparatus used in this experiment is one to measure with high precision the precessional frequency of the neutron spin in a weak magnetic field with a neutron beam magnetic resonance apparatus similar to that used for measuring the magnetic moment of the neutron. Results of the measurement are presented. 52 references

Development of a D-D Neutron Generator

International Nuclear Information System (INIS)

Kim, In Jung; Jung, Hwa Dong; Park, Chang Su; Jung, Nam Suk; Jung, Soon Wook; Hwang, Y. S.; Choi, H. D.

2007-01-01

To enhance neutron yield, the ion source of the D-D neutron generator is replaced by a large current helicon plasma ion source. Current and energy of deuteron beam are increased, and hence neutron yield is enhanced. The maximum neutron yield is 2x10 8 n/s

Travelling-wave resonant four-wave mixing breaks the limits of cavity-enhanced all-optical wavelength conversion.

Science.gov (United States)

Morichetti, Francesco; Canciamilla, Antonio; Ferrari, Carlo; Samarelli, Antonio; Sorel, Marc; Melloni, Andrea

2011-01-01

Wave mixing inside optical resonators, while experiencing a large enhancement of the nonlinear interaction efficiency, suffers from strong bandwidth constraints, preventing its practical exploitation for processing broad-band signals. Here we show that such limits are overcome by the new concept of travelling-wave resonant four-wave mixing (FWM). This approach combines the efficiency enhancement provided by resonant propagation with a wide-band conversion process. Compared with conventional FWM in bare waveguides, it exhibits higher robustness against chromatic dispersion and propagation loss, while preserving transparency to modulation formats. Travelling-wave resonant FWM has been demonstrated in silicon-coupled ring resonators and was exploited to realize a 630-μm-long wavelength converter operating over a wavelength range wider than 60 nm and with 28-dB gain with respect to a bare waveguide of the same physical length. Full compatibility of the travelling-wave resonant FWM with optical signal processing applications has been demonstrated through signal retiming and reshaping at 10 Gb s(-1).

[Summary talk for the fourth international symposium on neutron induced reactions

International Nuclear Information System (INIS)

Raman, S.

1985-01-01

Comments are made on presentations on these topics: how the mean field theories account for average nuclear properties determined by the dynamics of the system and how the fluctuations about this average can be simulated in terms of a Hamiltonian consisting of a Gaussian orthogonal ensemble; a full Hamiltonian consisting of at least nine terms; multi-step direct reaction theory; the verification of the hypothesis of an E1 giant resonance built on every excited state of the nucleus; neutron resonance averaging; level density of compound resonances; unequal parity distribution to explain the gamma competition in the continuum of 56 Fe; a survey of the most recent measurements of (n,p) and n,α) reactions with thermal and resonance neutrons; and data indicating a hard component of fission neutrons from 252 Cf

Pursuing nuclear energy with no nuclear contamination - from neutron flux reactor to deuteron flux reactor

International Nuclear Information System (INIS)

Li, X. Z.; Wei, Q. M.; Liu, B.; Zhu, X. G.; Ren, S. L.

2007-01-01

Pursuing nuclear energy with no nuclear contamination has been a long endeavor since the first fission reactor in 1942. Four major concepts have been the key issues: i.e. resonance, negative feed back, self-sustaining, nuclear radiation. When nuclear energy was just discovered in laboratory, the key issue was to enlarge it from the micro-scale to the macro-scale. Slowing-down the neutrons was the key issue to enhance the fission cross-section in order to build-up the neutron flux through the chain-reactions using resonance between neutron and fissile materials. Once the chain-reaction was realized, the negative feed-back was the key issue to keep the neutron flux at the allowable level. The negative reaction coefficient was introduced by the thermal expansion, and the resonant absorption in cadmium or boron was used to have a self-sustaining fission reactor with neutron flux. Then the strong neutron flux became the origin of all nuclear contamination, and a heavy shielding limits the application of the nuclear energy. The fusion approach to nuclear energy was much longer; nevertheless, it evolved with the similar issues. The resonance between deuteron and triton was resorted to enlarge the fusion cross section in order to keep a self-sustaining hot plasma. However, the 14 MeV neutron emission became the origin of all nuclear contamination again. Deuteron plus helium-3 fusion reaction was proposed to avoid neutron emission although there are two more difficulties: the helium-3 is supposed to be carried back from the moon; and much more higher temperature plasma has to be confined while 50 years needed to realized the deuteron-triton plasma already. Even if deuteron plus helium-3 fusion plasma might be realized in a much higher temperature plasma, we still have the neutron emission from the deuteron-deuteron fusion reaction in the deuteron plus helium-3 fusion plasma. Polarized deuteron-deuteron fusion reaction was proposed early in 1980's to select the neutron

Resonant tunneling of UCN through the moving interference filter and experimental test of the UCN dispersion law

International Nuclear Information System (INIS)

Frank, A.I.; Bondarenko, I.V.; Balashov, S.N.; Geltenbort, P.; Hoghoj, P.; Kozlov, A.V.; Masalovich, S.V.; Toperverg, B.P.

2004-01-01

With the aim to test experimentally the dispersion law validity for very slow neutrons a spectrum of ultracold neutrons (UCN) under the condition of resonance tunneling through the moving Neutron Interference Filter was investigated. The neutron spectrum in this case has a narrow width resonance, whose parameters depend on the filter characteristics and dispersion law of neutron waves in matter. For a number of samples a noticeable shift of the resonance position when the filter moved parallel to its surface was detected. This shift is in strong contradiction with the commonly accepted dispersion law. Further investigations have shown that the spectrum of tunneling neutrons is not exactly defined by the solution of one-dimensional quantum problem, but substantially affected by neutron scattering from filter imperfections. The cross section of this scattering depends on the neutron wave number and increases dramatically in resonance conditions. Experimental results as well as comprehensive theoretical analysis have led us to the unambiguous conclusion that observed phenomena of the resonance shift in a moving sample are caused by scattering of neutron tunneling states rather than by a deviation from the commonly accepted dispersion law. (author)

Neutron-induced Fission Cross Sections of Am and Cm isotopes (Final Report of Research Contract 14485). Resonance and Fast Neutron Induced Fission Cross Sections of Americium and Curium Nuclides (Third-year Progress Report of Research Contract 14485)

International Nuclear Information System (INIS)

Alekseev, A.A.; Bergman, A.A.; Berlev, A.I.; Koptelov, E.A.; Egorov, A.S.; Samylin, B.F.; Trufanov, A.M.; Fursov, B.I.; Shorin, V.S.

2012-01-01

The neutron induced fission cross sections of Am and Cm isotopes were measured relative to 239 Pu in the neutron energy range from 1 eV to 20 keV at the INR RAS lead slowing down spectrometer LSDS-100. The fission resonance integrals were also estimated using the measured cross section data. The results have been compared with the available experimental and evaluated data. This analysis has shown the present status of the measured fission cross sections and the necessity to revise the evaluated cross sections libraries for the minor actinides. (author)

Determination of neutron cross sections and resonance parameters for vanadium, the stable thallium isotopes, and the stable tellurium isotopes. Progress report, October 1, 1976--October 31, 1977

International Nuclear Information System (INIS)

Winters, R.R.

1977-10-01

The analysis of the neutron capture cross section data for 51 V + n has now been completed up to 215 keV. Using a few neutron widths and spin and parity assignments from the literature, the capture data has yielded estimates of radiative widths for 45 s-wave resonances and capture areas for 139 resonances. Of particular interest is the very large s-wave radiative widths for this reaction and the rather broad distribution of radiative widths. A paper describing these results is included with this report. The analysis of the neutron capture cross sections for the reaction 205 Tl(n,γ) is presently being extended to incident neutron energy 115 keV. The study of the scattered-beam sensitivity of the total energy detectors at the ORELA capture facility continues. This small but troublesome effect has now been parameterized, but the errors to be assigned to the parameterization are not yet well defined. However, in obtaining additional data for the parameterization, a series of 208 Pb(n,γ) cross section measurements were made. The analysis of these data led to results important in understanding stellar nucleosynthesis and are reported in a paper included with this report. the analysis of the Te(n,γ) data proceeds methodically but slowly

Neutron methods for the direct determination of the magnetic induction in thick films

Energy Technology Data Exchange (ETDEWEB)

Kozhevnikov, S.V., E-mail: kozhevn@nf.jinr.ru [Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, 141980 Dubna (Russian Federation); Ott, F. [CEA, IRAMIS, Laboratoire Léon Brillouin, F-91191 Gif sur Yvette (France); CNRS, IRAMIS, Laboratoire Léon Brillouin, F-91191 Gif sur Yvette (France); Radu, F. [Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein Strasse 15, D-12489 Berlin (Germany)

2016-03-15

We review different neutron methods which allow extracting directly the value of the magnetic induction in thick films: Larmor precession, Zeeman spatial beam-splitting and neutron spin resonance. Resulting parameters obtained by the neutron methods and standard magnetometry technique are presented and compared. The possibilities and specificities of the neutron methods are discussed. - Highlights: • We present neutron methods for investigations of the thick magnetic films. • It is the methods for the direct determination of the magnetic induction. • Magnetic induction in bulk, at single interface and in a single domain. • It is Larmor precession, Zeeman spatial beam-splitting and neutron spin resonance. • These methods are complementary to polarized neutron reflectometry.

Non-contrast enhanced magnetic resonance angiography techniques in candidates for kidney transplantation: A comparative study

International Nuclear Information System (INIS)

Blankholm, Anne Dorte; Ginnerup-Pedersen, Bodil; Stausbøl-Grøn, Brian; Haislund, Margit; Laustsen, Sussie; Ringgaard, Steffen

2013-01-01

Aim: Detailed knowledge of vessel status in potential candidates for kidney transplantation is essential for the surgeon. Contrast enhanced magnetic resonance angiography has previously been used intensively for assessing this, but the discovery that use of gadolinium based contrast agents in magnetic resonance imaging can cause Nephrogenic Systemic Fibrosis in patients suffering from severe kidney disease has lead to renewed interest in non-contrast enhanced magnetic resonance angiography. The aim of this study was to find a non-contrast enhanced magnetic resonance angiography method for preoperative evaluation of the pelvic vessels prior to kidney transplantation, providing a sufficient image quality. Method: In a prospective study we consecutively included 54 patients undergoing examinations prior to kidney transplantation. The patients were examined with the following magnetic resonance angiography sequences: A 2D Time of flight (n = 54), 3D Time of flight (n = 52) patients, 3D Phase Contrast (n = 54), 3D Balanced Steady State Free Precession (n = 52) and a 2D TRiggered Angiography Non-Contrast Enhanced (TRANCE) (a Spin Echo sequence with subtraction) (n = 48). The sequences were evaluated with respect to contrast, diagnostic performance and artefact burden. Results: Evaluating contrast, 3D Phase Contrast was significantly better than 2D Time of flight (p 0.2). The 2D Time of flight was significantly better than the other sequences (p < 0.001) in all cases. The artefact score was lowest for the Phase Contrast images and significantly superior to the 2D Time of flight (p < 0.005). The 2D Time of flight was significantly better than the three other sequences (p < 0.001) in all cases. Conclusion: Non-contrast enhanced magnetic resonance angiography offers a safe preoperative examination for assessment of vessel status before kidney transplantation. A combination of 2D Time of flight and 3D Phase Contrast acquisitions is recommended and can be performed within a

Resonant cavity enhanced light harvesting in flexible thin-film organic solar cells

KAUST Repository

Sergeant, Nicholas P.

2013-04-24

Dielectric/metal/dielectric (DMD) electrodes have the potential to significantly increase the absorption efficiency and photocurrent in flexible organic solar cells. We demonstrate that this enhancement is attributed to a broadband cavity resonance. Silver-based semitransparent DMD electrodes with sheet resistances below 10 ohm/sq. are fabricated on flexible polyethylene terephthalate (PET) substrates in a high-throughput roll-to-roll sputtering tool. We carefully study the effect of the semitransparent DMD electrode (here composed of ZnxSnyOz/Ag/InxSn yOz) on the optical device performance of a copper phthalocyanine (CuPc)/fullerene (C60) bilayer cell and illustrate that a resonant cavity enhanced light trapping effect dominates the optical behavior of the device. © 2013 Optical Society of America.

Gadolinium-DTPA-enhanced magnetic resonance imaging and functional outcome in patients with acute myocardial infarction

International Nuclear Information System (INIS)