Articles de revues : « Neutrino ma »

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Giaré, William, Eleonora Di Valentino, Alessandro Melchiorri et Olga Mena. « New cosmological bounds on hot relics : axions and neutrinos ». Monthly Notices of the Royal Astronomical Society 505, n^o 2 (21 mai 2021) : 2703–11. http://dx.doi.org/10.1093/mnras/stab1442.

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ABSTRACT Axions, if realized in nature, can be copiously produced in the early universe via thermal processes, contributing to the mass-energy density of thermal hot relics. In light of the most recent cosmological observations, we analyse two different thermal processes within a realistic mixed hot dark matter scenario which includes also massive neutrinos. Considering the axion–gluon thermalization channel, we derive our most constraining bounds on the hot relic masses ma < 7.46 eV and ∑mν < 0.114 eV both at 95 per cent CL; while studying the axion–pion scattering, without assuming any specific model for the axion–pion interactions, and remaining in the range of validity of the chiral perturbation theory, our most constraining bounds are improved to ma < 0.91 eV and ∑mν < 0.105 eV, both at 95 per cent CL. Interestingly, in both cases, the total neutrino mass lies very close to the inverted neutrino mass ordering prediction. If future terrestrial double beta decay and/or long-baseline neutrino experiments find that the nature mass ordering is the inverted one, this could rule out a wide region in the currently allowed thermal axion window. Our results therefore, strongly support multi messenger searches of axions and neutrino properties, together with joint analyses of their expected sensitivities.

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Vermeesch, Pieter, Martin Rittner, Irene Schimmelpfennig, Lucilla Benedetti et ASTER Team. « Determining erosion rates in Allchar (Macedonia) to revive the lorandite neutrino experiment ». Proceedings of the Royal Society A : Mathematical, Physical and Engineering Sciences 474, n^o 2213 (mai 2018) : 20170470. http://dx.doi.org/10.1098/rspa.2017.0470.

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205 Tl in the lorandite (TiAsS 2 ) mine of Allchar (Majdan, FYR Macedonia) is transformed to 205 Pb by cosmic ray reactions with muons and neutrinos. At depths of more than 300 m, muogenic production would be sufficiently low for the 4.3 Ma old lorandite deposit to be used as a natural neutrino detector. Unfortunately, the Allchar deposit currently sits at a depth of only 120 m below the surface, apparently making the lorandite experiment technically infeasible. We here present 25 erosion rate estimates for the Allchar area using in situ produced cosmogenic 36 Cl in carbonates and 10 Be in alluvial quartz. The new measurements suggest long-term erosion rates of 100–120 m Ma −1 in the silicate lithologies that are found at the higher elevations of the Majdanksa River valley, and 200–280 m Ma −1 in the underlying marbles and dolomites. These values indicate that the lorandite deposit has spent most of its existence at depths of more than 400 m, sufficient for the neutrinogenic 205 Pb component to dominate the muon contribution. Our results suggest that this unique particle physics experiment is theoretically feasible and merits further development.

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Forero, D. V. « Neutrino predictions in a modified Babu-Ma-Valle model ». Journal of Physics : Conference Series 447 (24 juillet 2013) : 012042. http://dx.doi.org/10.1088/1742-6596/447/1/012042.

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Kitabayashi, Teruyuki, et Naoto Koizumi. « Remark on Majorana CP phases in neutrino mixing and leptogenesis ». Modern Physics Letters A 29, n^o 16 (25 mai 2014) : 1450087. http://dx.doi.org/10.1142/s0217732314500874.

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We estimate Majorana CP phases for a simple flavor neutrino mixing matrix which has been reported by Qu and Ma. Sizes of Majorana CP phases are evaluated in the study of the neutrinoless double beta decay and a particular leptogenesis scenario. We find the dependence of the physically relevant Majorana CP phase on the mass of lightest right-handed neutrino in the minimal seesaw model and the effective Majorana neutrino mass which is related with the half-life of the neutrinoless double beta decay.

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LAVOURA, L., et H. KÜHBÖCK. « PREDICTIONS OF AN A4 MODEL WITH A FIVE-PARAMETER NEUTRINO MASS MATRIX ». Modern Physics Letters A 22, n^o 03 (30 janvier 2007) : 181–89. http://dx.doi.org/10.1142/s0217732307022608.

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Winklehner, Daniel, Janet Conrad, Joseph Smolsky, Loyd Waites et Philip Weigel. « New Commissioning Results of the MIST-1 Multicusp Ion Source ». Journal of Physics : Conference Series 2244, n^o 1 (1 avril 2022) : 012013. http://dx.doi.org/10.1088/1742-6596/2244/1/012013.

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Abstract For the sterile neutrino experiment IsoDAR (Isotope Decay-At-Rest), we have developed a compact particle accelerator system delivering a 10 mA, continuous wave (cw) proton beam at 60 MeV to a neutrino production target. The accelerator comprises a compact isochronous cyclotron, an RFQ embedded in the cyclotron yoke, and an ion source. To reduce space charge effects during injection and acceleration, we are accelerating H+ 2 instead of protons. To produce the needed cw H+ 2 beam current of 10 mA (nominal) at the required purity and quality, we have built a new filament driven, multicusp ion source (MIST-1). Here we report commissioning results for long-time running at reduced power, demonstrating the feasibility of the design. Highlights include an H+ 2 beam current density of ≈ 10 mA/cm2, ≈ 80% H+ 2 fraction, and extrapolated emittances of 0.05 π-mm-mrad (RMS, normalized) after extraction. We also present high fidelity simulations that are in good qualitative and quantitative agreement with emittance measurements in our test beam line.

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D'Eramo, Francesco, Eleonora Di Valentino, William Giarè, Fazlollah Hajkarim, Alessandro Melchiorri, Olga Mena, Fabrizio Renzi et Seokhoon Yun. « Cosmological bound on the QCD axion mass, redux ». Journal of Cosmology and Astroparticle Physics 2022, n^o 09 (1 septembre 2022) : 022. http://dx.doi.org/10.1088/1475-7516/2022/09/022.

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Abstract We revisit the joint constraints in the mixed hot dark matter scenario in which both thermally produced QCD axions and relic neutrinos are present. Upon recomputing the cosmological axion abundance via recent advances in the literature, we improve the state-of-the-art analyses and provide updated bounds on axion and neutrino masses. By avoiding approximate methods, such as the instantaneous decoupling approximation, and limitations due to the limited validity of the perturbative approach in QCD that forced to artificially divide the constraints from the axion-pion and the axion-gluon production channels, we find robust and self-consistent limits. We investigate the two most popular axion frameworks: KSVZ and DFSZ. From Big Bang Nucleosynthesis (BBN) light element abundances data we find for the KSVZ axion ΔN eff < 0.31 and an axion mass bound ma < 0.53 eV (i.e., a bound on the axion decay constant fa > 1.07 × 107 GeV) both at 95% CL. These BBN bounds are improved to Δ N eff < 0.14 and ma < 0.16 eV (fa > 3.56 × 107 GeV) if a prior on the baryon energy density from Cosmic Microwave Background (CMB) data is assumed. When instead considering cosmological observations from the CMB temperature, polarization and lensing from the Planck satellite combined with large scale structure data we find Δ N eff < 0.23, ma < 0.28 eV (fa > 2.02 × 107 GeV) and ∑ mν < 0.16 eV at 95% CL. This corresponds approximately to a factor of 5 improvement in the axion mass bound with respect to the existing limits. Very similar results are obtained for the DFSZ axion. We also forecast upcoming observations from future CMB and galaxy surveys, showing that they could reach percent level errors for ma ∼ 1 eV.

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OKADA, HIROSHI. « INVESTIGATIONS OF THE FLAVOR SYMMETRY, RADIATIVE SEESAW MODEL AND COLD DARK MATTER ». International Journal of Modern Physics E 16, n^o 05 (juin 2007) : 1541–56. http://dx.doi.org/10.1142/s0218301307006873.

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It is now clear that the masses of the neutrino sector are much lighter than those of the other three sectors. Canonial seesaw model would be the most famous for the above explanation. But one must introduce heavy particles that will not be able to observed with present scientific technologies. On the other hand, there are many attempts to explain the neutrino masses radiatively by means of inert Higgses, which do not have the vacuum expectation values. Then one can discuss cold dark matter candidates, because of no needing so heavy particles. The most famous work would be the Zee model17. Recently a new type model (hep-ph/0601225)4 along this line of thought was proposed by E. Ma. We adopted this idea, and then we introduced a new flavor symmetry to constrain the Yukawa sector. So our model might be more predictive, and can be investigated at LHC. I will present how we can obserb the particular signal at LHC, and what we can predict about the neutrino sector.

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MA, ERNEST. « SUPERSYMMETRIC A4×Z3 AND A4 REALIZATIONS OF NEUTRINO TRIBIMAXIMAL MIXING WITHOUT AND WITH CORRECTIONS ». Modern Physics Letters A 22, n^o 02 (20 janvier 2007) : 101–6. http://dx.doi.org/10.1142/s0217732307022505.

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In an improved application of the tetrahedral symmetry A4 first introduced by Ma and Rajasekaran, supplemented by the discrete symmetry Z3 as well as supersymmetry, a two-parameter form of the neutrino mass matrix is derived which exhibits the tribimaximal mixing of Harrison, Perkins and Scott. This form is the same as the one obtained previously by Altarelli and Feruglio, and the inverse of that obtained by Babu and He. If only A4 is used, then corrections appear, making tan2 θ12 different from 0.5, without changing significantly sin22θ23 from one or θ13 from zero.

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Jimbo, Kouichi, Toshiyuki Shirai, Ka-Ngo Leung et Karl van Bibber. « Proposal for a compact neutron generator based on a negative deuterium ion beam ». Journal of Physics : Conference Series 2420, n^o 1 (1 janvier 2023) : 012035. http://dx.doi.org/10.1088/1742-6596/2420/1/012035.

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Abstract Interest in high intensity generators of neutrons for basic and applied science has been growing, and thus the demand for an economical neutron generator has been growing. A major driver for the development of high intensity neutron generators are studies of neutron disturbance in integrated circuits, for which a compact generator that can be easily accommodated in an ordinary size lab would be highly desirable. We have investigated possible designs for neutron generators based on the D-D fusion reaction, which produce direction dependent mono-energetic neutrons with carry-off energy larger than 2.45 MeV. Specifically, we find a negative deuterium ion beam most attractive for this application, and plan to construct such a system with a negative deuterium ion beam of 200 keV energy and 100 mA current as a prototype of this concept.

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Khorasanov, Georgiy, Dmitriy Samokhin, Aleksandr Zevyakin, Yevgeniy Zemskov et Anatoliy Blokhin. « Lead reactor of small power with metallic fuel ». Nuclear Energy and Technology 4, n^o 2 (26 novembre 2018) : 99–102. http://dx.doi.org/10.3897/nucet.4.30527.

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The possibility for obtaining a hard neutron spectrum in small reactor cores has been considered. A harder spectrum than spectra in known fast sodium cooled and molten salt reactors has been obtained thanks to the selection of relatively small core dimensions and the use of metallic fuel and natural lead (natPb) coolant. The calculations for these compositions achieve an increased average neutron energy and a large fraction of hard neutrons in the spectrum (with energies greater than 0.8 MeV) caused by a minor inelastic interaction of neutrons with the fuel with no light chemical elements and with the coolant containing 52.3% of 208Pb, a low neutron-moderating isotope. An interest in creating reactors with a hard neutron spectrum is explained by the fact that such reactors can be practically used as special burners of minor actinides (MA), and as isotope production and research reactors with new consumer properties. With uranium oxide fuel (UO2) substituted by metallic uranium-plutonium fuel (U-Pu-Zr), the reactors under consideration have the average energy of neutrons and the fraction of hard neutrons increasing from 0.554 to 0.724 MeV and from 18 to 28% respectively. At the same time, the one-group fission cross-section of 241Am increases from 0.359 to 0.536 barn, while the probability of the 241Am fission increases from 22 to 39%. It is proposed that power-grade plutonium resulting from regeneration of irradiated fuel from fast sodium cooled power reactors be used as part of the fuel for future burner reactors. It contains unburnt plutonium isotopes and some 1% of MAs which transmutate into fission products in the process of being reburnt in a harder spectrum. This will make it possible to reduce the MA content in the burner reactor spent fuel and to facilitate so the long-term storage conditions for high-level nuclear waste in dedicated devices.

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Kumada, Hiroaki, Susumu Tanaka, Fujio Naito, Toshikazu Kurihara, Takashi Sugimura, Hideyuki Sakurai, Akira Matsumura et Takeji Sakae. « Neutron beam performance of iBNCT as linac-based neutron source for boron neutron capture therapy ». EPJ Web of Conferences 231 (2020) : 01003. http://dx.doi.org/10.1051/epjconf/202023101003.

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The linac-based neutron source “iBNCT” developed by the Tsukuba team has been shown to generate a large intensity of neutrons. To confirm the applicability of the device to BNCT, several characteristic measurements have been implemented. In a water phantom experiment, when the accelerator was operated with an average current of 1.4 mA, the maximum thermal neutron flux was approximately 7.8 × 108 (cm-2s-1). From estimation of the stability of the linac, the results demonstrate its applicability to actual treatment.

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Taskaev, Sergey, Evgenii Berendeev, Marina Bikchurina, Timofey Bykov, Dmitrii Kasatov, Iaroslav Kolesnikov, Alexey Koshkarev et al. « Neutron Source Based on Vacuum Insulated Tandem Accelerator and Lithium Target ». Biology 10, n^o 5 (21 avril 2021) : 350. http://dx.doi.org/10.3390/biology10050350.

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A compact accelerator-based neutron source has been proposed and created at the Budker Institute of Nuclear Physics in Novosibirsk, Russia. An original design tandem accelerator is used to provide a proton beam. The proton beam energy can be varied within a range of 0.6–2.3 MeV, keeping a high-energy stability of 0.1%. The beam current can also be varied in a wide range (from 0.3 mA to 10 mA) with high current stability (0.4%). In the device, neutron flux is generated as a result of the 7Li(p,n)7Be threshold reaction. A beam-shaping assembly is applied to convert this flux into a beam of epithermal neutrons with characteristics suitable for BNCT. A lot of scientific research has been carried out at the facility, including the study of blistering and its effect on the neutron yield. The BNCT technique is being tested in in vitro and in vivo studies, and the methods of dosimetry are being developed. It is planned to certify the neutron source next year and conduct clinical trials on it. The neutron source served as a prototype for a facility created for a clinic in Xiamen (China).

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Nishitani, Takeo, Sachiko Yoshihashi, Yuuki Tanagami, Kazuki Tsuchida, Shogo Honda, Atsushi Yamazaki, Kenichi Watanabe, Yoshiaki Kiyanagi et Akira Uritani. « Neutronics Analyses of the Radiation Field at the Accelerator-Based Neutron Source of Nagoya University for the BNCT Study ». Journal of Nuclear Engineering 3, n^o 3 (13 juillet 2022) : 222–32. http://dx.doi.org/10.3390/jne3030012.

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The Nagoya University Accelerator-driven Neutron Source (NUANS) is an accelerator-based neutron source by 7Li(p,n)7Be reaction with a 2.8 MeV proton beam up to 15 mA. The fast neutrons are moderated and shaped to beam with a Beam Shaping Assembly (BSA). NUANS is aiming at the basic study of the Boron Neutron Capture Therapy (BNCT) such as an in vitro cell-based irradiation experiment using a water phantom. Moreover, the BSA is developed as a prototype of one for human treatment. We have evaluated the radiation field of NUANS by a Monte Carlo code PHITS. It is confirmed that the radiation characteristics at the BNCT outlet meet the requirement of IAEA TECDOC-1223. Additionally, the radiation field in the water phantom located just in front of the BSA outlet is calculated. In the in vitro irradiation experiment, the boron dose of 30 Gy-eq, which is the dose to kill tumor cells, is expected for 20 min of irradiation at the beam current of 15 mA.

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Sadighzadeh, A., A. Salehizadeh, M. Mohammadzadeh, F. Shama, S. Setayeshi, S. A. H. Feghhi, S. M. Sadati, M. Rezaei, E. Haji Ebrahimi et G. H. Roshani. « Prediction of Neutron Yield of IR-IECF Facility in High Voltages Using Artificial Neural Network ». Journal of Engineering 2014 (2014) : 1–7. http://dx.doi.org/10.1155/2014/798160.

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Artificial neural network (ANN) is applied to predict the number of produced neutrons from IR-IECF device in wide discharge current and voltage ranges. Experimentally, discharge current from 20 to 100 mA had been tuned by deuterium gas pressure and cathode voltage had been changed from −20 to −82 kV (maximum voltage of the used supply). The maximum neutron production rate (NPR) of 1.46 × 107 n/s had occurred when the voltage was −82 kV and the discharge current was 48 mA. The back-propagation algorithm is used for training of the proposed multilayer perceptron (MLP) neural network structure. The obtained results show that the proposed ANN model has achieved good agreement with the experimental data. Results show that NPR of 1.855 × 108 n/s can be achieved in voltage and current of 125 kV and 45 mA, respectively. This prediction shows 52% increment in maximum voltage of power supply. Also, the optimum discharge current can increase 1270% NPR.

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Muraz, Jean-François, Daniel Santos, Véronique Ghetta, Julien Giraud, Julien Marpaud, Marine Hervé, Pascal Sortais et Mauro Forlino. « Development of a regenerated Beryllium target and a thermal test facility for Compact Accelerator-based Neutron Sources ». EPJ Web of Conferences 231 (2020) : 03003. http://dx.doi.org/10.1051/epjconf/202023103003.

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Recently, the possibility to use compact accelerators coupled to high current ion sources for the production of intense low energy proton or deuteron beams has motivated many research laboratories to develop accelerator based neutrons sources for several purposes, including Neutron Capture Therapy (NCT). The NCT needs a high flux, about 10 9 n.cm-2.s-1, of thermal neutrons (E<10 keV) at the tumour site. Up to now, the NCT required neutron flux was mainly delivered by nuclear reactors. However, the production of such neutron flux is now possible using proton or deuteron beams on specific targets able to stand a high pow er (~15- 30 kW) on a small area (~10 cm2). This specific target design, materials and supports, has to cope with extreme physical constraints . The LPSC team has conceived an original solution formed by a thin (8 μm) rotating beryllium target depos ited on a graphite wheel and coupled with a beryllium sputtering device for periodic 9Be layer restoration. By means of 9Be (d,n) 10B nuclear reaction, this target irradiated by a 10- -20 mA deuteron beam (1.45 MeV) should produce the required neutron flux. In order to validate the target design of the neutron flux production and the beryllium target thermal capabilities, we built a 30 cm diameter rotating Beryllium target prototype and a compact electron beam line able to deliver a power density of 3kW/cm2.

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Schmidt, A., C. Goyon, A. Link, C. Cooper, E. Anaya, M. Anderson, G. Bartolo et al. « Measuring characteristic differences between high- and low-performing discharges on the MegaJOuLe Neutron Imaging Radiography (MJOLNIR) DPF ». Physics of Plasmas 29, n^o 6 (juin 2022) : 062708. http://dx.doi.org/10.1063/5.0089121.

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A dense plasma focus (DPF) is a compact coaxial plasma gun, which completes its discharge as a Z-pinch, producing short (<100 ns) pulses of ions, x rays, and/or neutrons. Lawrence Livermore National Laboratory recently constructed and began operating a new device, the MJOLNIR (MegaJOuLe Neutron Imaging Radiography) DPF, which is designed for single-pulse flash neutron radiography. This device has achieved neutron yields of up to 4.1 × 1011 neutrons/pulse at 3.3 MA peak current, and higher-current commissioning is under way. Like most DPFs, MJOLNIR exhibits variable yields in some configurations. We present evidence of the role of parasitic current paths within the gun in stochastically influencing the yield. First through “conditioning shots,” where new hardware has been introduced, we show that increased run-down and run-in speeds correlate with higher yields. These observations are consistent with current being delivered to the electrodes but not to the main plasma sheath, degrading the implosion-driving force. Once nominal conditions are established, we correlate low-performing discharges with smaller current dip and associated voltage spike for a fixed machine configuration. A snow-plow model is able to recreate small-magnitude current dips through the introduction of a parasitic current path, and particle-in-cell simulations establish how parasitic current paths lower the ion beam energy available to produce neutrons. Finally, we observe an increased likelihood of shots with low yield and smaller current dip with increasing fill pressure.

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BYSTRITSKY, V. M., V. M. GREBENYUK, S. S. PARZHITSKI, F. M. PEN'KOV, V. T. SIDOROV, V. A. STOLUPIN, T. L. BULGAKOV et al. « Experimental investigation of dd reaction in range of ultralow energies using Z-pinch ». Laser and Particle Beams 18, n^o 2 (avril 2000) : 325–33. http://dx.doi.org/10.1017/s0263034600182230.

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Experimental results on measurement of dd-reaction cross sections in the energy range of 0.1–1.5 keV using the Z-pinch technique are presented. The experiment was fulfilled at the high current generator of the High-Current Electronics Institute, city of Tomsk, Russia. The dd-fusion neutrons were registered by time-of-flight scintillator detectors and BF3 detectors of thermal neutrons. The estimates were obtained at 90% of the confidence level for the upper limits of the neutron-producing dd-reaction cross sections for average deuteron collision energies of 0.11, 0.34, 0.37, and 1.46 keV. These results substantiate feasibility to get a cross section magnitude for dd-reaction in the range of the collision energy of 0.8–3 keV using similar technology at the pulse current level of 2–3 MA.

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Hidaka, Hiroshi, Shigekazu Yoneda, Kunihiko Nishiizumi et Marc Caffee. « The Neutron Energy Spectra of Lunar Meteorites Evaluated from Sm and Er Isotopic Compositions ». Astrophysical Journal 925, n^o 2 (1 février 2022) : 209. http://dx.doi.org/10.3847/1538-4357/ac423a.

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Abstract Cosmic-ray exposure records of 13 lunar meteorites, Dhofar 081, Dhofar 910, Dhofar 911, Northwest Africa (NWA) 482, NWA 2995, NWA 2996, NWA 3136, NWA 3163, NWA 4472, NWA 4734, NWA 4884, NWA 4932, and NWA 4936, were characterized from the abundances of spallogenic (10Be and 26Al) and neutron-captured (36Cl, 41Ca,150Sm, and 168Er) nuclides produced by cosmic-ray irradiation. Assuming a single-stage irradiation model for individual meteorites, 11 of the 13 meteorites had resided at shallow depths in the range of 55 to 330 g cm−2 from the lunar surface and experienced cosmic-ray irradiations for 140–870 Ma on the Moon. In contrast, 2 of the 13 meteorites, Dhofar 911 and NWA 4932, cannot be simply explained by a single-stage irradiation, but need at least two-stage irradiation on the Moon. Furthermore, the neutron fluences of thermal and epithermal energy regions for individual meteorites were quantified from a combination of the isotopic shifts of 149Sm–150Sm and 167Er–168Er, respectively. Our estimates gave 8–11 times higher epithermal neutron fluences (1.7–13.7 × 101 7 neutrons cm−2) than the thermal neutron fluences (0.65–13.8 × 1016 neutrons cm−2) for 9 of the 13 meteorites, which are consistent with those from the lunar regolith materials in our previous study. This result also supports the long cosmic-ray irradiation of most lunar meteorites on the surface of the Moon.

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Darnowski, Piotr, et Nikolaj Uzunow. « Minor actinides impact on basic safety parameters of medium-sized sodium-cooled fast reactor ». Nukleonika 60, n^o 1 (1 mars 2015) : 171–79. http://dx.doi.org/10.1515/nuka-2015-0034.

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Abstract An analysis of the influence of addition of minor actinides (MA) to the fast reactor fuel on the most important safety characteristics was performed. A special emphasis was given to the total control rods worth in order to describe qualitatively and quantitatively its change with MA content. All computations were performed with a homogeneous assembly model of modified BN-600 sodium-cooled fast reactor core with 0, 3 and 6% of MA. A model was prepared for the Monte Carlo neutron transport code MCNP5 for fresh fuel in the beginning-of-life (BOL) state. Additionally, some other parameters, such as Doppler constant, sodium void reactivity, delayed neutron fraction, neutron fluxes and neutron spectra distribution, were computed and their change with MA content was investigated. Study indicates that the total control rods worth (CRW) decreases with increasing MA inventory in the fuel and confirms that the addition of MA has a negative effect on the delayed neutron fraction.

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Paul, Michael, Ido Silverman, Shlomi Halfon, Semion Sukoriansky, Boris Mikhailovich, Tala Palchan, Arkady Kapusta et al. « A 50 kW Liquid-Lithium Target for BNCT and Material-Science Applications ». EPJ Web of Conferences 231 (2020) : 03004. http://dx.doi.org/10.1051/epjconf/202023103004.

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A compact Liquid Lithium Target (LiLiT) has been operating at SARAF for several years with beam power of several kW (1.9-2.5 MeV, up to 2 mA). When bombarding the lithium with low energy protons neutrons are generated. The neutron source, mainly used for nuclear astrophysics research, was decommissioned in 2016 towards an upgraded model - with possible applications to Boron Neutron Capture Therapy (BNCT) and material-science studies. The improved version has been designed to sustain 50 kW proton beam power (2.5 MeV, ~20 mA) to provide sufficient neutron flux required for clinical BNCT application. The new model has a 50 mm wide lithium jet to enable dissipation of the higher beam power and an improved heat exchanger to remove the power to a secondary cooling loop. A new Annular Linear INduction electro-magnetic pump (ALIN) has been designed and built to provide the required lithium flow rate. Other mechanical improvements facilitate the maintenance of the system and the robustness of operation. Radiological risks due to the 7Be produced in the reaction are reduced by using an integrated lead shielding of the lithium reservoir. An integrated neutron moderator is being designed to adjust the neutron energy to the spectrum best suited to BNCT. A low power (6 kW) model of the new design with a narrower nozzle (18 mm wide) and a rotating-magnet electro-magnetic pump is operating at SARAF to support the ongoing astrophysics and nuclear research program [1], [2]. To fulfill clinical BNCT, the upgraded LiLiT model will require an accelerator of appropriate energy and intensity. The design features of the new system are presented in this paper.

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Konashi, Kenji, Kunihiro Itoh, Tsugio Yokoyama et Michio Yamawaki. « Utilization Research and Development of Hydride Materials in Fast Reactors ». Advances in Science and Technology 94 (octobre 2014) : 23–31. http://dx.doi.org/10.4028/www.scientific.net/ast.94.23.

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Metal hydrides have high hydrogen atom density, which is equivalent to that of liquid water. An application of the hafnium hydride has been investigated as a neutron absorber in the Fast Breeder Reactors (FBRs). Fast neutrons are efficiently moderated by hydrogen in Hf hydrides and are absorbed by Hf. Since three isotopes of Hf have large cross sections, increase in the life of control rod is considered by Hf hydride. Results of design study of the core with Hf hydride control rods shows that the long lived hafnium hydride control rod is feasible in the large sodium-cooled FBR. Results of irradiation test conducted in BOR-60 has demonstrated the integrity of the capsules during irradiation. Na bonded capsule has an advantage in confinement effect of hydrogen compared with He bonded one. An application of hydride technique to transmutation target of MA was also discussed. MA hydride target is able to enhance the transmutation rate in FBR.

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Knaster, Juan, et Yoshikazu Okumura. « Accelerators for Fusion Materials Testing ». Reviews of Accelerator Science and Technology 08 (janvier 2015) : 115–42. http://dx.doi.org/10.1142/s1793626815300078.

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Fusion materials research is a worldwide endeavor as old as the parallel one working toward the long term stable confinement of ignited plasma. In a fusion reactor, the preservation of the required minimum thermomechanical properties of the in-vessel components exposed to the severe irradiation and heat flux conditions is an indispensable factor for safe operation; it is also an essential goal for the economic viability of fusion. Energy from fusion power will be extracted from the 14 MeV neutron freed as a product of the deuterium–tritium fusion reactions; thus, this kinetic energy must be absorbed and efficiently evacuated and electricity eventually generated by the conventional methods of a thermal power plant. Worldwide technological efforts to understand the degradation of materials exposed to 14 MeV neutron fluxes [Formula: see text] m[Formula: see text]s[Formula: see text], as expected in future fusion power plants, have been intense over the last four decades. Existing neutron sources can reach suitable dpa (“displacement-per-atom”, the figure of merit to assess materials degradation from being exposed to neutron irradiation), but the differences in the neutron spectrum of fission reactors and spallation sources do not allow one to unravel the physics and to anticipate the degradation of materials exposed to fusion neutrons. Fusion irradiation conditions can be achieved through Li (d, xn) nuclear reactions with suitable deuteron beam current and energy, and an adequate flowing lithium screen. This idea triggered in the late 1970s at Los Alamos National Laboratory (LANL) a campaign working toward the feasibility of continuous wave (CW) high current linacs framed by the Fusion Materials Irradiation Test (FMIT) project. These efforts continued with the Low Energy Demonstrating Accelerator (LEDA) (a validating prototype of the canceled Accelerator Production of Tritium (APT) project), which was proposed in 2002 to the fusion community as a 6.7[Formula: see text]MeV, 100[Formula: see text]mA CW beam injector for a Li (d, xn) source to bridge with the International Fusion Materials Irradiation Facility (IFMIF) under discussion at the time. Worldwide technological efforts are maturing soundly and the time for a fusion-relevant neutron source has arrived according to world fusion roadmaps; if decisions are taken we could count the next decade with a powerful source of 14 MeV neutrons thanks to the expected significant results of the Engineering Validation and Engineering Design Activity (EVEDA) phase of the IFMIF project. The accelerator know-how has matured in all possible aspects since the times of FMIT conception in the 1970s; today, operating 125 mA deuteron beam at 40 MeV in CW with high availabilities seems feasible thanks to the understanding of the beam halo physics and the three main technological breakthroughs in accelerator technology: (1) the ECR ion source for light ions developed at Chalk River Laboratories in the early 1990s, (2) the RFQ operation of H[Formula: see text] in CW with 100 mA demonstrated by LEDA in LANL in the late 1990s, and (3) the growing maturity of superconducting resonators for light hadrons and low [Formula: see text] beams achieved in recent years.

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Wang, Deli, Daniel Moses, Guillermo Bazan, Alan Heeger et Jyostana Lal. « CONFORMATION OF A CONJUGATED POLYELECTROLYTE IN AQUEOUS SOLUTION : SMALL ANGLE NEUTRON SCATTERING ». Journal of Macromolecular Science, Part A 38, n^o 12 (30 novembre 2001) : 1175–89. http://dx.doi.org/10.1081/ma-100108376.

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He, Liaoyuan, Liang Chen, Shaopeng Xia et Yang Zou. « Minor Actinides Transmutation and 233U Breeding in a Closed Th-U Cycle Based on Molten Chloride Salt Fast Reactor ». Energies 15, n^o 24 (14 décembre 2022) : 9472. http://dx.doi.org/10.3390/en15249472.

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Long-lived minor actinides (MAs) are one of the primary contributors to the long-term radiological hazards of nuclear waste, and the buildup of MAs is hampering the development of nuclear power. The transmutation of MAs in reactors is regarded as a potential way to replace direct disposal to reduce the impact of MA on the environment and improve the utilization of fuel. Due to its superior features, such as outstanding neutron economy, no fuel assembly fabrication, high neutron flux, and especially online refueling and reprocessing, the molten chloride salt fast reactor (MCFR) is regarded as one of the potential reactors for MA incineration. In this work, MA transmutation capability and 233U breeding performance for an optimized MCFR have been evaluated in different scenarios. The results show that the MA transmutation capability and 233U breeding performance with online transuranic elements (TRU) and 232Th feeding scenario are improved significantly compared with the case in online 233U and 232Th feeding, when the initial MA loading is 5 mol%, the total mass of MA transmutation and MA incineration is 7160 kg and 1759 kg during the whole 100 years operation under online TRU and 232Th feeding scenario, and the corresponding average annual net production of 233U is 450 kg, however, the MA transmutation amount, MA incineration amount and average annual net production of 233U for online 233U and 232Th feeding scenario is 5298 kg, 1315 kg, and 249 kg, respectively. In addition, the research also shows that the increase in initial loading of MA has no obvious effect on the improvement of the 233U breeding performance but can improve the transmutation efficiency of MA under online TRU and 232Th feeding scenarios. Furthermore, if 233U is continuously extracted online from the core during the operation, the 233U breeding performance will be significantly improved, but it will deteriorate the safety performance, such as the fuel temperature coefficient of reactivity (TCR) and the effective delayed neutron fraction (EDNF), more importantly, it will also put forward higher requirements for the immature online reprocessing technology.

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Paul, Michael, Moshe Tessler, Shlomi Halfon, Elad Korngut, Arik Kreisel, Tala Palchan, Eliran Peretz, Leonid Weissman et Asher Shor. « Study of Astrophysical s-Process Neutron Capture Reactions at the High-Intensity SARAF-LiLiT Neutron Source ». EPJ Web of Conferences 232 (2020) : 01003. http://dx.doi.org/10.1051/epjconf/202023201003.

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We report on recent experiments at the Soreq Applied Research Accelerator Facility Liquid-Lithium Target (SARAF-LiLiT) laboratory dedicated to the study of s-process neutron capture reactions. The kW-power proton beam at 1.92 MeV (1-2 mA) from SARAF Phase I yields high-intensity 30 keV quasi-Maxwellian neutrons (3-5×1010 n/s). The high neutron intensity enables Maxwellian averaged cross sections (MACS) measurements of low-abundance or radioactive targets. Neutron capture reactions on the important s-process branching points 147Pm and 171Tm were investigated by activation in the LiLiT neutron beam and γ-measurements of their decay products. MACS values at 30 keV extracted from the experimental spectrum-averaged cross sections are obtained and will be discussed. The Kr region, at the border between the so-called weak and strong s-process was also investigated. Atom Trap Trace Analysis (ATTA) was used for the first time for the measurement of a nuclear reaction cross section. After activation in the quasi-Maxwellian neutron flux at SARAF-LiLiT, isotopic ratios were determined for 81Kr(230 ky)/80Kr and 85gKr(10.8 y)/84Kr. The latter ratio was confirmed both by low-level β counting and γ spectrometry. The shorter-lived capture products 79,85m,87Kr were detected by γ -spectrometry and the corresponding neutron-capture MACS of the respective target nuclei 78,84,86Kr were determined. The MACS of the 80Kr(n, γ)81Kr and 84Kr(n, γ)85gKr reactions are still under study. The partial MACS leading to 85mKr(4.5 h) measured in this experiment has interesting implications since this state decays preferentially by γ decay (79%) to 85Rb on a faster time scale than does 85gKr and behaves thus as an s-process branching point.

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Shlenskii, Mikhail, et Boris Kuteev. « System Studies on the Fusion-Fission Hybrid Systems and Its Fuel Cycle ». Applied Sciences 10, n^o 23 (26 novembre 2020) : 8417. http://dx.doi.org/10.3390/app10238417.

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This paper is devoted to applications of fusion-fission hybrid systems (FFHS) as a powerful neutron source implementing transmutation of minor actinides (MA: Np, Am, Cm) extracted from the spent nuclear fuel (SNF) of nuclear reactors. Calculations which simulated nuclide kinetics for the metallic fuel containing MA and neutron transport were performed for particular facilities. Three FFHS with fusion power equal to 40 MW are considered in this study: demo, pilot-industrial and industrial reactors. In addition, needs for a fleet of such reactors are assessed as well as future FFHSs’ impact on Russian Nuclear Power System. A system analysis of nuclear energy development in Russia was also performed with the participation of the FFHSs, with the help of the model created at AO “Proryv”. The quantity of MA that would be produced and transmuted in this scenario is estimated. This research shows that by the means of only one hybrid facility it is possible to reduce by 2130 the mass of MA in the Russian power system by about 28%. In the case of the absence of partitioning and transmutation of MA from SNF, 287 t of MA will accumulate in the Russian power system by 2130.

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Melatos, A., et E. S. Phinney. « Hydromagnetic Structure of a Neutron Star Accreting at Its Polar Caps ». Publications of the Astronomical Society of Australia 18, n^o 4 (2001) : 421–30. http://dx.doi.org/10.1071/as01056.

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AbstractThe hydromagnetic structure of a neutron star accreting symmetrically at both magnetic poles is calculated as a function of accreted mass, Ma, starting from a polytropic sphere plus central magnetic dipole (Ma =0) and evolving the configuration through a quasistatic sequence of twodimensional, Grad–Shafranov equilibria as Ma increases. It is found that the accreted material spreads equatorward under its own weight, compressing the magnetic field into a thin boundary layer and burying it everywhere except in a narrow, equatorial belt. The magnetic dipole moment of the star is given by µ=5.2×1024(B0/1012.5G)1.3(Ma/10−8Mʘ yr−1)0.18(Ma/Mʘ)−1.3Gcm3, and the fractional difference between its principal moments of inertia is given by Є=2.1×10−5(B0/1012.5G)0.27(Ma/10−8Myr−1)0.18(Ma/Mʘ)1.7, for Ma in the range 10−5Ma/Mʘ10−1,where B0 is the pre-accretion magnetic field strength, and Ma is the accretion rate.

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Onischuk, H. A., Yu A. Kurachenko et Yu G. Zabaryansky. « Photoneutrons for Radiation Therapy and Radionuclide Production ». KnE Engineering 3, n^o 3 (21 février 2018) : 41. http://dx.doi.org/10.18502/keg.v3i3.1605.

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The possibility of organizing neutron therapy with a photoneutron beam produced by the electron accelerator target, and ensuring the required dose at the tumor at a reasonable exposure time and with minimal impact on patients investigated. Generation of neutrons from the target of electron accelerator takes place in two stages: e- ® γ ® n, and in the selected electron energy range of 20-100 MeV, the bremsstrahlung gamma radiation in many times (~ 3 orders of magnitude) offers more than “useful” neutron yield. This raises the problem of the selective control of the “harmful” for radiotherapy secondary gamma radiation while providing the minimum attenuation of the neutron flux in the output beam. In order to solve the general problem of the formation of a neutron beam with necessary spectral characteristics having sufficient intensity, there has been resolved a number of computational tasks of the selection of the optimal configuration of the output beam unit and its composition. The matter of high importance is to minimize additional irradiation of the patient from the bremsstrahlung (generated by electrons) and secondary gamma radiation (generated by neutrons) from the accelerator target as well as from output unit’s materials. On the other hand, at a generation stage e- ® γ the bremsstrahlung beam could be applied for effective radionuclide production by reactions (γ,n) and (γ,p) due to high leak intensity ~ 1.3·1017 photon/s. By the Mo100(γ,n)99Mo reaction the main diagnostic nuclide 99Tc could be produced sufficiently for the clinical needs. The resulting configuration of the output unit provides the required beam quality for the neutron capture therapy (NCT), which commonly assumed to be the only competitive technology of neutron therapy on the background of the massive invasion of proton therapy and other highly selective techniques that ultimately damage the target sparing the surrounding tissues and organs. For the accessible accelerator (average current 4 mA and electron energy 35 MeV) the flux density of epithermal photoneutrons (they required for NCT) in the beam at the output is of the order of magnitude or more higher than the typical yield from existing and planned reactors' beams. The proposed scheme of generation and extraction of photoneutrons for NCT has a number of strong advantages over traditional techniques: a) the applying of electron accelerators for neutron production is much safer and cheaper than conventional reactor beams in use; b) accelerator with the target, the beam output unit with the necessary equipment can be placed on the territory of the clinic without any problems of radiation safety; c) the proposed target – liquid gallium, which also serves as a cooler, is an “environmentally friendly” material due to low activation which rapidly (in ~ 4 days) falls to the background level.

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Itoh, Keiji, Masakatsu Misawa et Toshiharu Fukunaga. « Neutron Diffraction of Amorphous Se-Te Prepared by MA. » Journal of the Japan Society of Powder and Powder Metallurgy 48, n^o 9 (2001) : 806–9. http://dx.doi.org/10.2497/jjspm.48.806.

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Cordelli, M., E. Diociaiuti, A. Ferrari, S. Miscetti, S. Müller, G. Pezzullo et I. Sarra. « An induced annealing technique for SiPMs neutron radiation damage ». Journal of Instrumentation 16, n^o 12 (1 décembre 2021) : T12012. http://dx.doi.org/10.1088/1748-0221/16/12/t12012.

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Abstract The use of Silicon Photo-Multipliers (SiPMs) has become popular in the design of High Energy Physics experimental apparatus with a growing interest for their application in detector area where a significant amount of non-ionising dose is delivered. For these devices, the main effect caused by the neutron fluence is a linear increase of the leakage current. In this paper, we present a technique that provides a partial recovery of the neutron damage on SiPMs by means of an Electrical Induced Annealing. Tests were performed, at the temperature of 20°C, on a sample of three SiPM arrays (2×3) of 6 mm2 cells with 50 μm pixel sizes: two from Hamamatsu and one from SensL. These SiPMs have been exposed to neutrons generated by the Elbe Positron Source facility (Dresden), up to a total fluence of 8 × 1011 n1 MeV-eq/cm2. Our techniques allowed to reduced the leakage current of a factor ranging between 15-20 depending on the overbias used and the SiPM vendor. Because, during the process the SiPM current can reach O(100 mA), the sensors need to be operated in a condition that provides thermal dissipation. Indeed, caution must be used when applying this kind of procedures on the SiPMs, because it may damage permanently the devices themself.

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Chahidi, Hassan, Hamid Bounouira, Hamid Amsil, Abdelmajid Choukri, Khalid Embarch, Abdessamad Didi, Ilias Aarab, Khalid Laraki et Hamid Marah. « Comparison of relative and k0 neutron activation analysis methods at MA-R1 TRIGA MARK II Research Reactor of CNESTEN (Morocco) ». E3S Web of Conferences 336 (2022) : 00054. http://dx.doi.org/10.1051/e3sconf/202233600054.

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Since the installation of the TRIGA MARK II reactors in the National Centre for Nuclear Energy, Science and Technology (CNESTEN), Neutron Activation Data Analysis software (NADA) for neutron activation analysis (NAA) based on the relative method was the first software used; Over the years, the neutron activation analysis laboratory has been seeking to develop other softwares based on k0-INAA standardization namely the K0-IAEA software and the k0 software for Windows. In this paper we will focus on the comparison between the performance of k0 software for Windows and NADA. We compared the results obtained by the NADA Software and k0 for windows for the same input parameters (sample mass, nuclear data, net peak area for the same gamma line and cooling measurement times). In the neutron activation analysis laboratory of the National Center for Nuclear Energy, Science and Technology (CNESTEN) we analysed several reference materials (RM) or certified reference materials (CRM) and WEPAL samples. In this analysis, only certified or recommended values were used to compare the two processes for the different elements.

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Klix, Axel, Toralf DÖring, Alexander Domula et Kai Zuber. « The intensive DT neutron generator of TU Dresden ». EPJ Web of Conferences 170 (2018) : 02004. http://dx.doi.org/10.1051/epjconf/201817002004.

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TU Dresden operates an accelerator-based intensive DT neutron generator. Experimental activities comprise investigation into material activation and decay, neutron and photon transport in matter and R&D work on radiation detectors for harsh environments. The intense DT neutron generator is capable to produce a maximum of 1012 n/s. The neutron source is a solid-type water-cooled tritium target based on a titanium matrix on a copper carrier. The neutron yield at a typical deuteron beam current of 1 mA is of the order of 1011 n/s in 4Π. A pneumatic sample transport system is available for short-time irradiations and connected to wo high-purity germanium detector spectrometers for the measurement of induced activities. The overall design of the experimental hall with the neutron generator allows a flexible setup of experiments including the possibility of investigating larger structures and cooled samples or samples at high temperatures.

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Sunardi, Sunardi, et Muryono Muryono. « DETERMINATION OF LIMIT DETECTION OF THE ELEMENTS N, P, K, Si, Al, Fe, Cu, Cd, WITH FAST NEUTRON ACTIVATION USING NEUTRON GENERATOR ». Indonesian Journal of Chemistry 6, n^o 2 (14 juin 2010) : 170–74. http://dx.doi.org/10.22146/ijc.21755.

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Determination of limit detection of the elements N, P, K, Si, Al, Fe, Cu, Cd, with fast neutron activation using neutron generator has been done. Samples prepared from SRM 2704, N, P, K elements from MERCK, Cu, Cd, Al from activation foil made in San Carlos, weighted and packed for certain weight then iradiated during 30 minutes with 14 MeV fast neutron using the neutron generator and then counted with gamma spectrometry (accuspec). At this research condition of neutron generator was set at current 1 mA that produced neutron flux about 5,47.107 n/cm2.s and experimental result shown that the limit detection for the elements N, P, K, Si, Al, Fe, Cu, Cd are 2,44 ppm, 1,88 ppm, 2,15 ppm, 1,44 ppm, 1,26 ppm, 1,35 ppm, 1,05 ppm, 2,99 ppm, respectively. The data indicate that the limit detection or sensitivity of appliance of neutron generator to analyze the element is very good, which is feasible to get accreditation AANC laboratory using neutron generator. Keywords: limit detection, AANC, neutron generator

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Ачкасов, V. Achkasov, Чевычелов, Yu Chevychelov, Анциферова, V. Antsiferova, Лавлинский et al. « Calculation of indicators of resistance of work of digital chips in CAD ». Forestry Engineering Journal 4, n^o 4 (15 janvier 2015) : 291–300. http://dx.doi.org/10.12737/8494.

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The technique of radiation-resistant design of integrated circuits in computer-aided design is presented and comparisons with expert data are provided, which are affected by these types of radiations like gam-ma, x-ray and neutron radiation, as well as the impact of the neutron pulse, which affect largely, on the gain of the transistor are examined. Different types of cardinality doses are represented that affect the crystals of integrated circuits based on the real pulse shape of artificial intelligence.

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Lin, Yu, Tobias Arlt, Nikolay Kardjilov, Ingo Manke et Werner Lehnert. « In Operando Neutron Radiography Analysis of a High-Temperature Polymer Electrolyte Fuel Cell Based on a Phosphoric Acid-Doped Polybenzimidazole Membrane Using the Hydrogen-Deuterium Contrast Method ». Energies 11, n^o 9 (24 août 2018) : 2214. http://dx.doi.org/10.3390/en11092214.

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In order to characterize high temperature polymer electrolyte fuel cells (HT-PEFCs) in operando, neutron radiography imaging, in combination with the deuterium contrast method, was used to analyze the hydrogen distribution and proton exchange processes in operando. These measurements were then combined with the electrochemical impedance spectroscopy measurements. The cell was operated under different current densities and stoichiometries. Neutron images of the active area of the cell were captured in order to study the changeover times when the fuel supply was switched between hydrogen and deuterium, as well as to analyze the cell during steady state conditions. This work demonstrates that the changeover from proton to deuteron (and vice versa) leads to local varying media distributions in the electrolyte, independent of the overall exchange dynamics. A faster proton-to-deuteron exchange was re-discovered when switching the gas supply from H2 to D2 than that from D2 to H2. Furthermore, the D2 uptake and discharge were faster at a higher current density. Specifically, the changeover from H to D takes 5–6 min at 200 mA cm−2, 2–3 min at 400 mA cm−2 and 1–2 min at 600 mA cm−2. An effect on the transmittance changes is apparent when the stoichiometry changes.

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Kubes, Pavel, Daniel Klir, Marian Paduch, Tadeusz Pisarczyk, Marek Scholz, Tomasz Chodukowski, Zofia Kalinowska et al. « Characterization of the Neutron Production in the Modified MA Plasma Focus ». IEEE Transactions on Plasma Science 40, n^o 4 (avril 2012) : 1075–81. http://dx.doi.org/10.1109/tps.2012.2187312.

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Schultz, L., P. Lamparter et S. Steeb. « X-Ray and Neutron Diffraction of Amorphous Nickel-Zirconium-Alloys as Prepared in Different Ways ». Zeitschrift für Naturforschung A 46, n^o 6 (1 juin 1991) : 491–98. http://dx.doi.org/10.1515/zna-1991-0604.

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AbstractThe structure of amorphous NiχZr100-χ-alloys (Χ= 30, 31, 34, 63.7, and 65), which were produced by melt spinning (MS), mechanical alloying (MA), and sputtering (SP) was studied by X-ray- and neutron diffraction yielding structure factors, pair correlation functions, coordination numbers, atomic distances, and Warren-Cowley chemical short range order parameters. The atomic arrangement within the first coordination sphere is independent of the method of preparation while in the second and higher spheres it differs between the MS- and the MA-alloys on the one side and the SP-specimens on the other side. Thus one understands that some physical properties of the different specimens differ

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He, Liaoyuan, Liang Chen, Yong Cui, Shaopeng Xia et Yang Zou. « Minor Actinides Transmutation Performance in a Closed Th–U Cycle Based on Molten Chloride Salt Fast Reactor ». Materials 15, n^o 23 (1 décembre 2022) : 8555. http://dx.doi.org/10.3390/ma15238555.

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The molten chloride salt fast reactor (MCFR) with a closed Th–U fuel cycle is receiving more and more attention due to its excellent performance, such as high solubility of actinides, superior breeding capacity, and good inherent safety. In this work, the neutronics performances for different minor actinides (MA) loadings and operation modes are analyzed and discussed based on an optimized MCFR. The results indicate that online continuous reprocessing can significantly increase the transmutation performance of MAs. In addition, MA loadings have an obvious effect on the neutronics characteristics of the MCFR, and it is helpful for improving the MA transmutation capability and 233U breeding performance, simultaneously. When MA = 5 mol%, the average annual MA transmutation mass and incineration mass can achieve about 53 kg and 13 kg, respectively, and the corresponding annual net production of 233U is 250 kg. When MA = 33.5 mol%, the annual MA transmutation mass and incineration mass can be about 310 kg and 77 kg, respectively, and the corresponding annual net production of 233U is 349 kg. However, when the MA loadings exceed 10%, the corresponding keff will exceed 1.1 for decades, even if only Th is continuously fed online. The results also indicate that the transmutation ratio (TR) and incineration ratio (IR) of MA increase and reach maximum values in the first decades for all the different MA loadings, which means MA may be fed into the fuel salt to improve its transmutation capability. Moreover, though MA loading will increase the level of radiotoxicity of the core in the early stage of burnup, the radiotoxicity of MA will drop rapidly after a brief rise during the operation. It can also be found that the temperature coefficient of reactivity (TCR) of all different MA loadings can be negative enough to maintain the safety of the MCFR during the whole operation, although it decreases in the beginning of life (BOL) with the increasing MA loading. Furthermore, the evolution of an effective delayed neutron fraction (EDNF) is also researched and discussed, and the EDNF varies most significantly when loading MA = 35.5 mol%, with a range of 273 to 310 pcm over the entire 100 years of operation.

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AVINASH, K. « Avinash–Shukla mass limit for the maximum dust mass supported against gravity by electric fields ». Journal of Plasma Physics 76, n^o 3-4 (15 janvier 2010) : 493–500. http://dx.doi.org/10.1017/s0022377809990729.

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AbstractThe existence of a new class of astrophysical objects, where gravity is balanced by the shielded electric fields associated with the electric charge on the dust, is shown. Further, a mass limit MA for the maximum dust mass that can be supported against gravitational collapse by these fields is obtained. If the total mass of the dust in the interstellar cloud MD > MA, the dust collapses, while if MD < MA, stable equilibrium may be achieved. Heuristic arguments are given to show that the physics of the mass limit is similar to the Chandrasekar's mass limit for compact objects and the similarity of these dust configurations with neutron and white dwarfs is pointed out. The effect of grain size distribution on the mass limit and strong correlation effects in the core of such objects is discussed. Possible location of these dust configurations inside interstellar clouds is pointed out.

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Glebov, A., Yu Baranaev, I. Moskovchenko et P. Kirillov. « SCWR DEVELOPMENT FROM CONCEPT TO TEST REACTOR ». PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY. SERIES : NUCLEAR AND REACTOR CONSTANTS 2019, n^o 3 (26 septembre 2019) : 30–44. http://dx.doi.org/10.55176/2414-1038-2019-3-30-44.

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The nuclear reactor cooled by supercritical pressure water - SCWR (Supercritical Water-cooled Reactor) is adopted as one of the promising reactors of the IV-generation. SCWR conceptual proposals are developed by more than 45 organizations in 16 countries with developed nuclear energy. The SCWR concept is based on the implementation of a single-circuit direct-flow scheme of nuclear power plants cooled by SKD water. The introduction of reactors of this type will increase the efficiency up to 45 %, increase the coefficient of fuel reproduction, reduce metal consumption and construction volumes, improve economic and environmental performance. Countries participating in the MFP in the direction of SCWR consider the development of a reactor with a thermal spectrum of neutrons and uranium fuel to be a priority, but in the subsequent stages, with an increase in problems with the storage of spent nuclear fuel (SNF) and Junior actinides (MA), it is possible to move to a reactor with a fast neutron spectrum, MOX fuel and a closed fuel cycle (ZTC). For ~10 years, the SSC RF - FEI and OKB "Gidropress" have been working together on the conceptual design of VVER-SKD - single-circuit RP with SCD coolant with a fast-resonance neutron spectrum with a capacity of Ne=1700 MW. This rector is recognized as the prospect of development of VVER technology with the possibility of using uranium fuel and the transition in the future to MOX-based fuel (U-Pu-Th) and to ZTZ. Rosatom recognizes this area as an innovative one, and has signed systemic agreements on Russia's participation in the work of the MFP in the SCWR direction. The paper presents the results of computational studies on the main version of the high-power reactor, as well as the test N=30 MW.

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Davies, Patrick, Roland Baatz, Heye Reemt Bogena, Emmanuel Quansah et Leonard Kofitse Amekudzi. « Optimal Temporal Filtering of the Cosmic-Ray Neutron Signal to Reduce Soil Moisture Uncertainty ». Sensors 22, n^o 23 (25 novembre 2022) : 9143. http://dx.doi.org/10.3390/s22239143.

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Cosmic ray neutron sensors (CRNS) are increasingly used to determine field-scale soil moisture (SM). Uncertainty of the CRNS-derived soil moisture strongly depends on the CRNS count rate subject to Poisson distribution. State-of-the-art CRNS signal processing averages neutron counts over many hours, thereby accounting for soil moisture temporal dynamics at the daily but not sub-daily time scale. This study demonstrates CRNS signal processing methods to improve the temporal accuracy of the signal in order to observe sub-daily changes in soil moisture and improve the signal-to-noise ratio overall. In particular, this study investigates the effectiveness of the Moving Average (MA), Median filter (MF), Savitzky–Golay (SG) filter, and Kalman filter (KF) to reduce neutron count error while ensuring that the temporal SM dynamics are as good as possible. The study uses synthetic data from four stations for measuring forest ecosystem–atmosphere relations in Africa (Gorigo) and Europe (SMEAR II (Station for Measuring Forest Ecosystem–Atmosphere Relations), Rollesbroich, and Conde) with different soil properties, land cover and climate. The results showed that smaller window sizes (12 h) for MA, MF and SG captured sharp changes closely. Longer window sizes were more beneficial in the case of moderate soil moisture variations during long time periods. For MA, MF and SG, optimal window sizes were identified and varied by count rate and climate, i.e., redestimates temporal soil moisture dynamics by providing a compromise between monitoring sharp changes and reducing the effects of outliers. The optimal window for these filters and the Kalman filter always outperformed the standard procedure of simple 24-h averaging. The Kalman filter showed its highest robustness in uncertainty reduction at three different locations, and it maintained relevant sharp changes in the neutron counts without the need to identify the optimal window size. Importantly, standard corrections of CRNS before filtering improved soil moisture accuracy for all filters. We anticipate the improved signal-to-noise ratio to benefit CRNS applications such as detection of rain events at sub-daily resolution, provision of SM at the exact time of a satellite overpass, and irrigation applications.

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Das, Basanta, Anurag Shyam, Rashmita Das et Durga Rao. « The neutron production rate measurement of an indigenously developed compact D-D neutron generator ». Nuclear Technology and Radiation Protection 28, n^o 4 (2013) : 422–26. http://dx.doi.org/10.2298/ntrp1304422d.

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One electrostatic accelerator based compact neutron generator was developed. The deuterium ions generated by the ion source were accelerated by one accelerating gap after the extraction from the ion source and bombarded to a target. Two different types of targets, the drive - in titanium target and the deuteriated titanium target were used. The neutron generator was operated at the ion source discharge potential at +Ve 1 kV that generates the deuterium ion current of 200 mA at the target while accelerated through a negative potential of 80 kV in the vacuum at 1.3?10-2 Pa filled with deuterium gas. A comparative study for the neutron yield with both the targets was carried out. The neutron flux measurement was done by the bubble detectors purchased from Bubble Technology Industries. The number of bubbles formed in the detector is the direct measurement of the total energy deposited in the detector. By counting the number of bubbles the total dose was estimated. With the help of the ICRP-74 neutron flux to dose equivalent rate conversion factors and the solid angle covered by the detector, the total neutron flux was calculated. In this presentation the operation of the generator, neutron detection by bubble detector and estimation of neutron flux has been discussed.

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Skalyga, V. A., I. V. Izotov, S. S. Vybin, T. V. Kulevoy, G. N. Kropachev, A. L. Sitnikov et S. V. Grigoriev. « Design of the proton injector for compact neutron source DARIA ». Journal of Physics : Conference Series 2244, n^o 1 (1 avril 2022) : 012092. http://dx.doi.org/10.1088/1742-6596/2244/1/012092.

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Abstract Project of the proton accelerator-driven compact neutron source DARIA (Dedicated for Academic Research and Industrial Application) is developed in order to replace small and middle flux neutron sources based on the nuclear reactors. DARIA has a uniquely high ratio of efficiency to cost due to deep optimization of each key element of the system (proton injector and accelerator, target, neutron moderator and neutron instruments. A unique ECR ion source, developed at the IAP RAS, would be used as a proton beam injector. In such device the plasma is heated by the powerful 28 GHz gyrotron radiation, providing a record level of volumetric energy input for such systems over 100 W/cm^3. The high plasma density and the optimal electron temperature provide proton beams formation with a current of up to several hundred mA and an emittance that meets the requirements of modern accelerators. The paper discusses the advantages of using such an ion source, its scheme and design performance.

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Batyaev, V. F., et S. V. Skliarov. « Detection of tiny amounts of fissile materials in large-sized containers with radioactive waste ». EPJ Web of Conferences 170 (2018) : 05005. http://dx.doi.org/10.1051/epjconf/201817005005.

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The paper is devoted to non-destructive control of tiny amounts of fissile materials in large-sized containers filled with radioactive waste (RAW). The aim of this work is to model an active neutron interrogation facility for detection of fissile ma-terials inside NZK type containers with RAW and determine the minimal detectable mass of U-235 as a function of various param-eters: matrix type, nonuniformity of container filling, neutron gen-erator parameters (flux, pulse frequency, pulse duration), meas-urement time. As a result the dependence of minimal detectable mass on fissile materials location inside container is shown. Nonu-niformity of the thermal neutron flux inside a container is the main reason of the space-heterogeneity of minimal detectable mass in-side a large-sized container. Our experiments with tiny amounts of uranium-235 (<1 g) confirm the detection of fissile materials in NZK containers by using active neutron interrogation technique.

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Korobeinikov, V., V. Kolesov, A. Terekhova et Yu Karazhelevskaya. « RESEARCHES OF THE POSSIBILITY TO BURN OUT MINOR ACTINIDES IN A FAST REACTOR WITH METAL FUEL ON THE BASIS OF ONLY MINOR ACTINIDES ». PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY. SERIES : NUCLEAR AND REACTOR CONSTANTS 2020, n^o 1 (26 mars 2020) : 59–68. http://dx.doi.org/10.55176/2414-1038-2020-1-59-68.

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Minor actinides (MA) - primarily, isotopes of neptunium, americium, and curium - attract particular attention due to their long-term radiotoxicity. Measures to reduce the increase in the number of minor actinides have not yet been taken their total number in the world is growing, and will reached more than 200 tons by 2020. Note that minor actinides, as well as nuclides formed as a result of neutron capture, have the ability to share, so it is necessary to investigate whether the nuclear reactor can work if only they are used as fuel? The paper examined the possibility of using fuels from MA alone in reactors without uranium or plutonium. From the results of comparing the fission and capture cross sections, it follows that fuel in the form of Am or Np-237 can only use a fast neutron reactor, since in the thermal and intermediate spectra the capture cross section significantly exceeds the fission cross section. The results of calculations of the active zones of a model fast reactor with fuel from one americium or neptunium-237 demonstrated the high speed of their transmutation and burning out.

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蔡, 进. « Effects on k_eff and Neutron Flux of MA Transmutation in Fast Reactor ». Nuclear Science and Technology 05, n^o 01 (2017) : 1–12. http://dx.doi.org/10.12677/nst.2017.51001.

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Fukunaga, Toshiharu, Masakatsu Misawa, Kenji Suzuki et Uichiro Mizutani. « Chemical structure of Ni-Ti neutron zero scattering amorphous powders prepared by MA. » Journal of the Japan Society of Powder and Powder Metallurgy 38, n^o 1 (1991) : 67–70. http://dx.doi.org/10.2497/jjspm.38.67.

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Cikhardt, J., D. Klir, A. V. Shishlov, V. A. Kokshenev, K. Rezac, R. K. Cherdizov, G. N. Dudkin et al. « Neutron fluence distribution in experiments with 3 MA deuterium gas-puff z-pinch ». Physics of Plasmas 27, n^o 7 (juillet 2020) : 072705. http://dx.doi.org/10.1063/5.0008108.

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Ilić, R., J. Rant, M. Humar, G. Somogyi et I. Hunyadi. « Neutron radiographic characteristics of MA-ND type (allyl-diglycol-carbonate) nuclear track detectors ». International Journal of Radiation Applications and Instrumentation. Part D. Nuclear Tracks and Radiation Measurements 12, n^o 1-6 (janvier 1986) : 933–36. http://dx.doi.org/10.1016/1359-0189(86)90737-5.

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