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5 results on '"DD neutrons"'

1. On Scaling of DD Fusion Power in a Nanosecond Vacuum Discharge.

Author

Kurilenkov, Yu. K., Tarakanov, V. P., and Oginov, A. V.

Subjects
*CATHODES, *NEUTRONS, *ANODES
Abstract

Earlier, in a nanosecond vacuum discharge (NVD) with a deuterated Pd anode, the appearance of DD neutrons was observed not only at the well-studied quasi-stationary stage, where a virtual cathode (VC) appears in the interelectrode space, but also at the initial stage of the discharge. An analysis of the experiment shows that the autoelectron beam can play the role of a kind of trigger for starting DD fusion processes on the surface or in the volume of the Pd anode, but its mechanism at the initial stage of the discharge remained unclear. In this work, PIC modeling of the possible partial penetration of a beam of autoelectrons into hollow anode Pd tubes is carried out. This leads to the formation of very small short-lived VCs inside individual Pd tubes, where, starting from a current of 100 A, DD microfusion is possible. It is shown that in devices with oscillating ions, the favorable scaling of the DD fusion power, which increases with decreasing VC radius, can be retained up to rVC ≈ 0.02 cm. [ABSTRACT FROM AUTHOR]

Published
2022
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2. A study on neutron emission from a cylindrical inertial electrostatic confinement device.

Author

Buzarbaruah, N., Mohanty, S.R., and Hotta, E.

Subjects
*NEUTRON emission, *NEUTRON generators, *DOSIMETERS, *NEUTRON counters, *NUCLEAR fusion
Abstract

Abstract The adaption of new generation portable neutron sources has been increasingly marked in a wide range of research fields compared to the large-scale neutron generators. In this context, we have successfully demonstrated some essential parameters required for the emission of 2.45 MeV DD fusion neutrons from a steady state portable linear neutron source based on inertial electrostatic confinement scheme. The parameters that control the production of neutrons are the working pressure of the fuel gas, applied voltage, measured current and cathode geometries. The neutrons emitted from the source are confirmed using neutron monitor, bubble dosimeters, nuclear track detectors, and He-3 proportional counter. Presently, the device produces neutrons up to the order of ∼ 106 n/sec at discharge voltage ranging from -60 kV to -80 kV, and discharge current of 20 mA to 30 mA. Highlights • A portable linear neutron source based on inertial electrostatic confinement scheme was developed. • Neutron monitor, bubble dosimeters, nuclear track detectors and He-3 proportional counter were used to confirm the neutron emission. • The device produces neutrons up to the order of ∼ 106 n/sec at discharge voltage ranging from -60kV to -80kV and discharge current of 20 mA to 30 mA. [ABSTRACT FROM AUTHOR]

Published
2018
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3. Effect of nuclear elastic scattering on the D(d,n)3He fusion reactivity induced by energetic protons observed in the large helical device

Author

MATSUURA, Hideaki, KIMURA, Kento, UMEZAKI, D., OGAWA, Kunihiro, ISOBE, Mitsutaka, NISHITANI, Takeo, KAWAMOTO, Yasuko, OISHI, Tetsutaro, GOTO, Motoshi, OSAKABE, Masaki, SUGIYAMA, Shota, MATSUURA, Hideaki, KIMURA, Kento, UMEZAKI, D., OGAWA, Kunihiro, ISOBE, Mitsutaka, NISHITANI, Takeo, KAWAMOTO, Yasuko, OISHI, Tetsutaro, GOTO, Motoshi, OSAKABE, Masaki, and SUGIYAMA, Shota

Abstract

The enhancement of the fusion reaction rate coefficient induced by energetic protons, which isone of the typical nuclear elastic scattering (NES) effects, was observed in the large helicaldevice (LHD) located at the National Institute for Fusion Science. An intense high purityhydrogen beam (the atomic ratio of the contained deuterium was less than 1 ppm) with∼170 keV-energy and ∼10 MW-power was injected into a deuterium plasma with the electrontemperature ∼9 keV and density ∼1019 m−3. After the hydrogen beam injection, the neutrongeneration rate by the D(d,n)3He fusion reaction immediately increased, and an increment ofover one order of magnitude was observed, even though there was no meaningful iontemperature variation. The reasons for the increment in the neutron generation rate arediscussed with reference to the Boltzmann–Fokker–Planck analysis along with LHDexperimental data. It is concluded that the increment was induced by the production ofenergetic deuterons due to the NES of energetic protons., source:Citation H. Matsuura et al 2021 Nucl. Fusion 61 094001, source:https://doi.org/10.1088/1741-4326/ac13e6, identifier:0000-0002-7498-4191

Published
2021

4. Effect of nuclear elastic scattering on the D(d,n)3He fusion reactivity induced by energetic protons observed in the large helical device

Author

Mitsutaka Isobe, Kunihiro Ogawa, Masaki Osakabe, S. Sugiyama, Hiroto Matsuura, Takeo Nishitani, Yasuko Kawamoto, D. Umezaki, Motoshi Goto, T. Oishi, and K. Kimura

Subjects
Elastic scattering, fusion reaction rate coefficient, Nuclear and High Energy Physics, Fusion, Materials science, nuclear elastic scattering, Condensed Matter Physics, Molecular physics, Large Helical Device, DD neutrons, large angle scattering, Reactivity (chemistry), large helical device, Nuclear Experiment
Abstract

The enhancement of the fusion reaction rate coefficient induced by energetic protons, which isone of the typical nuclear elastic scattering (NES) effects, was observed in the large helicaldevice (LHD) located at the National Institute for Fusion Science. An intense high purityhydrogen beam (the atomic ratio of the contained deuterium was less than 1 ppm) with∼170 keV-energy and ∼10 MW-power was injected into a deuterium plasma with the electrontemperature ∼9 keV and density ∼1019 m−3. After the hydrogen beam injection, the neutrongeneration rate by the D(d,n)3He fusion reaction immediately increased, and an increment ofover one order of magnitude was observed, even though there was no meaningful iontemperature variation. The reasons for the increment in the neutron generation rate arediscussed with reference to the Boltzmann–Fokker–Planck analysis along with LHDexperimental data. It is concluded that the increment was induced by the production ofenergetic deuterons due to the NES of energetic protons.

Published
2021
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5. Study of DD Neutrons and their Transmission in Iron Spheres

Author

Dhakal, Sushil

Subjects
Nuclear Physics, Iron Sphere, Cross Section, Neutron Transmission, Monoenergetic, ENDF, Monte Carlo Simulation, Elastic Cross Section, Inelastic Cross Section, Total Cross Section, Non-Elastic Cross Section, DD Neutrons, Time of Flight, Breakup Neutrons
Abstract

The Deuterium-Deuteron (DD) reaction has been used as a neutron source to study the transport of neutrons in natural iron. The scattering targets are used in the form of spheres and the neutron transmission measurement has been done at 7-MeV incident deuteron beam energy. The purpose of this study is to test the elastic and non-elastic neutron scattering cross sections for iron in the ENDF/B-VII data library, as some indications about the inaccuracy of those cross sections have been found from previous studies. The experiment has been carried out using the 4.5-MV tandem accelerator at Edwards Accelerator Laboratory at Ohio University, Athens, Ohio.The DD source reaction has been measured at 5- and 7-MeV deuteron beam energy. The D(d,n) sup>3He monoenergetic reaction cross section has been measured from 0°to 135° at both 5- and 7-MeV beam energy and the D(d,np)D breakup reaction cross section has been measured up to 60° laboratory angles at 7-MeV beam energy. The target used is a deuterium gas cell of 3-cm length at approximately 2 atmosphere absolute pressure. The neutron energy is determined using the time of flight method. A NE213 liquid scintillation detector is used for neutron detection and the thick-target 27Al(d,n) reaction is used for the determination of neutron detector efficiency. The monoenergetic reaction cross section has been found to be in reasonable agreement with previous evaluations.The neutron transmission studies through iron spheres is done using two natural iron spheres with thicknesses of 3 and 8 cm. The DD source measurement (sphere-off) were repeated for the transmission studies and the neutron source was covered with the spheres for the transmission measurements. The experimental transmitted neutron spectrum is compared with the calculation done using Monte Carlo simulation code MCNP6.1 developed by Los Alamos National Laboratory. MCNP uses ENDF/B-VII.1 evaluated iron cross section for the simulation. The calculated and experimental neutron spectrum in time of flight has been compared at various laboratory angles from 0° to 150°.The calculated and experimental neutron time of flight spectra for neutron counts under the main peak (D(d,n)3He peak region) agree within the error bars for angles 90°, 135° and 150° for larger sphere (8-cm thickness) whereas they agree for all angles 0°, 15°, 30°, 45°, 90°, 135° and 150° for smaller sphere (3-cm thickness). However, the calculated and experimental neutron spectra show a difference of 12%, 11.80%, 16.85% and 19.67% in the main peak neutron counts for larger sphere at angles 0°, 15°, 30° and 45° respectively which can not be accounted for by the systematic uncertainty in our measurement (the 5% uncertainty in the target thickness and the 5% efficiency systematics are the main contributors). The sphere-off to on ratios for the calculation and the experiment also show a significant difference at those angles and this comparison is more robust as it avoids most of the systematic uncertainties including the efficiency. These differences likely come from the uncertainty in the ENDF cross section used.To test the ENDF cross section sensitivity, elastic cross section is decreased by 10% and inelastic cross section is increased by 14.78% in the energy range 7.2 to 11 MeV which corresponds to the energy range of the monoenergetic neutron peak for angles between 0° to 45°. This cross section modification keeps the total cross section constant on average in that energy range as the total in the library is assumed to be correct. This modification reduces the difference between the calculation and the experiment and brings it in agreement within the error bars. This result implies the possibility of underestimation of inelastic cross section in the above energy range and hence the overestimation of elastic cross section in the ENDF library.

Published
2016

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