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Results for “MEV RANGE 01-10”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Output calculation of electron therapy at extended SSD using an improved LBR method

Purpose: To calculate the output factor (OPF) of any irregularly shaped electron beam at extended SSD. Methods: Circular cutouts were prepared from 2.0 cm diameter to the maximum possible size for 15 × 15 applicator cone. In addition, two irregular cutouts were prepared. For each cutout, percentage depth dose (PDD) at the standard SSD and doses at different SSD values were measured using 6, 9, 12, and 16 MeV electron beam energies on a Varian 2100C LINAC and the distance at which the central axis electron fluence becomes independent of cutout size was determined. The measurements were repeated with an ELEKTA Synergy LINAC using 14 × 14 applicator cone and electron beam energies of 6, 9, 12, and 15 MeV. The PDD measurements were performed using a scanning system and two diodes—one for the signal and the other a stationary reference outside the tank. The doses of the circular cutouts at different SSDs were measured using PTW 0.125 cm{sup 3} Semiflex ion-chamber and EDR2 films. The electron fluence was measured using EDR2 films. Results: For each circular cutout, the lateral buildup ratio (LBR) was calculated from the measured PDD curve using the open applicator cone as the reference field. The effective SSD (SSD{sub eff}) of each circular cutout was calculated from the measured doses at different SSD values. Using the LBR value and the radius of the circular cutout, the corresponding lateral spread parameter [σ{sub R}(z)] was calculated. Taking the cutout size dependence of σ{sub R}(z) into account, the PDD curves of the irregularly shaped cutouts at the standard SSD were calculated. Using the calculated PDD curve of the irregularly shaped cutout along with the LBR and SSD{sub eff} values of the circular cutouts, the output factor of the irregularly shaped cutout at extended SSD was calculated. Finally, both the calculated PDD curves and output factor values were compared with the measured values. Conclusions: The improved LBR method has been generalized to calculate the output factor of electron therapy at extended SSD. The percentage difference between the calculated and the measured output factors of irregularly shaped cutouts in a clinical useful SSD region was within 2%. Similar results were obtained for all available electron energies of both Varian 2100C and ELEKTA Synergy machines.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2018

Measurement of Angular Distributions of Gamma Rays from the Inelastic Scattering of 14.1-MeV Neutrons by Carbon and Oxygen Nuclei

The results obtained by measuring the angular and energy distributions of gamma rays originating from the inelastic scattering of 14.1-MeV neutrons by carbon and oxygen nuclei are presented. The measurements in question were performed by the tagged-neutron method in a beam of an ING-27 standard portable neutron generator. The angular distributions of gamma rays emitted by the 2{sup +} state of {sup 12}С at 4.43 MeVand the 3{sup −} state of {sup 16}O at 6.13 MeV were obtained.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2015

Fission Fragment Angular Distributions measured with a Time Projection Chamber

The subject is presented in a series of slides with the following organization: Introduction (What is anisotropy? Relevance (Theory and ratio cross section), Previous measurements); Experiment (Particle tracking in the fissionTPC, Neutron time of flight, Data analysis & uncertainty calculation, Preliminary result for 235 U); and Future Work (Refine 235 U result, Process 239 Pu data).

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2019

Investigation the optical band gap of self-assembled monolayer of tin selenide synthesized by chemical solution deposition

In this study, the fabrication and characterization of the thin layer of SnSe self-assembled were investigated by control of the preparation parameters. SnSe binary nanoparticles semiconductor were prepared using chemical solution deposition technique. The deposition time and temperature and the solution concentration that govern the evolution of the configuration films and optical band gap in chemical deposition processes was explored. We benefited from Rutherford Backscattering Spectrometry with 2 MeV {sup 4}He ions to determine the depth profile of the elements in tin selenide. UV–visible spectroscopy was used for energy band gap determination. Also, the nanostructured and the morphologies of the thin films were analyzed by scanning electron microscopy. We were able to achieve a broad optical band gap ranging from 5.82 to 3.06 eV of SnSe thin films appropriate for solar cell and photovoltaic applications.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2018

Effects of proton irradiation on the microstructure and shape recovery characteristics of a NiTi alloy

Highlights: • The complex multilayer structure can be induced by irradiation. • Phase constitution with increased fluence evolved as follows: B19’ → (B19’ + B2 + Ti{sub 2}Ni) → (B2 + Ti{sub 2}Ni + TiH{sub 2}). • The transformation temperature decreases remarkablly with the increasing of irradiation fluence. • The strain recovery characteristics deteriorated significantly with the irradiation fluence increasing. - Abstract: Herein, we investigate the effects of proton irradiation on the structure and shape recovery characteristics of a NiTi alloy and provide a mechanistic explanation of the observed phenomena. Detailed analysis revealed that bombardment with 3 MeV protons induced the formation of a complex multilayer structure comprising TiH{sub 2}, Ti{sub 2}Ni, austenite and austenite-martensite layers along the irradiation direction with increasing distance and the origin of the above structure was shown to be closely related to the preferential sputtering effect and irradiation-induced segregation. Finally, the shape recovery characteristics significantly deteriorated with increasing irradiation fluence, since the multilayer structure hindered the martensitic transformation.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Plasma-filled diode based on the coaxial gun

The paper presents the results of studies of a coaxial gun for a plasma-filled electron diode. Effects of the discharge channel diameter and gun current on characteristics of the plasma and pulse generated in the diode were investigated. The electron beam with maximum energy of {>=}1 MeV at the current of Almost-Equal-To 100 kA was obtained in the experiments with a plasma-filled diode. The energy of Almost-Equal-To 5 kJ with the peak power of {>=}100 GW dissipated in the diode.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

An integrated time-of-flight versus residual energy subsystem for a compact dual ion composition experiment for space plasmas

We have developed a novel concept for a Compact Dual Ion Composition Experiment (CoDICE) that simultaneously provides high quality plasma and energetic ion composition measurements over 6 decades in ion energy in a wide variety of space plasma environments. CoDICE measures the two critical ion populations in space plasmas: (1) mass and ionic charge state composition and 3D velocity and angular distributions of ∼10 eV/q–40 keV/q plasma ions—CoDICE-Lo and (2) mass composition, energy spectra, and angular distributions of ∼30 keV–10 MeV energetic ions—CoDICE-Hi. CoDICE uses a common, integrated Time-of-Flight (TOF) versus residual energy (E) subsystem for measuring the two distinct ion populations. This paper describes the CoDICE design concept, and presents results of the laboratory tests of the TOF portion of the TOF vs. E subsystem, focusing specifically on (1) investigation of spill-over and contamination rates on the start and stop microchannel plate (MCP) anodes vs. secondary electron steering and focusing voltages, scanned around their corresponding model-optimized values, (2) TOF measurements and resolution and angular resolution, and (3) cross-contamination of the start and stop MCPs’ singles rates from CoDICE-Lo and -Hi, and (4) energy resolution of avalanche photodiodes near the lower end of the CoDICE-Lo energy range. We also discuss physical effects that could impact the performance of the TOF vs. E subsystem in a flight instrument. Finally, we discuss advantages of the CoDICE design concept by comparing with capabilities and resources of existing flight instruments.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2015

Poynting-flux-dominated jets challenged by their photospheric emission

One of the key open question in the study of jets, in general, and jets in gamma-ray bursts (GRBs), in particular, is the magnetization of the outflow. Here we consider the photospheric emission of Poynting-flux-dominated outflows, when the dynamics is mediated by magnetic reconnection. We show that thermal three-particle processes, responsible for the thermalization of the plasma, become inefficient at a radius of r{sub sup}∼10{sup 9.5} cm, far below the photosphere, at ∼10{sup 11.5} cm. Conservation of the total photon number above r{sub sup} combined with Compton scattering below the photosphere enforces kinetic equilibrium between electrons and photons. This, in turn, leads to an increase in the observed photon temperature, which reaches ≳8 MeV (observed energy) when decoupling the plasma at the photosphere. This result is weakly dependent on the free model parameters. We show that in this case, the expected thermal luminosity is a few percent of the total luminosity, and could therefore be detected. The predicted peak energy is more than an order of magnitude higher than the observed peak energy of most GRBs, which puts strong constraints on the magnetization of these outflows.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2018

Color and Luminescence Centers in LuAG and Pr:LuAG Crystals Before and After {sup 60}Co γ-Irradiation

The absorption and thermoluminescence spectra and their relaxation in pure and praseodymium-doped LuAG crystals are comparatively studied to determine the contribution of intrinsic and impurity defects before and after irradiation by {sup 60}Co γ-quanta with an average energy of 1.25 MeV, dose rate of 0.8 Gy/s, and dose of 10{sup 3} Gy at 310 K. The existence of intrinsic F{sup +} defects with a typical absorption band at 375 nm and impurity Cr{sup 4+} centers absorbing at 285, 420, 490, and 595 nm in both LuAG and Pr:LuAG samples before irradiation is related to the crystal-growth technology and the impurity composition of the charge. An increase in the concentration of F{sup +} and Cr{sup 4+} centers after γ-irradiation is caused by charging of neutral F centers and changing of the electronic state (valence) of Cr{sup 3+} impurity centers. Formation of antisite defect complexes Lu{sub Al}{sup 3+}–V{sub O}, which are responsible for a luminescence band at 335 nm, is suggested. The first broad peak at 340 K on the thermoluminescence curves of both samples after irradiation with a dose of 10{sup 3} Gy is related to liberation of charge carriers from shallow trapping levels; thermal activation and radiative recombination with emitting centers begin at 310 K, which places the upper limit on the temperature range of application of these scintillation crystals.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Effect of Oxygen on the Quantum, Magnetic, and Thermodynamic Properties of Co Nanowires on the Reconstructed Anisotropic (1 × 2)/Au(110) and (1 × 2)/Pt(110) Surfaces: Ab Initio Approach

Ab initio theoretical study of the quantum magnetic properties of Co nanowires on the pure and oxygen-reconstructed (1 × 2)/Au(110) and (1 × 2)/Pt(110) surfaces is performed. Their structures and electronic configurations are calculated using the electron density functional theory. High values of magnetic moment and magnetic anisotropy energies of Co atoms are found on both pure and oxygen-reconstructed (1 × 2)/Au(110) and (1 × 2)/Pt(110) surfaces. The adsorption of oxygen atoms on the (1 × 2)/Au(110) substrate is shown to affect the structural arrangement of Co nanowire atoms on this substrate and to increase the magnetic anisotropy energy (by 1.91 meV per nanowire atom). The adsorption of oxygen on the Pt(110) substrate substantially decreases the magnetic anisotropy energy of the Co nanowire on it (by 5.98 meV per atom). The origin of these changes is revealed by analyzing the local densities of states of the d electrons of nanowire atoms. The temperature ranges of the states with the lowest free surface energy are determined using the atomistic thermodynamics methods. These data and the available experimental data are used to predict the possibility of observing the structures under study in experiments.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2019

Relativistic Modeling of Ultra-Short Electron Pulse Propagation

The ultrafast electron microscopy, electron diffraction, electron crystallography, and nanocrystallography methods opened the possibility of studying the coherent structural dynamics of matter. The time resolution of the ultrafast electron microscopy and electron diffraction methods determined by the duration of electron pulses is the key parameter of experimental setups. This paper treats electron pulse dynamics in the field free drift region specifically for applications in atomic imaging. The electron beam is modeled as a system of particles (N) with N = 1000 and N = 10 000 electrons. The beam propagates for a certain period of time (1–4 ns); during its propagation, electron distribution parameters (over coordinates and velocities) are calculated to characterize the temporal profile and uncertainty in the electron wavelength at the sample. The results of applying relativistic dynamic equations show that nonrelativistic results are satisfactorily applicable (with 15 per cent or better accuracy) for modeling short electron pulse elongation and broadening at 30 keV and lower energies. However, the results of such modeling may be significantly in error for intermediate energies (300 keV), and for the fast relativistic beams (3 MeV) they become completely wrong. The relative reduction in Coulomb repulsion effects at higher energies is known, however; we give a comprehensive treatment that allows a quantitative picture. Using high-energy electron pulses results in almost complete elimination of the repulsive Coulomb effect. Dispersion of electron velocities becomes much lower at higher energies. For 3 MeV electrons, electron pulse duration as well as its radius does not noticeably change even after traveling for 4 ns (1.2 m). Even at 300 keV, the pulse duration increase is negligible until 1 ns (0.2 m). A simple mean-field model suggested in [13] has been extended to arbitrarily fast relativistic electron pulses with good correspondence to direct dynamic modeling.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2017

Study of the Involvement of {sup 8}Be and {sup 9}B Nuclei in the Dissociation of Relativistic {sup 10}C, {sup 10}B, and {sup 12}C Nuclei

The results obtained by estimating the contribution of 8Be and 9B nuclei to the coherent dissociation of {sup 10}C, {sup 10}B, and {sup 12}C relativistic nuclei in nuclear track emulsions (“white” stars) are presented. The selection of white stars accompanied by 9B leads to a distinct peak appearing in the distribution of the excitation energy of 2α2p ensembles and having a maximum at 4.1 ± 0.3 MeV. A 8Be nucleus manifests itself in the coherent-dissociation reaction {sup 10}B → {sup 2}He + H with a probability of (25 ± 5)%, (14 ± 3)% of it being due to 9B decays. The ratio of the branching fractions of the {sup 9}B + n and {sup 9}Be + p mirror channels is estimated at 6 ± 1. An analysis of the relativistic dissociation of {sup 12}C nuclei in a nuclear track emulsion revealed nine 3α events corresponding to the Hoyle state.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2017

Calculation of Spectra of Neutrons and Charged Particles Produced in a Target of a Neutron Generator

An algorithm for calculating the spectra of neutrons and associated charged particles produced in the target of a neutron generator is detailed. The products of four nuclear reactions {sup 3}H(d,n){sup 4}He, {sup 2}H(d,n){sup 3}He, {sup 2}H(d,p){sup 3}H, and {sup 3}He(d,p){sup 4}He are analyzed. The results of calculations are presented in the form of neutron spectra for several emission angles and spectra of associated charged particles emitted at an angle of 180° for a deuteron initial energy of 0.13 MeV.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2017

Experimental Research to Confirm the Excitation of Gamov–Teller Resonance in Compound Nucleus {sup 118}Sb

At proton energies of 4–9 MeV, trial experimental investigations were performed to confirm the excitation of Gamov–Teller resonance (GTR) 1{sup +} in the compound nucleus {sup 118}Sb discovered by B.Ya. Guzhovskiy’s research group in the {sup 117}Sn(p,xn) reaction at proton energies of 7.2 MeV (the first component is GTR1) and 9.9MeV (the second component is GTR2). The {sup 117}Sn(p,xn) reaction was used, whose neutrons and background neutrons were registered by an all-wave long counter arranged at an angle of 140° to the direction of the proton beam propagation. Simultaneously, along with the registration of neutrons, elastically and inelastically scattered protons at angles of 20° and 160° were registered. At the proton energy equal to ~7.2 MeV, in the excitation functions for {sup 117}Sn(p,xn), {sup 117}Sn(p,p{sub 0}), and {sup 117}Sn(p,p{sub 4}){sup 117}Sn* (1004.5 keV, 3/2{sup +}), a resonance with a width of ≈1.2 MeV having an energy structure was discovered. Its possible quantum numbers are 1{sup +}.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2018

Study of the Mechanism of the {sup 13}C(d, p){sup 14}C Reaction at E{sub d} = 15.3 MeV

The angular dependences of the differential cross sections of the {sup 13}C(d, p){sup 14}C reaction at the deuteron energy of 15.3MeV are presented according tomeasurements for the cases where the final nucleus is produced in the ground state (0{sup +}) and in the 1{sup −} excited state at 6.094 MeV. The angular distribution of protons corresponding to the sum 0{sup +} (6.589 MeV) + 3{sup −} (6.728 MeV) + 0{sup −} (6.903 MeV) of states of the {sup 14}C nucleus that were not separated experimentally is also obtained. These experimental results are compared with their counterparts calculated by means of the FRESCO code for the mechanisms of neutron stripping and sequential neutron and dineutron transfer. The neutron and dineutron spectroscopic amplitudes are calculated for pure and mixed shell configurations. The best set of optical-potential parameters is determined for the entrance and exit reaction channels. It is shown that the neutron-stripping mechanismpermits describing themeasured angular distributions for all states of the {sup 14}C nucleus that were investigated here.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2018

Development of a Method for Measurement of Photonuclear-Reaction Cross Sections with the Aid of Simulated Quasimonoenergetic-Photon Spectra

A procedure for measuring photonuclear-reaction cross sections by employing the method of quasimonochromatization of the bremsstrahlung photon spectrum is developed. This procedure permits determining reaction cross sections via measuring the reaction yield at three fixed values of the electron energy. The procedure is equivalent to measuring the cross section in question for quasimonochromatic photons. Bremsstrahlung-photon spectra are obtained using state-of-the-art simulation means involving the GEANT4 code as applied to a specific experiment with allowance for its geometry, target thicknesses, electron-beam parameters, etc. The results obtained by simulating quasimonochromatic distributions of bremsstrahlung photons are presented for experiments at the LUE-8-5 linear electron accelerator of Institute for Nuclear Research (Moscow, Russian Academy of Sciences). These results are found to be in good agreement with the experimental energy distribution of the cross section for the reaction {sup 111}Cd(γ, γ') in the energy range between 5 and 8 MeV.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2018

Possibility of Studying Neutron–Neutron Correlations in Halo Nuclei

An experimental investigation of the reaction of core pickup from {sup 6}He and {sup 11}Li two-neutronhalo nuclei is proposed. In such experiments, neutron–neutron correlations in a halo nucleus will be assessed on the basis of the energy of a neutron–neutron quasibound state. A detailed kinematical simulation of the reaction {sup 6}He + {sup 2}H → {sup 6}Li + (nn) →{sup 6} Li + n + n is performed. It is shown that the energy of the quasibound state in question can determined from the shape of the energy spectrum of neutrons originating from the breakup of this state. In the proposed exclusive experiment, a beam of {sup 6}He ({sup 11}Li) nuclei with an energy of about 5 to 10 MeV per nucleon interacts with a deuterated-polyethylene target. This will permit detecting charged particles ({sup 6}Li and {sup 11}Be) and a neutron. On the basis of determining the energy of the neutron–neutron quasibound state, it will become possible to estimate the effective attraction between the valence neutrons in the field of the third particle (core).

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2017

Impact of silver metallization and electron irradiation on the mechanical deformation of polyimide films

The impact of silver metallization and electron irradiation on the physical and mechanical properties of polyimide films has been studied. The metal that impregnated the structure of the polyimide substrate was 1–5 μm. The surface coatings contained 80–97% of the relative silver mirror in the visible and infrared regions. Irradiation was performed at the ELU-6 linear accelerator with an average beam electron energy of 2 MeV, an integral current of up to 1000 μA, a pulse repetition rate of 200 Hz, and a pulse duration of 5 μs. The absorbed dose in the samples was 10, 20, 30, and 40 MGy. The samples were deformed at room temperature under uniaxial tension on an Instron 5982 universal testing system. The structural changes in the composite materials that result from the impact of the physical factors were studied using an X-ray diffractometer DRON-2M in air at 293 K using CuK{sub α} radiation (λ{sub αCu} = 1.5418 Å). A substantial growth of mechanical characteristics resulting from the film metallization, as compared to the pure film, was observed. The growth of the ultimate strength by Δσ = 105 MPa and the plasticity by Δε = 75% is connected with the characteristics of the change of structure of the metallized films and the chemical etching conditions. The electron irradiation of the metallized polyimide film worsens its elastic and strength characteristics due to the formation of new phases in the form of silver oxide in the coating. The concentration of these phases increased with increasing dose, which was also the result of the violation of the ordered material structure, namely, the rupture of polyimide macromolecule bonds and the formation of new phases of silver in the coating. A mathematical model was obtained that predicts the elastic properties of silver metallized polyimide films. This model agrees with the experimental data.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗