Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “proton emission”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

25 Siβ + -decay spectroscopy

Background: β-decay spectroscopy provides valuable information on exotic nuclei and a stringent test for nuclear theories beyond the stability line. Purpose: To search for new β-delayed protons and γ rays of 25 Si to investigate the properties of 25 Al excited states. Method: 25 Si β decays were measured by using the Gaseous Detector with Germanium Tagging system at the National Superconducting Cyclotron Laboratory. The protons and γ rays emitted in the decay were detected simultaneously. Here, a Monte Carlo method was used to model the Doppler broadening of 24 Mg γ-ray lines caused by nuclear recoil from proton emission. Shell-model calculations using two newly developed universal sd-shell Hamiltonians were performed. Results: The most precise 25Si half-life to date has been determined. A new proton branch at 724(4) keV and new proton-γ-ray coincidences have been identified. Three 24 Mg γ-ray lines and eight 25 Al γ-ray lines are observed for the first time in 25 Si decay. The first measurement of the 25 Si β-delayed γ-ray intensities through the 25 Al unbound states is reported. All the bound states of 25 Al are observed to be populated in the β decay of 25 Si. Several inconsistencies between the previous measurements have been resolved, and new information on the 25 Al level scheme is provided. An enhanced decay scheme has been constructed and compared to the mirror decay of 25 Na and the shell-model calculations. Conclusions: The measured excitation energies, γ-ray and proton branchings, log $ft$ values, and Gamow-Teller transition strengths for the states of 25 Al populated in the β decay of 25 Si are in good agreement with the shell model calculations, offering gratifyingly consistent insights into the fine nuclear structure of 25 Al.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2026

FLASH-therapy suitable single-pulse proton generation using TiH 2 under nanosecond laser irradiation

We investigated proton emission from titanium hydride (TiH 2 ) targets irradiated in vacuum by a 6-ns, 1064-nm Nd:YAG laser. Time-of-flight measurements with a Faraday cup and an electrostatic ion analyzer resolved distinct proton peaks at high pulse energies, with yields on the order of 10 9 protons per shot. Systematic scans over pulse energy and up to 1000 repeated shots showed that, while the peak amplitude gradually decreased, the integrated proton number remained nearly constant. This behavior is consistent with surface-induced broadening of the plasma expansion while bulk hydrogen is replenished by diffusion and repeated ablation of fresh TiH 2 layers. Using the measured proton numbers and pulse widths, a simple direct-plasma-injection-style scaling indicates peak currents of ∼100 mA and sub-microsecond pulse durations. The pulse structure and yield satisfy key ultra-high-dose-rate criteria and, together with sustained output over 1000 shots, support TiH 2 -based laser ion sources as practical candidates for FLASH-therapy (ultra-high-dose-rate)-oriented studies and injector development using direct plasma injection.

43 PARTICLE ACCELERATORS↗
DOE OSTI2021

Proton decays in 16 Ne and 18 Mg and isospin-symmetry breaking in carbon isotopes and isotones

We report that proton-rich nuclei possess unique properties in the nuclear chart. Due to the presence of both continuum coupling and Coulomb interaction, phenomena such as halos, Thomas-Ehrman shift, and proton emissions can occur. Relevant experimental data are difficult to obtain, so that theoretical calculations are needed to understand nuclei at drip lines and to guide experimentalists. In particular, the 16 Ne and 18 Mg isotopes are supposed to be one-proton and/or two-proton emitting nuclei, but associated experimental data are either incomplete or even unavailable. Consequently, we performed Gamow shell model calculations of carbon isotones bearing A = 15 - 18 . Isospin-symmetry breaking occurring in carbon isotones and isotopes is also discussed. It is hereby shown that the mixed effects of continuum coupling and Coulomb interaction at drip lines generate complex patterns in isospin multiplets. Added to that, it is possible to determine the one-proton and two-proton widths of 16 Ne and 18 Mg . Obtained decay patterns are in agreement with those obtained in previous experimental and theoretical works. Moreover, to our knowledge, this is the first theoretical calculation of binding energy and partial decay widths of 18 Mg in a configuration interaction picture.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2022

Ab initio calculation of the β decay from 11 Be to a 10 Be + $\textit{p}$ resonance

In this work, the exotic β -delayed proton emission is calculated in 11 Be from first principles using chiral two- and three-nucleon forces. To investigate the unexpectedly large branching ratio measured in Ayyad et al. [Phys. Rev. Lett. 123, 082501 (2019)], we calculate the proposed (1/2 + , 1/2) proton resonance in 11 B using the no-core shell model with continuum. This calculation helps to address whether this enhancement is caused by unknown dark decay modes or an unobserved proton resonance. We report a branching ratio of $b_p$ = (1.3 ± 0.5) × 10 –6 , suggesting that its unexpectedly large value is caused by an unobserved proton resonance in 11 B.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2021

The São Paulo Potential and the 3 He Breakup Reaction at 130 MeV on 93 Nb and 197 Au

Nuclear reactions induced by weakly bound nuclei often result in the emission of light particles as products of the projectile breakup. The incident particle is expected to fragment before reaching the interior of the target nuclei, a characteristic that tends to favor forward angular emission. Although the first models developed for such reactions were proposed many decades ago by Udagawa and Tamura, Ichimura, Austern, Vincent, and Kasano, and Hussein and McVoy, to this date most of the attention has been dedicated to the breakup of the deuteron and other very weakly bound systems, while more strongly bound projectiles have not been fully explored. Here, we describe the production of protons and deuterons from the breakup of 3He. The breakup of 3 He on two heavy targets, 93 Nb and 197 Au, is analyzed in this study. However, the incoming energy involved is much larger than that of the standard phenomenological optical potentials available in the literature for the 3He entrance channel. We have overcome this difficulty by using the São Paulo potential and adjusting the nuclear diffusivity. The deuteron inclusive spectra were calculated at several angles and compared well with the experimental data. Theoretical proton emission predictions are also given for future reference, since no inclusive measurements were performed for the targets under study. Finally, one of our goals is to verify the description of deuteron emission from fast projectiles, for which many partial waves contribute to the scattering process.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2025

Study of alpha-resonances in ¹¹B via the ⁷Li(⁷Li, t ) reaction

The near-threshold proton resonance in ¹¹B, recently identified and characterized through independent experi-ments, plays a crucial role in understanding the unexpectedly high decay branch observed in the β-delayed proton emission (β− p) from the neutron halo nucleus ¹¹Be. Critical to interpreting this process is the determination of whether or not this state has any significant α-decay width (rα). A coincidence measurement was conducted to study the alpha-transfer reaction ⁷Li(⁷Li, t ) ¹¹B∗ → ⁷Li +α employing the Super-Enge Split Pole Spectrograph coupled with a silicon detector at Florida State University. This experiment aimed to investigate the structure of α resonances in ¹¹B in the Eₑₓ = 9.0 MeV–14 MeV energy region. In particular, to explore and constrain the α-decay branch of the near-threshold proton resonance at Eₑₓ = 11.44 MeV. No significant α-decay strength was observed from this state. Additionally, the experimental results provided insights into the state at Eₑₓ = 12.55 MeV, previously proposed as the T = 3/2 isobaric analog state of the ¹¹Be ground state. The observed decay pattern, dominated by α + ⁷Li, suggests a strong T = 1/2 component, indicating the need for further experimental measurements.

Lopez-Saavedra, E.↗
DOE OSTI2025

Application of a temporal multiscale method for efficient simulation of degradation in PEM Water Electrolysis under dynamic operating conditions

Hydrogen is emerging as a vital energy carrier, driven by the need to reduce carbon emissions. Proton Electrolyte Membrane Water Electrolysis (PEMWE) enables hydrogen production under fluctuating renewable power conditions but requires improved understanding and stability of the anode catalyst layer under dynamic operating conditions, especially with low noble metal loadings. Long-term degradation experiments are both time-consuming and costly; therefore, a systematic, model-aided approach is essential. In the present work, a temporal multiscale method is applied to reduce the computational effort of simulating long-term degradation processes in PEMWE, with an exemplary focus on catalyst dissolution. A mechanistic model incorporating the oxygen evolution reaction, catalyst dissolution, and hydrogen permeation from the cathode to the anode was hypothesized and implemented. In this way, the local periodicity of transport and reaction processes in dynamic PEMWE operation, which influence the gradual degradation of the catalyst layer, is captured. The temporal multiscale method significantly reduces the computational effort of simulation, decreasing processing time from hours to mere minutes. This efficiency gain is attributed to the limited evolution of Slow-Scale variables during each period of time P of the Fast-Scale variables. Consequently, simulation is required only until local periodicity is achieved within each Slow-Scale time step. Hence, the fully resolved dynamic problem is decoupled into these two scales, employing a heterogeneous multiscale technique. The developed approach effectively accelerates parameter estimation and predictive simulations, supporting systematic modeling of PEMWE degradation under dynamic conditions.

08 HYDROGEN↗
DOE OSTI2021

A pathway to unveiling neutrinoless ββ decay nuclear matrix elements via γγ decay

We investigate the experimental feasibility of detecting second-order double-magnetic dipole (γγ-M1M1) decays from double isobaric analog states (DIAS), which have recently been found to be strongly correlated with the nuclear matrix elements of neutrinoless ββ decay. Using the nuclear shell model, we compute theoretical branching ratios for γγ-M1M1 decays and compare them with other competing processes, such as single-γ decay and proton emission, which represent the dominant decay channels. We also estimate the potential competition from internal conversion and internal pair creation, which can influence the decay dynamics. Additionally, we propose an experimental strategy based on using LaBr3 scintillators to identify γγ-M1M1 transitions from the DIAS amidst the background of the competing processes. Our approach emphasizes the challenges of isolating the rare γγ-M1M1 decay and suggests ways to enhance the experimental detection sensitivity. Our simulations suggest that it may be possible to access experimentally γγ-M1M1 decays from DIAS, shedding light on the neutrinoless ββ decay nuclear matrix elements.

Romeo, Beatriz↗
DOE OSTI2020

Mirror-symmetry violation in bound nuclear ground states

Conservation laws are deeply related to any symmetry present in a physical system. Analogously to electrons in atoms exhibiting spin symmetries, it is possible to consider neutrons and protons in the atomic nucleus as projections of a single fermion with an isobaric spin (isospin) of t = 1/2. Every nuclear state is thus characterized by a total isobaric spin T and a projection T z —two quantities that are largely conserved in nuclear reactions and decays. A mirror symmetry emerges from this isobaric-spin formalism: nuclei with exchanged numbers of neutrons and protons, known as mirror nuclei, should have an identical set of states, including their ground state, labelled by their total angular momentum J and parity π. In this work, we report evidence of mirror-symmetry violation in bound nuclear ground states within the mirror partners strontium-73 and bromine-73. We find that a J π = 5/2 - spin assignment is needed to explain the proton-emission pattern observed from the T = 3/2 isobaric-analogue state in rubidium-73, which is identical to the ground state of strontium-73. Therefore the ground state of strontium-73 must differ from its J π = 1/2 - mirror bromine-73. This observation offers insights into charge-symmetry-breaking forces acting in atomic nuclei.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

Saturn-ring proton backlighters for the National Ignition Facility

Proton radiography is a well-established technique for measuring electromagnetic fields in high-energy-density plasmas. Fusion reactions producing monoenergetic particles, such as D 3 He, are commonly used as a source, produced by a capsule implosion. Using smaller capsules for radiography applications is advantageous as the source size decreases, but on the National Ignition Facility (NIF), this can introduce complications from increasing blow-by light, since the phase plate focal spot size is much larger than the capsules. In this article, we report a demonstration of backlighter targets where a “Saturn” ring is placed around the capsule to block this light. The nuclear performance of the backlighters is unperturbed by the addition of a ring. We also test a ring with an equatorial cutout, which severely affects the proton emission and is not viable for radiography applications. These results demonstrate the general viability of Saturn ring backlighter targets for use on the NIF.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2021

Measurement of the Ar ( e , e ' p ) and Ti ( e , e ' p ) cross sections in Jefferson Lab Hall A

The E12-14-012 experiment, performed in Jefferson Lab Hall A, has collected exclusive electron-scattering data ( e , e ' p ) in parallel kinematics using natural argon and natural titanium targets. In this study we report the first results of the analysis of the data set corresponding to beam energy 2222 GeV, electron scattering angle 21 . 5 ° , and proton emission angle – 50 ° . The differential cross sections, measured with ≈ 4 % uncertainty, have been studied as a function of missing energy and missing momentum, and compared to the results of Monte Carlo simulations, obtained from a model based on the distorted-wave impulse approximation.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

Convenient Location of a Near-Threshold Proton-Emitting Resonance in B 11

The presence of cluster-like narrow resonances in the vicinity of reaction/decay thresholds is a ubiquitous phenomenon with profound consequences. Here, we argue that the continuum coupling, present in the open quantum system description of the atomic nucleus, can profoundly impact the nature of near-threshold states. In this Letter, we discuss the structure of the recently observed near-threshold resonance in 11 B, whose very existence explains the puzzling beta-delayed proton emission of the neutron-rich 11 Be.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

All-optical nanoscopic spatial control of molecular reaction yields on nanoparticles

Molecular adsorbate reactions on nanoparticles play a fundamental role in areas such as nano-photocatalysis, atmospheric, and astrochemistry. They can be induced, enhanced, and controlled by field localization and enhancement on the nanoparticle surface. In particular, the ability to perform highly controlled near-field-mediated reactions is key to deepening our understanding of surface photoactivity on nanosystems. Here, using reaction nanoscopy, we experimentally demonstrate all-optical nanoscopic control of surface reaction yields by tailoring the near fields on nanoparticles with waveform-controlled linear and bicircular two-color laser pulses, respectively. We observe site-selective proton emission from the dissociative ionization of adsorbate molecules on Si O 2 nanoparticles as a function of the polarization and relative phase of the two-color pulses. The angularly resolved close-to-uniform mapping between the surface reaction yields and the measured ion momentum enables the observation and spatial control of molecular reactions on the nanoparticle surface with nanoscopic resolution. The experimental results are modeled and reproduced qualitatively by classical trajectory Monte Carlo simulations. Our work paves the way toward reliable all-optical control of photocatalytic chemical reactions on nanoscale surfaces.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Enhanced Nuclear Binding near the Proton Drip Line Opens Possible Bypass of the 64 Ge Rapid Proton Capture Process Waiting Point

Abstract We performed astrophysics model calculations with updated nuclear data to identify a possible bypass of the 64 Ge waiting point, a defining feature of the rapid proton capture (rp) process that powers type I X-ray bursts on accreting neutron stars. We find that the rp-process flow through the 64 Ge bypass could be up to 36% for astrophysically relevant conditions. Our results call for new studies of 65 Se, including the nuclear mass, β -delayed proton emission branching, and nuclear structure as it pertains to the 64 As( p , γ ) reaction rate at X-ray burst temperatures.

Nuclear astrophysics↗
DOE OSTI2025

$\mathcal{R}$ -matrix analysis of η + nat Cl reactions relevant to molten-salt reactor designs [Abstract]

Performed with support from the U.S. Nuclear Criticality Safety Program in an effort to provide improved chlorine cross section and corresponding covariance data, the R-matrix analysis of neutron induced reactions for two stable chlorine isotopes, 35,37 Cl, was performed in the energy range of thermal up to 1.2 MeV. Starting from the repository of the ENDF/B-VIII.0 library and following recent measurement campaigns, this work represents a significant improvement in the evaluation of the ( η , p ) reaction channel. The evaluation methodology uses the $\mathcal{R}$ -matrix code SAMMY to generate a set of Reich-Moore resonance parameters. As predicted by recently measured 35 Cl( η , p ) data, the presented evaluation features a dramatic increase in the magnitude of the ( η , p ) reaction channel over the ENDF/B-VIII.0 and previous nuclear data ENDF/B released libraries. Together with details of the evaluation procedure, the impact of the updates in the outgoing proton emissions on reactivity coefficients for different molten-salt reactor designs is presented and discussed.

charged-particle↗
DOE OSTI2020

Corrigendum: Balmer emission induced by proton impact on atomic hydrogen

In the original article [1] there is a misprint in the captions of figures 1 and 2. The AOCC calculations were labeled as (1) and the Glauber approximation as (2). It should be vice versa. In addition, in figure 2, the AOCC cross sections for excitation into the 3d1 and 3d2 states (dotted lines in panels (b) and (c)) were mistakenly reduced by a factor of 0.7. The correct results are shown below in the updated figure. Furthermore, these corrections do not affect the conclusions drawn in [1].

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2023

Interplay of effects of neutron skins in coordinate space and proton skins in momentum space on emission of hard photons in heavy-ion collisions near the Fermi energy

Within an isospin- and momentum-dependent Boltzmann-Uehling-Uhlenbeck transport model, we investigate the hard photons emission from neutron-proton bremsstrahlung in the reaction system of 208 Pb + 208 Pb around Fermi energy. Effects of neutron skins in coordinate (r) space and proton skins in momentum (k) space on the time evolution, the angular distribution, and the transverse momentum spectra of hard photons with different energies are studied. It is shown that the emission of direct hard photons is sensitive to the neutron skin, which has larger effects for more energetic hard photons. Meanwhile, we find that the proton skins have an important influence on the emission of direct hard photons, and its effect is actually even larger than that of neutron skins. Furthermore, it needs to take the effect of proton skins into account when we determine the size of neutron skins by comparing transport mode predictions of hard photons with the corresponding experimental measurements.

190 ≤ A ≤ 219↗