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Brune, C. R.

Publications and source records attributed to Brune, C. R..

At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

First measurement in a magnetic confinement fusion experiment of the H 3 + H 3 → He 5 + n intermediate two-body resonant reaction

We report on the first experimental measurements made at a magnetic confinement fusion device of the tritium(T)-tritium(T) reaction T + T → He 4 + 2 n indicating the presence of the intermediate two-body resonant reaction T + T → He 5 + n . During the second deuterium-tritium campaign (DTE2) at the Joint European Torus, measurements of fusion plasmas with high tritium concentrations, n T / ( n T + n D ) ≈ 0.99 , heated with tritium neutral beam injection, were performed using the neutron time-of-flight (TOF) spectrometer TOFOR. We detect a peak in the neutron emission TOF spectrum consistent with the two-body resonant reaction. The TT neutron emission energy spectrum is modeled using an R -matrix framework where the distributions of the most likely model parameters given our experimental TOF data are determined utilizing a Markov chain Monte Carlo approach. We compare our best estimate of the T + T neutron emission energy spectrum with results obtained at inertial confinement fusion experiments at the OMEGA facility and find a spectral shape that is consistent with the energy dependency in the neutron spectrum observed at OMEGA. Published by the American Physical Society 2024

Physics↗
DOE OSTI2024

Elastic scattering of 3 He + 4 He with the SONIK scattering chamber

Measurements of the elastic scattering cross section of 3 He and 4 He are important in order to improve constraints on theoretical models of 4 He ⁢( 3 He ,𝛾)⁢ 7 Be, a key reaction in Big Bang nucleosynthesis and solar neutrino production. The astrophysical 𝑆 factor for this reaction is a significant source of uncertainty in the standard-solar-model prediction of the 7 Be and 8 B solar neutrino fluxes. The elastic scattering measurements reported in the literature do not extend to low energies and lack proper uncertainty quantification. A new measurement of the 4 He ⁢( 3 He, 3 He)⁢ 4 He reaction has been made at center-of-mass energies 𝐸c.m.=0.38−3.13 MeV using the Scattering of Nuclei in Inverse Kinematics (SONIK) scattering chamber: a windowless, extended gas target surrounded by an array of 30 collimated silicon charged particle detectors situated at TRIUMF. This is the first elastic scattering measurement of 3 He + 4 He made below 500 keV and it has greater angular range and better precision than previous measurements. The elastic scattering data were analyzed using both 𝑅-matrix and halo effective field theory frameworks, and values of the 𝑠-wave scattering length and effective range were extracted. Here, the resulting improvement in knowledge of the 𝑠-wave effective-range function at low energies reduces the overall uncertainty in 𝑆 34 at solar energies.

Elastic scattering reactions↗
DOE OSTI2023

Absolute cross section of the C 12 ( p , γ ) N 13 reaction

Solar neutrino measurements have recently reached a level of sensitivity such that CNO fluxes can now be experimentally determined. While these first measurements are still only sensitive to the higher energy neutrinos resulting from the β + decays of 15 Ο produced by the 14 Ν ⁡( p ,$\gamma$)⁢ 15 O reaction, future measurements will work towards detection of neutrinos from the β + decay of 13 N from the 12 C ⁡( p ,$\gamma$)⁢ 13 N reaction. Here, this paper reports on a recent measurement of the 12 C ⁡( p ,$\gamma$)⁢ 13 N reaction covering a broad laboratory energy range between 1.0 and 2.5 MeV. The measurement was made to better determine the overall normalization of the absolute cross section and to explore the interference effects between the two broad, overlapping resonances at proton energies of 0.460 and 1.689 MeV and the direct capture to the ground state of 13 N in the framework of a multichannel R -matrix analysis. This work takes into account previous radiative capture as well as elastic 12 C ( p , p ) 12 C scattering data, making uncertainty estimations using a Bayesian framework, to determine a reliable extrapolation of the low energy S factor towards the stellar energy range of CNO hydrogen burning. These new experimental results, and a detailed investigation of the past literature data, suggest that the resonant component of the cross section should be 30% lower than previously accepted.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2023

Spin cutoff factor and level density for Ni 59 from an analysis of compound nuclear reactions

The spin cutoff parameter for 59 Ni has been studied from different types of experimental data, including neutron angular distributions from the 56 Fe(α,n) 59 Ni reaction, spin of discrete levels, the level density from the proton evaporation spectrum of the 54 Fe( 6 Li,p) 59 Ni reaction and neutron resonance spacing. Experimental data points were compared with calculations using models widely used in literature. It was found that the available empirical models overestimate data points in the energy region below the neutron separation energy, while microscopic calculations which take into account pairing correlations within Hartree-Fock +Bardeen-Cooper-Schrieffer approach are consistent with data. As a result, it confirmed earlier findings that pairing correlations play an important role and need to be taken into account when the spin cutoff parameter is calculated below the neutron separation energy.

(a,n) reaction↗
DOE OSTI2022

First near-threshold measurements of the 13 C($α, n$ 1 ) 16 O reaction for low-background-environment characterization

The modeling of background sources in large volume detection systems requires accurate nuclear cross sections for a variety of reactions. Among the most important are (α,n) on light nuclei, where α particles, up to ≈9 MeV, are produced from the decay of actinides present in trace amounts in detection and structural material. In order to model the neutron energy spectra and production of other secondary particles, the partial cross sections are needed. Yet very little experimental data exists for these partial cross sections because past measurements, hampered by the experimental challenges of neutron detection, have focused mostly on total reaction cross section measurements. Here, in this paper, the partial cross section of the 13 C(α,n 1 ) 16 O reaction is reported for the first time. The measurements were made near the reaction threshold using a high energy resolution helium spectrometer. The measurements show a rapidly increasing cross section, which quickly becomes a significant fraction of the total reaction cross section. Measurements are compared with previous theory estimates and differences of more than an order of magnitude are found. A comparison is made with new total cross section measurements and the current level of consistency is demonstrated.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

First inverse kinematics measurement of resonances in Be 7 ( α , γ ) C 11 relevant to neutrino-driven wind nucleosynthesis using DRAGON

A possible mechanism to explain the origin of the light $\textit{p}$ nuclei in the Galaxy is the nucleosynthesis in the proton-rich neutrino-driven wind ejecta of core-collapse supernovas via the $\textit{νp}$ process. However, this production scenario is very sensitive to the underlying supernova dynamics and the nuclear physics input. As far as the nuclear uncertainties are concerned, the breakout from the $\textit{pp}$ chains via the 7 Be(α,γ) 11 C reaction has been identified as an important link which can influence the nuclear flow and, therefore, the efficiency of the $\textit{νp}$ process. However, its reaction rate is poorly known over the relevant temperature range, $\textit{T}$ = 1.5–3 GK. We report on the first direct measurement of two resonances of the 7 Be(α,γ) 11 C reaction with previously unknown strengths using an intense radioactive 7 Be beam from the Isotope Separator and Accelerator (ISAC-I) Center facility and the DRAGON recoil separator in inverse kinematics. In this work, we have decreased the 7 Be(α,γ) 11 C reaction rate uncertainty to ≈9.4–10.7% over the relevant temperature region.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Direct Measurement of Resonances in Be 7 ( α , γ ) C 11 Relevant to ν p -Process Nucleosynthesis

Here, we have performed the first direct measurement of two resonances of the 7 Be(α,γ) 11 C reaction with unknown strengths using an intense radioactive 7 Be beam and the DRAGON recoil separator. We report on the first measurement of the 1155 and 1110 keV resonance strengths of 1.73 ± 0.25(stat) ± 0.40(syst) eV and $125^{+27}_{-25}$(stat) ± 15(syst) meV, respectively. The present results have reduced the uncertainty in the 7 Be(α,γ) 11 C reaction rate to ~9.4%–10.7% over $\textit{T}$ = 1.5–3 GK, which is relevant for nucleosynthesis in the neutrino-driven outflows of core-collapse supernovae ($\textit{νp}$ process). We find no effect of the new, constrained reaction rate on $\textit{νp}$-process nucleosynthesis.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Measurements of the 27 Al(α,n) Thick Target Yield near Threshold

In this work, we present results from direct measurements of the 27 Al(α,n) thick-target yield from laboratory incident energies E α ≈ 3 to 5 MeV, performed with the 3 HeBF 3 Giant Barrel (HeBGB) neutron detector at the Edwards Accelerator Laboratory. Our measurements have a small energy cadence in order to address discrepancies and sparseness of thick-target-yield data sets existing for this energy region. We find general agreement with existing data sets, including yields derived from cross-section data, while resolving a discrepancy between existing thick-target-yield data sets for E α ≈ 4–5 MeV. However, for E α < 3.5 MeV, our results are substantially lower than previous thick-target-yield data and somewhat larger than yields calculated from existing cross-section data. Our data complete the energy range needed for estimates of the 27 Al(α,n) contribution to neutrino and dark matter detector backgrounds and result in increased viability of 27 Al(α,n) as a plasma diagnostic tool at fusion facilities such as the National Ignition Facility.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2022

Measurements of the 96 Zr(α,n) cross section for astrophysics and applications

The reaction 96 Zr(α,n) plays an important role in ν-driven wind nucleosynthesis in core-collapse supernovae and is a possible avenue for medical isotope production. Here, cross section measurements were performed using the activation technique at the Edwards Accelerator Laboratory. Results were analyzed along with world data on the 96 Zr(α, n) cross section and 96 Zr(α, α) differential cross section using large-scale Hauser-Feshbach calculations. We find general agreement between our data, previous measurements, and a statistical description of the reaction. However, we find a larger cross section at low energies compared to prior experimental results, allowing for a larger astrophysical reaction rate. This may impact results of core-collapse supernova ν-driven wind nucleosynthesis calculations, but does not significantly alter prior conclusions about 99 Mo production for medical physics applications. The results from our large-scale Hauser-Feshbach calculations demonstrate that phenomenological optical potentials may yet be adequate to describe (α, n) reactions of interest for ν-driven wind nucleosynthesis, albeit with regionally-adjusted model parameters.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2022

Study of charged-particle emission in neutron reactions on 10 B

The 10 B + n system has been studied by measuring charged particles from neutron-induced reactions in the 1 to 20 MeV energy range. Protons, deuterons, tritons, and α particles were measured at four angles using the pulsed white neutron spectrum at the Los Alamos Neutron Science Center Weapons Neutron Research facility. Differential cross sections for each species are reported. These new data are combined with literature data in an R-matrix analysis of the 11 B compound system. Furthermore, a comparison is made to the molecular and cluster states candidates observed in these reactions.

43 PARTICLE ACCELERATORS↗
DOE OSTI2022

The 3 He BF 3 Giant Barrel (HeBGB) neutron detector

(α,n) reactions play an important role in nuclear astrophysics and applications and are an important background source in neutrino and dark matter detectors. Measurements of total (α,n) cross sections employing direct neutron detection often have a considerable systematic uncertainty associated with the energy-dependent neutron detection efficiency and the unknown initial neutron energy distribution. Furthermore, the 3 He BF 3 Giant Barrel (HeBGB) neutron detector was built at the Edwards Accelerator Laboratory at Ohio University to overcome this challenge. HeBGB offers a near-constant neutron detection efficiency of (7.5 ± 1.2)% over the neutron energy range 0.01 MeV–9.00 MeV, removing a significant source of systematic uncertainty present in earlier (α,n) cross section measurements.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2021

Reduction of the neutron imaginary potential off the stability line and its possible impact on neutron capture rates

The effect of the isovector imaginary optical potential has been studied experimentally by using the particle-evaporation technique for the 11 B + 48 Ca reaction with a 21.8 MeV 11 B beam. Spectra of neutron, proton, and α particles emitted from the neutron-rich compound nucleus 59 Mn have been measured and analyzed with traditional optical model potentials with their original parametrizations as well as with adjusted isovector imaginary components. It is shown that the isovector component of the imaginary potential is indispensable in the reproduction of proton and α-particle yields from this reaction and even needs to be enhanced compared with the suggestions of the original model parametrizations. Furthermore, this can lead to important consequences for astrophysical reaction-rate calculations.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2021

C 13 ( n , 2 n γ ) C 12 γ -ray production in the 14–16 MeV incident neutron energy range

We report γ-ray emission from 12 C and 13 C samples irradiated with deuterium-tritium fusion neutrons was experimentally measured at the Omega Laser Facility and at the Ohio University Edwards Accelerator Laboratory. The intent of these measurements was to determine the feasibility of using 13 C-based plastic ablators with embedded 12 C layers for “dark mix” diagnosis of inertial confinement fusion implosions. Spectrally resolved measurements at Ohio University identified significant 4.44-MeV γ-ray emission from the 13 C(n, 2nγ) 12 C-L1 reaction channel. The recorded 4.44-MeV 13 C signal was compared against emission from an identically irradiated 12 C target with known 12 C(n, n'γ) 12 C-L1 cross section, which resulted in an average 13 C(n, 2nγ) 12 C-L1 cross section of 117 ± 17 mb over the incident neutron energy distribution range from 14.4 to 15.8 MeV. Integrated 13C γ -ray signals above 2.9 MeV recorded with the Gas Cherenkov Detector at Omega exceeded MCNP6.1 predictions by a factor of 3. The additional signal was attributed to 4.44-MeV γs resulting in an inferred 13 C(n, 2nγ) 12 C-L1 cross section of 95 ± 11 mb at 14.1-MeV average incident neutron energy. As a result, the 13 C-based “dark mix” diagnostic concept was deemed infeasible.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2021

Investigation of secondary γ -ray angular distributions using the N 15 ( p , α 1 γ ) C * 12 reaction

The observation of secondary γ-rays provides an alternative method of measuring cross sections that populate excited final states in nuclear reactions. The angular distributions of these γ-rays also provide information on the underlying reaction mechanism. Despite a large amount of data of this type in the literature, publicly available R-matrix codes do not have the ability to calculate these types of angular distributions. In this report, the mathematical formalism derived in Brune and deBoer is implemented in the R-matrix code AZURE2 and calculations are compared with previous data from the literature for the 15 N( p, α1γ ) 12 C* reaction. In addition, new measurements, made at the University of Notre Dame Nuclear Science Laboratory using the Hybrid Array of Gamma Ray Detectors (HAGRiD), are reported that span an energy range from E p = 0.88 to 4.0 MeV. Excellent agreement between data and the phenomenological fit is obtained up to the limit of the previous fit at E p = 2.0 MeV and the R-matrix fit is extended from E x ≈ 13.5 up to E x ≈ 15.3 MeV, where 15 N+p and 12 C+α reactions are fit simultaneously for the first time. An excellent reproduction of the 15 N( p, α1γ ) 12 C* and 12 C(α, α) 12 C data is achieved, but inconsistencies and difficulty in fitting other data is encountered and discussed.

6 ≤ A ≤ 19↗
DOE OSTI2021

Determination of the 60 Zn level density from neutron evaporation spectra

Nuclear reactions of interest for astrophysics and applications often rely on statistical model calculations for nuclear reaction rates, particularly for nuclei far from β stability. However, statistical model parameters are often poorly constrained, where experimental constraints are particularly sparse for exotic nuclides. For example, our understanding of the breakout from the NiCu cycle in the astrophysical rp-process is currently limited by uncertainties in the statistical properties of the proton-rich nucleus 60 Zn. We have determined the nuclear level density of 60 Zn using neutron evaporation spectra from 58 Ni( 3 He,n) measured at the Edwards Accelerator Laboratory. We compare our results to a number of theoretical predictions, including phenomenological, microscopic, and shell-model-based approaches. Notably, we find the 60 Zn level density is somewhat lower than expected for excitation energies populated in the 59 Cu(p,γ) 60 Zn reaction under rp-process conditions. This includes a level density plateau from roughly 5 to 6 MeV excitation energy, which is counter to the usual expectation of exponential growth and all theoretical predictions that we explore. Here, a determination of the spin distribution at the relevant excitation energies in 60 Zn is needed to confirm that the Hauser-Feshbach formalism is appropriate for the 59 Cu(p,γ) 60 Zn reaction rate at x-ray burst temperatures

59 ≤ A ≤ 89↗
DOE OSTI2020

Cross section of neutrons from the H 2 ( n , 2 n ) reaction at E n = 15 MeV

In this work, the double-differential cross section of the deuteron breakup reaction 2 H(n, 2n) has been studied experimentally with a neutron beam energy of 15 MeV. Special attention has been devoted to estimation of background condition and multiple scattering effect in the scattering sample. Experimental data have been compared with models based on phase-space approximation used in the ENDF/B-VIII.0 data library and in the MCNP neutron transport code, as well as with rigorous model based on Faddeev equations used for cross section evaluations in JENDL data library. It was found that experimental data are better reproduced by Faddeev model, however, the model overestimates data in the low-energy region of the neutron spectrum (<4 MeV)

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

Cross-section measurements to low-lying excited final states in the 24 M(α,p) 27 Al*(γ) reaction as an energy source for x-ray bursts

Energy production in Type Ia x-ray bursts depends on a number of nuclear reactions that become efficient in a hot environment (up to 2 GK). Model sensitivity studies have been performed in an effort to better identify the reactions that have the largest effect, but these efforts are hampered by the high level of complexity of the astrophysical model and large nuclear physics uncertainties. In a recent study, the 24 Mg(α,p) 27 Al reaction was found to significantly affect the energy generation in x-ray bursts. This manuscript reports the first study of the 24 Mg(α,p 1,2 γ) 27 Al reaction at energies relevant for x-ray bursts. In conclusion, the branches to the 27 Al excited states increase to a small degree the estimates of the total astrophysical 24 Mg(α,p) 27 Al reaction rate.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗