Engineering topics

Burkey, M. T.

Publications and source records attributed to Burkey, M. T..

11 records

DOE OSTI2024

The Beta-decay Paul Trap Mk IV: Design and commissioning

Here, the Beta-decay Paul Trap is an open-geometry, linear trap used to measure the decays of 8 Li and 8 B to search for a tensor contribution to the weak interaction. In the latest 8 Li measurement of Burkey et al. (2022), β scattering was the dominant experimental systematic uncertainty. The Beta-decay Paul Trap Mk IV reduces the prevalence of β scattering by a factor of 4 through a redesigned electrode geometry and the use of glassy carbon and graphite as electrode materials. The trap has been constructed and successfully commissioned with 8 Li in a new data campaign that collected 2.6 million triple coincidence events, an increase in statistics by 30% with 4 times less β scattering compared to the previous 8 Li data set.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2024

Improved Tensor Current Limit from 8 B 𝛽 Decay Including New Recoil-Order Calculations

A precision measurement of the 𝛽 + decay of 8 B was performed using the Beta-decay Paul Trap to determine the 𝛽−𝜈 angular correlation coefficient 𝑎 𝛽⁢𝜈 . The experimental results were combined with new ab initio symmetry-adapted no-core shell-model calculations to yield the second-most precise measurement from Gamow-Teller decays, 𝑎 𝛽⁢𝜈 = −0.3345 ± 0.001⁢9 stat ± 0.002⁢1 syst . This value agrees with the standard model value of −1/3 and improves uncertainties in 8 B by nearly a factor of 2. By combining results from 8 B and 8 Li , a tight limit on tensor current coupling to right-handed neutrinos was obtained. A recent global evaluation of all other precision 𝛽 decay studies suggested a nonzero value for right-handed neutrino coupling in contradiction with the standard model at just above 3⁢𝜎. Finally, the present results are of comparable sensitivity and do not support this finding.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2023

Angular Correlations in the β Decay of B 8 : First Tensor-Current Limits from a Mirror-Nucleus Pair

We present the first measurement of the α–β–ν angular correlation in the Gamow-Teller β + decay of 8 B. This was accomplished using the Beta-decay Paul Trap, expanding on our previous work on the β – decay of 8 Li. The 8 B result is consistent with the V – A electroweak interaction of the standard model and, on its own, provides a limit on the exotic right-handed tensor current relative to the axial-vector current of |C T /C A | 2 < 0.013 at the 95.5% confidence level. This represents the first high-precision angular correlation measurements in mirror decays and was made possible through the use of an ion trap. Here, by combining this 8 B result with our previous 8 Li results, we demonstrate a new pathway for increased precision in searches for exotic currents.

6 ≤ A ≤ 19↗

DOE OSTI2023

Determination of the $^8\mathrm{B}$ neutrino energy spectrum using trapped ions

We report the β + decay of 8 B provides the dominant source of solar neutrinos above 2 MeV. Consequently, experiments that detect neutrinos from the sun require an accurate determination of the 8 B neutrino energy spectrum. In this work, the β -decay Paul trap surrounded by double-sided silicon strip detectors was utilized to precisely measure the decay products of trapped 8 B ions. The results were used to determine the 8 Be final-state distribution and to reconstruct the neutrino energy spectrum. This measurement using trapped ions is the first of its kind and puts the neutrino energy spectrum on much firmer footing by discriminating between recently reported values for the maximum of the final-state distribution.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2022

Improved Limit on Tensor Currents in the Weak Interaction from Li 8 β Decay

Here, the electroweak interaction in the standard model is described by a pure vector-axial-vector structure, though any Lorentz-invariant component could contribute. In this Letter, we present the most precise measurement of tensor currents in the low-energy regime by examining the $β-\bar{ν}$ correlation of trapped 8 Li ions with the Beta-decay Paul Trap. We find $a_{β\barν}$ = - 0.3325 ± 0.0013 stat ± 0.0019 syst at 1σ for the case of coupling to right-handed neutrinos (C T = -C$^{'}_{T}$), which is consistent with the standard model prediction.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2022

Impact of Clustering on the Li 8 β Decay and Recoil Form Factors

We place unprecedented constraints on recoil corrections in the β decay of 8 Li, by identifying a strong correlation between them and the 8 Li ground state quadrupole moment in large-scale ab initio calculations. The results are essential for improving the sensitivity of high-precision experiments that probe the weak interaction theory and test physics beyond the standard model. In addition, our calculations predict a 2 + state of the α + α system that is energetically accessible to β decay but has not been observed in the experimental 8 Be energy spectrum, and has an important effect on the recoil corrections and β decay for the A = 8 systems. Furthermore, this state and an associated 0 + state are notoriously difficult to model due to their cluster structure and collective correlations, but become feasible for calculations in the ab initio symmetry-adapted no-core shell-model framework.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2022

Searching for the origin of the rare-earth peak with precision mass measurements across Ce–Eu isotopic chains

A nuclear mass survey of rare-earth isotopes has been conducted with the Canadian Penning Trap mass spectrometer using the most neutron-rich nuclei thus far extracted from the CARIBU facility. Here, we present a collection of 12 nuclear masses determined with a precision of ≤ 10 keV/c 2 for Z = 58-63 nuclei near N = 100. Independently, a detailed study exploring the role of nuclear masses in the formation of the r-process rare-earth abundance peak has been performed. Employing a Markov chain Monte Carlo (MCMC) technique, mass predictions of lanthanide isotopes have been made which uniquely reproduce the observed solar abundances near A = 164 under three distinct astrophysical outflow conditions. We demonstrate that the mass surface trends thus far mapped out by our measurements are most consistent with MCMC mass predictions given an r process that forms the rare-earth peak during an extended (n, γ) ⇌ (γ, n) equilibrium.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2021

New approach to precisely measure γ-ray intensities for long-lived fission products, with results for the decay of 95 Zr

For many fission products, the rays emitted following decay provide an easily-detectable signature that can be used to identify their quantities and distributions in a sample. As a result, γ-ray spectroscopy is often exploited to study fission-product yields, provided sufficiently accurate information on the γ-ray intensity is available. However, in many cases, the uncertainties in the existing nuclear data are large enough that they compromise the precision achievable for modern experiments and applications. To address this need, we have developed a new experimental method that is well suited to precisely measure absolute γ-ray intensities in the β decay of long-lived fission products. The approach involves the production of a radiopure sample by implantation of a mass-separated ion beam from the CAlifornium Rare Isotope Breeder Upgrade (CARIBU) facility on a thin carbon foil. The emitted β-decay radiation is detected with a 4π gas proportional counter and a meticulously efficiency-calibrated high-purity germanium (HPGe) detector. As a first measurement to demonstrate the approach, we studied the absolute γ-ray intensities of the strongest transitions following the β decay of 95 Zr and its decay-daughter 95 Nb, and determined them to fractional precisions of better than 1–2%. In addition, with a larger sample of activity produced through neutron irradiation of an isotopically-enriched Zr foil, we performed a high-precision measurement of the relative γ-ray intensities following the decay of 95 Zr with just the HPGe detector. Here, the sample-production method at CARIBU and the coincidence detection approach demonstrated here can be applied to study fission products with half-lives longer than a day, which includes isotopes important not only for nuclear-energy and national-security applications, but also for medical-isotope research and environmental monitoring.

4π↗

DOE OSTI2020

Spin-trap isomers in deformed, odd-odd nuclei in the light rare-earth region near $N=98$

Masses of neutron-rich, odd-odd Pm, Eu, and Tb nuclei near N = 98 were measured using the Canadian Penning Trap mass spectrometer at the Californium Rare Isotope Breeder Upgrade (CARIBU) facility. High-resolution mass measurements yielded the discovery of spin-trap isomers at N = 97 in Tb 162 , and in the N = 99 isotones of Pm 160 and Tb 164 . Furthermore, no evidence of long-lived isomers were observed at N = 95 in Eu 158 , at N = 97 in Pm 158 , nor at N = 101 in Eu 164 and Tb 166 . Here, these experimental observations are compared to results from multiquasiparticle blocking calculations.

150 ≤ A ≤ 189↗

DOE OSTI2020

$β$-delayed neutron emission studies of 137,138 I and 144,145 Cs performed with trapped ions

A detailed study of the β-delayed neutron emission properties of 137,138 I and 144,145 Cs has been performed by confining ions in the Beta-decay Paul Trap. The daughter ions following β decay emerge from the trapped-ion cloud with negligible scattering allowing reconstruction of the recoil-ion energy from the time of flight. From this information, the neutron-emission branching ratios and neutron-energy spectra were deduced. The results for the 137 I and 144,145 Cs decays are in agreement with previous results performed using direct neutron-detection techniques. In the case of 138 I, a branching ratio of 6.18(50)% is obtained, yielding a value consistent with the more recent results, which are a factor of two larger than measurements made prior to 1978.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2020

$β$-delayed-neutron studies of 135,136 Sb and 140 I performed with trapped ions

In this work, Beta-delayed-neutron $(βn)$ spectroscopy was performed using the Beta-decay Paul Trap and an array of radiation detectors. The $βn$ branching ratios and energy spectra for 135,136 Sb and 140 I were obtained by measuring the time of flight of recoil ions emerging from the trapped ion cloud. These nuclei are located at the edge of an isotopic region identified as having $βn$ branching ratios that impact the $r$-process abundance pattern around the A ≈ 130 peak. For 135,136 Sb and 140 I, $βn$ branching ratios of 14.6(13)%, 17.6(29)%, and 7.6(28)% were determined, respectively. The $βn$ energy spectra obtained for 135 Sb and 140 I are compared with results from direct neutron measurements, and the $βn$ energy spectrum for 136 Sb has been measured for the first time.

42 ENGINEERING↗