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M. Brodeur

Publications and source records attributed to M. Brodeur.

At least 37 records · Page 2Linked to original sources
arXiv2023

Executive Summary of the Topical Program: Nuclear Isomers in the Era of FRIB

We report on the Facility for Rare Isotope Beams (FRIB) Theory Alliance topical program "Nuclear Isomers in the Era of FRIB". We outline the many ways isomers influence and contribute to nuclear science and technology, especially in the four FRIB pillars: properties of rare isotopes, nuclear astrophysics, fundamental symmetries, and applications for the nation and society. We conclude with a resolution stating our recommendation that the nuclear physics community actively pursue isomer research. A white paper is forthcoming.

nucl-th↗
arXiv2023

Fundamental Symmetries, Neutrons, and Neutrinos (FSNN): Whitepaper for the 2023 NSAC Long Range Plan

This whitepaper presents the research priorities decided on by attendees of the 2022 Town Meeting for Fundamental Symmetries, Neutrons and Neutrinos, which took place December 13-15, 2022 in Chapel Hill, NC, as part of the Nuclear Science Advisory Committee (NSAC) 2023 Long Range Planning process. A total of 275 scientists registered for the meeting. The whitepaper makes a number of explicit recommendations and justifies them in detail.

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arXiv2023

Nuclear $β$ decay as a probe for physics beyond the Standard Model

This white paper was submitted to the 2022 Fundamental Symmetries, Neutrons, and Neutrinos (FSNN) Town Hall Meeting in preparation for the next NSAC Long Range Plan. We advocate to support current and future theoretical and experimental searches for physics beyond the Standard Model using nuclear $β$ decay.

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arXiv2022

TriSol: a major upgrade of the TwinSol RNB facility

We report here on the recent upgrade of the TwinSol radioactive nuclear beam (RNB) facility at the University of Notre Dame. The new TriSol system includes a magnetic dipole to provide a second beamline and a third solenoid which acts to reduce the size of the radioactive beam on target.

physics.acc-ph↗
arXiv2022

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

The electroweak interaction in the Standard Model (SM) is described by a pure vector-axial-vector structure, though any Lorentz-invariant component could contribute. In this work, we present the most precise measurement of tensor currents in the low-energy regime by examining the $β$-$\barν$ correlation of trapped $^{8}$Li ions with the Beta-decay Paul Trap. We find $a_{βν} = -0.3325 \pm 0.0013_{stat} \pm 0.0019_{syst}$ at $1σ$ for the case of coupling to right-handed neutrinos $(C_T=-C_T')$, which is consistent with the SM prediction.

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arXiv2020

First Penning trap mass measurement of $^{36}$Ca

Isobaric quintets provide the best test of the isobaric multiplet mass equation (IMME) and can uniquely identify higher order corrections suggestive of isospin symmetry breaking effects in the nuclear Hamiltonian. The Generalized IMME (GIMME) is a novel microscopic interaction theory that predicts an extension to the quadratic form of the IMME. Only the $A=20, 32$ $T=2$ quintets have the exotic $T_z = -2$ member ground state mass determined to high-precision by Penning trap mass spectrometry. In this work, we establish $A=36$ as the third high-precision $T=2$ isobaric quintet with the $T_z = -2$ member ground state mass measured by Penning trap mass spectrometry and provide the first test of the predictive power of the GIMME. A radioactive beam of neutron-deficient $^{36}$Ca was produced by projectile fragmentation at the National Superconducting Cyclotron Laboratory. The beam was thermalized and the mass of $^{36}$Ca$^+$ and $^{36}$Ca$^{2+}$ measured by the Time of Flight - Ion Cyclotron Resonance method in the LEBIT 9.4 T Penning trap. We measure the mass excess of $^{36}$Ca to be ME$ = -6483.6(56)$ keV, an improvement in precision by a factor of 6 over the literature value. The new datum is considered together with evaluated nuclear data on the $A=36$, $T=2$ quintet. We find agreement with the quadratic form of the IMME given by isospin symmetry, but only coarse qualitative agreement with predictions of the GIMME. A total of three isobaric quintets have their most exotic members measured by Penning trap mass spectrometry. The GIMME predictions in the $T = 2$ quintet appear to break down for $A = 32$ and greater.

nucl-ex↗
arXiv2020

High precision mass measurements of the isomeric and ground states of $^{44}$V: improving constraints on the IMME parameters of the A=44, $\text{0}^{\text{+}}$ quintet

The Isobaric Multiplet Mass Equation (IMME) has been successful at predicting the masses of isobaric analogue states in the same multiplet, while its coefficients are known to follow trends as functions of mass number. The Atomic Mass Evaluation 2016 [Chin. Phys. C 41, 030003 (2017)] $^{44}$V mass value results in an negative $c$ coefficient for the IMME quadratic term. The $b$ and $c$ coefficients can provide constraints for construction of the isospin-nonconserving (INC) Hamiltonians for the $pf$ shell. The excitation energy of the $0^+, T=2$ level in $^{44}$V is currently unknown and can be used to constrain the $^{44}$Cr mass. The aim of the experiment was to perform high-precision mass measurements to resolve the difference between $^{44}$V isomeric and ground states, to test the IMME, and to provide ingredients for identifying the $0^+$, $T=2$ state in $^{44}$V. High-precision Penning trap mass spectrometry was performed at LEBIT, to measure the cyclotron frequency ratios of [$^{44g,m}$VO]$^+$ versus [$^{32}$SCO]$^+$, a reference mass, to extract both the isomeric and ground state masses of $^{44}$V. The mass excess of the ground and isomeric states in $^{44}$V were measured to be $-23\ 804.9(80)$ keV/$\text{c}^2$ and $-23\ 537.0(55)$ keV/$\text{c}^2$. This yielded a new proton separation energy of $S_p$ = 1\ 773(10) keV. The new mass values of $^{44}$V have been used to deduce the IMME $b$ and $c$ coefficients of the lowest $2^+$ and $6^+$ triplets in $A=44$. The $2^+$ $c$ coefficient is verified with the IMME trend and agrees with the shell-model predictions using charge-dependent Hamiltonians. The mirror energy differences were determined between $^{44}$V and $^{44}$Sc, in line with isospin-symmetry. The new value of the proton separation energy determined will be important for the determination of the $0^+$, $T=2$ state in $^{44}$V and for prediction of the mass of $^{44}$Cr.

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arXiv2019

Exploring the mass surface near the rare-earth abundance peak via precision mass measurements at JYFLTRAP

The JYFLTRAP double Penning trap at the Ion Guide Isotope Separator On-Line (IGISOL) facility has been used to measure the atomic masses of 13 neutron-rich rare-earth isotopes. Eight of the nuclides, $^{161}$Pm, $^{163}$Sm, $^{164,165}$Eu, $^{167}$Gd, and $^{165,167,168}$Tb, were measured for the first time. The systematics of the mass surface has been studied via one- and two-neutron separation energies as well as neutron pairing-gap and shell-gap energies. The proton-neutron pairing strength has also been investigated. The impact of the new mass values on the astrophysical rapid neutron capture process has been studied. The calculated abundance distribution results in a better agreement with the solar abundance pattern near the top of the rare-earth abundance peak at around $A\approx165$.

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arXiv2018

r-Process Nucleosynthesis: Connecting Rare-Isotope Beam Facilities with the Cosmos

This is an exciting time for the study of r-process nucleosynthesis. Recently, a neutron star merger GW170817 was observed in extraordinary detail with gravitational waves and electromagnetic radiation from radio to gamma rays. The very red color of the associated kilonova suggests that neutron star mergers are an important r-process site. Astrophysical simulations of neutron star mergers and core collapse supernovae are making rapid progress. Detection of both, electron neutrinos and antineutrinos from the next galactic supernova will constrain the composition of neutrino-driven winds and provide unique nucleosynthesis information. Finally FRIB and other rare-isotope beam facilities will soon have dramatic new capabilities to synthesize many neutron-rich nuclei that are involved in the r-process. The new capabilities can significantly improve our understanding of the r-process and likely resolve one of the main outstanding problems in classical nuclear astrophysics. However, to make best use of the new experimental capabilities and to fully interpret the results, a great deal of infrastructure is needed in many related areas of astrophysics, astronomy, and nuclear theory. We will place these experiments in context by discussing astrophysical simulations and observations of r-process sites, observations of stellar abundances, galactic chemical evolution, and nuclear theory for the structure and reactions of very neutron-rich nuclei. This review paper was initiated at a three-week International Collaborations in Nuclear Theory program in June 2016 where we explored promising r-process experiments and discussed their likely impact, and their astrophysical, astronomical, and nuclear theory context.

astro-ph.SR↗
arXiv2018

Precision mass measurements on neutron-rich rare-earth isotopes at JYFLTRAP - reduced neutron pairing and implications for the $r$-process calculations

The rare-earth peak in the $r$-process abundance pattern depends sensitively on both the astrophysical conditions and subtle changes in nuclear structure in the region. This work takes an important step elucidating the nuclear structure and reducing the uncertainties in $r$-process calculations via precise atomic mass measurements at the JYFLTRAP double Penning trap. $^{158}$Nd, $^{160}$Pm, $^{162}$Sm, and $^{164-166}$Gd have been measured for the first time and the precisions for $^{156}$Nd, $^{158}$Pm, $^{162,163}$Eu, $^{163}$Gd, and $^{164}$Tb have been improved considerably. Nuclear structure has been probed via two-neutron separation energies $S_{2n}$ and neutron pairing energy metrics $D_n$. The data do not support the existence of a subshell closure at $N=100$. Neutron pairing has been found to be weaker than predicted by theoretical mass models. The impact on the calculated $r$-process abundances has been studied. Substantial changes resulting in a smoother abundance distribution and a better agreement with the solar $r$-process abundances are observed.

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arXiv2017

High-precision $Q_{EC}$-value measurement of the superallowed $β^+$ emitter $^{22}$Mg and an evaluation of the $A=22$ isobaric triplet

A direct $Q_{EC}$-value measurement of the superallowed $β^+$ emitter $^{22}$Mg was performed using TRIUMF's Ion Trap for Atomic and Nuclear science (TITAN). The direct ground-state to ground-state atomic mass difference between $^{22}$Mg and $^{22}$Na was determined to be $Q_{EC}=4781.40(22)$~keV, representing the most precise single measurement of this quantity to date. In a continued push towards calculating superallowed isospin-symmetry-breaking (ISB) corrections from first principles, ab-initio shell-model calculations of the $A=22$ IMME are also presented for the first time using the valence-space in-medium similarity renormalization group formalism. With particular starting two- and three-nucleon forces, this approach demonstrates a level of agreement with the experimental data that suggests reliable ab-initio calculations of superallowed ISB corrections are now possible.

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arXiv2017

Precision Mass Measurements of Neutron-Rich Co Isotopes Beyond N=40

The region near Z=28, N=40 is a subject of great interest for nuclear structure studies due to spectroscopic signatures in $^{68}$Ni suggesting a subshell closure at N=40. Trends in nuclear masses and their derivatives provide a complementary approach to shell structure investigations via separation energies. Penning trap mass spectrometry has provided precise measurements for a number of nuclei in this region, however a complete picture of the mass surfaces has so far been limited by the large uncertainty remaining for nuclei with N > 40 along the iron and cobalt chains. Here we present the first Penning trap measurements of $^{68,69}$Co, performed at the Low-Energy Beam and Ion Trap facility at the National Superconducting Cyclotron Laboratory. In addition, we perform ab initio calculations of ground state and two-neutron separation energies of cobalt isotopes with the valence-space in-medium similarity renormalization group approach based on a particular set of two- and three-nucleon forces which predict saturation in infinite matter. We discuss the importance of these measurements and calculations for understanding the evolution of nuclear structure near $^{68}$Ni.

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arXiv2017

Precision mass measurements of $^{125-127}$Cd isotopes and isomers approaching the $N=82$ closed shell

We present the results of precision mass measurements of neutron-rich cadmium isotopes. These nuclei approach the $N=82$ closed neutron shell and are important to nuclear structure as they lie near doubly-magic $^{132}$Sn on the chart of nuclides. Of particular note is the clear identification of the ground state mass in $^{127}$Cd along with the isomeric state. We show that the ground state identified in a previous mass measurement which dominates the mass value in the Atomic Mass Evaluation is an isomeric state. In addition to $^{127/m}$Cd, we present other cadmium masses measured ($^{125/m}$Cd and $^{126}$Cd) in a recent TITAN experiment at TRIUMF. Finally, we compare our measurements to new \emph{ab initio} shell-model calculations and comment on the state of the field in the $N=82$ region.

nucl-ex↗
arXiv2017

High-precision mass measurement of $^{56}$Cu and the redirection of the rp-process flow

We report the mass measurement of $^{56}$Cu, using the LEBIT 9.4T Penning trap mass spectrometer at the National Superconducting Cyclotron Laboratory at Michigan State University. The mass of $^{56}$Cu is critical for constraining the reaction rates of the $^{55}$Ni(p,$γ$)$^{56}$Cu(p,$γ$)$^{57}$Zn($β^+$)$^{57}$Cu bypass around the $^{56}$Ni waiting point. Previous recommended mass excess values have disagreed by several hundred keV. Our new value, ME=$-38 626.7(6.4)$ keV, is a factor of 30 more precise than the suggested value from the 2012 atomic mass evaluation [Chin. Phys. C {\bf{36}}, 1603 (2012)], and more than a factor of 12 more precise than values calculated using local mass extrapolations, while agreeing with the newest 2016 atomic mass evaluation value [Chin. Phys. C {\bf{41}}, 030003 (2017)]. The new experimental average was used to calculate the astrophysical $^{55}$Ni(p,$γ$) and $^{57}$Zn($γ$,p) reaction rates and perform reaction network calculations of the rp-process. These show that the rp-process flow redirects around the $^{56}$Ni waiting point through the $^{55}$Ni(p,$γ$) route, allowing it to proceed to higher masses more quickly and resulting in a reduction in ashes around this waiting point and an enhancement to higher-mass ashes.

nucl-ex↗
arXiv2017

Precision mass measurements of magnesium isotopes and implications on the validity of the Isobaric Mass Multiplet Equation

If the mass excess of neutron-deficient nuclei and their neutron-rich mirror partners are both known, it can be shown that deviations of the Isobaric Mass Multiplet Equation (IMME) in the form of a cubic term can be probed. Such a cubic term was probed by using the atomic mass of neutron-rich magnesium isotopes measured using the TITAN Penning trap and the recently measured proton-separation energies of $^{29}$Cl and $^{30}$Ar. The atomic mass of $^{27}$Mg was found to be within 1.6$σ$ of the value stated in the Atomic Mass Evaluation. The atomic masses of $^{28,29}$Mg were measured to be both within 1$σ$, while being 8 and 34 times more precise, respectively. Using the $^{29}$Mg mass excess and previous measurements of $^{29}$Cl we uncovered a cubic coefficient of $d$ = 28(7) keV, which is the largest known cubic coefficient of the IMME. This departure, however, could also be caused by experimental data with unknown systematic errors. Hence there is a need to confirm the mass excess of $^{28}$S and the one-neutron separation energy of $^{29}$Cl, which have both come from a single measurement. Finally, our results were compared to ab initio calculations from the valence-space in-medium similarity renormalization group, resulting in a good agreement.

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arXiv2016

Status of the NSCL Cyclotron Gas Stopper

A gas-filled reverse cyclotron for the thermalisation of energetic beams is under construction at NSCL/MSU. Rare isotopes produced via projectile fragmentation after in-flight separation will be injected into the device and converted into low-energy beams through buffer gas interactions as they spiral towards the centre of the device. The extracted thermal beams will be used for low energy experiments such as precision mass measurements with traps or laser spectroscopy, and further transport for reacceleration. Detailed calculations have been performed to optimize the magnetic field design as well as the transport and stopping of ions inside the gas. An RF carpet will be used to transport the thermal ions to the axial extraction point. The calculations indicate that the cyclotron gas stopper will be much more efficient for the thermalisation of light and medium mass ions compared to linear gas cells. In this contribution we will discuss simulations of the overall performance and acceptance of machine, the beam matching calculations to the fragment separator emittance, and the construction status.

physics.acc-ph↗
arXiv2015

Mass measurements of neutron-rich Rb and Sr isotopes

We report on the mass measurements of several neutron-rich $\mathrm{Rb}$ and $\mathrm{Sr}$ isotopes in the $A \approx 100$ region with the TITAN Penning-trap mass spectrometer. Using highly charged ions in the charge state $q=10+$, the masses of $^{98,99}\mathrm{Rb}$ and $^{98-100}\mathrm{Sr}$ have been determined with a precision of $6 - 12\ \mathrm{keV}$, making their uncertainty negligible for r-process nucleosynthesis network calculations. The mass of $^{101}\mathrm{Sr}$ has been determined directly for the first time with a precision eight times higher than the previous indirect measurement and a deviation of $3σ$ when compared to the Atomic Mass Evaluation. We also confirm the mass of $^{100}\mathrm{Rb}$ from a previous measurement. Furthermore, our data indicates the existance of a low-lying isomer with $80\ \mathrm{keV}$ excitation energy in $^{98}\mathrm{Rb}$. We show that our updated mass values lead to minor changes in the r-process by calculating fractional abundances in the $A\approx 100$ region of the nuclear chart.

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