Nuclear Masses in Astrophysics for the Next 25 Years

Penning trap mass spectrometry provides the most precise technique for direct measurement of the mass of single nuclides. The determination with high-precision of this fundamental nuclear property, and the related nuclear binding energy, gives information on the evolution of nuclear structure away from stability. It also produces valuable inputs for the theoretical models describing the...

Of the approximately 7,000 nuclei predicted by nuclear models, fewer than half have had their mass measured experimentally. Many of the remaining nuclei are highly unstable and difficult to produce. Precise mass measurements play a crucial role in nuclear structure studies and nucleosynthesis modelling, and require advanced instrumentation to reach the most exotic isotopes.
At the DESIR...

Understanding the reaction rates of nuclei relevant to nucleosynthesis processes relies in part on nuclear masses, often far from the valley of stability. The Canadian Penning Trap (CPT) has long measured such masses, and has recently concluded a decade-long campaign at the CARIBU facility, measuring over 200 nuclei produced through the spontaneous fission of $^{252}$Cf. One focus of these...

The rapid neutron capture (r-) process is responsible for producing half of the elements heavier than iron in the Universe. Most of the exotic neutron-rich nuclei along the r-process path are currently not experimentally accessible, making theoretical predictions essential, e.g., for nuclear masses, reaction rates, and fission properties. Here we employ ab initio masses for nuclei around the...

To further expand the science program at the Facility of Rare Isotope Beams (FRIB), we are developing a high-voltage Multi-Reflection Time-of-Flight (MR-ToF) device at FRIB. It is foreseen to increase the reach of FRIB’s high-precision mass measurement program, to deliver isobaric and isomeric purified ion beams to experimental stations within FRIB’s stopped and reaccelerated beam areas and to...

There is an astute idea of the different processes that assemble heavy elements (Z > 26) in our universe, but the production sites of some of them remain unclear. The processes that generate the most exotic nuclei such as r-process, for rapid neutron capture, and rp-process, for rapid proton capture are difficult to thoroughly describe because of the lack of experimental nuclear properties of...

Atomic masses are indispensable in nuclear structure and astrophysics research, and Penning traps enable the most precise mass measurements achievable to date [1]. TRIGA-Trap is a high-precision, double Penning-trap mass spectrometer located in the reactor hall of the TRIGA (Training, Research, Isotopes, General Atomic) research reactor in Mainz, Germany [2]. At TRIGA-Trap, mass measurements...

The nuclear two-photon or double gamma (2$\gamma$) decay is a rare
second-order electromagnetic process in which an excited nucleus emits two gamma rays simultaneously [1]. Its branching ratio is significantly lower than that of competing first-order processes such as internal conversion, pair creation, or single-photon emission, making its experimental observation extremely challenging....

TRIUMF's Ion Trap for Atomic and Nuclear science (TITAN) specializes in high-precision measurements and isobaric separation of exotic nuclei using advanced electromagnetic traps. These precise mass measurements are crucial for investigating nuclear structure and studying astrophysical processes involving isotopes far from the valley of stability.
TITAN’s Multiple-Reflection Time-of-Flight...

Approximately half of the nuclei heavier than iron are produced by the rapid neutron capture process ($r$ process). [1] The r process can be simulated with nuclear reaction network codes for which nuclear input data is essential. Particularly neutron capture reaction rates and $\beta$-decay $Q$ values are important, both of which are dependent on nuclear masses. However, many neutron-rich...

Bound-state beta decay is an exotic nuclear process in which the emitted electron is created directly into a vacant atomic orbital rather than being released into the continuum. This rare decay mode becomes significantly more probable in highly charged ions and requires long-duration storage measurements, conditions that are uniquely achievable at storage ring facilities. To date, all...

A Multi-Reflection Time-of-Flight Mass-Spectrometer (MR-ToF-MS) [1], a device that rapidly separates ions based on their mass-over-charge ratios, has been incorporated to the Ion-Guide Isotope-Separator On-Line (IGISOL) facility [2]. At IGISOL, a variety of radioactive beams can be produced via fusion-evaporation, fission or multinucleon-transfer reactions. The continuous ion beam is...

The CARIBU facility just conpleted an upgrade to nuCARIBU where the fission products are now obtained from neutron-induced fission of 235U instead of the spontaneous fission of 252Cf used previously. This new source is more intense and should provide access to even more exotic nuclides and allow extending the mass measurement campaigns on very neutron-rich isotopes that were performed at...

The ISOLTRAP experiment [1] is a multi-ion-trap mass spectrometer located at ISOLDE/CERN for high-precision mass measurements of artificially produced, short-lived, exotic radionuclides far from stability. Experimentally, ISOLTRAP uses multi-reflection time-of-flight and Penning-trap mass spectrometry for absolute and relative atomic mass measurements.
Following Einstein's famous...

In the quest to measure the masses of the most exotic species available at TRIUMF, the TITAN facility has transitioned from a Penning-trap to a Multi-Reflection Time-Of-Flight (MR-TOF) mass spectrometer. The latter has permitted measurements of yields with species less than 0.01 particles per second as well as half-life determinations. With an extraordinary dynamic range, TITAN has tackled...

The crust of neutron stars in soft X-ray transients is heated up by nuclear reactions induced by hydrostatic compression during periods of active accretion. These periods alternate with quiescent phases, during which X-ray telescopes in space have monitored a gradual decrease in the thermal emission from the surface of a dozen neutron stars [1]. The exact location of heating sources and the...

The synthesis of elements via the rapid-neutron capture process depends sensitively on the one-neutron separation energy, which in turns is influenced by nuclear structure effects such as shell closure and deformation. It has already been demonstrated for the light isotopes that standard magic numbers such as 20, 28 vanish while new ones emerge as nuclei gets more neutron rich. Such situation...

Atomic masses are indispensable in nuclear structure and astrophysics research, and Penning traps enable the most precise mass measurements achievable to date [1]. TRIGA-Trap is a high-precision, double Penning-trap mass spectrometer located in the reactor hall of the TRIGA (Training, Research, Isotopes, General Atomic) research reactor in Mainz, Germany [2]. At TRIGA-Trap, mass measurements...

A neural network with two hidden layers is developed for nuclear mass prediction, based on the finite-range droplet model (FRDM12). Different hyperparameters, including the number of hidden units, the choice of activation functions, the initializers, and the learning rates, are adjusted explicitly and systematically.
The resulting mass predictions are achieved by averaging the predictions...

The established storage ring mass spectrometry at the current operational HIRFL-CSR facility in Lanzhou has demonstrated its efficacy in accurately measuring the masses of short-lived nuclei that are far from beta stability. With the advent of the High Intensity heavy-ion Accelerator Facility (HIAF), the beam intensity is anticipated to be three orders of magnitude higher than what can...

Approximately half of the nuclei heavier than iron are produced by the rapid neutron capture process ($r$ process). [1] The r process can be simulated with nuclear reaction network codes for which nuclear input data is essential. Particularly neutron capture reaction rates and
$\beta$-decay Q values are important, both of which are dependent on nuclear masses. However, many neutron-rich...

More details to my talk "Schottky & Isochronous Mass Spectroscopy"

The time-of-flight magnetic rigidity (TOF-B$\rho$) technique is an effective method for determining the mass of unstable nuclides that have lifetimes of the order of 10s of ms. This method uses the motion of an ion in a magnetic field to determine its mass. With sufficiently precise time-of-flight measurements, around 10 ps uncertainty, the resulting mass resolution is of the order of...

In this poster, I will present the work that revolves around nuclear mass measurements methods of exotic nuclei with the ISOLTRAP experiment at CERN. You will find the astrophysical motivations for mass measurements in two extremes of the nuclear chart near the magic proton number Z = 50. To reach these areas, there are some technical challenges that we have to face. In this context, I will...

Time-of-flight mass measurement of exotic nuclei near N=28 shell closure around sulfur

The Nuclear Physics European Collaboration Committee (NuPECC) recently published its Long Range Plan (LRP) 2024 for European Nuclear Physics [1]. The document is a result of a large community effort, involving researchers in various meetings, workshops and thematical working groups. Nuclear masses and their importance for nuclear astrophysics is highlighted throughout the document, from the...

High precision mass measurement using ion traps continue to play an important role in shaping our understanding of the nucleus. State-of-the-art spectrometers nowadays can reach far into the neutron-rich terra incognita, away from the valley of stability, where new structure phenomena including e.g. weakening or disappearance of classical nuclear shells or rapid shape transitions can be...

Machine Learning has become a powerful tool in science. Various machine learning approaches including Neural Networks, Support Vector Machines, Gaussian Process Regression, and Ensemble of Trees have been used to either model binding energies directly or to improve binding energy predictions from existing models. This talk will discuss the successes, benefits, and disadvantages of various...

(talk will be held remotely)

Nuclear masses of neutron-deficient N$\sim$Z nuclei are pivotal for modeling astrophysical processes, such as the rapid proton-capture (rp) and $\nu$p processes, which drive nucleosynthesis in X-ray bursts and proton-rich supernova ejecta. These masses determine proton separation energies, reaction Q-values, and waiting points, directly influencing reaction flows, light curves, and p-nuclei...

The recent mass measurement of $^{70}$Kr using the $B\rho$-defined isochronous mass spectrometry yields a mass excess of $-41320(140)$ keV, indicating a 220-keV increase in binding energy compared to the AME2020 prediction. We utilize this experimental mass to probe its impact on the potential waiting point $^{68}$Se in $r$p-process and quantitatively constrain the $2p$-capture reaction flow...

There is an astute idea of the different processes that assemble heavy elements (Z > 26) in our universe, but the production sites of some of them remain unclear. The processes that generate the most exotic nuclei such as r-process, for rapid neutron capture, and rp-process, for rapid proton capture are difficult to thoroughly describe because of the lack of experimental nuclear properties of...