Mass measurements of ^{31-33}Na and ^{31-35}Mg using the TITAN MR-TOF-MS at TRIUMF's ISAC facility are presented, with the uncertainty of the ^{33}Na mass reduced by over 2 orders of magnitude. The excellent performance of the MR-TOF-MS has also allowed the discovery of a millisecond isomer in ^{32}Na. The precision obtained shows that the binding energy of the normally closed N=20 neutron shell reaches a minimum for ^{32}Mg but increases significantly for ^{31}Na, hinting at the possibility of enhanced shell strength toward the unbound ^{28}O. We compare the results with new ab initio predictions that raise intriguing questions of nuclear structure beyond the dripline.

Mass measurements of ^31-33Na and ^31-35Mg using the TITAN MR-TOF-MS at TRIUMF's ISAC facility are presented, with the uncertainty of the ^33Na mass reduced by over two orders of magnitude. The excellent performance of the MR-TOF-MS has also allowed the discovery of a millisecond isomer in ^32Na. The precision obtained shows that the binding energy of the normally closed N = 20 neutron shell reaches a minimum for ^32Mg but increases significantly for ^31Na, hinting at the possibility of enhanced shell strength toward the unbound ^28O. We compare the results with new ab initio predictions that raise intriguing questions of nuclear structure beyond the dripline.

The prediction of isotopic abundances resulting from the rapid neutron capture process (r process) requires high-precision mass measurements. Using TITAN's on-line time-of-flight spectrometer, first time mass measurements are performed for ^{83}Zn and ^{86}Ga. These measurements reduced uncertainties, and are used to calculate isotopic abundances near the first r-process abundance peak using astrophysical conditions present during a binary neutron star (BNS) merger. Good agreement in abundance across a range of trajectories is found when comparing to several metal-poor stars while also strongly deviating from the solar r-process pattern. These findings point to a high degree of sensitivity to the electron fraction of a BNS merger on the final elemental abundance pattern for certain elements near the first r-process peak while others display universality. We find that small changes in electron fraction can produce distinct abundance patterns that match those of metal-poor stars with different classifications.

We report precision mass measurements of 74-76Sr performed with the TITAN multiple-reflection time-of- flight mass spectrometer. This marks a first-time mass measurement of 74Sr and gives increased mass precision to both 75Sr and 76Sr, which were previously measured using storage ring and Penning trap methods, respectively. This completes the A = 74, T = 1 isospin triplet and gives increased precision to the A = 75, T = 1/2 isospin doublet, which are both the heaviest experimentally evaluated triplets and doublets to date. The new data allow us to evaluate coefficients of the isobaric multiplet mass equation for the first time at A = 74 and with increased precision at A = 75. With increased precision of 75Sr, we confirm the recent measurement reported by CSRe that was used to remove a staggering anomaly in the doublets. New ab initio valence-space in-medium similarity renormalization group calculations of the T = 1 triplet are presented at A = 74. We also investigate the impact of the new mass data on the reaction flow of the rapid proton capture process in type I x-ray bursts using a single-zone model.

Isotopes at the limits of nuclear existence are of great interest for their critical role in nuclear astrophysical reactions and their exotic structure. Experimentally, exotic nuclides are challenging to address due to their low production cross-sections, overwhelming amounts of contamination, and lifetimes of typically less than a second. To this end, a Multiple-Reflection Time-of-Flight mass spectrometer at the TITAN-TRIUMF facility was built to determine atomic masses. This device is the preferred tool to work with exotic nuclides due to its ability to resolve the species of interest from contamination and short measurement cycle times, enabling mass measurements of isotopes with millisecond half-lives. With a relative precision of the order 10−7, we demonstrate why the TITAN MR-TOF MS is the tool of choice for precision mass surveys for nuclear structure and astrophysics. The capabilities of the device are showcased in this work, including new mass measurements of short-lived tin isotopes (104–107Sn) approaching the proton dripline as well as 89Zr, 90Y, and 91Y. The last three illustrate how the broadband surveys of MR-TOF MS reach beyond the species of immediate interest.

A compact ion source combining electron impact and thermal ionization has been developed and commissioned in two Multiple-Reflection Time-Of-Flight Mass Spectrometer (MR-TOF-MS) setups at the Fragment Separator Ion Catcher at the GSI Helmholtz Centre for Heavy Ion Research, Darmstadt, Germany, and at TRIUMF's Ion Trap for Atomic and Nuclear science at TRIUMF Canada's particle accelerator center, Vancouver, Canada. The ion source is notable for its compact dimensions of 50 mm in height and 68 mm in diameter. The ion source is currently in daily operation at both facilities. Design, simulations, and results of combining ions from thermal and electron-impact ionization of different gases (perfluoropropane and sulfur hexafluoride) are presented in this work. The systematic effects of heating power on the thermal source were studied in detail. The source has demonstrated stable and long-term production of reference ions over a wide mass range for the MR-TOF-MS. This versatile ion source has also been used to optimize and investigate the transport of ions with different chemical reactivity and ionization potentials.

Isotopes at the limits of nuclear existence are of great interest for their critical role in nuclear astrophysical reactions and their exotic structure. Experimentally, exotic nuclides are challenging to address due to low production cross-sections, overwhelming amounts of contamination, and lifetimes typically less than a second. To this end, a Multiple-Reflection Time-of-Flight mass spectrometer at the TITAN-TRIUMF facility was built to determine atomic masses. This device is a preferred tool to work with exotic nuclides due to its ability to resolve the species of interest from contamination and short measurement cycle times enabling mass measurements of isotopes with millisecond half-lives. With a relative precision of order $10^{-7}$, we demonstrate why the TITAN MR-TOF MS is the tool of choice for precision mass surveys for nuclear structure and astrophysics. The capabilities of the device are showcased in this work including new mass measurements of short-lived tin isotopes ($^{104-107}$Sn) approaching the proton dripline as well as $^{89}$Zr, $^{90}$Y, and $^{91}$Y. The last three illustrate how the broadband surveys of MR-TOF MS reach beyond the species of immediate interest.

New mass values measured with the TITAN MR-TOF-MS are reported for the short-lived isotopes 24−26Ne, produced at TRIUMF's ISAC facility using a uranium carbide target and cold FEBIAD ion source. A least-squares adjustment within the framework of the Atomic Mass Evaluation was performed and the improved precision of the new mass values is highlighted. The improved mass accuracy in this N=14 mid-shell region can also point to the refinement in values of the charge radii. By reducing the mass uncertainty of isotopes, their contribution of the mass shift uncertainty in laser spectroscopy can be negated. The work is part of developments for reaching the N=20 Island of Inversion, where high molecular contamination hinders mass measurements of the neon isotopes.

Mass measurements continue to provide invaluable information for elucidating nuclear structure and scenarios of astrophysical interest. The transition region between the Z=20 and 28 proton shell closures is particularly interesting due to the onset and evolution of nuclear deformation as nuclei become more neutron-rich. This provides a critical testing ground for emerging ab-initio nuclear structure models. Here, we present high-precision mass measurements of neutron-rich chromium isotopes using the sensitive electrostatic Multiple-Reflection Time-Of-Flight Mass Spectrometer (MR-TOF-MS) at TRIUMF's Ion Trap for Atomic and Nuclear Science (TITAN) facility. Our high-precision mass measurements of 59,61−63Cr confirm previous results, and the improved precision in measurements of 64−65Cr refine the mass surface beyond N=40. With the ab initio in-medium similarity renormalization group, we examine the trends in collectivity in chromium isotopes and give a complete picture of the N=40 island of inversion from calcium to nickel.

Nuclear mass measurements of isotopes are key to improving our understanding of nuclear structure across the chart of nuclides, in particular for the determination of the appearance or disappearance of nuclear shell closures. We present high-precision mass measurements of neutron-rich Ca, Ti and V isotopes performed at the TITAN and LEBIT facilities. These measurements were made using the TITAN multiple-reflection time-of-flight mass spectrometer (MR-ToF-MS) and the LEBIT 9.4T Penning trap mass spectrometer. In total, 13 masses were measured, eight of which represent increases in precision over previous measurements. These measurements refine trends in the mass surface around $N = 32$ and $N = 34$, and support the disappearance of the $N = 32$ shell closure with increasing proton number. Additionally, our data does not support the presence of a shell closure at $N = 34$.

Nuclear properties across the chart of nuclides are key to improving and validating our understanding of the strong interaction in nuclear physics. We present high-precision mass measurements of neutron-rich Fe isotopes performed at the TITAN facility. The multiple-reflection time-of-flight mass spectrometer (MR-ToFMS), achieving a resolving power greater than 600 000 for the first time, enabled the measurement of Fe63-70, including first-time high-precision direct measurements (delta m/m approximate to 10(-7)) of Fe68-70, as well as the discovery of a long-lived isomeric state in Fe-69. These measurements are accompanied by both mean-field and ab initio calculations using the most recent realizations which enable theoretical assignment of the spin-parities of the Fe-69 ground and isomeric states. Together with mean-field calculations of quadrupole deformation parameters for the Fe isotope chain, these results benchmark a maximum of deformation in the N = 40 island of inversion in Fe and shed light on trends in level densities indicated in the newly refined mass surface.

Nuclear mass measurements of isotopes are key to improving our understanding of nuclear structure across the chart of nuclides, in particular, for the determination of the appearance or disappearance of nuclear shell closures. We present high-precision mass measurements of neutron-rich Ca, Ti, and V isotopes performed at TRIUMF's Ion Trap for Atomic and Nuclear science (TITAN) and the Low Energy Beam and Ion Trap (LEBIT) facilities. These measurements were made using the TITAN multiple-reflection time-of-flight mass spectrometer (MR-ToF-MS) and the LEBIT 9.4T Penning trap mass spectrometer. In total, 13 masses were measured, 8 of which represent increases in precision over previous measurements. These measurements refine trends in the mass surface around N = 32 and N = 34, and support the disappearance of the N = 32 shell closure with increasing proton number. Additionally, our data do not support the presence of a shell closure at N = 34.

The performance of high-precision mass spectrometry of radioactive isotopes can often be hindered by large amounts of contamination, including molecular species, stemming from the production of the radioactive beam. In this paper, we report on the development of Collision-Induced Dissociation (CID) as a means of background reduction for experiments at TRIUMF's Ion Trap for Atomic and Nuclear science (TITAN). This study was conducted to characterize the quality and purity of radioactive ion beams and the reduction of molecular contaminants to allow for mass measurements of radioactive isotopes to be done further from nuclear stability. This is the first demonstration of CID at an ISOL-type radioactive ion beam facility, and it is shown that molecular contamination can be reduced up to an order of magnitude.

Background: The neutron-rich A approximate to 100, N approximate to 62 mass region is important for both nuclear structure and nuclear astrophysics. The neutron-rich segment of this region has been widely studied to investigate shape coexistence and sudden nuclear deformation. However, the absence of experimental data of more neutron-rich nuclei poses a challenge to further structure studies. The derivatives of the mass surface, namely, the two-neutron separation energy and neutron pairing gap, are sensitive to nuclear deformation and shed light on the stability against deformation in this region. This region also lies along the astrophysical r-process path, and hence precise mass values provide experimental input for improving the accuracy of the r-process models and the elemental abundances. Purpose: (a) Changes in deformation are searched for via the mass surface in the A = 104 mass region at the N = 66 mid-shell crossover. (b) The sensitivity of the astrophysical r-process abundances to the mass of Rb and Sr isotopic chains is studied. Methods: Masses of radioactive Rb and Sr isotopes are precisely measured using a Multiple-Reflection Time-of-Flight Mass Separator (MR-TOF-MS) at the TITAN facility. These mass values are used to calculate two-neutron separation energies, two-neutron shell gaps and neutron pairing gaps for nuclear structure physics, and one-neutron separation energies for fractional abundances and astrophysical findings. Results: We report the first mass measurements of Rb-103 and Sr-103 with uncertainties of less than 45 keV/c(2). The uncertainties in the mass excess value for Rb-102 and (102)5r have been reduced by a factor of 2 relative to a previous measurement. The deviations from the AME extrapolated mass values by more the 0.5 MeV have been found. Conclusions: The metrics obtained from the derivatives of the mass surface demonstrate no existence of a subshell gap or onset of deformation in the N = 66 region in Rb and Sr isotopes. The neutron pairing gaps studied in this work are lower than the predictions by several mass models. The abundances calculated using the waiting-point approximation for the r process are affected by these new masses in comparison with AME2016 mass values.

High-accuracy mass measurements of neutron-deficient Yb isotopes have been performed at TRIUMF using TITAN's multiple-reflection time-of-flight mass spectrometer (MR-TOF-MS). For the first time, an MR-TOF-MS was used on line simultaneously as an isobar separator and as a mass spectrometer, extending the measurements to two isotopes further away from stability than otherwise possible. The ground state masses of ^{150,153}Yb and the excitation energy of ^{151}Yb^{m} were measured for the first time. As a result, the persistence of the N=82 shell with almost unmodified shell gap energies is established up to the proton drip line. Furthermore, the puzzling systematics of the h_{11/2}-excited isomeric states of the N=81 isotones are unraveled using state-of-the-art mean field calculations.

We report precision mass measurements of neutron-deficient gallium isotopes approaching the proton drip line. The measurements of ^60-63Ga performed with the TITAN multiple-reflection time-of-flight mass spectrometer provide a more than threefold improvement over the current literature mass uncertainty of ^61Ga and mark the first direct mass measurement of ^60Ga. The improved precision of the ^61Ga mass has important implications for the astrophysical rp process, as it constrains essential reaction Q-values near the ^60Zn waiting point. Based on calculations with a one-zone model, we demonstrate the impact of the improved mass data on prediction uncertainties of X-ray burst models. The first-time measurement of the ^60Ga ground-state mass establishes the proton-bound nature of this nuclide; thus, constraining the location of the proton drip line along this isotopic chain. Including the measured mass of ^60Ga further enables us to extend the evaluated T=1 isobaric multiplet mass equation up to A=60.

We report high-precision mass measurements of ^{50-55}Sc isotopes performed at the LEBIT facility at NSCL and at the TITAN facility at TRIUMF. Our results provide a substantial reduction of their uncertainties and indicate significant deviations, up to 0.7 MeV, from the previously recommended mass values for ^{53-55}Sc. The results of this work provide an important update to the description of emerging closed-shell phenomena at neutron numbers N=32 and N=34 above proton-magic Z=20. In particular, they finally enable a complete and precise characterization of the trends in ground state binding energies along the N=32 isotone, confirming that the empirical neutron shell gap energies peak at the doubly magic ^{52}Ca. Moreover, our data, combined with other recent measurements, do not support the existence of a closed neutron shell in ^{55}Sc at N=34. The results were compared to predictions from both ab initio and phenomenological nuclear theories, which all had success describing N=32 neutron shell gap energies but were highly disparate in the description of the N=34 isotone.

TRIUMF’s Ion Trap for Atomic and Nuclear science (TITAN) has specialized in fast Penning Trap mass spectrometry of very short-lived radioactive isotopes. The facility has been upgraded with a Multiple-Reflection Time-of-Flight Mass Spectrometer (MR-TOF-MS) to continue its quest towards more exotic nuclides, which are critical for our understanding of nuclear structure effects far from the valley of beta stability and for the nucleosynthesis of heavy elements in explosive astrophysical environments. In this publication, we discuss the implementation, operation and performance of TITAN’s MR-TOF-MS as a stand-alone high-precision mass spectrometer and as an isobar separator. By using the novel mass-selective re-trapping technique for the isobar separation, the MR-TOF-MS can consecutively perform separation and mass measurement of the same ion population, acting as its own isobar separator. The device boosts the dynamic range and reach of the TITAN facility by several orders of magnitude. The MR-TOF-MS reaches a high mass resolving power (m/Δm∼400000), high precision and mass accuracy (δm/m<10−7), is fast (common cycle time 20ms), shows high sensitivity and very large dynamic range (ion of interest to contaminant ratios of up to 1 to 106).

A new series of neutron-rich indium mass measurements is reported from the TITAN multiple-reflection time-of-flight mass spectrometer (MR-TOF-MS). These mass measurements cover In125-134 (N = 76-85) and include ground states as well as isomeric states. The masses of nuclei in this region are known to be of great importance for accurately modeling r-process nucleosynthesis, and the significance of the reported neutron-rich indium masses is discussed in this context. Results are compared with earlier experimental data where available as well as theoretical mass models. The measurements reported here include the first mass measurements of In-133,In-134, as well as the first direct mass measurement of In-132. The masses of In125-131 ground states and several isomers were previously measured to higher precision by Penning trap mass spectrometry, which also resolved some low-lying isomers that could not be resolved in this work. The earlier Penning trap measurements serve as excellent cross-checks for the MR-TOF-MS measurements, and in some cases the MR-TOF-MS measurements improve the literature uncertainties of higher-lying isomer masses and excitation energies. A new isomeric state for In-128, I recently reported for the first time by the JYFLTRAP group, is also confirmed by the TITAN MR-TOF-MS, with a measured excitation energy of 1813(17) keV.