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The accurate determination of atomic final states following nuclear $\ensuremath{\beta}$ decay plays an important role in several experiments. In particular, the charge state distributions of ions following nuclear $\ensuremath{\beta}$ decay are important for determinations of the $\ensuremath{\beta}\text{\ensuremath{-}}\ensuremath{\nu}$ angular correlation with improved precision. Beyond the hydrogenic cases, the decay of neutral $^{6}\mathrm{He}$ presents the simplest case. Our measurement aims at providing benchmarks to test theoretical calculations. The kinematics of ${\mathrm{Li}}^{n+}$ ions produced following the $\ensuremath{\beta}$ decay of $^{6}\mathrm{He}$ within an electric field were measured using $^{6}\mathrm{He}$ atoms in the metastable $(1s2s,^{3}S_{1})$ and $(1s2p,^{3}P_{2})$ states confined by a magneto-optical trap. The electron shakeoff probabilities were deduced, including their dependence on ion energy. We find significant discrepancies on the fractions of Li ions in the different charge states with respect to a recent calculation.

A new approach to β-delayed neutron spectroscopy has been demonstrated that circumvents the many limitations associated with neutron detection by instead inferring the decay branching ratios and energy spectra of the emitted neutrons by studying the nuclear recoil. Using the Beta-decay Paul Trap, fission-product ions were trapped and confined to within a 1 -mm 3 volume under vacuum using only electric fields. Results from recent measurements of 137 I + and plans for development of a dedicated ion trap for future experiments using the intense fission fragment beams from the Californium Rare Isotope Breeder Upgrade (CARIBU) facility at Argonne National Laboratory are summarized. The improved nuclear data that can be collected is needed in many fields of basic and applied science such as nuclear energy, nuclear astrophysics, and stockpile stewardship.

The most sensitive direct method to establish the absolute neutrino mass is observation of the endpoint of the tritium beta-decay spectrum. Cyclotron Radiation Emission Spectroscopy (CRES) is a precision spectrographic technique that can probe much of the unexplored neutrino mass range with $\mathcal{O}({\rm eV})$ resolution. A lower bound of $m(\nu_e) \gtrsim 9(0.1)\, {\rm meV}$ is set by observations of neutrino oscillations, while the KATRIN Experiment - the current-generation tritium beta-decay experiment that is based on Magnetic Adiabatic Collimation with an Electrostatic (MAC-E) filter - will achieve a sensitivity of $m(\nu_e) \lesssim 0.2\,{\rm eV}$. The CRES technique aims to avoid the difficulties in scaling up a MAC-E filter-based experiment to achieve a lower mass sensitivity. In this paper we review the current status of the CRES technique and describe Project 8, a phased absolute neutrino mass experiment that has the potential to reach sensitivities down to $m(\nu_e) \lesssim 40\,{\rm meV}$ using an atomic tritium source., Comment: 19 pages, 8 figures, to be published in Journal of Physics G

We present simple derivations of nuclear $\beta$-decay correlations with an emphasis on the special role of helicity. This provides a good opportunity to teach students about helicity and chirality in particle physics through exercises using simple aspects of quantum mechanics. In addition, this paper serves as an introduction to nuclear $\beta$-decay correlations from both a theoretical and experimental vantage. This article can be used to introduce students to ongoing experiments searching for hints of new physics in the low-energy precision frontier.

The β - decay Paul trap is a linear radiofrequency-quadrupole ion trap that has been developed for precision β - decay studies. The design of the trap electrodes allows a variety of radiation detectors to surround the cloud of trapped ions. The momentum of the low-energy recoiling daughter nuclei following β decay is negligibly perturbed by scattering and is available for study. This advantageous property of traps allows the kinematics of particles that are difficult or even impossible to directly detect to be precisely reconstructed using conservation of energy and momentum. An ion-trap system offers several advantages over atom traps, such as higher trapping efficiencies and element-independent capabilities. The first precision experiment using this system is a measurement of β - decay angular correlations in the decay of 8Li performed by inferring the momentum of the neutrino from the kinematic shifts imparted to the breakup α particles. Many other β - decay studies that would benefit from a determination of the nuclear recoil can be performed with this system.

International audience; We have developed a position response calibration method for a micro-channel plate (MCP) detector with a delay-line anode position readout scheme. Using an {\em in situ} calibration mask, an accuracy of 8~$\mu$m and a resolution of 85~$\mu$m (FWHM) have been achieved for MeV-scale $\alpha$ particles and ions with energies of $\sim$10~keV. For high statistics experiments, this method can be directly employed with the experimental data without any dedicated calibration runs. The improved performance of the MCP detector can find applications in many fields of AMO and nuclear physics. In our case, it helps reducing systematic uncertainties in a high-precision nuclear $\beta$-decay experiment.

In the standard model, the weak interaction is formulated with a purely vector-axial-vector (V-A) structure. Without restriction on the chirality of the neutrino, the most general limits on tensor currents from nuclear β decay are dominated by a single measurement of the β-ν[over ¯] correlation in ^{6}He β decay dating back over a half century. In the present work, the β-ν[over ¯]-α correlation in the β decay of ^{8}Li and subsequent α-particle breakup of the ^{8}Be^{*} daughter was measured. The results are consistent with a purely V-A interaction and in the case of couplings to right-handed neutrinos (C_{T}=-C_{T}^{'}) limits the tensor fraction to |C_{T}/C_{A}|^{2}

International audience; Synopsis Correlations between β decay products are sensitive observables to look for exotic contributions to the weak interaction excluded by the Standard Model of particle physics. To precisely measure the β − ν angular correlation parameter, a βν , in 6 He β decay, the radioactive atoms are trapped in a magneto-optical trap and the momentum of β particles and 6 Li recoil ions are measured in coincidence. The shake-off process, leading to higher charge states of the Li, plays an important role in this observation and must be studied carefully. Its study provides stringent tests of the sudden approximation for atomic calculations in this few electron system.

It has been understood since 1897 that accelerating charges must emit electromagnetic radiation. Cyclotron radiation, the particular form of radiation emitted by an electron orbiting in a magnetic field, was first derived in 1904. Despite the simplicity of this concept, and the enormous utility of electron spectroscopy in nuclear and particle physics, single-electron cyclotron radiation has never been observed directly. Here we demonstrate single-electron detection in a novel radiofrequency spec- trometer. We observe the cyclotron radiation emitted by individual magnetically-trapped electrons that are produced with mildly-relativistic energies by a gaseous radioactive source. The relativistic shift in the cyclotron frequency permits a precise electron energy measurement. Precise beta elec- tron spectroscopy from gaseous radiation sources is a key technique in modern efforts to measure the neutrino mass via the tritium decay endpoint, and this work demonstrates a fundamentally new approach to precision beta spectroscopy for future neutrino mass experiments., 6 pages, 3 figures

A measurement of the $\ensuremath{\alpha}\mathrm{\text{\ensuremath{-}}}\ensuremath{\beta}\mathrm{\text{\ensuremath{-}}}\overline{\ensuremath{\nu}}$ angular correlation in the Gamow-Teller decay $^{8}\mathrm{Li}\ensuremath{\rightarrow}^{8}\mathrm{Be}^{*}+\overline{\ensuremath{\nu}}+\ensuremath{\beta}$, $^{8}\mathrm{Be}^{*}\ensuremath{\rightarrow}\ensuremath{\alpha}+\ensuremath{\alpha}$ has been performed using ions confined in a linear Paul trap surrounded by silicon detectors. The energy difference spectrum of the $\ensuremath{\alpha}$ particles emitted along and opposite the direction of the $\ensuremath{\beta}$ particle is consistent with the standard model prediction and places a limit of 3.1% (95.5% confidence level) on any tensor contribution to the decay. From this result, the amplitude of any tensor component ${C}_{T}$ relative to that of the dominant axial-vector component ${C}_{A}$ of the electroweak interaction is limited to $|{C}_{T}/{C}_{A}|l0.18$ (95.5% confidence level). This experimental approach is facilitated by several favorable features of the $^{8}\mathrm{Li}$ $\ensuremath{\beta}$ decay and has different systematic effects than the previous $\ensuremath{\beta}\mathrm{\text{\ensuremath{-}}}\overline{\ensuremath{\nu}}$ correlation results for a pure Gamow-Teller transition obtained from studying $^{6}\mathrm{He}$ $\ensuremath{\beta}$ decay.

The Canadian Penning Trap mass spectrometer has made mass measurements of 33 neutron-rich nuclides provided by the new Californium Rare Isotope Breeder Upgrade (CARIBU) facility at Argonne National Laboratory. The studied region includes the 132Sn double shell closure and ranges in Z from In to Cs, with Sn isotopes measured out to A = 135, and the typical measurement precision is at the 100 ppb level or better. The region encompasses a possible major waiting point of the astrophysical r process, and the impact of the masses on the r process is shown through a series of simulations. These first-ever simulations with direct mass information on this waiting point show significant increases in waiting time at Sn and Sb in comparison with commonly used mass models, demonstrating the inadequacy of existing models for accurate r-process calculations., Comment: 5 pages, 3 figures, accepted to Physical Review Letters

A novel technique for beta-delayed neutron spectroscopy has been developed using trapped radioactive ions. The neutron energy spectrum was reconstructed by measuring the time of flight (TOF) of the nuclear recoil following neutron emission, thereby avoiding all the challenges associated with neutron detection such as backgrounds from scattered neutrons and gamma rays and complicated detector-response functions. A proof-of-principle measurement was conducted on 137I+ by delivering ions from a 252Cf source, confining them in a linear Paul trap surrounded by radiation detectors, and measuring the neutron energy spectrum and branching ratio by detecting the beta and recoil ions in coincidence. Systematic effects were explored by determining the branching ratio three ways. Improvements to achieve higher detection efficiency, better energy resolution, and a lower neutron energy threshold were implemented by upgrading the detectors and optimizing the trapping apparatus. These improvements were demonstrated in a campaign of measurements including 138I, which is a standard beta-delayed neutron precursor outlined by a recent IAEA report on delayed neutron measurements.

The masses of 40 neutron-rich nuclides from Z = 51 to 64 were measured at an average precision of $\delta m/m= 10^{-7}$ using the Canadian Penning Trap mass spectrometer at Argonne National Laboratory. The measurements, of fission fragments from a $^{252}$Cf spontaneous fission source in a helium gas catcher, approach the predicted path of the astrophysical $r$ process. Where overlap exists, this data set is largely consistent with previous measurements from Penning traps, storage rings, and reaction energetics, but large systematic deviations are apparent in $\beta$-endpoint measurements. Differences in mass excess from the 2003 Atomic Mass Evaluation of up to 400 keV are seen, as well as systematic disagreement with various mass models., Comment: 15 pages, 16 figures. v2 updated, published in Physical Review C

The reaction paths of two proposed nucleosynthetic processes on the proton-rich side of stability, the $rp$ and $\ensuremath{\nu}p$ processes, pass through a region of isotopes between Mo and Pd where masses had long gone unmeasured. Precise knowledge of the paths and final abundances of these two processes has been limited by the corresponding lack of precision in the proton-separation energies ${S}_{p}$ when derived from extrapolated masses. The masses of 18 neutron-deficient isotopes of Nb, Mo, Tc, Ru, and Rh have been measured using the Canadian Penning trap mass spectrometer. Three of the masses presented, ${}^{90}$Mo, ${}^{91}$Mo, and ${}^{93}$Tc, provide the first direct measurement of the masses of these nuclides, and the others provide confirmation of recent measurements using other Penning traps. Included in this work is a measurement of the mass of ${}^{87}$Mo, which differs by $3.7\ensuremath{\sigma}$ from the mass presented in the 2003 Atomic Mass Evaluation. This leads to a change in the ${S}_{p}$ value of ${}^{88}$Tc which reduces the suppression of flow of the $\ensuremath{\nu}p$-process path through ${}^{87}$Mo($p,\ensuremath{\gamma}$)${}^{88}$Tc reported following the mass measurement of ${}^{88}$Tc [C. Weber et al., Phys. Rev. C 78, 054310 (2008)]. This in turn affects the resulting $\ensuremath{\nu}p$-process abundances.

The double-{beta}-decay Q values of {sup 130}Te, {sup 128}Te, and {sup 120}Te have been determined from parent-daughter mass differences measured with the Canadian Penning Trap mass spectrometer. The {sup 132}Xe-{sup 129}Xe mass difference, which is precisely known, was also determined to confirm the accuracy of these results. The {sup 130}Te Q value was found to be 2527.01{+-}0.32 keV, which is 3.3 keV lower than the 2003 Atomic Mass Evaluation recommended value and is consistent with another recent Penning trap measurement. The {sup 128}Te and {sup 120}Te Q values were found to be 865.87{+-}1.31 and 1714.81{+-}1.25 keV, respectively. For {sup 120}Te, this reduction in uncertainty of nearly a factor of 8 opens up the possibility of using this isotope for sensitive searches for neutrinoless double-electron capture and electron capture with {beta}{sup +}emission.

The proposed {nu}p process, which occurs in the early time proton-rich neutrino winds of core-collapse supernovae, has the potential to resolve the long-standing uncertainty in the production of the light p-nuclei {sup 92}Mo and {sup 94}Mo. A recent study incorporating this {nu}p process has indicated that the proton separation energy S{sub p} of {sup 93}Rh is especially important in determining the relative production of these two isotopes. To reproduce the observed solar {sup 92}Mo/{sup 94}Mo abundance ratio of 1.57 a S{sub p} value for {sup 93}Rh of 1.64 {+-} 0.1 MeV is required. The previously unknown masses of {sup 92}Ru and {sup 93}Rh have been measured with the Canadian Penning Trap mass spectrometer resulting in an experimental value for S{sub p}({sup 93}Rh) of 2.007 {+-} 0.009 MeV. This implies that with our current understanding of the conditions in core-collapse supernova explosions the {nu}p process is not solely responsible for the observed solar {sup 92}Mo/{sup 94}Mo abundance ratio.

The proposed cyclotron gas-stopping scheme for the efficient thermalization of intense rare isotope beams is examined. Simulations expand on previous studies and expose many complications of such an apparatus arising from physical effects not accounted for properly in previous work. The previously proposed cyclotron gas-stopper geometry is found to have a near null efficiency, but extended simulations suggest that a device with a much larger pole gap could achieve a stopping efficiency approaching roughly 90% and at least a 10 times larger acceptance. However, some of the advantages that were incorrectly predicted in previous simulations for high intensity operation of this device are compromised., Comment: Accepted for publication in Nuclear Inst. and Methods in Physics Research, A