Session G05: FOCUS: Nuclear Physics Experiments using AMO Techniques

Live

We are developing a new method for measuring the cross section of low-yield nuclear reactions by capturing the products in a cryogenically frozen noble gas solid. Once embedded in the noble gas solid, which is optically transparent, the product atoms can be selectively identified by laser-induced fluorescence and individually counted via optical imaging to determine the cross section. Single-atom sensitivity by optical imaging is feasible because the surrounding lattice of noble gas atoms facilitates a large wavelength shift between the excitation and the emission spectrum of the product atoms. The tools and techniques from the fields of single-molecule spectroscopy and superresolution imaging in combination with an electromagnetic recoil separator, for beam and isotopic differentiation, allow for a detection scheme with near-unity efficiency, a high degree of selectivity, and single-atom sensitivity. This technique could be used to determine a number of astrophysically important nuclear reaction rates. We will report on our first tests of this approach using the Rb and Kr ion beams from the ReA3 facility at the National Superconducting Cyclotron Lab at Michigan State University.   

Live

Precision measurements of ground and excited state properties of rare nuclides, like nuclear masses and charge radii, have a wealth of applications among others in atomic-, nuclear-, astro-, neutrino- and particle physics. Recent technical developments in the manipulation and detection of radionuclides in high-precision Penning-trap mass spectrometry like the phase-imaging and Fourier-transform ion cyclotron resonance detection methods have boosted the field and allow e.g. for relative mass uncertainties at the level of 1E-11. These technical advances as well as the opening of new fields of applications like the identification of low-lying isomeric states and the measurement of not only nuclear but also electron binding energies of exotic species will be presented.   

Live

Measurements of isotope shifts of optical transitions in heavy atoms can shed light on nuclear properties, and potentially probe new physics beyond the standard model. We report measurements of the isotope shifts of two optical transitions in Nd$^+$, across a series of five zero-spin isotopes that spans the nuclear shape transition. The measurements take advantage of the high optical densities of Nd$^+$ ions that can be produced in a cryogenically cooled neutral plasma, which enabled us to precisely measure the isotope shifts of these optical transitions for the first time. The bound on the nonlinearity of the King plot constructed from the isotope shifts could inform searches for new physics. We will discuss the future prospects for ultra-precise optical measurements of isotope shifts in Nd$^+$.   

Live

In the early 2000’s, the MIT Penning trap group implemented a technique for measuring atomic mass ratios by simultaneous measurement of the cyclotron frequency of two ions in a coupled magnetron orbit [1]. Applying this technique to ion pairs of $m/q$ near 30 they achieved a fractional precision of $7 \times 10^{-12}$, still the highest precision attained for a mass ratio. With future aims of an improved mass comparison of tritium to helium-3 [2], and of the antiproton to proton, and the immediate goal of an improved value for $m_d/m_p$, we are re-developing this method using H$_2^+$ and D$^+$. (We have recently determined this mass ratio to $2 \times 10^{-11}$ using simultaneously trapped ions, but by measuring the cyclotron frequencies alternately using large and small cyclotron orbits [3]). However, the coupled magnetron orbit entails additional systematics due to increased ion-ion interaction, and because the ions are now displaced from the center of the Penning trap. Compared to $m/q = 30$, some systematics are reduced, while others are increased. [1] S. Rainville, J. K. Thompson, and D. E. Pritchard, Science 303, 334 (2004). [2] E. G. Myers, et al., Phys. Rev. Lett. 114, 013003 (2015). [3] D. Fink and E. G. Myers, Phys. Rev. Lett. 124, 013001 (2020).   

Live

Ions that are difficult to laser cool, and hence cannot be detected with fluorescence, are promising for fundamental physics research and quantum information science. We present a method to rapidly and nondestructively identify trapped dark ions by measuring the motional frequencies of dark ions co-trapped with laser-coolable bright ions. We use the $S_{1/2}$, $P_{1/2}$ and $D_{3/2}$ level structure of $\mathrm{Sr}^+$, and separately $\mathrm{Ra}^+$, to controllably amplify the ion’s motion by modifying the optical spectrum with coherent population trapping. The amplified ion motion modulates the scattered light, which we collect and Fourier transform to extract the motional frequencies, and from this the dark ion mass. The technique can be used with ions that have a lambda level structure, such as $\mathrm{Ca}^+$ and $\mathrm{Ba}^+$, and only utilizes the two lasers already required for laser cooling.   

On Demand

We report a fourfold improvement in the determination of nuclear magnetic moments for neutron-deficient isotopes of francium 207-213, reducing the uncertainties from 2\% for most isotopes to 0.5\%. These are found by comparing our high-precision calculations of hyperfine structure constants for the ground states with experimental values. In particular, we show the importance of a careful modeling of the Bohr-Weisskopf effect, which arises due to the finite nuclear magnetization distribution. This effect is particularly large in Fr and until now has not been modeled with sufficiently high accuracy. An improved understanding of the nuclear magnetic moments and Bohr-Weisskopf effect are crucial for benchmarking the atomic theory required in precision tests of the standard model, in particular atomic parity violation studies, that are underway in francium. B. M. Roberts and J. S. M. Ginges, arXiv:2001.01907 (2020).   

Electric Field Simulation of the Field Cage for Dual Phase Deep Underground Neutrino Experiment

The Deep Underground Neutrino Experiment (DUNE) is the U.S. flagship experiment being designed to study the characteristics of neutrinos which make up a quarter of the fundamental particle map in 2026. This subatomic particle can reveal various unsolved mysteries like the existence of matter in the universe. In DUNE neutrino interactions will be captured inside a 12m x 12m x 60m active volume time projection chamber using liquid argon as the medium. The ionization electrons due to the traversing charged particles from neutrino interactions drift through the liquid argon and detected. The field cage which is constructed by modules made of aluminum strips and fiber-glass I-beams provides a uniform electric field for these electrons to drift at the uniform speed. After analyzing the performance of the previous design of field cage used in a prototype detector, several improvements were made to the field cage design for DUNE. Before the actual construction and test of field cage, we are simulating the electric field across the new field cage design. In this talk, I would be describing the new design of the field cage and the resulting electric field map of the new field cage design.