No Arabic abstract
Several modes of electroweak radioactive decay require an interaction between the nucleus and bound electrons within the constituent atom. Thus, the probabilities of the respective decays are not only influenced by the structure of the initial and final states in the nucleus, but can also depend strongly on the atomic charge. Conditions suitable for the partial or complete ionization of these rare isotopes occur naturally in hot, dense astrophysical environments, but can also be artificially generated in the laboratory to selectively block certain radioactive decay modes. Direct experimental studies on such scenarios are extremely difficult due to the laboratory conditions required to generate and store radioactive ions at high charge states. A new electron-beam ion trap (EBIT) decay setup with the TITAN experiment at TRIUMF has successfully demonstrated such techniques for performing spectroscopy on the radioactive decay of highly charged ions.
This article presents an upgraded in-trap decay spectroscopy apparatus which has been developed and constructed for use with TRIUMFs Ion Trap for Atomic and Nuclear science (TITAN). This device consists of an open-access electron-beam ion-trap (EBIT), which is surrounded radially by seven low-energy planar Si(Li) detectors. The environment of the EBIT allows for the detection of low-energy photons by providing backing-free storage of the radioactive ions, while guiding charged decay particles away from the trap centre via the strong (up to 6 T) magnetic field. In addition to excellent ion confinement and storage, the EBIT also provides a venue for performing decay spectroscopy on highly-charged radioactive ions. Recent technical advancements have been able to provide a significant increase in sensitivity for low-energy photon detection, towards the goal of measuring weak electron-capture branching ratios of the intermediate nuclei in the two-neutrino double beta ($2 ubetabeta$) decay process. The design, development, and commissioning of this apparatus are presented together with the main physics objectives. The future of the device and experimental technique are discussed.
Precision spectroscopy of atomic systems is an invaluable tool for the advancement of our understanding of fundamental interactions and symmetries. Recently, highly charged ions (HCI) have been proposed for sensitive tests of physics beyond the Standard Model and as candidates for high-accuracy atomic clocks. However, the implementation of these ideas has been hindered by the parts-per-million level spectroscopic accuracies achieved to date. Here, we cool a trapped HCI to the lowest reported temperatures, and introduce coherent laser spectroscopy on HCI with an eight orders of magnitude leap in precision. We probe the forbidden optical transition in $^{40}$Ar$^{13+}$ at 441 nm using quantum-logic spectroscopy and measure both its excited-state lifetime and $g$-factor. Our work ultimately unlocks the potential of HCI, a large, ubiquitous atomic class, for quantum information processing, novel frequency standards, and highly sensitive tests of fundamental physics, such as searching for dark matter candidates or violations of fundamental symmetries.
Storage rings have been employed over three decades in various kinds of nuclear and atomic physics experiments with highly charged ions. Storage ring operation and precision physics experiments benefit from the availability of beam cooling which is common to nearly all facilities. The basic aspects of the storage ring components and the operation of the ring in various ion-optical modes as well as the achievable beam conditions are described. Ion storage rings offer unparalleled capabilities for high precision experiments with stable and radioactive beams. The versatile techniques and methods for beam manipulations allow for preparing beams of highest quality at any energy of interest. The rings are therefore part of the experiment . Recent experiments conducted in a wide energy range and with various experimental installations are discussed. An overview of active and planned facilities, new experimental set-ups and proposed physics experiments completes this review.
We report linear polarization measurements of x rays emitted due to dielectronic recombination into highly charged krypton ions. The ions in the He-like through O-like charge states were populated in an electron beam ion trap with the electron beam energy adjusted to recombination resonances in order to produce $Kalpha$ x rays. The x rays were detected with a newly developed Compton polarimeter using a beryllium scattering target and 12 silicon x-ray detector diodes sampling the azimuthal distribution of the scattered x rays. The extracted degrees of linear polarization of several dielectronic recombination transitions agree with results of relativistic distorted--wave calculations. We also demonstrate a high sensitivity of the polarization to the Breit interaction, which is remarkable for a medium-$Z$ element like krypton. The experimental results can be used for polarization diagnostics of hot astrophysical and laboratory fusion plasmas.
We present the first investigation on the effect of highly charged ion bombardment on a manganese arsenide thin film. The MnAs films, 150 nm thick, are irradiated with 90 keV Ne$^{9+}$ ions with a dose varying from $1.6times10^{12}$ to $1.6times10^{15}$ ions/cm$^2$. The structural and magnetic properties of the film after irradiation are investigated using different techniques, namely, X-ray diffraction, magneto-optic Kerr effect and magnetic force microscope. Preliminary results are presented. From the study of the lattice spacing, we measure a change on the film structure that depends on the received dose, similarly to previous studies with other materials. Investigations on the surface show a strong modification of its magnetic properties.