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The electron-beam ion trap (EBIT) at the National Institute of Standards and Technology (NIST) was employed for the measurement and detailed analysis of the $\ensuremath{\delta}\ensuremath{\lambda}(^{124}\mathrm{Xe},^{136}\mathrm{Xe})$ isotopic shifts of the Al-like $3{s}^{2}3p\phantom{\rule{4pt}{0ex}}^{2}P_{1/2}\ensuremath{-}3{s}^{2}3p\phantom{\rule{4pt}{0ex}}^{2}P_{3/2}$, Al-like $3{s}^{2}3p\phantom{\rule{4pt}{0ex}}^{2}P_{1/2}\ensuremath{-}3{s}^{2}3d\phantom{\rule{4pt}{0ex}}^{2}D_{3/2}$, Mg-like $3{s}^{2}\phantom{\rule{4pt}{0ex}}^{1}S_{0}\ensuremath{-}3s3p\phantom{\rule{4pt}{0ex}}^{1}P_{1}$, Mg-like $3{s}^{2}\phantom{\rule{4pt}{0ex}}^{1}S_{0}\ensuremath{-}3s3p\phantom{\rule{4pt}{0ex}}^{3}P_{1}$, Na-like $3s\phantom{\rule{4pt}{0ex}}^{2}S_{1/2}\ensuremath{-}3p\phantom{\rule{4pt}{0ex}}^{2}P_{1/2}$ (${D}_{1}$), and Na-like $3s\phantom{\rule{4pt}{0ex}}^{2}S_{1/2}\ensuremath{-}3p\phantom{\rule{4pt}{0ex}}^{2}P_{3/2}$ (${D}_{2}$) transitions. Systematic analysis revealed possible line blends and contributing experimental uncertainties. Highly accurate atomic-structure calculations were conducted and used to determine the $\ensuremath{\delta}{\ensuremath{\langle}{r}^{2}\ensuremath{\rangle}}^{136,124}$ difference in the mean-square nuclear charge radii of the two xenon isotopes. In the present work, $\ensuremath{\delta}{\ensuremath{\langle}{r}^{2}\ensuremath{\rangle}}^{136,124}$ of 0.276 $\ifmmode\pm\else\textpm\fi{}$ 0.030 ${\mathrm{fm}}^{2}$ was obtained from the weighted average of the Na-like ${D}_{1}$, Mg-like $3{s}^{2}\ensuremath{-}3s3p$ and Al-like $3{s}^{2}3p\ensuremath{-}3{s}^{2}3p$ and $3{s}^{2}3p\ensuremath{-}3{s}^{2}3d$ transitions. This result confirms the value previously determined from the Na-like ${D}_{1}$ transition of 0.269 $\ifmmode\pm\else\textpm\fi{}$ 0.042 ${\mathrm{fm}}^{2}$. The uncertainty of our result is half of that of previous results for the same isotopes obtained from x-ray spectroscopy of muonic atoms, laser spectroscopy of neutral xenon atoms, and a global evaluation of charge radii. Our result is slightly outside the uncertainty of the value obtained from a King plot analysis of comparable precision. The present work illustrates that extreme-ultraviolet spectroscopy of highly charged ions is a viable approach for measurements of charge nuclear radii differences and can be used to benchmark conventional methods.

The ReA post-accelerator of the National Superconducting Cyclotron Laboratory employs an Electron-Beam Ion Trap (EBIT) as a charge breeder to reaccelerate rare-isotope beams to several MeV/u. The Facility for Rare-Isotope Beams (FRIB) is near completion and will provide RIB rates expected to exceed in some cases 1010 particles/s. The ReA EBIT operates with an electron current of 300 – 600 mA, corresponding to an electron current density of 170 – 340 A/cm2 and a maximum trap capacity of 1010 elementary charges, which can be insufficient to handle high FRIB rates. A High-Current Electron-Beam Ion Source (HCEBIS) has been constructed based on the backbones of the TEST EBIS from the Brookhaven National Laboratory. By using a 4-A electron beam, a current density of 298 A/cm2 and a maximum trap capacity of 2.4×10n elementary charges can be achieved. This paper presents the status of the HCEBIS. It also includes results of electron- and ion-beam simulations and discusses electron-beam commissioning plans.

Electron beam ion sources and traps (EBIST) produce and trap highly charged atomic ions with an electron beam of high current density. The ions are confined in the radial space-charge potential of the electron beam and a long square-shaped axial electrostatic potential well. An important field of application of EBIST is charge breeding of highly charged ions at radioactive ion beam facilities. There, highly charged radioactive isotopes are accelerated by particle accelerators for experiments in nuclear astrophysics and to study the structure of unstable nuclei. The width in time of the ion pulses ejected from EBIST can often contain too many ions for nuclear physics detection systems to efficiently detect all single radioactive isotopes or related events. Neglecting the influence of ion–ion collisions on the extraction rate, this publication derives, for different initial thermal energy distributions of the trapped ions, the time-dependent trap-opening functions to stretch the time distribution of ion pulses ejected from an EBIST trapping potential for the release of ions at a constant rate over an extended extraction period.

In radioactive ion beam experiments, beams containing isomers can be of interest in probing nuclear structure and informing astrophysical reaction rates. While the production of mixed in-flight ground state and isomer beams using nucleon transfer can be generally understood through distorted wave Born approximation methodology, low-spin isomer production via fast fragmentation is relatively unstudied. To attain a practical understanding of low-spin isomer production using fast fragmentation beams, a test case of $^{38}\mathrm{K}/^{38m}\mathrm{K}$ was studied at the National Superconducting Cyclotron Laboratory's ReAccelerated Beam facility. Starting from lise++ predictions, the fragmentation momentum distribution was sampled to determine isomer production. In addition, the effects of the gas stopper gradient and charge breeding times were examined. In the case of $^{38}\mathrm{K}$, isomer production peaks at $\ensuremath{\sim}57%$. This maximum is observed just off the lise++ predicted optimum magnetic rigidity, with only small losses in beam intensity within a few percent of this optimum rigidity setting. Control of the isomer fraction was also achieved through the modification of charge breeding times. Fast fragmentation appears to be a feasible method for production of low-spin isomeric beams, but additional study is necessary to better describe the mechanism involved.

The electron-beam ion trap (EBIT) charge breeder of the ReA post-accelerator, located at the National Superconducting Cyclotron Laboratory (Michigan State University), started on-line operation in September 2015. Since then, the EBIT has delivered many pilot beams of stable isotopes and several rare-isotope beams. An operating aspect of the ReA EBIT is the breeding of high charge states to reach high reaccelerated beam energies. Efficiencies in single charge states of more than 20% were measured with ${^{39}\mathrm{K}}^{15+}$, ${^{85}\mathrm{Rb}}^{27+}$, ${^{47}\mathrm{K}}^{17+}$, and ${^{34}\mathrm{Ar}}^{15+}$. Producing high charge states demands long breeding times. This reduces the ejection frequency and, hence, increases the number of ions ejected per pulse. Another operating aspect is the ability to spread the distribution in time of the ejected ion pulses to lower the instantaneous rate delivered to experiments. Pulse widths were stretched from a natural $25\text{ }\text{ }\ensuremath{\mu}\mathrm{s}$ up to $\ensuremath{\sim}70\text{ }\text{ }\mathrm{ms}$. This publication reviews the progress of the ReA EBIT system over the years and presents the results of charge-breeding efficiency measurements and pulse-stretching tests obtained with stable- and rare-isotope beams. Studies performed with high sensitivity to identify and quantify stable-isotope contaminants from the EBIT are also presented, along with a novel method for purifying beams.

The ReA post-accelerator at the National Superconducting Cyclotron Laboratory (NSCL) employs an electron beam ion trap (EBIT) as a charge breeder. A Monte-Carlo simulation code was developed to calculate the transverse acceptance phase space of the EBIT for continuously injected ion beams and to determine the capture efficiency in dependence of the transverse beam emittance. For this purpose, the code records the position and time of changes in charge state of injected ions, leading either to capture or loss of ions. To benchmark and validate the code, calculated capture efficiencies were compared with results from a geometrical model and measurements. The results of the code agree with the experimental findings within a few 10%. The code predicts a maximum total capture efficiency of 50% for EBIT parameters readily achievable and an efficiency of up to 80% for an electron beam current density of 1900 A/cm 2 .

The variation in mean-square nuclear charge radius of xenon isotopes was measured utilizing a new method based on extreme ultraviolet spectroscopy of highly charged Na-like ions. The isotope shift of the Na-like D1 (3s $^{2}$S$_{1/2}$ - 3p $^2$P$_{1/2}$) transition between the $^{124}$Xe and $^{136}$Xe isotopes was experimentally determined using the electron beam ion trap facility at the National Institute of Standards and Technology. The mass shift and the field shift coefficients were calculated with enhanced precision by relativistic many-body perturbation theory and multi-configuration Dirac-Hartree-Fock method. The mean-square nuclear charge radius difference was found to be $\delta^{136, 124}$ = 0.269(0.042) fm$^2$. Our result has smaller uncertainty than previous experimental results and agrees with the recommended value by Angeli and Marinova [I. Angeli and K. P. Marinova, At. Data and Nucl. Data Tables {\bf 99}, 69-95 (2013)]., Comment: 6 pages, 3 figures

At accelerator facilities, charge breeders convert ion beams of low charge states (mostly singly charged) into multiply charged ion beams to extend the energy range of beams accelerated and delivered to experiments. A field of application that has grown over the past decades is charge breeding of rare-isotope beams (RIBs). RIBs are of interest in nuclear physics and astrophysics to study nuclear structure and the origin of the chemical elements. Several postaccelerators at RIB facilities in operation and under construction employ electron-beam ion source and trap (EBIS/T) breeders. Compared with other breeding techniques, EBIS/Ts have many advantages: high efficiency, fast and variable breeding times, small beam emittances, and high beam purity. This publication reviews the use of EBIS/T breeders at RIB facilities with a particular emphasis on their use for postacceleration along with advances in related fields.

Short breeding times, narrow charge state distributions, low background, high efficiency, and the flexible time structure of the ejected low-emittance ion pulses are among the most attractive features of electron beam ion source or trap (EBIS/T) based charge breeders. Significant progress has been made to further improve these properties: Several groups are working to increase current densities towards 10(3) or even 10(4) A/cm(2). These current densities will become necessary to deliver high charge states of heavy nuclei in a short time and/or provide sufficient space-charge capacity to handle high-current ion beams in next-generation rare-isotope beam (RIB) facilities. Efficient capture of continuous beams, attractive because of its potential of handling highest-current ion beams, has become possible with the development of high-density electron beams of >1 A. Requests for the time structure of the charge bred ion pulse range from ultra-short pulses to quasi-continuous beams. Progress is being made on both ends of this spectrum, by either dividing the extracted charge in many pulse-lets, adjusting the extraction potential for a near-uniform long pulse, or adding dedicated devices to spread the ion bunches delivered from the EBIS/T in time. Advances in EBIS/T charge state breeding are summarized, including recent results with NSCL's ReA EBIS/T charge breeder.

At the NSCL a reaccelerator with design end energy of 3 MeV/u for 238U, called ReA3, is approaching the end of construction. ReA3 will be coupled to a gas stopper at the NSCL fragmentation facility to provide rare-isotope beams of nuclides not available at ISOL facilities in this energy range. An Electron Beam Ion Trap (EBIT) will be used to provide highly charged ions at an energy of about 12 keV/u. The charge breeder is followed by a room-temperature radiofrequency quadrupole (RFQ) and a series of superconducting linear accelerator structures. Initial commissioning results from the EBIT and its charge-over-mass separator are presented.

TITAN (TRIUMF's Ion Traps for Atomic and Nuclear science) is a novel online facility for high-precision mass measurements on short-lived isotopes. TITAN is the only such facility that employs an Electron-Beam Ion Trap (EBIT) charge-state breeder to produce highly charged ions for their use to increase the precision of mass measurements. We describe the recently commissioned TITAN EBIT and present the results of first injection, charge breeding, and extraction tests performed with stable and radioactive ions.

Spectra in the extreme ultraviolet range from 107 to 353 A emitted from Fe ions in various ionization stages have been observed at the Heidelberg electron beam ion trap (EBIT) with a flat-field grating spectrometer. A series of transition lines and their intensities have been analyzed and compared with collisional-radiative simulations. The present collisional-radiative model reproduces well the relative line intensities and facilitates line identification of ions produced in the EBIT. The polarization effect on the line intensities resulting from nonthermal unidirectional electron impact was explored and found to be significant (up to 24%) for a few transition lines. Based upon the observed line intensities, relative charge state distributions (CSD) of ions were determined, which peaked at Fe23+ tailing toward lower charge states. Another simulation on ion charge distributions including the ionization and electron capture processes generated CSDs which are in general agreement with the measurements. By observing intensity ratios of specific lines from levels collisionally populated directly from the ground state and those starting from the metastable levels of Fe XXI, Fe X and other ionic states, the effective electron densities were extracted and found to depend on the ionic charge. Furthermore, it was found that the overlap of the ion cloud with the electron beam estimated from the effective electron densities strongly depends on the charge state of the ion considered, i.e. under the same EBIT conditions, higher charge ions show less expansion in the radial direction.

Double beta decay (ββ) is a nuclear decay mode expected to appear in at least two varieties, the double-neutrino (2ν) and the zero-neutrino (0ν) mode. The 0νββ-decay is of particular interest as it requires the neutrino to be a Majorana particle. The search for such a decay is presently being carried out or planned in a number of experiments, such as EXO, MAJORANA, GERDA, CUORE, COBRA, NEMO-III and SNO+. The 0ν-decay rate depends on the neutrino mass but, unfortunately, also on a rather complex nuclear matrix element, making the extraction of the mass heavily dependent on the underlying theoretical nuclear model. However, all theoretical models can readily be tested against the 2ν mode, which, unlike its 0ν counterpart, only involves simple Gamow–Teller nuclear matrix elements. These elements can be determined experimentally either through charge-exchange reactions or, for the ground-state transition, through the electron capture (EC) or single β-decay of the intermediate odd–odd nucleus. The present program is geared towards the measurement of the EC branching ratios (BR). In most cases, these ratios are poorly known or not known at all, because EC is usually suppressed by several orders of magnitude compared to the β-decay counterpart due to energy considerations. Traditional methods for measuring these ratios have so far suffered from overwhelming background generated by these high-energy electrons. Recently, a unique background-free method for measuring EC branching ratios was proposed using the TITAN ion trap at the TRIUMF ISAC (Isotope Separator and ACcelerator) radioactive beam facility. The measurements will make use of the EBIT (Electron Beam Ion Trap) operating in Penning mode where electrons from the β−-decay will be confined by the magnetic field. K-shell X-rays from EC will be detected by seven X-ray detectors located around the trap, thus providing orders of magnitude background suppression and thus ideal low-BR measurement environment.

Electric-dipole transitions between nearly degenerate, opposite parity levels of atomic dysprosium (Dy) were monitored overan eight-month period to search for a variation in thefine-structure constant, α. The frequencies of thesetransitions are sensitive to variation of α due to largerelativistic corrections of opposite sign for the opposite-paritylevels. In this unique system, in contrast to atomic-clockcomparisons, the difference of the electronic energies of theopposite-parity levels can be monitored directly utilizing aradio-frequency (rf), electric-dipole transition between them. Ourmeasurements for the frequency variation of the 3.1-MHz transitionin 163Dy and the 235-MHz transition in 162Dy can beanalyzed for both a temporal variation and a gravitational-potentialdependence of α since, during the data acquisition period, the Earth is located at different values of the gravitationalpotential of the Sun. The data provide a rate of fractional temporalvariation of α of (-2.7±2.6)×10-15 yr-1 ora value of (-8.7 ±6.6) ×10-6 for kα, thelinear-variation coefficient for α in a changinggravitational potential. These results are independent ofassumptions regarding variation of other fundamental constants. Thelatter result can be combined with other experimental constraints toextract the first limits on ke and kq, which characterize thevariation of me/mp and mq/mp in a changing gravitationalpotential, where me, mp, and mq are electron, proton, andquark masses. All results indicate the absence of significantvariation at the present level of sensitivity.

The radiative lifetime and mass isotope shift of the 1s22s22p 2P3/2 - 2P1/2 M1 transition in Ar13+ ions have been determined with high accuracies using the Heidelberg electron beam ion trap. This fundamentally relativistic transition provides unique possibilities for performing precise studies of correlation and quantum electrodynamic effects in many-electron systems. The lifetime corresponding to the transition has been measured with an accuracy of the order of one per thousand. Theoretical calculations predict a lifetime that is in significant disagreement with this high-precision experimental value. Our mass shift calculations, based on a fully relativistic formulation of the nuclear recoil operator, are in excellent agreement with the experimental results and confirm the absolute necessity to include relativistic recoil corrections when evaluating mass shift contributions even in medium-Z ions.

The precision of atomic mass measurements in a Penning trap is directly proportional to the charge state q of the ion and, hence, can be increased by using highly charged ions (HCl). For this reason, charge breeding with an electron beam ion trap (EBIT) is employed at TRIUMFs Ion Trap for Atomic and Nuclear science (TITAN) on-line facility in Vancouver, Canada. By bombarding the injected and trapped singly charged ions with an intense beam of electrons, the charge state of the ions is rapidly increased inside the EBIT. To be compatible with the online requirements of short-lived isotopes, very high electron beam current densities are needed. The TITAN EBIT includes a 6 Tesla superconducting magnet and is designed to have electron beam currents and energies of up to 5 A and 60 keV, respectively. Once operational at full capacity, most species can be bred into a He-like configuration within tens of ms. Subsequently, the HCl are extracted, pass a Wien filter to reduce isobaric contamination, are cooled, and injected into a precision Penning trap for mass measurement. We will present the first results and current status of the TITAN EBIT, which has recently been moved to TRIUMF after assembly and commissioning at the Max-Planck-Institute (MPI) for Nuclear Physics in Heidelberg, Germany.

Few-electron ions, which can be produced and studied at rest in electron beam ion traps (EBITs) are very well suited for the study of nuclear size effects and QED in strong fields, but the various contributions are usually entangled. Therefore, combinations of experiments with ions in different charge states are required to separate those contributions. In order to achieve this, several spectroscopic techniques have been recently implemented at the Heidelberg EBIT, aiming at high resolution and accuracy. In the optical region the most accurate wavelengths ever reported for highly charged ions [Draganic et al., Phys. Rev. Lett. 91 (2003) 183001] have been obtained, the results being sensitive to isotopic shifts [Tupitsyn et al., Phys. Rev. A 68 (2003) 022511] at the 0.01 meV level. The forbidden transitions of B-like ArXIV and Be-like ArXV ions studied here are especially interesting, since the QED contributions are as large as 0.2%. Improved atomic structure calculations allow to determine their values with growing accuracy, although the theoretical accuracy still lags three to four orders of magnitude behind the experimental one. In a different experiment, the lifetime of the corresponding metastable level has also been measured with an uncertainty of less than 0.2% thus becoming sensitive to the influence of the bound electron anomalous magnetic moment, an almost experimentally unexplored QED effect so far. A new laser spectroscopic setup aims at facilitating future studies of the hyperfine structure of heavy hydrogenic ions. Through the study of the dielectronic recombination, information on rare processes, such as two-electron-one-photon transitions in Ar16+ [Zou et al., Phys. Rev. A 67 (2003) 42703] at energies of around 2 keV, or the interference effects between dielectronic and radiative recombination in Hg77+ at 50 keV, and accurate values for the excitation energies of very heavy HCI have been obtained. A novel X-ray crystal spectrometer allowing absolute X-ray wavelength measurements in the range up to 15 keV with very high precision and reproducibility is currently used to study the Lyman series of H-like ions of medium-Z ions and the 2s-2p transitions of very heavy Li-like ions. (c) 2005 Elsevier B.V. All rights reserved. 12th International Conference on the Physics of Highly Charged Ions, Sep 06-11, 2004, Vilnius, Lithuania

ReA is a reaccelerator of rare-isotope beams at the National Superconducting Cyclotron Laboratory (NSCL). The rare isotopes are produced by fast projectile fragmentation. After production, they are separated in-flight and thermalized in a He gas “catcher” cell before being sent to ReA for reacceleration to a few MeV/u. One of its main components is an electron-beam ion trap (EBIT) employed to convert injected singly charged ions to highly charged ions prior to injection into linear-accelerator structures. The ReA EBIT features a high-current electron gun, a long trap structure, and a two-field superconducting magnet to provide both the high electron-beam current density needed for fast charge breeding and high capture probability of injected beams. This paper presents recent commissioning results. In particular, 39 K + ions have been injected, charge bred to 39 K 16 + and extracted for reacceleration up to 60 MeV. First charge-breeding results of beams injected from a commissioning Rb ion source in the NSCL’s beam “stopping” vault are also presented.

Two years after the relocation of the Heidelberg EBIT, several experiments are already in operation. Spectroscopic measurements in the optical region have delivered the most precise reported wavelengths for highly charged ions, in the case of the forbidden transitions of Ar XIV and Ar XV. The lifetimes of the metastable levels involved in those transitions has been determined with an error of less than 0.2%. A new, fully automatized x-ray crystal spectrometer allows systematic measurements with very high precision and reproducibility. Absolute measurements of the Lyman series of H-like ions are currently underway. Dielectronic recombination studies have yielded information on rare processes, as two-electron-one photon transitions in Ar16+, or the interference effects between dielectronic and radiative recombination in Hg77+. The apparatus can now operate at electron beam currents of more than 500 mA, and energies up to 100 keV. A further beam energy increase is planned in the near future. Ions can be extracted from the trap and transported to external experiments. Up to 4 × 107 Ar16+ ions per second can be delivered to a 1 cm diameter target at 10 m distance. Charge-exchange experiments with U64+ colliding with a cold He atomic beam have been carried out, as well as experiments aiming at the optimization of the charge state distribution of the extracted via dielectronic recombination. Two new EBITs, currently in advanced state of construction in Heidelberg, will be used for experiments at the VUV free electron laser at TESLA (Hamburg) and for the charge breeding of short-lived radioactive isotopes at the TRIUMF ISAC facility.

The Electron Beam Ion Trap (EBIT) in NSCL's reaccelerator ReA uses continuous ion injection and accumulation. In order to maximize capture efficiency and minimize breeding time into high charge states, the EBIT requires a high-current/high current-density electron beam. A new electron gun insert based on a concave Ba-dispenser cathode has been designed and built to increase the current transmitted through the EBIT's superconducting magnet. With the new insert, stable EBIT operating conditions with 0.8 A of electron beam have been established. The design of the electron gun is presented together with calculated and measured perveance data. In order to assess the experimental compression of the electron beam, a pinhole CCD camera has been set up to measure the electron beam radius. The camera observes X-rays emitted from highly charged ions, excited by the electron beam. Initial tests with this camera setup will be presented. They indicate that a current density of 640 A/cm(2) has been reached when the EBIT magnet was operated at 4 T.

The Electron Beam Ion Trap (EBIT) of the National Superconducting Cyclotron Laboratory at Michigan State University is used as a charge booster and injector for the currently commissioned rare isotope re-accelerator facility ReA. This EBIT charge breeder is equipped with a unique superconducting magnet configuration, a combination of a solenoid and a pair of Helmholtz coils, allowing for a direct observation of the ion cloud while maintaining the advantages of a long ion trapping region. The current density of its electron beam is a key factor for efficient capture and fast charge breeding of continuously injected, short-lived isotope beams. It depends on the radius of the magnetically compressed electron beam. This radius is measured by imaging the highly charged ion cloud trapped within the electron beam with a pinhole camera, which is sensitive to X-rays emitted by the ions with photon energies between 2 keV and 10 keV. The 80%-radius of a cylindrical 800 mA electron beam with an energy of 15 keV is determined to be r80%= (212±19)μm in a 4 T magnetic field. From this, a current density of j = (454 ± 83)A/cm2 is derived. These results are in good agreement with electron beam trajectory simulations performed with TriComp and serve as a test for future electron gun design developments. © 2014 AIP Publishing LLC.

A new technique has been developed at TRIUMF's TITAN facility to perform in-trap decay spectroscopy. The aim of this technique is to eventually measure weak electron capture branching ratios (ECBRs) and by this to consequently determine GT matrix elements of $\beta\beta$ decaying nuclei. These branching ratios provide important input to the theoretical description of these decays. The feasibility and power of the technique is demonstrated by measuring the ECBR of $^{124}$Cs., Comment: 9 pages, 9 figures

ReA is a post-accelerator at the National Superconducting Cyclotron Laboratory at Michigan State University. ReA is designed to reaccelerate rare isotopes to energies of a few MeV/u following production by projectile fragmentation and thermalization in a gas cell. The facility consists of four main components: an electron-beam ion trap (EBIT) charge breeder, an achromatic charge-over-mass (Q/A) separator, a radio-frequency quadrupole accelerator, and a superconducting radio-frequency linear accelerator. The EBIT charge breeder was specifically designed to efficiently capture continuous beams of singly charged ions injected at low energy (

TRIUMF's Ion Trap for Atomic and Nuclear science (TITAN) constitutes the only high precision mass measurement setup coupled to a rare isotope facility capable of increasing the charge state of short-lived nuclides prior to the actual mass determination in a Penning trap. Recent developments around TITAN's charge breeder, the electron beam ion trap, form the basis for several successful experiments on radioactive isotopes with half-lives as low as 65 ms and in charge states as high as 22+.

Electron beam ion traps (EBITs) are a new tool for charge breeding of rare isotope beams. The ionization efficiency of a new high current EBIT recently built at the MPIK was investigated spectroscopically during its commissioning phase.

We present Penning-trap mass measurements of neutron-rich ${}^{44,47\ensuremath{-}50}$K and ${}^{49,50}$Ca isotopes carried out at the TITAN facility at TRIUMF-ISAC. The ${}^{44}$K mass measurement was performed with a charge-bred 4$+$ ion utilizing the TITAN electron beam ion trap and agrees with the literature. The mass excesses obtained for ${}^{47}$K and ${}^{49,50}$Ca are more precise and agree with the values published in the 2003 Atomic Mass Evaluation (AME'03). The ${}^{48,49,50}$K mass excesses are more precise than the AME'03 values by more than 1 order of magnitude. For ${}^{48,49}$K, we find deviations of 7$\ensuremath{\sigma}$ and 10$\ensuremath{\sigma}$, respectively. The new ${}^{49}$K mass excess lowers significantly the two-neutron separation energy at the neutron number $N=30$ compared with the separation energy calculated from the AME'03 mass-excess values and thus increases the $N=28$ neutron-shell gap energy at $Z=19$ by approximately 1 MeV.

We present a description of the Radio Frequency Quadrupole (RFQ) ion trap built as part of the TITAN facility. It consists of a gas-filled, segmented, linear Paul trap and is the first stage of the TITAN setup with the purpose of cooling and bunching radioactive ion beams delivered from ISAC-TRIUMF. This is the first such device to be driven digitally, i.e., using a high voltage ($V_{pp} = \rm{400 \, V}$), wide bandwidth ($0.2 < f < 1.2 \, \rm{MHz}$) square-wave as compared to the typical sinusoidal wave form. Results from the commissioning of the device as well as systematic studies with stable and radioactive ions are presented including efficiency measurements with stable $^{133}$Cs and radioactive $^{124, 126}$Cs. A novel and unique mode of operation of this device is also demonstrated where the cooled ion bunches are extracted in reverse mode, i.e., in the same direction as previously injected., 34 pages, 17 figures

The first direct mass measurement of $^{6}\mathrm{He}$ has been performed with the TITAN Penning trap mass spectrometer at the ISAC facility. In addition, the mass of $^{8}\mathrm{He}$ was determined with improved precision over our previous measurement. The obtained masses are $m(^{6}\mathrm{He})=6.018\text{ }885\text{ }883(57)\text{ }\text{ }\mathrm{u}$ and $m(^{8}\mathrm{He})=8.033\text{ }934\text{ }44(11)\text{ }\text{ }\mathrm{u}$. The $^{6}\mathrm{He}$ value shows a deviation from the literature of $4\ensuremath{\sigma}$. With these new mass values and the previously measured atomic isotope shifts we obtain charge radii of 2.060(8) and 1.959(16) fm for $^{6}\mathrm{He}$ and $^{8}\mathrm{He}$, respectively. We present a detailed comparison to nuclear theory for $^{6}\mathrm{He}$, including new hyperspherical harmonics results. A correlation plot of the point-proton radius with the two-neutron separation energy demonstrates clearly the importance of three-nucleon forces.

Recent high-precision mass measurements of $^{9}$Li and $^{9}$Be, performed with the TITAN Penning trap at the TRIUMF ISAC facility, are analyzed in light of state-of-the-art shell model calculations. We find an explanation for the anomalous Isobaric Mass Multiplet Equation (IMME) behaviour for the two $A$ = 9 quartets. The presence of a cubic $d$ = 6.3(17) keV term for the $J^{\pi}$ = 3/2$^{-}$ quartet and the vanishing cubic term for the excited $J^{\pi}$ = 1/2$^{-}$ multiplet depend upon the presence of a nearby $T$ = 1/2 state in $^{9}$B and $^{9}$Be that induces isospin mixing. This is contrary to previous hypotheses involving purely Coulomb and charge-dependent effects. $T$ = 1/2 states have been observed near the calculated energy, above the $T$ = 3/2 state. However an experimental confirmation of their $J^{\pi}$ is needed., Comment: 5 pages, 2 figures

Penning trap mass measurements of short-lived nuclides have been performed for the first time with highly-charged ions (HCI), using the TITAN facility at TRIUMF. Compared to singly-charged ions, this provides an improvement in experimental precision that scales with the charge state q. Neutron-deficient Rb-isotopes have been charge bred in an electron beam ion trap to q = 8 - 12+ prior to injection into the Penning trap. In combination with the Ramsey excitation scheme, this unique setup creating low energy, highly-charged ions at a radioactive beam facility opens the door to unrivalled precision with gains of 1-2 orders of magnitude. The method is particularly suited for short-lived nuclides such as the superallowed {\beta} emitter 74Rb (T1/2 = 65 ms). The determination of its atomic mass and an improved QEC-value are presented., Comment: 5 pages, 3 figures

International audience; Precise atomic mass determinations play a key role in various fields of physics, including nuclear physics, testing of fundamental symmetries and constants and atomic physics. Recently, the TITAN Penning trap measured the masses of several neutron halos. These exotic systems have an extended, diluted, matter distribution that can be modelled by considering a nuclear core surrounded by a halo formed by one or more of loosely bound neutrons. Combined with laser spectroscopy measurements of isotopic shifts precise masses can be used to obtain reliable charge radii and two-neutron-seperation energies for these halo nuclei. It is shown that these results can be used as stringent tests of nuclear models and potentials providing an important metric for our understanding of the interactions in all nuclei.

TITAN (TRIUMF's Ion Traps for Atomic and Nuclear science) is an online facility designed to carry out high-precision mass measurements on singly and highly charged radioactive ions. The TITAN Penning trap has been built and optimized in order to perform such measurements with an accuracy in the sub ppb-range. A detailed characterization of the TITAN Penning trap is presented and a new compensation method is derived and demonstrated, verifying the performance in the range of sub-ppb., 33 pages, 16 figures

International audience; Knowledge of 2νββ nuclear matrix elements is essential to probe the theoretical framework of 0νββ decays. At TITAN, TRIUMF's Ion Trap for Atomic and Nuclear science, a novel technique has been developed to measure electron capture branches of virtual intermediate nuclei in ββ decays.During two experiments with radioactive 124,126Cs isotopes the feasibility of this new method was proven.

At TRIUMF's ion trap for atomic and nuclear science (TITAN) a new experimental technique is being developed to measure electron-capture branching ratios of intermediate nuclei in double-β decays. The key feature of this novel technique is the use of an open access Penning trap. Radioactive ions are stored inside the trap while their decays are observed. X-rays following an electron capture are detected by x-ray detectors radially installed around the trap. Electrons originating from β-decays are guided out of the trap by the Penning trap's strong magnetic field where they are then detected by a Si-detector. Detailed simulations have been performed to determine the size and characterize the efficiency of this detector. During a beam time with radioactive 107In this β-detector has been used and for the first time an electron capture branching ratio has been determined with this novel technique of in-trap decay spectroscopy.

TRIUMF's Ion Trap for Atomic and Nuclear science (TITAN) is a multi-ion trap facility with the goal of high precision mass measurements of radio-nuclides. TITAN is coupled to the ISAC on-line facility at TRIUMF, Vancouver, Canada, and consists of a Radio-Frequency Quadrupole (RFQ) buncher and cooler, an Electron Beam Ion Trap (EBIT), a Cooler Penning Trap (CPET), presently under construction and installation planned for 2011, and the Measurement Penning Trap (MPET). To date the TITAN EBIT has been used for charge breeding of stable and radioactive isotopes. In this paper we report the successful injection and extraction of stable Na and radioactive 25Na. Preliminary emittance measurements have been completed and the emittance in the vertical direction was found to be epsilon εrmsY = 15.7±0.5πmm-mrad at a beam energy of 1.95 keV.

Nuclear ground state properties including mass, charge radii, spins and moments can be determined by applying atomic physics techniques such as Penning-trap based mass spectrometry and laser spectroscopy. The MATS and LaSpec setups at the low-energy beamline at FAIR will allow us to extend the knowledge of these properties further into the region far from stability. The mass and its inherent connection with the nuclear binding energy is a fundamental property of a nuclide, a unique “fingerprint”. Thus, precise mass values are important for a variety of applications, ranging from nuclear-structure studies like the investigation of shell closures and the onset of deformation, tests of nuclear mass models and mass formulas, to tests of the weak interaction and of the Standard Model. The required relative accuracy ranges from 10−5 to below 10−8 for radionuclides, which most often have half-lives well below 1 s. Substantial progress in Penning trap mass spectrometry has made this method a prime choice for precision measurements on rare isotopes. The technique has the potential to provide high accuracy and sensitivity even for very short-lived nuclides. Furthermore, ion traps can be used for precision decay studies and offer advantages over existing methods. With MATS (Precision Measurements of very short-lived nuclei using an A_dvanced Trapping System for highly-charged ions) at FAIR we aim to apply several techniques to very short-lived radionuclides: High-accuracy mass measurements, in-trap conversion electron and alpha spectroscopy, and trap-assisted spectroscopy. The experimental setup of MATS is a unique combination of an electron beam ion trap for charge breeding, ion traps for beam preparation, and a high-precision Penning trap system for mass measurements and decay studies. For the mass measurements, MATS offers both a high accuracy and a high sensitivity. A relative mass uncertainty of 10−9 can be reached by employing highly-charged ions and a non-destructive Fourier-Transform Ion-Cyclotron-Resonance (FT-ICR) detection technique on single stored ions. This accuracy limit is important for fundamental interaction tests, but also allows for the study of the fine structure of the nuclear mass surface with unprecedented accuracy, whenever required. The use of the FT-ICR technique provides true single ion sensitivity. This is essential to access isotopes that are produced with minimum rates which are very often the most interesting ones. Instead of pushing for highest accuracy, the high charge state of the ions can also be used to reduce the storage time of the ions, hence making measurements on even shorter-lived isotopes possible. Decay studies in ion traps will become possible with MATS. Novel spectroscopic tools for in-trap high-resolution conversion-electron and charged-particle spectroscopy from carrier-free sources will be developed, aiming e.g. at the measurements of quadrupole moments and E0 strengths. With the possibility of both high-accuracy mass measurements of the shortest-lived isotopes and decay studies, the high sensitivity and accuracy potential of MATS is ideally suited for the study of very exotic nuclides that will only be produced at the FAIR facility.Laser spectroscopy of radioactive isotopes and isomers is an efficient and model-independent approach for the determination of nuclear ground and isomeric state properties. Hyperfine structures and isotope shifts in electronic transitions exhibit readily accessible information on the nuclear spin, magnetic dipole and electric quadrupole moments as well as root-mean-square charge radii. The dependencies of the hyperfine splitting and isotope shift on the nuclear moments and mean square nuclear charge radii are well known and the theoretical framework for the extraction of nuclear parameters is well established. These extracted parameters provide fundamental information on the structure of nuclei at the limits of stability. Vital information on both bulk and valence nuclear properties are derived and an exceptional sensitivity to changes in nuclear deformation is achieved. Laser spectroscopy provides the only mechanism for such studies in exotic systems and uniquely facilitates these studies in a model-independent manner.The accuracy of laser-spectroscopic-determined nuclear properties is very high. Requirements concerning production rates are moderate; collinear spectroscopy has been performed with production rates as few as 100 ions per second and laser-desorption resonance ionization mass spectroscopy (combined with β-delayed neutron detection) has been achieved with rates of only a few atoms per second.This Technical Design Report describes a new Penning trap mass spectrometry setup as well as a number of complementary experimental devices for laser spectroscopy, which will provide a complete system with respect to the physics and isotopes that can be studied. Since MATS and LaSpec require high-quality low-energy beams, the two collaborations have a common beamline to stop the radioactive beam of in-flight produced isotopes and prepare them in a suitable way for transfer to the MATS and LaSpec setups, respectively., This manuscript has been acomplished by the contributions from several members of the MATS and LaSpec collaborations. All the contributions are acknowledged and without them this document would not exist. We also acknowledge support from the Max-Planck Society as well as from several funding agencies in Spain which provided economical support for the organization of the 3rd LaSpec-MATS collaboration meeting held in Matalascañas (Huelva) in October 2008. This meeting served to fix the TDR contents. These funding agencies are Junta de Andalucía and CPAN (Centro Nacional de Partículas Astropartículas y Nuclear).

We report the mass measurement of the short-lived $^{12}\mathrm{Be}$ nuclide (${T}_{1/2}=21.5$ ms) performed using the Penning trap mass spectrometer TITAN at TRIUMF. Our mass excess value of $25 078.0(2.1)$ keV is in agreement with previous measurements, but is a factor of 7 more precise than the Atomic Mass Evaluation of 2003. To address an unresolved discussion on the spin assignment of isospin $T=2$ states in $^{12}\mathrm{C}$ and $^{12}\mathrm{O}$, we reevaluate the isobaric mass multiplet equation for the lowest lying $T=2$ multiplet in the $A=12$ system and use the extracted parameters to extrapolate from the known excited ${2}^{+}$ and ${0}^{+}$ states in $^{12}\mathrm{Be}$. Though this analysis favors the second known $T=2$ state in $^{12}\mathrm{C}$ to be ${2}^{+}$, ${0}^{+}$ cannot be excluded.

Experiments with reaccelerated beams are an essential component of the science program of existing and future rare isotope beam facilities. NSCL is currently constructing ReA3, a reaccelerator for rare isotopes that have been produced by projectile fragmentation and in-flight fission and that have been thermalized in a gas stopper. The resulting low-energy beam will be brought to an Electron Beam Ion Source/Trap (EBIS/T) in order to obtain highly charged ions at an energy of 12 keV/u. This charge breeder is followed by a compact linear accelerator with a maximum beam energy of 3 MeV/u for 238U and higher energies for lighter isotopes. Next-generation rare isotope beam facilities like the Facility for Rare Isotope Beams FRIB, but also existing Isotope Separator On-line (ISOL) facilities are expected to provide rare-isotope beam rates in the order of 1011 particles per second for reacceleration. At present the most promising scheme to efficiently start the reacceleration of these intense beams is the use of a next-generation high-current charge-breeder based on an EBIS/T. MSU has formed a collaboration to develop an EBIT for this purpose. A new high-current EBIS/T breeder will be developed and constructed at MSU, where also first tests on achievable beam rate capability will be performed. The EBIT is planned to be installed at the Isotope Separator and Accelerator facility ISAC at TRIUMF laboratory for on-line tests with rare isotope beams and to provide intense energetic reaccelerated radioactive beams. The status of the ReA3-EBIS/T in the NSCL reaccelerator project is given with a brief summary of results, followed by a discussion of plans for the future high-intensity EBIS/T charge breeder.

The frequency ratio of {sup 6}Li to {sup 7}Li was measured using the TITAN Penning trap mass spectrometer. This measurement resolves a 16-ppb discrepancy between the {sup 6}Li mass of 6.015 122 795(16) u from the Atomic Mass Evaluation 2003 (AME03), which is based on a measurement by JILATRAP, and the more recent measurement of 6.015 122 890(40) u by SMILETRAP. Our measurement agrees with SMILETRAP and a more precise mass value for {sup 6}Li of 6.015 122 889(26) u is presented along with systematic evaluations of the measurement uncertainties. This result makes {sup 6}Li a solid anchor point for future mass measurements on highly charged ions with m/q{approx}6.

Radio-frequency electric-dipole transitions between nearly degenerate, opposite parity levels of atomic dysprosium (Dy) were monitored over an eight-month period to search for a variation in the fine-structure constant, $\alpha$. The data provide a rate of fractional temporal variation of $\alpha$ of $(-2.4\pm2.3)\times10^{-15}$ yr$^{-1}$ or a value of $(-7.8 \pm 5.9) \times 10^{-6}$ for $k_\alpha$, the variation coefficient for $\alpha$ in a changing gravitational potential. All results indicate the absence of significant variation at the present level of sensitivity. We also present initial results on laser cooling of an atomic beam of dysprosium., Comment: 10 pages, 6 figures, fixed typos in section 5, updated results

Penning trap mass measurements of 9 Be, 10 Be ( t 1 / 2 = 1.51 My ), and the one-neutron halo nuclide 11 Be ( t 1 / 2 = 13.8 s ) have been performed using TITAN at TRIUMF. The resulting 11 Be mass excess ( ME = 20 177.60 ( 58 ) keV ) is in agreement with the current Atomic Mass Evaluation (AME03) [G. Audi, et al., Nucl. Phys. A 729 (2003) 337] value, but is over an order of magnitude more precise. The precision of the mass values of 9,10 Be have been improved by about a factor of four and reveal a ≈ 2 σ deviation from the AME mass values. Results of new atomic physics calculations are presented for the isotope shift of 11 Be relative to 9 Be, and it is shown that the new mass values essentially remove atomic mass uncertainties as a contributing factor in determining the relative nuclear charge radius from the isotope shift. The new mass values of 10,11 Be also allow for a more precise determination of the single-neutron binding energy of the halo neutron in 11 Be.

A high-precision Penning trap mass measurement of the exotic $^{8}\mathrm{He}$ nuclide (${T}_{1/2}=119\text{ }\text{ }\mathrm{ms}$) has been carried out resulting in a reduction of the uncertainty of the halo binding energy by over an order of magnitude. The new mass, determined with a relative uncertainty of $9.2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8}$ ($\ensuremath{\delta}m=690\text{ }\text{ }\mathrm{eV}$) is 13 keV less bound than the previously accepted value. The mass measurement is of great relevance for the recent charge-radius measurement of $^{8}\mathrm{He}$ [P. Mueller et al., Phys. Rev. Lett. 99, 252501 (2007).]. The $^{8}\mathrm{He}$ mass is the first result from the newly-commissioned Penning trap: TITAN (TRIUMF's Ion Trap for Atomic and Nuclear science) at the ISAC (Isotope Separator and Accelerator) radioactive beam facility at TRIUMF.

A compact flat-field soft x-ray grazing-incidence grating spectrometer equipped with a cryogenically cooled back-illuminated charge-coupled device camera was built and implemented at the Heidelberg Electron Beam Ion Trap. The instrument spans the spectral region from 1 to 37 nm using two different gratings. In slitless operation mode, it directly images a radiation source, in this case ions confined in an electron beam ion trap, with high efficiency and reaching hereby a resolving power of lambda/Deltalambda approximately =130 at 2 nm and of lambda/Deltalambda approximately =600 at 28 nm. Capable of automatized operation, its low noise and excellent stability make it an ideal instrument not only for spectroscopic diagnostics requiring wide spectral coverage but also for precision wavelength measurements.

The Zeeman line components of the magnetic-dipole (M1) 1s{sup 2}2s{sup 2}2p {sup 2}P{sub 1/2}-{sup 2}P{sub 3/2} transition in boronlike Ar{sup 13+} were experimentally resolved by high-precision emission spectroscopy using the Heidelberg electron beam ion trap. We determined the gyromagnetic (g) factors of the ground and first-excited levels to be g{sub 1/2}=0.663(7) and g{sub 3/2}=1.333(2), respectively. This corresponds to a measurement of the g factor of a relativistic electron in a bound non-S state of a multielectron ion with a 1.5 parts-per-thousand accuracy. The results are compared to theoretical calculations by means of the configuration interaction Dirac-Fock-Sturmian method including electron correlation effects and additional quantum electrodynamic corrections. Our measurements show that the classical Lande g factor formula is sufficiently accurate to the present level of accuracy in few-electron ions of medium nuclear charge number Z.

Radio-frequency E1 transitions between nearly degenerate, opposite parity levels of atomic dysprosium were monitored over an eight month period to search for a variation in the fine-structure constant. During this time period, data were taken at different points in the gravitational potential of the Sun. The data are fitted to the variation in the gravitational potential yielding a value of $(-8.7 \pm 6.6) \times 10^{-6}$ for the fit parameter $k_\alpha$. This value gives the current best laboratory limit. In addition, our value of $k_{\alpha}$ combined with other experimental constraints is used to extract the first limits on k_e and k_q. These coefficients characterize the variation of m_e/m_p and m_q/m_p in a changing gravitational potential, where m_e, m_p, and m_q are electron, proton, and quark masses. The results are $k_e = (4.9 \pm 3.9) \times 10^{-5}$ and $k_q = (6.6 \pm 5.2) \times 10^{-5}$., Comment: 6 pages, 3 figures