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This study presents the investigation of magnetic dipole transition lines of W13+ ions in the wavelength range of 200–700 nm at a low-energy electron beam ion trap. Seventeen lines emitted from W13+ ions have been observed with three being reported experimentally for the first time. The atomic structure calculation and spectra simulation of W13+ ions have been carried out using the multiconfiguration Dirac–Hartree–Fock method combined with the relativistic configuration interaction approach and the collisional–radiative model, respectively. The theoretical calculations are in reasonable agreement with the experimental observations, and most of the observed lines have been identified. [ABSTRACT FROM AUTHOR]

The X-ray spectra of L-shell transitions in Neon-like Xenon ion (Xe44+) have been precisely measured at the Shanghai Electron-Beam Ion Trap using a high-resolution crystal spectrometer. Focusing on the line-intensity ratio of the 3F {2p6-(2p51/23s1/2)J=1} and 3D {2p6-(2p53/23d5/2)J=1} lines (3F/3D), our measurements have achieved remarkable precision improvements over the previous studies. These spectra have been simulated using the collisional-radiative model (CRM) within the Flexible Atomic Code, showing good agreement with the measurements. The previously reported discrepancies, approximately ranging from 10% to 20%, have been significantly reduced in this work to below 1.4% for electron-beam energies exceeding 6 keV and to around 7% for lower energies. Furthermore, our analysis of population fluxes of the involved levels reveals a very high sensitivity of the 3F line to radiation cascades. This suggests that the current CRM, which conventionally excludes interionic population transfer processes, may underestimate the population of the upper level of the 3F line and the cascade-related higher levels, thus explaining the remaining discrepancies. These findings provide a solid foundation for further minimizing these discrepancies and are crucial for understanding the atomic structure and plasma model of these ions. [ABSTRACT FROM AUTHOR]

Spectral lines of the magnetic-dipole transition between the 3 d 2 D 3 / 2 , 5 / 2 levels of K-like Kr17+, Zr21+, Nb22+, Mo23+, and Ru25+ ions were measured in a compact electron beam ion trap. By means of dedicated calibration methods, the transition wavelengths of Kr17+, Zr21+, and Mo23+ ions reduce uncertainties by at least one order of magnitude and the wavelengths of Nb22+ and Ru25+ ions are measured for the first time at a few ppm level. In addition, the fine-structure energy splittings were systematically calculated using the multiconfiguration Dirac–Hartree–Fock method combined with the relativistic configuration interaction approach. The contributions of the core-valence and core-core electron correlations, the Breit interaction and QED effect were discussed in detail. The results show that it is essential to include deep core-valence correlation of L -shell and core-core valence correlation of 3 p subshell to obtain an agreement better than 0.15% with existing experimental values. The calculation model can be performed to predict the wavelength within a high accuracy for a wide range of potassium-like ions. [ABSTRACT FROM AUTHOR]

This work reported the investigation of optical spectra of Rh-like Xe9+ and Ru-like Xe10+ ions at a low-energy electron beam ion trap. The line from 4d92D3/2–2D5/2 M1 transition of Xe9+ ions was remeasured, the wavelength of which was determined to be 598.365(5) nm, and the uncertainty was significantly improved. In the region of 200–700 nm, four spectral lines emitted from Xe10+ ions were directly observed for the first time. The relativistic many-body perturbation method was adopted for the investigation of fine structure in Xe10+ ions. The theoretical and experimental results were in good agreement within 2%, and the four observed lines of Xe10+ ions were identified. [ABSTRACT FROM AUTHOR]

Measurements of the L-shell X-ray emission of fluorine-like europium ions (Eu54+) were made under controlled laboratory conditions on the EBIT-I electron beam ion trap at Livermore using an X-ray calorimeter, extending such measurements to the middle of the rare earth elements. Comparing the calorimeter spectra with atomic data from the flexible atomic code, we have identified and analyzed several prominent n = 3 → n = 2 transitions, including one two-electron, one-photon core changing transition and one electric quadrupole transition. We find that the measured energies are typically up to several eV higher than predicted. [ABSTRACT FROM AUTHOR]

We report measurements of hypersatellite radiation of argon ions in the electron energy region of 5200 eV to 7500 eV. Here, we observed a strong enhancement of this hypersatellite  K α h  production. Trielectronic recombination (TR) is discussed as a possible channel for  K α h  production leading to this enhancement where main TR resonances are expected to occur. Data analysis was mainly based on the extracted intensity ratio of hypersatellite  K α h  to  K α  lines ( K α h / K α ). In addition, the collisional excitation and the collisional ionisation of the K-shell ions were modeled as main background processes of the K α  X-ray production. The  K α h / K α  intensity ratio shows a significant rise around 6500 eV electron energy by a factor of about two above the background level. This observation is compared with calculations of the expected electron energies for the resonant  K α h  emission due to the KK TR process. The observed rise as a function of the electron collision energy, which occurs in the vicinity of the predicted TR resonances, is significantly stronger and energetically much wider than the results of theoretical calculations for the TR process. However, the experimental evidence of this process is not definitive. [ABSTRACT FROM AUTHOR]

In an effort to measure electron-impact ionization (EII) cross-sections of He-like F e 24 + at the electron beam ion trap (EBIT) facility of the National Institute of Standards and Technology (NIST), we have experimentally determined the corrections to the nominal beam energy determined by the voltages applied to the EBIT. High-resolution X-ray spectra were recorded at nominal electron beam energies between 6660 eV and 6750 eV using X-ray microcalorimetry based upon an array of 192 transition-edge sensors (TES). A large-scale collisional-radiative simulation of the non-Maxwellian EBIT plasma using relevant atomic data calculated with Flexible Atomic Code allowed us to determine the space-charge correction due to the electron beam including the neutralization factor by the ion cloud of the EBIT. [ABSTRACT FROM AUTHOR]

In this work, we report a spectroscopy measurement of Ru 21 + to Ru 24 + ions in the optical region using a low energy electron beam ion trap. Twelve lines were observed. The multiconfiguration Dirac–Hartree–Fock and relativistic configuration interaction methods were used to calculate the atomic level energies and the transition rates. With the assistance of the theoretical results, eleven magnetic dipole lines were identified. The experimental results provide new reference data for further theoretical investigations of the complex ions. [ABSTRACT FROM AUTHOR]

Wavelength calibration in diffraction spectroscopy typically depends on identifying strong, well-known lines in the recorded spectra and fitting a calibration function to them. In this paper, we outline a novel method (order penalization) for improving spectroscopic calibrations by extending non-linear least squares fitting of the calibration curve. The method introduces an extra term into the minimized quantity that penalizes disagreement in the positions of spectral lines observed in multiple diffraction orders. The primary advantage of this method is that the lines used do not have to be identified, except for establishing the fact that they are different orders of the same line. This increases the number of constraints on the calibration curve, potentially in spectral regions where no regular calibration lines are available. The mathematical basis of this method is described, and the performance of this method is evaluated on simulated data and experimental data from the National Institute of Standards and Technology (NIST) Electron Beam Ion Trap. We demonstrate the effectiveness of the method on the spectra of highly charged Ag-like Re 28 + and nearby charge state ions. • Calibration uncertainty can be reduced when lines are seen in multiple orders. • Monte Carlo simulations were used to profile the method's performance. • In experiments, the method has decreased calibration uncertainty by more than 66 %. [ABSTRACT FROM AUTHOR]

The 4s24p 2P3/2â€"2P1/2 magnetic dipole transition in Ga-like ions is interested in developing of high precise highly charged ion clock (Yu and Sahoo 2019 Phys. Rev. A 99 022513). In this work, we present direct observations of the transition in Mo11+ and Ru13+ ions at an electron beam ion trap. Internal and external calibration methods are used for determining the wavelength of the Mo11+ and Ru13+ lines, respectively. Both measurements reach precision levels of a few ppm. Compared with the available values, the current results significantly improve the experimental uncertainty. [ABSTRACT FROM AUTHOR]

This paper reports an experimental realization of a low-temperature quasi-Maxwell–Boltzmann plasma in an electron beam ion trap (EBIT) by employing a special energy sweep technique. A Maxwellian C IV plasma with electron temperatures in the range 10–40 eV is simulated in the Shanghai high-temperature superconducting EBIT (SH-HtscEBIT), which requires stable performance of the EBIT under the extreme condition of ultralow electron beam energy. The C IV spectra are obtained by an extreme ultraviolet spectrometer in the wavelength region 290–400 Å. The measured spectral line intensity ratios are compared with the results of calculations using a collisional-radiative model. The mean difference between the experimental and theoretical results in the simulated temperature region is about 14%. [ABSTRACT FROM AUTHOR]

Highly charged tungsten transitions can be used as a diagnostic tool for investigating performance of the fusion device. Systematic spectroscopic investigations of the radiative decay channels of the tungsten charge states allow for extending the fundamental understanding of highly charged ions and can serve as a diagnostic tool to improve applied plasma research. Electron beam ion traps (EBIT) offer the ability to generate emission from highly charged tungsten ions because of their charge state and excitation selectivity due to their quasi-monoenergetic electron beam. In this work, we report the current experimental capabilities of the EBIT at the National Institute of Standards and Technology (NIST). High-resolution measurements of EUV and x-ray transitions from tungsten charge states are shown, demonstrating our ability to produce and identify the spectral features of highly charged tungsten plasma. While the experimental results were limited by the lack of an absolute calibration of the spectrometer, we present approximate transition energies of two strong transitions from the Ti-like W 52+ and Sc-like W 53+ charge states. Our estimates agree quite well with the results of FAC simulations, where these strongest transitions were identified to originate from 3d-4f transitions. This decay channel has been shown to be the strongest transition for surrounding charge states. [ABSTRACT FROM AUTHOR]

We report a population kinetics study on line emissions of the Pm-like Bi 22+ performed by using a collisional-radiative (CR) model. Population rates of excited levels are analyzed to explain the population trapping in the 4 f 13 5 s 2 state which causes the loss of the 5 s − 5 p resonance lines in emission spectra. Based on the present analysis, we elucidate why the population trapping is not facilitated for a meta-stable excited level of the Sm-like Bi 21+ . The emission line spectra are calculated for the Pm-like isoelectronic sequence from Au 18+ through W 13+ and compared with experimental measurements by electron-beam-ion-traps (EBITs). Structures of the spectra are similar for all of the cases except for calculated W 13+ spectra. The calculated spectra are hardly reconciled with the measured W 13+ spectrum using the compact electron-beam-ion-trap (CoBIT) [Phys. Rev. A 92 (2015) 022510]. [ABSTRACT FROM AUTHOR]

We present a direct observation of the M1 transition between the fine structure splitting in the 4f135s25p6 2F ground term of W VIII. The spectroscopic data of few-times ionized tungsten ions are important for the future ITER diagnostics, but there is a serious lack of data. The present study is part of an ongoing effort to solve this problem. Emission from the tungsten ions produced and trapped in a compact electron beam ion trap is observed with a Czerny-Turner visible spectrometer. Spectra in the EUV range are also observed at the same time to help identify the previously-unreported visible lines. The observed wavelength 574.47±0.03 nm (air), which corresponds to the fine structure splitting of 17,402.5 ± 0.9 cm-1, shows reasonable agreement with the previously reported value 17,410 ± 5 cm-1 obtained indirectly through the analysis of EUV spectra [Ryabtsev et al., Atoms 3 (2015) 273]. [ABSTRACT FROM AUTHOR]

The spectroscopic investigation of optical spectra of Ca-like Br15+, Kr16+, Zr20+, and Rh25+ ions at an electron beam ion trap was presented. In the region of 200-700 nm, ten spectral lines emitted from these ions were identified, eight of which were reported for the first time. The multiconfiguration Dirac-Hartree-Fock and relativistic configuration interaction methods were employed in the calculations of energy levels and transition rates, in which the Breit interaction and QED effects were taken into account, and the contributions of core-valence and core-core correlations were found to be essential. The present results showed a good agreement between the theory and the experiment in general. For four lines, the discrepancies between the calculated and measured wavelengths were larger than 1.5%, and our accurate experimental results could be reference data for further calculations. • Optical lines of Ca-like Br15+, Kr16+, Zr20+, and Rh25+ ions are measured at a low-energy electron beam ion trap. • Ten spectral lines are identified and eight of them are reported for the first time. • The wavelengths and transition rates are calculated with the MCDHF combined with the RCI method. • The core-valence and core-core correlations are found to be essential. [ABSTRACT FROM AUTHOR]

• The 4 p 2 3 P 1 − 3 P 0 magnetic dipole clock transition in highly charged Rh13+ ions was firstly directly observed in an electron beam ion trap. • Using a dedicated internal calibration method, the line wavelength was determined at a few ppm precision level. The uncertainty was significantly improved by more than 350 time compared with the previous most precise indirect measurement. Magnetic dipole transitions between fine- or hyperfine-structure splitting in the n p 2 3 P ground term have been proposed to develop ultraprecise atomic clocks (https://link.aps.org/doi/10.1103/PhysRevLett.113.233003 Yudin e t a l. , Phys. Rev. Lett. 113 (2014) 233003). In the present work, a spectroscopic investigation of fine-structure splitting of 4 p 2 3 P 1 − 3 P 0 in Rh 13 + is performed in a compact electron beam ion trap. By means of a dedicated internal calibration method, the transition wavelength of 321.2150(14) nm (in air) is precisely determined at a few ppm level which agrees with the previous results and improves its uncertainty by more than 350 times. [ABSTRACT FROM AUTHOR]

Abstract: We present the charge state distributions of highly charged ions extracted from an electron beam ion trap (EBIT). The distributions were obtained in the two different extraction modes, pulsed mode and leaky mode. The number ratio between adjacent charge state ions, which is an important quantity to measure dielectronic recombination cross sections with an EBIT, is compared between the two extraction modes. The results are also compared with recent theoretical predictions by Zhang et al. [17]. [Copyright &y& Elsevier]

At the NSCL a reaccelerator with design end energy of 3 MeV/u for U, 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. [ABSTRACT FROM AUTHOR]

Abstract: 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. [Copyright &y& Elsevier]

Abstract: The paper describes a novel application of an electron beam ion trap as a plasma target facility for intense laser–plasma interaction studies. The low density plasma target (∼1013/cm3) is confined in a mobile cryogenic electromagnetic charged particle trap, with the magnetic confinement field of 1–3T maintained by a superconducting magnet. Ion plasmas for a large variety of ion species and charge states are produced and maintained within the magnetic field and the space-charge of an energetic electron beam in the “electron beam ion trap” (EBIT) geometry. Intense laser beams (optical lasers, X-ray lasers and upcoming “X-ray free electron lasers” (XFEL)) provide strong time varying electromagnetic fields (>1012 V/cm in femto- to nano-second pulses) for interactions with electromagnetically confined neutral/non-neutral plasmas. Experimental scenarios with intense photon fields on ionization/excitation processes, the ionization balance, as well as photon polarization effects and tests with intense lasers that utilize the ion plasma target are outlined. A first test of the plasma target with the PHELIX high intensity laser at GSI is described. [Copyright &y& Elsevier]

Abstract: While more than a decade of work has provided glimpses into the physics of highly charged ion (HCI) neutralization on surfaces, two prominent objectives remain unfulfilled: (1) a unified, quantitative model for separating the kinetic energy response of a wide range of materials classes from the effects of HCIs’ potential energy effects and (2) insertion of HCI technology(s) as a cost-effective processing tool in a high-volume market sector. The National Institute of Standards and Technology (NIST) electron beam ion trap (EBIT) facility has recently incorporated tools for preparing clean, atomically flat surfaces of single crystals from gold to tungsten to silicon and for depositing and patterning thin films that range from high resistivity oxides to transition metals like cobalt and nickel. Current activities are focused on utilizing this unique capability to simultaneously address both of the objectives above by employing technologically important magnetic multi-layer systems to perform transport measurements that provide new insight into the fundamental processes that occur during HCI–surface neutralization. Specifically, we are producing Magnetic Tunnel Junctions (MTJs) critical to both magnetic devices and incorporating HCIs in the processing recipe to adjust critical electronic properties that are currently inhibiting their advancement. In return, the electrical response of the tunnel junction to the HCI processing provides a novel approach to performing ensemble measurements of HCI–surface interactions. By varying the construction of the tunnel junction, critical tests of the role of electron density, densities of states and electronic structure in the HCI–surface charge exchange can be performed. [Copyright &y& Elsevier]

Abstract: TITAN (TRIUMF''s Ion Trap for Atomic and Nuclear science) is a system of multiple ion traps installed at the radioactive ion beam facility ISAC. The uniqueness of the system lies in the combination of different kinds of ion traps nowhere else available, and the coupling of this system to ISAC as a source of the most intense radioactive beams of very exotic nuclei worldwide. ISAC is now been operational for more than 5 years, and has been proven to be able to deliver a broad variety of radioactive species with unsurpassed production yields, making it the facility of choice for a next generation ion trap facility, like TITAN. The physics goals of TITAN are manifold, but the emphasis lies on the test of the Standard Model via the determination of the V ud CKM matrix element, nuclear structure and halo-nuclei investigations, and nuclear astrophysics by providing precise and accurate mass measurements. [Copyright &y& Elsevier]

The Dresden EBIT – a compact room-temperature electron beam ion trap (EBIT) – is able to produce argon ions in all stages of ionization. From measured argon X-ray spectra we determine electron beam current densities of 176–514 A cm−2 at measured electron beam diameters of 145 and 102 μm, respectively. Direct excitation processes in Ar16+ are studied in dependence of additional helium and neon admixtures acting here as coolant. It is shown that the addition of different light gases leads to a specific increase of some ten percent of the argon X-ray output from the trap. [Copyright &y& Elsevier]

The electron beam ions traps (EBITs) are widely used to study highly charged ions (HCIs). In an EBIT, a high energy electron beam collides with atoms and ions to generate HCIs in the trap region. It is important to study the physics in the trap. The atomic processes, such as electron impact ionisation (EI), radiative recombination (RR), dielectronic recombination (DR) and charge exchange (CX), occur in the trap and numerical simulation can give some parameters for design, predict the composition and describe charge state evolution in an EBIT [Phys. Rev. A 43 (1991) 4861]. We are presently developing a new code, which additionally includes a description of the overlaps between the ion clouds of the various charge-states. It has been written so that it can simulate experiments where various machine parameters (e.g. beam energy and current) can vary throughout the simulation and will be able to use cross-sections either based on scaling laws or derived from atomic structure calculations. An object-oriented method is used in developing the new software, which is an efficient way to organize and write code. [Copyright &y& Elsevier]

The conceptual design of a new electron beam ion trap primarily intended for the study of electron–ion interactions is outlined along with some preliminary predictions regarding its capabilities. [Copyright &y& Elsevier]

With the Dresden EBIT it is possible to produce highly charged ions in a compact, economical and long-term stable ion source working at room temperature. The operation principle is based on electron impact ionization of primarily neutral atoms in a high-density electron beam in combination with electrical potentials for axial trapping. Radial trapping is realized by the negative space charge of the electron beam itself. After build-up the first Dresden EBIT in 1999 first results from a second EBIT device, the so-called Dresden EBIT II are presented. By means of X-ray spectroscopy we analyze the influence of different source parameters as ion trapping time, height of wall potentials and pressure on the production and storage of highly charged xenon ions. [ABSTRACT FROM AUTHOR]

The intensity ratio of Fe XIV 264.765A/274.203A is useful to determine the electron density of solar corona, and the relationship between the electron density and the intensity ratio obtained from a model should be evaluated using laboratory plasmas to estimate the electron density more precisely. We constructed a new collisional–radiative model (CR-model) for Fe XIV (an Al-like iron ion) by considering the processes of proton-impact excitation and electron-impact ionization to the excited states of a Mg-like iron ion. The atomic data used in the CR-model were calculated using the HULLAC atomic code. The model was evaluated based on laboratory experiments using a compact electron beam ion trap, called CoBIT, and the Large Helical Device (LHD). The measured Fe XIV 264.785 Å/274.203 Å line intensity ratio with CoBIT was 1.869 ± 0.036, and it agreed well with our CR-model results. Concurrently, the measured ratio using LHD was larger than the results of our CR-model and CHIANTI. The estimated electron densities using our CR-model agreed with those from CHIANTI within a factor of 1.6–2.4 in the range of n e ≈ 10 10 − 11 cm − 3 . Further model development is needed to explain the ratio in a high-electron density region. [ABSTRACT FROM AUTHOR]

HITRAP is a facility for deceleration of highly charged ions (HCI) produced online by the GSI accelerator. It consists of two linear stages for deceleration down to several keV/charge and an ion trap for ion cooling down to sub-eV energies. We report on two recent developments within the facility: a new design for the HITRAP cooling trap in order to improve its stability and voltage rigidity, as well as the investigation of the so-called MIVOC method in the HITRAP EBIT for production of Sb35+, Fe21+, and B5+. [ABSTRACT FROM AUTHOR]