Superheavy Ions Research Articles

Average charges of superheavy Fl (Z[formula omitted]114), Mc (Z[formula omitted]115), Lv (Z[formula omitted]116) and Ts (Z[formula omitted]117) ions passing through He-gas target at ion energies [formula omitted] 0.25 – 300 keV/u

Equilibrium charge-state fractions Fq and average charges 〈q〉 are calculated for ion beams of superheavy Flq+, Mcq+, Lvq+ and Tsq+ ions with charges q= 0 – 11 colliding with He atoms at ion energies E= 0.25 – 300 keV/u. The data are obtained using electron-loss and capture cross sections, calculated for He-gas pressures P= 0 and P=0.8 mbar with account for the target-density effect. At energies E≈ 0.25 – 10 keV/u, the influence of the effect is found small, but at higher energies E≥ 10 keV/u, it becomes important and leads to increase of 〈q〉 values by 3 – 5 times.Calculated average charges are in a good agreement with experimental data and semi-empirical estimates available at E= 132 keV/u and P=0.8 mbar. The 〈q〉 values are also compared with experimental data and other calculations for heavy and superheavy ions with atomic numbers Z= 38 – 114 as a function of the Bohr scaling parameter vZ1/3, where v is the ion velocity.

Alternating phase focusing beam dynamics for drift tube linacs

In contrast to conventional E-mode resonance accelerators, H-mode DTLs provide for compact linac sections and have been established as highly efficient resonators during the last decades. Thus, H-mode structures are widely applied for heavy-ion acceleration with medium beam energies because of their outstanding capability to provide high acceleration gradients with relatively low energy consumption. To build upon those advantages, an alternating phase focusing beam dynamics layout has been applied to provide for a resonance accelerator design without internal lenses, which allows for eased commissioning, routine operation, maintenance, and potential future upgrades. The features of such a channel are going to be demonstrated on the example of two interdigital H-mode cavities, separated by an external quadrupole triplet. This setup provides for heavy ion (mass-to-charge ratio A/z≤6\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$A/z\\le 6$\\end{document}) acceleration from 300 keV/u to 1400 keV/u and is used as an injector part of the superconducting continuous wave accelerator HELIAC. Hence, this promising approach generally enables effective and compact routine operation for various applications, such as super heavy ion research, material science, and radio biological applications such as heavy-ion tumor therapy.

Super-heavy ion beams generated by a multi-PW femtosecond laser

The numerical investigations into the acceleration of superheavy ions driven by a multi-PW, 30 fs laser pulse with a peak intensity from 5 × 1022 to 2 × 1023 W/cm2 were carried out using an advanced 2D3V particle-in-cell code. The properties of laser-accelerated Au, Pb, Bi, and U ion beams, such as ionization and ion energy spectra, ion beam energies, angular distributions of the beam fluence, the ion pulse shapes, and peak intensities, were examined and compared. It was found that for a laser intensity of 1023 W/cm2, a common feature of the Au, Pb, Bi, and U ion beams was the dominance in the beam of Ne-like ions that carry the vast majority (≥90%) of the energy of all accelerated ions and have by far the highest mean and maximum ion energy. The Ne-like ion beams for Au, Pb, Bi, and U have almost identical angular fluence distributions and ion pulse shapes, as well as peak fluencies and intensities. However, the dependence of the parameters of the Ne-like ion beam on the laser intensity is different for ions with different masses. In the considered laser intensity range, the heaviest ions (U ions) ensured the achievement of the highest beam parameters, such as the mean and maximum ion energy, the ion beam energy, or the laser-to-ions energy conversion efficiency. The mono-charge superheavy ion beams demonstrated in this paper open the prospect for novel applications of heavy ions in high energy-density physics, nuclear physics, and possibly in other fields.

Furnace ion source with electron ionization for calibrating a spectrometer for precise determination of masses of superheavy elements

Precise determination of the isotope masses of superheavy elements obtained by the complete fusion of 48Ca+ ions with Au, Pb, Bi, U, and Pu targets can provide valuable information on the mechanisms of nuclear reactions leading to the formation of these elements. A specialized multi-turn time-of-flight mass spectrometer is to be used to match the goal. The source of the target isotopes is a DC-280 cyclotron, a «factory of superheavy elements» at the Joint Institute for Nuclear Research (JINR, Dubna, Russia). The point of the problem is that ions of superheavy elements are formed quite rarely even in the specialized accelerator of JINR: during the last experiment, the frequency of their appearance was up to 10 events per day. Precise determination of the mass number requires comparing the time of flight of a superheavy ion through a mass analyzer with the same time for a calibrant ion, the mass number and charge of which are precisely known a priori from the process of its formation. Implementation of such a mass spectrometric analysis required the development of an ion source capable of stable operation for a long time. To solve the problem, a number of ion sources were considered. The choice of an ion source with electron ionization is substantiated. A source with a crucible in which the calibrant evaporates during heating was proposed and tested. Various substances (PbBr2, Nd, C60, fullerene soot) were considered as a calibrant. The mass spectra of these compounds are presented, namely, the spectrum of neodymium compounds and the mass spectrum of fullerene soot. It is shown that the use of fullerene soot is optimal, since the mass spectrum of fullerene soot contains ions in the range of mass numbers from 12 to 800 and higher. Moreover, the mass spectrum of fullerene soot contains many peaks in the mass number region of interest 275 – 300 a.m.u. It has been experimentally shown that the ion intensities within the indicated range differ by less than an order of magnitude which makes the use of fullerene soot a standard sample for calibration of a high-resolution time-of-flight mass spectrometer.

Towards single-charge heavy ion beams driven by an ultra-intense laser

The acceleration of super-heavy ions from an ultra-thin lead target irradiated by a femtosecond laser pulse with an intensity in the range of ∼1022–1023 W cm−2 was investigated using an advanced 2D3V particle-in-cell code. It is shown that by properly selecting the laser pulse parameters, it is possible to produce a practically single-charge Pb ion beam with multi-GeV ion energies and the laser-to-ions energy conversion efficiency approaching 30%. At the laser intensity of 1023 W cm−2, Pb ions with the charge state Z = 72 carry over 90% of the total energy of all ions, while the peak intensity and peak fluence of the Pb+72 ion beam are at least two orders of magnitude higher than for other types of ions. In addition, the Pb+72 ion beam is more compact and has a smaller angular divergence than those for other types of ions. The above properties of the Pb+72 ion beam mean that further energy-efficient purification of the beam from other types of ions is possible, even in simple ion transport and selection systems.

Electronic Structure of Lr+ (Z = 103) from Ab Initio Calculations

The four-component relativistic Dirac–Coulomb Hamiltonian and the multireference configuration interaction (MRCI) model were used to provide the reliable energy levels and spectroscopic properties of the Lr+ ion and the Lu+ homolog. The energy spectrum of Lr+ is very similar to that of the Lu+ homolog, with the multiplet manifold of the 7s2, 6d17s1 and 7s17p1 configurations as the ground and low-lying excited states. The results are discussed in light of earlier findings utilizing different theoretical models. Overall, the MRCI model can reliably predict the energy levels and properties and bring new insight into experiments with superheavy ions.

Super-Heavy Ions Acceleration Driven by Ultrashort Laser Pulses at Ultrahigh Intensity

Laser ion acceleration driven by the utmost intense laser pulses pushes superheavy gold ions to unprecedented energies, key for applications ranging from nuclear physics to next-generation accelerators.

Mobility of the Singly-Charged Lanthanide and Actinide Cations: Trends and Perspectives.

The current status of gaseous transport studies of the singly-charged lanthanide and actinide ions is reviewed in light of potential applications to superheavy ions. The measurements and calculations for the mobility of lanthanide ions in He and Ar agree well, and they are remarkably sensitive to the electronic configuration of the ion, namely, whether the outer electronic shells are 6s, 5d6s or 6s2. The previous theoretical work is extended here to ions of the actinide family with zero electron orbital momentum: Ac+ (7s2, 1S), Am+ (5f77s 9S°), Cm+ (5f77s2 8S°), No+ (5f147s 2S), and Lr+ (5f147s2 1S). The calculations reveal large systematic differences in the mobilities of the 7s and 7s2 groups of ions and other similarities with their lanthanide analogs. The correlation of ion-neutral interaction potentials and mobility variations with spatial parameters of the electron distributions in the bare ions is explored through the ionic radii concept. While the qualitative trends found for interaction potentials and mobilities render them appealing for superheavy ion research, lack of experimental data and limitations of the scalar relativistic ab initio approaches in use make further efforts necessary to bring the transport measurements into the inventory of techniques operating in “one atom at a time” mode.

Towards ultra-intense ultra-short ion beams driven by a multi-PW laser

AbstractThe multi-petawatt (PW) lasers currently being built in Europe as part of the Extreme Light Infrastructure (ELI) project will be capable of generating femtosecond light pulses of ultra-relativistic intensities (~1023–1024 W/cm2) that have been unattainable so far. Such laser pulses can be used for the production of high-energy ion beams with unique features that could be applied in various fields of scientific and technological research. In this paper, the prospect of producing ultra-intense (intensity ≥1020 W/cm2) ultra-short (pico- or femtosecond) high-energy ion beams using multi-PW lasers is outlined. The results of numerical studies on the acceleration of light (carbon) ions, medium-heavy (copper) ions and super-heavy (lead) ions driven by a femtosecond laser pulse of ultra-relativistic intensity, performed with the use of a multi-dimensional (2D3 V) particle-in-cell code, are presented, and the ion acceleration mechanisms and properties of the generated ion beams are discussed. It is shown that both in the case of light ions and in the case of medium-heavy and super-heavy ions, ultra-intense femtosecond multi-GeV ion beams with a beam intensity much higher (by a factor ~102) and ion pulse durations much shorter (by a factor ~104–105) than achievable presently in conventional radio frequency-driven accelerators can be produced at laser intensities of 1023 W/cm2 predicted for the ELI lasers. Such ion beams can open the door to new areas of research in high-energy density physics, nuclear physics and inertial confinement fusion.

Current Status of the NUKLON-2 Space Mission

The NUKLON-2 experiment is aimed at measuring the isotope and charge composition of cosmic rays for medium, heavy, and superheavy ions (Z < 82) with energies between 300 MeV/nucleon and 1 GeV/nucleon. The design of the planned satellite-borne NUKLON-2 cosmic-ray detector is presented. Modeling of the detector’s performance indicates the adopted isotope-separation techniques are effective.

Ultra-intense femtosecond super-heavy ion beams driven by a multi-PW laser

The paper reports the results of numerical studies on the laser-driven acceleration of super-heavy ions by a multi-PW laser pulse of ultra-relativistic intensity attainable with the Extreme Light Infrastructure lasers currently being built in Europe. Using a multi-dimensional (2D3V) particle-in-cell code, it is shown that multi-GeV super-heavy (thorium) ion beams with an intensity of ∼1021–1022W/cm2, fluence ∼1017–1018cm−2 and time duration ∼20–100fs can be produced from a sub-μm thorium target irradiated by a 150-J, 20-fs laser pulse with an intensity of 1023W/cm2. Such ion beams are impossible to obtain presently with the use of conventional RF-driven accelerators, so they can open the door to new areas of research in both nuclear and high energy-density physics.

GAUGE-INVARIANT RELATIVISTIC PERTURBATION THEORY APPROACH TO DETERMINATION OF ENERGY and SPECTRAL CHARACTERISTICS FOR HEAVY AND SUPERHEAVY ATOMS AND IONS: REVIEW

We reviewed an effective consistent ab initio approach to relativistic calculation of the spectra for multi-electron heavy and superheavy ions with an account of relativistic, correlation, nuclear, radiative effects is presented. The method is based on the relativistic gauge-invariant (approximation to QED) perturbation theory (PT) and generalized effective field nuclear model with using the optimized one-quasiparticle representation firstly in theory of the hyperfine structure for relativistic atom. The wave function zeroth basis is found from the Dirac equation with potential, which includes the core ab initio potential, the electric and polarization potentials of a nucleus. The correlation corrections of the high orders are taken into account within the Green functions method (with the use of the Feynman diagram’s technique). There have taken into account all correlation corrections of the second order and dominated classes of the higher orders diagrams (electrons screening, particle-hole interaction, mass operator iterations). The magnetic inter-electron interaction is accounted in the lowest on α parameter (α is the fine structure constant), approximation, the self-energy part of the Lamb shift is taken effectively into consideration within the Ivanov-Ivanova non-perturbative procedure, the Lamb shift polarization part - in the generalized Uehling-Serber approximation with accounting for the Källen-Sabry α2 (αZ) and Wichmann-Kroll α(αZ)n corrections.

Prospects for laser spectroscopy, ion chemistry and mobility measurements of superheavy elements in buffer-gas traps

Laser spectroscopic methods are reviewed which are of potential interest for the investigation of atomic and ionic level structures of superheavy elements. The latter are defined here as the trans-fermium elements with Z>100 for which no experimental atomic or ionic level structure information is known so far, and which cannot be bred in high flux nuclear power reactors via successive neutron capture. The principles of suitable laser spectroscopic methods are described, and illustrated by examples of real experiments. The addressed methods include single-ion spectroscopy in Paul traps, laser-induced fluorescence spectroscopy (LIF), radiation-detected optical pumping (RADOP), radioactive decay-detected resonance ionization spectroscopy (RADRIS), and ion-guide-detected resonance ionization spectroscopy (IGRIS). With the exception of the first all take advantage of a storage of the ions or atoms in so-called buffer-gas traps.The developed experimental methods can, in principle, also be employed for studying ion-chemical reactions with gas admixtures like O2 as well as for performing ion mobility measurements. Both provide complementary information on the electronic structure of superheavy ions. First attempts on this road of research are reviewed as well.

Evaluation of the stopping powers of superheavy ions with values of Z up to 124 in Al and U

The electronic and the nuclear stopping powers of superheavy ions with values of Z up to 124 and A = 300 in Al and U were estimated in the energy range of 0.01–0.20 MeV/u. The corresponding stopping powers were estimated by using the stopping powers of ions with 6 ≤ Z ≤ 92 obtained from SRIM. The results were compared with those deduced from Northcliffe and Schilling’s stoppingpower tables and with experimental data for 16O and 19F ions in Al. The estimated electronic stopping powers of the light ions agreed better with their experimental values at energies above 0.10 MeV/u than the SRIM data did.

Influence of relativistic effects on electron-loss cross sections of heavy and superheavy ions colliding with neutral atoms

The influence of relativistic effects, such as relativistic interaction and relativistic wave functions, on the electron-loss cross sections of heavy and superheavy atoms and ions (atomic number Z ≳ 92) colliding with neutral atoms is investigated using a newly created RICODE-M computer program. It is found that the use of relativistic wave functions changes the electron-loss cross section values by about 20–30% around the cross-section maximum compared to those calculated with nonrelativistic wave functions. At relativistic energies E ≥ 200 MeV/u, the relativistic interaction between colliding particles leads to a quasiconstant behavior of the loss cross sections σELrel ∼ const, to be compared with the Born asymptotic law σELB ∼ lnE/E.

Average charge states of heavy and superheavy ions passing through a rarified gas: Theory and experiment

The average charge states $\overline{q}$ of heavy and superheavy ions (atomic numbers $Z=80$--114) passing through He gas are studied experimentally and theoretically. Experimental data were measured at the gas-filled recoil separator, i.e., the TransActinide Separator and Chemistry Apparatus (TASCA) at GSI Darmstadt, for ion energies of a few hundred keV/u at gas pressures of 0.2 to 2.0 mbar. An attempt is made to describe experimental $\overline{q}$ values by means of atomic calculations of the binding energies and electron-loss and electron-capture cross sections. The influence of the gas-density effect is included in the calculations. The calculated $\overline{q}$ reproduce the experimental values for elements with $Z=80$--114 within 20%. A comparison with different semiempirical models is presented as well, including a local fit of high accuracy, which is often used in superheavy-element experiments to estimate the average charge states of heavy ions, e.g., at the gas-filled recoil separator TASCA. The $\overline{q}$ values for elements with $Z=115$, 117, 119, and 120 at He-gas pressure of 0.8 mbar are predicted.

ESTIMATION ON STOPPING POWERS OF SUPERHEAVY ION WITH Z=120 AND A=300 IN SEVERAL MEDIA

Stopping powers of superheavy ion with Z=120 and A=300 have been estimated in several media in the energy region 0.0177≤E/A≤0.141 MeV / amu . The electronic and nuclear stopping powers of ions with 6≤Z≤92 calculated by SRIM have been used to estimate the corresponding stopping powers of the superheavy ion. The media included two solid compounds (UF4 and Mylar) and two gases ( He and butane). The results were compared with those deduced from Northcliffe and Schilling's stopping-power tables.

A new stopping power parameterization for 0.1–15MeV/nucleon heavy and superheavy ions in solids and gases

Abstract Electronic stopping powers of heavy ions in several media are deduced from the corresponding proton data by using new effective charge parameterizations. Separate sets of parameters were deduced for solid and gaseous materials using the available data for heavy ions in the energy range from 0.1 to 15 MeV/nucleon. Using these results, predictions are made for stopping powers of heavy and superheavy elements with Z = 100–130 in the energy range of 0.5–15 MeV/nucleon.

Investigation of the passage of 100–1000-MeV/nucleon superheavy ions through homogeneous media

This work is a continuation of the experimental and theoretical investigations of the effect of the Z 1 3 correction to the stopping power of ions on the passage of heavy ions 40Ar, 56Fe, 197Au, 131Xe, and 238U with energies of about 1 GeV/nucleon through a homogeneous medium. The previously observed systematic deviations of the calculations based on the first Born approximation to the scattering of a particle by the atomic electrons in the medium from the experimental values of the total ionization ranges of the nuclei and their stopping powers is confirmed. The discrepancy increases with the atomic number of the projectile nucleus. It is shown that the Z 1 3 correction in the form proposed by Jackson and McCarthy eliminates, especially for ions with Z1>50, the systematic discrepancy between the computed and experimental values. For the experimental energy range relativistic Mott scattering of a particle by the atomic electrons in the target makes the dominant contribution to the observed Z 1 3 effect.

Effects of the Breit interaction on the 1s binding energy of superheavy elements

Dirac-Fock calculations of the 1s binding energy of superheavy ions in the He, Ne, Xe and Rn isoelectronic series are presented. Complete e+-e- interaction (Breit interaction) is studied. Various effects due to this interaction are discussed in detail, and particularly effects which arise when the magnetic part of the Breit interaction is included in the self-consistent field process. For the RN-like series the calculations is made beyond the ( nu /c)2 approximation, to all orders in the energy of the exchange photon.