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.
•Calculations of atomic average charges need an account of the target-density effect.•Average charges of superheavy elements are well scaled with Bohr parameter vZ1/3.•The density effect shifts the equilibrium fractions towards higher ion charges.
Processes of multiple electron-impact ionization of ions in a plasma and a beam passing through the plasma have been considered. Using experimental data and theoretical calculations of the cross ...sections for
n
-electron ionization
, the contribution from many-electron ionization rates
to the total ionization rate has been determined as a function of the electron temperature of the plasma
T
. It has been shown that the total contribution of many-electron ionization rates to the total ionization rate in ion beams passing through the plasma is determined by the relation between the velocity of an ion beam
and the thermal velocity of electrons in the plasma
. Many-electron ionization rates
have been numerically calculated for W
+
ions for electron temperatures of the plasma from 1 eV to 10 keV and velocities of the ion beam
= 0–30 a.u., where 1 a.u. ≈ 2.2 × 10
8
cm/s is the atomic unit of velocity.
Equilibrium charge-state fractions Fq and average charges 〈q〉 are calculated for low-charged Hfq+, Wq+ and Osq+ ions with the charges q = 0–3 colliding with He atoms at energies E = 0.5–25 keV/u. Fq ...and 〈q〉 values are obtained on the basis of electron-capture and electron-loss cross sections calculated by ARSENY and DEPOSIT codes briefly described in the paper. Calculated cross sections, Fq and 〈q〉 values, calculated also for other low-energy ion–atom collisions, are compared with available experimental data. The present results may be of interest for specialists studying low-energy beams of rare isotopes of Hf, W and Os ions.
A detailed description of a recently developed BREIT computer code (Balance Rate Equations of Ion Transportation) for calculating charge-state fractions of ion beams passing through matter is ...presented. The code is based on the analytical solutions of the differential balance equations for the charge-state fractions as a function of the target thickness and can be used for calculating the ion evolutions in gaseous, solid and plasma targets. The BREIT code is available on-line and requires the charge-changing cross sections and initial conditions in the input file.
The eigenvalue decomposition method, applied to obtain the analytical solutions of the rate equations, is described in the paper. Calculations of non-equilibrium and equilibrium charge-state fractions, performed by the BREIT code, are compared with experimental data and results of other codes for ion beams in gaseous and solid targets. Ability and limitations of the BREIT code are discussed in detail.
The study of slow collisions of heavy particles is a challenging task from both experimental and theoretical points of view. A powerful tool for the theoretical description of these collisions is the ...adiabatic theory of transitions in slow collisions developed by Solov’ev (1989), which is applied here to study low-energy charge exchange between tungsten ions and inert-gas atoms at 0.01–1 keV/u. It is found that the main mechanism of charge-exchange transitions in collisions of W+ ions with Ar and Kr atoms at energies below 1 keV/u is the rotational coupling associated with internuclear axis rotation in close collisions, while charge exchange between W8+ ions and He atoms is mainly due to the radial Landau–Zener type transitions. For all cases, potential curves as a function of the internuclear distance are calculated together with the charge-exchange cross sections. The cross sections obtained are compared with experimental data, showing good agreement and explaining the mechanisms of the transitions.
An overview of experimental data and theoretical methods is given for charge-changing processes with ion beams passing through gaseous, solid, and plasma targets. The main focus is on electron ...capture and electron loss processes involving heavy many-electron ions (like Arq+, Krq+, Pbq+, Wq+, Uq+) at relatively large and relativistic ion energies E = 50 keV/u − 50 GeV/u, including multielectron processes, which increase the total cross sections to about 50% or more. A large part of the paper is devoted to consideration of the stopping power of matter-the basic quantity characterizing kinetic energy losses of ions due to interactions with particles in matter. The electron capture processes for heavy ions colliding with atoms at low energies E < 10 eV/u and the arising isotopic effect are briefly discussed. The formation dynamics of charge-state fractions and average equilibrium charges in the ion beams interacting with medium particles are considered on the basis of the balance rate equations, including the creation of equilibrium charge-state fractions and average charges, an equilibrium target thickness and ion beam average charge, etc. A short description of the computer programs ETACHA, GLOBAL, CHARGE, and BREIT for calculating the charge-state fractions as a function of the target thickness is given, and some applications directly using charge-state fractions, e.g., in the detection of superheavy elements and in solving problems in laboratory and astrophysical plasmas, are considered. All physical processes and effects touched upon in the paper are explained in terms of atomic physics using the radiative and collisional characteristics of heavy many-electron ions interacting with electrons, atoms, ions, and molecules.
Stripping of relativistic uranium-ion beams by foils Shevelko, V.P.; Winckler, N.; Tolstikhina, Inga Yu
Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms,
09/2020, Letnik:
479
Journal Article
Recenzirano
The dynamics of relativistic uranium-ion beams stripped by foils from Be to Au is investigated in the 100–500 MeV/u energy range. Calculations of the charge-state distributions of uranium fractions ...as a function of foil thickness are performed using the BREIT code, based on the analytical solution of the balance rate equations for the ion charge-state fractions. Relativistic electron-loss and electron-capture cross sections, required for BREIT as input data, are calculated for interactions of Uq+ ions, q = 65–92, colliding with Be, C, Al, Ti, Cu, Mo, W, and Au atoms. The beam energy losses are found to be rather small, less than 20%, and are not accounted for in calculations. Calculated charge-state distributions are compared with available experimental data, obtained at the GSI (Gesellschaft für Schwerionenforschung) and BEVALAC (Bevatron Linear Accelerator) facilities, and with calculations by the GLOBAL code created at GSI.The optimal conditions are predicted for production of bare, H-like, He-like and Li-like uranium ions with the largest probabilities. Dependencies of the equilibrium thicknesses for uranium charge-state fractions on the initial charge of incident ions are investigated.
The ratio R=σ(H2)/σ(H) of single-electron capture cross sections of positively charged ions colliding with H and H2 targets was investigated at ion energies E= 2 keV/amu–200 MeV/amu and ion charges ...q=1−74 using the Brinkman–Kramers approximation with normalized capture probabilities. The dependence of the R ratio on the polar angle θρ between H2-molecule axis and the projectile-velocity direction was studied for angles 0∘≤θρ≤90∘. It was shown that at certain angles θρ, the R ratio exhibits an oscillatory structure caused by interference of two waves scattered on two atomic centers of H2 molecule. At scaled energies Ẽ=E(keV/amu)/q4/7≈102–103, the R ratios, obtained by averaging the corresponding σ(H2) cross sections over all orientations of H2 target, also show an oscillatory structure, the shape of which depends on the ion charge q. At higher energies Ẽ≈103−105, the R ratio calculated for charges q=1−74 is nearly independent on q and is equal to R≈2.82, while the Bragg’s rule gives R=2. In the present paper, the R≈2.82 value is explained by modeling a H2 molecule as a He atom with ionization energy I=15.43eV, equal to the binding energy of the H2 molecule. Computed ratios are compared with available experimental data, semi-empirical formulae and other calculations.
Charge-changing processes of low-charged ions, used in hydrogen plasma probing by the heavy ion beam probe method, are considered. Along with the ionization of beam ions by plasma electrons and ...protons, the charge-exchange processes of ions on H atoms and protons are also studied. It is shown that charge exchange of beam ions on plasma protons and H atoms, which is rarely taken into account, plays an important role in beam–plasma interaction. New data on the cross sections and rates of ionization and charge-exchange processes are presented for Tl+ and Tl2+ ions, which are frequently used for plasma diagnostics. Calculations are performed for hydrogen plasma temperatures Te = 1 eV–10 keV and densities Ne = 1012–1014 cm−3 at relatively low and high ion-beam velocities vb = 0.2 and 1.0 a.u., respectively. Special attention is paid to the determination of the electron temperatures at which the charge-exchange processes on H atoms and protons are important. Multiple ionization of beam ions by plasma electrons and protons is briefly discussed.
In this paper, an experiment has been analyzed in which an arc discharge in argon was ignited between a carbon cathode and an anode. Argon was supplied to a discharge combustion region bounded by a ...quartz cylinder. The radiation of the arc discharge passed through a light filter and was focused on an optical fiber and then transmitted to the spectrometer through it. Spectral analysis showed that the temperature within the arc in these experimental conditions is
K. The concentration of the plasma components was calculated based on the Saha equation for atoms and electrons, as well as for ArI and ArII ions. It was found that ArI ions are the primary plasma particles in the experiment.
