Heavy Multicharged Ions Research Articles

Space weathering on inner planetary surface analogues induced by swift multicharged heavy ion bombardment

Silicates are ubiquitous in space. They dominate the surfaces of the inner rocky planets (Mercury in the case of the Solar System), the Moon, and asteroids, forming the major part of the non-volatile material. The physical and chemical properties of the rocky surfaces are determined not only by their initial composition but also by the processes occurring on them. Here we discuss one of these processes; irradiation by energetic cosmic particles that induces many effects among which structural changes and sputtering, the latter contributing to the formation of exospheres. In the current work we report the results of experiments conducted on anorthite, jadeite and nepheline silicates that have been irradiated with energetic heavy ions with the aim to better understand the interaction of galactic cosmic rays, solar wind, and solar energetic particles with planetary and small body surfaces. The sputtering effects induced by energetic (MeV/u) multicharged heavy ions (e.g., 105Rh and 140Ba) were analyzed by the PDMS-TOF-SIMS technique (plasma desorption mass spectrometry - time-of-flight secondary ion mass spectrometry). Positive and negative secondary ionic species are identified: Na+, K+, Al+, Ca+, SiO2−. Ejection of (SiO2)n− and (AlSi)Om− cluster series are also observed. Less frequent, negative ion yields are one order of magnitude less than positive ones, or greater, which is the case for nepheline, with 0.671 ions impact−1 for positive and 0.126 ions impact−1 for negative ions. The results concerning ejection of ionic species show, for instance, that the Na+/K+ ratio is ~2.5, which is in very good agreement with that observed in the Hermean exosphere found to be ~2.3.

Energetic ion irradiation of N2O ices relevant for Solar system surfaces

ABSTRACT Ices are the dominant surface material of many Solar system objects, such as comets and trans-Neptunian objects. They are continuously exposed to ion bombardment by solar wind ions and cosmic rays, which trigger secondary ion emission, contributing to the exosphere formation. Laboratory studies demonstrated the effects of energetic processing of ices at low temperature, showing the production of molecules and free radicals of astrophysical interest. Nitrous oxide (N2O) is one of the molecular species observed in star-forming sites, reason why it may be present in the ices covering some minor bodies in the outer Solar system. In the current work, N2O ice at 10 K was irradiated by energetic (MeV/u) multicharged heavy ions (e.g. 105Rh and 140Ba); the sputtered species were detected and analysed by the TOF-PDMS technique (time-of-flight plasma desorption mass spectrometry). Small positive and negative secondary ions were identified: N+, N2+, NO+, O+, and O−. The bombardment also induces production of ion cluster series: (N2)nR$_{m}^+$, (NO)nR$_{m}^+$, (N2O)nR$_{m}^+$, where R = N+, N2+, NO+, N2O+, Om+ (n up to ∼ 10, m = 1−3). Their yield distributions follow the sum of two decreasing exponentials, one fast -F and another slow -S, suggesting a two-regime formation. Most of the yield distributions have the same pair of exponential decay constants, around kF ∼ 1.4 and kS ∼ 0.15 u−1. Based on this behavior, an emission description for aggregates is proposed, useful to understand the processes by which neutral and ionized molecular species are delivery to the gas phase in space.

Multi-Charged Heavy Ion Sources for Radioactive Isotope Beam Factory

Multi-Charged Heavy Ion Sources for Radioactive Isotope Beam Factory

Feasibility study of a compact heavy ion source for investigation of laboratory magnetospheric plasma.

We are developing a laser ion source to provide a high brightness multi-charged heavy ion beam as a part of the heavy ion beam probe system, which will be used to diagnose plasma potential in the Ring Trap 1 device at the University of Tokyo. As a probe beam, Nb2+ was selected, and a detailed laser irradiation condition was explored. It was found that the laser power density of 1.2 × 109 W/cm2 gives the maximum particle number of Nb2+ per laser energy from a niobium foil target. Essential ablation plasma parameters to design the laser ion source were also obtained. The expected beam current was more than 12 mA/cm2, with a pulse width of 3.1 µs at 200 mm away from the target.

Multi-charged heavy ion acceleration from the ultra-intense short pulse laser system interacting with the metal target

Experimental demonstration of multi-charged heavy ion acceleration from the interaction between the ultra-intense short pulse laser system and the metal target is presented. Al ions are accelerated up to 12 MeV/u (324 MeV total energy). To our knowledge, this is far the highest energy ever reported for the case of acceleration of the heavy ions produced by the <10 J laser energy of 200 TW class Ti:sapphire laser system. Adding to that, thanks to the extraordinary high intensity laser field of ∼10(21) W cm(-2), the accelerated ions are almost fully stripped, having high charge to mass ratio (Q/M).

Non-Equilibrium Heavy Gases Plasma MHD-Stabilization in Axisymmetric Mirror Magnetic Trap

Experimental researches of the shear flows influence on the confinement in the mirror trap of the dense nonequilibrium helium and nitrogen plasma created under conditions of the electron cyclotron resonance (ECR) gas breakdown were made.Limiter with electric potential relative to the vacuum chamber was set inside the mirror trap.During the increasing of the value of limiter potential over Ucrit = 70-100 V the considerable increasing of the full ion flux from the trap was obtained (about of 3-4 times) that is apparently indicates that the plasma density and may be electron temperature increased in the trap that can be interpreted as the transversal losses decrease that is the result of “vortex confinement” regime realization. Pointed effect was obtained in the helium and nitrogen plasma both. Azimuthal modes with m = 1, m = 2 dominated in spatial spectrum of plasma oscillations.This method of “vortex confinement” regime realization for non-equilibrium heavy ions plasmas seems to be perspective for new generation of ECR heavy multicharged ion sources creation.

Status report of the heavy ions source research and development for Spiral2

The physics background requiring a very intense multicharged heavy ion source for Spiral2 is explained. The new Spiral2 low energy beam line dedicated to the heavy ions production and equipped with PHOENIX V2 ECRIS is presented. A status of the A-PHOENIX commissioning at 18 GHz is summarized. A new hybrid ECRIS concept with a cryogenic permanent magnet hexapole is proposed as an improvement of A-PHOENIX technology.

Acceleration of heavy multicharged ions in the interaction of a subrelativistic femtosecond laser pulse with a melted metal surface

Results are presented from experimental studies of ion acceleration under the action of femtosecond laser pulses with an intensity of 1017 W/cm2, incident onto the free surfaces of melted gallium and indium. The effect of the polarization direction of a linearly polarized laser pulse and the amplitude of a short prepulse, which precedes the main pulse by several nanoseconds, on the parameters of accelerated ions is investigated. It is found that, even for such a moderate laser intensity, the characteristic velocity of fast ions ejected along the reflected beam is a factor of 1.5 higher than that of ions ejected along the normal to the target surface. It is shown that, as the prepulse energy increases, the hard X-ray yield and the mean energy of hot electrons increase substantially, whereas the velocity of both fast and slow ions decreases appreciably regard-less of laser polarization.

Improved atomic masses ofKr84,86andXe129,132

Using single ions in a cryogenic Penning trap we have remeasured the atomic masses of $^{84,86}\mathrm{Kr}$ and $^{129,132}\mathrm{Xe}$ with the results $M[^{84}\mathrm{Kr}]=83.911$ 497 731(8) u, $M[^{86}\mathrm{Kr}]=85.910$ 610 628(8) u, $M[^{129}\mathrm{Xe}]=128.904$ 780 859(11) u, and $M[^{132}\mathrm{Xe}]=131.904$ 155 086(10) u. These results supersede those previously reported by Shi, Redshaw, and Myers [Phys. Rev A 72, 022510 (2005)], which suffered from systematic error associated with the comparison of heavy multicharged ions with singly charged reference ions.

Formation of fast multicharged heavy ions under the action of a superintense femtosecond laser pulse on the cleaned surface of a target

It is found that the mean charge of tungsten ions in a solid tungsten target cleaned from the surface layer of hydrocarbon and oxide compounds and exposed to femtosecond laser radiation with an intensity exceeding 1016 W/cm2 attains 22+, while the maximum charge is 29+. The maximum energy of such ions approaches 1 MeV. The corresponding values obtained on a dirty target with the same laser pulse parameters constitute 3+, 5+, and 150 keV. The results of numerical simulation show that such a large maximum charge of ions can be attained owing to the emergence of an electrostatic ambipolar field at the sharp boundary between the plasma and vacuum. The main mechanism of ionization of ions with maximum charges is apparently impact ionization in the presence of an external quasi-static field. In addition, direct above-threshold ionization by this field can also play a significant role. It is also shown that heavy ions in a clean target are accelerated by hot electrons. This leads to the formation of high-energy ions. The effect of recombination on the charge of the ions being detected is analyzed in detail.

Acceleration of heavy multicharged ions up to 1 MeV from a cleaned solid target irradiated by a femtosecond laser pulse with an intensity of 1016 W/cm2

A noticeable increase in the charge and energy of ions accelerated from a solid tungsten target irradiated by a femtosecond laser pulse with an intensity higher than 1016W/cm2 has been found when the target surface is precleaned by a nanosecond laser pulse with an energy density of 3 J/cm2. Tungsten ions with charges up to +29 and energies up to 1 MeV were detected in this case, while the charge and energy of tungsten ions from a target with an uncleaned surface do not exceed +3 and 12 keV, respectively.

Saturation Current Densities at the Critical Point of a Spherical Probe in a Moving Collisional Plasma with Negative Ions or Dust Grains

The problem is considered of the probe diagnostics of a moving, weakly ionized, collision-dominated plasma containing singly charged negative ions or dust grains (heavy multicharged ions). Based on an asymptotic analysis, expressions are obtained that describe the saturation current densities of the electrons and of the charged particles of other species at the point where the plasma flowing around a spherical probe in the laminar boundary layer regime stagnates.

High-Power CO2Laser System with Repetition Rate Operation for High Current Multicharged Heavy Ion Generations

Experimental and numerical calculation results devoted to development of an optical system for an ion source based on a repetition rate CO2 laser are described. The laser chain consists of a master oscillator, gas absorber cells, and a four-pass amplifier. The optical system provides smooth laser pulses with variable duration and high spatial quality that ensures efficiency for plasma heating and ion generation. The parameters of the plasma ion component measured in the CERN laboratory are applied for a lead target illumination.

Nuclear-polarization effect to the hyperfine structure in heavy multicharged ions

We have investigated the correction to the hyperfine structure of heavy multicharged ions, which is connected with the nuclear-polarization effect caused by the unpaired bound electron. Numerical calculations are performed for hydrogenlike ions taking into account the dominant collective nuclear excitations. The correction defines the ultimate limit of precision in accurate theoretical predictions of the hyperfine-structure splittings.

Generation of high-quality charged particle beams during the acceleration of ions by high-power laser radiation

Numerous applications of protons and ions accelerated by laser radiation require charged particle beams of high quality (i.e., such that the ratio of the energy width of the beam to its mean energy is small). In order to produce beams with controlled quality, it is proposed to use two-layer targets in which the first layer consists of heavy multicharged ions and the second layer (thin and narrow in the transverse direction) consists of protons. The possibility of generating a high-quality proton beam in the interaction of ultraintense laser radiation with such a two-layer target is demonstrated by two-and three-dimensional particle-in-cell computer simulations.

Overlapping identical resonances and radiative interference effects in recombination of heavy multicharged ions

The purely QED effect of double radiative interference in the recombination of electrons with heavy multicharged ions is discussed. Numerical calculations of the corresponding cross sections in the vicinities of the KL12M12 and KM12M12 dielectronic recombination resonances of heliumlike uranium are reported. The possibility of near-future experimental observation of the effect with the Super-EBIT facility is suggested.

Fast ion-induced CO molecule fragmentation in the strong interaction regime

A coincident time of flight technique is used to investigate fast ion-induced CO molecule fragmentation with swift and multicharged heavy ions. The results concern the strong interaction regime for which no data have yet been reported. Kinetic energy release distributions, branching ratios and multi-electron removal cross sections are determined for each dissociation channel of ions (Q = 2-9). The general trend, from the perturbative regime to the strong interaction regime, is analysed in the light of recent ion-atom advances. The use of recoil ion momentum spectroscopy to study one dissociative single ionization channel - with simultaneous excitation - greatly improves the experimental KER resolution. Furthermore, it allows a coincident measurement of the angular and kinetic energy release distributions. This technique is proved promising for molecular spectroscopy studies.

Overlapping identical resonances and double radiative interference effects in recombination of heavy multicharged ions

The purely QED effect of double radiative interference in the recombination of electrons with heavy multicharged ions is discussed. Numerical calculations of the corresponding cross sections in the vicinities of the KL12M12 and KM12M12 dielectronic recombination resonances of heliumlike uranium are reported. The possibility of near-future experimental observation of the effect with the Super-EBIT facility is suggested.

Fragmentation of CO + molecular ion through dissociative excited states produced by swift multicharged heavy ion impact on CO molecules

CO+ molecular ion excitation induced by 6.7 MeV/amu Xe44+ ion impact was studied using recoil ion momentum spectroscopy. The Kinetic Energy Release (KER) distribution clearly shows the population of highly excited states. Excellent agreement is observed when comparing this distribution to previous low lying states calculation. Surprisingly high KER components were present in our spectra with values as high as 29 eV. The simple Coulomb model is obviously unable to explain the measured fragmentation energies for the process , involving a neutral fragment.

Nuclear polarization effects in spectra of multicharged ions

We evaluate the nuclear-polarization energy shifts for one-electron 208 82Pb and 238 92U ions. In contrast to previous calculations, the effect of nuclear polarizability is found to be essentially of minor significance for high-precision measurements of the Lamb shift in heavy multicharged ions. The calculations are carried out employing different numerical methods. We also provide a comparison of our numerical results with analytical estimates.