Kr Ions Research Articles

DTs-60 cyclotron complex for scientific and applied research and commercial applications in nanotechnology

An accelerator complex has been developed on the basis of the DTs-60 cyclotron for performing scientific and applied research and for commercial application in nanotechnology. The complex was designed and constructed at the Laboratory of Nuclear Reactions of the Joint Institute for Nuclear Research for the Interdisciplinary Scientific and Research Center at the L. N. Gumelev Eurasian National University (Kazakhstan). Intense beams of heavy ions of Ne, Ar, Kr, and other elements have been obtained and accelerated in the cyclotron. Various polymer films have been irradiated and several control batches of track membranes have been prepared in a wide range of densities of the openings. The complex is a unifying factor in the development of technologies, science, and science-intensive business and is intended for producing track filters, developing commercial technologies using nano-and microstructures based on nuclear membranes and for creating a scientific environment in Kazakhstan.

Letters to the Editor

Sir, Reply to comments of U. German, M. Weinstein, A. Abraham, and Z. B. Alfassi. I am inclined to discontinue the ‘discussion’ and agree with German et al. that the issue of the credibility of the application of HTTL to the dosimetry of neutrons, be they fast or thermal, be the chips properly annealed or not, be they be heated by gas, or contact or laser, or of the dosimetry of ‘high-LET’ particles be they low MeV protons or GeV Kr ions should indeed be treated in future publications.

Cation Sublattice Disorder Induced by Swift Heavy Ions in MgAl2O4 and ZnAl2O4 Spinels: 27Al Solid-State NMR Study

MgAl2O4 and ZnAl2O4 spinels have been irradiated by swift heavy ions (86Kr and 36S) simulating the irradiation by fission products for applications in the transmutation targets. The structures of unirradiated and irradiated spinel samples have been studied by NMR spectroscopy, with 27Al magic angle spinning and multiple-quantum magic angle spinning experiments. The parameters of fluence and electronic stopping power have been compared. For 86Kr ions, the obtained spectra are modified by irradiation: we observe a rise of the amount of aluminum in tetrahedral sites and a widening of the lines associated with the different aluminum environments compared with those of the pristine samples. Site exchange in the cationic sublattice is then observed and can be quantified from NMR spectra, determining the inversion parameter. An inversion parameter of 0.77 is estimated for the MgAl2O4 spinel irradiated with 1013 Kr ions/cm2, for a value of 0.275 in the pristine samples. Moreover, a line attributed to aluminum in 5-fold coordination with oxygen is observed in irradiated spinel samples at the maximum fluence for krypton. These new aluminum environments can characterize a transition layer which could change toward an amorphous layer, increasing the electronic stopping power and/or the fluence.

Grain Growth in Nanocrystalline Metal Thin Films under In Situ Ion-Beam Irradiation

Abstract In-situ observations in a transmission electron microscope (TEM) were used to study the microstructure evolution in metal Zr, Pt, Cu, and Au nanocrystalline thin films under ion-beam irradiation. Free-standing films were prepared by sputter deposition. Samples were irradiated in-situ at the Intermediate Voltage Electron Microscope (IVEM) at Argonne National Laboratory with Ar and Kr ions to fluences in excess of 1016 ion/cm2. As a result of irradiation, grain growth was observed in all samples using Bright Field (BF) imaging in the TEM. The average grain size increased monotonically with ion fluence until it reached a saturation value. Similarly to thermal grain growth, the ion-irradiation induced grain growth curves could be best fitted with curves of the type: Dn-D0n=KΦ. The irradiations were done at temperatures ranging from 20 to 773 K. The results suggest the existence of three regimes with respect to irradiating temperature: (i) a purely thermal regime, which appears to start above the bulk coarse-grained recrystallization temperature, (ii) a thermally assisted regime where thermal diffusion and irradiation effects combine to increase the rate of grain growth relative to that resulting from either of these mechanisms alone, and (iii) an athermal regime (low-temperature regime) where irradiation can by itself cause grain growth. The transition temperature between the athermal regime and the thermally assisted regime depends on the material, but is in the range 0.14–0.22 times the melting point. The influence of the ion type was also investigated on Zr-Fe irradiated with 600 keV Kr ions versus 600 keV Ar ions.

Development of emulsion track expansion techniques for optical-microscopy-observation of low-velocity ion tracks with ranges beyond optical resolution limit

We succeeded to observe tracks of low-velocity Kr ions, having originally ranges below optical resolution, in a fine grain nuclear emulsion with an optical microscope after expanding the emulsion along the incident direction. This opens up the possibility of tracking low-velocity nuclear recoils from massive dark matter particles using optical microscope scanning systems.

Charge states of inert gas ions in lunar ilmenites

Fractionation of particles of solar corpuscular radiation significantly changes from flare to flare; therefore the average regularities derived from the contents of inert gases in lunar samples of different cosmicray exposure age are of particular importance. Simulation of the charge states of inert gas ions (Ne, Ar, Kr, and Xe) in lunar ilmenites suggests possibility of higher solar flare activity and higher hardness of the solar proton spectrum ∼1 billion years ago.

Features of sputtering of nitrides and their components

The sputtering behaviour of hexagonal or wurtzite polycrystal nitrides of boron, aluminium, and gallium was explored employing methods of molecular dynamics. The sputtering yield Y of nitrides and the average energy Ē 1 of emitted particles were studied as dependent on the mass m 1 of bombarding He, Li, B, N, Ne, Al, Ar, Ni, Ga, Kr, and Xe ions with the initial energy E 0 between 200 and 10,000 eV. Y(m 1) and Ē 1(m 1) were researched upon for preferential sputtering of nitride components at low E 0. It was revealed that the ratio between the sputtering yield of the light component and that of the heavy one depends on ion energy and mass. At E 0=200 eV and m 1=40, the ratio for BN, AlN, and GaN amounts to 1.2, 2.2, and 2.4, respectively. For nitride components, an anomalous dependence of sputtering on ion mass was found, its maximum occurring at a certain ratio m 2/m 1, where m 2 is the averagè mass of two nitride components.

Technology of Ferroelectric Thin-Film Formation with Large Coercive Field on Amorphous SiO2 by Ion-Bombardment-Assisted Sputtering and Oxygen Radical Treatment for Future Scaling Down of Ferroelectric Gate Field-Effect Transistor Memory Device

Sr2(Ta1-x,Nbx)2O7 (perovskite STN; x=0.3) is one of the most practical candidates for one-transistor-type ferroelectric memory devices, because it has a low dielectric constant. However, in the application to metal–ferroelectric–insulator–Si field-effect transistor (MFIS-FET) memory devices, the fabrication of STN on an amorphous insulator, such as SiO2, is difficult. In particular, in the case of STN, because its crystallization annealing temperature is 950 °C, the metal elements of STN and Si react with each other during crystallization annealing. As a result, perovskite STN cannot be fabricated. To overcome this problem, we have developed an ion-bombardment-assisted sputtering method. Furthermore, to obtain universal conditions for forming perovskite STN based on plasma physics, plasma parameters such as ion bombardment energy and ion flux, were measured. Perovskite STN was obtained when the ion bombardment energy was 38 eV and the normalized Kr ion flux was 78 [ions/atom]. An IrO2/STN (140 nm)/STN seed layer (10 nm)/Si device whose STN was fabricated under these plasma conditions, shows square hysteresis curves and a memory window of 1.7 V under an 8 V writing operation. This value corresponds to a coercive field of 55 kV/cm.

Low-velocity ion tracks in fine grain emulsion

We have studied low-velocity Kr ion responses of nuclear emulsions for the possibility of tracking Ag and Br recoils from galactic dark matter particles. Tracks of 680–1180 km/s Kr ions have been observed in a 40 nm-sized AgBr grain emulsion with scanning electron microscopy. The tracks have a linear energy-dependency in range, angles biased along the incident direction, and a high developed-grain number density with respect to expected electronic stopping. We find that the fine grain emulsion is sensitive enough to low-velocity heavy ions whose energy losses are mainly governed by nuclear stopping.

The influence of krypton and bismuth–krypton implantation on manganin sensitivity to temperature and hydrostatic pressure

The influence of implantation of krypton ions and the combined implantation of bismuth and krypton ions into manganin pressure sensors on their sensitivity to pressure and temperature has been investigated. Manganin pressure sensors were of the foil type, 10 μm thick, and of relatively large planar dimensions. Implanted dose of Kr was 2.5×1015 ion/cm2 with the energy of 245 MeV/ion. In the case of combined implantation, it was as high as 1016 ion/cm2 with the energy of ∼255 keV/ion for Bi ions and 1017 ion/cm2 with the energy of ∼255 keV/ion for Kr ions. Implantation of high-energy Kr ions makes the pressure sensitivity increase only ∼1%, but for the complex Kr–Bi implantation, the increase of pressure sensitivity by 25% has been observed. Modelling of the resistance properties of the sensor, representing it as a parallel connection of strongly implanted and almost not implanted parts, allowed us to estimate the increase in the pressure sensitivity of the strongly implanted part as being much higher (∼250%). High-dose implantation with Kr and Bi ions remarkably changes the temperature-resistance characteristic of manganin sensor, making it more convenient for the use in the vicinity of room temperature. The surface structure of the manganin foil after high-energy Kr ions implantation has smaller roughness.

The Abundances of Light Neutron‐Capture Elements in Planetary Nebulae. I. Photoionization Modeling and Ionization Corrections

We have conducted a large-scale survey of 120 planetary nebulae (PNe) to search for the near-infrared emission lines [Kr III] 2.199 μm and [Se IV] 2.287 μm. The neutron (n)-capture elements Se and Kr may be enriched in a PN if its progenitor star experienced s-process nucleosynthesis and third dredge-up. In order to determine Se and Kr abundances, we have added these elements to the atomic databases of the photoionization codes Cloudy and XSTAR, which we use to derive ionization correction factors (ICFs) to account for the abundances of unobserved Se and Kr ions. However, much of the atomic data governing the ionization balance of these two elements are unknown, and have been approximated from general principles. We find that uncertainties in the atomic data can lead to errors approaching 0.3 dex in the derived Se abundances and up to 0.2-0.25 dex for Kr. To reduce the uncertainties in the Kr ionization balance stemming from the approximate atomic data, we have modeled 10 bright PNe in our sample, selected because they exhibit emission lines from multiple Kr ions in their optical and near-infrared spectra. We have empirically adjusted the uncertain Kr atomic data until the observed line intensities of the various Kr ions are adequately reproduced by our models. Using the adjusted Kr atomic data, we have computed a grid of models over a wide range of physical parameters (central star temperature, nebular density, and ionization parameter) and derived formulae that can be used to compute Se and Kr ICFs. In the second paper of this series, we will apply these ICFs to our full sample of 120 PNe, which comprises the first large-scale survey of n-capture elements in PNe.

Stark mixing of ionic intermediate states in radiative recombination of channeled ions

Stark mixing of intermediate excited ionic states due to combined action of crystal lattice, polarization wake potential and collisions with electrons is considered theoretically. Calculations for radiative recombination of well-channeled Ar and Kr ions under planar channeling in Si crystal show significant influence of the mixing of [n = 2] states on formation of the X-ray spectra and angular correlation between L-REC and Kα1 photons.

The order‐disorder phase transformation in ion‐irradiated rare earth sesquioxide Dy2O3

AbstractIn this report, we examine an irradiation‐induced order‐disorder phase transformation in polycrystalline pellets of the rare earth sesquioxide Dy2O3 using grazing incidence X‐ray diffraction (GIXRD) and transmission electron microscopy (TEM). This sesquioxide is characterized by a cubic C ‐type rare earth structure known as bixbyite. Samples were irradiated with heavy ion Kr++ (300 keV) at cryogenic temperature. GIXRD and cross‐sectional TEM observations reveal that the ordered body‐centered cubic bixbyite structure transforms to a disordered (anion deficient) fluorite structure in this irradiated sesquioxide. This observation is consistent with a radiation‐induced disordering process in which the oxygen superlattice associated with the bixbyite structure is destroyed and the material adopts an anion disordered fluorite structure as evidenced by the disappearance of characteristic GIXRD diffraction peaks resulting from ordering of the oxygen superlattice, and similar electron diffraction pattern features. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Dielectronic recombination data for dynamic finite-density plasmas

We report on total and final-state resolved partial dielectronic recombination data for helium-like ions forming lithium-like ions. The calculations consider ions of Li, Be, B, C, N, O, F, Ne, Na, Mg, Al, Si, P, S, Cl, Ar, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Zn, Kr, Mo, and Xe. The results are discussed and compared with available experimental data and with previous calculations. Our archived datasets include both total and level-specific DR rate coefficients. The total ion rate coefficients are provided both in tabulated form and as analytical fits for easy implementation into spectral modelling codes. We employ the level specific rate coefficients in constructing detailed spectral models of Li-like ions including the combined effects of collisional excitation and recombination. The results from these models are compared with the those pure collisional excitation models under typical conditions of low density plasmas. This work is part of an assembly of a dielectronic recombination database for modelling of finite-density plasmas.

Study on irradiation-induced magnetic transition in FeRh alloys by means of Fe K-edge XMCD spectroscopy

We have studied the effects of swift heavy ion irradiation on the magnetic properties of Fe–50at.%Rh intermetallic compound by using Fe K-edge X-ray magnetic circular dichroism (XMCD) at 20K. For an unirradiated specimen, no signal of XMCD spectrum has been observed because Fe–50at.%Rh intermetallic compound is intrinsically anti-ferromagnetic below room temperature. For the specimens irradiated with 120–200MeV Ni, Kr, Xe or Au ions, we have found XMCD spectra which are characterized by a dispersion-type profile with a positive peak and a negative peak near Fe K-edge. The intensity of XMCD spectra remarkably depends on ion-fluence and ion-mass. The experimental result implies that the ferromagnetic state is induced by the swift heavy ion irradiation. The change in magnetic state of Fe element is discussed in terms of energy deposition through the elastic and electronic processes.

Structure changes in InP and GaAs crystals double irradiated with electrons and swift heavy ions

We have studied InP and GaAs crystal structure changes under the influence of swift Kr and Bi ions irradiation by means of scanning electron microscopy, atomic force microscopy (AFM) and selective chemical etching. The previous disordering of samples by electron irradiation is shown to be leading to macrodefect formation in the form of cracks and breaks at the depths near the ion end-of-range and on the crystal surface. A possible explanation of the observed effects is proposed.

Alignment dynamics in a laser-produced plasma

We observe the time evolution of ground-state ion alignment in a laser-produced plasma. Krypton ions produced in a strong, linearly polarized optical laser field $({10}^{14}--{10}^{15}\phantom{\rule{0.3em}{0ex}}\mathrm{W}∕{\mathrm{cm}}^{2})$ are aligned along the field polarization axis. Using microfocused, tunable x rays from Argonne's Advanced Photon Source, we measure orbital alignment as a function of time. For plasma densities of the order of ${10}^{14}\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3}$, the alignment decays within a few nanoseconds. A quantitative model explains the decay in terms of electron-ion collisions in the plasma. By applying an external magnetic field, we are able to suppress the disalignment and induce coherent spin precession of the Kr ions, thus providing an in situ monitor of magnetic fields in a plasma.

The impact of high-dose implantation into manganin on its thermo-resistance properties under high pressure

Using high-dose implantation into manganin of 253 MeV Kr ions (a surface dose of 2.5×10 15 ion/cm 2), as well as 250 keV Bi ions (a surface dose of 10 17 ion/cm 2) and 250 keV Kr ions (a surface dose of 10 16 ion/cm 2), the pressure and temperature sensitivities of manganin foil have been investigated. It was found that the pressure sensitivity of manganin increased ( α=2.45×10 −5 MPa −1 before implantation and α imp=4.60×10 −5 MPa −1 after complex implantation with 250 keV of Bi and Kr ions, the accuracy of estimation does not exceed 0.01×10 −5 MPa −1) and its temperature sensitivity remained appreciably reduced.

Magnetic and structural behavior of FeCo/Cu multilayers submitted to Kr irradiation

We have studied the effects of ion irradiation on the structural and magnetic properties of FeCo/Cu multilayers. The films were irradiated at room temperature with 600keV Kr ions, with fluences ranging from 1 to 5×1015ions/cm2. X-ray absorption spectroscopy (XAS) was used to characterize the structural changes around Fe and Co atoms. The XAS data have shown a phase transformation of FeCo alloy from bcc for the as-deposited sample to fcc after irradiation. The structural effects induced by irradiation changed the saturation magnetization (MS), the coercive field (HC) and the magnetic particle size. The interplay between structural and magnetic effects indicates that some degree of mixing took place even being the elements immiscible.

Interface mixing of Fe/Si bilayers by noble-gas ions: Are there effects of the ionic charge state?

Charge-state equilibration of ions moving in matter occurs within femtoseconds and when penetrating nanometer depths. Ion-beam mixing in bilayers, tens of nm thick, should therefore not depend on the charge state of the projectiles. As the experimental situation for metal/silicon bilayers irradiated with noble-gas ions of different charge-states is ambiguous, we studied interface mixing of Fe/Si(100) bilayers, induced by 100keV 40Ar, 180keV 86Kr and 250keV 132Xe ions, either singly and multiply charged (Ar8+, Kr11+, Xe17+). No significant influence of the ionic charge-state was established for Kr and Xe ions; a slightly higher mixing rate was found for Ar8+ than for Ar1+ irradiation.