MeV Argon Research Articles

Permanent magnet ECR ion source and LEBT dipole for single-ended heavy ion ToF-ERDA facility

We present the status of the ion source and low energy beam transport prototyping for a single-ended heavy ion time-of-flight elastic recoil detection analysis equipment. The environmentally friendly concept is based on a permanent magnet ECR ion source and dipole magnet on a 500 kV platform without SF6 insulation, producing high charge state noble gas ion beams, e.g. 3–6 MeV argon. The ion fluxes of Ar6+–Ar12+ achieved with the CUBE-ECRIS permanent magnet minimum-B quadrupole ion source exceed 1-10 particle nA required for the low energy ToF-ERDA application. The CUBE-ECRIS can produce over 1 particle nA krypton and xenon beams up to charge states Kr19+ and Xe24+, which enables extending the scope of the ToF-ERDA application. The integration of an adjustable-field permanent magnet dipole into the CUBE-ECRIS test stand at the JYFL accelerator laboratory is described briefly.

Microstructural evolution of silicon carbide fiber under argon ion irradiation at room temperature

In current work, irradiation-induced microstructural evolution of the Cansas 3303 SiC fiber was investigated. This fiber was irradiated by 1.8 MeV argon ions at room temperature in the Shanghai Institute of Applied Physics, Chinese Academy of Sciences. The ion fluences were 5 × 1014, 1 × 1015, 2.5 × 1015 and 5 × 1015 ions/cm2 corresponding to the maximum doses of 0.27, 0.54, 1.35 and 2.70 displacements per atom (dpa), respectively. Irradiation effects were characterized by using micro-Raman spectroscopy and transmission electron microscopy. The results showed that the Cansas 3303 fiber consists of nanocrystalline SiC grains, carbon packets and carbon ribbons. Irradiation-induced amorphization accompanied with the decrease of SiC grain size was observed in the fiber with the increase of ion fluences. However, SiC grains still remained in this fiber up to the dose of 2.70 dpa. Besides, the reduction of the quantity and size in carbon packets and the annihilation of carbon ribbons in this fiber were also detected.

Disorder-induced crossover of Mott insulator to weak Anderson localized regime in an argon-irradiated NdNiO3 film

We show that an introduction of disorder in a controlled way using 1 MeV argon (Ar) ion irradiation, suppresses the correlation driven metal-insulator transition (MIT) in $\mathrm{Nd}\mathrm{Ni}{\mathrm{O}}_{3}$ films. The films make a crossover to a heavily disordered conductor governed by weak localization (WL) and at even higher disorder, an Anderson localized state. The disorder (atomic displacement up to 2% of the total atoms) in the $\mathrm{Nd}\mathrm{Ni}{\mathrm{O}}_{3}$ films was created using 1 MeV ${\mathrm{Ar}}^{4+}$ ion irradiation. We show that the pristine films of $\mathrm{Nd}\mathrm{Ni}{\mathrm{O}}_{3}$ exhibit an MIT with the conduction process being governed by variable range hopping (VRH). For disorder up to 1% of the displaced atoms or lower, the insulating state arising from a gap in the density of states (DOS) at the Fermi level (${E}_{F}$) as in a Mott insulator is suppressed and the conduction in the film shows a WL behavior with finite conductivity at temperature $T\ensuremath{\rightarrow}0$. This behavior is expected in a disordered conductor that does not have a gap in DOS at ${E}_{F}$. At higher fluences the conductivity reduces substantially but the electrical conduction shows a power-law temperature dependence with a small but finite zero temperature conductivity $\ensuremath{\sigma}(T=0)$ which is expected in a solid with electrons that are Anderson localized. A similar experiment was performed on the La substituted $\mathrm{Nd}\mathrm{Ni}{\mathrm{O}}_{3}$ films (${\text{Nd}}_{1\ensuremath{-}x}{\text{La}}_{x}{\text{NiO}}_{3}$) with $x=0.3$ that are grown in the same way. La substitution in $\mathrm{Nd}\mathrm{Ni}{\mathrm{O}}_{3}$ suppresses the temperature driven transition and leads to a metallic state with critical composition at $x\ensuremath{\approx}0.3$. The pristine as well as films irradiated with lowest fluence shows metallic or marginally metallic behavior grown on $\mathrm{La}\mathrm{Al}{\mathrm{O}}_{3}$ and $\mathrm{Sr}\mathrm{Ti}{\mathrm{O}}_{3}$ substrates, respectively. However, at higher fluences they too exhibit a convergence in electronic transport and $\ensuremath{\sigma}$ shows a power-law temperature dependence at low $T$ with $\ensuremath{\sigma}(T=0)\ensuremath{\ne}0$. Evidence of suppression of correlated behavior can also be seen in the irradiated films where the non-Gaussian nature of resistance fluctuation at $T\ensuremath{\approx}{T}_{\text{MI}}$, a signature of correlated electron systems, is suppressed on irradiation that leads to collapse of the MIT. Evidence for progressing disordering of the films on irradiation were observed in Raman spectroscopy as well as x-ray studies that show the basic integrity of the ${\text{NiO}}_{6}$ octahedra is preserved and the structure retains its crystallinity.

Effect of noble-gas bubbles on deuterium trapping behavior in argon pre-implanted stainless steel

Ion implantation technique and nuclear reaction analysis were used to study the trapping behavior of deuterium by radiation defects in 316 austenitic stainless steel. Defect structure with a different ratio of displacement per atom (dpa) to argon gaseous impurity along with a depth has been formed by pre-irradiation of SS316 with 1.4 MeV argon ions. The deuterium migration between layers containing various defect types served as an indicator of traps strength. Computational evaluation of deuterium trapping process within the framework of the diffusion-trapping model has shown that gas-bubbles associated traps turn out to be a strongest deuterium traps with a binding energy of 0.74 eV. Other irradiation-induced defect types have a weaker effect on deuterium retention in austenitic steel. Experimental observations and calculation results are discussed with respect to the possibility of molecular hydrogen formation in radiation-induced nanovoids under operating conditions of water-cooled reactor internals.

Irradiation resistance of chromium coatings for ATFC in the temperature range 300–550°C

Within the accident tolerant fuel cladding (ATFC) concept, chromium coatings appear to be promising for protecting zirconium alloys from high temperature oxidation. The effects of high energy heavy ion irradiation in the temperature range of 300–550°C on the structure of chromium coatings deposited on Zr-based (E110) alloy substrate by the cathodic arc evaporation method were studied. Isotropic growth of the grain size in chromium coatings from the initial 250 nm to 476 nm at 550°C is caused by irradiation with 1.4 MeV argon ions to the dose of 25 displacements per atom (dpa). Maximum swelling up to 1.6 % was observed under the irradiation temperature of 500°C.

Low energy argon ion irradiation effect on magnetic behavior of polycrystalline Cu substituted ZnO

Zn1-xCuxO (0 ≤ x ≤ 1) polycrystalline samples were prepared by solid state reaction route and then irradiated with 1.2 MeV argon ions at a fluence value of 1.1 × 1016 ions/cm2. The samples were characterized by X-ray diffraction, Raman spectroscopy and VSM measurements. The X-ray diffraction analysis confirms that the structural properties of Zn1-xCuxO films do not change substantially with ion beam irradiation. However, Raman studies clearly show the lattice distortion and the presence of point defects. All the samples exhibit room temperature ferromagnetic behavior. The saturation magnetization value decreases with increasing Cu concentration due to the enhancement of diamagnetic contribution and the improvement of amorphous nature of the samples.

Irradiation resistance of vacuum arc chromium coatings for zirconium alloy fuel claddings

Effects of high-energy heavy ion irradiation on the structure of chromium coatings, which were deposited by the cathodic arc evaporation method on the Zr-based alloy (E110) substrate, have been studied. Within the framework of the accident-tolerant fuel claddings (ATFC) concept, chromium coatings seem to be promising for protection of zirconium alloys from oxidation. The radiation resistance of Cr deposited coatings was investigated through the study of void swelling after irradiation with 1.4 MeV argon ions at 400 °C to doses of 5, 15 and 25 dpa. The irradiation of chromium coatings causes the isotropic growth of grain size from initial 250 nm up to 295 nm, and also, the swelling up to 0.66% under irradiation dose of 25 dpa. It can be concluded that chromium coatings have a high resistance to irradiation and are a good candidate as a protection of zirconium alloys fuel claddings in the frame of the ATFC philosophy.

(Invited) Welding of Nickel Nanowires By Ions Beam Irradiation: From Small to Large Scale

In order to replace conventional transparent conducting electrodes, metal nanowires (MNWs) networks have long been act as promising contenders due to their high mechanical flexibility. However, nanowire-nanowire contact resistance is main technical obstruction in terms of improvement in their performance. To reduce nanowire-nanowire contact resistance, welding of nanowires (NWs) is essential. In this work, MeV proton and argon ions beam irradiation induced nanoscale welding technique to fabricate X-, Y-, II- and T-shaped molecular junctions between nickel nanowires (Ni-NWs) is presented. Ni-NWs are irradiated by 2.75 MeV proton ions and 3.5 MeV argon ions at doses 1x1016ions/cm2 and 5x1015 respectively while temperature is kept constant. Transmission electron microscopy (TEM), scanning electron microscopy (SEM) and x-ray diffraction (XRD) results reveal that Ni-NWs are welded without losing stability in crystal structures of NWs. Afterward, a two-dimensional large scale random network of Ni-NWs is fabricated by 3 MeV proton ions beam irradiation induced nanoscale welding of Ni-NWs at crossing positions. Proton ion beam induced large scale network fabrication is confirmed by TEM and SEM techniques. Moreover, these networks are characterized optically using UV-VIS spectroscopy. It is observed that at a beam fluence of 5x1015 ions/cm2, perfect molecular junctions between Ni-NWs in X-, II-, and V-shapes are achieved and a large scale welded network of Ni-NWs is obtained without distorting the morphology of NWs. Moreover, structure of Ni-NWs remains stable under 3MeV proton ions beam irradiation and networks are found to be optically transparent. The results exhibit that fabrication of Ni-NWs network precede through three steps: i- High energy ions beam irradiation induced heat spikes lead to locally heat and fuse Ni-NWs, ii- Formation of molecular junctions on small scale, iii- Formation of large scale network Ions beam irradiation induced welding of Ni-NWs can improve performance of NWs networks by reducing contact resistance between NWs for application as transparent conducting electrodes. These high quality welded MNWs networks may potentially be applied as transparent conducting electrodes in optoelectronic devices.

Effect of 1.2 MeV argon ions irradiation on magnetic properties of ZnO

Room temperature ferromagnetism in 1.2MeV argon ions irradiated polycrystalline ZnO has been observed. The magnetic contribution in form of saturation magnetization is higher in sample irradiated with ion fluence of 1×1015 ions/cm2. However, annealing of the defects at higher fluences of 5×1015 ions/cm2 reduce the magnetic contribution in comparison to the magnetic contribution of the lower fluences. The X-ray diffraction reveals that the degree of crystallinity decreases with the increase of ion fluences upto 1×1015 ions/cm2 and further it increases at a fluence of 5×1015 ions/cm2. The inhomogeneous arrangement of grains and changes in their sizes with increasing ion fluences decrease the magnetic ordering of the system. The electron probe microstructure analyses and micro-Raman spectra of irradiated samples show in-homogeneity in zinc and oxygen ratio which is one of the causes to show ferromagnetism.

Titanium and zirconium oxidation under argon irradiation in the low MeV range

ABSTRACTWe studied the irradiation effects on Ti and Zr surfaces in slightly oxidizing environment (rarefied dry air, 500°C) using multi-charged argon ions in the low MeV range (1 – 9 MeV) to the aim of determining the respective role of the electronic and nuclear stopping power in the operating oxidation process under irradiation. We have shown that ballistic collisions contribute significantly to the enhanced Ti and Zr oxidation under MeV argon bombardment. We have also shown that the projectile energy plays a significant role in the overall process.A significant oxide film thickening is visible on titanium under irradiation, taking the form of a well-defined oxidation peak between 1 and 4 MeV, as a result of the Nuclear Backscattering Spectroscopy and Spectroscopic Ellipsometry studies.A significant oxide film thickening is also visible on zirconium under same irradiation conditions, at 4 and 9 MeV, as a result of the NBS study. Work is in progress in order to determine how the modified oxidation process depends in this case on the projectile energy.

Effect of ion irradiation on optoelectronic properties of Ba0.12Sr0.88SO4: Eu phosphor

Nanocrystalline Ba0.12Sr0.88SO4 phosphor doped with Eu at 0.1mol% optimum concentration was prepared by the chemical co-precipitation method. X-ray diffraction study of the prepared sample suggests the orthorhombic structure with an average grain size of 62nm. The band gap was found to be 4.3eV. The samples were irradiated with 1.2MeV argon ions at fluences varying between 1011 and 1015ions/cm2, i.e. in the dose range of 59kGy to 590MGy. A prominent photoluminescence (PL) emission peak is seen around 376nm due to transition from an excited state 4f65d to 8S7/2 state of Eu2+ ions. The broadening of bands in FTIR spectrum at 1110, 990, 643 and 617cm−1 is an evidence of the generation of SO4−, SO3−, SO2−, O−, etc. radicals after ion irradiation. The effect of ion irradiation on luminescence properties was studied.

Radiation damage induced at the surface of titanium by argon ions of a few MeV

Oxide films thermally grown on titanium in a weakly oxidizing environment (5 × 10 −3 Pa of dry air) under irradiation with 2, 4 and 9 MeV argon have been studied. The AFM study reveals a cratering effect of 2, 4 and 9 MeV argon and a significant surface roughening effect of 2 MeV argon, both effects being largely unexpected in this energy range. The XPS analysis shows that the TiO 2 stoichiometry of the superficial oxide film is fairly well maintained under argon irradiation. The Spectroscopic Ellipsometry analysis reveals an oxide film thickness multiplied by a factor of three under irradiation with 2 MeV argon by comparison with 9 MeV argon, the irradiation effect on oxide growth remaining very limited for 4 or 9 MeV argon. The possible role of the electronic but most certainly of the nuclear energy losses on the surface damage mechanism are discussed. It is suggested that the oxidizing environment is necessary to freeze the instantaneous surface damage and permits the post-mortem observation.

Effect of ion irradiation on the thermoluminescence properties of K2Ca2(SO4)3 phosphor

This paper presents the thermoluminescence (TL) studies of ion-irradiated potassium–calcium mixed sulfate phosphor. The sample was prepared by the solid-state diffusion method. The X-ray diffraction study of the prepared sample suggests an orthorhombic structure with an average particle size of 0.16 μ m. The samples were irradiated with 1.2 MeV argon ions at fluences varying between 1011 and 1015 ions/cm2. The argon ions penetrate to a depth of 1.93 μ m and lose their energy mainly via electronic stopping. Due to ion irradiation, a large number of defects such as oxygen vacancies, radicals and color centers are formed in the sample. TL glow curves were recorded for each of the ion fluences. A linear increase in the intensity of TL glow peaks was found with an increase in the ion dose from 72 kGy to 720 MGy. The kinetic parameters associated with the prominent glow peaks were calculated using glow curve deconvolution, different glow curve shapes and sample heating rate methods.

Study of the zirconium oxidation under heavy ion irradiation

The objective of the present paper is to put in evidence the influence of damages due to the collision cascades which take place at the end of the heavy ion micrometer range, on the zirconium surface oxidation.A comparison between two zirconium oxidation experiments under heavy ion irradiation performed in the same temperature and pressure conditions is presented. In the first experiment, a 6μm thick zirconium foil is irradiated with a 50MeV 129Xe beam which stops in the Zr foil. In the second one, a 2μm thick zirconium foil is crossed by the whole fission fragment distribution emitted in the 235U fission. In order to explain the unexpected increase of the oxidation rate observed in the first case, MeV argon irradiation experiments have been performed at IPNL. Results show that collision cascades created in the Zr foil, far from the surface, increase significantly the Zr oxidation.

Analysis of the projectile track charging by H + secondary ion velocity distribution measurements

Secondary ions, emitted from LiF, Al (covered with layers of Al 2O 3) and Au bombarded by a MeV argon (25 keV/u) beam, are analyzed by a XY-TOF detection system. This new method allows, for each emitted ion, the simultaneous measurement of its time-of flight (TOF) and its impact coordinates (XY) on the detector surface, after acceleration by a homogenous electric field. Angular distributions and initial velocities for atomic H + secondary ions are determined as a function of the projectile impact angle θ p (37° up to 78°, with respect to the surface normal) and the electrical surface target properties. Emission of low velocity H + ions ( v 0<30 km/s) occurs preferentially close to the line of incidence of the projectile. Their initial velocity distribution depends clearly on the target electrical conductivity. At constant θ p, the maximum of the velocity distribution, v 0 max, is found to be 26.5, 27.9 and 32.5 km/s for Au, Al and LiF targets, respectively. For Au target, no clear dependence on the impact angle θ p was found. However, increasing θ p from 37° to 78° v 0 max shifts from 27.9 to 30 km/s for Al and 32.5–35.5 km/s for LiF. This shift is explained by a transient positive charging up of the nuclear track and is an indication of the track potential decay. The dependence of v 0 on θ p is explained by the variation of the length of the track inside the insulator layer, once neutralization time is assumed to be dependent on the electron current inside the track of the insulator layers from a conducting substrate.

Molecular secondary ion emission from binary collisions

Secondary ions, produced by neutral 1.0 MeV argon beam impact on Al 2O 3 and LiF thin films, are analyzed by a XY-TOF detection system. Angular distributions and initial velocities are simultaneously determined for ionized species originating from the bulk or from the adsorbate layer. The employed XY-TOF spectrometer was designed to measure accurately radial and axial velocity measurements of positive and negative secondary ions with mass <50 u and desorbed from the surface material in the 100-eV energy range. The analysis shows that high velocity diatomic and triatomic molecules can be also emitted in a process similar to the one involving atomic secondary ions, in which energetic binary collisions causes emission perpendicularly to the beam direction. The initial velocity distribution analysis is shown to be helpful in the identification of chemical species lying either on surface or in the bulk material.

Radioluminescence of alumina during proton and heavy ion irradiation

Radioluminescence (RL) of sapphire and polycrystalline alumina (p-Al 2O 3) under 8 MeV proton (flux 2 × 10 12 proton/cm 2s), 150 MeV argon (4.3 × 10 8 ion/cm 2 s) and 253 MeV krypton (4.3 × 10 8 ion/cm 2 s) ion irradiation has been measured in the UV and visible ranges. The processes causing the changes of RL of sapphire with a dose differ from those of p-Al 2O 3. Radiation-induced annealing of oxygen vacancies in p-Al 2O 3 occurs with decreasing F +-band. Inhomogeneous distribution of traps associated with grain boundaries causes electrical charging of microscopic regions in p-Al 2O 3 and an increase of F-band of RL. The accumulation of charge carriers at traps increases excitation probability of F +-center and results in growth of F +-band of sapphire. A ratio of initial to saturation intensity of the F +-band increases with increasing the linear energy loss of incident particles.

Measurement of stopping power of 240 MeV argon ions in partially ionized helium discharge plasma

An energy loss of 240 MeV argon ions in a Z-pinch helium plasma has been for the first time observed throughout the entire pinching process. Standard Stark broadening analysis gives an electron density ranging from 4 to 6 × 1017 cm−3 during the pinch. To deduce stopping power from the energy loss, the target thickness of the helium plasma has been evaluated assuming the mean charge of helium based on thermal equilibrium. The observed electron density and the mean charge of helium give a target thickness of 30 ± 3 μg cm−2 from 1 μs to 1.8 μs after the discharge ignition. The measured stopping power exceeds a tabulated value for cold helium gas by a factor of 2 to 3 around the time of the first pinch. The experimental stopping power is compared with theoretical values calculated using an equation of stopping power for a partially ionized plasma.

Defect production in silicon irradiated with 750 MeV Ar ions

Specimens of about 320 μm thick and 〈1 1 1〉 oriented single crystalline silicon are irradiated with 750 MeV argon ions at room temperature to dose levels of 9×10 13 and 4.3×10 14 Ar/cm 2. Positron lifetime measurements, fourier transform infrared absorption (FT–IR) and electron paramagnetic resonance (EPR) techniques are applied to investigate the specimens. It is found that divacancies of neutral charge state are the main vacancy clusters induced by the irradiations. No amorphous phase is detected up to the highest dose. In the area where electronic processes are dominating a divacancy concentration around 7×10 16/cm 3 is found which shows little change with dose. At the projected range where nuclear process is dominating the divacancy concentration increases dramatically with increasing of dose. It is argued that energy deposition through electronic processes can only induce limited damage in silicon and high electronic stopping power suppresses the formation of amorphous zones.

Kinetics of impurity gettering on buried defects created by MeV argon implantation

High energy argon ion implantation was used to form, in intentionally gold or platinum contamined silicon samples, a buried layer of efficient gettering sinks with low damage creation close to the surface. In any case, the implantation temperature was chosen to avoid partial or complete amorphization. Both nature and long term stability of these centers have been determined by Transmission Electron Microscopy (TEM) and channeling measurements. The kinetics of gold accumulation on these sinks was measured using high sensitivity Rutherford Backscattering (RBS) analysis as a function of implantation dose and annealing temperature. The effect of initial metallic contamination concentration was also investigated. The results are discussed using a model which takes into account a trapping-detrapping reaction and an impurity dependent annealing behaviour of the gettering sites.