Effect Of Heavy Ion Irradiation Research Articles

Swift heavy ion irradiation of water ice from MeV to GeV energies

Context. Cosmic ray ion irradiation affects the chemical composition of and triggers physical changes in interstellar ice mantles in space. One of the primary structural changes induced is the loss of porosity, and the mantles evolve toward a more compact amorphous state. Previously, ice compaction was monitored at low to moderate ion energies. The existence of a compaction threshold in stopping power has been suggested.Aims. In this article we experimentally study the effect of heavy ion irradiation at energies closer to true cosmic rays. This minimises extrapolation and allows a regime where electronic interaction always dominates to be explored, providing the ice compaction cross section over a wide range of electronic stopping power.Methods. High-energy ion irradiations provided by the GANIL accelerator, from the MeV up to the GeV range, are combined with in-situ infrared spectroscopy monitoring of ice mantles. We follow the IR spectral evolution of the ice as a function of increasing fluence (induced compaction of the initial microporous amorphous ice into a more compact amorphous phase). We use the number of OH dangling bonds of the water molecule, i.e. pending OH bonds not engaged in a hydrogen bond in the initially porous ice structure as a probe of the phase transition. These high-energy experiments are combined with lower energy experiments using light ions (H, He) from other facilities in Catania, Italy, and Washington, USA.Results. We evaluated the cross section for the disappearance of OH dangling bonds as a function of electronic stopping power. A cross-section law in a large energy range that includes data from different ice deposition setups is established. The relevant phase structuring time scale for the ice network is compared to interstellar chemical time scales using an astrophysical model.Conclusions. The presence of a threshold in compaction at low stopping power suggested in some previous works seems not to be confirmed for the high-energy cosmic rays encountered in interstellar space. Ice mantle porosity or pending bonds monitored by the OH dangling bonds is removed efficiently by cosmic rays. As a consequence, this considerably reduces the specific surface area available for surface chemical reactions.

DNA-PKcs Inhibition Sensitizes Cancer Cells to Carbon-Ion Irradiation via Telomere Capping Disruption

Heavy-ion irradiation induces a higher frequency of DNA double strand breaks (DSBs) which must be properly repaired. Critical shortening of telomeres can trigger DNA damage responses such as DSBs. Telomeres are very sensitive to oxidative stress such as ionizing radiation. The DNA-dependent protein kinase catalytic subunit (DNA-PKcs) is the central component in the non-homologous end joining (NHEJ) repair complex and participates in telomere maintenance. Therefore, it is expected to enhance the cell killing effect of heavy-ion irradiation via DNA-PKcs inhibition. To test this hypothesis, cellular radiosensitivity was measured by the clonal genetic assay. DNA damage repair was relatively quantified by long PCR. Apoptosis was quantified by flow-cytometric analysis of annexin V/PI double staining, and senescence was analyzed by galactosidase activity. Telomere length was semi-quantified by real-time PCR. P53 and p21 expression was determined by western blotting. Our data demonstrated that MCF-7 and HeLa cells with DNA-PKcs inhibition were more susceptible to carbon-ion irradiation than Those without DNA-PKcs inhibition. Even though NHEJ was inhibited by the DNA-PKcs specific inhibitor, NU7026, most DNA damage induced by carbon-ion irradiation was repaired within 24 hours after irradiation in both cell lines. However, potential lethal damage repair (PLDR) could not restore cellular inactivation in DNA-PKcs inhibited cells. MCF-7 cells showed extensive senescence and accelerated telomere length reduction, while HeLa cells underwent significant apoptosis after irradiation with NU7026 incubation. In addition, both cell lines with shorter telomere were more susceptible to carbon-ion radiation. Our current data suggested that DNA-PKcs inhibition could enhance cellular sensitivity to carbon-ion radiation via disturbing its functional role in telomere end protection. The combination of DNA-PKcs inhibition and carbon-ion irradiation may be an efficient method of heavy-ion therapy.

Integrated experimental and computational approach to understand the effects of heavy ion radiation on skin homeostasis

The effects of low dose high linear energy transfer (LET) radiation on human health are of concern for space, occupational, and clinical exposures. As epidemiological data for such radiation exposures are scarce for making relevant predictions, we need to understand the mechanism of response especially in normal tissues. Our objective here is to understand the effects of heavy ion radiation on tissue homeostasis in a realistic model system. Towards this end, we exposed an in vitro three dimensional skin equivalent to low fluences of neon (Ne) ions (300 MeV u(-1)), and determined the differentiation profile as a function of time following exposure using immunohistochemistry. We found that Ne ion exposures resulted in transient increases in the tissue regions expressing the differentiation markers keratin 10, and filaggrin, and more subtle time-dependent effects on the number of basal cells in the epidermis. We analyzed the data using a mathematical model of the skin equivalent, to quantify the effect of radiation on cell proliferation and differentiation. The agent-based mathematical model for the epidermal layer treats the epidermis as a collection of heterogeneous cell types with different proliferation-differentiation properties. We obtained model parameters from the literature where available, and calibrated the unknown parameters to match the observed properties in unirradiated skin. We then used the model to rigorously examine alternate hypotheses regarding the effects of high LET radiation on the tissue. Our analysis indicates that Ne ion exposures induce rapid, but transient, changes in cell division, differentiation and proliferation. We have validated the modeling results by histology and quantitative reverse transcription polymerase chain reaction (qRT-PCR). The integrated approach presented here can be used as a general framework to understand the responses of multicellular systems, and can be adapted to other epithelial tissues.

200 MeV Ag+15 ion irradiation-induced modifications in structural, magnetic and dielectric properties of nanoparticles of Cu0.2Zn0.8Fe2O4 ferrite

The present investigation aims at studying the effect of swift heavy ion irradiation on the structural, magnetic and dielectric properties of the nanocrystalline Cu0.2Zn0.8Fe2O4 spinel ferrite. The sample was synthesised using the sol–gel technique and then irradiated with the 200 MeV Ag+15 ion beam. The Rietveld profile refinement of the X-ray diffraction patterns confirmed the cubic spinel structure of samples. The spherical morphology revealed through transmission electron microscopy images was consistent with the crystalline diameter. The overall magnetic behaviour pointed towards superparamagnetic relaxation at room temperature along with the significant increase in saturation magnetisation, coercivity and blocking temperature after irradiation. This could be attributed to the slight increase in the particle size and ion-induced modifications on the surface states of the nanoparticles. The enhancement in dielectric constant and loss tangent after irradiation could be attributed to the available Fe+2 ↔ Fe+3 and/or Zn+2 ↔ Zn+3 ion polarisation at the octahedral site, especially on grain boundaries of the sample.

Effect of swift heavy ion irradiation on copper/polymethyl methacrylate nanocomposites

In this study, composite films were prepared by incorporating the copper nanoparticles in the insulating polymethyl methacrylate (PMMA) polymer matrix by the solution casting method. These films were irradiated with 120 MeV Si10+ ions at a fluence of 1×1012 ions/cm2. The radiation-induced changes in dielectric, structural and thermal properties of PMMA/Cu nanocomposites were studied using the impedance/gain phase-analyzer, X-ray diffraction (XRD), Fourier transform infra red (FTIR) spectroscopy and differential scanning calorimeter (DSC) techniques. The dielectric properties were observed to enhance with increase in metal nanoparticles’ concentration as well as with irradiation fluence. This may be due to the metal/polymer bonding and conversion of the polymeric structure into the hydrogen-depleted carbon network. Crystallite size and crystallinity of pristine and irradiated samples are observed to increase after irradiation as revealed from the XRD analysis. High-energy ion beam irradiation of the semicrystalline polymer nanocomposite changes its T g behavior as observed from the DSC analysis which is corroborated with XRD results. This might be attributed to the rupture of some polymeric bonds, which is also corroborated with the FTIR spectroscopic analysis.

Effect of swift heavy ion irradiation on lead sulfide quantum dots embedded in polyvinyl alcohol

The present study compares structural and optical modifications of lead sulfide (PbS) quantum dots under swift heavy ion (SHI) irradiation. PbS quantum dots are prepared following an inexpensive chemical route using polyvinyl alcohol as the dielectric host matrix. SHI irradiation of the samples is carried out with 100 MeV Si7+ ion beam with fluences in the range from 1×1011 to 3×1013 ions cm−2 and their structural and optical properties, before and after irradiation, are compared by X-ray diffraction (XRD), photoluminescence (PL) and UV–Vis spectroscopy. The structural parameters of PbS quantum dots are studied by X-ray line profile analysis using the Williamson–Hall plot. The values of average crystallite sizes are found to vary from 8 to 18 nm. XRD studies confirmed the formation of the cubic nanocrystalline PbS. Improvement of crystalline quality for lower fluences is exhibited by an increase in the X-ray intensities of the films. The UV–Vis absorption spectra reveal blue shift relative to the bulk material. Size enhancement of PbS quantum dots after irradiation has been indicated in XRD line profiles of the samples which has also been supported by optical absorption spectra. PL studies of all the samples are carried out with excitation wavelength 350 nm. A broad PL emission with peak centered at 473 nm is observed in pristine as well as all the irradiated samples. PL study also shows that PL intensity increases with ion fluences.

In situ RBS measurements for the effect of swift heavy ion irradiation on metal–insulator interfaces

We have studied the effect of 200MeV Xe ion irradiation on Bi–Al2O3 and Au–Al2O3 interfaces by means of in situ Rutherford backscattering spectrometry (RBS). For the Bi–Al2O3 interface, we could observe a systematic change in RBS spectrum as a function of Xe ion fluence or the irradiation time. On the other hand, for Au–Al2O3 system, we could not observe any change in RBS spectrum. The experimental result confirmed our previous result that atomic mixing at Bi–Al2O3 interface surely occurs by the Xe ion irradiation. We analyzed the RBS spectra by the simulation software SIMNRA, and discussed the Bi–Al2O3 mixing quantitatively. From the irradiation time dependence of the mixing layer thickness, we estimated the effective diffusion constant for the atomic mixing at Bi–Al2O3 interface. Its value corresponds to the self-diffusion near the melting temperature of Al2O3. The result implies that Bi and Al2O3 are in molten forms during the ion irradiation, resulting in the atomic mixing at Bi–Al2O3 interface.

Effects of energetic heavy ion irradiation on hardness of Al–Mg–Si alloys

Al–Mg–Si alloys were irradiated with 5.4MeV Al ions, 7.3MeV Fe ions, 10MeV I ions, and 16MeV Au ions at room temperature and the Vickers microhardness was measured. The hardness of Al–Mg–Si alloys increases with increasing the ion fluence. In a viewpoint of ion fluence, hardness change of the Al alloys is different by the kind of irradiating ions. But, in a viewpoint of the density of elastically deposited energy, the effect of the four kinds of them on hardness is almost the same. This result means that the effect of irradiation on hardness of Al–Mg–Si alloys is dominated by the elastically deposited energy. The microstructure of the ion-irradiated specimens were investigated by means of three-dimensional atom probe (3DAP). The experimental result was compared with the microstructure and the hardness for thermally aged specimens. We also discuss the difference in ion-irradiation induced change in hardness between Al–Mg–Si alloys and Al–Cu–Mg alloys (duralumin).

Development of dual-beam system using an electrostatic accelerator for in-situ observation of swift heavy ion irradiation effects on materials

We have developed the dual beam system which accelerates two kinds of ion beams simultaneously especially for real-time ion beam analysis. We have also developed the alternating beam system which can efficiently change beam species in a short time in order to realize efficient ion beam analysis in a limited beam time. The acceleration of the dual beam is performed by the 20UR Pelletron™ tandem accelerator in which an ECR ion source is mounted at the high voltage terminal [1,2]. The multi-charged ions of two or more elements can be simultaneously generated from the ECR ion source, so dual-beam irradiation is achieved by accelerating ions with the same charge to mass ratio (for example, 132Xe11+ and 12C+). It enables us to make a real-time beam analysis such as Rutherford Back Scattering (RBS) method, while a target is irradiated with swift heavy ions. For the quick change of the accelerating ion beam, the program of automatic setting of the optical parameter of the accelerator has been developed. The switchover time for changing the ion beam is about 5min. These developments have been applied to the study on the ion beam mixing caused by high-density electronic excitation induced by swift heavy ions.

Magnetic and topographical modifications of amorphous Co–Fe thin films induced by high energy Ag7+ ion irradiation

We have investigated the effects of swift heavy ion irradiation on thermally evaporated 44nm thick, amorphous Co77Fe23 thin films on silicon substrates using 100MeV Ag7+ ions fluences of 1×1011ions/cm2, 1×1012ions/cm2, 1×1013ions/cm2, and 3×1013ions/cm2. The structural modifications upon swift heavy irradiation were investigated using glancing angle X-ray diffraction. The surface morphological evolution of thin film with irradiation was studied using Atomic Force Microscopy. Power spectral density analysis was used to correlate the roughness variation with structural modifications investigated using X-ray diffraction. Magnetic measurements were carried out using vibrating sample magnetometry and the observed variation in coercivity of the irradiated films is explained on the basis of stress relaxation. Magnetic force microscopy images are subjected to analysis using the scanning probe image processor software. These results are in agreement with the results obtained using vibrating sample magnetometry. The magnetic and structural properties are correlated.

Effect of swift heavy ion irradiation on the short range order in novel electrodeposited ternary amorphous alloys

The effect of swift heavy ion irradiation in novel electrodeposited ternary amorphous alloys was studied by 57Fe and 119Sn conversion electron Mössbauer spectroscopy. Irradiation of Sn3Co3Fe with 246MeV Kr ions induces partial segregation and rearrangement of the constituent elements from the amorphous state toward an ordered state. The Sn3Ni3Fe irradiated with 600MeV Xe ions exhibits transformation from the as-deposited amorphous toward a slightly more disordered state due to the swift heavy ion irradiation.

Influence of Swift Heavy Ion (Si<sup>+8</sup>) Irradiation on Super-Paramagnetic Mn<sub>0.5</sub>Zn<sub>0.5</sub>Fe<sub>2</sub>O<sub>4</sub> Nanoparticles Having Different Sizes

We report the Swift Heavy Ion (SHI) irradiation effect on structural and magnetic properties of Mn0.5Zn0.5Fe2O4ferrite nanoparticles. The irradiation experiment has been carried out on three different sized, i.e. 63, 82 and 126 Å, Mn0.5Zn0.5Fe2O4particles with 100 MeV Si+8ions to a fluence 5 × 1013ions/cm2using the 15UD Tandem accelerator. The XRD measurement reveals that the basic single phase spinel structure remains unaltered after SHI irradiation; however, the lattice parameters and particle size decrease on SHI irradiation. The magnetization measurement carried out at 300 K indicates that all the particles are super-paramagnetic at room temperature, but the applied magnetic field of 70 kOe is insufficient to saturate the system. DC and AC magnetization measurements indicate that on irradiation, the sample with an intermediate size is affected more than the other two.

Modifications induced in the structural and optical properties of bismuth sodium borosilicate glass thin films by 120 MeV Ag7+ ions

The composition of the glass is Bi2O3 (20%)–Na2O (15%)–B2O3 (50%)–SiO2 (15%) was prepared by conventional melt quench method. To study the effect of heavy ion irradiation on the glass network and structural units, thin films of the glass have been prepared by electron beam gun evaporation. The prepared films are irradiated using 120MeV Ag7+ ions in the fluence range of 1×1012–3×1013ionscm−2. The optical and structural properties were investigated using UV–visible absorption spectroscopy and Fourier Transform Infrared (FTIR) spectroscopic techniques. A significant decrease in the band gap is observed after irradiation which is indicative of the fact that radiation has caused compaction in the glass structure.

Detecting swift heavy ion irradiation effects with graphene

In this paper we show how single layer graphene can be utilized to study swift heavy ion (SHI) modifications on various substrates. The samples were prepared by mechanical exfoliation of bulk graphite onto SrTiO3, NaCl and Si(111), respectively. SHI irradiations were performed under glancing angles of incidence and the samples were analysed by means of atomic force microscopy in ambient conditions. We show that graphene can be used to check whether the irradiation was successful or not, to determine the nominal ion fluence and to locally mark SHI impacts. In case of samples prepared in situ, graphene is shown to be able to catch material which would otherwise escape from the surface.

Effects of high-energy heavy ion irradiation on the crystal structure in CeO2 thin films

We studied the change in crystal structure of 200MeV Xe and 10MeV I ion irradiated CeO2 thin films by means of X-ray diffraction (XRD). The experimental result showed that the average lattice parameter of CeO2 decreased and the full width at half maximum increased by the ion irradiation. Their changes are well correlated with the electronic stopping powers for I and Xe ions. The dependence of lattice parameter on the electronic energy loss was analyzed by using the Poisson’s law, and the radii of the regions affected by the irradiation were determined.

Structural and Magnetic Characterizations of 200 MeV Ag<sup>15+</sup> Irradiated Bi<sub>x</sub>Co<sub>2-x</sub>MnO<sub>4</sub> Thin Films

The effect of swift heavy ion (SHI) irradiation on the structural and magnetic properties of thin films of Bi-substituted Co2MnO4 prepared by Pulsed Laser Deposition (PLD) is presented. XRD analysis reveals that the BixCo2-x MnO4 (x = 0.0, 0.1 & 0.3) films grown on amorphous quartz, and crystalline LaAlO3 (LAO) exhibited single phase cubic spinel structure with low strain before and after the irradiation at 200 MeV Ag15+ ions at three fluence values 1 × 1011, 5 × 1011 and 1 × 1012 ions/cm2. DC magnetization hysteresis loop study of the films revealed a ferrimagnetic ordering below the transition temperature ~ 185 K and the saturation magnetization was increased by the irradiation at optimal fluence value 51011 ions/cm2. X-ray Magnetic Circular Dichroism (XMCD) studies showed the antiparallel alignments of Co and Mn magnetic moments.

Structural modifications of swift heavy ion irradiated PEN probed by optical and thermal measurements

The effects of swift heavy ion irradiation on the structural characteristics of Polyethylene naphthalate (PEN) were studied. Samples were irradiated in vacuum at room temperature by lithium (50MeV), carbon (85MeV), nickel (120MeV) and silver (120MeV) ions with the fluence in the range of 1×1011–3×1012ionscm−2. Ion induced changes were analyzed using X-ray diffraction (XRD), Fourier transform infra red (FT-IR), UV–visible spectroscopy, thermo-gravimetric analysis (TGA) and differential scanning calorimetry (DSC) techniques. Cross-linking was observed at lower doses resulting in modification of structural properties, however higher doses lead to the degradation of the investigated polymeric samples.

Effect of swift heavy ion irradiation on transformations of oxide nanoclusters in ODS alloys

AbstractMicrostructure of Cr16 ferritic steel reinforced with yttrium oxide particles and KP4 oxide dispersion strengthened (ODS) alloy irradiated with 167 MeV xenon and 700 MeV bismuth ions at 300 K has been studied using high resolution transmission electron microscopy. It was found that Bi ion irradiation at fluences more than 1013 cm‐2 leads to complete amorphization of oxide particles in Cr16 samples, while central regions of large (∼20 nm) particles and small oxides (∼5 nm) in KP4 steel remain crystalline. The Xe ion irradiation effect consists in polycrystallization of single crystalline oxide particles. Small oxide particles at 1.5×1015 Xe×cm‐2 are fragmented to quasi‐amorphous state. No dissolution of nanoparticles has been revealed in all studied samples. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Swift heavy ion induced modifications in structural, optical & magnetic properties of pure and V doped ZnO films

The effect of swift heavy ion irradiation on structural, optical and magnetic properties of pure ZnO, Zn0.95V0.05O and Zn0.90V0.10O films prepared by RF sputtering are studied. X-ray diffraction (XRD) analysis reveals no significant change in the ZnO crystal structure except a small change in intensity and peak broadening on irradiation. Raman spectra reveal the degradation of crystalline quality upon ion irradiation. Atomic force microscopy (AFM) study shows the formation of smaller sized nanostructures on ion irradiation. Photoluminescence (PL) spectra of ZnO films reveal the increase of defects such as oxygen vacancy in the films upon ion irradiation. The irradiated V doped ZnO films exhibit room temperature ferromagnetic behaviour. An increase in oxygen vacancy on ion irradiation together with V ion concentration favours enhanced ferromagnetic behaviour in irradiated V doped ZnO films.

Effect of swift heavy ions on structural and optical properties of bismuth based alumino-borosilicate glasses

Borosilicate glass is considered to be one of the most suitable materials for immobilization of the high level radioactive waste (HLW). In the present investigation, glass of the composition Bi2O3 (15%)–Al2O3 (10%)–B2O3 (50%)–SiO2 (25%) was prepared by melting followed by quenching method. Optical and structural properties of these glasses were investigated using UV–visible absorption spectroscopy; X-ray diffraction and Fourier Transform Infrared (FTIR) spectroscopic techniques. Effects of heavy ion irradiation on glass network and structural units have been studied by irradiating glass thin film samples with heavy ions Li3+ (50MeV) and Ag14+(180MeV) at different fluence rates ranging from 1012ions/cm2 to 1014ions/cm2. Irradiation of materials by swift heavy ions (SHI) results in highly excited lattice atoms due to inelastic collisions with atomic electrons. Atomic displacements and structural modifications of such a lattice, brings out interesting changes in the materials. It is seen that irradiation causes significant changes in compaction of the glass network. Changes in the atomic structure before and after the irradiation are observed and explained.