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1

Teflon impregnated anatase TiO2 nanoparticles irradiated by 80 keV Xe+ ions  

NASA Astrophysics Data System (ADS)

We report the effect of 80 keV Xe+ ion irradiation on the morphological and optical responses of TiO2 nanoparticles spread over commercially available polytetrafluoroethylene (PTFE, Teflon). These nanoparticles were synthesized via a convenient, sol-gel approach with titanium isopropoxide as the main precursor. From X-ray diffraction (XRD) studies we found that, the nanoparticles crystallize in anatase phase and with a preferential orientation of crystallites along (1 0 1) plane. Upon irradiation at a fluence of 1.25 × 1017 ions/cm2, the nanoparticle dimension was found to increase from a value of ˜9 nm to ˜20-30 nm. Essentially, particle growth is predicted as a consequence of swelling behavior accompanied by the formation of Xe van der Waal crystals in isolated regions of nano-titania. Evidence of nanoripples was also witnessed on the surface of the irradiated nano-titania. The morphological evolution was assessed both by atomic force and transmission electron microscopies (AFM and TEM) independently. From the UV-Vis optical absorption studies, the estimated optical band gap was found to drop with increasing fluence, while refractive index exhibited a remarkable improvement. Photoluminescence (PL) studies have revealed that, the band edge emission and those due to the self trapped excitons (STE) and other oxygen vacancy related ones were manifested considerably as a result of Xe ion irradiation.

Khanam, Rizwin; Paul, Nibedita; Kumar, P.; Kanjilal, D.; Ahmed, Gazi A.; Mohanta, Dambarudhar

2014-10-01

2

Phase transformations in Y2O3 thin films under swift Xe ions irradiation  

NASA Astrophysics Data System (ADS)

Yttrium oxide (Y2O3) thin films deposited on silicon (Si) by an ion beam sputtering technique have been irradiated by 92 MeV xenon ions at room temperature. The microstructure of the irradiated thin film has been studied by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and electron energy loss spectroscopy (EELS). A complete structural conversion from the cubic C-type to a monoclinic B-type phase is obtained. These results were compared with the phase transformation obtained in Y2O3 thin films by medium energy Xe ion irradiation. In both cases the oxygen network behaviour under irradiation is the key parameter of the phase transformation.

Gaboriaud, R. J.; Jublot, M.; Paumier, F.; Lacroix, B.

2013-09-01

3

Irradiation system of ions (H-Xe) for biological studies near the Bragg peak  

NASA Astrophysics Data System (ADS)

We have developed a new system for irradiating biological samples in air with ions from H to Xe below 6.0MeV/nucleon near the Bragg peak. The irradiation system can provide ion beams with 20-mm diameter of which the central area of 100mm2 is uniform in fluence rate within a standard deviation of ±10%. For each ion, the linear energy transfer is selectable by irradiation positions in air, from the lowest at the surface of a vacuum window to the highest at the Bragg peak, for example, from 281 to 977 keV/?m for C ions. A wide range of fluence rates, 10-3-104ions/?m2/s, can be provided by the system, which makes it possible to irradiate a variety of biological samples with different target sizes, from small plasmid DNA to living mammalian cells. The ion fluence irradiated to each sample is calculated from the output of the secondary electron monitor using the linear relationship between the output and ion fluence measured at the sample position by CR-39 track detectors. Survival curves and visualization of NBS1 foci for human cells are presented as examples of preliminary experiments using C ions near the Bragg peak.

Konishi, Teruaki; Yasuda, Nakahiro; Takeyasu, Akihiro; Ishizawa, Sachi; Fujisaki, Takashi; Matsumoto, Kenichi; Furusawa, Yoshiya; Sato, Yukio; Hieda, Kotaro

2005-11-01

4

High dose Xe ion irradiation of yttria stabilized zirconia : influence of sputtering on implanted ion profile and retained damage /.  

SciTech Connect

Fully-stabilized zirconia is known as a radiation resistant material. The objective of many experinients on zirconia has been to test the susceptibility of this material to amorphization. Because zirconia exhibits high radiation tolerance, this has made very high fluence ion irradiation experiments a necessity and so, additional iiradiation-inducetl effects such as surface sputtering become important. In this paper, we present results from 340 keV Xe' irradiations of yttria-stabilized zirconia (YSZ) to fluences ranging froiri 1.10' to 1.5.1OZ1 ions/m2. No iunorphization of YSZ was observed after irradiation to even the highest ion fluences. To assess sputtering effects at high fluence, an analytical model was developed, using ion range and damage distribulions calculated using Monte Carlo simulations for ion-solid interactions. Analysis results and experimental data revealed that at high fluences, the implanted ion and damago distribution profiles are significantly modified by sputtering.

Afanasyev, I. V. (Ivan Viktorovich); Sickafus, K. (Kurt E.)

2001-01-01

5

Evolution of amorphization and nanohardness in SiC under Xe ion irradiation  

NASA Astrophysics Data System (ADS)

Amorphization and nanohardness changes of SiC irradiated with 7 MeV Xenon ions at doses from 0.006 to 2 dpa were investigated. At a dose of 0.6 dpa, the results of Raman spectrum reveal the formation of Si-Si and C-C bonds within the SiC network while TEM results show the appearance of amorphous islands. The hardness of irradiated SiC is regarded as a combined result of covalent-bond damage and hardening effect of defects. In the low dpa regime (<0.06 dpa), the hardness of irradiated SiC increases with increasing dose, which is mainly caused by hardening effect. Up to 0.06 dpa, the hardening increases about 20.3%. And an equilibrium is reached between the covalent-bond damage and the hardening effect when irradiated SiC begins to amorphize (0.6 dpa). Above the dose of 0.6 dpa, the hardness decreases strongly due to the grievous covalent-bond damage.

Li, Jianjian; Huang, Hefei; Lei, Guanhong; Huang, Qing; Liu, Renduo; Li, Dehui; Yan, Long

2014-11-01

6

Damage Accumulation in MgAl{sub 2}O{sub 4} and Yttria-Stabilized ZrO{sub 2} by Xe-Ion Irradiation  

SciTech Connect

Magnesium-aluminate spinel (MAS) and yttria-stabilized zirconia (YSZ) are being considered for use as ceramic matrices in proliferation resistant fuels and radioactive storage systems, and may be used either as individual entities or as constituents in multicomponent ceramic systems. It is worthwhile, therefore, to compare radiation damage in these two potentially important materials when subjected to similar irradiation conditions, e.g., ion beam irradiation. To compare radiation damage properties of these two materials, single crystals of spinel and zirconia were irradiated with 340 keV Xe{sup ++} ions at 120 K, and subsequently investigated by Rutherford backscattering and ion channeling (RBS/C), and optical absorption spectroscopy. Results indicate that damage accumulation in both spinel and zirconia follow a three stage process: (1) very slow damage accumulation over a wide range of dose; (2) rapid changes in damage over a range of doses from about 0.25 to 25 displacements per atom (DPA); (3) slower damage accumulation at very high doses and possibly saturation. Optical absorption results indicate that F-centers form in Xe ion-irradiated spinel and that the concentration of these centers saturates at high dose. Absorption bands are also formed in both spinel and zirconia that are due to point defect complexes formed upon irradiation. These bands increase in intensity with increasing Xe dose, and, in the case of zirconia, without saturation. Finally the rate of change in intensity of these bands with increasing Xe dose, mimic the changes in damage observed by RBS/C with increasing dose.

Afanasyev-Charkin, I.V.; Gritsyna, V.T.; Cooke, D.W.; Bennett, B.L.; Sickafus, K.E.

1999-04-25

7

Nanoparticle Ejection from Au Induced by Single Xe Ion Impacts  

SciTech Connect

Insitu transmission electron microscopy has been used to observe sputtered Au during Xe ion irradiation in transmission geometry. The sputtered Au was collected on an electron transparent carbon foil. Nanoparticles were observed on the collector foil after they were ejected by single ion impacts. The ejection is from the melt zone formed during the thermal spike phase of a displacement cascade produced near the surface by a single ion impact. Such single ion impacts are also capable of producing craters. Ejected nanoparticles can make a significant contribution to sputtering.

Birtcher, Robert C.; Donnelly, S. E.; Schlutig, S.

2000-12-04

8

Nanoparticle ejection from Au by single Xe ion impacts.  

SciTech Connect

In situ transmission electron microscopy has been used to observe sputtered Au during Xe ion irradiation in transmission geometry. The sputtered Au was collected on an electron transparent carbon foil. Nanoparticles were observed on the collector foil after they were ejected by single ion impacts. The ejection is from the melt zone formed during the thermal spike phase of a displacement cascade produced near the surface by a single ion impact. Such single ion impacts are also capable of producing craters. Ejected nanoparticles can make a significant contribution to sputtering.

Birtcher, R. C.; Donnelly, S. E.; Schlutig, S.; Materials Science Division; Univ. of Salford; CIRIL Lab. CEA /CNRS

2000-12-04

9

The studies of irradiation assisted stress corrosion cracking on reactor internals stainless steel under Xe irradiation  

NASA Astrophysics Data System (ADS)

Specimens of Chinese domestic reactor internals stainless steel were irradiated with 6 MeV Xe ions for three peak displacement damage of 2, 7 and 15 dpa at room temperature. The slow strain rate tests (SSRT), grazing incidence X-ray diffraction (GIXRD) and nano-indentation tests were carried out to study the IASCC properties, phase transition and nano-hardness variations. The SSRT results indicate that the IASCC susceptibility increases with irradiation damage. Ion irradiation accelerates the stress corrosion cracking (SCC). A new ferrite phase diffraction peak of ?(1 1 0) after irradiated to 7 dpa and another two ? phase of ?(2 0 0) and ?(2 1 1) after irradiated to 15 dpa were observed by GIXRD, which may be due to localized deformation. A similar trend of irradiation hardening and IASCC susceptibility was observed, which suggests an essential connection between them.

Wang, Rong-shan; Xu, Chao-liang; Liu, Xiang-bing; Huang, Ping; Chen, Yu

2015-02-01

10

Experimental ion mobility measurements in Xe-N2 mixtures  

NASA Astrophysics Data System (ADS)

In this paper we present the results for the ion mobility measurements made in gaseous mixtures of xenon (Xe) and nitrogen (N2) for low reduced electric fields (in the 15 Td to 30 Td range), at room temperature. The choice of reduced electric fields was guided by typical gaseous detector's demands. In the 0-100% range of Xe concentrations in the mixture, only one peak was observed which was attributed to Xe2+; in fact its mobility was found to follow Blanc's law. A typical time-of-arrival spectrum for 90% Xe and 10% N2 is shown. The reduced mobilities, obtained from the peaks, are calculated and presented in this paper.

Garcia, A. N. C.; Neves, P. N. B.; Trindade, A. M. F.; Cortez, A. F. V.; Santos, F. P.; Conde, C. A. N.

2014-07-01

11

Sputtering yields exceeding 1000 by 80 keV Xe irradiation of Au nanorods  

NASA Astrophysics Data System (ADS)

Using experiments and computer simulations, we find that 80 keV Xe ion irradiation of Au nanorods can produce sputtering yields exceeding 1000, which to our knowledge are the highest yields reported for sputtering by single ions in the nuclear collision regime. This value is enhanced by more than an order of magnitude compared to the same irradiation of flat Au surfaces. Using MD simulations, we show that the very high yield can be understood as a combination of enhanced yields due to low incoming angles at the sides of the nanowire, as well as the high surface-to-volume ratio causing enhanced explosive sputtering from heat spikes. We also find, both in experiments and simulations, that channeling has a strong effect on the sputtering yield: if the incoming beam happens to be aligned with a crystal axis of the nanorod, the yield can decrease to about 100.

Ilinov, A.; Kuronen, A.; Nordlund, K.; Greaves, G.; Hinks, J. A.; Busby, P.; Mellors, N. J.; Donnelly, S. E.

2014-12-01

12

Xe/+/ -induced ion-cyclotron harmonic waves  

NASA Astrophysics Data System (ADS)

Xenon ion sources on an ejectable package separated from the main payload during the flights of Porcupine rockets F3 and F4 which were launched from Kiruna, Sweden on March 19 and 31, 1979, respectively. The effects of the xenon ion beam, detected by the LF (f less than 16 kHz) wideband electric field experiment and analyzed by using a sonograph, are discussed. Particular attention is given to the stimulation of the ion-cyclotron harmonic waves which are usually linked to the local proton gyro-frequency, but are sometimes related to half that frequency. It was found that in a plasma dominated by O(+) ions, a small amount (1-10%) of protons could cause an effect such that the O(+) cyclotron harmonic waves are set up by the hydrogen ions, the net result being the observation of harmonic emissions separated by the hydrogen ion gyro frequency.

Jones, D.

13

Microstructure evolution in Xe-irradiated UO2 at room temperature  

SciTech Connect

In situ Transmission Electron Microscopy was conducted for single crystal UO2 to understand the microstructure evolution during 300 keV Xe irradiation at room temperature. The dislocation microstructure evolution was shown to occur as nucleation and growth of dislocation loops at low irradiation doses, followed by transformation to extended dislocation segments and tangles at higher doses. Xe bubbles with dimensions of 1-2 nm were observed after room-temperature irradiation. Electron Energy Loss Spectroscopy indicated that UO2 remained stoichiometric under room temperature Xe irradiation.

L.F. He; J. Pakarinen; M.A. Kirk; J. Gan; A.T. Nelson; X.-M. Bai; A. El-Azab; T.R. Allen

2014-07-01

14

Microstructure and nanoindentation of the CLAM steel with nanocrystalline grains under Xe irradiation  

NASA Astrophysics Data System (ADS)

This work presents an early look at irradiation effects on China low activation martensitic (CLAM) steel with nanocrystalline grains (NC-CLAM steels) under 500 keV Xe-ion bombardment at room temperature to doses up to 5.3 displacements per atom (dpa). The microstructure in the topmost region of the steel is composed of nanocrystalline grains with an average diameter of 13 nm. As the samples were implanted at low dose, the nanocrystalline grains had martensite lath structure, and many dislocations and high density bubbles were introduced into the NC-CLAM steels. As the irradiation dose up to 5.3 dpa, a tangled dislocation network exists in the lath region, and the size of the bubbles increases. X-ray diffraction results show that the crystal quality decreases after irradiation, although the nanocrystals obviously coarsen. Grain growth under irradiation may be ascribed to the direct impact of the thermal spike on grain boundaries in the NC-CLAM steels. In irradiated samples, a compressive stress exists in the surface layer because of grain growth and irradiation-introduced defects, while the irradiation introduced grain-size coarsening and defects gradients from the surface to matrix result in a tensile stress in the irradiated NC-CLAM steels. Nanoindentation was used to estimate changes in mechanical properties during irradiation, and the results show that the hardness of the NC-CLAM steels increases with increasing irradiation dose, which was ascribed to the competition between the grain boundaries and the irradiation-introduced defects.

Chang, Yongqin; Zhang, Jing; Li, Xiaolin; Guo, Qiang; Wan, Farong; Long, Yi

2014-12-01

15

Dose dependence of the production yield of endohedral 133Xe-fullerene by ion implantation  

NASA Astrophysics Data System (ADS)

The production yield of endohedral 133Xe-fullerene by ion implantation has been studied by taking advantage of the radioactivity of 133Xe. Fullerene targets, which were produced by vacuum evaporation of C 60 or C 70 on a Ni backing, were bombarded with 30-38 keV 133Xe ions by using an isotope separator at doses ranging from 1 × 10 12 to 1 × 10 14 cm -2. The production yield of endohedral 133Xe-fullerene was determined by an high performance liquid chromatography analysis following the dissolution of the targets in o-dichlorobenzene. It was found that the production yield decreased with increasing dose and incident energy, and the production yield of 133Xe@C 70 was higher than that of 133Xe@C 60 for the same dose and incident energy. Those production yields are discussed in connection with amorphization of fullerene molecules in collisions with 133Xe ions.

Watanabe, S.; Ishioka, N. S.; Shimomura, H.; Muramatsu, H.; Sekine, T.

2003-05-01

16

Structural investigation of xenon-ion-beam-irradiated glassy carbon  

Microsoft Academic Search

Raman spectroscopy, cross-sectional transmission electron microscopy, and electron-energy-loss spectroscopy have been used to monitor the ion-beam-induced transformation in glassy carbon irradiated with 320-keV Xe ions to doses between 5×1012 and 6×1016 ions\\/cm2. It was found that (i) the ion beam amorphizes the glassy carbon structure; (ii) the amorphization is accompanied by a compaction of the glassy carbon from an initial

D. G. McCulloch; S. Prawer; A. Hoffman

1994-01-01

17

Searching for the Mass of the Neutrino (Spectroscopy of Ba+ ions in Liquid 136Xe)  

NASA Astrophysics Data System (ADS)

Our group is developing a new detection technique for zero neutrino double beta decay: efficient 136Ba+ daughter ion tagging by laser induced fluorescence in a liquid Xe time-projection chamber. Double beta decay is the only sensitive probe of the absolute neutrino mass scale below the present limit of about 0.3 eV. In preparation for this final experiment one must first understand the spectroscopy of Ba+ ions in liquid Xe and demonstrate that a single Ba+ ion can be detected in the liquid Xe. A liquid Xe test apparatus in which Ba+ ions are created by laser ablation of a Ba sample has been constructed. Preliminary excitation and emission spectra of Ba+ in liquid Xe are reported.

Hall, Kendy; Jeng Fairbank, Shie-Chang, Jr.; Miyajima, Mitsuhiro

2002-10-01

18

Surface damage on 6H-SiC by highly-charged Xeq+ ions irradiation  

NASA Astrophysics Data System (ADS)

Surface damage on 6H-SiC irradiated by highly-charged Xeq+ (q = 18, 26) ions to different fluences in two geometries was studied by means of AFM, Raman scattering spectroscopy and FTIR spectrometry. The FTIR spectra analysis shows that for Xe26+ ions irradiation at normal incidence, a deep reflection dip appears at about 930 cm-1. Moreover, the reflectance on top of reststrahlen band decreases as the ion fluence increases, and the reflectance at tilted incidence is larger than that at normal incidence. The Raman scattering spectra reveal that for Xe26+ ions at normal incidence, surface reconstruction occurs and amorphous stoichiometric SiC and Si-Si and C-C bonds are generated and original Si-C vibrational mode disappears. And the intensity of scattering peaks decreases with increasing dose. The AFM measurement shows that the surface swells after irradiation. With increasing ion fluence, the step height between the irradiated and the unirradiated region increases for Xe18+ ions irradiation; while for Xe26+ ions irradiation, the step height first increases and then decreases with increasing ion fluence. Moreover, the step height at normal incidence is higher than that at tilted incidence by the irradiation with Xe18+ to the same ion fluence. A good agreement between the results from the three methods is found.

Zhang, L. Q.; Zhang, C. H.; Han, L. H.; Xu, C. L.; Li, J. J.; Yang, Y. T.; Song, Y.; Gou, J.; Li, J. Y.; Ma, Y. Z.

2014-12-01

19

Accurate Xe isotope measurement using JPL ion trap.  

PubMed

We report an approach for the reproducible and accurate compositional analysis of different mixtures of Xe isotopes using miniature Jet Propulsion Laboratory Quadrupole Ion Trap (JPL-QIT). A major study objective was to validate the recent instrumental improvements to the long-term operational stability under different pressures, temperatures, and trapping conditions. We propose that the present device can be used in certification of trace amounts of isotopes in mixtures dominated by one or more isotopes. Measured isotopic compositions are verified against commercially available standards with accuracy better than 0.07%. To aid the analysis of experimental data, we developed a scalable replica fitting method and use peak areas as descriptors of relative isotopic abundances. This low-power and low-mass device is ideally suited for planetary explorations aimed to enhance quantitative analysis for major isotopes present in small amounts of atmospheric samples. PMID:25216693

Madzunkov, Stojan M; Nikoli?, Dragan

2014-11-01

20

Modifications in structure and optical property of Cu nanoparticles in SiO2 by post heavy ion irradiation  

NASA Astrophysics Data System (ADS)

The implantation-synthesized Cu nanoparticles (NPs) in silica were irradiated with 500 keV Xe and Ar ions, respectively. After Xe ion irradiation at a fluence of 2 × 1016/cm2, the average diameter of Cu NPs was increased from 7.3 to 8.5 nm, and especially, Cu NPs with a diameter of 11-14 nm were formed beyond the projected range of Cu ions and nearly aligned at the same depth, which presented a higher volume fraction. As a result, the Cu surface plasmon resonance (SPR) absorption peak was enhanced. However, if Xe ion fluence was less than 1 × 1016/cm2, no clear variation of the Cu SPR absorption peak could be found. Further, it was also revealed that Xe ion irradiation caused the Cu SPR absorption peak to more drastically change than Ar ion irradiation at the same ion fluence. The underlying processes for the above findings were discussed and tentatively proposed.

Liu, Changlong; Wang, Nana; Wang, Jun; Liu, Huixian; Jia, Guangyi; Mu, Xiaoyu

2014-05-01

21

Influence of Xe{sub 2}{sup +} ions on the micro-hollow cathode discharge driven by thermionic emission  

SciTech Connect

The influence of Xe{sub 2}{sup +} dimer ions and excited Xe* atoms on the hollow cathode discharge driven by electron thermionic emission is studied using two-dimensional Particle-in-Cell Monte Carlo Collisions modeling. A comparison with the results of two-component (electrons and Xe{sup +} ions) plasma modeling showed that the presence of the Xe{sub 2}{sup +} dimer ions and excited Xe* atoms in the plasma affects the plasma parameters (density, potential, and ion fluxes toward the cathode). The influence of Xe{sub 2}{sup +} ions and Xe* atoms on the plasma sheath parameters, such as thickness and the ion velocity at the sheath edge, is analyzed.

Levko, D. [LAPLACE (Laboratoire Plasma et Conversion d'Energie), Universite de Toulouse, UPS, INPT Toulouse, 118 Route de Narbonne, F-31062 Toulouse Cedex 9 (France)] [LAPLACE (Laboratoire Plasma et Conversion d'Energie), Universite de Toulouse, UPS, INPT Toulouse, 118 Route de Narbonne, F-31062 Toulouse Cedex 9 (France); Bliokh, Y. P.; Krasik, Ya. E. [Department of Physics, Technion, 32000 Haifa (Israel)] [Department of Physics, Technion, 32000 Haifa (Israel)

2014-04-15

22

Observation of hyperfine mixing in measurements of a magnetic octupole decay in isotopically pure nickel-like 129Xe and 132Xe ions  

SciTech Connect

We present measurements of high statistical significance of the rate of the magnetic octupole (M3) decay in nickel-like ions of isotopically pure {sup 129}Xe and {sup 132}Xe. On {sup 132}Xe, an isotope with zero nuclear spin and therefore without hyperfine structure, the lifetime of the metastable level was established as (15.06 {+-} 0.24) ms. On {sup 129}Xe, an additional fast (2.7 {+-} 0.1 ms) decay component was established that represents hyperfine mixing with a level that decays by electric quadrupole (E2) radiation.

Trabert, E; Beiersdorfer, P; Brown, G V

2006-12-21

23

TiO2 films photocatalytic activity improvements by swift heavy ions irradiation  

NASA Astrophysics Data System (ADS)

TiO2 thin films synthesized by sol-gel on glass substrates are irradiated by 90 MeV Xe ions at various fluences and room temperature under normal incidence. The structural, electrical, optical and surface topography properties before and after Xe ions irradiation are investigated. X-ray diffraction (XRD) reveals that the crystallinity is gradually destroyed, and the films become amorphous above 5×1012 ions/cm2. The band gap is not affected by Xe ions irradiation as evidenced from the optical measurements. By contrast, the conductivity increases with raising Xe fluence. The energy band diagram established from the electrochemical characterization shows the feasibility of TiO2 films for the photo-electrochemical chromate reduction. Xe ion irradiation results in enhanced photocatalytic activity in aquatic medium, evaluated by the reduction of Cr(VI) into trivalent state. TiO2 films irradiated at 1013 Xe/cm2 exhibit the highest photoactivity; 69% of chromate (10 ppm) is reduced at pH ~3 after 4 h of exposure to sunlight (1120 mW cm-2) with a quantum yield of 0.06%.

Rafik, Hazem; Mahmoud, Izerrouken; Mohamed, Trari; Abdenacer, Benyagoub

2014-08-01

24

Nanoparticle ejection from gold during ion irradiation.  

SciTech Connect

We have used in situ transmission electron microscopy to study the sputtering of gold by inert-gas ions and, in particular, nanoparticles ejected by individual ion impacts. Irradiations were performed at room temperature in transmission geometry with Ne, Ar, Kr and Xe ions at energies between 100 and 600 keV. Nanoparticles result from situations in which ion impacts also give rise to nanometer size craters on the surface. The number of nanoparticles increased linearly with increasing ion dose. The rate of nanoparticle ejection scales with the probability, calculated with standard Monte Carlo techniques, for high-energy deposition events by individual ions in the near-surface region regardless of the irradiation. The percentage of near-surface, high-energy recoils that eject a nanoparticle is high. The rate of nanoparticle ejection depends on energy transfer to the Au lattice and not on the ion that makes the impact or its energy. Ejected nanoparticles account for the nonlinear component of sputtering. Monte Carlo calculations offer a general technique for predicting situations in which nanoparticles can be ejected and thus when the nonlinear contribution to the sputtering yield is likely to be significant.

Birtcher, R. C.; Donnelly, S. E.; Schlutig, S.; Materials Science Division; Univ. of Salford; Univ. of Caen

2004-01-01

25

Spontaneous magnetization induced in the spinel ZnFe2O4 by heavy ion irradiation in the electronic stopping power regime  

Microsoft Academic Search

Zinc ferrite, ZnFe2O4, has been irradiated by GeV heavy ions (Kr, Xe, Pb, U) and the induced chemical and physical modifications have been investigated by magnetization measurements, Mössbauer spectroscopy and high resolution electron microscopy. Xe, Pb and U ion irradiation leads to amorphized latent tracks, while Kr ion irradiation produced Moirés characteristic lattice misorientations. In both cases, relaxation phenomena involve

F. Studer; Ch. Houpert; D. Groult; J. Yun Fan; A. Meftah; M. Toulemonde

1993-01-01

26

Effect of XeCl laser irradiation on the defect structure of Nd:YAG crystals  

NASA Astrophysics Data System (ADS)

This paper presents the effect of XeCl laser irradiation on Nd:YAG single crystal samples with various number of pulses at different repetition rates and laser fluences. Effects of the irradiation on the optical and structural properties of the crystal are analyzed by UV-vis-NIR spectroscopy. Annihilation of some point defects of the crystal structure is observed following laser irradiation at a fluence of 100 mJ cm-2 with 100 and 500 pulses. Increasing the laser fluence and pulse numbers leads to saturation and new defects are found to be formed in the crystal. Additional absorption spectra of the irradiated samples show that oxygen vacancies in the Nd:YAG crystals are removed during the low-dose irradiation. The laser irradiation is compared to the thermal annealing process for Nd:YAG crystal modification. Additional absorption spectrum of an annealed sample reveals that induced negative absorption band at 236 nm is correlated with the annihilation of the oxygen vacancy center. Our results also demonstrate that XeCl laser treatment has several advantages upon annealing at high temperatures in the Nd:YAG crystal quality improvement. Thus, the present work can give a new approach to modify Nd:YAG crystals to be used in a wide variety of solid-state laser engineering.

Panahibakhsh, S.; Jelvani, S.; Maleki, M. H.; Mollabashi, M.; Abolhosseini, S.

2014-09-01

27

Irradiation hardening of ODS ferritic steels under helium implantation and heavy-ion irradiation  

NASA Astrophysics Data System (ADS)

Irradiation hardening of ODS ferritic steels after multi-energy He-ion implantation, or after irradiation with energetic heavy ions including Xe and Bi-ions was investigated with nano-indentation technique. Three kinds of high-Cr ODS ferritic steels including the commercial MA956 (19Cr-3.5Al), the 16Cr-0.1Ti and the 16Cr-3.5Al-0.1Zr were used. Data of nano-hardness were analyzed with an approach based on Nix-Gao model. The depth profiles of nano-hardness can be understood by the indentation size effect (ISE) in specimens of MA956 implanted with multi-energy He-ions or irradiated with 328 MeV Xe ions, which produced a plateau damage profile in the near-surface region. However, the damage gradient overlaps the ISE in the specimens irradiated with 9.45 Bi ions. The dose dependence of the nano-hardness shows a rapid increase at low doses and a slowdown at higher doses. An 1/2-power law dependence on dpa level is obtained. The discrepancy in nano-hardness between the helium implantation and Xe-ion irradiation can be understood by using the average damage level instead of the peak dpa level. Helium-implantation to a high dose (7400 appm/0.5 dpa) causes an additional hardening, which is possibly attributed to the impediment of motion dislocations by helium bubbles formed in high concentration in specimens.

Zhang, Hengqing; Zhang, Chonghong; Yang, Yitao; Meng, Yancheng; Jang, Jinsung; Kimura, Akihiko

2014-12-01

28

Effect of heavy noble gas ion irradiation on terahertz emission efficiency of InP (100) and (111) crystal planes  

NASA Astrophysics Data System (ADS)

Emission of terahertz (THz) electromagnetic radiation from heavily-doped (5 × 1018 cm-3) (100) and (111) InP bulk materials and nanoporous honeycomb membranes, irradiated with heavy noble gas (Kr and Xe) ions, is presented. Irradiating samples with Kr or Xe improves THz emission efficiency. For (111) samples, as for unirradiated samples, the irradiated porous structures generate more THz radiation than their bulk counterparts. On the other hand, in contrast to unirradiated (100) samples, the irradiated (100) samples show a decrease in THz emission with porosity. We attribute this behaviour to changes in the local electric field due to the combined effect of the irradiation and nanoporosity.

Radhanpura, K.; Lewis, R. A.; Sirbu, L.; Enachi, M.; Tiginyanu, I. M.; Skuratov, V. A.

2014-09-01

29

An attempt to reproduce high burn-up structure by ion irradiation of SIMFUEL  

NASA Astrophysics Data System (ADS)

Experiments in IC-100 and U-400 cyclotrons were conducted with SIMFUEL pellets (11.47 wt.% of fission products simulators) to reproduce some aspects of the long-term irradiation conditions in epithermal reactors. Pellets were irradiated with Xe16+, Xe24+ and He+ at energies ranging from 20 keV (He+) to 320 keV (Xe16+) and 1-90 MeV (Xe24+). Some samples were subsequently annealed to obtain larger grain sizes and to study defects recovery. The major microstructural changes consisted in grain sub-division observed on SEM and AFM images and change in composition registered by EPMA (pellets irradiated with 1-90 MeV Xe24+ ions at fluence of 5 × 1015 cm-2). Lattice distortion and increase in dislocation density is also noted according to X-ray data. At low energies and high fluences formation of bubbles (20 keV He+ at 5.5 × 1017 cm-2) was observed. Grain sub-division exhibits full coverage of the grain body and preservation of former grain boundaries. The size of sub-grains depends on local dislocation density and changes from 200 nm to 400 nm along the irradiated surface. Beneath it the size ranges from 150 to 600 nm. Sub-grains are not observed in samples irradiated by low-energy ions even at high dislocation densities.

Baranov, V. G.; Lunev, A. V.; Reutov, V. F.; Tenishev, A. V.; Isaenkova, M. G.; Khlunov, A. V.

2014-09-01

30

The effects of nuclear and electronic stopping powers on ion irradiated novolac–diazoquinone films  

Microsoft Academic Search

The structure and surface modifications induced in ion irradiated AZ-1350J photoresist films as function of energy, fluence and the amount of electronic and nuclear deposited energy density are investigated in detail. The films have been irradiated with 380keV He+, 4MeV I2+ and 800keV Xe2+ ions, in a fluence range from 1013 to 1016cm?2. At these energies, the ranges of the

Irene T. S. Garcia; F. C. Zawislak; D. Samios

2004-01-01

31

Generation of strongly coupled Xe cluster nanoplasmas by low intensive soft x-ray laser irradiation  

SciTech Connect

A seeding gas jet including Xe clusters was irradiated with a laser-driven plasma soft x-ray laser pulse ({lambda}=13.9 nm, {approx}7 ps, {<=}5 Multiplication-Sign 10{sup 9} W/cm{sup 2}), where the laser photon energy is high enough to ionize 4d core electrons. In order to clarify how the innershell ionization followed by the Auger electron emission is affected under the intense laser irradiation, the electron energy distribution was measured. Photoelectron spectra showed that the peak position attributed to 4d hole shifted to lower energy and the spectral width was broadened with increasing cluster size. Moreover, the energy distribution exhibited that a strongly coupled cluster nanoplasma with several eV was generated.

Namba, S.; Hasegawa, N.; Kishimoto, M.; Nishikino, M.; Kawachi, T. [Graduate School of Engineering, Hiroshima University,Kagamiyama 1-4-1, Higashi-Hiroshima, Hiroshima, 739-8527 (Japan); Quantum Beam Science Directorate, Japan Atomic Energy Agency, Umemidai 8-1, Kizugawa, Kyoto, 619-0215 (Japan)

2012-07-11

32

In-Situ Laser Tagging of ^136Ba^+ Ions in a Liquid ^136Xe Detector  

NASA Astrophysics Data System (ADS)

Our group is working in partnership with the Enriched Xenon Observatory (EXO) collaboration to measure the effective Majorana mass of neutrinos with a sensitivity of 0.01eV in a ton size liquid ^136Xe detector. The only way to achieve such sensitivity is by neutrinoless double beta decay (00??) with tagging of the ^136Ba^+ daughter ion at the decay site. At CSU, we are developing a new fluorescence technique for in-situ laser tagging of a single ^136Ba^+ ion in liquid Xe. Laser ablation is used to implant approximately 10^8 Ba^+ ions per pulse into a liquid xenon cell. In the past we have been troubled with inconsistencies in our fluorescence spectra, which may be due to impurities or unknown particles within our liquid Xe. To understand these problems, a liquid xenon recirculation system and purity monitor has been built. Purity levels of ppb can now be measure in our liquid xenon system. I will present possible emission spectra of Ba^+ ions in liquid xenon and discuss how they correlate with the liquid xenon purity.

Hall, Kendy; Benitez, Cesar; Fairbank, William

2008-10-01

33

Molecular dynamics study on low-energy sputtering of carbon material by Xe ion bombardment  

NASA Astrophysics Data System (ADS)

The low-energy sputtering of carbon material under Xe ion bombardment is studied through the molecular dynamics (MD) simulation. For the normal incidence of Xe, the MD result of sputtering yield almost agrees with the experimental result by Williams et al. (AIAA-2004-3788). However, the experimental result shows a less incident angle dependence than the MD result because the experiment performed on a rough surface. It is found that the sputtered particles have memory of the projectile because the sputtered particles by the low-energy projectile undergo only a few collisions before the ejection. Low density of an amorphous carbon surface brings the decrease of the sputtering yield and the increase of high-energy sputtered atoms.

Muramoto, T.; Hyakutake, T.

2013-05-01

34

1 MeV electron irradiation of solid Xe nanoclusters in Al : an in-situ HRTEM study.  

SciTech Connect

Thin film samples of a simple embedded nanocluster system consisting of solid Xe precipitates in Al have been subjected to 1 MeV electron irradiation in a high-voltage electron microscope. High-resolution images have been recorded on videotape in order to monitor the changes to the system resulting from the passage of electrons through the film. Inspection of the video recordings (in some cases frame-by-frame) reveals that complex, rapid processes occur under the electron beam. These include, movement of small clusters, coalescence of neighboring clusters, shape changes, the apparent melting and resolidification of the Xe, and the creation and annealing of extended defects within the Xe lattice. A tentative interpretation of some of the observations is presented in terms of the electron-induced displacement processes at the surface of the clusters.

Donnelly, S. E.; Furuya, K.; Song, M.; Birtcher, R. C.; Allen, C. W.

1997-12-05

35

New process observed in collisions between highly charged protonated protein and Xe8+ Xe5+ He2+ ions  

NASA Astrophysics Data System (ADS)

Electron multicapture processes have been studied in collisions between cytochrome C protein and highly charged Xe and He projectile at keV kinetic energy range. In competition with single and double electron capture, a new and unexpected channel attributed to deprotonation process of the protein has been observed.

Martin, S.; Chen, L.; Brédy, R.; Vernier, A.; Dugourd, P.; Antoine, R.; Ortéga, C.; Ji, M.; Bernard, J.; Gonzalez Maganad, O.; Reitsma, G.; Schlathölter, T.

2014-04-01

36

Valence-shell photoionization of Ag-like Xe7+ ions: experiment and theory  

NASA Astrophysics Data System (ADS)

We report on experimental and theoretical results for the photoionization of Ag-like xenon ions, Xe7+, in the photon energy range 95–145 eV. The measurements were carried out at the Advanced Light Source at an energy resolution of ?E = 65 meV with additional measurements made at ?E = 28 meV and 39 meV. Small resonance features below the ground-state ionization threshold, at about 106 eV, are due to the presence of metastable Xe7+(4{{d}10}4f{{ }2}f5/2,7/2{^\\circ }) ions in the ion beam. On the basis of the accompanying theoretical calculations using the Dirac atomic R-matrix codes (DARC), an admixture of only a few percent of metastable ions in the parent ion beam is inferred, with almost 100% of the parent ions in the (4{{d}10}5s{{ }2}{{s}1/2}) ground level. The cross section is dominated by a very strong resonance associated with 4d\\to 5f excitation and subsequent autoionization. This prominent feature in the measured spectrum is the 4{{d}9}5s5{{f} 2}{{P}{^\\circ }} resonance located at (122.139 ± 0.01) eV. An absolute peak cross section of 1.2 Gigabarns was measured at 38 meV energy resolution. The experimental natural width ? = 76 ± 3 meV of this resonance compares well with the theoretical estimate of 88 meV obtained from the DARC calculation with 249 target states. Given the complexity of the system, overall satisfactory agreement between theory and experiment is obtained for the photon energy region investigated.

Müller, A.; Schippers, S.; Esteves-Macaluso, D.; Habibi, M.; Aguilar, A.; Kilcoyne, A. L. D.; Phaneuf, R. A.; Ballance, C. P.; McLaughlin, B. M.

2014-11-01

37

Relativistic Many-body Moller-Plesset Perturbation Theory Calculations of the Energy Levels and Transition Probabilities in Na- to P-like Xe Ions  

SciTech Connect

Relativistic multireference many-body perturbation theory calculations have been performed on Xe{sup 43+}-Xe{sup 39+} ions, resulting in energy levels, electric dipole transition probabilities, and level lifetimes. The second-order many-body perturbation theory calculation of energy levels included mass shifts, frequency-dependent Breit correction and Lamb shifts. The calculated transition energies and E1 transition rates are used to present synthetic spectra in the extreme ultraviolet range for some of the Xe ions.

Vilkas, M J; Ishikawa, Y; Trabert, E

2007-03-27

38

Local structure and hardness change of Zr50Cu40Al10 bulk glassy alloy after heavy ion irradiation  

NASA Astrophysics Data System (ADS)

Zr50Cu40Al10 bulk glassy alloys before and after 200 MeV Xe ion irradiation with a maximum dose of about 1 × 1014 ions/cm2 and 5 MeV Al ion ("self-ion") irradiation with a dose of about 3 × 1014 ions/cm2 have been investigated by positron annihilation and micro-Vickers hardness measurements. No crystallization took place in the samples after the irradiation according to X-ray diffraction measurement. We found that the hardness decreases by irradiation with increasing the irradiation dose. A decreasing trend of positron lifetime, which reflects the size of free volume, was observed. These facts imply that heavy ion irradiation can be used for the local modification of hardness, which is not thermal effect, in Zr50Cu40Al10 bulk glassy alloy.

Onodera, Naoto; Ishii, Akito; Fukumoto, Yuka; Iwase, Akihiro; Yokoyama, Yoshihiko; Hori, Fuminobu

2012-07-01

39

Theoretical prediction of HRgCO(+) ion (Rg=He, Ne, Ar, Kr, and Xe).  

PubMed

Ab initio quantum chemical methods have been employed to investigate the structure, stability, charge redistribution, and harmonic vibrational frequencies of rare gas (Rg=He, Ne, Ar, Kr, and Xe) containing HRgCO(+) ion. The Rg atoms are inserted in between the H and C atoms of HCO(+) ion and the geometries are optimized for minima as well as transition state using second order Moller-Plesset perturbation theory, density functional theory, and coupled-cluster theory [CCSD(T)] methods. The HRgCO(+) ions are found to be metastable and exhibit a linear structure at the minima position and show a nonlinear structure at the transition state. The predicted ion is unstable with respect to the two-body dissociation channel leading to the global minima (HCO(+)+Rg) on the singlet potential surface. The binding energies corresponding to this channel are -406.4, -669.3, -192.3, -115.4, and -52.2 kJ mol(-1) for HHeCO(+), HNeCO(+), HArCO(+), HKrCO(+), and HXeCO(+) ions, respectively, at CCSD(T) method. However, with respect to other two-body dissociation channel, HRg(+)+CO, the ions are found to be stable and have positive energies except for HNeCO(+) at the same level of theory. The computed binding energies for this channel are 15.0, 28.8, 29.5, and 29.1 kJ mol(-1) for HHeCO(+), HArCO(+), HKrCO(+), and HXeCO(+) ions, respectively. Very high positive three-body dissociation energies are found for H+Rg+CO(+) and H(+)+Rg+CO dissociation channels. It indicates the existence of a very strong bonding between Rg and H atoms in HRgCO(+) ions. The predicted ions dissociate into global minima, HCO(+)+Rg, via a transition state involving H-Rg-C bending mode. The barrier heights for the transition states are 22.7, 10.1, 13.1, and 15.0 kJ mol(-1) for He, Ar, Kr, and Xe containing ions, respectively. The computed two-body dissociation energies are comparable to that of the experimentally observed mixed cations such as ArHKr(+), ArHXe(+), and KrHXe(+) in an electron bombardment matrix isolation technique. Thus HRgCO(+) cations may also be possible to prepare and characterize similar to the mixed cations (RgHRg('))(+) in low temperature matrix isolation technique. PMID:19045398

Jayasekharan, T; Ghanty, T K

2008-11-14

40

Preparation of ion-track membranes of poly( p-phenylene terephthalamide): Control of pore shape by irradiation with different ion beams  

NASA Astrophysics Data System (ADS)

The preparation of ion-track membranes of thermally stable poly( p-phenylene terephthalamide) (PPTA) was performed by ion beam irradiation followed by chemical etching with a sodium hypochlorite solution. Cylindrical pores were observed in the membrane irradiated with 197Au and 238U ions at an energy of 11.1 MeV/n. In contrast, funnel shape pores appeared in the membrane irradiated with 84Kr, 102Ru and 129Xe ion at energies of 6.2, 3.6 and 3.5 MeV/n, respectively. The 197Au and 238U ion irradiation was found to exhibit more than four times larger sensitivity to the track etching under the same etching conditions. Consequently, the pore shape can be controlled by the masses and energies of the irradiated ions, in close relation to the etching sensitivity of the track.

Suzuki, Yasuyuki; Yamaki, Tetsuya; Koshikawa, Hiroshi; Asano, Masaharu; Voss, Kay-Obbe; Neumann, Reinhard; Yoshida, Masaru

2007-07-01

41

Photoionization cross section calculations for the halogen-like ions Kr+ and Xe+  

NASA Astrophysics Data System (ADS)

Photoionization cross section calculations on the halogen-like ions; Kr+ and Xe+ have been performed for a photon energy range from each ion threshold to 15 eV, using large-scale close-coupling calculations within the Dirac-Coulomb R-matrix approximation. The results from our theoretical work are compared with recent measurements made at the ASTRID merged-beam set-up at the University of Aarhus in Denmark and from the Fourier transform ion cyclotron resonance trap method at the SOLEIL synchrotron radiation facility in Saint-Aubin, France Bizau et al (2011 J. Phys. B: At. Mol. Opt. Phys. 44 055205) and the advanced light source Müller (2012 private communication), Aguliar et al (2012 J. Phys.: Conf. Ser. at press). For each of these complex ions our theoretical cross section results over the photon energy range investigated are seen to be in excellent agreement with experiment. Resonance energy positions and quantum defects of the prominent Rydberg resonances series identified in the spectra are compared with experiment for these complex halogen-like ions.

McLaughlin, B. M.; Ballance, C. P.

2012-04-01

42

Effects of ion irradiation on solid oxide fuel cells  

NASA Astrophysics Data System (ADS)

The solid oxide fuel cell (SOFC) is an electrochemical device that converts chemical to electrical energy. It is usually based around an oxide conducting ceramic electrolyte that requires temperatures above 800°C to operate. There are many advantages to lowering this operation temperature such as more gas sealing options and more efficient startup. One of the key limitations is in the transport of ions across the electrolyte. The most common electrolyte material used is Yttria-Stabilized Zirconia (YSZ). The ionic conductivity can be greatly affected by grain boundaries, dislocations, and point defects. In this study, dislocations were introduced by heavy ion irradiation. Irradiation with Xe+ or Ar+ produced a large number of point defects and dislocations via a mechanism similar to Frank partial dislocation formation. The dislocation density was on the order of 1012/cm2 and the Burgers vector was 1/2<110>. Heat treatment at temperatures from 800-1400°C changed the defect structure, eliminated point defects, and allowed dislocations to react and grow. Thin films of YSZ were deposited on silicon substrates using pulsed laser deposition (PLD). Films deposited on a metallized substrate were polycrystalline while films deposited directly onto conductive silicon could be epitaxially grown. Ion irradiation caused the film conductivity to drop by a factor of 2-3 due to additional point defects in the film. Heat treatment removed these point defects allowing the conductivity to recover. A novel method was developed to produce freestanding YSZ membranes without a silicon substrate by using the Focused Ion Beam (FIB). Thick, single-crystal YSZ pieces were thinned using in-situ X-Ray Energy Dispersive Spectroscopy (EDS) for end point detection. The final membranes were single crystal, less than 350nm thick, and pinhole free. IV curves and impedance measurements were made after irradiation and heat treatment. The conductivity showed similar trends to the PLD deposited thin films. In addition to the ohmic losses from the electrolyte, ion implantation also affected the activation losses of the electrode. Single crystal electrolytes were implanted with various species. The exchange current density improved by an order of magnitude following irradiation with Na+ and Xe+ on the cathode side.

Cheng, Jeremy

43

Thermal processes in multilayer second-generation HTSC under swift heavy-ion irradiation  

NASA Astrophysics Data System (ADS)

On the basis of the thermal spike model, the estimations with regard to tapes of the second-generation Ag/YBaCuO/MgO/Hastelloy HTSC under irradiation with Ar, Kr, and Xe ions of an energy of about 1.2 MeV/amu have been carried out. The results have been compared with the available experimental data. In addition, the possibility of processes such as melting, recrystallization, amorphization, and other phase transitions in multilayer structures under ion irradiation has been studied.

Didyk, A. Yu.; Semina, V. K.; Hofman, A.; Mikhailova, G. N.; Troitskij, A. V.; Antonova, L. Kh.

2013-09-01

44

Theoretical prediction of XRgCO(+) ions (X = F, Cl, and Rg = Ar, Kr, Xe).  

PubMed

In this work we have predicted novel rare gas containing cationic molecules, XRgCO(+) (X = F, Cl and Rg = Ar, Kr, Xe) using ab initio quantum chemical methods. Detail structural, stability, vibrational frequency, and charge distribution values are reported using density functional theory, second-order Møller-Plesset perturbation theory, and coupled-cluster theory based methods. These ions are found to be metastable in nature and exhibit a linear geometry with C?v symmetry in their minima energy structures, and the nonlinear transition state geometries are associated with Cs symmetry. Except for the two-body dissociation channel (Rg + XCO(+)), these ions are stable with respect to all other dissociation channels. However, the connecting transition states between the above-mentioned two-body dissociation channel products and the predicted ions are associated with sufficient energy barriers, which restricts the metastable species to transform into the global minimum products. Thus, it may be possible to detect and characterize these metastable ions using an electron bombardment technique under cryogenic conditions. PMID:24295279

Manna, Debashree; Ghosh, Ayan; Ghanty, Tapan K

2013-12-27

45

Multifragmentation in intermediate energy {sup 129}Xe-induced heavy-ion reactions  

SciTech Connect

The {sup 129}Xe-induced reactions on {sup nat}Cu, {sup 89}Y, {sup 165}Ho, and {sup 197}Au at bombarding energies of E/A = 40 & 60 MeV have been studied theoretically and experimentally in order to establish the underlying mechanism of multifragmentation at intermediate energy heavy-Ion collisions. Nuclear disks formed in central heavy-ion collisions, as simulated by means of Boltzmann-like kinetic equations, break up into several fragments due to a new kind of Rayleigh-like surface instability. A sheet of liquid, stable in the limit of non-interacting surfaces, is shown to become unstable due to surface-surface interactions. The onset of this instability is determined analytically. A thin bubble behaves like a sheet and is susceptible to the surface instability through the crispation mode. The Coulomb effects associated with the depletion of charges in the central cavity of nuclear bubbles are investigated. The onset of Coulomb instability is demonstrated for perturbations of the radial mode. Experimental intermediate-mass-fragment multiplicity distributions for the {sup 129}Xe-induced reactions are shown to be binomial at each transverse energy. From these distributions, independent of the specific target, an elementary binary decay probability p can be extracted that has a thermal dependence. Thus it is inferred that multifragmentation is reducible to a combination of nearly independent emission processes. If sequential decay is assumed, the increase of p with transverse energy implies a contraction of the emission time scale. The sensitivity of p to the lower Z threshold in the definition of intermediate-mass-fragments points to a physical Poisson simulations of the particle multiplicities show that the weak auto-correlation between the fragment multiplicity and the transverse energy does not distort a Poisson distribution into a binomial distribution. The effect of device efficiency on the experimental results has also been studied.

Tso, Kin

1996-05-01

46

Tracing electron-ion recombination in nanoplasmas produced by extreme-ultraviolet irradiation of rare-gas clusters.  

PubMed

We investigate electron-ion recombination in nanoplasmas produced by the ionization of rare-gas clusters with intense femtosecond extreme-ultraviolet (XUV) pulses. The relaxation dynamics following XUV irradiation is studied using time-delayed 790-nm pulses, revealing the generation of a large number of excited atoms resulting from electron-ion recombination. In medium-sized Ar-Xe clusters, these atoms are preferentially created in the Xe core within 10 ps after the cluster ionization. The ionization of excited atoms serves as a sensitive probe for monitoring the cluster expansion dynamics up to the ns time scale. PMID:25014813

Schütte, B; Campi, F; Arbeiter, M; Fennel, Th; Vrakking, M J J; Rouzée, A

2014-06-27

47

Xenon-nitrogen chemistry: gas-phase generation and theoretical investigation of the xenon-difluoronitrenium ion F2N-Xe+.  

PubMed

The xenon-difluoronitrenium ion F(2)N-Xe(+) , a novel xenon-nitrogen species, was obtained in the gas phase by the nucleophilic displacement of HF from protonated NF(3) by Xe. According to Møller-Plesset (MP2) and CCSD(T) theoretical calculations, the enthalpy and Gibbs energy changes (?H and ?G) of this process are predicted to be -3 kcal mol(-1) . The conceivable alternative formation of the inserted isomers FN-XeF(+) is instead endothermic by approximately 40-60 kcal mol(-1) and is not attainable under the employed ion-trap mass spectrometric conditions. F(2)N-Xe(+) is theoretically characterized as a weak electrostatic complex between NF(2)(+) and Xe, with a Xe-N bond length of 2.4-2.5 Å, and a dissociation enthalpy and free energy into its constituting fragments of 15 and 8 kcal mol(-1), respectively. F(2)N-Xe(+) is more fragile than the xenon-nitrenium ions (FO(2)S)(2)NXe(+), F(5)SN(H)Xe(+), and F(5)TeN(H)Xe(+) observed in the condensed phase, but it is still stable enough to be observed in the gas phase. Other otherwise elusive xenon-nitrogen species could be obtained under these experimental conditions. PMID:21826753

Operti, Lorenza; Rabezzana, Roberto; Turco, Francesca; Borocci, Stefano; Giordani, Maria; Grandinetti, Felice

2011-09-12

48

Microstructure of ion irradiated ceramic insulators  

NASA Astrophysics Data System (ADS)

Cross-section transmission electron microscopy was utilized to examine the radiation-induced microstructural changes in Al 2O 3, MgO, Si 3N 4 and MgAl 2O 4 after irradiation with a wide variety of energetic ion beams. The relative influence of ionizing and displacive radiation was studied by systematically varying the mass and energy of the bombarding ions between 1 MeV H + and 4 MeV Zr 3+ ions. The measured ion ranges were between 1 and 15% greater than the ranges calculated by the TRIM code, with the largest discrepancies occurring for intermediate mass ions. The implanted ions exerted a strong influence on the overall microstructural evolution of the irradiated ceramics. Numerous microstructural features (e.g., amorphization, colloids) were produced in the implanted ion regions which could not be produced in irradiated regions that were well separated from the implanted ions. The microstructural evolution in regions well separated from the implanted ions was found to depend strongly on the mass and energy of the bombarding ion. Light ion irradiation produced a significant enhancement in point defect diffusion (evidenced by defect-free zones at the surface and adjacent to internal defect sinks) compared to heavy ion irradiation at the same damage rate. Similarly, irradiation with a given ion at a higher flux generally produced an increased amount of observable diffusion. In some cases such as 1 MeV proton irradiation, observable defect clusters did not form. This suppression in defect cluster formation may be due to the high amount of point defect recombination associated with ionization enhanced diffusion that occurs during energetic light ion irradiation.

Zinkle, S. J.

1994-06-01

49

Study on the behavior of oxygen atoms in swift heavy ion irradiated CeO2 by means of synchrotron radiation X-ray  

E-print Network

on cerium dioxide (CeO2), CeO2 sintered pellets were irradiated with 200 MeV Xe ions at room temperature1 Study on the behavior of oxygen atoms in swift heavy ion irradiated CeO2 by means of synchrotron Institute of Electric Power Industry, Komae, Tokyo, 201-8511, Japan Keywords:, CeO2, Swift heavy ion

Paris-Sud XI, Université de

50

Porous structure formation in ion irradiated germanium  

NASA Astrophysics Data System (ADS)

The ion beam induced modification of amorphous germanium is characterised by the formation of voids close to the sample surface and the transformation into a sponge-like porous surface layer at high ion fluences. This extreme structural modification of the sample surface is independent of the (heavy) ion species used and accompanied by a strong volume expansion. Nevertheless, recently it was demonstrated that buried voids (and buried sponge-like layers) can be formed in the depth of the projected ion range, however, only for the irradiation with I-ions at high ion fluences. Thus, the ion species and their chemical properties seem to play an important role in the structural modification around the projected ion range. In this paper we investigate the influence of the ion species on the ion beam induced void formation in Ge for room temperature irradiation with 380 keV I- and Au-ions as a function of the ion fluence. Independent of the ion species, a strong volume expansion is observed caused by void formation and the transformation into a sponge-like porous surface layer. For both ion species used, the final porous layers are structurally identical as established by cross section and plan view electron microscopy investigations. Further ion irradiation of the sponge-like porous structure, however, leads to significant differences in the ion beam induced structural evolution. For the Au-ion irradiation the porous layer remains nearly unchanged, whereas for the irradiation with I-ions a transformation from sponge-like to netlike porous layers occurs which is accompanied again by an extreme volume expansion. The underlying mechanism will be discussed based on chemical properties of the implanted ions.

Steinbach, T.; Wesch, W.

2014-01-01

51

Swift heavy ion irradiation reduces porous silicon thermal conductivity  

NASA Astrophysics Data System (ADS)

While the electrical conductivity of semiconductors can be easily changed over order of magnitudes (8 in silicon) by playing on the doping, the thermal conductivity (TC) control is a challenging issue. Nevertheless, numerous applications require TC control in Si down to 1 W m-1 K-1. Among them, there are thermal insulation requirements in MEMS, thermal management issues in 3D packaging or TC reduction for thermoelectric applications. Towards this end, the formation of nanoporous Si by electrochemical anodisation is efficient. Nevertheless, in this case the material is too fragile for MEMS application or even to withstand CMOS technological processes. In this work, we show that ion irradiation in the electronic regime is efficient for reducing TC in meso-porous Si (PSi), which is more mechanically robust than the nanoporous PSi. We have studied three different mass to energy ratios (238U at 110 MeV and 130Xe at 91 MeV and 29 MeV) with fluences ranging from 1012 cm-2 to 7 × 1013 cm-2. The sample properties, after irradiation, have been measured by infrared spectroscopy, Raman spectroscopy and scanning electron microscopy. The TC has been measured using scanning thermal microscopy. Although, bulk Si is insensitive to ion interaction in the electronic regime, we have observed the amorphisation of the PSi resulting in a TC reduction even for the low dose and energy. For the highest irradiation dose a very important reduction factor of four was obtained.

Massoud, M.; Canut, B.; Newby, P.; Frechette, L.; Chapuis, P. O.; Bluet, J. M.

2014-12-01

52

TEM, XRD and nanoindentation characterization of Xenon ion irradiation damage in austenitic stainless steels  

NASA Astrophysics Data System (ADS)

Cross-sectional and bulk specimens of a 20% cold-worked 316 austenitic stainless steel (CW 316 SS) has been characterized by TEM, XRD and nanoindentation to determine the microstructural evolution and mechanical property changes of 316 SS after irradiation with 7 MeV Xe26+ ions. TEM results reveal the presence of dislocation loops with a number density of approximately 3 × 1022 m-3 and sizes between 3 to 10 nm due to the collapse of vacancy rich cores inside displacement cascades. Peak broadening observed in XRD diffraction patters reveal systematic changes to lattice parameters due to irradiation. The calculated indentation values in irradiated 316 SS were found to be much higher in comparison to the unirradiated specimen, indicating the dose dependent effect of irradiation on hardness. The relationship between irradiation induced microstructural evolution and the changes to the mechanical properties of CW 316 SS are discussed in the context of fluence and irradiation temperature.

Huang, H. F.; Li, J. J.; Li, D. H.; Liu, R. D.; Lei, G. H.; Huang, Q.; Yan, L.

2014-11-01

53

Heavy Ion Irradiated Ferromagnetic Films: The Cases of Cobalt and Iron  

NASA Astrophysics Data System (ADS)

Polycrystalline, e-gun deposited Co, Fe and Co/Fe films, tens of nanometers thick, have been irradiated with Ne, Kr, Xe and/or Fe ions to fluences of up to 5 × 1016 ions/cm2. Changes in the magnetic texture induced by the implanted ions have been measured by means of hyperfine methods, such as Magnetic Orientation Mössbauer Spectroscopy (Fe), and by Magneto-Optical Kerr Effect and Vibrating Sample Magnetometry. In Co and CoFe an hcp ? fcc phase transition has been observed under the influence of Xe-ion implantation. For 1016 Xe-ions/cm2, ion beam mixing in the Co/Fe system produces a soft magnetic material with uniaxial anisotropy. The effects have been correlated with changes in the microstructure as determined via X-ray diffraction. The influences of internal and external strain fields, an external magnetic field and pre-magnetization have been studied. A comprehensive understanding of the various effects and underlying physical reasons for the modifications appears to emerge from these investigations.

Lieb, K. P.; Zhang, K.; Müller, G. A.; Gupta, R.; Schaaf, P.

2005-01-01

54

Dissolution of Olivine Promoted by Ion Irradiation  

NASA Astrophysics Data System (ADS)

Recent laboratory simulations of ion irradiation effects on planetary minerals show changes in the surface composition of surfaces that are different depending on whether the analysis is done in-situ (without removing the sample from vacuum) or ex-situ using an electron microscope. We found that olivine samples that have been irradiated by keV ions show preferential loss of magnesium when exposed to water. Irradiations were done with 4 keV argon ions to fluences between 1015 and 1018 ions/cm2. Soak times in high purity water ranged from minutes to days, and exhibit the same degree of Mg depletion, independent of soak time. The concentration of magnesium on the surface of irradiated natural olivine decreases by 40% upon contact with water, as measured with x-ray photoelectron spectroscopy. This finding is important for laboratory simulations of regolith processes and for establishing procedures for the handling of irradiated samples, including those from sample return missions.

Cantando, E. D.; Dukes, C. A.; Baragiola, R. A.

2006-12-01

55

Swift heavy ion irradiation of ZnO nanoparticles embedded in silica: Radiation-induced deoxidation and shape elongation  

SciTech Connect

ZnO nanoparticles (NPs) embedded in amorphous SiO{sub 2} were irradiated with 200 MeV Xe{sup 14+} swift heavy ions (SHIs) to a fluence of 5.0 × 10{sup 13} ions/cm{sup 2}. Optical linear dichroism was induced in the samples by the irradiation, indicating shape transformation of the NPs from spheres to anisotropic ones. Transmission electron microscopy observations revealed that some NPs were elongated to prolate shapes; the elongated NPs consisted not of ZnO but of Zn metal. The SHI irradiation induced deoxidation of small ZnO NPs and successive shape elongation of the deoxidized metal NPs.

Amekura, H.; Tsuya, D.; Mitsuishi, K.; Nakayama, Y. [National Institute for Materials Science (NIMS), Tsukuba, Ibaraki 305-0003 (Japan)] [National Institute for Materials Science (NIMS), Tsukuba, Ibaraki 305-0003 (Japan); Okubo, N.; Ishikawa, N. [Japan Atomic Energy Agency (JAEA), Tokai, Ibaraki (Japan)] [Japan Atomic Energy Agency (JAEA), Tokai, Ibaraki (Japan); Singh, U. B.; Khan, S. A.; Avasthi, D. K. [Inter-University Accelerator Centre (IUAC), New Delhi (India)] [Inter-University Accelerator Centre (IUAC), New Delhi (India); Mohapatra, S. [Guru Gobind Singh Indraprastha University, New Delhi (India)] [Guru Gobind Singh Indraprastha University, New Delhi (India)

2013-11-11

56

Ion irradiation-induced diffusion in bixbyite-fluorite related oxides: Dislocations and phase transformation  

NASA Astrophysics Data System (ADS)

Ion-irradiation induced diffusion and the phase transformation of a bixbyite-fluorite related rare earth oxide thin films are studied. This work is focused on yttrium sesquioxide, Y2O3, thin films deposited on Si (1 0 0) substrates using the ion beam sputtering technique (IBS). As-deposited samples were annealed ant then irradiated at cryogenic temperature (80 K) with 260 keV Xe2+ at different fluences. The irradiated thin oxide films are characterized by X-ray diffraction. A cubic to monoclinic phase transformation was observed. Analysis of this phenomenon is done in terms of residual stresses. Stress measurements as a function of irradiation fluences were realised using the XRD-sin2? method. Stress evolution and kinetic of the phase transformation are compared and leads to the role-played by the nucleation of point and extended defects.

Rolly, Gaboriaud; Fabien, Paumier; Bertrand, Lacroix

2014-05-01

57

Irradiation effect of swift heavy ion for Zr50Cu40Al10 bulk glassy alloy  

NASA Astrophysics Data System (ADS)

It has been reported that heavy ion irradiation causes softening in some cases of Zr-based bulk metallic glass alloys. However, the fundamental mechanisms of such softening have not been clarified yet. In this study, Zr50Cu40Al10 bulk glassy alloys were irradiated with heavy ions of 10 MeV I at room temperature. The maximum fluence was 3 × 1014 ions/cm2. The positron annihilation measurements have performed before and after irradiation to investigate changes in free volume. We discuss the relationship between the energy loss and local open volume change after 10 MeV I irradiation compared with those obtained for 200 MeV Xe and 5 MeV Al. The energy loss analysis in ion irradiation for the positron lifetime has revealed that the decreasing trend of positron lifetime is well expressed as a function of total electronic energy deposition rather than total elastic energy deposition. It means that the positron lifetime change by the irradiation has a relationship with the inelastic collisions with electrons during heavy ion irradiation.

Onodera, Naoto; Ishii, Akito; Ishii, Kouji; Iwase, Akihiro; Yokoyama, Yoshihiko; Saitoh, Yuichi; Ishikawa, Norito; Yabuuchi, Atsushi; Hori, Fuminobu

2013-11-01

58

Double-electron removal from H2 by slow, highly charged Xe23+ ions  

NASA Astrophysics Data System (ADS)

A five-body classical trajectory Monte Carlo model has been used to study double-electron removal from H2 by collisions with highly charged ions. The final-state correlations between ionized protons and projectile are calculated for Xe23+ impact on H2 at collision energies ranging from 2.6 eV u-1 to 2.6 keV u-1. In the centre-of-mass frame of the recoiling protons, as the projectile energy decreases the proton energy distribution broadens considerably and also shifts to lower energies relative to that for an isolated molecule Franck-Condon transition. At low collision energies the protons are found to be scattered to the forward direction with large transverse momenta opposite to that of the projectile. The strong forward momenta are a signature of three-body dynamics with the protons Coulomb exploding against the projectile on the incoming portion of the trajectory. Investigation of the centre-of-mass momenta of the protons reveals a significant anisotropy of the proton angular distributions. At the lowest collision energies, there is a strong preference for the protons to be aligned parallel to the projectile direction. This behaviour, combined with their low centre-of-mass energies, implies that the protons are formed along the electric field vector of the incoming projectile concurrent with stretching of the molecular bond. The bond stretching is important only when the collision time is long (tens of femtoseconds) compared with the dissociation time of the molecule.

Olson, R. E.; Feeler, C. R.

2001-04-01

59

Fragmentation of DNA components by hyperthermal heavy ion (Ar+ and Xe+) impact in the condensed phase  

NASA Astrophysics Data System (ADS)

The overriding environmental factor that presently limits human endeavors in space is exposure to heavy ion radiation. While knowledge of its damage to living tissue is essential for radiation protection and risk estimates for astronauts, very little data exists at the molecular level regarding the nascent DNA damage by the primary particle track, or by secondary species during subsequent reaction cascades. This persistent lack of a basic understanding of nascent damage induced by such low dose, high LET radiation, introduces unacceptable errors in radiation risk estimates (based mainly on extrapolation from high dose, low LET radiation), particularly for long term exposure. Mutagenic effects induced by heavy ion radiation to cells are largely due to DNA damage by secondary transient species, i.e. secondary ballistic ions, electrons and radicals generated along the ion tracks; the secondary ions have hyperthermal energies up to several 100 eV, which they will deposit within a few nm in the surrounding medium; thus their LET is very high, and yields lethal clustered DNA lesions. We present measurements of molecular damage induced in films of DNA components by ions with precisely such low energies (1-100 eV) and compare results to conventional electron impact measurements. Experiments are conducted in UHV using a mass selected low energy ion source, and a high-resolution quadrupole MS to monitor ion yields desorbing from molecular films. Among the major fragments, NH4 + is identified in the desorption mass spectra of irradiated films of Adenine, Guanine, Cytosine, indicating efficient deamination; in cells this results in pre-mutagenic lesions. Experiments with 5-amino-Uracil, and comparison to previous results on uracil and thymine show that deamination is a key step in the NH4 + fragment formation. For Adenine, we also observe formation of amine aducts in the films, viz. amination of Adenine, and global fragmentation in all ion impact mass spectra, attributed mainly to kinetic & potential ion scattering.[Funded by NSERC and the Canadian Space Agency].

Sarabipour, Sarvenaz; Sarvenaz Sarabipour, Ms; Michaud, Marc; Deng, Zongwu; Huels, Michael A.

60

High energy heavy ion irradiation effects in MgO?MgFe 2O 4 ceramics  

NASA Astrophysics Data System (ADS)

Magnesium oxide single crystals containing magnesioferrite precipitates (MgFe 2O 4) have been obtained by thermal annealing at 1073 K of MgO single crystals implanted with 6 × 10 16 100 keV 57Fe ions cm -2. The size of the aggregates ranges from 20 to 80 nm. These samples have been irradiated at GANIL with 3.4 GeV Xe ions at 10 12 ions cm -2 fluence. The effects of these particles have been investigated by transmission electron microscopy (TEM) and conversion electron Mössbauer spectroscopy (CEMS). TEM observations reveal damaged regions inside the precipitates. The diameter of these zones ranges from 4 to 6 nm and their density roughly corresponds to the xenon fluence. The CEMS spectra show an increase of the paramagnetic component due to Fe 3+ ions on the cost of the magnetically ordered components due to Fe 3+ ions in octahedral and tetrahedral sites of the MgFe 2O 4 spinel structure. This is in agreement with the TEM observations and can be due to a local modification of the spinel structure in the damaged regions. Such irradiation defects are tracks induced by the very high electronic stopping power [ ( {- dE }/{dx }) e ? 1 keVÅ-1] of the Xe ions.

Treilleux, M.; Fuchs, G.; Perez, A.; Balanzat, E.; Dural, J.

1988-05-01

61

Slow ion irradiation of sugar: astrobiological implications  

Microsoft Academic Search

As a result of irradiation by slow hydrogen and argon ions of saccharose, humic films having a fractal nature were produced. The use of hydrogen ions simulated roughly the interaction of low-energy solar wind protons with interplanetary dust grains which, in addition to organic and mineral dust, may include clumps of viable bacteria. The type of film generated by this

M. Tuleta; L. Gabla; N. C. Wickramasinghe

2009-01-01

62

High energy heavy ion irradiation in semiconductors  

NASA Astrophysics Data System (ADS)

Pd/n-Si and Pd/n-GaAs devices have been irradiated from high energy (˜100 MeV) heavy ions of Au 7+ (gold) and Si 7+ (silicon) to study the irradiation effects in these junction devices on semiconductor substrates. The devices have been characterized from I-V and C-V studies for electronic flow characterization. It has been found that the devices become high resistive on the irradiation and the substrates change the conductivity type from n- to p- on the irradiation of fluence of ˜10 12-10 13 ions/cm 2. The change in conductivity type has been understood as a result of creation of deep acceptors on the irradiation.

Srivastava, P. C.; Pandey, S. P.; Sinha, O. P.; Avasthi, D. K.; Asokan, K.

63

Synthesis of Diamond-Like Carbon Films Using a Bi-Modal Sputter Deposition with xe Ions  

NASA Astrophysics Data System (ADS)

An alternative approach to a sputtering process was examined where a single incident beam of Xe ions was used to simultaneously sputter a carbon target and bombard a growing film. The hypothesis that by positioning a substrate at grazing angles to the central axis of the ion beam, the additional energy provided will be beneficial to the formation of sp3 bonding. Amorphous carbon (a-C) and diamond-like carbon (DLC) films were synthesized by sputtering a graphite target from a Kaufmann-type ion source. Experimental results revealed that when a substrate was placed at grazing angles due to a secondary resputtering process, it was not possible to fabricate DLCs but only sp2-rich polymeric a-C. For DLC synthesis the optimal angles of the target and the substrate to the ion flux were found to be 30° and 0°, respectively, and the ion energies of 0.8-1 keV.

Rybachuk, Maksym; Bell, John M.

64

Damage accumulation in gallium nitride irradiated with various energetic heavy ions  

NASA Astrophysics Data System (ADS)

In this work a study of damage production in gallium nitride via elastic collision process (nuclear energy deposition) and inelastic collision process (electronic energy deposition) using various heavy ions is presented. Ordinary low-energy heavy ions (Fe + and Mo + ions of 110 keV), swift heavy ions ( 208Pb 27+ ions of 1.1 MeV/u) and slow highly-charged heavy ions (Xe n+ ions of 180 keV) were employed in the irradiation. Damage accumulation in the GaN crystal films as a function of ion fluence and temperature was studied with RBS-channeling technique, Raman scattering technique, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). For ordinary low-energy heavy ion irradiation, the temperature dependence of damage production is moderate up to about 413 K resulting in amorphization of the damaged layer. Enhanced dynamic annealing of defects dominates at higher temperatures. Correlation of amorphization with material decomposition and nitrogen bubble formation was found. In the irradiation of swift heavy ions, rapid damage accumulation and efficient erosion of the irradiated layer occur at a rather low value of electronic energy deposition (about 1.3 keV/nm 3), which also varies with irradiation temperature. In the irradiation of slow highly-charged heavy ions (SHCI), enhanced amorphization and surface erosion due to potential energy deposition of SHCI was found. It is indicated that damage production in GaN is remarkably more sensitive to electronic energy loss via excitation and ionization than to nuclear energy loss via elastic collisions.

Zhang, C. H.; Song, Y.; Sun, Y. M.; Chen, H.; Yang, Y. T.; Zhou, L. H.; Jin, Y. F.

2007-03-01

65

Effects of Ion Irradiation on Ice Porosity  

NASA Astrophysics Data System (ADS)

Vapor-deposited water ice is believed to be present in astronomical environments such as interstellar grains, planetary rings, comets, and icy satellites. Some salient properties are its amorphous molecular structure and its microporosity, which determines its capacity to absorb gas. Since in most astronomical environments these ices are subject to radiation it is important to determine the effect of radiation on porosity. We have studied in the laboratory the effects of ion irradiation on the porosity of amorphous ice using ultraviolet-visible spectroscopy and infrared spectroscopy. Our findings indicate that ion irradiation compacts porous ice. The density of the ice film rises asymptotically to a saturation value with increasing ion fluence. Irradiation also decreases the intensity of the ~ 2.7 ?m absorption features assigned to the O-H stretch of dangling molecules present in porous ice film. However, we find that the dangling bond features decrease at a faster rate than the ice porosity. To investigate this contrasting behavior, we performed gas adsorption/desorption experiments on ice films irradiated to different fluences of 100 keV Ar+ ions. We will discuss how these measurements can be used to obtain pore size distributions and changes induced via ion irradiation. Finally, our results open the possibility that ices can remain porous, even if the dangling bond features are not present, which is of particular interest in colder regions such as interstellar ices.

Raut, U.; Teolis, B. D.; Loeffler, M. J.; Fama, M.; Vidal, R. A.; Baragiola, R. A.

2006-05-01

66

Effects of swift heavy ion irradiation parameters on optical properties of muscovite mica  

NASA Astrophysics Data System (ADS)

Muscovite mica sheets with a thickness of 25 ?m were irradiated by various kinds of swift heavy ions (Sn, Xe and Bi) in HIRFL (Heavy Ion Research Facility in Lanzhou). The fluences ranged from 1 × 1010 to 8 × 1011 ions/cm2 were applied. The electronic energy loss (dE/dx)e in mica was changed from 14.7 to 31.2 keV/nm. The band gaps and Urbach energy of pristine and irradiated mica were analyzed by ultraviolet-visible spectroscopy (UV-Vis). A red shift of the absorption edge was found in the absorption spectra of muscovite mica irradiated by ions with increasing (dE/dx)e. The results show that the chemical bonds between Tetrahedral-Octahedral-Tetrahedral (TOT) layers of mica were destroyed by ion irradiation. With increasing (dE/dx)e and fluences, the band gaps became narrow and the Urbach energy increased. It suggests that the amount of defects and the proportion of amorphous structure were increased in mica irradiated with increasing (dE/dx)e and fluences.

Zhang, S. X.; Liu, J.; Zeng, J.; Song, Y.; Mo, D.; Yao, H. J.; Duan, J. L.; Sun, Y. M.; Hou, M. D.

2015-01-01

67

Fe K-shell ionization induced by Xe20+ ions near the Bohr velocity  

NASA Astrophysics Data System (ADS)

Fe K-shell ionization cross sections by 2.4-6.0 MeV Xe20+ impact were investigated. It was found that the BEA model corrected both by the Coulomb repulsion and the effective nuclear charge gives the best agreement with the experimental data.

Xianming, Zhou; Yongtao, Zhao; Rui, Cheng; Jieru, Ren; Shidong, Liu; Yu, Lei; Yuanbo, Sun; Yuyu, Wang; Ge, Xu; Guoqing, Xiao

2014-04-01

68

Early and Late Responses to Ion Irradiation  

NASA Astrophysics Data System (ADS)

Early and late responses to ion beam therapy (IBT) are the result of complex interactions between host, dose volume, and radiobiological factors. Our understanding of these early and late tissue responses has improved greatly with the accumulation of laboratory and clinical experience with proton and heavy ion irradiation. With photon therapy becoming increasingly conformal, many concepts developed for 3D conformal radiotherapy and intensity modulated radiation therapy with photons are also applicable to IBT. This chapter reviews basic concepts and experimental data of early and late tissue responses to protons and ions.

Schulte, Reinhard; Ling, Ted

69

Amorphization of crystalline Si due to heavy and light ion irradiation.  

SciTech Connect

The formation of amorphous silicon in crystalline silicon by bombardment with light (Si) and heavy (Xe) ions has been investigated by transmission electron microscopy with in situ ion irradiation. Experiments have been carried out at room temperature and low temperature (50 K) and the results are compared to a simple numerical model for amorphization. The results indicate that the amorphization mechanisms for both irradiations are heterogeneous in nature and that numerous overlaps of the collision cascade are generally required to render the crystal amorphous. Following from this, the nature of the material within the confines of collision cascades will be discussed and it will be shown that the individual cascade volume is not necessarily amorphous as previously described in the scientific literature but contains varying degrees of damage depending on the energy deposited within the cascade.

Edmondson, P. D.; Riley, D. J.; Birtcher, R. C.; Donnelly, S. E.; Materials Science Division; Univ. of Salford

2009-08-01

70

Amorphization of crystalline Si due to heavy and light ion irradiation  

SciTech Connect

The formation of amorphous silicon in crystalline silicon by bombardment with light (Si) and heavy (Xe) ions has been investigated by transmission electron microscopy with in situ ion irradiation. Experiments have been carried out at room temperature and low temperature (50 K) and the results are compared to a simple numerical model for amorphization. The results indicate that the amorphization mechanisms for both irradiations are heterogeneous in nature and that numerous overlaps of the collision cascade are generally required to render the crystal amorphous. Following from this, the nature of the material within the confines of collision cascades will be discussed and it will be shown that the individual cascade volume is not necessarily amorphous as previously described in the scientific literature but contains varying degrees of damage depending on the energy deposited within the cascade.

Edmondson, P. D.; Riley, D. J.; Donnelly, S. E. [Institute for Materials Research, University of Salford, Manchester M5 4WT (United Kingdom); Birtcher, R. C. [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States)

2009-08-15

71

Ion irradiation effects in natural garnets: Comparison with zircon  

E-print Network

Ion irradiation effects in natural garnets: Comparison with zircon S. Utsunomiya, L.M. Wang, R ; Z ¼ 8) under ion-beam irradiation was investigated in order to compare its radiation susceptibility during the ion irradiation at high temperature. This behavior may be related to the phase relations

Utsunomiya, Satoshi

72

Mutation induced with ion beam irradiation in rose  

NASA Astrophysics Data System (ADS)

The effects of mutation induction by ion beam irradiation on axillary buds in rose were investigated. Axillary buds were irradiated with carbon and helium ion beams, and the solid mutants emerged after irradiation by repeated cutting back. In helium ion irradiation, mutations were observed in plants derived from 9 buds among 56 irradiated buds in 'Orange Rosamini' and in plants derived from 10 buds among 61 irradiated buds in 'Red Minimo'. In carbon ion, mutations were observed in plants derived from 12 buds among 88 irradiated buds in 'Orange Rosamini'. Mutations were induced not only in higher doses but also in lower doses, with which physiological effect by irradiation was hardly observed. Irradiation with both ion beams induced mutants in the number of petals, in flower size, in flower shape and in flower color in each cultivar.

Yamaguchi, H.; Nagatomi, S.; Morishita, T.; Degi, K.; Tanaka, A.; Shikazono, N.; Hase, Y.

2003-05-01

73

Chromosomal instability induced by heavy ion irradiation  

NASA Technical Reports Server (NTRS)

PURPOSE: To establish the dose-response relationship for the induction of chromosomal instability in GM10115 cells exposed to high-energy iron ions (1 GeV/nucleon, mean LET 146 keV/microm) and gold ions (11 GeV/nucleon, mean LET 1450 keV/microm). Past work has established that sparsely ionizing X-rays can induce a long-lived destabilization of chromosomes in a dose-dependent manner at an incidence of approximately 3% per gray. The present investigation assesses the capacity of High-Z and High-energy (HZE) particles to elicit this same endpoint. MATERIALS AND METHODS: Clonal populations derived from single progenitor cells surviving heavy-ion irradiation were analyzed cytogenetically to identify those clones showing a persistent destablization of chromosomes. RESULTS: Dose-response data, with a particular emphasis at low dose (< 1.0 Gy), indicate a frequency of approximately 4% per gray for the induction of chromosomal instability in clones derived from single progenitor cells surviving exposure to iron ions. The induction of chromosomal instability by gold ions was, however, less responsive to applied dose, as the observed incidence of this phenotype varied from 0 to 10% over 1-8 Gy. Both iron and gold ions gave dose-dependent increases in the yield of chromosomal aberrations (both chromosome- and chromatid-type) measured at the first mitosis following irradiation, as well as shoulderless survival curves having D0=0.87 and 1.1 Gy respectively. CONCLUSIONS: Based on the present dose-response data, the relative biological effectiveness of iron ions is 1.3 for the induction of chromosomal instability, and this indicates that heavy ions are only slightly more efficient than X-rays at eliciting this delayed phenotype.

Limoli, C. L.; Ponnaiya, B.; Corcoran, J. J.; Giedzinski, E.; Morgan, W. F.

2000-01-01

74

Microstructure of Swift Heavy Ion Irradiated MgAl(Sub 2)O(Sub 4) Spinel  

SciTech Connect

Plan view and cross-section transmission electron microscopy was used to investigate the microstructure of magnesium aluminate spinel (MgAl{sub 2}O{sub 4}) following room temperature irradiation with either 430 MeV Kr, 614 MeV Xe, or 72 MeV I ions. The fluences ranged from 1 x 10{sup 16}/m{sup 2} (single track regime) to 1 x 10{sup 20}/m{sup 2}. Destruction of the ordered spinel crystal structure on both the anion and cation sublattices was observed in the ion tracks at low fluences. At intermediate fluences, the overlapping ion tracks induced the formation of a new metastable crystalline phase. Amorphization with a volumetric expansion of {approximately}35% was observed in spinel irradiated with swift heavy ions (electronic stopping powers >7 keV/nm) at fluences above 1 x 10{sup 19}/m{sup 2}. These results demonstrate that swift heavy ion radiation can induce microstructural changes not achievable with conventional elastic collision irradiation at comparable temperatures.

Matzke, H.; Skuratov, V.A.; Zinkle, S.J.

1998-11-30

75

Dependence of cross sections for multi-electron loss by 6 mev/amu xe18+ ions on target atomic number  

E-print Network

for multi-electron loss on target atomic number by using 6 MeV/amu Xe18+ ions and to compare the results with the n-body Classical Trajectory Monte Carlo calculations. A secondary objective of this project is to determine the extent to which the cross...

Peng, Yong

2004-09-30

76

I-Xe systematics in LL chondrites  

NASA Astrophysics Data System (ADS)

A stepwise heating analysis of Ar and Xe data from five neutron-irradiated whole rock LL chondrites (Soko Banja, Alta Ameen, Tuxtuac, Guidder, and Olivenza) is presented, emphasizing the complicated thermal history of ordinary chondrites. None of the present meteorites show a well-defined (Ar-40)-(Ar-39) apparent age plateau comprised of more than two release fractions. Most of the samples are found to yield well-defined high-temperature correlations between Xe-129/Xe-130 and Xe-128/Xe-130, and thus determinations of I-129/I-127 and Xe-129/Xe-130 at the time of isotopic closure for Xe. As in the case of other ordinary chondrites, the I-Xe systematics for LL chondrites correlate neither with a metamorphic grade nor with chronologies based opon other methods.

Bernatowicz, T. J.; Podosek, F. A.; Swindle, T. D.; Honda, M.

1988-05-01

77

Effects of swift heavy ions irradiation parameters on optical properties of muscovite mica  

E-print Network

Muscovite mica sheets with a thickness of 25 {\\mu}m were irradiated by various kinds of swift heavy ions (Sn, Xe and Bi) in HIRFL. The fluences ranged from 1$\\times$10^{10} ions/cm^2 to 8$\\times$10^{11} ions/cm^2. The electronic energy loss (dE/dx)_e was increased from 14.7 keV/nm to 31.2 keV/nm. The band gap and Urbach energy of pristine and irradiated mica were analyzed by ultraviolet- visible spectroscopy. Periodic fringes in long wave length of the absorption spectra caused by interference phenomenon, were disturbed as the (dE/dx)_e increased. It was suggested that the chemical bonds between Tetrahedral-Octohedral-Tetrahedral (TOT) layers of mica were destroyed. Thus the smooth surface was cleaved after irradiation. The band gap was narrowed down with the increasing (dE/dx)_e and fluences. The values of Urbach energy were increased as the (dE/dx)_e and fluences gradually increased. It was indicated that the amount of defects and the proportion of amorphous structure were increased in mica irradiated under...

Zhang, Sheng-Xia; Zeng, Jian; Song, Yin; Mo, Dan; Yao, Hui-Jun; Duan, Jing-Lai; Sun, You-Mei; Hou, Ming-Dong

2014-01-01

78

Mechanical properties of fluorite-related oxides subjected to swift ion irradiation: Pyrochlore and zirconia  

NASA Astrophysics Data System (ADS)

The modifications of the mechanical properties of related-fluorite oxides (cubic zirconia [c-ZrO 2] and pyrochlores [Gd 2(Ti 1-xZr x) 2O 7 with x = 0.5 and x = 1]) induced by swift heavy ion irradiation are investigated. Polycrystalline pellets of both materials were irradiated at room temperature with 940 MeV Pb or 870 MeV Xe ions at the GANIL accelerator in Caen at fluences ranging from 2 × 10 11 to 10 13 cm -2. Residual macroscopic stresses induced by irradiation were determined using X-ray diffraction and the sin 2? method. The microhardness and the fracture toughness of irradiated samples were studied by Vickers micro-indentation. Amorphization occurs in Gd 2TiZrO 7 and not in Gd 2Zr 2O 7 and c-ZrO 2. The mechanical behavior of materials is found to be closely related to the residual stresses induced in the surface layer by irradiation. Compressive stresses are generated in c-ZrO 2 and Gd 2TiZrO 7 (leading to an increase of fracture toughness), whereas tensile stresses (inducing a large decrease of fracture toughness) are observed in Gd 2Zr 2O 7 due to the lattice contraction related to a pyrochlore fluorite?transition.

Sattonnay, G.; Moll, S.; Desbrosses, V.; Menvie Bekale, V.; Legros, C.; Thomé, L.; Monnet, I.

2010-10-01

79

Effect of Ion Doping Process on Thin-Film Transistor Characteristics Using a Bucket-Type Ion Source and XeCl Excimer Laser Annealing  

NASA Astrophysics Data System (ADS)

The effect of the ion doping process on polysilicon thin-film transistor (TFT) characteristics was investigated using a bucket-type ion source and XeCl excimer laser annealing. Generally, as the acceleration voltage (Va) of phosphorous ions, the doping time (td) and the laser energy (Ea) for impurity activation increased, the field effect mobility (?) was increased and the leakage current (Ioff) was decreased. The conditions of Va from 1.5 to 2.0 kV, td from 10 s to 5 min, and Ea from 150 to 260 mJ/cm2 were found to enable TFT performance with ? of more than 20 cm2/Vs, threshold voltage of less than 5 V, and Ioff of less than 5× 10-11 A.

Aoyama, Takashi; Kawachi, Genshiro; Mochizuki, Yasuhiro; Suzuki, Takaya

1992-04-01

80

Unexpected transverse velocity component of Xe{sup +} ions near the exit plane of a Hall thruster  

SciTech Connect

The velocity component of singly charged xenon ions in a plane perpendicular to the thrust axis of the 1 kW-class PPS100-ML Hall effect thruster is deduced from laser induced fluorescence measurements on the 5d {sup 2}F{sub 7/2}{yields}6p {sup 2}D{sub 5/2}{sup 0} electronic transition at 834.72 nm. Measurements are carried out at several locations in the near field of the channel exhaust. Thruster operating parameters, such as magnetic field strength, discharge voltage, and xenon mass flow rate, are varied over a wide range. The initial aim of this work was to measure the azimuthal velocity of the ions due to their weak magnetic deflection. Surprisingly, experimental results cannot be explained by the one and only Lorentz force acting on Xe{sup +} ions. A realistic picture of the ion trajectory in the ExB drift plane is obtained when adding a velocity component directed toward the external cathode.

Bourgeois, G.; Mazouffre, S. [ICARE, CNRS, 1C Avenue de la Recherche Scientifique, 45071 Orleans (France); Sadeghi, N. [LSP, Joseph Fourier University and CNRS, 140 Ave. de la Physique, 38402 St. Martin d'Heres (France)

2010-11-15

81

Ion irradiated graphite exposed to fusion-relevant deuterium plasma  

NASA Astrophysics Data System (ADS)

Graphite samples were irradiated with 5 MeV carbon ions to simulate the damage caused by collision cascades from neutron irradiation in a fusion environment. The ion irradiated graphite samples were then exposed to a deuterium plasma in the linear plasma device, MAGPIE, for a total ion fluence of ?1 × 1024 ions m-2. Raman and near edge X-ray absorption fine structure (NEXAFS) spectroscopy were used to characterize modifications to the graphitic structure. Ion irradiation was observed to decrease the graphitic content and induce disorder in the graphite. Subsequent plasma exposure decreased the graphitic content further. Structural and surface chemistry changes were observed to be greatest for the sample irradiated with the greatest fluence of MeV ions. D retention was measured using elastic recoil detection analysis and showed that ion irradiation increased the amount of retained deuterium in graphite by a factor of four.

Deslandes, Alec; Guenette, Mathew C.; Corr, Cormac S.; Karatchevtseva, Inna; Thomsen, Lars; Ionescu, Mihail; Lumpkin, Gregory R.; Riley, Daniel P.

2014-12-01

82

Local brain heavy ion irradiation induced Immunosuppression  

NASA Astrophysics Data System (ADS)

Purpose: To investigate the long term effect of acute local brain heavy ion irradiation on the peripheral immune system in rat model. Methodology: Only the brain of adult male Wistar rats were radiated by heavy ions at the dose of 15 Gy. One, two and three months after irradiation, thymus and spleen were analyzed by four ways. Tunel assay was performed to evaluate the percentage of apoptotic cells in thymus and spleen, level of Inflammatory cytokines (IL-2, IL-6, SSAO, and TNF-?) was detected by ELISA assay, the differentiation of thymus T lymphocyte subsets were measured by flow cytometry and the relative expression levels of genes related to thymus immune cell development were measured by using quantitative real-time PCR. Results: Thymus and spleen showed significant atrophy from one month to three months after irradiation. A high level of apoptosis in thymus and spleen were obtained and the latter was more vulnerable, also, high level of inflammatory cytokines were found. Genes (c-kit, Rag1, Rag2 and Sca1) related to thymus lymphocytes’ development were down-regulated. Conclusion: Local area radiation in the rat brain would cause the immunosuppression, especially, the losing of cell-mediated immune functions. In this model, radiation caused inflammation and then induced apoptosis of cells in the immune organs, which contributed to immunosuppression.

Lei, Runhong; Deng, Yulin; Huiyang Zhu, Bitlife.; Zhao, Tuo; Wang, Hailong; Yu, Yingqi; Ma, Hong; Wang, Xiao; Zhuang, Fengyuan; Qing, Hong

83

Nanoindentation investigation of heavy ion irradiated Ti 3(Si,Al)C 2  

NASA Astrophysics Data System (ADS)

Because of good damage tolerance, thermal stability and interesting mechanical properties, Ti 3SiC 2, belonging to M n+1AX n phases, has been considered as a potential candidate material for applications in the future Gas Fast nuclear Reactors (GFR) such as components of fuel cladding working between 500 °C and 800 °C. However, the outstanding mechanical properties of Ti 3SiC 2 related to a layered microstructure could be impacted by irradiation. In this work, high energy Kr and Xe ion irradiated Ti 3Si 0.95Al 0.05C 2 and Ti 3Si 0.90Al 0.10C 2 samples, provided by IMR Shenyang, Chinese Academy of Science, were characterized by nanoindentation technique. After irradiation at room temperature, an increase in hardness with irradiation dose was highlighted. Nevertheless, some damage tolerance remained because of preservation of the typical MAX layered structure. Irradiations at 300 °C and 500 °C lead to less significant increase suggesting irradiation defect annealing. A complete recovery of the properties at 800 °C seems to be obtained.

Liu, X. M.; Le Flem, M.; Béchade, J. L.; Monnet, I.

2010-06-01

84

Microstructure and atomic disordering of magnesium aluminate spinel irradiated with swift heavy ions  

NASA Astrophysics Data System (ADS)

We have investigated the microstructure and atomic disordering of nearly stoichiometric magnesium aluminate spinel (MgO · 1.1Al 2O 3), irradiated with 200 MeV Xe 14+ ions ( Se = 25 keV/nm). Transmission electron microscopy techniques of bright-field (BF) and high-resolution (HR) imaging, as well as high angular resolution electron channeling X-ray spectroscopy (HARECXS) were employed for quantitative analysis of radiation-induced structural change. BF images of ion tracks show columnar dark contrast of ˜4 nm in diameter accompanying distinct black or white dots at the incident surface. Clear lattice fringes are observed in HR images even inside the ion tracks, indicating that the spinel crystals are not amorphized but partially disordered along the ion tracks. HARECXS analysis showed that cation disordering progresses successively with ion fluence, and the disordered regions are found to extend over 12.8 ± 0.9 nm in diameter for Al ions and 9.6 ± 0.6 nm for Mg ions along the ion tracks. This chemically disordered region is much larger than the strained volume detected by BF and HR images.

Yamamoto, T.; Shimada, M.; Yasuda, K.; Matsumura, S.; Chimi, Y.; Ishikawa, N.

2006-04-01

85

Atomic transport in metal/ceramic interfaces under heavy ion irradiation  

NASA Astrophysics Data System (ADS)

Ion beam mixing is a useful tool to modify the physical properties of interfaces in different materials. Metal/metal systems were extensively studied in the last decade. In the last few years research has been focused on the technologically more important metal/ceramic systems. In these systems, however, there is only limited knowledge on stability and diffusion processes under heavy ion irradiation. In order to collect more information about physical processes, which could be important for applications and in tailoring of interfaces, systematic ion beam mixing experiments on several bi-layer samples have been performed. Different oxide-ceramic substrates (MgO, Al 2O 3, SiO 2, ZrO 2) were covered by thin metallic films (Fe, Cu, Ni, Au, Ag) using a MBE set-up. Ion beam mixing experiments were performed at three different energies (150 keV, 4 and 12 MeV) with Ar-, Kr-and Xe-ions at different temperatures (77-673 K). Mixing behaviour was studied mainly by RBS measurements after the irradiation. The structure and topography of the films prior to and after irradiation were investigated by high resolution scanning electron microscopy (HRSEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). It was of special interest to determine the enhancement of the mixing rate compared to the ballistic mixing. This enhancement can be explained by thermal spikes (temperature independent effect) or by mobile defects produced by the heavy ions during irradiation and/or by chemical driving forces (temperature dependent effects).

Nagel, R.; Balogh, A. G.

86

Enhanced adhesion from high energy ion irradiation  

NASA Technical Reports Server (NTRS)

It has been found that the adhesion of thin metal films on insulators, semiconductors, and metals could be improved by subjecting the material to a high-energy ion bombardment. Griffith et al. (1982) have first suggested a use of this technique with insulators. The present investigation has the objective to determine the mechanism for the adhesion enhancement. A description is presented of a preliminary transmission electron microscopy (TEM) study of thinned bonded samples of silver on silicon using electron diffraction. It is found that irradiation of a variety of thin film-substrate combinations by heavy ion beams will provide a remarkable improvement in the adherence of the film. The evidence for the mechanism involved in the enhancement of adhesion is discussed.

Werner, B. T.; Vreeland, T., Jr.; Mendenhall, M. H.; Qui, Y.; Tombrello, T. A.

1983-01-01

87

Raman Scattering in Natural Diamond Crystals Implanted with High-Energy Ions and Irradiated with Fast Neutrons  

NASA Astrophysics Data System (ADS)

Raman scattering is studied in natural diamond crystals with radiation-induced defects produced by implantation of high energy Xe and Kr ions (ion kinetic energy >1 MeV/amu) and by irradiation with fast reactor neutrons (kinetic energy >100 keV). Confocal measurements of the Raman spectra along the surface of an oblique section of the ionimplanted diamonds are used to study the radiation damage profile. The evolution of the Raman scattering spectra with depth of the damaged layer in the ion-implanted diamonds, and as a function of annealing temperature of the neutron-irradiated diamond, is determined by spatial localization of phonons in the radiation disordered crystal lattice and by the formation of associations of intrinsic defects in the lattice.

Poklonskaya, O. N.; Vyrko, S. A.; Khomich, A. A.; Averin, A. A.; Khomich, A. V.; Khmelnitsky, R. A.; Poklonskia, N. A.

2015-01-01

88

Electron-emission processes in highly charged Ar and Xe ions impinging on highly ordered pyrolytic graphite at energies just above the kinetic threshold  

NASA Astrophysics Data System (ADS)

At keV energies, many electronic processes contribute to the emission of secondary electrons in the interaction of highly charged ions on surfaces. To unravel contributions resulting from isolated hollow atoms in front of the surface or embedded in the electron gas of the target, heavy highly charged Ar and Xe ions are collided on highly ordered pyrolytic graphite (HOPG). A light target material as HOPG assures straight-line trajectories in the subsurface range. By a systematic change of incidence angle and energy of low-charged Ar and Xe ions, the kinetic electron emission component is determined. Separating out the kinetic energy contribution for the highly charged ions yields pure potential-energy-driven secondary-electron yields. From these yields it is concluded that in contrast to metallic targets, only a small fraction of the secondary electrons stem from above the surface. The lack of above-surface emission is likely due to the semimetallic electronic structure of HOPG. The subsurface emission is found to scale with the increase in binding energy of the inner-shell hole when incrementing the charge state of the projectile Ar or Xe ions.

Bodewits, E.; Hoekstra, R.; Dobes, K.; Aumayr, F.

2014-11-01

89

Searching for the Mass of the Neutrino (Spectroscopy of Ba+ ions in Liquid ^136Xe)  

NASA Astrophysics Data System (ADS)

The goal of the Enriched Xenon Observatory (EXO) collaboration is to detect neutrino-less double beta decay using a ton size liquid ^136Xenon detector with zero background. Such detection can only be achieved if the daughter ^136Ba^+ ion that is present at decay site is tagged. The EXO collaboration is working towards several techniques to tag the Ba^+ ion. In-situ laser tagging of Ba^+ ions in a liquid xenon test apparatus is being developed at Colorado State University (CSU). Ba^+ ions are implanted in the liquid xenon by ablating a barium sample with a 1064nm Nd-YAG pulsed laser. In-situ laser tagging can only be accomplished if the spectroscopy of Ba^+ ions in liquid xenon is understood. This work's goal is to confirm the spectra of Ba+ ions in liquid xenon. The most recent results of the experiments at CSU will be presented.

Hall, Kendy; Benitez, Cesar; Fairbank, Bill

2009-10-01

90

Defect formation and accumulation in CeO2 irradiated with swift heavy ions  

NASA Astrophysics Data System (ADS)

We have investigated microstructure evolution in CeO2 irradiated with 210 MeV Xe ions by using transmission electron microscopy to gain the fundamental knowledge on radiation damage induced by fission fragments in nuclear fuel and transmutation target. Analysis on the accumulation of ion tracks has revealed an influence region to recover pre-existing core damage regions of ion tracks to be 8.4 nm in radius. Cross section observations showed that high-density electronic excitation induces both ion tracks and dislocation loops. At high fluences of 1.5 × 1019 and 1 × 1020 ions m-2, depth-dependent microstructure was developed with radiation-induced defects of ion tracks, dislocation loops (dot-contrast) and line dislocations. Formation of sub-divided small grains was found at shallow depth at a fluence of 1 × 1020 ions m-2. The microstructure evolution was discussed in terms of the accumulation of interstitials due to significant overlap of high density electronic excitation.

Yasuda, K.; Etoh, M.; Sawada, K.; Yamamoto, T.; Yasunaga, K.; Matsumura, S.; Ishikawa, N.

2013-11-01

91

Energy dependence of nanopillars formation on InSb semiconductor surfaces under gallium FIB and noble gas ions beam irradiation  

NASA Astrophysics Data System (ADS)

We have studied the formation and evolution of ion beam-induced pillars growth on InSb(0 0 1) surface through a comparison of irradiation with Ga (Focused Ion Beam) and noble gas ion (Ar, Kr, Xe) beams. Room temperature, normal incidence ion irradiation was carried out with the ion beam energy of 1-3 keV for noble gas and 3-30 keV for FIB Ga ions. The surface morphology of the developed structures and their chemical composition were investigated by means of scanning and transmission electron microscopy (SEM/TEM). We have examined the evolution from the initial flat InSb surface, through clusters formation, at initial stages of irradiation (ion beam fluence of 5 × 1016 ions/cm2), to the pillar structure formation at higher ion fluences (2.8 × 1017 ions/cm2), for both kinds of projectiles. The projectile ion energy dependence of the pillar size, height and density was studied for both kinds of ion species for the first time. It has been found that the pillar sizes and heights exhibit the power-law dependence on projectile energy with the same exponent for both kinds of the ion species. The TEM measurements uncovered crystalline InSb core of the pillar and In/Ga enriched amorphous tip and shell structure. We confirmed a universal mechanism of pillars formation based on redeposition of the sputtered sample material for both ion species i.e. noble gas ions and Ga FIB.

Jany, B. R.; Szajna, K.; Nikiel, M.; Wrana, D.; Trynkiewicz, E.; Pedrys, R.; Krok, F.

2015-02-01

92

Optical alteration of complex organics induced by ion irradiation  

Microsoft Academic Search

Most ion irradiation experiments relevant to primitive outer Solar System objects have been performed on ice and silicate targets. Here we present the first ion irradiation experiments performed on natural complex hydrocarbons (asphaltite and kerite). These materials are very dark in the visible and have red-sloped spectra in the visible and near-infrared. They may be comparable in composition and structure

Lyuba Moroz; Giuseppe Baratta; Giovanni Strazzulla; Larissa Starukhina; Elisabetta Dotto; Maria Antonietta Barucci; Gabriele Arnold; Elisa Distefano

2004-01-01

93

Carbon nanowires generated by ion irradiation of hydrocarbon ices  

NASA Astrophysics Data System (ADS)

In this paper we present the formation of carbon nanowires (polyynes and polycumulenes) in the solid state by ion irradiation of frozen hydrocarbons (C6H6 and C2H2). Irradiations have been performed using H+ ions in the 100's keV energy regime using fluences up to 5 × 1014 ions/cm2. Beyond the intrinsic significance of these results in the field of material science, this work has been motivated by the fact that ion beam irradiation of hydrocarbon ices is one of the most important process thought to happen in several extraterrestrial environments where many spectroscopic features of polyyne molecules have been identified.

Puglisi, O.; Compagnini, G.; D'Urso, L.; Baratta, G. A.; Palumbo, M. E.; Strazzulla, G.

2014-05-01

94

Influence of irradiation with swift heavy ions on multilayer Si/SiO{sub 2} heterostructures  

SciTech Connect

The influence of Xe ions with an energy of 167 MeV and a dose in the range 10{sup 12}-3 Multiplication-Sign 10{sup 13} cm{sup -2} on heterostructures consisting of six pairs of Si/SiO{sub 2} layers with the thicknesses {approx}8 and {approx}10 nm, correspondingly, is studied. As follows from electron microscopy data, the irradiation breaks down the integrity of the layers. At the same time, Raman studies give evidence for the enhancement of scattering in amorphous silicon. In addition, a yellow-orange band inherent to small-size Si clusters released from SiO{sub 2} appears in the photoluminescence spectra. Annealing at 800 Degree-Sign C recovers the SiO{sub 2} network, whereas annealing at 1100 Degree-Sign C brings about the appearance of a more intense photoluminescence peak at {approx}780 nm typical of Si nanocrystals. The 780-nm-peak intensity increases, as the irradiation dose is increased. It is thought that irradiation produces nuclei, which promote Si-nanocrystal formation upon subsequent annealing. The processes occur within the tracks due to strong heating because of ionization losses of the ions.

Kachurin, G. A., E-mail: kachurin@isp.nsc.ru; Cherkova, S. G.; Marin, D. V.; Volodin, V. A.; Cherkov, A. G.; Antonenko, A. Kh.; Kamaev, G. N. [Russian Academy of Sciences, Rzhanov Institute of Semiconductor Physics, Siberian Branch (Russian Federation); Skuratov, V. A. [Joint Institute for Nuclear Research (Russian Federation)

2013-03-15

95

Emulation of reactor irradiation damage using ion beams  

SciTech Connect

The continued operation of existing light water nuclear reactors and the development of advanced nuclear reactor depend heavily on understanding how damage by radiation to levels degrades materials that serve as the structural components in reactor cores. The first high dose ion irradiation experiments on a ferritic-martensitic steel showing that ion irradiation closely emulates the full radiation damage microstructure created in-reactor are described. Ferritic-martensitic alloy HT9 (heat 84425) in the form of a hexagonal fuel bundle duct (ACO-3) accumulated 155 dpa at an average temperature of 443°C in the Fast Flux Test Facility (FFTF). Using invariance theory as a guide, irradiation of the same heat was conducted using self-ions (Fe++) at 5 MeV at a temperature of 460°C and to a dose of 188 displacements per atom. The void swelling was nearly identical between the two irradiations and the size and density of precipitates and loops following ion irradiation are within a factor of two of those for neutron irradiation. The level of agreement across all of the principal microstructure changes between ion and reactor irradiations establishes the capability of tailoring ion irradiations to emulate the reactor-irradiated microstructure.

G. S. Was; Z. Jiao; E. Beckett; A. M. Monterrosa; O. Anderoglu; B. H. Sencer; M. Hackett

2014-10-01

96

Formation of TiO2 nanorods by ion irradiation  

NASA Astrophysics Data System (ADS)

Ion beam irradiation is a powerful method to fabricate and tailor the nanostructured surface of materials. Nanorods on the surface of single crystal rutile TiO2 were formed by N+ ion irradiation. The dependence of nanorod morphology on ion fluence and energy was elaborated. With increasing ion fluence, nanopores grow in one direction perpendicular to the surface and burst finally to form nanorods. The length of nanorods increases with increasing ion energy under same fluence. The development of the nanorod structure is originated from the formation of the nanopores while N2 bubbles and aggregation of vacancies were responsible for the formation of nanopores and nanorods. Combining C+ ion irradiation and post-irradiation annealing experiments, two qualitative models are proposed to explain the formation mechanism of these nanorods.

Zheng, X. D.; Ren, F.; Cai, G. X.; Hong, M. Q.; Xiao, X. H.; Wu, W.; Liu, Y. C.; Li, W. Q.; Ying, J. J.; Jiang, C. Z.

2014-05-01

97

Generation of colour centres in yttria-stabilized zirconia by heavy ion irradiations in the GeV range  

NASA Astrophysics Data System (ADS)

We have studied the colour centre production in yttria-stabilized zirconia (ZrO2:Y3 + ) by heavy ion irradiation in the GeV range using on-line UV-visible optical absorption spectroscopy. Experiments were performed with 11.4 MeV amu - 1 127Xe, 197Au, 208Pb and 238U ion irradiations at 8 K or room temperature (RT). A broad and asymmetrical absorption band peaked at a wavelength about 500 nm is recorded regardless of the irradiation parameters, in agreement with previous RT irradiations with heavy ions in the 100 MeV range. This band is de-convoluted into two broad Gaussian-shaped bands centred at photon energies about 2.4 and 3.1 eV that are respectively associated with the F + -type centres (involving a singly ionized oxygen vacancy, VO·) and T centres (i.e. Zr3 + in a trigonal symmetry) observed by electron paramagnetic resonance (EPR) spectroscopy. In the case of 8 K Au ion irradiation at low fluences, six bands are used at about 1.9, 2.3, 2.7, 3.1 and 4.0 eV. The three bands near 2.0-2.5 eV can be assigned to oxygen divacancies (i.e. F2 + centres). No significant effect of the irradiation temperature is found on the widths of all absorption bands for the same ion and fluence. This is attributed to the inhomogeneous broadening arising from the static disorder due to the native charge-compensating oxygen vacancies. However, the colour centre production yield is strongly enhanced at 8 K with respect to RT. When heating irradiated samples from 8 K to RT, the extra colour centres produced at low temperature do not recover completely to the level of RT irradiation. The latter results are accounted for by an electronically driven defect recovery process.

Costantini, Jean-Marc; Beuneu, François; Schwartz, Kurt; Trautmann, Christina

2010-08-01

98

Kinetic energy distribution of multiply charged ions in Coulomb explosion of Xe clusters  

NASA Astrophysics Data System (ADS)

We report on the calculations of kinetic energy distribution (KED) functions of multiply charged, high-energy ions in Coulomb explosion (CE) of an assembly of elemental Xen clusters (average size = 200-2171) driven by ultra-intense, near-infrared, Gaussian laser fields (peak intensities 1015 - 4 × 1016 W cm-2, pulse lengths 65-230 fs). In this cluster size and pulse parameter domain, outer ionization is incomplete/vertical, incomplete/nonvertical, or complete/nonvertical, with CE occurring in the presence of nanoplasma electrons. The KEDs were obtained from double averaging of single-trajectory molecular dynamics simulation ion kinetic energies. The KEDs were doubly averaged over a log-normal cluster size distribution and over the laser intensity distribution of a spatial Gaussian beam, which constitutes either a two-dimensional (2D) or a three-dimensional (3D) profile, with the 3D profile (when the cluster beam radius is larger than the Rayleigh length) usually being experimentally realized. The general features of the doubly averaged KEDs manifest the smearing out of the structure corresponding to the distribution of ion charges, a marked increase of the KEDs at very low energies due to the contribution from the persistent nanoplasma, a distortion of the KEDs and of the average energies toward lower energy values, and the appearance of long low-intensity high-energy tails caused by the admixture of contributions from large clusters by size averaging. The doubly averaged simulation results account reasonably well (within 30%) for the experimental data for the cluster-size dependence of the CE energetics and for its dependence on the laser pulse parameters, as well as for the anisotropy in the angular distribution of the energies of the Xeq+ ions. Possible applications of this computational study include a control of the ion kinetic energies by the choice of the laser intensity profile (2D/3D) in the laser-cluster interaction volume.

Heidenreich, Andreas; Jortner, Joshua

2011-02-01

99

Damaged carbon nanotubes get healed by ion irradiation  

SciTech Connect

Carbon nanotubes (CNTs) are being used for varied applications. It is therefore important to study their stability under extreme conditions of temperature and irradiation. In this work, we report the stability of CNTs [both single-wall CNTs (SWCNTs) and multiwalled CNTs (MWCNTs)] under irradiation of a carbon ion beam of energy 55 MeV. The irradiated samples were analyzed using Raman spectroscopy. The Raman results indicate the interesting phenomenon of healing or annealing of CNTs under ion beam irradiation. The annealing process appears to begin at the lowest value of fluences and persists for quite a good range of fluence values. As the irradiation dose increases ({approx_equal}1x10{sup 14} ions/cm{sup 2}) the MWCNTs begin to amorphize whereas the SWCNTs system continues to heal.

Jeet, Kiran; Jindal, V. K.; Dharamvir, Keya [Department of Physics, Panjab University, Chandigarh 160014 (India); Bharadwaj, L. M. [Biomolecular Electronic and Nanotechnology Division, Central Scientific Instruments Organisation, Sector 30-C, Chandigarh 160030 (India); Avasthi, D. K. [Materials Science Group, Inter University Accelerator Centre, Aruna Asaf Ali Marg, P.O. Box 10502, New Delhi 110067 (India)

2010-08-15

100

Enhanced electrochemical etching of ion irradiated silicon by localized amorphization  

SciTech Connect

A tailored distribution of ion induced defects in p-type silicon allows subsequent electrochemical anodization to be modified in various ways. Here we describe how a low level of lattice amorphization induced by ion irradiation influences anodization. First, it superposes a chemical etching effect, which is observable at high fluences as a reduced height of a micromachined component. Second, at lower fluences, it greatly enhances electrochemical anodization by allowing a hole diffusion current to flow to the exposed surface. We present an anodization model, which explains all observed effects produced by light ions such as helium and heavy ions such as cesium over a wide range of fluences and irradiation geometries.

Dang, Z. Y.; Breese, M. B. H. [Centre for Ion Beam Applications (CIBA), Department of Physics, National University of Singapore Singapore 117542 (Singapore); Lin, Y.; Tok, E. S. [Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542 (Singapore); Vittone, E. [Physics Department, NIS Excellence Centre and CNISM, University of Torino, via Pietro Giuria 1, 10125 Torino (Italy)

2014-05-12

101

Accumulation process of cascades in ceramics under ion and/or electron irradiation*1  

NASA Astrophysics Data System (ADS)

Dual-beam irradiation and simultaneous observation with 30 keV Xe + ions and 250 or 1000 keV electrons have been performed for understanding the structure and the accumulation process of cascades and for attaining insight into the synergistic effect of electron and/or free point defects on the properties of cascades. Covalent crystals such as Si, Ge and Ge?20 at% Si show contrast in transmission electron microscopy through the overlap of cascades, which stabilizes high concentration of point defects and induces an amorphous-like phase in covalent crystals. In ionic crystals such as MgO, Al 2O 3 and MgAl 2O 4, recombination of Frenkel pairs is of predominance and a small number of point defects are rather homogeneously distributed even when heavy ion impacts are introduced. The effects of electrons are to suppress the formation of vacancy clusters and to assist the nucleation of interstitial loops under the dual-beam irradiation.

Abe, Hiroaki; Kinoshita, Chiken; Nakai, Kiyomichi

1991-03-01

102

Radiation damage in ion-irradiated MgO  

Microsoft Academic Search

The microstructures found in specimens of single crystal MgO after irradiation with 2 MeV oxygen or 4 MeV iron ions were examined by transmission electron microscopy of cross-sectional specimens. The observed damage consisted primarily of dislocations. The end of the damage occurred at a depth of 2.4 mum for the oxygen irradiation and 2.8 mum for the iron irradiation. For

L. L. Horton; J. Bentley; M. B. Lewis

1986-01-01

103

The effects of swift heavy-ion irradiation on helium-ion-implanted silicon  

NASA Astrophysics Data System (ADS)

Cross-sectional transmission electron microscopy (XTEM) was used to study the effects of irradiation with swift heavy ions on helium-implanted silicon. <1 0 0>-oriented silicon wafers were implanted with 30 keV helium to a dose of 3 × 1016 He+/cm2 at 600 K. Subsequently, the helium-implanted Si wafers were irradiated with 792 MeV argon ions. The He bubbles and extended defects in the wafers were examined via XTEM analysis. The results reveal that the mean diameter of the He bubbles increases upon Ar-ion irradiation, while the number density of the He bubbles decreases. The microstructure of the He bubbles observed after Ar-ion irradiation is comparable to that observed after annealing at 1073 K for 30 min. Similarly, the mean size of the extended defects, i.e., Frank loops, increases after Ar-ion irradiation. Possible mechanisms are discussed.

Li, B. S.; Du, Y. Y.; Wang, Z. G.; Shen, T. L.; Li, Y. F.; Yao, C. F.; Sun, J. R.; Cui, M. H.; Wei, K. F.; Zhang, H. P.; Shen, Y. B.; Zhu, Y. B.; Pang, L. L.

2014-10-01

104

Ion irradiation tolerance of graphene as studied by atomistic simulations  

SciTech Connect

As impermeable to gas molecules and at the same time transparent to high-energy ions, graphene has been suggested as a window material for separating a high-vacuum ion beam system from targets kept at ambient conditions. However, accumulation of irradiation-induced damage in the graphene membrane may give rise to its mechanical failure. Using atomistic simulations, we demonstrate that irradiated graphene even with a high vacancy concentration does not show signs of such instability, indicating a considerable robustness of graphene windows. We further show that upper and lower estimates for the irradiation damage in graphene can be set using a simple model.

Ahlgren, E. H.; Lehtinen, O. [Department of Physics, University of Helsinki, P.O. Box 43, 00014 Helsinki (Finland); Kotakoski, J. [Department of Physics, University of Helsinki, P.O. Box 43, 00014 Helsinki (Finland); Department of Physics, University of Vienna, Boltzmanngasse 5, 1190 Wien (Austria); Krasheninnikov, A. V. [Department of Physics, University of Helsinki, P.O. Box 43, 00014 Helsinki (Finland); Department of Applied Physics, Aalto University, P.O. Box 1100, 00076 Aalto (Finland)

2012-06-04

105

Study on effects of energetic ion irradiation in Gd2O3-doped CeO2 by means of synchrotron radiation X-ray spectroscopy  

NASA Astrophysics Data System (ADS)

To study the effects of Gd2O3-doping and the irradiation with high energy fission products in the nuclear fuels (UO2), Gd2O3-doped CeO2 pellets, which are simulation materials of UO2, were irradiated with 200 MeV Xe14+ ions. Effects of Gd2O3-doping and the ion irradiation were estimated by using Extended X-ray Absorption Fine Structure (EXAFS) measurement. The interatomic distances between each Ce and the first nearest O atoms, and Ce and the second nearest Ce atoms increase by the irradiation and the effect of the ion irradiation on the atomic distances is more pronounced for higher amounts of dopant. The Debye-Waller factors for Ce-O and Ce-Ce pairs increase with increasing the amount of Gd2O3 dopant. These results suggest that the lattice binding energy is weakened by Gd2O3-doping. The Debye-Waller factors increase also by the irradiation. The effect of ion irradiation on the Debye-Waller factors, however, becomes smaller for higher amounts of dopant.

Tahara, Y.; Shimizu, K.; Ishikawa, N.; Okamoto, Y.; Hori, F.; Matsui, T.; Iwase, A.

2012-04-01

106

Ion exchange in glass using femtosecond laser irradiation  

SciTech Connect

We explain the occurrence of ion exchange and an index profile around the focal point inside a commercial crown glass formed by femtosecond laser irradiation. The index profile in the photoinduced area has a ring-shaped pattern, which indicates that local densification occurred in the glass. An irregular surface reflecting the density distribution is formed around the focal point by dry etching process using a focused ion beam. By the irradiation of femtosecond laser pulses, the effect of ion exchange between the focal point and the surrounding area is also observed in the area in which local densification occurred.

Kanehira, Shingo [Innovative Collaboration Center, Kyoto University, Nishikyo-ku, Kyoto 615-8510 (Japan); Miura, Kiyotaka; Hirao, Kazuyuki [Department of Material Chemistry, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510 (Japan)

2008-07-14

107

University of Wisconsin Ion Beam Laboratory: A facility for irradiated materials and ion beam analysis  

NASA Astrophysics Data System (ADS)

The University of Wisconsin Ion Beam Laboratory (UW-IBL) has recently undergone significant infrastructure upgrades to facilitate graduate level research in irradiated materials phenomena and ion beam analysis. A National Electrostatics Corp. (NEC) Torodial Volume Ion Source (TORVIS), the keystone upgrade for the facility, can produce currents of hydrogen ions and helium ions up to ˜200 ?A and ˜5 ?A, respectively. Recent upgrades also include RBS analysis packages, end station developments for irradiation of relevant material systems, and the development of an in-house touch screen based graphical user interface for ion beam monitoring. Key research facilitated by these upgrades includes irradiation of nuclear fuels, studies of interfacial phenomena under irradiation, and clustering dynamics of irradiated oxide dispersion strengthened steels. The UW-IBL has also partnered with the Advanced Test Reactor National Scientific User Facility (ATR-NSUF) to provide access to the irradiation facilities housed at the UW-IBL as well as access to post irradiation facilities housed at the UW Characterization Laboratory for Irradiated Materials (CLIM) and other ATR-NSUF partner facilities. Partnering allows for rapid turnaround from proposed research to finalized results through the ATR-NSUF rapid turnaround proposal system. An overview of the UW-IBL including CLIM and relevant research is summarized.

Field, K. G.; Wetteland, C. J.; Cao, G.; Maier, B. R.; Dickerson, C.; Gerczak, T. J.; Field, C. R.; Kriewaldt, K.; Sridharan, K.; Allen, T. R.

2013-04-01

108

Characteristic x rays from multiple-electron capture by slow highly charged Ta{sup q+} ions from He and Xe atoms  

SciTech Connect

Characteristic x rays, emitted by slow (velocity {nu}{approx}0.3 a.u.) highly charged Ta{sup q+} (q=41-49) ions after multiple capture from He or Xe atoms, were investigated in coincidence with recoil ions. The x-ray spectra are distinctly different for single and double capture as well as for different target ionization potentials (He and Xe). For the open M-shell configurations of the projectile (q>45) the spectra are dominated by cascade transitions. There is no evidence for direct radiative transitions from Rydberg states into the M shell, indicating dominant capture into angular momentum states that forbids such transitions. From such features we get, by comparison with spectra obtained from the calculation of the radiative cascades, the angular momentum values of the captured electron. A simple model, including autoionization, is used to relate double- and single-capture x-ray spectra and to explain their differences. The x-ray spectra with projectiles having no initial M vacancies (q<45) can have an important contribution from the internal dielectronic excitation (IDE) process. It is found that this channel is drastically reduced for double capture from He and closed for projectiles with q=41, as expected from our calculations of the core-excited states in Ta{sup (q-1)+}. The x-ray spectra and photon yields in these heavy systems are thus determined by a competition between the relaxation channels: radiative relaxation, IDE, and, for multiple capture, autoionization.

Madzunkov, S. [Department of Atomic Physics, Stockholm University, Alba Nova S-10691 Stockholm (Sweden); Department of Physics, Kansas State University, Manhattan, Kansas 66506 (United States); Fry, D. [Department of Physics, Kansas State University, Manhattan, Kansas 66506 (United States); Lindroth, E.; Schuch, R. [Department of Atomic Physics, Stockholm University, Alba Nova S-10691 Stockholm (Sweden)

2006-03-15

109

Swift heavy ion irradiation of muscovite and biotite substrates  

NASA Astrophysics Data System (ADS)

We report magnetic and spectroscopic studies of naturally occurring layered phyllosilicates; muscovite and biotite of Sikkim Himalaya. The minerals are characterised by SEM-EDS, powder X-ray diffraction (pXRD), electron paramagnetic resonance (EPR) and magnetometry. EPR spectra of muscovite and its axial dependence show the presence of Mn2+ ions in the silicate sheets. The samples are irradiated with 120 MeV Au ions and the consequent structural modifications are analysed. The irradiation does not influence the compositions, structural and magnetic properties of these micas. Therefore, both muscovite and biotite are more suitable for use as substrates than many other materials routinely used as substrates for swift heavy ion irradiation measurements.

Tiwari, Archana; Tripathi, Ajay; Pathak, Anand P.

2015-01-01

110

Ion irradiation of TNO surface analogue ice mixtures: the chemistry .  

NASA Astrophysics Data System (ADS)

Vis-NIR spectra of some Centaurs and Trans-Neptunian Objects (TNOs) indicate surfaces rich in H_2O, N_2, CO_2, CH_4 e CH_3OH. Cosmic ion irradiation is one of the processes driving the evolution of TNO surfaces. A main role is played by the chemistry induced by colliding ions; many molecular bonds are broken along the ion track, and this may lead to the formation of byproduct molecules. Starting from laboratory experiments, it is possible to infer the presence of molecules still undetected on TNOs. For instance, carbonic acid (H_2CO_3) is produced after irradiation of H_2O:CO_2 icy mixtures, while irradiation of H_2O:N_2 icy mixtures causes the production of N_2O, NO, and NO_2. From H_2O:CH_4:N_2 mixtures, many species are formed, such as CO, CO_2, HCN, HNCO, N_2O, and molecules including CN bonds. Moreover, ion irradiation may modify the relative intensity of NIR features, as in the case of solid methanol, whose 2.34 mu m band decreases in intensity with respect to the 2.27 mu m band, after increasing irradiation doses. We suggest that this effect may be observed on Centaur Pholus.

Baratta, G. A.; Brunetto, R.; Caniglia, G.; Fulvio, D.; Ioppolo, S.; Leto, G.; Palumbo, M. E.; Spinella, F.; Strazzulla, G.

111

Response of Strontium Titanate to Ion and Electron Irradiation  

SciTech Connect

Response of strontium titanate (SrTiO3) to ion and electron irradiation is studied at room temperature. For an accurate energy to depth conversion and a better determination of ion-induced disorder profile from Rutherford backscattering spectrometry measurement, a detailed iterative procedure is described and applied to ion channeling spectra to determine the dechanneling yield and the disorder profiles for the Sr and Ti sublattices. The result shows a large underestimation in disorder depth, ~ 40% at the damage peak, which indicates a large overestimation of the electronic stopping power for 1.0 MeV Au ions in SrTiO3 predicted by the SRIM (Stopping and Range of Ions in Matter) code. Overestimation of heavy ion stopping power may lead to an overestimation of the critical dose for amorphization. The current study also demonstrates possible ionization effects in SrTiO3 under ion and electron irradiation. Pre-amorphized SrTiO3 exhibits strong ionization-induced epitaxial recovery at the amorphous/crystalline interface under electron irradiation.

Zhang, Yanwen; Lian, Jie; Zhu, Zihua; Bennett, Wendy D.; Saraf, Laxmikant V.; Rausch, Julie L.; Hendricks, Catherine A.; Ewing, R. C.; Weber, William J.

2009-04-20

112

Effect of swift heavy ion irradiations in polycrystalline aluminum nitride  

NASA Astrophysics Data System (ADS)

Thanks to its high thermal conductivity, aluminum nitride may be a serious candidate as fuel coating for the Gas Fast Reactor. However, its behavior under irradiation is not entirely well understood. In order to catch a glimpse of this behavior, specimens were irradiated with swift heavy ions of different energies then characterized by both thermally stimulated luminescence and optical absorption spectrophotometry. With these techniques, the native defects, as well as those affected by irradiation, were identified: thus, by comparison to the virgin sample, no new defect detectable by these techniques is created by irradiations. Eventually, the fact that these techniques complement each other allowed to understand the effect of irradiation parameters on the defect concentration.

Nappé, J. C.; Benabdesselam, M.; Grosseau, Ph.; Guilhot, B.

2011-01-01

113

Ion irradiation of ammonia/carbon dioxide mixtures  

NASA Astrophysics Data System (ADS)

We present new experimental results on the thermal and ion irradiation processing of ammonia/carbon dioxide frozen mixtures. Mixtures deposited at low T (16 K) have then been warmed up to 160 K. During warm up complex chemical reactions occur leading to the formation of new molecules and, in particular, of ammonium carbamate. Other samples have been irradiated with 144 keV S9+ ions. Also in this case new chemical species are formed among which CO and OCN-. The results are discussed in the light of their relevance to understand the effects of different processes going on in the variegated superficial and sub-superficial layers of Enceladus.

Lv, X. Y.; Boduch, P.; Ding, J. J.; Domaracka, A.; Langlinay, T.; Palumbo, M. E.; Rothard, H.; Strazzulla, G.

2013-09-01

114

Crystalline nanostructures on Ge surfaces induced by ion irradiation  

NASA Astrophysics Data System (ADS)

Besides conventional low efficiency lithographic techniques broad ion beam irradiation is a simple and potentially mass productive technique to fabricate nanoscale patterns on various semiconductor surfaces. The main drawback of this method is that the irradiated semiconductor surfaces are amorphized, which strongly limits the potential application of these nanostructures in electronic and optoelectronic devices. In this work we report that high-quality crystalline nanostructure patterns are formed on Ge surfaces via Ar+ irradiation at elevated temperatures. This pattern formation process resembles the pattern formation in homoepitaxy. Therefore, the process is discussed based on a 'reverse epitaxy' mechanism.

Ou, Xin; Facsko, Stefan

2014-12-01

115

On the uptake of water vapor by ion irradiated polyimide  

NASA Astrophysics Data System (ADS)

It is known that ion-irradiated polymers are capable to adsorb dopants from solid, liquid or gaseous phases. For simple ambient atmosphere exposures, oxygen and water vapor are the most prominent dopants. Though the quantity of the latter one is not sufficient to be probed by conventional spectroscopic techniques, it can be detected indirectly via its ionic conductivity on applying a strong electric field along the track direction, as long as it is not yet masked by the intrinsic ion track conductivity, which is the case for low-fluence polymer irradiation. The conductivity is of similar order for most low-fluence irradiated polymers examined - namely 10-15-10-13 ?-1 cm-1. Water vapor uptake - as determined via the ion track conductivity - sensitively depends on the ambient air humidity, so that fresh low fluence irradiated polymers can act as humidity sensors. Aging however leads to rapid deterioration of this property within a week exposure time at ambient room temperature and pressure. The water vapor absorption process in tracks is reversible, and the amount of water retained depends specifically on the polymer. Thus, whereas for polyimide, polycarbonate, polypropylene, and polytetrafluoride some water vapor adsorption is detected, polymethylmethacrylate and polyethyleneterepthalate exhibit little or no effect. Moreover, uptake of water vapor is restricted to the latent ion tracks themselves, and is barely detectable in neighboring pristine material. It scales linearly with the deposition of electronic energy along the ion track.

Fink, D.; Klett, R.; Müller, M.; Hu, Xuanwen; Chadderton, L. T.; Wang, L.; Hillenbrand, J.

116

High energy XeBr electric discharge laser  

DOEpatents

A high energy XeBr laser for producing coherent radiation at 282 nm. The XeBr laser utilizes an electric discharge as the excitation source to minimize formation of molecular ions thereby minimizing absorption of laser radiation by the active medium. Additionally, HBr is used as the halogen donor which undergoes harpooning reactions with Xe.sub.M * to form XeBr*.

Sze, Robert C. (Santa Fe, NM); Scott, Peter B. (Los Alamos, NM)

1981-01-01

117

Magnetization and susceptibility of ion irradiated granular magnetite films  

SciTech Connect

Superparamagnetic granular magnetite (Fe3O4) films with an average grain size of 3 nm have been found to be magnetized following 5.5 MeV Si2+ ion irradiation to a fluence of 1.0E16 ions/cm2 near room temperature. The film underwent a phase transition to ferromagnetism after the irradiation. X-ray diffraction study shows that the average grain size increased to 23 nm. There is a dramatic change in the microstructure, featuring particle aggregation and material condensation. Magnetic domains in the irradiated film are observed in the size range of tens to several hundreds of nanometers. The change in the magnetic properties is attributed to irradiation induced grain growth and structural modifications that lead to occurrence of magnetic anisotropy. There are dipolar interactions between the nanoparticles in both the unirradiated and irradiated films. Data fits for the in-phase alternating current magnetic susceptibility of the unirradiated film indicate that the blocking temperature is ~150 K, depending on frequency. A gradual Verwey transition for the irradiated film occurs at ~75 K, above which the susceptibility exhibits unusual behavior: a linear decrease with decreasing temperature. There are irreversible processes of magnetic domains during cooling and warming up between 10 and 300 K.

Jiang, Weilin; McCloy, John S.; Lea, Alan S.; Sundararajan, J. A.; Yao, Qi; Qiang, Y.

2011-04-26

118

Cumulative dosage from heavy ion irradiation  

NASA Astrophysics Data System (ADS)

The near-earth radiation environment encountered by orbiting spacecraft is characterized, along with techniques for predicting effects long-term exposure to heavy ions have on electronic components and materials. The ions are resident in solar flares, galactic and extragalactic cosmic rays, and the Van Allen radiation belts. Ionized species, displaced and excited atoms, heating and broken chemical bonds are produced to a degree that depends on the cross-sectional absorption by the matter in the spacecraft. The matter-energy interactions are explored in depth, with emphasis on degradation of Si substrates and techniques for predicting the useful lifetime of components in the near-earth environment.

Bourrieau, Jacques

119

Magnetic properties of ion irradiated epitaxial Fe films  

NASA Astrophysics Data System (ADS)

Magnetic properties of a heavy-ion irradiated single crystalline iron film were investigated. A high quality Fe (001) film with a thickness of 250 nm was fabricated on MgO (001) using the molecular beam epitaxy technique. The film was irradiated by 3.2 MeV Ni ions at room temperature using a tandem accelerator. Formation of dislocation loops with nanometer size was observed by TEM observation, and that of sub-nanometer size vacancy clusters was confirmed indirectly from a resistivity increase. However, M-H hysteresis curves and magnetic domain structure did not change significantly. These results indicate the formation of irradiation defects of pure iron in nanometer scale range has little influence on the magnetization process of the iron.

Kamada, Y.; Watanabe, H.; Mitani, S.; Echigoya, J.; Mohapatra, J. N.; Kikuchi, H.; Kobayashi, S.; Takanashi, K.

2011-01-01

120

Ion irradiation damage on tin side surface of float glass  

NASA Astrophysics Data System (ADS)

Changes in the surface morphology and in-depth density variation in two surfaces of a float glass viz. the tin side and non-tin side surface, are investigated after 100 keV Ar ion irradiation. In the tin side surface, the irradiation caused a drastic change in density and surface roughness, whereas the other side (non-tin side surface) remained almost unaffected. Roughness of the tin side increases from 8 Å to 41 Å. Surface density also modified significantly with a redistribution of surface impurities. Monte Carlo simulations suggest that the displacement of tin and Fe impurities are responsible for the surface damage, which are experimentally examined by employing the total reflection X-ray fluorescence technique. Morphological and density changes are analyzed by grazing incidence X-ray reflectivity and atomic force microscopy techniques. Subsequent changes in surface morphology of float glass by ion irradiation are explained.

Modi, Mohammed H.; Lodha, Gyanendra S.; Tiwari, Manoj K.; Rai, Sanjay K.; Mukharjee, C.; Magudapathy, P.; Nair, K. G. M.; Nandedkar, Rajendra V.

2005-10-01

121

Effects of Ga ion-beam irradiation on monolayer graphene  

NASA Astrophysics Data System (ADS)

The effects of Ga ion on the single layer graphene (SLG) have been studied by Raman spectroscopy (RS), SEM, and field-effect characterization. Under vacuum conditions, Ga ion-irradiation can induce disorders and cause red shift of 2D band of RS, rather than lattice damage in high quality SLG. The compressive strain induced by Ga ion decreases the crystalline size in SLG, which is responsible for the variation of Raman scattering and electrical properties. Nonlinear out-put characteristic and resistance increased are also found in the I-V measurement. The results have important implications during CVD graphene characterization and related device fabrication.

Wang, Quan; Mao, Wei; Ge, Daohan; Zhang, Yanmin; Shao, Ying; Ren, Naifei

2013-08-01

122

Effects of Ga ion-beam irradiation on monolayer graphene  

SciTech Connect

The effects of Ga ion on the single layer graphene (SLG) have been studied by Raman spectroscopy (RS), SEM, and field-effect characterization. Under vacuum conditions, Ga ion-irradiation can induce disorders and cause red shift of 2D band of RS, rather than lattice damage in high quality SLG. The compressive strain induced by Ga ion decreases the crystalline size in SLG, which is responsible for the variation of Raman scattering and electrical properties. Nonlinear out-put characteristic and resistance increased are also found in the I-V measurement. The results have important implications during CVD graphene characterization and related device fabrication.

Wang, Quan; Mao, Wei; Zhang, Yanmin; Shao, Ying; Ren, Naifei [School of Mechanical Engineering, Jiangsu University, Zhenjiang 212013 (China)] [School of Mechanical Engineering, Jiangsu University, Zhenjiang 212013 (China); Ge, Daohan [School of Mechanical Engineering, Jiangsu University, Zhenjiang 212013 (China) [School of Mechanical Engineering, Jiangsu University, Zhenjiang 212013 (China); State Key Laboratory of Transducer Technology, Chinese Academy of Sciences, Shanghai 200050 (China)

2013-08-12

123

Evaporation of ion-irradiated disks  

E-print Network

We calculate the evaporation of a cool accretion disk around a black hole due to the ion-bombardment by an ion supported accretion flow (here ISAF, or optically thin ADAF). As first suggested by Spruit & Deufel (2002), this evaporation takes place in two stages: ion bombardment of the cool disk (Shakura-Sunyaev disk: SSD) produces an intermediate-temperature layer on top of the disk (`warm layer') which constitutes an independent accretion flow on both sides of the SSD. As this warm material accretes inward of the inner radius of the SSD, it becomes thermally unstable by lack of cooling of photons, and evaporates into the ISAF, thereby feeding the latter. Angular momentum conservation forces a certain fraction of the ISAF material to move outward, where it can bombard the SSD with its hot ions. The flow geometry is derived by computing stationary solutions of the continuity- and angular momentum equations for the three components (ISAF, warm flow and SSD). The overall radiative output is dominated by hard X-rays. They are produced mostly from the warm component, rather than the ISAF. The expected time dependence and stability of the flow, not computed here, is discussed briefly.

C. P. Dullemond; H. C. Spruit

2005-01-21

124

Ion Irradiation Effects in Synthetic Garnets Incorporating Actinides Satoshi Utsunomiya1  

E-print Network

Ion Irradiation Effects in Synthetic Garnets Incorporating Actinides Satoshi Utsunomiya1 , Lu the long term radiation effects due to radioactive decay can be simulated in short term with heavy ion-irradiation[3], many irradiation experiments using heavy ions have been completed in the potential ceramics

Utsunomiya, Satoshi

125

Vibrational spectra and structures of bare and Xe-tagged cationic SinOm+ clusters  

NASA Astrophysics Data System (ADS)

Vibrational spectra of Xe-tagged cationic silicon oxide clusters SinOm+ with n = 3-5 and m = n, n ± 1 in the gas phase are obtained by resonant infrared multiple photon dissociation (IRMPD) spectroscopy and density functional theory calculations. The SinOm+ clusters are produced in a laser vaporization ion source and Xe complexes are formed after thermalization to 100 K. The clusters are subsequently irradiated with tunable light from an IR free electron laser and changes in the mass distribution yield size-specific IR spectra. The measured IRMPD spectra are compared to calculated linear IR absorption spectra leading to structural assignments. For several clusters, Xe complexation alters the energetic order of the SinOm+ isomers. Common structural motifs include the Si2O2 rhombus, the Si3O2 pentagon, and the Si3O3 hexagon.

Savoca, Marco; Langer, Judith; Harding, Dan J.; Palagin, Dennis; Reuter, Karsten; Dopfer, Otto; Fielicke, André

2014-09-01

126

In-situ high temperature irradiation setup for temperature dependent structural studies of materials under swift heavy ion irradiation  

NASA Astrophysics Data System (ADS)

An in-situ high temperature (1000 K) setup is designed and installed in the materials science beam line of superconducting linear accelerator at the Inter-University Accelerator Centre (IUAC) for temperature dependent ion irradiation studies on the materials exposed with swift heavy ion (SHI) irradiation. The Gd2Ti2O7 pyrochlore is irradiated using 120 MeV Au ion at 1000 K using the high temperature irradiation facility and characterized by ex-situ X-ray diffraction (XRD). Another set of Gd2Ti2O7 samples are irradiated with the same ion beam parameter at 300 K and simultaneously characterized using in-situ XRD available in same beam line. The XRD studies along with the Raman spectroscopic investigations reveal that the structural modification induced by the ion irradiation is strongly dependent on the temperature of the sample. The Gd2Ti2O7 is readily amorphized at an ion fluence 6 × 1012 ions/cm2 on irradiation at 300 K, whereas it is transformed to a radiation-resistant anion-deficient fluorite structure on high temperature irradiation, that amorphized at ion fluence higher than 1 × 1013 ions/cm2. The temperature dependent ion irradiation studies showed that the ion fluence required to cause amorphization at 1000 K irradiation is significantly higher than that required at room temperature irradiation. In addition to testing the efficiency of the in-situ high temperature irradiation facility, the present study establishes that the radiation stability of the pyrochlore is enhanced at higher temperatures.

Kulriya, P. K.; Kumari, Renu; Kumar, Rajesh; Grover, V.; Shukla, R.; Tyagi, A. K.; Avasthi, D. K.

2015-01-01

127

Translational energy dependence of reaction mechanism: Xe++CH4?XeH++CH3  

E-print Network

The dynamics of the exoergic ion–molecule reaction Xe+(CH4,CH3)XeH+ were studied by chemical accelerator techniques over the relative translational energy range 0.2 to 8 eV. Results of the kinematicmeasurements are reported as scattering intensity...

Miller, G. D.; Strattan, L. W.; Cole, C. L.; Hierl, Peter M.

1981-01-01

128

Comparison of Deuterium Retention for Ion-irradiated and Neutron-irradiated Tungsten  

SciTech Connect

The behavior of D retention for Fe{sup 2+}-irradiated tungsten with a damage of 0.025-3 dpa was compared with that for neutron-irradiated tungsten with 0.025 dpa. The D{sub 2} thermal desorption spectroscopy (TDS) spectra for Fe{sup 2+}-irradiated tungsten consisted of two desorption stages at 450 and 550 K, while that for neutron-irradiated tungsten was composed of three stages and an addition desorption stage was found at 750 K. The desorption rate of the major desorption stage at 550K increased as the displacement damage increased due to Fe{sup 2+} irradiation increasing. In addition, the first desorption stage at 450K was found only for damaged samples. Therefore, the second stage would be based on intrinsic defects or vacancy produced by Fe{sup 2+} irradiation, and the first stage should be the accumulation of D in mono-vacancy and the activation energy would be relatively reduced, where the dislocation loop and vacancy is produced. The third one was found only for neutron irradiation, showing the D trapping by a void or vacancy cluster, and the diffusion effect is also contributed to by the high full-width at half-maximum of the TDS spectrum. Therefore, it can be said that the D{sub 2} TDS spectra for Fe{sup 2+}-irradiated tungsten cannot represent that for the neutron-irradiated one, indicating that the deuterium trapping and desorption mechanism for neutron-irradiated tungsten is different from that for the ion-irradiated one.

Yasuhisa Oya; Masashi Shimada; Makoto Kobayashi; Takuji Oda; Masanori Hara; Hideo Watanabe; Yuji Hatano; Pattrick Calderoni; Kenji Okuno

2011-12-01

129

Effect of irradiation spectrum on the microstructure of ion-irradiated Al{sub 2}O{sub 3}  

SciTech Connect

Polycrystalline samples of alpha-alumina have been irradiated with various ions ranging from 3.6 MeV Fe{sup +} to 1 MeV H{sup +} ions at 650 C. Cross-section transmission electron microscopy was used to investigate the depth-dependent microstructure of the irradiated specimens. The microstructure following irradiation was observed to be dependent on the irradiation spectrum. In particular, defect cluster nucleation was effectively suppressed in specimens irradiated with light ions such as 1 MeV H{sup +} ions. On the other hand, light ion irradiation tended to accelerate the growth rate of dislocation loops. The microstructural observations are discussed in terms of ionization enhanced diffusion processes.

Zinkle, S.J. [Oak Ridge National Lab., TN (United States). Metals and Ceramics Div.

1994-12-31

130

Kr ion irradiation study of the depleted-uranium alloys.  

SciTech Connect

Fuel development for the reduced enrichment research and test reactor (RERTR) program is tasked with the development of new low enrichment uranium nuclear fuels that can be employed to replace existing high enrichment uranium fuels currently used in some research reactors throughout the world. For dispersion type fuels, radiation stability of the fuel-cladding interaction product has a strong impact on fuel performance. Three depleted-uranium alloys are cast for the radiation stability studies of the fuel-cladding interaction product using Kr ion irradiation to investigate radiation damage from fission products. SEM analysis indicates the presence of the phases of interest: U(Al, Si){sub 3}, (U, Mo)(Al, Si){sub 3}, UMo{sub 2}Al{sub 20}, U{sub 6}Mo{sub 4}Al{sub 43} and UAl{sub 4}. Irradiations of TEM disc samples were conducted with 500 keV Kr ions at 200 C to ion doses up to 2.5 x 10{sup 19} ions/m{sup 2} ({approx}10 dpa) with an Kr ion flux of 10{sup 16} ions/m{sup 2}/s ({approx}4.0 x 10{sup -3} dpa/s). Microstructural evolution of the phases relevant to fuel-cladding interaction products was investigated using transmission electron microscopy.

Gan, J.; Keiser, D. D.; Miller, B. D.; Kirk, M. A.; Rest, J.; Allen, T. R.; Wachs, D. M. (Materials Science Division); (INL); (Univ. of Wisconsin)

2010-12-01

131

Kr Ion Irradiation Study of the Depleted-Uranium Alloys  

SciTech Connect

Fuel development for the Reduced Enrichment Research and Test Reactor program is tasked with the development of new low-enriched uranium nuclear fuels that can be employed to replace existing highly enriched uranium fuels currently used in some research reactors throughout the world. For dispersion-type fuels, radiation stability of the fuel/cladding interaction product has a strong impact on fuel performance. Three depleted uranium alloys are cast for the radiation stability studies of the fuel/cladding interaction product using Kr ion irradiation to investigate radiation damage from fission products. SEM analysis indicates the presence of the phases of interest: U(Si, Al)3, (U, Mo)(Si, Al)3, UMo2Al20, U6Mo4Al43, and UAl4. Irradiations of TEM disc samples were conducted with 500 keV Kr ions at 200ºC to ion doses up to 2.5 × 1015 ions/cm2 (~ 10 dpa) with an Kr ion flux of 1012 ions/cm2-sec (~ 4.0 × 10-3 dpa/sec). Microstructural evolution of the phases relevant to fuel-cladding interaction products was investigated using transmission electron microscopy.

J. Gan; D. Keiser; B. Miller; M. Kirk; J. Rest; T. Allen; D. Wachs

2010-12-01

132

Kr ion irradiation study of the depleted-uranium alloys  

NASA Astrophysics Data System (ADS)

Fuel development for the reduced enrichment research and test reactor (RERTR) program is tasked with the development of new low enrichment uranium nuclear fuels that can be employed to replace existing high enrichment uranium fuels currently used in some research reactors throughout the world. For dispersion type fuels, radiation stability of the fuel-cladding interaction product has a strong impact on fuel performance. Three depleted-uranium alloys are cast for the radiation stability studies of the fuel-cladding interaction product using Kr ion irradiation to investigate radiation damage from fission products. SEM analysis indicates the presence of the phases of interest: U(Al, Si) 3, (U, Mo)(Al, Si) 3, UMo 2Al 20, U 6Mo 4Al 43 and UAl 4. Irradiations of TEM disc samples were conducted with 500 keV Kr ions at 200 °C to ion doses up to 2.5 × 10 19 ions/m 2 (˜10 dpa) with an Kr ion flux of 10 16 ions/m 2/s (˜4.0 × 10 -3 dpa/s). Microstructural evolution of the phases relevant to fuel-cladding interaction products was investigated using transmission electron microscopy.

Gan, J.; Keiser, D. D.; Miller, B. D.; Kirk, M. A.; Rest, J.; Allen, T. R.; Wachs, D. M.

2010-12-01

133

Late degeneration in rabbit tissues after irradiation by heavy ions  

NASA Technical Reports Server (NTRS)

Results are presented for investigations of the late effects of heavy-ion irradiation on rabbit tissues which were undertaken to assess the hazards associated with the long-term exposure of humans to heavy ions in space during such activities as the construction of solar power stations or voyages to Mars. White rabbits approximately six weeks old were exposed to various doses of collimated beams of 400-MeV/n Ne ions, 570 MeV/n Ar ions and Co-60 gamma rays directed through both eyes, and the responses of the various tissues (hair follicles, skin, cornea, lens, retina, Harderian glands, bone and forebrain) were examined. Proliferating tissues are found to exhibit high damage levels in the early and late periods following irradiation, while terminally differentiating tissues repond to radiation most intensely in the late period, years after irradiation, with no intermediate recovery. The results obtained from rabbits are used to predict the occurrence of late tissue degeneration in the central nervous system, terminally differentiating systems and stem cells of humans one or more decades following exposure to radiation levels anticipated during long-duration space flights. The studies also indicate that tissues may be prematurely aged in the sense that tissue life spans may be shortened without the development of malignancies.

Lett, J. T.; Cox, A. B.; Keng, P. C.; Lee, A. C.; Su, C. M.; Bergtold, D. S.

1980-01-01

134

Ion-irradiation-induced amorphization of cobalt nanoparticles  

SciTech Connect

The amorphization of Co nanoparticles embedded in SiO{sub 2} has been investigated by measuring their structure and size, before and after ion irradiation, by x-ray absorption spectroscopy and small-angle x-ray scattering, respectively. Compared to bulk material, unirradiated crystalline nanoparticles exhibited increased structural disorder and a decreased average coordination number as a result of finite-size effects. Upon irradiation, there was no variation in nanoparticle size yet significant structural change. The coordination number decreased further while the mean value (bondlength), variance (Debye-Waller factor), and asymmetry (third cumulant) of the interatomic distance distribution all increased, as consistent with theoretical predictions for an amorphous elemental metal. Furthermore, the interatomic distance distribution for irradiated Co nanoparticles was in excellent agreement with our molecular dynamics simulations for bulk amorphous Co, and we have thus attributed the observed structural changes to the formation of an amorphous phase. Though such a crystalline-to-amorphous phase transformation is not readily achievable in bulk material by ion irradiation, we suggest that the perturbed structural state prior to irradiation and the amorphous surrounding matrix both contribute to nucleating and stabilizing the amorphous phase in irradiated Co nanoparticles. In addition to the structural properties, the vibrational properties of the amorphous phase were also probed, using temperature-dependent x-ray absorption spectroscopy measurements. The Einstein temperature of the unirradiated crystalline nanoparticles was lower than that of bulk material due to loosely bonded surface/interfacial atoms. In contrast, that of the irradiated amorphous nanoparticles was substantially higher than the bulk value. We attribute this apparent bond stiffening to the influence of the rigid surrounding matrix.

Sprouster, D. J.; Giulian, R.; Araujo, L. L.; Kluth, P.; Johannessen, B.; Kirby, N.; Nordlund, K.; Ridgway, M. C. [Department of Electronic Materials Engineering, Research School of Physics and Engineering, Australian National University, Canberra, Australian Capital Territory 0200 (Australia); Australian Synchrotron, Clayton, Victoria 3168 (Australia); Department of Physics and Helsinki Institute of Physics, University of Helsinki, Helsinki (Finland); Department of Electronic Materials Engineering, Research School of Physics and Engineering, Australian National University, Canberra, Australian Capital Territory 0200 (Australia)

2010-04-15

135

Magnetic properties of graphite irradiated with MeV ions  

SciTech Connect

We have studied the change in the magnetic properties produced on highly oriented pyrolytic graphite samples by irradiation of H, C, and N ions in the mega-electron-volt energy range. The use of specially made sample holders for the magnetic measurements provided high reproducibility allowing us to obtain directly the irradiation effects without any corrections or subtractions. Our results show that three magnetic phenomena are triggered by the defects produced by the irradiation, namely, Curie-type paramagnetism, ferromagnetism and an anomalous paramagnetic state that appears as precursor of the magnetic ordered state. Using SRIM simulations to estimate the amount of vacancies produced by the irradiation, the Curie-type paramagnetic response indicates an effective Bohr magneton number per nominally produced vacancy p=0.27+-0.02mu{sub B}. Direct measurements of the surface sample temperature during irradiation and the decrease in the (as-received) paramagnetic as well as ferromagnetic contributions after irradiation indicate that self-heating is one of the causes for small yield of ferromagnetism. Taking into account the hydrogen distribution in the virgin samples, the obtained results indicate that the induced ferromagnetism appears when the average vacancy distance is {approx}2 nm in the near surface region.

Ramos, M. A.; Munoz-Martin, A.; Climent-Font, A. [CMAM and Instituto de Ciencia de Materiales 'Nicolas Cabrera', Universidad Autonoma de Madrid, Cantoblanco, E-28049 Madrid (Spain); Barzola-Quiquia, J.; Esquinazi, P. [Division of Superconductivity and Magnetism, Institut fuer Experimentelle Physik II, Universitaet Leipzig, Linnestrasse 5, D-04103 Leipzig (Germany); Garcia-Hernandez, M. [Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco, E-28049 Madrid (Spain)

2010-06-01

136

Magnetization and susceptibility of ion-irradiated granular magnetite films  

NASA Astrophysics Data System (ADS)

Porous granular films of magnetite (Fe3O4) with grains of ˜3 nm in size were prepared using a state-of-the-art nanocluster deposition system. The films are initially superparamagnetic but become magnetized following Si2+ ion irradiation. A significant increase in the grain size and a dramatic change in the microstructure are observed. There are dipolar interactions between the nanoparticles in both the unirradiated and irradiated films. The in-phase alternating current magnetic susceptibility of the unirradiated film shows a blocking temperature of ˜150 K, depending on frequency. A broadened Verwey transition for the irradiated film occurs at ˜75 K, above which the susceptibility exhibits unusual behavior: a nearly linear decrease with decreasing temperature. There are irreversible domain rotations in the irradiated film during zero-field cooling and warming cycles between 10 and 300 K. The observed behavior of the irradiated granular films is quite distinct from that of metallic nanostructures after irradiation, and is due to the dramatic change in microstructures.

Jiang, W.; McCloy, J. S.; Lea, A. S.; Sundararajan, J. A.; Yao, Q.; Qiang, Y.

2011-04-01

137

Magnetization and susceptibility of ion-irradiated granular magnetite films  

SciTech Connect

Porous granular films of magnetite (Fe{sub 3}O{sub 4}) with grains of {approx}3 nm in size were prepared using a state-of-the-art nanocluster deposition system. The films are initially superparamagnetic but become magnetized following Si{sup 2+} ion irradiation. A significant increase in the grain size and a dramatic change in the microstructure are observed. There are dipolar interactions between the nanoparticles in both the unirradiated and irradiated films. The in-phase alternating current magnetic susceptibility of the unirradiated film shows a blocking temperature of {approx}150 K, depending on frequency. A broadened Verwey transition for the irradiated film occurs at {approx}75 K, above which the susceptibility exhibits unusual behavior: a nearly linear decrease with decreasing temperature. There are irreversible domain rotations in the irradiated film during zero-field cooling and warming cycles between 10 and 300 K. The observed behavior of the irradiated granular films is quite distinct from that of metallic nanostructures after irradiation, and is due to the dramatic change in microstructures.

Jiang, W.; McCloy, J. S.; Lea, A. S.; Sundararajan, J. A.; Yao, Q.; Qiang, Y. [Pacific Northwest National Laboratory, Richland, Washington 99352 (United States); Physics Department, University of Idaho, Moscow, Idaho 83844 (United States)

2011-04-01

138

Metastable hydronium ions in UV-irradiated ice  

SciTech Connect

We show that the irradiation of UV light (10-11 eV) onto an ice film produces metastable hydronium (H{sub 3}O{sup +}) ions in the ice at low temperatures (53-140 K). Evidence of the presence of metastable hydronium ions was obtained by experiments involving adsorption of methylamine onto UV-irradiated ice films and hydrogen-deuterium (H/D) isotopic exchange reaction. The methylamine adsorption experiments showed that photogenerated H{sub 3}O{sup +} species transferred a proton to the methylamine arriving at the ice surface, thus producing the methyl ammonium ion, which was detected by low energy sputtering method. The H{sub 3}O{sup +} species induced the H/D exchange of water, which was monitored through the detection of water isotopomers on the surface by using the Cs{sup +} reactive ion scattering method. Thermal and temporal stabilities of H{sub 3}O{sup +} and its proton migration activity were examined. The lifetime of the hydronium ions in the amorphized ice was greater than 1 h at {approx}53 K and decreased to {approx}5 min at 140 K. Interestingly, a small portion of hydronium ions survived for an extraordinarily long time in the ice, even at 140 K. The average migration distance of protons released from H{sub 3}O{sup +} in the ice was estimated to be about two water molecules at {approx}54 K and about six molecules at 100 K. These results indicate that UV-generated hydronium ions can be efficiently stabilized in low-temperature ice. Such metastable hydronium ions may play a significant role in the acid-base chemistry of ice particles in interstellar clouds.

Moon, Eui-Seong; Kang, Heon [Department of Chemistry, Seoul National University, 1 Gwanak-ro, Seoul 151-747 (Korea, Republic of)

2012-11-28

139

Mutagenic effects of heavy ion irradiation on rice seeds  

NASA Astrophysics Data System (ADS)

Three varieties of rice seeds were subjected to irradiation using low-energy and medium-energy ions. The damage and mutations induced by the ions were examined. In addition, genetic analysis and gene mapping of spotted leaf (spl) mutants were performed. Low-energy ions had no significant influence on germination, survival or seedling height, except for the survival of Nipponbare. Medium-energy ions had a significant influence on germination and survival but had no significant effect on seedling height. In the low-energy group, among 60,000 M2 plants, 2823 putative morphological mutants were found, and the mutation frequency was approximately 4.71%. In the medium-energy group, 3132 putative morphological mutants were found, and the mutation frequency was approximately 5.22%. Five spl mutants (spl29-spl33) were obtained by ion irradiation, and the heredity of the spl mutants was stable. The characteristics of the spl mutants were found, by genetic analysis and preliminary mapping, to be controlled by a single recessive gene, and spl30 and spl33 were found to be new lesion-mimic mutants.

Xu, Xue; Liu, Binmei; Zhang, Lili; Wu, Yuejin

2012-11-01

140

Tunable nanometer electrode gaps by MeV ion irradiation  

PubMed Central

We report the use of MeV ion-irradiation-induced plastic deformation of amorphous materials to fabricate electrodes with nanometer-sized gaps. Plastic deformation of the amorphous metal Pd80Si20 is induced by 4.64 MeV O2+ ion irradiation, allowing the complete closing of a sub-micrometer gap. We measure the evolving gap size in situ by monitoring the field emission current-voltage (I-V) characteristics between electrodes. The I-V behavior is consistent with Fowler-Nordheim tunneling. We show that using feedback control on this signal permits gap size fabrication with atomic-scale precision. We expect this approach to nanogap fabrication will enable the practical realization of single molecule controlled devices and sensors. PMID:22550357

Cheang-Wong, J.-C.; Narumi, K.; Schürmann, G. M.; Aziz, M. J.; Golovchenko, J. A.

2012-01-01

141

Tunable nanometer electrode gaps by MeV ion irradiation.  

PubMed

We report the use of MeV ion-irradiation-induced plastic deformation of amorphous materials to fabricate electrodes with nanometer-sized gaps. Plastic deformation of the amorphous metal Pd(80)Si(20) is induced by 4.64 MeV O(2+) ion irradiation, allowing the complete closing of a sub-micrometer gap. We measure the evolving gap size in situ by monitoring the field emission current-voltage (I-V) characteristics between electrodes. The I-V behavior is consistent with Fowler-Nordheim tunneling. We show that using feedback control on this signal permits gap size fabrication with atomic-scale precision. We expect this approach to nanogap fabrication will enable the practical realization of single molecule controlled devices and sensors. PMID:22550357

Cheang-Wong, J-C; Narumi, K; Schürmann, G M; Aziz, M J; Golovchenko, J A

2012-04-01

142

Tunable nanometer electrode gaps by MeV ion irradiation  

SciTech Connect

We report the use of MeV ion-irradiation-induced plastic deformation of amorphous materials to fabricate electrodes with nanometer-sized gaps. Plastic deformation of the amorphous metal Pd{sub 80}Si{sub 20} is induced by 4.64 MeV O{sup 2+} ion irradiation, allowing the complete closing of a sub-micrometer gap. We measure the evolving gap size in situ by monitoring the field emission current-voltage (I-V) characteristics between electrodes. The I-V behavior is consistent with Fowler-Nordheim tunneling. We show that using feedback control on this signal permits gap size fabrication with atomic-scale precision. We expect this approach to nanogap fabrication will enable the practical realization of single molecule controlled devices and sensors.

Cheang-Wong, J.-C.; Narumi, K.; Schuermann, G. M. [Department of Physics, Harvard University, Cambridge, Massachusetts 02138 (United States); Aziz, M. J. [School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138 (United States); Golovchenko, J. A. [Department of Physics, Harvard University, Cambridge, Massachusetts 02138 (United States); School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138 (United States)

2012-04-09

143

[Grain boundary and interface kinetics during ion irradiation  

SciTech Connect

Proposed here is renewed support of a research program focused on interface motion and phase transformation during ion irradiation, with emphasis on elemental semiconductors. Broadly speaking, the aims of this program are to explore defect kinetics in amorphous and crystalline semiconductors, and to relate defect dynamics to interface motion and phase transformations. Over the last three years, we initiated a program under DOE support to explore crystallization and amorphization of elemental semiconductors under irradiation. This research has enabled new insights about the nature of defects in amorphous semiconductors and about microstructural evolution in the early stages of crystallization. In addition, we have demonstrated almost arbitrary control over the relative rates of crystal nucleation and crystal growth in silicon. As a result, the impinged grain microstructure of thin (100 nm) polycrystalline films crystallized under irradiation can be controlled with grain sizes ranging from a few nanometers to several micrometers, which may have interesting technological implications.

Atwater, H.A.

1991-12-31

144

(Grain boundary and interface kinetics during ion irradiation)  

SciTech Connect

Proposed here is renewed support of a research program focused on interface motion and phase transformation during ion irradiation, with emphasis on elemental semiconductors. Broadly speaking, the aims of this program are to explore defect kinetics in amorphous and crystalline semiconductors, and to relate defect dynamics to interface motion and phase transformations. Over the last three years, we initiated a program under DOE support to explore crystallization and amorphization of elemental semiconductors under irradiation. This research has enabled new insights about the nature of defects in amorphous semiconductors and about microstructural evolution in the early stages of crystallization. In addition, we have demonstrated almost arbitrary control over the relative rates of crystal nucleation and crystal growth in silicon. As a result, the impinged grain microstructure of thin (100 nm) polycrystalline films crystallized under irradiation can be controlled with grain sizes ranging from a few nanometers to several micrometers, which may have interesting technological implications.

Atwater, H.A.

1991-01-01

145

Orientation Dependence of Flaking of Ion Irradiated Aluminum Single Crystals  

Microsoft Academic Search

Surface erosion on mono- and poly-crystalline aluminum, irradiated with 300-500 keV He+ or Ne+ ions at room temperature along the axial or off-axial directions, has been examined by SEM and TEM. The critical fluence at which flaking appears on the surface increased according to the order of the poly-crystalline sample, mono-crystals with surface normals of [111], [100] and [110]. On

Kotaro Ono; Takao Kino; Kohji Kamada; Hiroto Osono

1986-01-01

146

Respiratory gated irradiation system for heavy-ion radiotherapy  

Microsoft Academic Search

Purpose: In order to reduce the treatment margin of the moving target due to breathing, we developed a gated irradiation system for heavy-ion radiotherapy.Methods and Materials: The motion of a patient due to respiration is detected by the motion of the body surface around the chest wall. A respiratory sensor was developed using an infrared light spot and a position-sensitive

Shinichi Minohara; Tatsuaki Kanai; Masahiro Endo; Kouji Noda; Mitsutaka Kanazawa

2000-01-01

147

Sympathetic ophthalmia complicating helium ion irradiation of a choroidal melanoma  

Microsoft Academic Search

Sympathetic ophthalmia was diagnosed 49 months after helium ion irradiation of a left choroidal melanoma. The patient maintained good vision until 18 months after therapy, when she developed neovascular glaucoma. This complication required multiple therapeutic procedures, including topical anti-inflammatory and antiglaucomatous drops, 360 degrees peripheral panretinal cryoblation, and a single 180 degrees application of inferior cyclocryotherapy over a 2 1\\/2-year

P. D. Fries; D. H. Char; J. B. Crawford; W. Waterhouse

1987-01-01

148

Magnetization and susceptibility of ion-irradiated granular magnetite films  

Microsoft Academic Search

Porous granular films of magnetite (Fe3O4) with grains of ˜3 nm in size were prepared using a state-of-the-art nanocluster deposition system. The films are initially superparamagnetic but become magnetized following Si2+ ion irradiation. A significant increase in the grain size and a dramatic change in the microstructure are observed. There are dipolar interactions between the nanoparticles in both the unirradiated

Weilin Jiang; John S. McCloy; Alan S. Lea; J. A. Sundararajan; Qi Yao; Y. Qiang

2011-01-01

149

Track Structure in DNA Irradiated with Heavy Ions  

SciTech Connect

The spatial properties of trapped radicals produced in heavy ion-irradiated solid DNA at 77 K have been probed using pulsed Electron Paramagnetic Double Resonance (PELDOR or DEER) techniques. Salmon testes DNA hydrated to twelve water molecules per nucleotide was irradiated with 40Ar ions of energy 100 MeV/nucleon and LET ranging from 300 to 400 keV/?. Irradiated samples were maintained at cryogenic temperature at all times. PELDOR measurements were made using a refocused echo detection sequence that allows dipolar interaction between trapped radicals to be observed. The EPR spectrum is attributed to electron loss/gain DNA base radicals and neutral carbon-centered radicals that likely arise from sugar damage. We find a radical concentration of 13.5*1018 cm-3 in the tracks and a track radius of 6.79 nm. The cross section of these tracks is 144 nm2 yielding a lineal radical density of 2.6 radicals/nm. Based upon the yields previously determined for particles having calculated LET values of 300-400 keV/mm and our measured lineal density, we obtain an LET of 270 keV/mm, which is in good agreement with the calculated range of values. These measurements of radical density and spatial extent provide the first direct experimental determination of track characteristics in irradiated DNA.

Bowman, Michael K.; Becker, David; Sevilla, Michael D.; Zimbrick, John D.

2005-04-01

150

Manipulation of the graphene surface potential by ion irradiation  

NASA Astrophysics Data System (ADS)

We show that the work function of exfoliated single layer graphene can be modified by irradiation with swift (Ekin=92 MeV) heavy ions under glancing angles of incidence. Upon ion impact individual surface tracks are created in graphene on silicon carbide. Due to the very localized energy deposition characteristic for ions in this energy range, the surface area which is structurally altered is limited to ?0.01 ?m2 per track. Kelvin probe force microscopy reveals that those surface tracks consist of electronically modified material and that a few tracks suffice to shift the surface potential of the whole single layer flake by ?400 meV. Thus, the irradiation turns the initially n-doped graphene into p-doped graphene with a hole density of 8.5×1012 holes/cm2. This doping effect persists even after heating the irradiated samples to 500 °C. Therefore, this charge transfer is not due to adsorbates but must instead be attributed to implanted atoms. The method presented here opens up a way to efficiently manipulate the charge carrier concentration of graphene.

Ochedowski, O.; Kleine Bussmann, B.; Ban d'Etat, B.; Lebius, H.; Schleberger, M.

2013-04-01

151

Light ion irradiation for unfavorable soft tissue sarcoma  

SciTech Connect

Between 1978 and 1989, 32 patients with unfavorable soft tissue sarcoma underwent light ion (helium, neon) irradiation with curative intent at Lawrence Berkeley Laboratory. The tumors were located in the trunk in 22 patients and head and neck in 10. Macroscopic tumor was present in 22 at the time of irradiation. Two patients had tumors apparently induced by previous therapeutic irradiation. Follow-up times for surviving patients ranged from 4 to 121 months (median 27 months). The overall 3-year actuarial local control rate was 62%; the corresponding survival rate was 50%. The 3-year actuarial control rate for patients irradiated with macroscopic tumors was 48%, while none of the patients with microscopic disease developed local recurrence (100%). The corresponding 3-year actuarial survival rates were 40% (macroscopic) and 78% (microscopic). Patients with retroperitoneal sarcoma did notably well; the local control rate and survival rate were 64% and 62%, respectively. Complications were acceptable; there were no radiation related deaths, while two patients (6%) required operations to correct significant radiation-related injuries. These results appear promising compared to those achieved by low -LET irradiation, and suggest that this technique merits further investigation.

Linstadt, D.; Castro, J.R.; Phillips, T.L.; Petti, P.L.; Collier, J.M.; Daftari, I.; Schoethaler, R.; Rayner, A.

1990-09-01

152

Time-dependent characteristics of the dielectric barrier discharge in Xe-Cl2 mixture and kinetics of the XeCl? molecules  

NASA Astrophysics Data System (ADS)

Time-dependent characteristics of the dielectric barrier discharge in Xe-Cl2 mixture at chlorine concentration of 0.5% and kinetic processes governing the generation of XeCl? molecules are studied using the 1D fluid model. It is shown that at low voltage amplitude (5 kV) a one-peak mode of the discharge is observed and at high voltage amplitude (7 kV) a two-peak mode of the discharge appears. The radiation power of the XeCl? band increases with amplitude of the supply voltage. It is demonstrated that the harpoon reaction Xe? + Cl2 ? XeCl? + Cl provides the greatest contribution into generation of XeCl? exciplex molecules during short current pulses and the ion-ion recombination Xe+ 2 + Cl- ? XeCl* + Xe provides the greatest contribution during afterglow. Quenching of XeCl? molecules is a result of the radiative decay XeCl? ? Xe + Cl + hv (308 nm). During current spike the great contribution into quenching of XeCl? provides also the dissociative ionization e + XeCl? ? Xe+ + Cl + 2e.

Avtaeva, Svetlana

2014-04-01

153

Characterization of polymeric films subjected to lithium ion beam irradiation  

NASA Astrophysics Data System (ADS)

Two different polymeric materials that are candidate materials for use as binders for mixed uranium-plutonium oxide nuclear fuel pellets were subjected to Li ion beam irradiation, in order to simulate intense alpha irradiation. The materials (a polyethylene glycol 8000 and a microcrystalline wax) were then analyzed using a combination of mass spectrometry (MS) approaches and X-ray photoelectron spectroscopy (XPS). Samples of the irradiated PEG materials were dissolved in H2O and then analyzed using electrospray ionization-MS, which showed the formation of a series of small oligomers in addition to intact large PEG oligomers. The small oligomers were likely formed by radiation-induced homolytic scissions of the C-O and C-C bonds, which furnish radical intermediates that react by radical recombination with Hrad and OHrad . Surface analysis using SIMS revealed a heterogeneous surface that contained not only PEG-derived polymers, but also hydrocarbon-based entities that are likely surface contaminants. XPS of the irradiated PEG samples indicated the emergence of different carbon species, with peak shifts suggesting the presence of sp2 carbon atoms. Analysis of the paraffinic film using XPS showed the emergence of oxygen on the surface of the sample, and also a broadening and shifting of the C1s peak, demonstrating a change in the chemistry on the surface. The paraffinic film did not dissolve in either H2O or a H2O-methanol solution, and hence the bulk of the material could not be analyzed using electrospray. However a series of oligomers was leached from the bulk material that produced ion series in the ESI-MS analyses that were identified octylphenyl ethoxylate oligomers. Upon Li ion bombardment, these shifted to a lower average molecular weight, but more importantly showed the emergence of three new ion series that are being formed as a result of radiation damage. Surface analysis of the paraffinic polymers using SIMS produced spectra that were wholly dominated by hydrocarbon ion series, and no difference was observed between unirradiated and irradiated samples. The studies demonstrate that for the PEG-based polymers, direct evidence for radiolytic scission can be observed using ESI-MS, and suggests that both radiolytic pathways and efficiencies as a function of dose should be measurable by calibrating instrument response to the small oligomeric degradation products.

Groenewold, Gary S.; Cannon, W. Roger; Lessing, Paul A.; Avci, Recep; Deliorman, Muhammedin; Wolfenden, Mark; Akers, Doug W.; Jewell, J. Keith; Zuck, Larry D.

2013-02-01

154

Characterization of polymeric films subjected to lithium ion beam irradiation  

SciTech Connect

Two different polymeric materials that are candidate materials for use as binders for mixed uranium–plutonium oxide nuclear fuel pellets were subjected to Li ion beam irradiation, in order to simulate intense alpha irradiation. The materials (a polyethylene glycol 8000 and a microcrystalline wax) were then analyzed using a combination of mass spectrometry (MS) approaches and X-ray photoelectron spectroscopy (XPS). Samples of the irradiated PEG materials were dissolved in H2O and then analyzed using electrospray ionization-MS, which showed the formation of a series of small oligomers in addition to intact large PEG oligomers. The small oligomers were likely formed by radiation-induced homolytic scissions of the C–O and C–C bonds, which furnish radical intermediates that react by radical recombination with Hradical dot and OHradical dot. Surface analysis using SIMS revealed a heterogeneous surface that contained not only PEG-derived polymers, but also hydrocarbon-based entities that are likely surface contaminants. XPS of the irradiated PEG samples indicated the emergence of different carbon species, with peak shifts suggesting the presence of sp2 carbon atoms. Analysis of the paraffinic film using XPS showed the emergence of oxygen on the surface of the sample, and also a broadening and shifting of the C1s peak, demonstrating a change in the chemistry on the surface. The paraffinic film did not dissolve in either H2O or a H2O–methanol solution, and hence the bulk of the material could not be analyzed using electrospray. However a series of oligomers was leached from the bulk material that produced ion series in the ESI-MS analyses that were identified octylphenyl ethoxylate oligomers. Upon Li ion bombardment, these shifted to a lower average molecular weight, but more importantly showed the emergence of three new ion series that are being formed as a result of radiation damage. Surface analysis of the paraffinic polymers using SIMS produced spectra that were wholly dominated by hydrocarbon ion series, and no difference was observed between unirradiated and irradiated samples. The studies demonstrate that for the PEG-based polymers, direct evidence for radiolytic scission can be observed using ESI-MS, and suggests that both radiolytic pathways and efficiencies as a function of dose should be measurable by calibrating instrument response to the small oligomeric degradation products.

Gary S. Groenewold; W. Roger Cannon; Paul A. Lessing; Recep Avci; Muhammedin Deliorman; Mark Wolfenden; Doug W. Akers; J. Keith Jewell

2013-02-01

155

Ion irradiation damage in ilmenite at 100 K  

USGS Publications Warehouse

A natural single crystal of ilmenite (FeTiO3) was irradiated at 100 K with 200 keV Ar2+. Rutherford backscattering spectroscopy and ion channeling with 2 MeV He+ ions were used to monitor damage accumulation in the surface region of the implanted crystal. At an irradiation fluence of 1 ?? 1015 Ar2+/cm2, considerable near-surface He+ ion dechanneling was observed, to the extent that ion yield from a portion of the aligned crystal spectrum reached the yield level of a random spectrum. This observation suggests that the near-surface region of the crystal was amorphized by the implantation. Cross-sectional transmission electron microscopy and electron diffraction on this sample confirmed the presence of a 150 nm thick amorphous layer. These results are compared to similar investigations on geikielite (MgTiO3) and spinel (MgAl2O4) to explore factors that may influence radiation damage response in oxides.

Mitchell, J.N.; Yu, N.; Devanathan, R.; Sickafus, K.E.; Nastasi, M.A.; Nord, G.L., Jr.

1997-01-01

156

Origins of ion irradiation-induced Ga nanoparticle motion on GaAs surfaces  

SciTech Connect

We have examined the origins of ion irradiation-induced nanoparticle (NP) motion. Focused-ion-beam irradiation of GaAs surfaces induces random walks of Ga NPs, which are biased in the direction opposite to that of ion beam scanning. Although the instantaneous NP velocities are constant, the NP drift velocities are dependent on the off-normal irradiation angle, likely due to a difference in surface non-stoichiometry induced by the irradiation angle dependence of the sputtering yield. It is hypothesized that the random walks are initiated by ion irradiation-induced thermal fluctuations, with biasing driven by anisotropic mass transport.

Kang, M.; Wu, J. H.; Chen, H. Y.; Thornton, K.; Goldman, R. S. [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States)] [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States); Sofferman, D. L. [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States) [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States); Department of Physics, Adelphi University, Garden City, New York 11530-0701 (United States); Beskin, I. [Department of Physics, University of Michigan, Ann Arbor, Michigan 48109-1040 (United States)] [Department of Physics, University of Michigan, Ann Arbor, Michigan 48109-1040 (United States)

2013-08-12

157

Submitted for publication Production of defects in supported carbon nanotubes under ion irradiation  

E-print Network

Submitted for publication Production of defects in supported carbon nanotubes under ion irradiation University of Helsinki, Finland (December 10, 2001) Ion irradiation of individual carbon nanotubes deposited near irradiation-induced defects. 81.07.De, 61.48+c, 61.80.Jh,73.22.-f I. INTRODUCTION Recent

Nordlund, Kai

158

Grain growth in ZrFe thin films during in situ ion irradiation in a TEM  

E-print Network

Grain growth in Zr­Fe thin films during in situ ion irradiation in a TEM D. Kaoumi a,*, A.T. Motta Laboratory, Argonne, IL 060493, USA Available online 2 November 2005 Abstract In situ ion-beam irradiation was used to study irradiation induced grain growth in co-sputter-deposited Zr/xFe (0% 6 x 6 4

Motta, Arthur T.

159

Nanoscale manipulation of Ge nanowires by ion irradiation  

SciTech Connect

Nanowires have generated considerable interest as nanoscale interconnects and as active components of both electronic and electromechanical devices. However, in many cases, manipulation and modification of nanowires are required to fully realize their potential. It is essential, for instance, to control the orientation and positioning of nanowires in some specific applications. This work demonstrates a simple method to reversibly control the shape and the orientation of Ge nanowires using ion beams. Crystalline nanowires were amorphized by 30 keV Ga{sup +} implantation. Subsequently, viscous flow and plastic deformation occurred causing the nanowires to bend toward the beam direction. The bending was reversed multiple times by ion implanting the opposite side of the nanowires, resulting in straightening and subsequent bending into that opposite direction. This effect demonstrates the detailed manipulation of nanoscale structures is possible through the use of ion irradiation.

Romano, Lucia [Department of Physics and Astronomy, University of Catania and MATIS CNR-INFM, 64 Via S. Sofia, I-95123 Catania (Italy); Rudawski, Nicholas G.; Holzworth, Monta R.; Jones, Kevin S. [Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611 (United States); Choi, S. G.; Picraux, S. T. [Center for Integrated Nanotechnologies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

2009-12-01

160

Swift heavy ion irradiation of Pt nanocrystals: I. shape transformation and dissolution  

SciTech Connect

We report on the effects of swift heavy ion irradiation of embedded Pt nanocrystals (NCs), which change from spheres to prolate spheroids to rods upon irradiation. Using a broad range of ion irradiation energies and NC mean sizes we demonstrate that the elongation and dissolution processes are energy and size dependent, attaining comparable levels of shape transformation and dissolution upon a given energy density deposited in the matrix. The NC shape transformation remains operative despite discontinuous ion tracks in the matrix and exhibits a constant threshold size for elongation. In contrast, for ion irradiations in which the ion tracks are continuous, the threshold size for elongation is clearly energy dependent.

Giulian, R.; Araujo, L.L.; Kluth, P.; Sprouster, D.J.; Schnohr, C.S.; Byrne, A.P.; Ridgway, M.C. (ANU)

2014-09-24

161

Heavy ion irradiation effects of brannerite-type ceramics  

NASA Astrophysics Data System (ADS)

Brannerite, UTi 2O 6, occurs in polyphase Ti-based, crystalline ceramics that are under development for plutonium immobilization. In order to investigate radiation effects caused by ?-decay events of Pu, a 1 MeV Kr + irradiation on UTi 2O 6, ThTi 2O 6, CeTi 2O 6 and a more complex material, composed of Ca-containing brannerite and pyrochlore, was performed over a temperature range of 25-1020 K. The ion irradiation-induced crystalline-to-amorphous transformation was observed in all brannerite samples. The critical amorphization temperatures of the different brannerite compositions are: 970 K, UTi 2O 6; 990 K, ThTi 2O 6; 1020 K, CeTi 2O 6. The systematic increase in radiation resistance from Ce-, Th- to U-brannerite is related to the difference of mean atomic mass of A-site cation in the structure. As compared with the pyrochlore structure-type, brannerite phases are more susceptible to ion irradiation-induced amorphization. The effects of structure and chemical compositions on radiation resistance of brannerite-type and pyrochlore-type ceramics are discussed.

Lian, J.; Wang, L. M.; Lumpkin, G. R.; Ewing, R. C.

2002-05-01

162

Microstructure of RERTR DU-Alloys Irradiated with Krypton Ions  

SciTech Connect

Fuel development for reduced enrichment research and test reactor (RERTR) program is tasked with the development of new low enrichment uranium fuels that can be employed to replace existing high enrichment uranium fuels currently used in many research and test reactors worldwide. Radiation stability of the interaction product formed at fuel-matrix interface has a strong impact on fuel performance. Three depleted uranium alloys are cast that consist of the following 5 phases of interest to be investigated: U(Si,Al)3, (U,Mo)(Si,Al)3, UMo2Al20, U6Mo4Al43 and UAl4. Irradiation of TEM disc samples with 500 keV Kr ions at 200?C to high doses up to ~100 dpa were conducted using an intermediate voltage electron microscope equipped with an ion accelerator. The irradiated microstructure of the 5 phases is characterized using transmission electron microscopy. The results will be presented and the implication of the observed irradiated microstructure on the fuel performance will be discussed.

J. Gan; D. Keiser; D. Wachs; B. Miller; T. Allen; M. Kirk; J. Rest

2009-11-01

163

Ion irradiation-induced amorphization and nano-crystal formation in garnets  

E-print Network

Ion irradiation-induced amorphization and nano-crystal formation in garnets S. Utsunomiya a , L ion irradiation of the G3 garnet at a temperature of 1023 K near the Tc, nano-crystals were produced, particularly yttrium aluminum garnet (YAG), Y3Al5O12, and YAG doped by other ions for use in laser systems

Utsunomiya, Satoshi

164

Net sputtering rate due to hot ions in a Ne-Xe discharge gas bombarding an MgO layer  

SciTech Connect

An analytical method is developed for determining net sputtering rate for an MgO layer under hot ions with low energy (<100 eV) in a neon-xenon discharge gas at near-atmospheric pressure. The primary sputtering rate is analyzed according to spatial and energy distributions of the hot ions with average energy, E{sup h}{sub i}, above a threshold energy of sputtering, E{sub th,i}, multiplied by a yield coefficient. The threshold energy of sputtering is determined from dissociation energy required to remove an atom from MgO surface multiplied by an energy-transfer coefficient. The re-deposition rate of the sputtered atoms is calculated by a diffusion simulation using a hybridized probabilistic and analytical method. These calculation methods are combined to analyze the net sputtering rate. Maximum net sputtering rate due to the hot neon ions increases above the partial pressure of 4% xenon as E{sup h}{sub Ne} becomes higher and decreases near the partial pressure of 20% xenon as ion flux of neon decreases. The dependence due to the hot neon ions on partial pressure and applied voltage agrees well with experimental results, but the dependence due to the hot xenon ions deviates considerably. This result shows that the net sputtering rate is dominated by the hot neon ions. Maximum E{sup h}{sub Ne} (E{sup h}{sub Ne,max} = 5.3 - 10.3 eV) is lower than E{sub th,Ne} (19.5 eV) for the MgO layer; therefore, weak sputtering due to the hot neon ions takes place. One hot neon ion sputters each magnesium and each oxygen atom on the surface and distorts around a vacancy. The ratio of the maximum net sputtering rate is approximately determined by number of the ions at E{sup h}{sub i,max} multiplied by an exponential factor of -E{sub th,i}/E{sup h}{sub i,max}.

Ho, S.; Tamakoshi, T.; Ikeda, M.; Mikami, Y.; Suzuki, K. [Advanced Research Laboratory, Hitachi, Ltd., Akanuma 2520, Hatoyama-machi, Saitama 350-0395 (Japan)

2011-04-15

165

Compaction of microporous amorphous solid water by ion irradiation  

NASA Astrophysics Data System (ADS)

We have studied the compaction of vapor-deposited amorphous solid water by energetic ions at 40K. The porosity was characterized by ultraviolet-visible spectroscopy, infrared spectroscopy, and methane adsorption/desorption. These three techniques provide different and complementary views of the structural changes in ice resulting from irradiation. We find that the decrease in internal surface area of the pores, signaled by infrared absorption by dangling bonds, precedes the decrease in the pore volume during irradiation. Our results imply that impacts from cosmic rays can cause compaction in the icy mantles of the interstellar grains, which can explain the absence of dangling bond features in the infrared spectrum of molecular clouds.

Raut, U.; Teolis, B. D.; Loeffler, M. J.; Vidal, R. A.; Famá, M.; Baragiola, R. A.

2007-06-01

166

Production and irradiation of ionic liquid cluster ions  

NASA Astrophysics Data System (ADS)

We have developed a field-emission-type of cluster ion source using ionic liquids such as 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF6). The current obtained was stable by placing a porous cap around the emitter. Time-of-flight (TOF) measurement showed that the peak mass number was approximately 5000 for positive and negative BMIM-PF6 ion beams. This indicated that BMIM-PF6 clusters with a size of a few tens of molecules were produced. With regard to the surface modification by BMIM-PF6 ion beams, positive and negative cluster ion beams were used to irradiate Si(1 0 0) and glass substrates. Scanning electron microscope (SEM) and atomic force microscope (AFM) observations showed that the surface roughness of substrates increased. Furthermore, X-ray photoelectron spectroscopy (XPS) measurement showed that the composition ratio of layers deposited by positive or negative cluster ion beams was similar to that of BMIM-PF6 solvent.

Takaoka, Gikan H.; Takeuchi, Mitsuaki; Ryuto, Hiromichi; Ueda, Ryo

2013-07-01

167

QUB Low Energy Ion-Ices Irradiation Experiment  

NASA Astrophysics Data System (ADS)

Ion processing plays an important role in the chemical and physical modification of ice surfaces in astrophysical environments. This experimental project supported by the LASSIE ITN, led by Dr Tom Field, will investigate irradiation of astrophysical ice analogues by singly and multiply charged ion analogues of cosmic rays. Singly or multiply charged ions of either gaseous or solid elements are produced by a compact permanent magnet Electron Cyclotron Resonance (ECR) ion source attached to a ''floating beamline'' accelerator. Charge (q) to mass analysed ion beams in the energy range from a few 100 eV to 5xq keV are directed into a dedicated experimental chamber containing a temperature controlled (6K - 300K) cryostatically cooled sample of an astrophysical ice analogue. Current diagnostics include a differentially pumped, high resolution, quadrupole mass spectrometer mounted in ''line of sight'' of the ion impact area of the ice sample In a preliminary collaborative experiment with the groups of Prof Nigel Mason (Open University, UK) and Prof Elisabetta Palumbo (INAF-Osservatorio Astrofisico di Catania. Italy) and using a cryostat and FTIR spectrometer provided by Prof Nigel Mason we studied the interaction of 4 keV C+ and C2+ ions with H2O ices at 30K AND 90K. The most significant species formed in these interactions was 13CO2, the yield of which, with singly charged ions, could be explained by the competition between a formation and a destruction mechanism. In the case of doubly charged ions, explanation of the CO2 yield required additional formation and destruction mechanisms which were considered to be a result of the additional potential energy possessed by the projectile ions. These results also showed the influence of sample temperature and morphology. It is clear that for both singly and doubly charged projectile ions, the yield of 13CO2 was greater at 30K than at 90K. This effect has been observed elsewhere and has been assigned to the greater porosity of the 30K ice which leads to increased surface area on which reactions may occur.

Muntean, A.; Field, T.; Hunniford, A.; McCullough, B.; Konanoff, J.; Millar, T.

2011-05-01

168

Vibrational spectra and structures of bare and Xe-tagged cationic Si(n)O(m)? clusters.  

PubMed

Vibrational spectra of Xe-tagged cationic silicon oxide clusters Si(n)O(m)(+) with n = 3-5 and m = n, n ± 1 in the gas phase are obtained by resonant infrared multiple photon dissociation (IRMPD) spectroscopy and density functional theory calculations. The Si(n)O(m)(+) clusters are produced in a laser vaporization ion source and Xe complexes are formed after thermalization to 100 K. The clusters are subsequently irradiated with tunable light from an IR free electron laser and changes in the mass distribution yield size-specific IR spectra. The measured IRMPD spectra are compared to calculated linear IR absorption spectra leading to structural assignments. For several clusters, Xe complexation alters the energetic order of the Si(n)O(m)(+) isomers. Common structural motifs include the Si2O2 rhombus, the Si3O2 pentagon, and the Si3O3 hexagon. PMID:25217922

Savoca, Marco; Langer, Judith; Harding, Dan J; Palagin, Dennis; Reuter, Karsten; Dopfer, Otto; Fielicke, André

2014-09-14

169

Ion-irradiation-induced hardening in Inconel 718  

NASA Astrophysics Data System (ADS)

Inconel 718 is a material under consideration for areas in the target region of the spallation neutron source (SNS), now under construction at Oak Ridge National Laboratory (ORNL) in the US. In these positions, displacement damage from protons and neutrons will affect the mechanical properties. In addition, significant amounts of helium and hydrogen will build up in the material due to transmutation reactions. Nanoindentation measurements of solution-annealed (SA) Inconel 718 specimens, implanted with Fe-, He-, and H-ions to simulate SNS target radiation conditions, have shown that hardening occurs due to ion-induced displacement damage as well as due to the build-up of helium bubbles in the irradiated layer. Precipitation-hardened (PH) Inconel 718 also exhibited hardening by helium build-up but showed softening as a function of displacement damage due to dissolution of the ? ' and ?? precipitates.

Hunn, J. D.; Lee, E. H.; Byun, T. S.; Mansur, L. K.

2001-07-01

170

Behavior of nuclear materials irradiated with a dual ion beam  

NASA Astrophysics Data System (ADS)

Synergistic effects of nuclear (Sn) and electronic (Se) energy losses are investigated by comparing the damage accumulated in selected oxide (c-ZrO2, MgO, Gd2Ti2O7) and carbide (SiC) single crystals irradiated with single and dual low and high energy ion beams. Channeling results show that the Sn/Se synergy induces a strong decrease of the damage in MgO and SiC (where amorphization is prevented) and almost no effects in c-ZrO2 and Gd2Ti2O7. Raman and TEM results confirm this statement. The healing of defects generated by nuclear collisions in MgO and SiC is due to the electronic excitation produced in the wake of swift ions. These results present a strong interest for technological applications in the nuclear industry where expected cooperative Sn/Se effects may preserve the integrity of nuclear materials.

Thomé, Lionel; Veli?a, Gihan; Debelle, Aurélien; Miro, Sandrine; Garrido, Frédérico; Trocellier, Patrick; Serruys, Yves

2014-05-01

171

The change of microstructure and thermal properties in ion irradiated carbon nanotube mats as a function of ion penetration depth  

SciTech Connect

A stack of three carbon nanotube (CNT) mats was irradiated with 3 MeV He ions. The change in structural and thermal properties of individual mats as a function of ion penetration depth was characterized using electron microscopy and laser flash techniques. Ion irradiation can enhance thermal conductivity of the mats by introducing inter-tube displacements, which improve phonon transport across adjacent nanotubes. The enhancement, however, is reduced at higher damage levels due to the increasing phonon-defect scattering within the tubes. This study demonstrates the feasibility of using ion irradiation to manipulate thermal transport in carbon nanotubes.

Aitkaliyeva, A. [Materials Science and Engineering Program, Texas A and M University, College Station, Texas 77843 (United States)] [Materials Science and Engineering Program, Texas A and M University, College Station, Texas 77843 (United States); Shao, L. [Materials Science and Engineering Program, Texas A and M University, College Station, Texas 77843 (United States) [Materials Science and Engineering Program, Texas A and M University, College Station, Texas 77843 (United States); Department of Nuclear Engineering, Texas A and M University, College Station, Texas 77843 (United States)

2013-02-11

172

Vacuum ultraviolet absorption and ion track effects in LiF crystals irradiated with swift ions  

NASA Astrophysics Data System (ADS)

LiF crystals were irradiated with various light and heavy ions (Ni, Zn, Au, Pb, Bi, and U) of MeV to GeV energy. The radiation damage was studied by optical spectroscopy from the vacuum ultraviolet to the visible spectral region and by small angle x-ray scattering, in combination with optical bleaching and thermal annealing. In addition to the well-known electron centers (F and F2 centers) and the hole centers responsible for the previously observed band at 114 nm, a new absorption band was observed at 121 nm. The new band appears prominently in crystals irradiated with the heaviest projectiles (Au, Pb, Bi, U), is small for Zn ions, insignificant for the lighter Ni ion and absent in case of gamma irradiation. Under optical bleaching, F- and 114-nm centers are destroyed whereas the 121-nm band is relatively stable. The decay of the 121-nm band on thermal annealing coincides with the reduction of the small-angle x-ray scattering signal. It is considered that the 121-nm band is directly linked to hole-center clusters complementary to the electron-center aggregates in the core region of ion tracks. Evidence is presented to associate an absorption band at 275 nm formed after thermal annealing with the formation of small quasi-colloidal aggregates.

Davidson, A. T.; Schwartz, K.; Comins, J. D.; Kozakiewicz, A. G.; Toulemonde, M.; Trautmann, C.

2002-12-01

173

Influence of secondary particles from heavy ion irradiation to in-beam OpenPET detectors  

Microsoft Academic Search

We are investigating the influences of heavy ion irradiation on the detectors for in-beam OpenPET by using the Heavy Ion Medical Accelerator in Chiba (HIMAC) at the National institute of Radiological Sciences (NIRS). \\

F. Nishikido; Y. Yazaki; H. Osada; N. Inadama; T. Inaniwa; S. Satoh; K. Shibuya; E. Yoshida; T. Yamaya; H. Murayama

2009-01-01

174

Characterisation of dual ion beam irradiated yttria-stabilised zirconia by specific analytical techniques  

NASA Astrophysics Data System (ADS)

The combined effect of dual ion beam irradiated yttria-stabilized zirconia was investigated through Rutherford backscattering spectrometry/channeling (RBS/C), high resolution X-ray diffraction (HRXRD), atomic force microscopy (AFM) and transmission electron microscopy (TEM). Compared with other experimental results of single ion beam irradiation, a multistep damage accumulation model can also explain the irradiation effects of dual ion beam. Irradiation damage created by Ar + He ions are simply additive and no synergy effect has been observed. The variation trends of step height and displacement damage are similar. The synergic effects of displacement damage between heavy recoil atoms and ?-particle in nuclear waste matrices will not cause more serious damage than the sum of two kinds of ions. The two experimental damage peaks are consistent with those calculated using stopping and range of ions in matter (SRIM). Phase stability and irradiation resistance is further confirmed by high resolution transmission electron microscopy (HRTEM).

Zhang, Yanwen; Wang, Xu; Liu, Shiyi; Tang, Meixiong; Zhao, Ziqiang

2015-01-01

175

Modifications of optical properties of PC/ABS by dual ions beam irradiation  

NASA Astrophysics Data System (ADS)

Polycarbonate (PC)/acrylonitrile butadien styrene (ABS) blends used in the inner parts of automobiles require a glossy and metallic colored optical property. Such a surface can be produced by ion beam irradiation, but the surface treated by a single ion species irradiation tends to be degraded upon a long term exposure under UV and visible lights, which includes the loss of glossiness and the delamination of the irradiated layer. Such degradations can be prevented or greatly reduced by a combined irradiation of heavy and light ions such as N and He ions. This may be attributable to a graded interface between the irradiation affected layer and the base materials by overlapping penetration depths of the heavy and light ions. This work is motivated by an effort to substitute the conventional Cr plating process with the ion beam process in the automobile industry.

Park, Jae-Won; Lee, Jae-Sang; Lee, Byung-hoon; Kim, Min-kyu; Moon, Byung-Sik; Lee, Chan-Young; Choi, Byung-Ho

2013-03-01

176

Simulations of Xe and U diffusion in UO2  

SciTech Connect

Diffusion of xenon (Xe) and uranium (U) in UO{sub 2} is controlled by vacancy mechanisms and under irradiation the formation of mobile vacancy clusters is important. Based on the vacancy and cluster diffusion mechanisms established from density functional theory (DFT) calculations, we derive continuum thermodynamic and diffusion models for Xe and U in UO{sub 2}. In order to capture the effects of irradiation, vacancies (Va) are explicitly coupled to the Xe and U dynamics. Segregation of defects to grain boundaries in UO{sub 2} is described by combining the bulk diffusion model with models of the interaction between Xe atoms and vacancies with grain boundaries, which were derived from atomistic calculations. The diffusion and segregation models were implemented in the MOOSE-Bison-Marmot (MBM) finite element (FEM) framework and the Xe/U redistribution was simulated for a few simple microstructures.

Andersson, Anders D. [Los Alamos National Laboratory; Vyas, Shyam [Los Alamos National Laboratory; Tonks, Michael R. [Idaho National Laboratory; Casillas, Luis [Los Alamos National Laboratory; Uberuaga, Blas P. [Los Alamos National Laboratory; Millett, Paul [Idaho National Laboratory

2012-09-10

177

Development of porous structures in GaSb by ion irradiation  

NASA Astrophysics Data System (ADS)

Ion irradiation of GaSb causes not only defect formation but also leads to the formation of a porous structure. To study the behaviour of this structural modification, GaSb was irradiated with 6 MeV Iodine ions and ion fluences from 5 × 10 12 to 6 × 10 15 ions/cm 2. The samples were investigated by step height measurements and scanning electron microscopy (SEM). Experiments were performed with two different procedures: (CI) Continuous Irradiation of samples followed by measurements of the step height in air and (SI) Stepwise Irradiation of samples with measurements of the step height in air between subsequent irradiations. Samples irradiated continuously, show a linear increase of the step height with increasing ion fluence up to 1.5 × 10 14 ions/cm 2 followed by a steeper, linear increase for higher ion fluences up to a step height of 32 ?m. This swelling is induced by a formation of voids, and the two different slopes can be explained by a transformation from isolated voids to a rod like structure. For samples irradiated accordingly to procedure (SI), the step height shows the same behaviour up to an ion fluence of 1.5 × 10 14 ions/cm 2 resulting in a step height of ?3 ?m but then decreases with further irradiation. The latter effect is caused by a compaction of the porous structure.

Jacobi, C. C.; Steinbach, T.; Wesch, W.

2012-02-01

178

Determination of ion track radii in amorphous matrices via formation of nano-clusters by ion-beam irradiation  

SciTech Connect

We report on a method for the determination of ion track radii, formed in amorphous materials by ion-beam irradiation. The method is based on the addition to an amorphous matrix of a small amount of foreign atoms, which easily diffuse and form clusters when the temperature is sufficiently increased. The irradiation causes clustering of these atoms, and the final separations of the formed clusters are dependent on the parameters of the ion-beam. Comparison of the separations between the clusters that are formed by ions with different properties in the same type of material enables the determination of ion-track radii.

Buljan, M.; Karlusic, M.; Bogdanovic-Radovic, I.; Jaksic, M.; Radic, N. [Rudjer Boskovic Institute, Bijenicka cesta 54, 10000 Zagreb (Croatia); Salamon, K. [Institute of Physics, 10000 Zagreb (Croatia); Bernstorff, S. [Sincrotrone Trieste, 34102 Basovizza (Italy)

2012-09-03

179

Diamond-like carbon sputtering by laser produced Xe plasma  

NASA Astrophysics Data System (ADS)

The sputtering of diamond-like carbon (DLC) was investigated using Xe ion bombardment from the laser plasma X-ray source (LPX). The LPX we developed uses a solid Xe target and emits UV-X-rays and Xe ions. Using the LPX as an ion source, we measured etching depths of DLC, Ru, and Au films using a quartz crystal microbalance (QCM) to determine their ion sputtering rates at incident angles of 0° and 70°. The calculated results by the SRIM code were able to predict the measured results, except for the case of the DLC film at 0° incident. Our measured result indicated that the DLC sputtering at 0° was ten times larger than previously reported data, in which an ion gun was used. We consider that the difference was a characteristic effect of the laser plasma, and can be explained as a synergistic effect of ion bombardment and UV radiation from the Xe plasma.

Amano, Sho; Inoue, Tomoaki

2013-11-01

180

Surface pattern formation during MeV energy ion beam irradiation  

SciTech Connect

Surface patterning during high energy heavy ion irradiation is a relatively recent observation. We report in this paper the results of a study on the formation of self organized ripple patterns on silica surface irradiated with MeV energy gold ions.

Srivastava, S. K.; Nair, K. G. M.; Kannan, R. Kamala; Kamruddin, M.; Panigrahi, B. K.; Tyagi, A. K. [Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India)

2012-06-05

181

Effect of aging on surface chemical bonds of PTFE irradiated by low energy Ti ion  

NASA Astrophysics Data System (ADS)

Polytetrafluoroethylene (PTFE) was irradiated by low energy titanium ion in a metal vapor vacuum arc (MEVVA) implanter. The samples were irradiated with 80 keV Ti ion with fluences from 5×10 15 to 5×10 17 Ti/cm 2, respectively. Transportation of Ion in Matters (TRIM) code was employed to simulate Ti ion irradiation. The as-irradiated samples were investigated by ESCA, SEM and wettability. As increasing ion fluence, various chemical bonds and irradiation-damaged surfaces were observed. The water droplet contact angel of PTFE samples increased gradually with ion fluence. All the as-irradiated PTFE samples were aged in air for 1 year. After aging the surface-restructuring behavior was observed on the surfaces of the samples irradiated with ion fluence equal to or less than 5×10 16 Ti/cm 2, which resulted in decrease of the droplet contact angle of these samples. The surface roughness change of the aged samples, which were measured by atomic force microscopy (AFM), was consistent with the droplet contact angle change. The experimental results revealed that Ti ion fluence closely affected the surface chemical bond, morphology and wettability, as well as the aging stability of the as-irradiated PTFE samples.

Zhang, Jizhong; Zhang, Xiaoji; Zhou, Hongyu

2003-01-01

182

Temperature and ion irradiation dependence of magnetic domains and microstructure in CoPt multilayers  

E-print Network

-optical Kerr effect MOKE techniques. The microstructure of all samples was evaluated by TEM using a Philips CMTemperature and ion irradiation dependence of magnetic domains and microstructure in Co with perpendicular anisotropy were studied as a function of growth temperature (TG) and ion irradiation

Krishnan, Kannan M.

183

Production of defects in hexagonal boron nitride monolayer under ion irradiation O. Lehtinen a,  

E-print Network

Production of defects in hexagonal boron nitride monolayer under ion irradiation O. Lehtinen a, , E: Hexagonal boron nitride monolayer Ion irradiation Defect a b s t r a c t Atomistic computer simulations based on analytical potentials are employed to investigate the response of a hexagonal boron nitride

Krasheninnikov, Arkady V.

184

Modifying the electronic structure of semiconducting single-walled carbon nanotubes ion irradiation  

E-print Network

irradiation Antti Tolvanen,1 Gilles Buchs,2,3 Pascal Ruffieux,2 Pierangelo Gröning,2 Oliver Gröning,2-functional theory simulations with Ar- ion-irradiation experiments and low-temperature scanning tunneling microscopy and spectroscopy STM/STS characterization of the irradiated samples, we study the changes in the electronic

Krasheninnikov, Arkady V.

185

MeV single-ion beam irradiation of mammalian cells using the Surrey vertical nanobeam, compared with broad proton beam and X-ray irradiations  

NASA Astrophysics Data System (ADS)

As a part of a systematic study on mechanisms involved in physical cancer therapies, this work investigated response of mammalian cells to ultra-low-dose ion beam irradiation. The ion beam irradiation was performed using the recently completed nanobeam facility at the Surrey Ion Beam Centre. A scanning focused vertical ion nano-beam was applied to irradiate Chinese hamster V79 cells. The V79 cells were irradiated in two different beam modes, namely, focused single ion beam and defocused scanning broad ion beam of 3.8-MeV protons. The single ion beam was capable of irradiating a single cell with a precisely controlled number of the ions to extremely low doses. After irradiation and cell incubation, the number of surviving colonies as a function of the number of the irradiating ions was measured for the cell survival fraction curve. A lower survival for the single ion beam irradiation than that of the broad beam case implied the hypersensitivity and bystander effect. The ion-beam-induced cell survival curves were compared with that from 300-kV X-ray irradiation. Theoretical studies indicated that the cell death in single ion irradiation mainly occurred in the cell cycle phases of cell division and intervals between the cell division and the DNA replication. The success in the experiment demonstrated the Surrey vertical nanobeam successfully completed.

Prakrajang, K.; Jeynes, J. C. G.; Merchant, M. J.; Kirkby, K.; Kirkby, N.; Thopan, P.; Yu, L. D.

2013-07-01

186

Hardness modification of aluminum-alloys by means of energetic ion irradiation and subsequent thermal aging  

NASA Astrophysics Data System (ADS)

So far, we have found that the hardness of Al-Cu-Mg alloy (JIS2017, Duralumin) increases by energetic heavy ion irradiation at room temperature. Observations by using the three-dimensional atom probe (3DAP) have revealed that nano-meter sized precipitates are homogeneously distributed in the irradiated specimens, which are produced through the irradiation enhanced diffusion of solute atoms. The small precipitates contribute to the increase in hardness. In this report, we show the results for the hardness modification of Al-Cu-Mg alloy by the combination of energetic ion irradiation and thermal aging treatment. The hardness of the specimens pre-irradiated and thermally aged at 423 K is much larger than that without the pre-irradiation. The present result indicates that the combination of energetic ion irradiation and subsequent thermal aging can be used as an effective tool for the hardness modification of Al-Cu-Mg alloy.

Mitsuda, T.; Kobayashi, I.; Kosugi, S.; Fujita, Nao.; Saitoh, Y.; Hori, F.; Semboshi, S.; Kaneno, Y.; Nishida, K.; Soneda, N.; Ishino, S.; Iwase, A.

2012-02-01

187

Competition between two-photon-resonant three-photon ionization and four-wave mixing in Xe  

SciTech Connect

Competitive inhibition of a resonance enhanced multiphoton ionization process by a resonant four-wave mixing has been observed in Xe atoms. When an intense IR (1064 nm) laser was applied to a sample of Xe which was also being irradiated by a UV laser tuned to the two-photon absorption line of Xe, the two-photon-resonant three-photon ionization signals decreased with increasing IR laser power. This phenomenon is dependent on the resonant states of Xe and the polarization of the two laser beams. Three 6s excited states [5/2]{sub 2}, [3/2]{sub 2}, and [1/2]{sub 0} were examined. At the [1/2]{sub 0} resonant state, the ion signals were not decreased but slightly increased with the increase of the IR laser power. No suppression of the ion signal was observed at the [5/2]{sub 2} resonant state, when the polarization directions of the lasers were perpendicular to each other. The result of the polarization dependence reflects the selection rules of four-wave mixing. A simple rate equation analysis including the contribution of two-photon ionization from the [1/2]{sub 0} state by the IR laser well represents the IR laser-power dependence of the ion signal.

Nagai, Hidekazu; Nakanaga, Taisuke [National Institute of Advanced Industrial Science and Technology (AIST) Research Institute of Instrumentation Frontier, Tsukuba Central 5, Tsukuba, Ibaraki 305-8565 (Japan)

2011-12-15

188

Competition between two-photon-resonant three-photon ionization and four-wave mixing in Xe  

NASA Astrophysics Data System (ADS)

Competitive inhibition of a resonance enhanced multiphoton ionization process by a resonant four-wave mixing has been observed in Xe atoms. When an intense IR (1064 nm) laser was applied to a sample of Xe which was also being irradiated by a UV laser tuned to the two-photon absorption line of Xe, the two-photon-resonant three-photon ionization signals decreased with increasing IR laser power. This phenomenon is dependent on the resonant states of Xe and the polarization of the two laser beams. Three 6s excited states [5/2]2, [3/2]2, and [1/2]0 were examined. At the [1/2]0 resonant state, the ion signals were not decreased but slightly increased with the increase of the IR laser power. No suppression of the ion signal was observed at the [5/2]2 resonant state, when the polarization directions of the lasers were perpendicular to each other. The result of the polarization dependence reflects the selection rules of four-wave mixing. A simple rate equation analysis including the contribution of two-photon ionization from the [1/2]0 state by the IR laser well represents the IR laser-power dependence of the ion signal.

Nagai, Hidekazu; Nakanaga, Taisuke

2011-12-01

189

Energetic Ion and Electron Irradiation of the Icy Galilean Satellites  

NASA Technical Reports Server (NTRS)

Galileo Orbiter measurements of energetic ions (20 keV to 100 MeV) and electrons (20-700 keV) in Jupiter's magnetosphere are used, in conjunction with the JPL electron model (less than 40 MeV), to compute irradiation effects in the surface layers of Europa, Ganymede, and Callisto. Significant elemental modifications are produced on unshielded surfaces to approximately centimeter depths in times of less than or equal to 10(exp 6) years, whereas micrometer depths on Europa are fully processed in approximately 10 years. Most observations of surface composition are limited to optical depths of approximately 1 mm, which are indirect contact with the space environment. Incident flux modeling includes Stormer deflection by the Ganymede dipole magnetic field, likely variable over that satellite's irradiation history. Delivered energy flux of approximately 8 x 10(exp 10) keV/square cm-s at Europa is comparable to total internal heat flux in the same units from tidal and radiogenic sources, while exceeding that for solar UV energies (greater than 6 eV) relevant to ice chemistry. Particle energy fluxes to Ganymede's equator and Callisto are similar at approximately 2-3 x 10(exp 8) keV/square cm-s with 5 x 10(exp 9) at Ganymede's polar cap, the latter being comparable to radiogenic energy input. Rates of change in optical reflectance and molecular composition on Europa, and on Ganymede's polar cap, are strongly driven by energy from irradiation, even in relatively young regions. Irradiation of nonice materials can produce SO2 and CO2, detected on Callisto and Europa, and simple to complex hydrocarbons. Iogenic neutral atoms and meteoroids deliver negligible energy approximately 10(exp 4-5) keV/square cm-s but impacts of the latter are important for burial or removal of irradiation products. Downward transport of radiation produced oxidants and hydrocarbons could deliver significant chemical energy into the satellite interiors for astrobiological evolution in putative sub-surface oceans.

Cooper, John F.; Johnson, Robert E.; Mauk, Barry H.; Garrett, Henry B.; Gehrels, Neil

2001-01-01

190

Radiolysis study of actinide complexing agent by irradiation with helium ion beam  

NASA Astrophysics Data System (ADS)

?-Radiolysis of N, N, N', N'-tetraoctyldiglycolamide (TODGA) in n-dodecane was investigated by the irradiation with helium ion beam provided by a tandem accelerator. The radiation chemical yield for the degradation of TODGA by helium ion beam irradiation was less than that by ?-rays irradiation. It is considered that the radical cations of n-dodecane, which contribute to the charge transfer reaction with the TODGA molecules, decrease by recombination in track by high LET radiations such as ?-particles.

Sugo, Yumi; Taguchi, Mitsumasa; Sasaki, Yuji; Hirota, Koichi; Kimura, Takaumi

2009-12-01

191

Comparison of swelling for structural materials on neutron and ion irradiation  

SciTech Connect

The swelling of V-base alloys, Type 316 stainless steel, Fe-25Ni-15Cr alloys, ferritic steels, Cu, Ni, Nb-1% Zr, and Mo on neutron irradiation is compared with the swelling for these materials on ion irradiation. The results of this comparison show that utilization of the ion-irradiation technique provides for a discriminative assessment of the potential for swelling of candidate materials for fusion reactors.

Loomis, B.A.

1986-03-01

192

Sympathetic ophthalmia complicating helium ion irradiation of a choroidal melanoma  

SciTech Connect

Sympathetic ophthalmia was diagnosed 49 months after helium ion irradiation of a left choroidal melanoma. The patient maintained good vision until 18 months after therapy, when she developed neovascular glaucoma. This complication required multiple therapeutic procedures, including topical anti-inflammatory and antiglaucomatous drops, 360 degrees peripheral panretinal cryoblation, and a single 180 degrees application of inferior cyclocryotherapy over a 2 1/2-year period. Four weeks after the cyclocryotherapy, inflammation was noted in both eyes, and, one month later, enucleation of the left sympathogenic eye was performed. Serial histopathologic sections showed a full-thickness, fibrovascular, scleral scar and tantalum marker ring suture without uveal incarceration. Penetrating surgical trauma, a uveal melanoma, and multiple nonpenetrating treatments resulted in the development of sympathetic ophthalmia.

Fries, P.D.; Char, D.H.; Crawford, J.B.; Waterhouse, W.

1987-11-01

193

Sympathetic ophthalmia complicating helium ion irradiation of a choroidal melanoma.  

PubMed

Sympathetic ophthalmia was diagnosed 49 months after helium ion irradiation of a left choroidal melanoma. The patient maintained good vision until 18 months after therapy, when she developed neovascular glaucoma. This complication required multiple therapeutic procedures, including topical anti-inflammatory and antiglaucomatous drops, 360 degrees peripheral panretinal cryoblation, and a single 180 degrees application of inferior cyclocryotherapy over a 2 1/2-year period. Four weeks after the cyclocryotherapy, inflammation was noted in both eyes, and, one month later, enucleation of the left sympathogenic eye was performed. Serial histopathologic sections showed a full-thickness, fibrovascular, scleral scar and tantalum marker ring suture without uveal incarceration. Penetrating surgical trauma, a uveal melanoma, and multiple nonpenetrating treatments resulted in the development of sympathetic ophthalmia. PMID:3675290

Fries, P D; Char, D H; Crawford, J B; Waterhouse, W

1987-11-01

194

Response of nanostructured ferritic alloys to high-dose heavy ion irradiation  

NASA Astrophysics Data System (ADS)

A latest-generation aberration-corrected scanning/transmission electron microscope (STEM) is used to study heavy-ion-irradiated nanostructured ferritic alloys (NFAs). Results are presented for STEM X-ray mapping of NFA 14YWT irradiated with 10 MeV Pt to 16 or 160 dpa at -100 °C and 750 °C, as well as pre-irradiation reference material. Irradiation at -100 °C results in ballistic destruction of the beneficial microstructural features present in the pre-irradiated reference material, such as Ti-Y-O nanoclusters (NCs) and grain boundary (GB) segregation. Irradiation at 750 °C retains these beneficial features, but indicates some coarsening of the NCs, diffusion of Al to the NCs, and a reduction of the Cr-W GB segregation (or solute excess) content. Ion irradiation combined with the latest-generation STEM hardware allows for rapid screening of fusion candidate materials and improved understanding of irradiation-induced microstructural changes in NFAs.

Parish, Chad M.; White, Ryan M.; LeBeau, James M.; Miller, Michael K.

2014-02-01

195

Response of nanostructured ferritic alloys to high-dose heavy ion irradiation  

SciTech Connect

A latest-generation aberration-corrected scanning/transmission electron microscope (STEM) is used to study heavy-ion-irradiated nanostructured ferritic alloys (NFAs). Results are presented for STEM X-ray mapping of NFA 14YWT irradiated with 10 MeV Pt to 16 or 160 dpa at -100°C and 750°C, as well as pre-irradiation reference material. Irradiation at -100°C results in ballistic destruction of the beneficial microstructural features present in the pre-irradiated reference material, such as Ti-Y-O nanoclusters (NCs) and grain boundary (GB) segregation. Irradiation at 750°C retains these beneficial features, but indicates some coarsening of the NCs, diffusion of Al to the NCs, and a reduction of the Cr-W GB segregation (or solute excess) content. Ion irradiation combined with the latest-generation STEM hardware allows for rapid screening of fusion candidate materials and improved understanding of irradiation-induced microstructural changes in NFAs.

Parish, Chad M.; White, Ryan M.; LeBeau, James M.; Miller, Michael K.

2014-02-01

196

Heavy ion and X-ray irradiation alter the cytoskeleton and cytomechanics of cortical neurons  

PubMed Central

Heavy ion beams with high linear energy transfer exhibit more beneficial physical and biological performance than conventional X-rays, thus improving the potential of this type of radiotherapy in the treatment of cancer. However, these two radiotherapy modalities both cause inevitable brain injury. The objective of this study was to evaluate the effects of heavy ion and X-ray irradiation on the cytoskeleton and cytomechanical properties of rat cortical neurons, as well as to determine the potential mechanism of neuronal injury after irradiation. Cortical neurons from 30 new-born mice were irradiated with heavy ion beams at a single dose of 2 Gy and X-rays at a single dose of 4 Gy; subsequent evaluation of their effects were carried out at 24 hours after irradiation. An immunofluorescence assay showed that after irradiation with both the heavy ion beam and X-rays, the number of primary neurons was significantly decreased, and there was evidence of apoptosis. Radiation-induced neuronal injury was more apparent after X-irradiation. Under atomic force microscopy, the neuronal membrane appeared rough and neuronal rigidity had increased. These cell changes were more apparent following exposure to X-rays. Our findings indicated that damage caused by heavy ion and X-ray irradiation resulted in the structural distortion and rearrangement of the cytoskeleton, and affected the cytomechanical properties of the cortical neurons. Moreover, this radiation injury to normal neurons was much severer after irradiation with X-rays than after heavy ion beam irradiation. PMID:25206772

Du, Yuting; Zhang, Jie; Zheng, Qian; Li, Mingxin; Liu, Yang; Zhang, Baoping; Liu, Bin; Zhang, Hong; Miao, Guoying

2014-01-01

197

Modifications of the magnetic properties of ferrites by swift heavy ion irradiations  

NASA Astrophysics Data System (ADS)

Single crystal plates of ferrimagnetic yttrium iron garnet (111)-YIG:Si (Y3Fe4.94Si0.06O12) and barium hexaferrite (00.1)-BaM (BaFe12O19) or (00.1)-BaM:Co,Ti (BaFe9.1Co1.4Ti1.5O19) are irradiated with swift heavy ions (3.8 GeV 129Xe or 6.0 GeV 208Pb) in the electronic slowing down regime, above the threshold (?20 keV nm-1) of formation of continuous and homogeneous cylindrical amorphous tracks. The modifications of the magnetic properties are studied by 57Fe Mössbauer spectroscopy and ac magnetic permeability measurements versus ion fluence. In the doped crystals having a planar magnetic anisotropy (YIG:Si and BaM:Co,Ti), the room-temperature Mössbauer spectra show that the magnetization is flipped perpendicularly to the sample plane at a critical amorphous fraction around 30% in both compounds. This corresponds to a 90% drop of the measured in-plane magnetic permeability. No such effect is seen in the undoped BaM samples with the axial [00.1] anisotropy. These data are interpreted by a magnetomechanical effect generated by the stress field induced by the amorphous tracks in the sample plane which flips the magnetization along the track-axis direction when the stress-induced anisotropy constant surpasses the pristine crystal anisotropy constant at the critical amorphous fraction. In the case of YIG:Si single crystal, a track-induced anisotropy field around 0.1 T is deduced from the Mössbauer spectra under a magnetic field applied in the sample (111) plane which rotates the magnetization back to the easy <111> magnetization axis lying near the sample (111) plane in a reversible manner. The magnetic ordering of amorphous YIG:Si below 70 K is also studied by Mössbauer spectroscopy under high magnetic field (5 T). A two-dimensional Bruggeman model used for the calculation of the permeability of the crystal+amorphous track composites yields track-core radii larger by about 40% than the values previously obtained for both compounds by Mössbauer spectroscopy. We think that such discrepancies show that the samples cannot be treated like standard two-phase composites since the undamaged crystal undergoes a variable stress field depending on the damaged fraction.

Costantini, Jean-Marc; Studer, Francis; Peuzin, Jean-Claude

2001-07-01

198

Formation of TiO{sub 2} nanorods by ion irradiation  

SciTech Connect

Ion beam irradiation is a powerful method to fabricate and tailor the nanostructured surface of materials. Nanorods on the surface of single crystal rutile TiO{sub 2} were formed by N{sup +} ion irradiation. The dependence of nanorod morphology on ion fluence and energy was elaborated. With increasing ion fluence, nanopores grow in one direction perpendicular to the surface and burst finally to form nanorods. The length of nanorods increases with increasing ion energy under same fluence. The development of the nanorod structure is originated from the formation of the nanopores while N{sub 2} bubbles and aggregation of vacancies were responsible for the formation of nanopores and nanorods. Combining C{sup +} ion irradiation and post-irradiation annealing experiments, two qualitative models are proposed to explain the formation mechanism of these nanorods.

Zheng, X. D.; Ren, F., E-mail: fren@whu.edu.cn; Cai, G. X.; Hong, M. Q.; Xiao, X. H.; Wu, W.; Liu, Y. C.; Li, W. Q.; Ying, J. J.; Jiang, C. Z. [School of Physics and Technology, Center for Ion Beam Application and Center for Electron Microscopy, Wuhan University, Wuhan 430072 (China)

2014-05-14

199

Controlled shape modification of embedded Au nanoparticles by 3 MeV Au2+-ion irradiation  

NASA Astrophysics Data System (ADS)

Shape modification of embedded Au nanoparticles by 3 MeV Au2+-ion irradiation has been studied by cross-sectional transmission electron microscopy (XTEM). The ion irradiation on spherical Au nanoparticles shallowly-embedded in SiO2 caused a well-controlled transformation of shape to ellipsoidal. Satellite nanoparticles of smaller sizes were found to nucleate around the ellipsoids. Rapid growth of the ellipsoidal nanoparticles was observed as the applied fluence increased from 3 × 1015 to 7 × 1015 ions cm-2. The XTEM study also revealed the crystallinity of the ellipsoids formed by MeV ion irradiation. Reduction in the surface plasmon resonance (SPR) peak intensity in the optical absorption spectrum indicates partial dissolution of the spherical nanoparticles by ion irradiation. We have thus obtained a unique near-surface structure of ellipsoidal nanoparticles. The results are discussed in terms of effects of ion energy deposition and inverse Ostwald ripening.

Datta, D. P.; Takeda, Y.; Amekura, H.; Sasase, M.; Kishimoto, N.

2014-08-01

200

Superlattice-like stacking fault array in ion-irradiated GaN  

SciTech Connect

Controlling defects in crystalline solids is of technological importance for realizing desirable materials properties. Irradiation with energetic particles is useful for designing the spatial distribution and concentration of defects in materials. Here, we performed ion irradiation into hexagonal GaN with the wurtzite structure and demonstrated the spontaneous formation of superlattice-like stacking fault arrays. It was found that the modulation period can be controlled by irradiation conditions and post-irradiation heat treatments.

Ishimaru, Dr. Manabu [Osaka University; Usov, Igor Olegovich [ORNL; Zhang, Yanwen [ORNL; Weber, William J [ORNL

2012-01-01

201

Shape transformation of Sn nanocrystals induced by swift heavy-ion irradiation and the necessity of a molten ion track  

SciTech Connect

We report on the spherical to rodlike shape transformation of Sn nanocrystals (NCs) embedded in amorphous SiO{sub 2} following irradiation with 185 MeV Au ions. Consistent with previous reports for other metals, transmission electron microscopy demonstrates that under irradiation, Sn NCs larger than a critical size (11 nm) elongate parallel to the incident ion direction, while smaller particles remain spherical. Irradiation-induced NC dissolution is significant, as evident from the formation of smaller NCs in place of their original larger counterparts. Using formation conditions that yield Sn NCs at the amorphous-SiO{sub 2}/crystalline-Si interface, we show that the irradiation-induced shape change occurs only within the SiO{sub 2} layer, in the direction opposite to that of the incident ions. We suggest this demonstrates the necessity of a molten ion track and provides further evidence for an elongation process involving NC melting and flow.

Giulian, R.; Araujo, L. L.; Sprouster, D. J.; Kluth, P.; Byrne, A. P.; Ridgway, M. C. [Research School of Physics and Engineering, Australian National University, Canberra, ACT 0200 (Australia); Kremer, F.; Fichtner, P. F. P. [Instituto de Fisica, Universidade Federal do Rio Grande do Sul, Av. Bento Goncalves 9500, Ciaxa Postal 1501, CEP 91501-970, Porto Alegre, Rs (Brazil)

2010-09-15

202

Structural modifications of low-energy heavy-ion irradiated germanium  

SciTech Connect

Heavy-ion irradiation of crystalline germanium (c-Ge) results in the formation of a homogeneous amorphous germanium (a-Ge) layer at the surface. This a-Ge layer undergoes structural modification such as a strong volume expansion accompanied by drastic surface blackening with further ion irradiation. In the present paper we investigate the mechanism of this ion-induced structural modification in a-Ge basically for the irradiation with I ions (3 and 9 MeV) at room and low temperature as a function of ion fluence for the ion incidence angles of {Theta}=7 deg. and {Theta}=45 deg. For comparison, Ag- and Au-ion irradiations were performed at room temperature as a function of the ion fluence. At fluences two orders of magnitude above the amorphization threshold, morphological changes were observed for all irradiation conditions used. Over a wide range of ion fluences we demonstrate that the volume expansion is caused by the formation of voids at the surface and in the depth of the projected ion range. At high ion fluences the amorphous layer transforms into a porous structure as established by cross section and plan view electron microscopy investigations. However, the formation depth of the surface and buried voids as well as the shape and the dimension of the final porous structure depend on the ion fluence, ion species, and irradiation temperature and will be discussed in detail. The rate of the volume expansion (i.e., porous layer formation) depends linearly on the value of {epsilon}{sub n}. This clearly demonstrates that the structural changes are determined solely by the nuclear energy deposited within the amorphous phase. In addition, at high ion fluences all perpendicular ion irradiations lead to a formation of a microstructure at the surface, whereas for nonperpendicular ion irradiations a nonsaturating irreversible plastic deformation (ion hammering) without a microstructure formation is observed. For the irradiation with ion energies of several MeV, the effect of plastic deformation shows a linear dependence on the ion fluence. Based on these results, we provide an explanation for the differences in surface morphology observed for different angles of incidence of the ion beam will be discussed in detail.

Steinbach, T.; Wernecke, J.; Wesch, W. [Institut fuer Festkoerperphysik, Friedrich-Schiller-Universitaet Jena, Max-Wien-Platz 1, D-07743 Jena (Germany); Kluth, P.; Ridgway, M. C. [Australian National University, Research School of Physics and Engineering, Canberra (Australia)

2011-09-01

203

Tailoring magnetism in CoNi films with perpendicular anisotropy by ion irradiation  

SciTech Connect

This paper reports on the influence of ion irradiation on the magnetic properties of Co/Ni multilayers with perpendicular magnetic anisotropy (PMA). This material is a very promising candidate for ultrahigh density spintronic applications since it exhibits high polarization and low damping parameters. We show that PMA can be tailored in a controlled way by using uniform He{sup +} ion irradiation or focused Ga{sup +} ion beam.

Stanescu, D.; Ravelosona, D.; Mathet, V.; Chappert, C. [Institut d'Electronique Fondamentale, UMR CNRS 8622, Universite Paris Sud, 91405 Orsay Cedex (France); Samson, Y.; Beigne, C. [CEA Grenoble, DRFMC/SP2M, 17 avenue des Martyrs, 38054 Grenoble (France); Vernier, N.; Ferre, J. [Laboratoire de Physique de Solide, UMR CNRS 8502, Universite Paris Sud, 91405 Orsay Cedex (France); Gierak, J.; Bouhris, E. [Laboratoire de Photonique et de Nanostructures-CNRS, route de Nozay, 91460 Marcoussis (France); Fullerton, E. E. [Center for Magnetic Recording Research, University of California, San Diego, La Jolla, California 92093-0401 (United States)

2008-04-01

204

KeV-MeV ion irradiation of polyvinylidene fluoride (PVDF) films  

Microsoft Academic Search

Semicrystalline polyvinylidene fluoride (PVDF) films have been irradited with different ion beams and energies ranging between 0.1 keV\\/amu and 6 MeV\\/amu. Polymer modifications induced by the ion irradiation, for electronic and nuclear energy stopping, have been investigated in situ by a highly sensitive quadrupole mass spectrometer. Ion irradiation of PVDF produced ejection of H2 and HF molecules with a high

L. Torrisi; G. Ciavola; R. Percolla; F. Benyaich

1996-01-01

205

[Ion-beam irradiated ePTFE for an artificial dura mater].  

PubMed

Expanded polytetrafluoroethylene (ePTFE) is a stable polymer and widely used as a prosthesis because of its chemical inertness. However, ePTFE as an artificial dura mater is often associated with postoperative leakage of the cerebrospinal fluid (CSF) due to its very low adhesiveness to fibrin glue and surrounding tissue. The surfaces of ePTFE were modified by ion-beam irradiation in order to improve tissue adhesiveness. The morphological changes of ePTFE that was irradiated with 150 keV-He+, Net, Ar+ and Kr+ ions applied at a rate of 1 x 10(14), 5 x 10(14) and 1 x 10(15) ions/cm2 were examined with scanning electron microscopy. Next, surrounding tissue reactions to the implanted ePTFE into the rabbit calvarial defects were analyzed at intervals from 1 week up to 1 month. The micromesh structures of the ePTFE were destroyed by ion-beam irradiation, and the depth and width of the gaps increased with heavy particle ion and irradiated fluence. In an implantation study using experimental rabbits, a dura defect was patched with four types of ion-beam irradiated ePTFE with different in irradiation fluence. A CSF leakage was observed in the rabbit covered with non-irradiated ePTFE, but, CSF leakage did not occur in any of the rabbits covered with ion-beam irradiated ePTFE that adhered in a water-tight manner to surrounding tissues. Histological study indicated that fibroblast-like cells had infiltrated and anchored the gaps in the ion-beam irradiated ePTFE. Ar+ or Kr+ with 1 x 10(15) ions/cm2 irradiated ePTFE had the highest adhesiveness and produced the best healing of dura defects. PMID:14598645

Takahashi, Noriyoshi; Ujiie, Hiroshi; Suzuki, Yoshiaki; Iwaki, Masaya; Hori, Tomokatsu

2003-10-01

206

Behaviour of P, Si, Ni impurities and Cr in self ion irradiated Fe-Cr alloys - Comparison to neutron irradiation  

NASA Astrophysics Data System (ADS)

This paper presents an atom probe tomography study of phase transformation and solute segregation in Fe-Cr alloys of low purity under self-ion irradiation. Fe-9%Cr and Fe-12%Cr were irradiated at 100 °C, 300 °C and 420 °C at a dose of 0.5 dpa. Homogeneously distributed clusters enriched in Cr, P, Si and Ni are shown to form at 300 °C and 420 °C but not at 100 °C. Study of the evolution of the segregation intensities of Cr, Si and P in the clusters with temperature under ion irradiation indicates that they form by a radiation induced mechanism. No ?? clusters were observed whatever the irradiation temperature whereas they were observed in the same alloys after neutron irradiation at 300 °C at 0.6 dpa. Comparison of the solute cluster composition after ion irradiation and neutron irradiation, suggests that P atoms could play an important role in the appearance of the solute clusters by stabilizing point defect clusters that could later be enriched in Ni, Si and Cr.

Pareige, C.; Kuksenko, V.; Pareige, P.

2015-01-01

207

Three-dimensional morphology evolution of SiO2 patterned films under MeV ion irradiation  

E-print Network

Three-dimensional morphology evolution of SiO2 patterned films under MeV ion irradiation Kan OtaniO2 stripes on Si substrates induced by 3 MeV O++ ion irradiation. We develop a 3D constitutive evolution in complex three-dimensional structures under MeV ion irradiation. © 2006 American Institute

Hutchinson, John W.

208

Ion beam irradiation effects on Ge nanocrystals synthesized by using RF sputtering followed by RTA  

NASA Astrophysics Data System (ADS)

Here we report the effects of ion beam irradiation on Ge nanocrystals (NCs) embedded in SiO2 matrix. The Ge NCs embedded in silicon oxide matrix have been synthesized using RF magnetron co-sputtering technique followed by rapid thermal annealing. Eventually, Ge NCs were irradiated by 120 MeV Ag ions with various fluences at room temperature. X-ray diffraction patterns indicate the decrease in average size of Ge NCs with increase in irradiation fluence. Raman scattering spectra showed a peak of Ge-Ge optical phonon vibrational mode shifted towards lower wavenumber side upon irradiation with respect to its bulk value, which is due to quantum confinement of optical phonons in the NCs. This blue shift also reflects decrease in the size of NCs upon irradiation. Change of NC size with the increase of irradiation fluence can be explained on the basis of energy deposited by incident ion inside the target material.

Saikiran, V.; Srinivasa Rao, N.; Devaraju, G.; Chang, G. S.; Pathak, Anand P.

2013-11-01

209

Xe- and U-tracks in apatite and muscovite near the etching threshold  

NASA Astrophysics Data System (ADS)

Ion irradiation of a wedge-shaped Durango apatite backed by a mica detector allows investigating ion track ranges and etching properties at different points along the tracks. Transmission profiles obtained by irradiation with 2 × 106 cm-2 11.1 MeV/amu 132Xe and 2 × 106 cm-2 11.1 MeV/amu 238U parallel to the apatite c-axis correspond to ranges calculated with SRIM (Xe: 76.3 ?m; U: 81.1 ?m). However, the measured profiles show much greater etchable track-length variations than the calculated longitudinal straggles. The probable cause is that the length deficit exhibits significant variation from track to track. The measured length deficit in muscovite is in agreement with most existing data. In contrast, the length deficit in apatite appears to be close to zero, which is in conflict with all earlier estimates. This probably results from the etching properties of the apatite basal face, which permit surface-assisted sub-threshold etching of track sections in the nuclear stopping regime. These sections are not accessible from the opposite direction, i.e. by etching towards the endpoint of the tracks or in the direction of the ion beam. This conclusion is supported by the fact that linear dislocations are revealed in apatite basal faces and by the observation of imperfect etch pits that are separated from the etched ion track channel by a section that appears unetched under the microscope.

Wauschkuhn, Bastian; Jonckheere, Raymond; Ratschbacher, Lothar

2015-01-01

210

Swift heavy ion irradiation acts as a size filter to Ag nanoparticles embedded in silica glass  

NASA Astrophysics Data System (ADS)

The swift heavy ion (SHI) irradiation using as a tool for the ion-beam-shaping technique has attracted much attention in recently years, which can transform spherical metal nanoparticles (Nps) to prolate spheroids, nanorods or nanowires, with the elongation along the beam direction. In the present paper, we show that SHI irradiation can also act as a size filter to Ag Nps embedded in silica glass. In experiment, Ag Nps were introduced into silica glass by Ag ion implantation. Subsequently, 73 MeV Ca ions were used to irradiate the samples contained Ag Nps to different fluences. The direction of incident ions is perpendicular to sample surface. The surface plasmon resonance (SPR) absorbance peak of Ag Nps shifts to short wavelength with increase of irradiation fluence, meanwhile, the full width at half maximum (FWHM) of SPR peak decreases with increase of irradiation fluence. The decrease of FWHM indicates the reduction of Ag Nps size dispersion. TEM results show that Ag Nps smaller than 2.0 nm dissolve during irradiation, only Ag Nps larger than 2.0 nm survive and distribute in a narrow region. High energy Ca ion irradiation seems to act as a size filter. From TEM micrographs the size dispersion of Ag Nps is reduced comparing with that before irradiation, which is consistent with optical results.

Yang, Yitao; Zhang, Chonghong; Song, Yin; Gou, Jie; Zhang, Liqing; Meng, Yancheng; Zhang, Hengqing; Ma, Yizhun

2013-08-01

211

Double beta decay searches of Xe-134, Xe-126 and Xe-124 with large scale Xe detectors  

E-print Network

The sensitivity for double beta decay studies of Xe-134 and Xe-124 is investigated assuming a potential large scale Xe experiment developed for dark matter searches depleted in Xe-136. The opportunity for an observation of the 2nu double beta decay of Xe-134 is explored for various scenarios. A positive observation should be possible for all calculated nuclear matrix elements. The detection of 2$\

N. Barros; J. Thurn; K. Zuber

2014-09-29

212

Co-irradiation effects of intense heavy ions and photons on surface modification of insulators  

NASA Astrophysics Data System (ADS)

Co-irradiation effects of ions and photons on insulators have been studied to explore electronic excitation effects on surface modification. Ion implantation of MeV-Cu ions and green-laser irradiation was conducted to a-SiO 2 (820 ppm OH -) and spinel MgO·2.4(Al 2O 3). The dose rate varied from 2 to 10 ?A/cm2 for Cu ions of 3 MeV and from 0.05 to 0.2 J/cm2· pulse at 10 Hz for YAG-SHG laser, for a period corresponding to 3×10 16 ions/cm2. Atomic-force microscopy (AFM) was conducted to evaluate the surface morphology. Optical absorption was measured in a photon energy range from 0.5 to 6.5 eV. Single irradiation, either Cu ion-alone or laser-alone, caused few discernible changes of surface morphology. Co-irradiation of ions and photons at high power densities caused significant changes in the surface texture with an increase in surface roughness. Optical absorbance of the co-irradiated specimens also showed a change larger than that of sequentially irradiated ones. The results indicate that nonlinear synergistic effects are induced by the co-irradiation and may develop to a new modification method.

Kishimoto, N.; Okubo, N.; Lee, C. G.; Umeda, N.; Takeda, Y.

2001-04-01

213

In situ TEM ion irradiation and implantation effects on Au nanoparticle morphologies.  

PubMed

Energetic heavy and light ion effects on gold nanoparticles were probed by irradiating 20 and 60 nm diameter nanoparticles with either 3 MeV Cu(3+) or 10 keV He(+) ions in situ inside of a transmission electron microscope. Both ion species caused sintering, agglomeration, and ablation of the nanoparticles via sputtering, although at different rates. PMID:24584417

Bufford, Daniel; Pratt, Sarah H; Boyle, Timothy J; Hattar, Khalid

2014-07-21

214

Using HaXe  

Microsoft Academic Search

haXe is a high-level programming language for web development. It can be compiled into .js files for JavaScript developers\\u000a or into .swf files for Flash, and it also supports the Neko virtual machine. Before going into the details of haXe, I’ll explain\\u000a how it came to be and how it is related to the evolution of Flash, ActionScript, and some

Nicolas Cannasse

215

Modifications of SiC under high fluence Kr-ion irradiation at different temperatures  

NASA Astrophysics Data System (ADS)

4 MeV Kr-ions were irradiated into 6H-SiC single crystals with fluences from 1.0 × 1016 to 5.0 × 1016 cm-2 at room temperature, 300 °C and 500 °C, respectively (5.0 × 1016 cm-2 at 550 °C). The irradiation-induced modifications were measured by Atomic Force Microscope (AFM), Raman Spectrometer and Nano-indentation measurements. It was observed that the surface of RT-irradiated samples became rough as a result of crystallizing to amorphous state. The result of Raman spectra indicates that different migration behaviors of Si and C interstitials at different temperatures could have an effect on the stoichiometry of irradiated samples. It was also observed that the hardness of irradiated samples is higher than that of un-irradiated ones at high temperatures, with increase at low fluence and then decrease at high fluence. Finally, the effects of irradiation temperature and ion fluence are discussed.

Zang, Hang; Yang, Tao; Guo, Daxi; Xi, Jianqi; He, Chaohui; Wang, Zhiguang; Shen, Tielong; Pang, Lilong; Yao, Cunfeng; Zhang, Peng

2013-07-01

216

Improved photoelectrochemical response of haematite by high energy Ag9+ ions irradiation  

NASA Astrophysics Data System (ADS)

Haematite (?-Fe2O3) thin films deposited on a conducting glass substrate were irradiated with 120 MeV Ag9+ ions with increasing ion fluences. Their structural evolution was determined by x-ray diffraction and Raman spectroscopy. The irradiation of the samples of ?-Fe2O3 was found to be effective in improving its photoelectrochemical response. The film irradiated at a fluence of 1 × 1013 ions cm-2 showed a significantly higher photocurrent density than the unirradiated ?-Fe2O3. This effect is correlated with the transition from the ?-Fe2O3 to the Fe3O4 phase and the reduction in grain size that were observed on irradiation with Ag9+ ions. The measured flatband potential and donor density of the sample were also maximum at a fluence of 1 × 1013 ions cm-2.

Singh, Aadesh P.; Kumari, Saroj; Shrivastav, Rohit; Dass, Sahab; Satsangi, Vibha R.

2009-04-01

217

First multicharged ion irradiation results from the CUEBIT facility at Clemson University  

NASA Astrophysics Data System (ADS)

A new electron beam ion trap (EBIT) based ion source and beamline were recently commissioned at Clemson University to produce decelerated beams of multi- to highly-charged ions for surface and materials physics research. This user facility is the first installation of a DREEBIT-designed superconducting trap and ion source (EBIS-SC) in the U.S. and includes custom-designed target preparation and irradiation setups. An overview of the source, beamline, and other facilities as well as results from first measurements on irradiated targets are discussed here. Results include extracted charge state distributions and first data on a series of irradiated metal-oxide-semiconductor (MOS) device targets. For the MOS devices, we show that voltage-dependent capacitance can serve as a record of the electronic component of ion stopping power for an irradiated, encapsulated oxide target.

Shyam, R.; Kulkarni, D. D.; Field, D. A.; Srinadhu, E. S.; Cutshall, D. B.; Harrell, W. R.; Harriss, J. E.; Sosolik, C. E.

2015-01-01

218

Precipitation of the Carbides $M_{23}C_{6}$ under the Irradiation by High Energy Heavy Ions  

E-print Network

Carbide M_{23}C_{6} precipitation process in chromium-nickel steels 12H18N9ô and 00H17N14í2 irradiated with high energy heavy Ar^{+6} ions at 625^{o}ó has been studied. It was found that ion irradiation accelerates carbide M_{23}C_{6} precipitation in comparison to thermal annealing. It was shown that composition of carbides formed by irradiation in 00H17N14í2 steel formed under irradiation differs from composition of carbides precipitated during thermal ageing.

Hofmann, A; Semina, V K; Kochanski, T

2000-01-01

219

Microstructure and thermal desorption of deuterium in heavy-ion-irradiated pure tungsten  

NASA Astrophysics Data System (ADS)

To understand the fundamental processes of deuterium retention and desorption of irradiated plasma facing materials, thermal desorption of deuterium in pure W with and without ion irradiation up to 2 dpa by 2.4 MeV Cu2+ have been investigated. After the ion irradiation at room temperature, high density of small interstitial typed dislocation loops and also nano-voids due to cascade collisions were detected by TEM observation. Thermal desorption of spectra of D showed that fine vacancy clusters are formed even at low fluence and at room temperature irradiation, these defects act as the strong trapping center of deuterium in the temperature range of 660-900 K.

Watanabe, Hideo; Futagami, Naoki; Naitou, Shiori; Yoshida, Naoaki

2014-12-01

220

Ion irradiation-induced bimodal surface morphology changes in InSb.  

PubMed

High-energy ion irradiation of InSb results in the formation of bimodal surface structures, namely microscale hillock-like structures fully composed of nanoscale fibers. Analysis of the surface structures by a wide range of electron microscopy techniques reveals correlations between the irradiation conditions, such as the ion energy and fluence, and changes in the surface morphology. Sputtering effects play a key role in the integrity of the surface layer with increasing ion fluence. Possible mechanisms responsible for the morphological transformation are discussed, including both irradiation-induced and mechanical effects. PMID:20639585

Perez-Bergquist, Alejandro G; Li, Kundar; Zhang, Yanwen; Wang, Lumin

2010-08-13

221

EPR analysis of the effects of accelerated carbon ion and fast neutron irradiations on table sugar.  

PubMed

Table sugar samples were irradiated with accelerated carbon ions and fast neutrons. Electron paramagnetic resonance (EPR) analysis performed after the irradiation revealed a complex spectrum similar to that observed after gamma-ray irradiations. The total concentration of the paramagnetic centers induced by accelerated carbon ions and neutrons was proportional to the absorbed dose. Good stability of the produced free radicals was observed for a typical period of sugar storage. Sugar was more sensitive to accelerated carbon ions than to neutrons. The results show that table sugar can be a useful material for dosimetry in the case of a radiation accident. PMID:19467878

Mikou, M; Benzina, S; Bischoff, P; Denis, J M; Gueulette, J

2009-09-01

222

In-situ observation and atomic resolution imaging of the ion irradiation induced amorphisation of graphene  

PubMed Central

Ion irradiation has been observed to induce a macroscopic flattening and in-plane shrinkage of graphene sheets without a complete loss of crystallinity. Electron diffraction studies performed during simultaneous in-situ ion irradiation have allowed identification of the fluence at which the graphene sheet loses long-range order. This approach has facilitated complementary ex-situ investigations, allowing the first atomic resolution scanning transmission electron microscopy images of ion-irradiation induced graphene defect structures together with quantitative analysis of defect densities using Raman spectroscopy. PMID:25284688

Pan, C.-T.; Hinks, J. A.; Ramasse, Q. M.; Greaves, G.; Bangert, U.; Donnelly, S. E.; Haigh, S. J.

2014-01-01

223

Investigation of swelling induced by heavy ion and neutron irradiation in SiC  

NASA Astrophysics Data System (ADS)

In this paper, the single crystal samples of 6H-SiC were irradiated by 4 MeV Kr-ions, with irradiation fluences from 1.0 × 1016 to 5.0 × 1016 cm-2 at room temperature, 300 °C and 500 °C respectively (5.0 × 1016 cm-2 at 550 °C). The irradiation-induced swelling was strictly measured by X-ray Diffraction (XRD) and 3D surface profile. It is shown that the swelling strongly depends on the irradiation temperature and the ion fluence, and the magnitudes of volumetric swelling saturate at approximately 3.3% and 2.4% at the irradiation temperatures of 300 °C and 500 °C, respectively. Those magnitudes are higher than the neutrons' data at the same temperature. Furthermore, this paper exhaustively investigates the differences and similarities between heavy-ion and neutron irradiation-induced swelling; we suppose that the larger saturate swelling is caused by excess substitute vacancies in Si sub-lattice induced by Kr ions. Finally, by systematically analyzing the swelling data, it was speculated that the heavy-ion irradiation needs a higher dose to saturate the swelling compared to neutron at the same irradiation temperatures.

Zang, Hang; Guo, Daxi; Shen, Tielong; He, Chaohui; Wang, Zhiguang; Pang, Lilong; Yao, Cunfeng; Yang, Tao

2013-02-01

224

Impact of high dose krypton ion irradiation on corrosion behavior of laser beam welded zircaloy-4  

SciTech Connect

In order to study the effect of krypton ion irradiation on the aqueous corrosion behavior of laser beam welded zircaloy-4 (LBWZr4), the butt weld joint of zircaloy-4 was made by means of a carbon dioxide laser, subsequently the LBWZr4 samples were irradiated with Kr ions using an accelerator at an energy of 300 keV, with a dose range from 1 x 10{sup 15} to 3 x 10{sup 16} ions/cm{sup 2} at about 150 deg. C. Three-sweep potentiodynamic polarization measurement was employed to evaluate the aqueous corrosion behavior of Kr-irradiated LBWZr4 in a 0.5 M H{sub 2}SO{sub 4} solution. Scanning electron microscopy (SEM) was used to examine the surface topography of the Kr-irradiated LBWZr4 after the potentiodynamic polarization measurement. Transmission electron microscopy was employed to examine the change of microstructures in the irradiated surface. The polarization tests showed that compared with the passive current density of the as-received LBWZr4, the Kr-irradiated LBWZr4 is much lower; however, with the irradiation dose increasing from 1 x 10{sup 15} to 3 x 10{sup 16} ions/cm{sup 2}, the passive current density, closely related to the surface corrosion resistance, increased remarkably. The mechanism of the corrosion behavior transformation was due to the recrystallization of the amorphous phase induced by the lower ion irradiation.

Wan Qian [Department of Engineering Physics, Tsinghua University, Beijing100084 (China)]. E-mail: wanqian99@tsinghua.org.cn; Bai Xinde [Department of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Zhang Xiangyu [Department of Engineering Physics, Tsinghua University, Beijing100084 (China)

2006-02-02

225

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

NASA Astrophysics Data System (ADS)

Al-Mg-Si alloys were irradiated with 5.4 MeV Al ions, 7.3 MeV Fe ions, 10 MeV I ions, and 16 MeV 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).

Ueyama, D.; Saitoh, Y.; Hori, F.; Kaneno, Y.; Nishida, K.; Dohi, K.; Soneda, N.; Semboshi, S.; Iwase, A.

2013-11-01

226

Comparison of UV and high-energy ion irradiation of methanol:ammonia ice  

NASA Astrophysics Data System (ADS)

Aims: The main goal of this work is to compare the effects induced in ices of astrophysical relevance by high-energy ions, simulating cosmic rays, and by vacuum ultraviolet (UV) photons. Methods: This comparison relies on in situ infrared spectroscopy of irradiated CH3OH:NH3 ice. Swift heavy ions were provided by the GANIL accelerator. The source of UV was a microwave-stimulated hydrogen flow discharge lamp. The deposited energy doses were similar for ion beams and UV photons to allow a direct comparison. Results: A variety of organic species was detected during irradiation and later during ice warm-up. These products are common to ion and UV irradiation for doses up to a few tens of eV per molecule. Only the relative abundance of the CO product, after ice irradiation, was clearly higher in the ion irradiation experiments. Conclusions: For some ice mixture compositions, the irradiation products formed depend only weakly on the type of irradiation, swift heavy ions, or UV photons. This simplifies the chemical modeling of energetic ice processing in space.

Muñoz Caro, G. M.; Dartois, E.; Boduch, P.; Rothard, H.; Domaracka, A.; Jiménez-Escobar, A.

2014-06-01

227

Effects of energetic ion irradiation on the magnetism of Fe-Ni Invar alloy  

NASA Astrophysics Data System (ADS)

The magnetic properties of Fe-Ni Invar alloys are significantly affected by ion irradiation. Au3+ with the energy of 16 MeV irradiation effects on the magnetism of Fe66Ni34 have been reported in this paper. Considering from the temperature variations of AC susceptibility of irradiated Fe66Ni34, Curie temperature of a part of sample increase with increasing incident ion fluence, and the magnetization of irradiated Fe66Ni34 is also increase. The FCC structure of Fe66Ni34 is not changed by ion irradiation; however peaks become broader with increasing ion fluence. It means that lattice fluctuations are generated owing to ion irradiation. However it cannot be considered that lattice fluctuations observed X-ray diffraction measurements are enough to increase the Curie temperature observed in AC susceptibility measurements. Then, we suggest as the considerable origin of increasing TC, atomic mixing effects owing to the ion irradiation. It might change the chemical ordering reported in the diffused scattering, such as Fe-Fe coupling.

Matsushita, M.; Akamatsu, S.; Matsushima, Y.; Iwase, A.

2013-11-01

228

Double beta decay searches of 134Xe, 126Xe and 124Xe with large scale Xe detectors  

NASA Astrophysics Data System (ADS)

The sensitivity for double beta decay studies of 134Xe and 124Xe is investigated assuming a potential large scale Xe experiment developed for dark matter searches depleted in 136Xe. The opportunity for an observation of the 2??? - decay of 134Xe is explored for various scenarios. A positive observation should be possible for all calculated nuclear matrix elements. The detection of 2? ECEC of 124Xe can be probed in all scenarios covering the theoretical predicted half-life uncertainties and a potential search for 126Xe is discussed. The sensitivity to {{? }+}EC decay of 124Xe is discussed and a positive observation might be possible, while {{? }+}{{? }+} decay still remains unobservable. The performed studies take into account solar pp–neutrino interactions, 85Kr beta decay and remaining 136Xe double beta decay as background components in the depleted detector.

Barros, N.; Thurn, J.; Zuber, K.

2014-11-01

229

Investigations of structural, dielectric and optical properties on silicon ion irradiated glycine monophosphate single crystals  

NASA Astrophysics Data System (ADS)

The 50 MeV silicon ion irradiation induced modifications on structural, optical and dielectric properties of solution grown glycine monophosphate (GMP) crystals were studied. The high-resolution X-ray diffraction study shows the unaltered value of integrated intensity on irradiation. The dielectric constant as a function of frequency and temperature was studied. UV-visible studies reveal the decrease in bandgap values on irradiation and presence of F-centers. The fluorescence spectrum shows the existence of some energy levels, which remains unaffected after irradiation. The scanning electron micrographs reveal the defects formed on irradiation.

Kanagasekaran, T.; Mythili, P.; Bhagavannarayana, G.; Kanjilal, D.; Gopalakrishnan, R.

2009-08-01

230

Nano-porosity in GaSb induced by swift heavy ion irradiation  

SciTech Connect

Nano-porous structures form in GaSb after ion irradiation with 185 MeV Au ions. The porous layer formation is governed by the dominant electronic energy loss at this energy regime. The porous layer morphology differs significantly from that previously reported for low-energy, ion-irradiated GaSb. Prior to the onset of porosity, positron annihilation lifetime spectroscopy indicates the formation of small vacancy clusters in single ion impacts, while transmission electron microscopy reveals fragmentation of the GaSb into nanocrystallites embedded in an amorphous matrix. Following this fragmentation process, macroscopic porosity forms, presumably within the amorphous phase.

Kluth, P., E-mail: patrick.kluth@anu.edu.au; Schnohr, C. S.; Giulian, R.; Araujo, L. L.; Lei, W.; Rodriguez, M. D.; Afra, B.; Bierschenk, T.; Ridgway, M. C. [Department of Electronic Materials Engineering, Research School of Physics and Engineering, Australian National University, Canberra, Australian Capital Territory 0200 (Australia); Sullivan, J.; Weed, R. [ARC Centre for Antimatter-Matter Studies, AMPL, Research School of Physics and Engineering, Australian National University, Canberra, Australian Capital Territory 0200 (Australia); Li, W.; Ewing, R. C. [Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, Michigan 48109-1005 (United States)

2014-01-13

231

Effect of Swift Heavy Ion Irradiation on Lithium Zinc Silicate Glasses: A Photoluminescence Study  

SciTech Connect

Lithium zinc silicate glasses with and without copper were prepared by melt-quench method and their luminescence characteristics after swift heavy ion irradiation has been investigated. Based on these studies it is established that both these glasses contain colour centres and the luminescence from such centres get significantly quenched once these samples get irradiated with 100 MeV swift heavy Ag{sup +} ions with a fluence of 10{sup 13} ions/cm{sup 2} at room temperature. Trapping of the charge carriers by the increased defect concentration brought about by irradiation is responsible for the decrease in the luminescence intensity from the irradiated samples. Copper in these glasses mainly exists as Cu{sup +} ions as revealed by the broad emission around 500 nm.

Jogad, M. S. [Sharanabasaveshwar College of Science, Gulbarga 585 103 (India); Jogad, R. M. [Department of Physics, Gulburga University, Gulbarga 585106 (India); Sudarsan, V. [Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Krishna, P. S. R. [Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Kothiyal, G. P. [Technical Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India)

2011-07-15

232

Investigation of Current Spike Phenomena During Heavy Ion Irradiation of NAND Flash Memories  

NASA Technical Reports Server (NTRS)

A series of heavy ion and laser irradiations were performed to investigate previously reported current spikes in flash memories. High current events were observed, however, none matches the previously reported spikes. Plausible mechanisms are discussed.

Oldham, Timothy R.; Berg, Melanie; Friendlich, Mark; Wilcox, Ted; Seidleck, Christina; LaBel, Kenneth A.; Irom, Farokh; Buchner, Steven P.; McMorrow, Dale; Mavis, David G.; Eaton, Paul H.; Castillo, James

2011-01-01

233

MICROSTRUCTURE EVOLUTION OF NANOCRYSTALLINE METALLIC THIN-FILMS UNDER ION-BEAM IRRADIATION.  

E-print Network

??The microstructural evolution of nanocrystalline metallic thin-films under ion irradiation, especially grain growth and second-phase precipitation, was studied with detailed in situ experiments, and a… (more)

Kaoumi, Djamel

2007-01-01

234

Cu Precipitates in Fe Ion Irradiated Fe-Cu Alloys Studied Using Positron Techniques  

NASA Astrophysics Data System (ADS)

In this paper, we summarized our recent experimental results on Fe-Cu model alloys irradiated by Fe ion. Two kinds of Fe-Cu alloys with 0.3%Cu and 0.6%Cu were prepared and irradiated by 2.5 MeV Fe ion at 573 K. Irradiation dose is 0.1 dpa and 1.2 dpa for each type alloy respectively. Positron annihilation techniques of slow positron beam were used to investigate the irradiation induced defects. Results show that the S parameters are higher in the specimens with high irradiation dose, but the intensity of Cu peaks of CDB is lower. It indicates that the precipitation of Cu atoms formed easily as lower irradiation dose.

Cao, X. Z.; Zhang, P.; Xu, Q.; Sato, K.; Tsuchida, H.; Cheng, G. D.; Wu, H. B.; Jiang, X. P.; Yu, R. S.; Wang, B. Y.; Wei, L.

2013-06-01

235

Structural, Dielectric and Temperature Dependent Raman Spectroscopic Studies on Swift Heavy Ion Irradiated Tgs Crystals  

NASA Astrophysics Data System (ADS)

Polar cleavage surface of tri-glycine sulphate (TGS) of important room temperature ferroelectric crystal irradiated with 100 MeV oxygen ion beam are characterized to understand the effect of irradiation on structural, dielectric and vibrational modes of the crystal. X-ray diffraction results show lattice parameters a and b in monoclinic unit cell decrease with increasing fluence, whereas parameter `c' increases. However, the irradiated crystal remains in monoclinic phase. Dielectric anomaly peak value associated with paraelectric—ferroelectric phase transition gets reduce with irradiation and Tc shift towards lower temperature. A comparison of the Raman spectra of unirradiated crystal with those irradiated in both paraelectric and ferroelectric phase reveals the molecular ion getting distorted as a result of irradiation.

Bajpai, P. K.; Shah, Deepak; Kumar, Ravi; Kumar, Ashok; Katiyar, R. S.

2011-11-01

236

Spatial ordering of nano-dislocation loops in ion-irradiated materials  

NASA Astrophysics Data System (ADS)

Defect microstructures formed in ion-irradiated metals, for example iron or tungsten, often exhibit patterns of spatially ordered nano-scale dislocation loops. We show that such ordered dislocation loop structures may form spontaneously as a result of Brownian motion of loops, biased by the angular-dependent elastic interaction between the loops. Patterns of spatially ordered loops form once the local density of loops produced by ion irradiation exceeds a critical threshold value.

Dudarev, S. L.; Arakawa, K.; Yi, X.; Yao, Z.; Jenkins, M. L.; Gilbert, M. R.; Derlet, P. M.

2014-12-01

237

Modifying the electronic structure of semiconducting single-walled carbon nanotubes by Ar+ ion irradiation  

Microsoft Academic Search

Local controllable modification of the electronic structure of carbon nanomaterials is important for the development of carbon-based nanoelectronics. By combining density-functional theory simulations with Ar-ion-irradiation experiments and low-temperature scanning tunneling microscopy and spectroscopy (STM\\/STS) characterization of the irradiated samples, we study the changes in the electronic structure of single-walled carbon nanotubes due to the impacts of energetic ions. As nearly

Antti Tolvanen; Gilles Buchs; Pascal Ruffieux; Pierangelo Gröning; Oliver Gröning; Arkady V. Krasheninnikov

2009-01-01

238

High-energy ion irradiation effects on the surfaces of silicon carbide and silicon nitride  

Microsoft Academic Search

High-energy ion irradiation effects on the surfaces of ?-silicon carbide (SiC) and hot-pressed silicon nitride (Si3N4) were studied by optical microscopy, surface profilometry, Auger electron spectroscopy, and transmission electron microscopy (TEM) techniques. Optical microscopy and surface profilometry revealed that 1-MeV Ni+ ion irradiation at a dose of 1×1016 cm?2 produces swelling and roughness on both SiC and Si3N4. Auger electron

R. S. Bhattacharya; A. K. Rai; P. P. Pronko

1987-01-01

239

Electron spin resonance investigations on ion beam irradiated single-wall carbon nanotubes  

Microsoft Academic Search

ESR investigations on single-wall carbon nanotubes irradiated with accelerated protons, helium ions, and neon ions are reported. All spectra were accurately simulated assuming that the resonance line is a convolution of up to 4 lines originating from catalyst residues, amorphous carbon, and electrons delocalized over the conducting domains of nanotubes. The faint line observed in irradiated nanotubes at g>2.25 was

A. R. Adhikari; H. Bakhru; P. M. Ajayan; R. Benson; M. Chipara

2007-01-01

240

Biophysical characteristics of HIMAC clinical irradiation system for heavy-ion radiation therapy  

Microsoft Academic Search

Purpose: The irradiation system and biophysical characteristics of carbon beams are examined regarding radiation therapy.Methods and Materials: An irradiation system was developed for heavy-ion radiotherapy. Wobbler magnets and a scatterer were used for flattening the radiation field. A patient-positioning system using X ray and image intensifiers was also installed in the irradiation system. The depth-dose distributions of the carbon beams

Tatsuaki Kanai; Masahiro Endo; Shinichi Minohara; Nobuyuki Miyahara; Hiroko Koyama-ito; Hiromi Tomura; Naruhiro Matsufuji; Yasuyuki Futami; Akifumi Fukumura; Takeshi Hiraoka; Yoshiya Furusawa; Koichi Ando; Masao Suzuki; Fuminori Soga; Kiyomitsu Kawachi

1999-01-01

241

Microstructural changes induced by low energy heavy ion irradiation in titanium silicon carbide  

E-print Network

Microstructural changes induced by low energy heavy ion irradiation in titanium silicon carbide, and it was validated on irradiated silicon carbide. The swelling of Ti3SiC2 was estimated to 2.2 ±0 to these working conditions, non-oxide refractory ceramics are required as fuel cladding. Thus, carbides turn out

Boyer, Edmond

242

ITEP HEAVY ION RFQ OUTPUT LINE UPGRADE FOR EXPERIMENTS OF REACTOR MATERIAL INVESTIGATION UNDER IRRADIATION  

Microsoft Academic Search

Development of new materials for future energy facilities with higher operating efficiency is a challenging and crucial task. However, full-scale testing of radiation hardness of reactor materials is quite sophisticated and difficult as it requires long session of reactor irradiation; moreover, induced radioactivity considerably complicates further investigation. Ion beam irradiation does not have such a drawback, on the contrary, it

G. N. Kropachev; R. P. Kuibeda; A. I. Semennikov; A. A. Aleev; A. D. Fertman; T. V. Kulevoy

243

Oxide shell reduction and magnetic property changes in core-shell Fe nanoclusters under ion irradiation  

NASA Astrophysics Data System (ADS)

Ion irradiation effects are studied on the Fe-based core-shell nanocluster (NC) films with core as Fe and shell as Fe3O4/Fe3N. These NC films were deposited on Si substrates to thickness of ˜0.5 ?m using a NC deposition system. The films were irradiated at room temperature with 5.5 MeV Si2+ ions to ion fluences of 1015 and 1016 ions/cm2. It is found that the irradiation induces grain growth, Fe valence reduction in the shell, and crystallization or growth of Fe3N. The film retained its Fe-core and its ferromagnetic properties after irradiation. The nature and mechanism of oxide shell reduction and composition dependence after irradiation were studied by synthesizing additional NC films of Fe3O4 and FeO + Fe3N and irradiating them under the same conditions. The presence of nanocrystalline Fe is found to be a major factor for the oxide shell reduction. The surface morphologies of these films show dramatic changes in the microstructures due to cluster growth and agglomeration as a result of ion irradiation.

Sundararajan, Jennifer A.; Kaur, Maninder; Jiang, Weilin; McCloy, John S.; Qiang, You

2014-05-01

244

A model to evaluate the nano-indentation hardness of ion-irradiated materials  

NASA Astrophysics Data System (ADS)

Nanoindentation is essential to study on mechanical properties of ion-irradiated materials at nanoscale. The measured nanoindentation hardness needs to be converted to the bulk-equivalent hardness by using some computation models. We proposed a modified model based on the popular Nix-Gao model and Korsunsky film/substrate model for the evaluation of the composite hardness of the ion-irradiated materials as well as other material constants that characterize the performance of material during the indentation test. It is developed from two important considerations: (1) Ion-irradiated materials are simply treated as a film/substrate systems consisting of irradiated-hardening layer and the substrate. (2) The substrate starts to contribute to the composite hardness at the relative indentation depth (t) which is less than the films thickness (t0). The fitting results reveal that the modified model describes very well the hardness data obtained from different ion-irradiation systems such as helium and hydrogen ion irradiation. The proposed model not only shows the hardness of irradiated-hardening layer and substrate, but also allows quantitative understanding on the indentation size effect.

Liu, P. P.; Wan, F. R.; Zhan, Q.

2015-01-01

245

Oxide shell reduction and magnetic property changes in core-shell Fe nanoclusters under ion irradiation  

SciTech Connect

Ion irradiation effects are studied on the Fe-based core-shell nanocluster (NC) films with core as Fe and shell as Fe{sub 3}O{sub 4}/Fe{sub 3}N. These NC films were deposited on Si substrates to thickness of ?0.5 ?m using a NC deposition system. The films were irradiated at room temperature with 5.5?MeV Si{sup 2+} ions to ion fluences of 10{sup 15} and 10{sup 16} ions/cm{sup 2}. It is found that the irradiation induces grain growth, Fe valence reduction in the shell, and crystallization or growth of Fe{sub 3}N. The film retained its Fe-core and its ferromagnetic properties after irradiation. The nature and mechanism of oxide shell reduction and composition dependence after irradiation were studied by synthesizing additional NC films of Fe{sub 3}O{sub 4} and FeO?+?Fe{sub 3}N and irradiating them under the same conditions. The presence of nanocrystalline Fe is found to be a major factor for the oxide shell reduction. The surface morphologies of these films show dramatic changes in the microstructures due to cluster growth and agglomeration as a result of ion irradiation.

Sundararajan, Jennifer A.; Kaur, Maninder; Qiang, You, E-mail: youqiang@uidaho.edu [Department of Physics, University of Idaho, Moscow, Idaho 83844 (United States); Jiang, Weilin [Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352 (United States); McCloy, John S. [School of Mechanical and Materials Engineering, Washington State University, Pullman, Washington 99164 (United States)

2014-05-07

246

Effects of O 7+ swift heavy ion irradiation on indium oxide thin films  

NASA Astrophysics Data System (ADS)

Indium oxide thin films deposited by spray pyrolysis were irradiated by 100 MeV O 7+ ions with different fluences of 5 × 10 11, 1 × 10 12 and 1 × 10 13 ions/cm 2. X-ray diffraction analysis confirmed the structure of indium oxide with cubic bixbyite. The strongest (2 2 2) orientation observed from the as-deposited films was shifted to (4 0 0) after irradiation. Furthermore, the intensity of the (4 0 0) orientation was decreased with increasing fluence together with an increase in (2 2 2) intensity. Films irradiated with maximum fluence exhibited an amorphous component. The mobility of the as-deposited indium oxide films was decreased from ˜78.9 to 43.0 cm 2/V s, following irradiation. Films irradiated with a fluence of 5 × 10 11 ions/cm 2 showed a better combination of electrical properties, with a resistivity of 4.57 × 10 -3 ? cm, carrier concentration of 2.2 × 10 19 cm -3 and mobility of 61.0 cm 2/V s. The average transmittance obtained from the as-deposited films decreased from ˜81% to 72%, when irradiated with a fluence of 5 × 10 11 ions/cm 2. The surface microstructures confirmed that the irregularly shaped grains seen on the surface of the as-deposited films is modified as "radish-like" morphology when irradiated with a fluence of 5 × 10 11 ions/cm 2.

Gokulakrishnan, V.; Parthiban, S.; Elangovan, E.; Ramamurthi, K.; Jeganathan, K.; Kanjilal, D.; Asokan, K.; Martins, R.; Fortunato, E.

2011-08-01

247

Positron annihilation Doppler broadening spectroscopy study on Fe-ion irradiated NHS steel  

NASA Astrophysics Data System (ADS)

In order to study the evolution of irradiation-induced vacancy-type defects at different irradiation fluences and temperatures, a new type of ferritic/martensitic (F/M) steel named NHS (Novel High Silicon) was irradiated by 3.25 MeV Fe-ion at room temperature and 723 K to fluences of 4.3 × 1015 and 1.7 × 1016 ions/cm2. After irradiation, vacancy-type defects were investigated with variable-energy positron beam Doppler broadening spectra. Energetic Fe-ions produced a large number of vacancy-type defects in the NHS steel, but one single main type of vacancy-type defect was observed in both unirradiated and irradiated samples. The concentration of vacancy-type defects decreased with increasing temperature. With the increase of irradiation fluence, the concentration of vacancy-type defects increased in the sample irradiated at RT, whereas for the sample irradiated at 723 K, it decreased. The enhanced recombination between vacancies and excess interstitial Fe atoms from deeper layers, and high diffusion rate of self-interstitial atoms further improved by diffusion via grain boundary and dislocations at high temperature, are thought to be the main reasons for the reversed trend of vacancy-type defects between the samples irradiated at RT and 723 K.

Zhu, Huiping; Wang, Zhiguang; Gao, Xing; Cui, Minghuan; Li, Bingsheng; Sun, Jianrong; Yao, Cunfeng; Wei, Kongfang; Shen, Tielong; Pang, Lilong; Zhu, Yabin; Li, Yuanfei; Wang, Ji; Song, Peng; Zhang, Peng; Cao, Xingzhong

2015-02-01

248

Fabrication and characterization of APT specimens from high dose heavy ion irradiated materials.  

PubMed

The next generations of advanced energy systems will require materials that can withstand high doses of irradiation at elevated temperatures. Therefore, a methodology has been developed for the fabrication of high-dose ion-irradiated atom probe tomography specimens at a specific dose with the use of a focused ion beam milling system. The method also enables the precise ion dose of the atom probe tomography specimen to be estimated from the local concentration of the implanted ions. The method has been successfully applied to the characterization of the distribution of nanoclusters in a radiation-tolerant 14YWT nanostructured ferritic steel under ion irradiation to doses up to 400 displacements per atom. PMID:21277681

Miller, M K; Zhang, Y

2011-05-01

249

Modulation of structure, morphology and wettability of polytetrafluoroethylene surface by low energy ion beam irradiation  

NASA Astrophysics Data System (ADS)

Polytetrafluoroethylene (PTFE) films were irradiated under vacuum with 3 keV Argon ions (Ar+) and fluences ranging from 0.5 × 1018 to 2 × 1018 ions/cm2. Ion induced PTFE surface modifications of structural, morphological and wettability nature were studied by means of Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy, atomic force microscopy and force spectroscopy, and contact angle measurements. FTIR analysis indicated defluorination of PTFE due to the rupture of C-C and C-F bonds. The values of droplet contact angle of the irradiated samples decreased gradually with the increasing ion flux, and were found to be very sensitive to the environmental humidity under which the measurements were made. The experimental results show that the surface chemical bond, morphology, and wettability of irradiated PTFE samples depend closely on the argon ion flux.

Atta, Ali; Fawzy, Yasser H. A.; Bek, Alpan; Abdel-Hamid, Hassan M.; El-Oker, Mohamed M.

2013-04-01

250

KeV-MeV ion irradiation of polyvinylidene fluoride (PVDF) films  

NASA Astrophysics Data System (ADS)

Semicrystalline polyvinylidene fluoride (PVDF) films have been irradited with different ion beams and energies ranging between 0.1 keV/amu and 6 MeV/amu. Polymer modifications induced by the ion irradiation, for electronic and nuclear energy stopping, have been investigated in situ by a highly sensitive quadrupole mass spectrometer. Ion irradiation of PVDF produced ejection of H 2 and HF molecules with a high chemical yield. Switching on the ion beam, the measured yields show a prompt (for H 2) and a slow (for HF) component of the molecular emission, which depends on the ion energy, ion fluence and polymer temperature. Along the ion track, the energy deposition produces a high density of active species, which give rise to desorbed molecules, to cross-linking processes and to a very stable residual carboneous film. At room temperature, the diffusion coefficient of HF molecules measured in irradiated PVDF is of the order of 10 -8 cm 2/s. The structural modifications of the irradiated films have been investigated ex situ by X-ray diffraction and optical absorption. The ion energy deposition along the ion track can be useful to realize active bio-membranes through the polymer grafting process.

Torrisi, L.; Ciavola, G.; Percolla, R.; Benyaich, F.

1996-08-01

251

Sound wave generated by swift heavy ions  

NASA Astrophysics Data System (ADS)

We irradiated samples of polycrystalline metals (Al and Cu) and ceramics (MgO and machinable ceramic) with a short-pulse beam of 3.54-GeV Xe ions and detected sound waves in ultrasonic frequencies with piezoelectric sensors on the surface. On the Al sample, waveforms were observed at different positions relative to the epicenter and were compared with those by 3.8-GeV Ar ion and YAG-laser irradiation. The gross structure of the waveform was similar between the Xe and laser irradiation, where we observed a shear wave which was not found in the Ar-beam irradiation. For the metal samples, the propagation time of the compression wave to the epicenter is shorter for the Xe ion than the laser irradiation. Using the time difference and separately-measured value of speed of sound, we estimated the depth of the sound source in metals and found that it is near the end of the ion range.

Kambara, Tadashi

2006-04-01

252

Effects of ion irradiation on supported carbon nanotubes and nanotube-substrate A. V. Krasheninnikov, K. Nordlund, and J. Keinonen  

E-print Network

Effects of ion irradiation on supported carbon nanotubes and nanotube-substrate interfaces A. V of Helsinki, Finland ABSTRACT We employ molecular dynamics to study the effects of ion irradiation on carbon by forming nanotube-substrate bonds which appear near irradiation-induced defects. INTRODUCTION Recent

Krasheninnikov, Arkady V.

253

Ion-irradiation-induced defects in bundles of carbon nanotubes E. Salonen *, A.V. Krasheninnikov, K. Nordlund  

E-print Network

Ion-irradiation-induced defects in bundles of carbon nanotubes E. Salonen *, A.V. Krasheninnikov, K irradiation in bundles of single-wall carbon nanotubes. For this, we employ empirical potential molecular to be highly non-uniform. We also show that ion irradiation gives rise to the formations of inter-tube covalent

Krasheninnikov, Arkady V.

254

Enhancement of band gap and photoconductivity in gamma indium selenide due to swift heavy ion irradiation  

SciTech Connect

{gamma}-In{sub 2}Se{sub 3} thin films prepared at different annealing temperatures ranging from 100 to 400 deg. C were irradiated using 90 MeV Si ions with a fluence of 2x10{sup 13} ions/cm{sup 2}. X-ray diffraction analysis proved that there is no considerable variation in structural properties of the films due to the swift heavy ion irradiation. However, photosensitivity and sheet resistance of the samples increased due to irradiation. It was observed that the sample, which had negative photoconductivity, exhibited positive photoconductivity, after irradiation. The negative photoconductivity was due to the combined effect of trapping of photoexcited electrons, at traps 1.42 and 1.26 eV, above the valence band along with destruction of the minority carriers, created during illumination, through recombination. Photoluminescence study revealed that the emission was due to the transition to a recombination center, which was 180 meV above the valence band. Optical absorption study proved that the defects present at 1.42 and 1.26 eV were annealed out by the ion beam irradiation. This allowed photoexcited carriers to reach conduction band, which resulted in positive photoconductivity. Optical absorption study also revealed that the band gap of the material could be increased by ion beam irradiation. The sample prepared at 400 deg. C had a band gap of 2 eV and this increased to 2.8 eV, after irradiation. The increase in optical band gap was attributed to the annihilation of localized defect bands, near the conduction and valence band edges, on irradiation. Thus, by ion beam irradiation, one could enhance photosensitivity as well as the optical band gap of {gamma}-In{sub 2}Se{sub 3}, making the material suitable for applications such as window layer in solar cells.

Sreekumar, R.; Jayakrishnan, R.; Sudha Kartha, C.; Vijayakumar, K. P.; Khan, S. A.; Avasthi, D. K. [Department of Physics, Cochin University of Science and Technology, Cochin 682022 (India); Material Science Division, Inter University Accelerator Centre, New Delhi 110 067 (India)

2008-01-15

255

Kr-86 Ion-Beam Irradiation of Hydrated DNA: Free Radical and Unaltered Base Yields  

PubMed Central

This work reports an ESR and product analysis investigation of Kr-86 ion-beam irradiation of hydrated DNA at 77 K. The irradiation results in the formation and trapping of both base radicals and sugar phosphate radicals (DNA backbone radicals). The absolute yields (G, ?mol/J) of the base radicals are smaller than the yields found in similarly prepared ?-irradiated DNA samples, and the relative yields of backbone radicals relative to base radicals are much higher than that found in ?-irradiated samples. From these results, we have elaborated our radiation chemical model of the track structure for ion-beam irradiated DNA as it applies to krypton ion-beams. The base radicals, which are trapped as ion radicals or reversibly protonated or deprotonated ion radicals, are formed almost entirely in the track penumbra, a region in which radiation chemical effects are similar to those found in ?-irradiated samples. By comparing the yields of base radicals in ion-beam samples to the yields of the same radicals in ?-irradiated samples, the partition of energy between the low-LET region (penumbra) and the core is experimentally determined. The neutral sugar and other backbone radicals, which are not as susceptible to recombination as are ion radicals, are formed largely in the track core. The backbone radicals show a linear dose response up to very high doses. Unaltered base release yields in Kr-86 irradiated hydrated DNA are equal to sugar radical yields within experimental error limits, consistent with radiation-chemical processes in which all base release originates with sugar radicals. Two phosphorus-centered radicals from fragmentation of the DNA backbone are found in low yields. PMID:23106211

Becker, David; Adhikary, Amitava; Tetteh, Smedley T.; Bull, Arthur W.; Sevilla, Michael D.

2012-01-01

256

Hydrogen transport through oxide metal surface under atom and ion irradiation  

NASA Astrophysics Data System (ADS)

Both the latest and earlier achieved results on gas exchange processes on metal surfaces (including stainless steel, titanium, zirconium, tungsten with deposited aluminum oxide coating) under hydrogen atom or plasma irradiation with occasional oxygen impurity are presented in the paper. Mechanisms and regularities of these processes are discussed. It is demonstrated that surface oxide layer properties as a diffusion barrier strongly depend on external influence on the surface. In particular, it is revealed that low energy hydrogen ion irradiation could slow down hydrogen desorption from metals. Hydrogen atom or ion irradiation combined with simultaneous oxygen admixture accelerates hydrogen desorption from metals.

Begrambekov, L.; Dvoychenkova, O.; Evsin, A.; Kaplevsky, A.; Sadovskiy, Ya; Schitov, N.; Vergasov, S.; Yurkov, D.

2014-11-01

257

Modifying the morphology and magnetic properties of magnetite nanoparticles using swift heavy ion irradiation  

NASA Astrophysics Data System (ADS)

Magnetite (Fe3O4) nanospheres of ˜8-11 nm diameter synthesized using a chemical co-precipitation method were deposited as thin films on different substrates using spin coating. The thin films were irradiated with Ag ions at 100 MeV energy. Comparison of unirradiated, as synthesized Fe3O4 nanoparticulate thin film and ion irradiated film shows that irradiation causes dramatic changes in the morphology, structure and magnetic properties. Monte Carlo simulations carried out on this system indicate that the origin of the changes in the magnetic properties lies in the enhanced magnetic anisotropy energy density and reorientation of magnetic easy axis.

Gokhale, Shubha; Lamba, Subhalakshmi; Kumari, Neha; Singh, Bhupendra; Avasthi, D. K.; Kulkarni, S. K.

2014-08-01

258

Irradiation effects of swift heavy ions in actinide oxides and actinide nitrides: Structure and optical properties  

NASA Astrophysics Data System (ADS)

Actinide oxides have been used as nuclear fuels in the majority of power reactors working in the world and actinide nitrides are under investigation for the fuels of the future fast neutron fission reactors developed in Forum Generation IV. Radiation damage in actinide oxides UO 2, (U 0.92Ce 0.08)O 2, and actinide nitride UN has been characterized after irradiation with swift heavy ions. Fluences up to 3 × 10 13 ions/cm 2 of heavy ions (Kr 740 Mev, Cd 1 GeV) available at the CIRIL/GANIL facility were used to simulate irradiation in reactors by fission products and by neutrons. The macroscopic effects of irradiation remains very weak compared with those seen in other ceramic oxides irradiated in the same conditions: practically no swelling can be measured and no change in colour can be observed on the irradiated part of a polished face of sintered disks. The point defects in irradiated actinide compounds have been characterized by optical absorption spectroscopy in the UV-Vis-NIR wavelength range. The absorption spectra before and after irradiation are compared, and unexpected stability of optical properties during irradiation is shown. This result confirms the low rate of formation of point defects in actinide oxides and actinide nitrides under irradiation. Actinide oxides and nitrides studied are >40% ionic, and oxidation state of the actinides seems to be stable during irradiation. The small amount of point defects produced by radiation (<10 16 cm -2) has been identified from differences between the absorption spectrum before irradiation and the one after irradiation: point defects in oxygen or nitrogen lattices can be observed respectively in oxides and nitrides (F centres), and small amounts of U 5+ would be present in all compounds.

Beauvy, Michel; Dalmasso, Chrystelle; Iacconi, Philibert

2006-09-01

259

Sound wave generated by swift heavy ions  

Microsoft Academic Search

We irradiated samples of polycrystalline metals (Al and Cu) and ceramics (MgO and machinable ceramic) with a short-pulse beam of 3.54-GeV Xe ions and detected sound waves in ultrasonic frequencies with piezoelectric sensors on the surface. On the Al sample, waveforms were observed at different positions relative to the epicenter and were compared with those by 3.8-GeV Ar ion and

Tadashi Kambara

2006-01-01

260

Heavy Ion Irradiation Inhibits in Vitro Angiogenesis Even at Sublethal Dose1  

Microsoft Academic Search

Angiogenesis is essential for tumor growth and metastasis. Because endothelial cells are genetically stable, they rarely acquire resistance to anticancer modalities, and could, thus, be a suitable target for radiation therapy. Heavy ion radiation therapy has attracted attention as an effec- tive modality for cancer therapy because of its highly lethal effects, but the effects of heavy ion irradiation on

Yutaka Takahashi; Teruki Teshima; Naomasa Kawaguchi; Yoshinosuke Hamad; Seiji Mori; Ayako Madachi; Satoko Ikeda; Hirokazu Mizuno; Toshiyuki Ogata; Kumie Nojima; Yoshiya Furusawa; Nariaki Matsuura

2003-01-01

261

Observation of DNA damage of human hepatoma cells irradiated by heavy ions using comet assay  

Microsoft Academic Search

AIM: Now many countries have developed cancer therapy with heavy ions, especially in GSI (Gesellschaft für Schwerionenforschung mbH, Darmstadt, Germany), remarkable results have obtained, but due to the complexity of particle track structure, the basic theory still needs further researching. In this paper, the genotoxic effects of heavy ions irradiation on SMMC-7721 cells were measured using the single cell gel

Li-Mei Qiu; Wen-Jian Li; Xin-Yue Pang; Qing-Xiang Gao; Yan Feng; Li-Bin Zhou; Gao-Hua Zhang

2003-01-01

262

Oxide Shell Reduction and Magnetic Property Changes in Core-Shell Fe Nanoclusters under Ion Irradiation  

SciTech Connect

Ion irradiation effects are studied on the Fe-based core-shell nanocluster (NC) films with core as Fe and shell as Fe3O4/FeO. These NC films were were deposited on Si substrates to thickness of ~0.5 micrometers using a NC deposition system. The films were irradiated at room temperature with 5.5 MeV Si2+ ions to ion fluences of 1015 and 1016 ions/cm2. It is found that the irradiation induces grain growth, Fe valence reduction in the shell, and crystallization of Fe3N. The nature and mechanism of oxide shell reduction and composition dependence after irradiation were studied by synthesizing additional NC films of Fe3O4 and FeO+Fe3N and irradiating them under the same conditions. The presence of nanocrystalline Fe is found to be a major factor for the oxide shell reduction. The surface morphologies of these films show dramatic changes in the microstructures due to cluster growth and agglomeration as a result of ion irradiation.

Sundararajan, Jennifer A.; Kaur, Maninder; Jiang, Weilin; McCloy, John S.; Qiang, You

2014-02-12

263

Influence of irradiation spectrum and implanted ions on the amorphization of ceramics  

SciTech Connect

Polycrystalline Al2O3, magnesium aluminate spinel (MgAl2O4), MgO, Si3N4, and SiC were irradiated with various ions at 200-450 K, and microstructures were examined following irradiation using cross-section TEM. Amorphization was not observed in any of the irradiated oxide ceramics, despsite damage energy densities up to {similar_to}7 keV/atom (70 displacements per atom). On the other hand, SiC readily amorphized after damage levels of {similar_to}0.4 dpa at room temperature (RT). Si3N4 exhibited intermediate behavior; irradiation with Fe{sup 2+} ions at RT produced amorphization in the implanted ion region after damage levels of {similar_to}1 dpa. However, irradiated regions outside the implanted ion region did not amorphize even after damage levels > 5 dpa. The amorphous layer in the Fe-implanted region of Si3N4 did not appear if the specimen was simultaneoulsy irradiated with 1-MeV He{sup +} ions at RT. By comparison with published results, it is concluded that the implantation of certain chemical species has a pronounced effect on the amorphization threshold dose of all five materials. Intense ionizing radiation inhibits amorphization in Si3N4, but does not appear to significantly influence the amorphization of SiC.

Zinkle, S.J.; Snead, L.L.

1995-12-31

264

Ion microbeam irradiation for radiobiology and radical chemistry: status and prospect  

NASA Astrophysics Data System (ADS)

Ion microbeams are commonly used to study local irradiation effects in living cells, as it has been established that ion beam irradiations can lead to deleterious changes in cells that are not struck directly by the microbeam. Such changes, which take place over distances long compared to the size of the irradiation spot and for times long compared to the time of irradiation, are collectively termed radiation-induced bystander effect or RIBE. Free-radical chemistry is frequently invoked to explain the RIBE but no unified model is available at present. Ion microbeams when coupled with advanced methods for observing free radicals are the tools of choice for investigating the chemistry and biological processes governing RIBE.

Khodja, H.

2011-01-01

265

Evaluation of cell behavior on modified polypropylene with swift heavy ion irradiation  

NASA Astrophysics Data System (ADS)

Ion beam irradiation is a well known means to change the physico-chemical properties of polymers, and induced bio and citocompatibility in controlled conditions and in selected areas of surface. However, the enhancement of cell adhesion on a modified substrate does not mean that the surface is adequate for functional cells. The purpose of the present work is to study proliferation, changes in cytoskeleton and cell morphology on substrates as a function of irradiation parameters. We irradiated polypropylene with sulfur (S) ion-beam at energies of 110 MeV with fluences between 1 × 10 6 and 2 × 10 10 ions cm -2. NIH 3T3 cells were cultured on each sample. Cell morphology was observed using phase contrast microscopy and cytoskeleton proteins with fluorescence microscopy. The analysis show different cellular responses as a functions of irradiation parameter, strongly suggests that different underlying substratum can result in distinct types of cytoskeleton reorganization.

Arbeitman, Claudia R.; Ibañez, Irene L.; García Bermúdez, Gerardo; Durán, Hebe; del Grosso, Mariela F.; Salguero, Noelia; Mazzei, Rubén

2012-02-01

266

Damage and Microstructure Evolution in GaN under Au Ion Irradiation  

SciTech Connect

Damage and microstructure evolution in gallium nitride (GaN) under Au+ ion irradiation has been investigated using complementary electron microscopy, secondary ion mass spectrometry and ion beam analysis techniques. Epitaxially-grown GaN layers (2-um-thick) have been irradiated by 2.0 MeV Au ions to 1.0 × 1015 and 1.4 × 1015 cm-2 at 155 K and 7.3 × 1015 cm-2 at 200 K. The irradiation-induced damage has been analyzed by Rutherford backscattering spectroscopy in a channeling direction (RBS/C). For a better determination of ion-induced disorder profile, an iterative procedure and a Monte Carlo code (McChasy) are combined to analyze the ion channeling spectra. With increasing irradiation dose, separated amorphous layers develop from the sample surface and near the damage peak region. Formation of large nitrogen bubbles with sizes up to 70 nm is observed in the buried amorphous layer, while the surface layer contains small bubbles with diameter of a few nanometers due to significant nitrogen loss from the surface. Volume expansion from 3% to 25% in the irradiated region is suggested by cross sectional transmission electron microscope and RBS/C measurement. The anomalous shape of the Au distributions under three irradiations indicates out-diffusion of Au toward sample surface. The results from the complementary techniques suggest that nitrogen is retained in the damaged GaN where the crystallinity is preserved. Once the amorphous state is reached in the surface region, GaN starts to decompose and nitrogen escapes from the surface. Furthermore, experimental results show considerable errors in both disorder profile and ion range predicted by the Stopping and Range of Ions in Matter code, indicating a significant overestimation of electronic stopping powers of Au ions in GaN.

Zhang, Yanwen; Ishimaru, Manabu; Jagielski, Jacek; Zhang, Weiming; Zhu, Zihua; Saraf, Laxmikant V.; Jiang, Weilin; Thome, Lionel; Weber, William J.

2010-02-11

267

Design study of a raster scanning system for moving target irradiation in heavy-ion radiotherapy  

SciTech Connect

A project to construct a new treatment facility as an extension of the existing heavy-ion medical accelerator in chiba (HIMAC) facility has been initiated for further development of carbon-ion therapy. The greatest challenge of this project is to realize treatment of a moving target by scanning irradiation. For this purpose, we decided to combine the rescanning technique and the gated irradiation method. To determine how to avoid hot and/or cold spots by the relatively large number of rescannings within an acceptable irradiation time, we have studied the scanning strategy, scanning magnets and their control, and beam intensity dynamic control. We have designed a raster scanning system and carried out a simulation of irradiating moving targets. The result shows the possibility of practical realization of moving target irradiation with pencil beam scanning. We describe the present status of our design study of the raster scanning system for the HIMAC new treatment facility.

Furukawa, Takuji; Inaniwa, Taku; Sato, Shinji; Tomitani, Takehiro; Minohara, Shinichi; Noda, Koji; Kanai, Tatsuaki [Medical Physics Research Group, Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555 (Japan)

2007-03-15

268

Enhancement of impact-induced mechanoluminescence by swift heavy ion irradiation  

SciTech Connect

In this Letter, we report a strategy using swift heavy ion (SHI) irradiation to enhance the impact-induced mechanoluminescence (ML) in ML materials. The impact-induced ML intensity of CaSrAl{sub 2}Si{sub 2}O{sub 8}:Eu{sup 2+} was enhanced by about one order of magnitude by using SHI irradiation. Furthermore, the enhancement was found to depend on electronic stopping power and irradiation fluence. The density of traps of a type suitable for impact-induced ML is considered to be increased by the SHI irradiation, resulting in the impact-induced ML enhancement.

Zhan, T. Z.; Terasawa, Y. [Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, 6-1 Kasugakoen, Kasuga, Fukuoka 816-8580 (Japan); Xu, C. N. [Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, 6-1 Kasugakoen, Kasuga, Fukuoka 816-8580 (Japan); National Institute of Advanced Industrial Science and Technology, Kyushu, 807-1 Shuku, Tosu, Saga 841-0052 (Japan); CREST, Japan Science and Technology Agency, 4 Honcho, Kawaguchi, Saitama 332-0012 (Japan); Yamada, H. [Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, 6-1 Kasugakoen, Kasuga, Fukuoka 816-8580 (Japan); National Institute of Advanced Industrial Science and Technology, Kyushu, 807-1 Shuku, Tosu, Saga 841-0052 (Japan); Zhang, L. [National Institute of Advanced Industrial Science and Technology, Kyushu, 807-1 Shuku, Tosu, Saga 841-0052 (Japan); Iwase, H.; Kawai, M. [High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan)

2012-01-02

269

Interfacial carbon nanoplatelet formation by ion irradiation of graphene on iridium(111).  

PubMed

We expose epitaxial graphene (Gr) on Ir(111) to low-energy noble gas ion irradiation and investigate by scanning tunneling microscopy and atomistic simulations the behavior of C atoms detached from Gr due to ion impacts. Consistent with our density functional theory calculations, upon annealing Gr nanoplatelets nucleate at the Gr/Ir(111) interface from trapped C atoms initially displaced with momentum toward the substrate. Making use of the nanoplatelet formation phenomenon, we measure the trapping yield as a function of ion energy and species and compare the values to those obtained using molecular dynamics simulations. Thereby, complementary to the sputtering yield, the trapping yield is established as a quantity characterizing the response of supported 2D materials to ion exposure. Our findings shed light on the microscopic mechanisms of defect production in supported 2D materials under ion irradiation and pave the way toward precise control of such systems by ion beam engineering. PMID:25486329

Herbig, Charlotte; Åhlgren, E Harriet; Jolie, Wouter; Busse, Carsten; Kotakoski, Jani; Krasheninnikov, Arkady V; Michely, Thomas

2014-12-23

270

Resonant Raman scattering investigation of ion-irradiated hydrogenated amorphous carbon  

NASA Astrophysics Data System (ADS)

The effect of hydrogen removal by ion irradiation on the first- and second-order resonant Raman scattering of a-C:H are reported. We have measured the absolute first-order Raman intensity versus ion-irradiation dose and found a monotonic decrease in the absolute intensity with increasing ion dose. In addition, second-order Raman scattering also exhibited some resonance enhancement. The consequences of these results are discussed, particularly the important role of hydrogen in determining the vibrational properties of a-C:H films.

Sela, I.; Adel, M.; Beserman, R.

1990-07-01

271

Ion irradiation effects on ionic liquids interfaced with rf discharge plasmas  

NASA Astrophysics Data System (ADS)

The availability of plasma ion irradiation toward a gas-liquid interface is investigated in a rf discharge system incorporating an ionic liquid. The introduction of the ionic liquid to the plasma causes the formation of a sheath electric field on the ionic liquid surface, resulting in the acceleration of the ions to the ionic liquid and the generation of secondary electrons from the ionic liquid by the ion irradiation. These effects are found to advance the discharge process and enhance the plasma production.

Baba, K.; Kaneko, T.; Hatakeyama, R.

2007-05-01

272

Strain-dependent Damage in Mouse Lung After Carbon Ion Irradiation  

SciTech Connect

Purpose: To examine whether inherent factors produce differences in lung morbidity in response to carbon ion (C-ion) irradiation, and to identify the molecules that have a key role in strain-dependent adverse effects in the lung. Methods and Materials: Three strains of female mice (C3H/He Slc, C57BL/6J Jms Slc, and A/J Jms Slc) were locally irradiated in the thorax with either C-ion beams (290 MeV/n, in 6 cm spread-out Bragg peak) or with {sup 137}Cs {gamma}-rays as a reference beam. We performed survival assays and histologic examination of the lung with hematoxylin-eosin and Masson's trichrome staining. In addition, we performed immunohistochemical staining for hyaluronic acid (HA), CD44, and Mac3 and assayed for gene expression. Results: The survival data in mice showed a between-strain variance after C-ion irradiation with 10 Gy. The median survival time of C3H/He was significantly shortened after C-ion irradiation at the higher dose of 12.5 Gy. Histologic examination revealed early-phase hemorrhagic pneumonitis in C3H/He and late-phase focal fibrotic lesions in C57BL/6J after C-ion irradiation with 10 Gy. Pleural effusion was apparent in C57BL/6J and A/J mice, 168 days after C-ion irradiation with 10 Gy. Microarray analysis of irradiated lung tissue in the three mouse strains identified differential expression changes in growth differentiation factor 15 (Gdf15), which regulates macrophage function, and hyaluronan synthase 1 (Has1), which plays a role in HA metabolism. Immunohistochemistry showed that the number of CD44-positive cells, a surrogate marker for HA accumulation, and Mac3-positive cells, a marker for macrophage infiltration in irradiated lung, varied significantly among the three mouse strains during the early phase. Conclusions: This study demonstrated a strain-dependent differential response in mice to C-ion thoracic irradiation. Our findings identified candidate molecules that could be implicated in the between-strain variance to early hemorrhagic pneumonitis after C-ion irradiation.

Moritake, Takashi [Advanced Radiation Biology Research Program, Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, Chiba (Japan) [Advanced Radiation Biology Research Program, Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, Chiba (Japan); Proton Medical Research Center, University of Tsukuba, Tsukuba (Japan); Fujita, Hidetoshi; Yanagisawa, Mitsuru; Nakawatari, Miyako; Imadome, Kaori; Nakamura, Etsuko; Iwakawa, Mayumi [Advanced Radiation Biology Research Program, Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, Chiba (Japan)] [Advanced Radiation Biology Research Program, Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, Chiba (Japan); Imai, Takashi, E-mail: imait@nirs.go.jp [Advanced Radiation Biology Research Program, Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, Chiba (Japan)] [Advanced Radiation Biology Research Program, Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, Chiba (Japan)

2012-09-01

273

Three-stage structural modification of carbon nanotubes by swift heavy ion irradiation  

NASA Astrophysics Data System (ADS)

A study on the structural evolution of carbon nanotubes (CNTs) under irradiation by swift heavy ions (SHIs) of widely varying electronic energy loss (Se) values is presented. The control over Se is exercised through the choice of ion species used for irradiation. The ion beams used are those of nickel and gold with energies 60 and 120 MeV, respectively. Structural changes in CNTs were investigated qualitatively using Raman spectroscopy. Results of irradiation indicate that the structural modifications of CNTs can be broadly divided in three stages. At very low fluences the process of healing occurs; at intermediate fluences damage to the surface of CNTs predominates and nano-graphitic formations are seen; at very high fluences, of the order of 1 × 1014 ions/cm2, the system becomes amorphous. The stable nature of single walled carbon nanotubes compared to multiwalled carbon nanotubes, is also established from the Raman spectroscopy results.

Jeet, Kiran; Jindal, V. K.; Bharadwaj, L. M.; Bhandari, Rajiv; Dharamvir, Keya

2012-08-01

274

Pattern-induced magnetic anisotropy in FePt thin films by ion irradiation  

SciTech Connect

The magnetic properties of FePt thin films have been modified by exposing the samples to irradiation of 4 MeV Cl{sup 2+} ions. Patterned magnetic films, without modified topographical profile, were fabricated by irradiating the films through a shadowing micrometric mask. The structural changes, ascribed to the ion-beam-induced amorphization of the thin films, promote the modification of the magnetic anisotropy. In particular, the out-of-plane component of the magnetization decreases simultaneously with an enhancement of in-plane anisotropy by increasing ion fluence. Moreover, the nonirradiated regions present unexpected anisotropic behavior owing to the stray field of the irradiated regions. The control of this effect, which can have unwished consequences for the patterning of magnetic properties by ion bombardment, needs to be suitably addressed.

Jaafar, M. [Instituto de Ciencia de Materiales de Madrid, CSIC, ES-28049 Madrid (Spain); Dpto. Fisica de la Materia Condensada, UAM, ES-28049 Madrid (Spain); Sanz, R. [Instituto de Ciencia de Materiales de Madrid, CSIC, ES-28049 Madrid (Spain); Nanoate SL, Poeta Rafael Morales 2, ES-28702 San Sebastian de los Reyes, Madrid (Spain); McCord, J. [Institute of Ion Beam Physics and Materials Research, FZD, D-01314 Dresden (Germany); Jensen, J. [Thin Film Physics, Department of Physics, Chemistry and Biology, Linkoeping University, SE-581 83 Linkoeping (Sweden); Schaefer, R. [Leibniz Institute for Solid State and Materials Research, IFW, Helmholtzstrasse 20, D-01069 Dresden (Germany); Vazquez, M.; Asenjo, A. [Instituto de Ciencia de Materiales de Madrid, CSIC, ES-28049 Madrid (Spain)

2011-03-01

275

Producing metastable nanophase with sharp interface by means of focused ion beam irradiation  

SciTech Connect

Amorphous carbon/nickel double layers were irradiated by 30 keV Ga{sup +} ions via focused ion beam. The effect of irradiation on the concentration distribution of all constituents was studied by Auger electron spectroscopy depth profiling and cross sectional transmission electron microscopy, while the morphology change of the sample was determined by atomic force microscopy. The Ga{sup +} ion irradiation results in the formation of metastable Ni{sub 3}C layer with a uniform thickness. The C/Ni{sub 3}C and Ni{sub 3}C/Ni interfaces were found to be sharp up to a fluence of 200 Ga{sup +} ions/nm{sup 2}.

Barna, Arpad; Kotis, Laszlo; Labar, Janos; Osvath, Zoltan; Toth, Attila L.; Menyhard, Miklos [Research Institute for Technical Physics and Materials Science, P.O. Box 49, Budapest H-1525 (Hungary); Zalar, Anton; Panjan, Peter [Jozef Stefan Institute, Jamova 39, 1000 Ljubljana (Slovenia)

2009-02-15

276

Etch-free formation of porous silicon by high-energy ion irradiation  

SciTech Connect

In this study, porous silicon was fabricated without any chemical etching by self-ion implantation of crystalline Si performed at high temperature and at high fluences. The irradiated silicon samples, which remained crystalline under high temperature ion irradiation, exhibited an increased porous fraction with increasing sample temperature at a given fluence, up to the maximum tested temperature of 650 C. Extremely high ion fluences of at least 2 1018 ions/cm2 were necessary to produce significant void growth. Comparisons between the porous silicon structures and irradiation-induced porous networks in Ge, GaSb, and InSb are made, and differences in the formation conditions for these porous networks are discussed.

Perez-Bergquist, Dr. Alejandro G. [Los Alamos National Laboratory (LANL); Naab, Fabian U. [University of Michigan; Zhang, Yanwen [ORNL; Wang, Prof. Lumin [University of Michigan

2011-01-01

277

Etch-free Formation of Porous Silicon by High-energy Ion Irradiation  

SciTech Connect

In this study, porous silicon was fabricated without any chemical etching by self-ion implantation of crystalline Si performed at high temperature and at high fluences. The irradiated silicon samples, which remained crystalline under high temperature ion irradiation, exhibited an increased porous fraction with increasing sample temperature at a given fluence, up to the maximum tested temperature of 650º C. Extremely high ion fluences of at least 2 x 10¹? ions/cm² were necessary to produce significant void growth. Comparisons between the porous silicon structures and irradiation-induced porous networks in Ge, GaSb, and InSb are made, and differences in the formation conditions for these porous networks are discussed.

Perez-Bergquist, Alejandro G.; Naab, Fabian U.; Zhang, Yanwen; Wang, Lumin M.

2011-03-15

278

1\\/f noise studies of swift heavy ion irradiated magnetite thin films  

Microsoft Academic Search

The effect of 190 MeV 107Ag ion irradiation on antiphase boundaries (APBs) of epitaxial Fe3O4 thin films (thickness ˜70 nm) grown on MgO (1 0 0) oriented substrate has been investigated. The X-ray diffraction shows that at low fluence values upto 5 × 1011 ions\\/cm2, the strain in the films is relaxed whereas at high fluence 1 × 1012 ions\\/cm2,

M. Wasi Khan; Ravi Kumar; J. P. Srivastava; S. K. Arora; R. J. Choudhary; I. V. Shvets

2008-01-01

279

New Ion Beam Materials Laboratory for Materials Modification and Irradiation Effects Research  

SciTech Connect

A new multifunctional ion beam materials laboratory (IBML) has been established at the University of Tennessee, in partnership with Oak Ridge National Laboratory. The IBML is currently equipped with two ion sources, a 3 MV tandem accelerator, three beamlines and three endstations. The IBML is primarily dedicated to fundamental research on ion-solid interaction, ion beam analysis, ion beam modification, and other basic and applied research on irradiation effects in a wide range of materials. An overview of the IBML facility is provided, and experimental results are reported to demonstrate the specific capabilities.

Zhang, Yanwen [ORNL; Crespillo, Miguel L [University of Tennessee (UT); Xue, Haizhou [University of Tennessee, Knoxville (UTK); Jin, Ke [University of Tennessee, Knoxville (UTK); Chen, Chien-Hung [University of Tennessee, Knoxville (UTK); Fontana, Cristiano L [ORNL; Graham, Dr. Joseph T. [The University of Tennessee; Weber, William J [ORNL

2014-01-01

280

New ion beam materials laboratory for materials modification and irradiation effects research  

NASA Astrophysics Data System (ADS)

A new multifunctional ion beam materials laboratory (IBML) has been established at the University of Tennessee, in partnership with Oak Ridge National Laboratory. The IBML is currently equipped with two ion sources, a 3 MV tandem accelerator, three beamlines and three endstations. The IBML is primarily dedicated to fundamental research on ion-solid interaction, ion beam analysis, ion beam modification, and other basic and applied research on irradiation effects in a wide range of materials. An overview of the IBML facility is provided, and experimental results are reported to demonstrate the specific capabilities.

Zhang, Y.; Crespillo, M. L.; Xue, H.; Jin, K.; Chen, C. H.; Fontana, C. L.; Graham, J. T.; Weber, W. J.

2014-11-01

281

MeV Au ion irradiation in silicon and nanocrystalline zirconia film deposited on silicon substrate  

NASA Astrophysics Data System (ADS)

Nanocrystalline zirconia (ZrO2) film with thickness of 305 nm deposited on a silicon substrate was irradiated with 2 MeV Au ions to different fluences at different temperatures. The implanted ion profiles were measured by time-of-flight secondary ion mass spectrometry (ToF-SIMS) and simulated using the stopping and range of ions in matter (SRIM) code, respectively. The experimental results show that a large fraction of the incident Au ions penetrates through the ZrO2 film and are deposited into the Si substrate. At the interface of ZrO2 and Si, a sudden decrease of Au concentration is observed due to the much larger scattering cross section of Au in ZrO2 than in Si. The depth profile of the Au ions is measured in both the ZrO2 films and the Si substrates, and the results show that the Au distribution profiles do not exhibit a dependence on irradiation temperature. The local Au concentration increases proportionally with the irradiation fluence, suggesting that no thermal or irradiation-induced redistribution of the implanted Au ions. However, the Au concentration in the ZrO2 films, as determined by SIMS, is considerably lower than that predicted by the SRIM results, and the penetration depth from the SIMS measurements is much deeper than that from the SRIM predictions. These observations can be explained by an overestimation of the electronic stopping power, used in the SRIM program, for heavy incident ions in light targets. Overestimation of the heavy-ion electronic stopping power may lead to errors in local dose calculation and underestimation of the projected range of slow heavy ions in targets that contain light elements. A quick estimate based on a reduced target density may be used to compensate the overestimation of the electronic stopping power in the SRIM program to provide better ion profile prediction.

Chang, Yongqin; Zhang, Yanwen; Zhu, Zihua; Edmondson, Philip D.; Weber, William J.

2012-09-01

282

Damages in ceramics for nuclear waste transmutation by irradiation with swift heavy ions  

NASA Astrophysics Data System (ADS)

Inert matrices are proposed for advanced nuclear fuels or for the transmutation of the actinides that is an effective solution for the nuclear waste management. The behaviour of inert matrix ceramics like MgO, MgAl 2O 4 and cubic ZrO 2 oxides under irradiation is presented in this study. The alumina Al 2O 3 has been also studied as a reference for the ceramic materials. These oxides have been irradiated with swift heavy ions at CIRIL/GANIL to simulate the fragment fission effects. The irradiations with the different heavy ions (from S to Pb) with energy between 91 and 820 MeV, have been realised at room temperature or 500 °C. The fluencies were between 5 × 10 10 and 5 × 10 15 ions/cm 2. The polished faces of sintered polycrystalline disks or single crystal slices have been characterized before and after irradiation by X-ray diffraction and optical spectroscopy. The apparent swelling evaluated from surface profile measurements after irradiation is very important for spinel and zirconia, comparatively with those of magnesia or alumina. The amorphisation seems to be at the origin of this swelling, and the electronic stopping power of the ions is the most influent parameter for the irradiation damages. The point defects characterized by optical spectroscopy show a significant amount of damage on the oxygen sub-lattice in the irradiated oxides. F + centres are present in all irradiated oxides. However, new absorption bands are observed and cation clusters cannot be excluded in magnesia and spinel after irradiation.

Beauvy, Michel; Dalmasso, Chrystelle; Thiriet-Dodane, Catherine; Simeone, David; Gosset, Dominique

2006-01-01

283

Morphological and biochemical responses of Oryza sativa L. (cultivar MR219) to ion beam irradiation*  

PubMed Central

Objective: Heavy ion beam, which has emerged as a new mutagen in the mutation breeding of crops and ornamental plants, is expected to result in the induction of novel mutations. This study investigates the morphological and biochemical responses of Oryza sativa toward different doses of carbon ion beam irradiation. Methods: In this study, the dry seeds of O. sativa were irradiated at 0, 20, 40, 60, 80, 100, and 120 Gy, followed by in-vitro germination under controlled conditions. Morphological and biochemical studies were conducted to investigate the morphological and physiological responses of O. sativa towards ion beam irradiation. Results: The study demonstrated that low doses (10 Gy) of ion beam have a stimulating effect on the height, root length, and fresh weight of the plantlets but not on the number of leaves. Meanwhile, doses higher than 10 Gy caused reductions in all the morphological parameters studied as compared to the control samples. The highest total soluble protein content [(2.11±0.47) mg/g FW] was observed in plantlets irradiated at 20 Gy. All irradiated plantlets were found to have 0.85% to 58.32% higher specific activity of peroxidase as compared to the control samples. The present study also revealed that low doses of ion beam (10 and 20 Gy) had negligible effect on the total chlorophyll content of O. sativa plantlets while 40 Gy had a stimulating effect on the chlorophyll content. Plantlets irradiated between 40 to 120 Gy were shown to be 0.38% to 9.98% higher in total soluble nitrogen content which, however, was not significantly different from the control samples. Conclusions: Carbon ion beam irradiation administered at low to moderate doses of 10 to 40 Gy may induce O. sativa mutants with superior characteristics. PMID:24302713

Ling, Anna Pick Kiong; Ung, Ying Chian; Hussein, Sobri; Harun, Abdul Rahim; Tanaka, Atsushi; Yoshihiro, Hase

2013-01-01

284

Microstructural and Mechanical Property Changes in Ion Irradiated Tunsgten  

E-print Network

on the sustainability of tungsten as a plasma facing material (PFM). During operation, PFM must withstand harsh conditions with combined effects from high temperature, mechanical stress, irradiation, transmutation, and the production of hydrogen (H) and helium (He...

General, Michael

2013-04-08

285

Effect of irradiation parameters on defect aggregation during thermal annealing of LiF irradiated with swift ions and electrons  

SciTech Connect

Absorption spectroscopy were performed to study the effects of thermal annealing on the aggregation of color centers in LiF crystals irradiated with different ions between carbon and uranium of megaelectron volt-gigaelectron volt energy. The beam parameters such as energy, energy loss, and fluence have a pronounced influence on the initial defect composition and concentration as well as their evolution upon thermal annealing. A distinct phenomenon was observed, viz., the enhancement of F{sub n} centers for annealing temperatures between 500 and 700 K, followed by Li colloid formation above 700 K. The phenomenon requires specific irradiation conditions whereas the formation of Mg colloids from Mg impurities occurs in all irradiated crystals. The mechanisms of annealing and colloid formation are discussed.

Schwartz, K.; Neumann, R.; Trautmann, C. [GSI Helmholtzzentrum fuer Schwerionenforschung, Planckstr. 1, 64291 Darmstadt (Germany); Volkov, A. E.; Sorokin, M. V. [Russian Research Center 'Kurchatov Institute', Kurchatov Square 1, 123182 Moscow (Russian Federation)

2010-10-01

286

Confinement Resonances in Photoionization of Xe-C{sub 60}{sup +}  

SciTech Connect

Experimental evidence is presented for confinement resonances associated with photoabsorption by a Xe atom in a C{sub 60} cage. The giant 4d resonance in photoionization of Xe is predicted to be redistributed into four components due to multipath interference of photoelectron waves reflected by the cage. The measurements were made in the photon energy range 60-150 eV by merging a beam of synchrotron radiation with a mass/charge selected Xe-C{sub 60}{sup +} ion beam. The phenomenon was observed in the Xe-C{sub 583}{sup +} product ion channel.

Kilcoyne, A. L. D.; Aguilar, A. [Advanced Light Source, LBNL, MS 7-100, Berkeley, California 94720-8225 (United States); Mueller, A.; Schippers, S. [IAMP, Justus-Liebig-Universitaet, Leihgesterner Weg 217, 35392 Giessen (Germany); Cisneros, C. [Instituto de Ciencias Fisicas, UNAM, A.P. 48-3, Cuernavaca, 62251 (Mexico); Alna'Washi, G. [Hashemite University, P.O. Box 150459, Zarqa 13115 (Jordan); Aryal, N. B.; Baral, K. K.; Esteves, D. A.; Thomas, C. M.; Phaneuf, R. A. [Department of Physics, University of Nevada, Reno, Nevada 89557-0220 (United States)

2010-11-19

287

Electronic excitation effects on radiation damage in insulators under ion irradiation  

NASA Astrophysics Data System (ADS)

To extract electronic excitation effects from the synergistic damage processes, we have studied photon-irradiation effects on insulators under heavy ion irradiation. Copper ions (Cu 2+) of 3 MeV energy at an ion flux of 2 ?A/cm 2 and 2.3 eV photons at 0.2 J/cm 2pulse were used to amorphous SiO 2 (KU-1) and spinel MgO·2.4(Al 2O 3), either sequentially or simultaneously to fluences up to 5 × 10 17 ions/cm 2. Atomic force microscopy and cross-sectional TEM were conducted to study the surface morphology and internal microstructure, respectively. The simultaneous photon irradiation at high photon densities significantly enhanced surface damage for the insulators, but alleviated bulk defects. The electronic excitation gave rise to significant reduction in dislocation loops in MgO·2.4(Al 2O 3), whereas single ion irradiation produced copious dislocation loops. The results demonstrate that intense electronic excitation, coexistent with heavy ions, excite transient sub-gap states and the absorbed energy results in enhancement of atomic migration, either damaging the surface or annealing the internal defects.

Kishimoto, N.; Okubo, N.; Plaksin, O. A.; Takeda, Y.

2004-08-01

288

Physical and chemical response of 145 MeV Ne 6+ ion irradiated polymethylmethacrylate (PMMA) polymer  

NASA Astrophysics Data System (ADS)

Characterization of ion induced modifications in the physical, chemical and structural properties of polymethylmethacrylate (PMMA) polymer induced by 145 MeV Ne6+ ions has been carried out by FTIR, UV-Visible, Differential scanning calorimetry (DSC) and X-ray diffraction. Heavy ion irradiation was carried out under a vacuum of ?10-6 torr at Variable Energy Cyclotron Centre, Kolkata, India using a low beam current (?15 nA). Ion fluences of 1010, 1011, 1012, 1013 ions/cm2 were used. The optical band gap (Eg), calculated from the absorption edge of the UV-Vis spectra of these films in 200-800 nm region varied from 2.167 eV to 1.512 eV for virgin and irradiated samples. In FTIR spectra appreciable changes have been observed after irradiation, indicating the molecular fragmentation, cross-linking, formation of unsaturated groups and free radicals. DSC thermograms give information about the thermal stability and type of thermal reactions (exothermic/endothermic) on the application of heat to the polymer. XRD analyses show slight shift of peak position and significant changes in peak intensity. XRD results show a decrease of ?4.12% in crystallite size of irradiated sample at the higher fluence of 1012 ions/cm2.

Kumar, Rajesh; Ali, S. A.; Singh, Paramjit; De, U.; Virk, H. S.; Prasad, Rajendra

2011-07-01

289

Evolution of glassy polymers used for gas separation following ion beam irradiation  

NASA Astrophysics Data System (ADS)

Commercial gas separation membranes are typically polymeric because of low cost, processibility and wide range of available properties. However, while much work has been done to develop improved polymers for membranes, these materials have limitations for many applications. Therefore, much work has been focused in post-formation modification of polymer membrane. In this work, two very different polymers were modified by ion irradiation to evaluate the evolution in chemical structure, microstructure and permeation properties. A specific focus was on the impact of ion choice on properties of a specific polymer. The first part of study focused on evolution in a typical commercial membrane polymer, polysulfone, following H+ irradiation. Ion irradiation of polysulfone resulted in significant evolution in chemical structure at intermediate H+ doses. There was a general decrease in permeance with little improvement in selectivity following irradiation. Modification of asymmetric polysulfone membranes by H+ and C- irradiation resulted in significant damage to the porous substrate of the membranes. Therefore, these membranes exhibited larger decreases in permeance then could be attributed to changes in the selective layer. The polyimide, 6FDA-6FpDA, was irradiated with three different ions, (H+, N+ and F+) to investigate impact of ion mass and energy transfer mechanisms. As expected the polymer responded different to the different ions at similar overall doses and total energy transfer. In general, more damage to the polymer matrix was achieved with larger mass ions. The larger relative evolution to microstructure was attributed to the greater nuclear loss mechanism for N+ and F+ relative to H+. Significant evolution in permeation properties corresponded to this change in chemical structure and microstructure. While the ions exhibited similar trends in evolution in permeation properties, there were large differences in scale of modification. For example, at high dose H+ irradiation, the gas pair He/CH4 exhibited significant increase in both permeance and permselectivity. However, F+ irradiation at high doses exhibited drastic decreases in permeance for all gases. Several irradiated samples exhibited permeation properties that were beyond the trade-off curve for tradition polymers. Therefore, with additional research, ideal conditions may be selected to optimize the changes in permeation properties.

Ilconich, Jeffery B.

290

Temperature-ramped (129)Xe spin-exchange optical pumping.  

PubMed

We describe temperature-ramped spin-exchange optical pumping (TR-SEOP) in an automated high-throughput batch-mode (129)Xe hyperpolarizer utilizing three key temperature regimes: (i) "hot"-where the (129)Xe hyperpolarization rate is maximal, (ii) "warm"-where the (129)Xe hyperpolarization approaches unity, and (iii) "cool"-where hyperpolarized (129)Xe gas is transferred into a Tedlar bag with low Rb content (<5 ng per ?1 L dose) suitable for human imaging applications. Unlike with the conventional approach of batch-mode SEOP, here all three temperature regimes may be operated under continuous high-power (170 W) laser irradiation, and hyperpolarized (129)Xe gas is delivered without the need for a cryocollection step. The variable-temperature approach increased the SEOP rate by more than 2-fold compared to the constant-temperature polarization rate (e.g., giving effective values for the exponential buildup constant ?SEOP of 62.5 ± 3.7 × 10(-3) min(-1) vs 29.9 ± 1.2 × 10(-3) min(-1)) while achieving nearly the same maximum %PXe value (88.0 ± 0.8% vs 90.1% ± 0.8%, for a 500 Torr (67 kPa) Xe cell loading-corresponding to nuclear magnetic resonance/magnetic resonance imaging (NMR/MRI) enhancements of ?3.1 × 10(5) and ?2.32 × 10(8) at the relevant fields for clinical imaging and HP (129)Xe production of 3 T and 4 mT, respectively); moreover, the intercycle "dead" time was also significantly decreased. The higher-throughput TR-SEOP approach can be implemented without sacrificing the level of (129)Xe hyperpolarization or the experimental stability for automation-making this approach beneficial for improving the overall (129)Xe production rate in clinical settings. PMID:25008290

Nikolaou, Panayiotis; Coffey, Aaron M; Barlow, Michael J; Rosen, Matthew S; Goodson, Boyd M; Chekmenev, Eduard Y

2014-08-19

291

Space Plasma Ion Processing of Ilmenite in the Lunar Soil: Insights from In-Situ TEM Ion Irradiation Experiments  

NASA Technical Reports Server (NTRS)

Space weathering on the moon and asteroids results largely from the alteration of the outer surfaces of regolith grains by the combined effects of solar ion irradiation and other processes that include deposition of impact or sputter-derived vapors. Although no longer considered the sole driver of space weathering, solar ion irradiation remains a key part of the space weathering puzzle, and quantitative data on its effects on regolith minerals are still in short supply. For the lunar regolith, previous transmission electron microscope (TEM) studies performed by ourselves and others have uncovered altered rims on ilmenite (FeTiO3) grains that point to this phase as a unique "witness plate" for unraveling nanoscale space weathering processes. Most notably, the radiation processed portions of these ilmenite rims consistently have a crystalline structure, in contrast to radiation damaged rims on regolith silicates that are characteristically amorphous. While this has tended to support informal designation of ilmenite as a "radiation resistant" regolith mineral, there are to date no experimental data that directly and quantitatively compare ilmenite s response to ion radiation relative to lunar silicates. Such data are needed because the radiation processed rims on ilmenite grains, although crystalline, are microstructurally and chemically complex, and exhibit changes linked to the formation of nanophase Fe metal, a key space weathering process. We report here the first ion radiation processing study of ilmenite performed by in-situ means using the Intermediate Voltage Electron Microscope- Tandem Irradiation facility (IVEM-Tandem) at Argonne National Laboratory. The capability of this facility for performing real time TEM observations of samples concurrent with ion irradiation makes it uniquely suited for studying the dose-dependence of amorphization and other changes in irradiated samples.

Christoffersen, R.; Keller, L. P.

2007-01-01

292

Biodamage via shock waves initiated by irradiation with ions.  

PubMed

Radiation damage following the ionising radiation of tissue has different scenarios and mechanisms depending on the projectiles or radiation modality. We investigate the radiation damage effects due to shock waves produced by ions. We analyse the strength of the shock wave capable of directly producing DNA strand breaks and, depending on the ion's linear energy transfer, estimate the radius from the ion's path, within which DNA damage by the shock wave mechanism is dominant. At much smaller values of linear energy transfer, the shock waves turn out to be instrumental in propagating reactive species formed close to the ion's path to large distances, successfully competing with diffusion. PMID:23411473

Surdutovich, Eugene; Yakubovich, Alexander V; Solov'yov, Andrey V

2013-01-01

293

Temperature dependence of damage formation in Ag ion irradiated 4H-SiC  

NASA Astrophysics Data System (ADS)

Rutherford backscattering spectrometry (RBS) in channelling mode was used to study the defect formation in silver (Ag) ion irradiated silicon carbide (SiC). The 4H-SiC samples were irradiated with 360 keV Ag ions at different temperatures (15, 295, 375, 475, 625 and 875 K) over a wide range of fluences ( 1×1011 to 2×1016 cm, depending on the irradiation temperature). The results can be divided into two groups: (i) for irradiation temperatures between 15 and 475 K amorphisation of the implanted layers is reached for ion fluences between 7×1013 and 3×1014 cm. The over-all cross-section of defect production at very low ion fluences which comprises the formation of point defects and of amorphous clusters, is almost identical for all data sets measured in this temperature range. Differences in the damage evolution which occur at higher ion fluences, suggest that the relative contribution of amorphous clusters within single ion impacts in crystalline material decreases with rising temperature. (ii) For irradiations performed at 625 and 875 K no amorphisation is found for ion fluences as high as 2×1016 cm. With increasing ion fluence the defect concentration exhibits a distinctive plateau due to the balance between formation and recombination of point defects before increasing up to a saturation level well below amorphisation. For this final stage our results indicate a mixture of point defect clusters and extended defects most probably dislocations. A comparison with data from the literature suggests that the damage evolution for implantation at 625 and 875 K is strongly influenced by the mobility of vacancies starting at around 600 K.

Wendler, E.; Bierschenk, Th.; Wesch, W.; Friedland, E.; Malherbe, J. B.

2010-10-01

294

Fabrication of Nano-Columnar Tungsten Films and Their Deuterium and Helium Ion Irradiation Effects  

NASA Astrophysics Data System (ADS)

We fabricate nano-columnar tungsten (W) films on polycrystalline silicon substrates by magnetron sputtering using a grazing angle deposition technique. The deposition process is performed at a base pressure of 5×10?4 Pa. The intersection angle between the direction of the incident beam and the normal direction of the substrate is set as 85°. Separate as well as synergetic irradiations of 30/50 keV deuterium ions and 60 keV helium ions are carried out for the nano-columnar W. Samples of normal structure W are also irradiated under the same conditions as a comparison. Scanning electron microscopy and x-ray diffraction are used to characterize the structure of the as-prepared as well as the irradiated samples. The experimental results show that blisters are difficult to form on the surface of nano-columnar W under the irradiation conditions in this work, which could be due to the particular structure.

Cai, Ya-Nan; Han, Wen-Jia; Chen, Zhe; Yu, Jian-Gang; Feng, Hong-Li; Zhu, Kai-Gui

2014-12-01

295

Surface reformation and electro-optical characteristics of liquid crystal alignment layers using ion beam irradiation  

SciTech Connect

The surface modification characteristics of liquid crystal (LC) alignment layers irradiated with various argon (Ar) ion beam (IB) energies were investigated as a substitute for rubbing technology. Various pretilt angles were created on the IB-irradiated polyimide (PI) surfaces after IB irradiation, but the Ar ions did not alter the morphology on the PI surface, indicating that the pretilt angle was not due to microgrooves. The chemical bonding states of the IB-irradiated PI surfaces were analyzed in detail by x-ray photoelectron spectroscopy to verify the compositional behavior for the LC alignment. Chemical structure analysis showed that the alignment ability of LCs was due to the preferential reorientation of the carbon network due to the breaking of C=O double bonds in the imide ring parallel to the incident IB direction. The potential of applying nonrubbing technology to display devices was further supported by the superior electro-optical characteristics compared to rubbed PI.

Oh, Byeong-Yun; Lee, Kang-Min; Kim, Byoung-Yong; Kim, Young-Hwan; Han, Jin-Woo; Han, Jeong-Min; Lee, Sang-Keuk; Seo, Dae-Shik [Information Display Device Laboratory, Department of Electrical and Electronic Engineering, Yonsei University, 262 Seongsanno, Seodaemun-gu, Seoul 120-749 (Korea, Republic of)

2008-09-15

296

Performance Measurement: XE6  

NSDL National Science Digital Library

The purpose of this guide is to suggest how to monitor the runtime behaviour of the user application and hence to obtain better information to apply performance-tuning optimisations on the XE6 machine. This process is called performance measurement, and profiling tools (alternatively called performance measurement tools) are available on HECToR to help users identify the bottlenecks of their code. This guide covers what and how to measure.

297

Manipulation of transport hysteresis on graphene field effect transistors with Ga ion irradiation  

NASA Astrophysics Data System (ADS)

We have studied the effect of Ga ion irradiation on the controllable hysteretic behavior of graphene field effect transistors fabricated on Si/SO2 substrates. The various densities of defects in graphene were monitored by Raman spectrum. It was found that the Dirac point shifted to the positive gate voltage constantly, while the hysteretic behavior was enhanced first and then weakened, with the dose of ion irradiation increasing. By contrasting the trap charges density induced by dopant and the total density of effective trap charges, it demonstrated that adsorbate doping was not the decisive factor that induced the hysteretic behavior. The tunneling between the defect sites induced by ion irradiation was also an important cause for the hysteresis.

Wang, Quan; Liu, Shuai; Ren, Naifei

2014-09-01

298

First tests of the ion irradiation and implantation beamline at the CMAM  

NASA Astrophysics Data System (ADS)

The implantation and irradiation beamline of the Tandem ion accelerator of the Centro de Micro Análisis de Materiales (CMAM), in Madrid, has been recently completed with a beam sweep and monitoring system, and a cryostat/furnace. These new implementations convert the beamline into a versatile tool to implant ions, between H and Au2, in different materials with precise control of the sample temperature, which may be varied between -180 °C and 600 °C. The size of the swept area on target may be as large as 10 × 10 cm2. The implantation chamber also allows carrying out in situ or/and on line analyses during the irradiations by means of advanced optical measurements, as well as ion beam analyses (IBA). These advancements can be employed in novel applications such as the fabrication of optical waveguides and irradiation tests of structural and functional materials for future fusion reactors. The results of beam tests and first experiments are shown.

Jiménez-Rey, D.; Benedicto, M.; Muñoz-Martín, A.; Bachiller-Perea, D.; Olivares, J.; Climent-Font, A.; Gómez-Ferrer, B.; Rodríguez, A.; Narros, J.; Maira, A.; Álvarez, J.; Nakbi, A.; Zucchiatti, A.; de Aragón, F.; García, J. M.; Vila, R.

2014-07-01

299

The local reaction processes of polyethylene irradiated with heavy ion-beam  

Microsoft Academic Search

The local reaction induced in the track for low-density polyethylene irradiated with ion-beam was investigated. The transformations of the chemical structure induced by irradiation are on trans-vinylene, end-vinyl, vinylidine and the cross-link. The different reaction processes are induced in the micro-region of the track. These processes depend on the stopping power. In the region of larger stopping power, the rate

Yoshimasa Hama; Toshitaka Oka

2005-01-01

300

Role of impact parameter in branching reactions: Chemical accelerator studies of the reaction Xe++CH4?XeCH3 ++H  

E-print Network

Integral reaction cross sections and product velocity distributions have been measured for the ion–molecule reaction Xe+(CH4,H)XeCH3 + over the relative reactant translational energy range of 0.7–5.5 eV by chemical accelerator techniques...

Miller, G. D.; Strattan, L. W.; Hierl, Peter M.

1981-01-01

301

Microstructure evolution of metallic nanocrystalline thin-films under ion-beam irradiation  

NASA Astrophysics Data System (ADS)

The microstructural evolution of nanocrystalline metallic thin-films under ion irradiation, especially grain growth and second-phase precipitation, was studied with detailed in situ experiments, and a theoretical model was developed to explain the results of grain-growth. Free-standing Zr, Pt, Cu and Au, Cu-Fe, and Zr-Fe nanocrystalline thin films prepared by sputter deposition 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 at temperatures ranging from 20 to 773 K. The microstructural evolution of the thin-films was followed in situ by systematically recording bright field images and diffraction patterns at successive ion-irradiation doses. Grain growth was observed as a result of irradiation in all samples at all irradiation temperatures. The results suggest the existence of three regimes with increasing irradiating temperature: a low temperature regime (below about 0.15 to 0.22 Tm) where grain-growth does not depend on the irradiation temperature, a thermally assisted regime where both the grain-growth rate and the final grain size increase with increasing irradiation temperature, and a thermal regime where thermal effects dominate ion beam effects. Similarly to thermal grain growth, the ion-irradiation induced grain growth curves could be best fitted with curves of the type: Dn-Dn0=KF with n˜3 in the low temperature regime. The effect of solute addition on grain-growth was investigated using Zr(Fe) and Cu(Fe) supersaturated solid-solutions. In the case of Zr-Fe, Zr2Fe precipitates formed during irradiation (with the dose-to-precipitation of Zr2Fe decreasing with increasing irradiation temperature), whereas Cu-Fe remained as a solid-solution. The grain-growth rate and final size decreased in both alloys with respect to the pure metallic films as a result of second-phase particle pinning (Zener drag) (Zr-Fe), and solute drag (Cu-Fe). The grain-growth rate was found to depend on material and on irradiation conditions. In particular, neither grain-growth nor precipitation occurred under 1 MeV electron irradiation. Combined with rate-theory calculations, this shows that long range diffusion does not play a role in the process. A model of grain-growth under ion irradiation in the temperature-independent regime was developed, based on direct impact of irradiation-induced thermal spikes on grain-boundaries. Grain-boundary migration occurs by atomic jumps within the thermal spike biased by the grain-boundary curvature driving force. The model incorporates cascade structure features such as subcascade formation, and the probability of subcascades occurring at grain-boundaries. This results in a power law expression relating the average grain-size with the ion dose, where the exponent is 3 in agreement with the experimental data. In the thermally assisted regime, the increased grain-growth is explained within the framework of the same model, by the increased thermal spike size with higher substrate temperature. At the highest temperatures, other effects such as subcascade overlap and point defect migration to sinks may also enhance the process.

Kaoumi, Djamel

302

Modifications in magnetic anisotropy of M—type strontium hexaferrite crystals by swift heavy ion irradiation.  

NASA Astrophysics Data System (ADS)

Using vibrating sample magnetometery (VSM) 50 MeV Li 3+ ion irradiation effects on magnetic properties of single crystals of SrGa xIn yFe 12-(x+y)O 19 (where x=0, 5, 7, 9; y=0, 0.8, 1.3, 1.0), are reported. The substitution of Ga and In in strontium hexaferrite crystals decreases the value of magnetization sharply, which is attributed to shifting of collinear magnetic order to a non-collinear one. Reduction of magnetization is also explained to be as a result of the occupation of the crystallographic sites of Fe 3+ by Ga 3+ and In 3+. The Li 3+ ion irradiation decreases the value of magnetization, irrespective of whether the crystals are Ga-In substituted or unsubstituted crystals of SrFe 12O 19. The result is interpreted in terms of the occurrence of a paramagnetic doublet in crystals replacing magnetic sextuplet as a result of irradiation. Substitution of Ga-In in Strontium hexaferrite decreases the value of anisotropy constant. Irradiation with Li 3+ ions increases the values of anisotropy field for both substituted as well as unsubstituted crystals. Substitution with Ga-In also decreases the Curie temperature ( Tc) but the irradiation with Li 3+ ions does not affect the curie temperature of either Ga-In substituted or pure SrFe 12O 19 crystals.

Kaur, Balwinder; Bhat, Monita; Licci, F.; Kumar, Ravi; Kulkarni, S. D.; Joy, P. A.; Bamzai, K. K.; Kotru, P. N.

2006-10-01

303

Effect of swift heavy ion irradiation on bare and coated ZnS quantum dots  

SciTech Connect

The present study compares structural and optical modifications of bare and silica (SiO{sub 2}) coated ZnS quantum dots under swift heavy ion (SHI) irradiation. Bare and silica coated ZnS quantum dots were prepared following an inexpensive chemical route using polyvinyl alcohol (PVA) as the dielectric host matrix. X-ray diffraction (XRD) and transmission electron microscopy (TEM) study of the samples show the formation of almost spherical ZnS quantum dots. The UV-Vis absorption spectra reveal blue shift relative to bulk material in absorption energy while photoluminescence (PL) spectra suggests that surface state and near band edge emissions are dominating in case of bare and coated samples, respectively. Swift heavy ion irradiation of the samples was carried out with 160 MeV Ni{sup 12+} ion beam with fluences 10{sup 12} to 10{sup 13} ions/cm{sup 2}. Size enhancement of bare quantum dots after irradiation has been indicated in XRD and TEM analysis of the samples which has also been supported by optical absorption spectra. However similar investigations on irradiated coated quantum dots revealed little change in quantum dot size and emission. The present study thus shows that the coated ZnS quantum dots are stable upon SHI irradiation compared to the bare one.

Chowdhury, S. [Department of Physics, Gauhati University, Guwahati, Assam 781014 (India)], E-mail: sky@tezu.ernet.in; Hussain, A.M.P. [Department of Physics, Gauhati University, Guwahati, Assam 781014 (India); Ahmed, G.A. [Department of Physics, Tezpur University, Napaam, Tezpur, Assam 784028 (India); Singh, F.; Avasthi, D.K. [Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110067 (India); Choudhury, A. [Department of Physics, Tezpur University, Napaam, Tezpur, Assam 784028 (India)

2008-12-01

304

Low energy Ar+ ion irradiation induced surface modification in cadmium zinc telluride (CdZnTe)  

NASA Astrophysics Data System (ADS)

In this paper, we report on modifications in structural, stoichiometry, and optical properties of cadmium zinc telluride (CdZnTe) crystals due to 1 keV Ar+ ion irradiation as a function of ion fluence, using ion flux of 1.7 × 1017 ions cm-2 s-1. The CdZnTe crystals were irradiated at normal incidence, using fluence range of 8 × 1017-3 × 1019 ions cm-2. Atomic force microscopy studies show sequential change in surface structure as a function of ion fluence, from homogeneously populated nano-hole to micron sized holes on the entire CZT crystal surface. These holes are well geometrically defined and most of them are rectangular in shape. X-ray photoelectron spectroscopy studies show a reduction in Zn at % while Raman and photoluminescence studies show almost complete depletion of Te inclusions and slight red shifts, respectively, due to ion irradiations. Schottky diode radiation detectors fabricated from such defect free CZT crystals will show significantly higher energy resolution.

Tripathi, J. K.; Harilal, S. S.; Hassanein, A.

2014-09-01

305

Enhancement of ferromagnetism in Pd nanoparticle by swift heavy ion irradiation  

SciTech Connect

In this study, the effect of swift heavy ion irradiation on the magnetic properties of the Pd nanoparticles has been investigated. Structural investigations along with superconducting quantum interface device measurements show that ferromagnetic properties of the Pd nanoparticles are due to the deviation of their electronic structure from that of bulk. The electronic structure is further modified due to the creation of defects on ion irradiation, which results in 20 times increase in the saturation magnetization. The present study establishes that the defect induced modification of Pd 4d electronic structure is responsible for the ferromagnetic properties of the Pd nanoparticles.

Kulriya, P. K. [Department of Physics, Thin Film Laboratory, Indian Institute of Technology, New Delhi 110 016 (India); Inter-University Accelerator Centre, Aruna Asaf Ali Road, New Delhi 110067 (India); Mehta, B. R. [Department of Physics, Thin Film Laboratory, Indian Institute of Technology, New Delhi 110 016 (India); Avasthi, D. K.; Agarwal, D. C. [Inter-University Accelerator Centre, Aruna Asaf Ali Road, New Delhi 110067 (India); Thakur, P.; Brookes, N. B. [European Synchrotron Radiation Facility (ESRF), BP 220, F-38043 Grenoble Cedex (France); Chawla, A. K.; Chandra, R. [Nanoscience Laboratory, Institute Instrumentation Centre, Indian Institute of Technology Roorkee, Roorkee 247667 (India)

2010-02-01

306

Evaluation of Surface Damage of Organic Films due to Irradiation with Energetic Ion Beams  

SciTech Connect

The surface of L-leucine films irradiated with an Ar{sub 5000} cluster ion beam (5 keV) was characterized by using the X-ray reflective (XRR) measurement method, atomic force microscopy (AFM) and ellipsometry. No significant damage was detected on the surface of the L-leucine films irradiated with the Ar cluster ion beam. Therefore, the large cluster-low-energy (about 1 eV/atom) beam would be suitable for low-damage etching of organic materials.

Hada, Masaki; Hontani, Yusaku; Ichiki, Kazuya; Seki, Toshio [Department of Nuclear Engineering, Kyoto University, Sakyo, Kyoto, 606-8501 (Japan); Ibuki, Sachi; Ninomiya, Satoshi; Matsuo, Jiro [Quantum Science and Engineering Center, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Aoki, Takaaki [Department of Electronic Science and Engineering, Kyoto University, Nishigyo, Kyoto, 615-8530 (Japan)

2011-01-07

307

Tuning perpendicular anisotropy gradient in Co/Pd multilayers by ion irradiation  

NASA Astrophysics Data System (ADS)

The tunability of Ar+ ion irradiation of Co/Pd multilayers has been employed to create depth-dependent perpendicular anisotropy gradients. By adjusting the Ar+ kinetic energy and fluence, the depth and lateral density of the local structural modification are controlled. First-order reversal curve analysis through X-ray magnetic circular dichroism and conventional magnetometry studies shows that the local structural damage weakens the perpendicular anisotropy near the surface, leading to a magnetization tilting towards the in-plane direction. The ion irradiation method is complementary to and may be used in conjunction with, other synthesis approaches to maximize the anisotropy gradient.

Greene, Peter K.; Osten, Julia; Lenz, Kilian; Fassbender, Jürgen; Jenkins, Catherine; Arenholz, Elke; Endo, Tamio; Iwata, Nobuyuki; Liu, Kai

2014-08-01

308

Combined high pressure and heavy-ion irradiation: a novel approach.  

PubMed

Swift heavy-ion irradiations of a wide variety of materials have been used to modify and manipulate the properties of solids at the nanoscale. Recently, these high-energy irradiations have been successfully combined with high-pressure experiments. Based on results obtained for zircon (ZrSiO(4)), this paper introduces this new experimental approach involving diamond anvil cells and large ion-accelerator facilities. This technique provides a wide spectrum of geoscience applications from nanoscale simulations of fission-track formation under crustal conditions to phase transitions of radiation-damaged minerals resulting from meteorite impact. PMID:19844013

Lang, Maik; Zhang, Fuxiang; Lian, Jie; Trautmann, Christina; Neumann, Reinhard; Ewing, Rodney C

2009-11-01

309

Combined High Pressure and Heavy-Ion Irradiation: a Novel Approach  

SciTech Connect

Swift heavy-ion irradiations of a wide variety of materials have been used to modify and manipulate the properties of solids at the nanoscale. Recently, these high-energy irradiations have been successfully combined with high-pressure experiments. Based on results obtained for zircon (ZrSiO{sub 4}), this paper introduces this new experimental approach involving diamond anvil cells and large ion-accelerator facilities. This technique provides a wide spectrum of geoscience applications from nanoscale simulations of fission-track formation under crustal conditions to phase transitions of radiation-damaged minerals resulting from meteorite impact.

Lang, M.; Zhang, F; Lian, J; Trautmann, C; Neumann, R; Ewing, R

2009-01-01

310

Determination of the emission probability of the principal gamma ray of 135Xe  

NASA Astrophysics Data System (ADS)

The gamma ray emission probability is one of the most important characteristics used in quantifying radionuclides. This article describes in detail the principles and processes involved in the determination of the 135Xe gamma ray emission probability. Gaseous samples of 135Xe were generated by irradiating enriched 134Xe with a thermal neutron flux. The principal gamma ray emission probability of 135Xe was then determined to be 0.896±0.016 (k=1) by measuring the absolute activity using length-compensated internal gas proportional counters and ?-ray intensity using a high-purity germanium (HPGe) detector.

Li, Qi; Wang, Shilian; Jia, Huaimao; Fan, Yuanqing; Zhang, Xinjun; Chen, Zhanying; Zhao, Yungang; Chang, Yinzhong; Liu, Shujiang

2013-03-01

311

Mutation induction in bacteria after heavy ion irradiation  

NASA Technical Reports Server (NTRS)

From a compilation of experimental data on the mutagenic effects of heavy ions in bacteria, main conclusions have been drawn as follows: (1) The mutagenic efficacy of heavy ions in bacteria depends on physical and biological variables. Physical variables are the radiation dose, energy and charge of the ion; the biological variables are the bacterial strain, the repair genotype of bacteria, and the endpoint investigated (type of mutation, induction of enzymes related to mutagenesis); (2) The responses on dose or fluence are mainly linear or linear quadratic. The quadratic component, if found for low LET radiation, is gradually reduced with increasing LET; (3) At low values of Z and LET the cross section of mutation induction sigma m (as well as SOS response, sigma sos. and lambda phage induction, sigma lambda versus LET curves can be quite consistently described by a common function which increases up to approximately 100 keV/mu m. For higher LET values, the sigma(m) versus LET curves show the so-called 'hooks' observed also for other endpoints; (4) For light ions (Z is less than or equal to 4), the cross sections mostly decrease with increasing ion energy, which is probably related to the decrease of the specific energy departed by the ion inside the sensitive volume (cell). For ions in the range of Z = 10, sigma(m) is nearly independent on the ion energy. For heavier ions (Z is greater than or equal to 16), sigma(m) increases with the energy up to a maximum or saturation around 10 MeV/u. The increment becomes steeper with increasing atomic number of the ion. It correlates with the increasing track radius of the heavy ion; (5) The mutagenic efficiency per lethal event changes slightly with ion energy, if Z is small indicating a rough correlation between cellular lethality and mutation induction, only. For ions of higher Z this relation increases with energy, indicating a change in the 'mode' of radiation action from 'killing-prone' to 'mutation-prone'; and (6) Repair genotype substantially influences the radiation induced mutagenesis. Different mechanisms of mutation induction and/or different types of biologically significant lesions in wild type cells compared to repair deficient strains are a likely explanation.

Horneck, G.; Kozubek, S.

1994-01-01

312

Incorporation of the effect of the composite electric fields of molecular ions as a simulation tool for biological damage due to heavy ion irradiation II  

NASA Astrophysics Data System (ADS)

This paper presents a theoretical study of the DNA damage due to the effect of the composite electric fields of H2O+ ions produced from the irradiation of a heavy ion onto a cell. It is found that a much larger number of electrons, which are produced from electron impact ionization, is trapped near the track of an incident ion in the case of C6+ ion irradiation with the energy of 3 MeV/u than that of proton irradiation. Therefore, the irradiation of carbon ions may produce a larger number of cluster DNA damage than that in the irradiation of protons. This may lead to the understanding of relative biological effectiveness (RBE).

Moribayashi, Kengo

2012-07-01

313

Activated Ion Electron Capture Dissociation (AI ECD) of Proteins: Synchronization of Infrared and Electron Irradiation with Ion Magnetron Motion  

PubMed Central

Here, we show that to perform activated ion electron capture dissociation (AI-ECD) in a Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer equipped with a CO2 laser, it is necessary to synchronize both infrared irradiation and electron capture dissociation with ion magnetron motion. This requirement is essential for instruments in which the infrared laser is angled off-axis, such as the Thermo Finnigan LTQ FT. Generally, the electron irradiation time required for proteins is much shorter (ms) than that required for peptides (tens of ms), and the modulation of ECD, AI ECD, and infrared multiphoton dissociation (IRMPD) with ion magnetron motion is more pronounced. We have optimized AI ECD for ubiquitin, cytochrome c, and myoglobin; however the results can be extended to other proteins. We demonstrate that pre-ECD and post-ECD activation are physically different and display different kinetics. We also demonstrate how, by use of appropriate AI ECD time sequences and normalization, the kinetics of protein gas-phase refolding can be deconvoluted from the diffusion of the ion cloud and measured on the time scale longer than the period of ion magnetron motion. PMID:19200749

Mikhailov, Victor A.; Cooper, Helen J.

2009-01-01

314

Graphitic nanostripes in silicon carbide surfaces created by swift heavy ion irradiation.  

PubMed

The controlled creation of defects in silicon carbide represents a major challenge. A well-known and efficient tool for defect creation in dielectric materials is the irradiation with swift (E(kin) ? 500 keV/amu) heavy ions, which deposit a significant amount of their kinetic energy into the electronic system. However, in the case of silicon carbide, a significant defect creation by individual ions could hitherto not be achieved. Here we present experimental evidence that silicon carbide surfaces can be modified by individual swift heavy ions with an energy well below the proposed threshold if the irradiation takes place under oblique angles. Depending on the angle of incidence, these grooves can span several hundreds of nanometres. We show that our experimental data are fully compatible with the assumption that each ion induces the sublimation of silicon atoms along its trajectory, resulting in narrow graphitic grooves in the silicon carbide matrix. PMID:24905053

Ochedowski, Oliver; Osmani, Orkhan; Schade, Martin; Bussmann, Benedict Kleine; Ban-d'Etat, Brigitte; Lebius, Henning; Schleberger, Marika

2014-01-01

315

Irradiation of ionic liquid ion beams on silicon and glass substrates  

NASA Astrophysics Data System (ADS)

Irradiation of an ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF6) ion beam on borosilicate glass and single crystalline Si(100) surface was demonstrated by using an ionic liquid ion source we developed. Surface smoothing on the glass substrates was produced by the irradiations at an acceleration voltage of 4 kV with both positive and negative ion beams, which include cation-anion pairs attached to a single ion of either polarity. Water contact angle measurements and X-ray photoelectron spectroscopy indicated that the surface smoothing was probably caused by surface modification involving nano-ordered chemical etching by Si-F reaction, implantation and deposition of P, N and C.

Takeuchi, Mitsuaki; Hamaguchi, Takuya; Ryuto, Hiromichi; Takaoka, Gikan H.

2013-11-01

316

Surface processes occurring on PVDF under energetic ion irradiation  

Microsoft Academic Search

Modifications induced in polyvinylidene fluoride by energetic ions (E >= 1 MeV\\/amu) have been reported in previous papers [1-3]. It was shown by using methods such as X-ray photoemission spectroscopy (XPS), infrared absorption spectroscopy (IRAS), electron spin resonance (RPE) or differential scanning calorimetry (DSC) that light and very heavy ions lead to opposite modifications of the polymer. Superficial unsaturations characterized

A. Fina; A. Le Moel; J. P. Duraud; M. T. Valin; C. Le Gressus; E. Balanzat; J. M. Ramillon; C. Darnez

1989-01-01

317

Nitride and carbonitride layers of titanium formed under high energy ion irradiation  

Microsoft Academic Search

Titanium nitride and carbonitride films were formed by evaporating titanium while simultaneously irradiating with energetic nitrogen ions in an atmosphere of N2 and C2H2+N2, respectively. The physical and chemical properties, such as composition, purity, hardness, adhesion and corrosion resistance behaviour, were examined with respect to the process parameters such as nitrogen ion current density and the process pressure of the

W. Ensinger; J. M. Mayne

1991-01-01

318

Effect of ?-irradiation of ion imprinted polymer (IIP) particles for the preconcentrative separation of dysprosium from other selected lanthanides  

Microsoft Academic Search

The selectivity of zinc with respect to copper ions was improved by ?-irradiation of surface imprinted polymer particles. We have reported the preparation of dysprosium ion imprinted polymer (IIP) particles by covalent approach during molecular imprinting. This paper reports the results obtained after ?-irradiation of dysprosium IIP particles and their use in the preconcentration\\/separation of dysprosium from dilute aqueous solutions

V. M Biju; J. Mary Gladis; T. Prasada Rao

2003-01-01

319

Static elasticity of cordierite I: Effect of heavy ion irradiation on the compressibility of hydrous cordierite  

NASA Astrophysics Data System (ADS)

The effect of ion beam irradiations on the elastic properties of hydrous cordierite was investigated by means of Raman and X-ray diffraction experiments. Oriented single crystals were exposed to swift heavy ions (Au, Bi) of various specific energies (10.0-11.1 MeV/u and 80 MeV/u), applying fluences up to 5 × 1013 ions/cm2. The determination of unit-cell constants yields a volume strain of 3.4 × 10-3 up to the maximum fluence, which corresponds to a compression of non-irradiated cordierite at ~480 ± 10 MPa. The unit-cell contraction is anisotropic ( e 1 = 1.4 ± 0.1 × 10-3, e 2 = 1.5 ± 0.1 × 10-3, and e 3 = 7 ± 1 × 10-4) with the c-axis to shrink only half as much as the axes within the ab-plane. The lattice elasticity for irradiated cordierite ( ? = 1 × 1012 ions/cm2) was determined from single-crystal XRD measurements in the diamond anvil cell. The fitted third-order Birch-Murnaghan equation-of-state parameters of irradiated cordierite ( V 0 = 1548.41 ± 0.16 Å3, K 0 = 117.1 ± 1.1 GPa, ? K/? P = -0.6 ± 0.3) reveal a 10-11 % higher compressibility compared to non-irradiated cordierite. While the higher compressibility is attributed to the previously reported irradiation-induced loss of extra-framework H2O, the anomalous elasticity as expressed by elastic softening ( ? {a/-1}, ? {b/-1}, ? {c/-1} = 397 ± 9, 395 ± 28, 308 ± 11 GPa, ?( ? -1)/? P = -4.5 ± 2.7, -6.6 ± 8.4, -5.4 ± 3.0) appears to be related to the framework stability and to be independent of the water content in the channels and thus of the ion beam exposure.

Miletich, R.; Scheidl, K. S.; Schmitt, M.; Moissl, A. P.; Pippinger, T.; Gatta, G. D.; Schuster, B.; Trautmann, C.

2014-09-01

320

Tuning the surface properties of hydrogel at the nanoscale with focused ion irradiation.  

PubMed

With the site-specific machining capability of Focused Ion Beam (FIB) irradiation, we aim to tailor the surface morphology and physical attributes of biocompatible hydrogel at the nano/micro scale particularly for tissue engineering and other biomedical studies. Thin films of Gtn-HPA/CMC-Tyr hydrogels were deposited on a gold-coated substrate and were subjected to irradiation with a kiloelectronvolt (keV) gallium ion beam. The sputtering yield, surface morphology and mechanical property changes were investigated using Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and Monte Carlo simulations. The sputtering yield of the hydrogel was found to be approximately 0.47 ?m(3) nC(-1) compared with Monte-Carlo simulation results of 0.09 ?m(3) nC(-1). Compared to the surface roughness of the pristine hydrogel at approximately 2 nm, the average surface roughness significantly increased with the increase of ion fluence with measurements extended to 20 nm at 100 pC ?m(-2). Highly packed submicron porous patterns were also revealed with AFM, while significantly decreased pore sizes and increased porosity were found with ion irradiation at oblique incidence. The Young's modulus of irradiated hydrogel determined using AFM force spectroscopy was revealed to be dependent on ion fluence. Compared to the original Young's modulus value of 20 MPa, irradiation elevated the value to 250 MPa and 350 MPa at 1 pC ?m(-2) and 100 pC ?m(-2), respectively. Cell culture studies confirmed that the irradiated hydrogel samples were biocompatible, and the generated nanoscale patterns remained stable under physiological conditions. PMID:25225831

Kim, Y; Abuelfilat, A Y; Hoo, S P; Al-Abboodi, A; Liu, B; Ng, Tuck; Chan, P; Fu, J

2014-11-14

321

The Influence of High-Energy Lithium Ion Irradiation on Electrical Characteristics of Silicon and GaAs Solar Cells  

E-print Network

Space-grade Si and GaAs solar cells were irradiated with 15 & 40 MeV Li ions. Illuminated (AM0 condition) and unilluminated I-V curves reveal that the effect of high-energy Li ion irradiation has produced similar effects to that of proton irradiation. However, an additional, and different, defect mechanism is suggested to dominate in the heavier-ion results. Comparison is made with proton-irradiated solar-cell work and with non-ionizing energy-loss (NIEL) radiation-damage models.

B. Jayashree; Ramani; M. C. Radhakrishna; Anil Agrawal; Saif Ahmad Khan; A. Meulenberg

2006-10-22

322

Microstructural evolution of CANDU spacer material Inconel X-750 under in situ ion irradiation  

NASA Astrophysics Data System (ADS)

Work on Inconel®Inconel® is a registered trademark of Special Metals Corporation that refers to a family of austenitic nickel-chromium-based superalloys.1 X-750 spacers removed from CANDU®CANDU® is a registered trademark of Atomic Energy of Canada Limited standing for ''CANada Deuterium Uranium''.2 reactors has shown that they become embrittled and there is development of many small cavities within the metal matrix and along grain boundaries. In order to emulate the neutron irradiation induced microstructural changes, heavy ion irradiations (1 MeV Kr2+ ions) were performed while observing the damage evolution using an intermediate voltage electron microscope (IVEM) operating at 200 kV. The irradiations were carried out at various temperatures 60-400 °C. The principal strengthening phase, ??, was disordered at low doses (˜0.06 dpa) during the irradiation. M23C6 carbides were found to be stable up to 5.4 dpa. Lattice defects consisted mostly of stacking fault tetrahedras (SFTs), 1/2<1 1 0> perfect loops and small 1/3<1 1 1> faulted Frank loops. The ratio of SFT number density to loop number density for each irradiation condition was found to be neither temperature nor dose dependent. Under the operation of the ion beam the SFT production was very rapid, with no evidence for further growth once formed, indicating that they probably formed as a result of cascade collapse in a single cascade. The number density of the defects was found to saturate at low dose (˜0.68 dpa). No cavities were observed regardless of the irradiation temperature between 60 °C and 400 °C for doses up to 5.4 dpa. In contrast, cavities have been observed after neutron irradiation in the same material at similar doses and temperatures indicating that helium, produce during neutron irradiation, may be essential for the nucleation and growth of cavities.

Zhang, He Ken; Yao, Zhongwen; Judge, Colin; Griffiths, Malcolm

2013-11-01

323

Effect of heavy-ion and electron irradiation on properties of Fe-based superconductors  

NASA Astrophysics Data System (ADS)

The introduction of defects by particle irradiation is used to reveal the role of disorder in matter, which is unavoidable in all crystalline solids. In superconductors defects introduce flux pinning, controlling critical current, Jc; as well as pair-breaking scattering, limiting the critical temperature, Tc. To elucidate defect related properties of Fe-based superconductors (FBS) we precede in two types of irradiation: heavy ion (6GeV Pb) to create disorder in the form of amorphous tracks and low temperature electron irradiation (2.5MeV at 20K) to create point like defects. Substantial increase of irreversible magnetization and an upward shift of the irreversibility line are observed after heavy ion irradiation of all FBS investigated to date. In BaK122, signatures of a Bose-glass vortex state; angular dependence and variable-range hopping flux creep are revealed. Remarkably, heavy ion irradiation does not depress Tc, however, point-like disorder introduced by electron irradiation does substantially. In isovalently substituted Ba(FeAs1-xPx)2 and Ba(Fe1-xRuxAs)2 crystals, Tc decreases linearly with dose. Suppression to 40% of initial value of Tc was achieved in Ba(FeAs1-xPx)2. An increase of normal state resistivity is observed and correlated to depression of Tc. Change of superconducting gap structure with disorder was determined from penetration depth measurements, ?(T) dependence, at various stages of irradiation. Linear in T variation of pristine samples, indicative of the presence of nodes in gap, turned at low irradiation dose to exponential T variation, indicative of a fully gaped state. T^2 variation of ? is observed at higher doses. This behaviour is incompatible with symmetry-imposed nodes of d-wave pairing but consistent with S+/-, S+/+ mechanisms. This is the first observation of the impurity-induced node lifting expected in anisotropic s-wave superconductors

Konczykowski, Marcin

2013-03-01

324

Charge-exchange EUV spectroscopy in collisions of Xe{sup q+} (q=7-9) with rare gases  

SciTech Connect

Extreme ultraviolet (EUV) emission spectra have been measured in charge exchange collisions between Xe{sup q+} (q=7--9) and rare gases at an energy of 20 q keV. We have observed 4, 22, and 39 lines in collisions of Xe{sup 7+}, Xe{sup 8+}, and Xe{sup 9+}. Of these emission lines, four lines of Xe vii, eight lines of Xe viii, and nine lines of Xe ix correspond to newly observed transitions. The identification procedure is described in detail. The aim of this work is to obtain spectroscopic data for multiply charged Xe ions. In addition, the electron capture mechanism is also discussed using the crude classical over-the-barrier model to understand the target dependence of the emission spectra.

Tanuma, H.; Ohashi, H.; Yamamoto, N.; Kato, D.; Murakami, I.; Fujioka, S.; Nishimura, H.; Nishihara, K. [Department of Physics, Tokyo Metropolitan University, 1-1 Minami-Ohsawa, Hachioji, Tokyo 192-0397 (Japan); National Institute for Fusion Science, 322-6 Oroshi-cho, Toki 509-5292 (Japan); Institute of Laser Engineering, Osaka University, 2-6 Yamada-oka, Suita, Osaka 565-0871 (Japan)

2011-10-15

325

Effect of low energy oxygen ion beam irradiation on ionic conductivity of solid polymer electrolyte  

SciTech Connect

Over the past three decades, solid polymer electrolytes (SPEs) have drawn significant attention of researchers due to their prospective commercial applications in high energy-density batteries, electrochemical sensors and super-capacitors. The optimum conductivity required for such applications is about 10{sup ?2} – 10{sup ?4} S/cm, which is hard to achieve in these systems. It is known that the increase in the concentration of salt in the host polymer results in a continuous increase in the ionic conductivity. However, there is a critical concentration of the salt beyond which the conductivity decreases due to formation of ion pairs with no net charge. In the present study, an attempt is made to identify the concentration at which ion pair formation occurs in PEO: RbBr. We have attempted to modify microstructure of the host polymer matrix by low energy ion (Oxygen ion, O{sup +1} with energy 100 keV) irradiation. Ionic conductivity measurements in these systems were carried out using Impedance Spectroscopy before and after irradiation to different fluencies of the oxygen ion. It is observed that the conductivity increases by one order in magnitude. The increase in ionic conductivity may be attributed to the enhanced segmental motion of the polymer chains. The study reveals the importance of ion irradiation as an effective tool to enhance conductivity in SPEs.

Manjunatha, H., E-mail: gnk-swamy@blr.amrita.edu; Kumaraswamy, G. N., E-mail: gnk-swamy@blr.amrita.edu [Department of Physics, Amrita Vishwa Vidyapeetham, Bengaluru-560035 (India); Damle, R. [Department of Physics, Bangalore University, Bengaluru-560056 (India)

2014-04-24

326

Numerical Study on the Ablation Effects of Tungsten Irradiated by High-intensity Pulsed Ion Beam  

NASA Astrophysics Data System (ADS)

Based on the ion current density model of TEMP type ion beam accelerator, and utilizing the deposited energy of the high-intensity pulsed ion beam (HIPIB) in tungsten by Monte Carlo method as source term, a two-dimensional thermal conduction model controlling the irradiation process was built. The evolution of tungsten temperature during the irradiation period was obtained and analyzed. The results show that the melted thickness of tungsten surface is about 0.3 ?m at shooting center of target irradiated by HIPIB at the end of a pulse under the ion peak current density of 100 A/cm2, the materials of tungsten surface in thickness of about 0.2 ?m reach boiling point; and among the ion peak current density of 50-200 A/cm2, the melting ablation depth is less than 1 ?m according to the calculation. While the ion peak current density increased to about 330 A/cm2, the vaporizing ablation phenomenon appeared on the shooting center of tungsten surface.

Wu, Di; Lei, Mingkai; Zhu, Xiaopeng; Gong, Ye

327

Irradiation effects in rapidly and conventionally solidified alloys. Phase stability in rapidly solidified N i-Nb under Ni ion irradiation  

NASA Technical Reports Server (NTRS)

Two alloy compositions in the Ni-Nb system (Ni60Nb40 and Ni85Nb15) were produced by rapidly quenching from the melt with the piston anvil technique. The Ni60Nb40 was transformed to a metastable, partially crystalline state by heat treatment in a differential scanning calorimeter. The Ni85Nb15 was fully crystalline, with the majority of the grains composed of collections of primary dendrite arms. Both compositions were irradiated with 4 MeV Ni++ ions. The irradiation induced microstructures were examined by transmission electron microscopy and compared with thermally aged samples. The thermal evolution was arrested by ion irradiation in the temperature range studied, by inhibiting the nucleation of the NiNb phase. No irradiation induced voids were observed. It is found that the ion irradiation drives the microstructure along a different path than thermal evolution.

1982-01-01

328

Analysis of charge and mass effects on peroxidase expressions and activities in Arabidopsis thaliana after low-energy ion irradiation.  

PubMed

In order to study the impact of incident ions on organism mutation, positively and negatively charged low-energy oxygen and hydrogen ions were implanted into the dry seeds of Arabidopsis thaliana using three different dosages. The effects of ion irradiation on peroxidase abundance, activity, isozyme patterns, and transcription were analyzed. The results showed that ion irradiation increases peroxidase activity, transcription, and translation. In all analyses, the relative magnitude of effect of the three ions was consistent, with the implantation of O(+) and H(+) affecting peroxidase more than O(-). This finding suggests that the charge of an incident ion influences cellular systems more than its mass. PMID:19815092

Li, Ke; Jiang, Shan; Yu, Haichan; Zhao, Jin; Zhang, Fengshou; Carr, Christopher; Zhang, Jun; Zhang, Genfa

2009-01-01

329

Chemi-luminescence measurements of hyperthermal Xe{sup +}/Xe{sup 2+}+ NH{sub 3} reactions  

SciTech Connect

Luminescence spectra are recorded for the reactions of Xe{sup +}+ NH{sub 3} and Xe{sup 2+}+ NH{sub 3} at energies ranging from 11.5 to 206 eV in the center-of-mass (E{sub cm}) frame. Intense features of the luminescence spectra are attributed to the NH (A {sup 3}{Pi}{sub i}-X {sup 3}{Sigma}{sup -}), hydrogen Balmer series, and Xe I emission observable for both primary ions. Evidence for charge transfer products is only found through Xe I emission for both primary ions and NH{sup +} emission for Xe{sup 2+} primary ions. For both primary ions, the absolute NH (A-X) cross section increases with collision energy before leveling off at a constant value, approximately 9 x 10{sup -18} cm{sup 2}, at about 50 eV while H-{alpha} emission increases linearly with collision energy. The nascent NH (A) populations derived from the spectral analysis are found to be independent of collision energy and have a constant rotational temperature of 4200 K.

Prince, Benjamin D.; Steiner, Colby P. [Air Force Research Laboratory, Space Vehicles Directorate, Kirtland AFB, New Mexico 87117 (United States); Chiu, Yu-Hui [Busek Co. Inc, Natick, Massachusetts 01760 (United States)

2012-04-14

330

Ion irradiation of Fe-Fe oxide core-shell nanocluster films: Effect of interface on stability of magnetic properties  

SciTech Connect

A cluster deposition method was used to produce films of loosely aggregated nanoclusters (NC) of Fe core-Fe3O4 shell or fully oxidized Fe3O4. Films of these NC on Si(100) or MgO(100)/Fe3O4(100) were irradiated to 1016 Si2+/cm2 near room temperature using an ion accelerator. Ion irradiation creates structural change in the NC film with corresponding chemical and magnetic changes which depend on the initial oxidation state of the cluster. Films were characterized using magnetometry (hysteresis, first order reversal curves), microscopy (transmission electron, helium ion), and x-ray diffraction. In all cases, the particle sizes increased due to ion irradiation, and when a core of Fe is present, irradiation reduces the oxide shells to lower valent Fe species. These results show that ion irradiated behavior of the nanocluster films depends strongly on the initial nanostructure and chemistry, but in general saturation magnetization decreases slightly.

McCloy, John S.; Jiang, Weilin; Droubay, Timothy C.; Varga, Tamas; Kovarik, Libor; Sundararajan, Jennifer A.; Kaur, Maninder; Qiang, You; Burks, Edward; Liu, Kai

2013-08-23

331

Antiradiation vaccine: Technology and development of prophylaxis, prevention and treatment of biological consequences from Heavy Ion irradiation  

Microsoft Academic Search

Introduction: An anti-radiation vaccine could be an important part of a countermeasures reg-imen for effective radioprotection, immunoprophylaxis and immunotherapy of the acute radi-ation syndromes (ARS) after gamma-irradiation, neutron irradiation or heavy ion irradiation. Reliable protection of non-neoplastic regions of patients with different forms of cancer which undergo to heavy ion therapy ( e.g. Hadron-therapy) can significantly extend the efficiency of

Dmitri Popov; Vecheslav Maliev

2010-01-01

332

Polymer surfaces graphitization by low-energy He+ ions irradiation  

NASA Astrophysics Data System (ADS)

The electrical and optical properties of surfaces of polyimide and AZ5214e graphitized by low-energy (1 keV) He+ irradiation at different polymer temperatures were investigated. The conductivity of the graphitized layers can be controlled with the irradiation temperature within a broad range and can reach values up to ˜1000 S/cm. We show that the electrical transport in low-conducting samples is governed by thermally activated hopping, while the samples with a high conductivity show a typical semimetallic behavior. The transition from thermally activated to semimetallic conductance governed by the irradiation temperature could also be observed in optical measurements. The semimetallic samples show an unusually high for graphitic materials carrier concentration, which results in a high extinction coefficient in the visible light range. By analyzing the temperature dependence of the conductance of the semimetallic samples, we conclude that the scattering of charge carriers is dominated by Coulomb interactions and can be described by a weak localization model. The transition from a three to two dimensional transport mechanism at low temperatures consistently explains the change in the temperature dependence of the conductance by cooling, observed in experiments.

Geworski, A.; Lazareva, I.; Gieb, K.; Koval, Y.; Müller, P.

2014-08-01

333

Production and evolution of carbonaceous material by ion irradiation in space.  

PubMed

We review recent experimental studies concerning the evolution, driven by ion irradiation, of carbonaceous material from frozen gas to a refractory molecular solid. Under further irradiation the latter changes to a polymer-like material and ultimately to amorphous carbon. Most of the results have been obtained by "in situ" and remote IR and Raman spectroscopy. The results have been applied to demonstrate that molecular solids may be easily formed by irradiation of frozen mantles in dense interstellar clouds. Polymer-like material and amorphous carbons may result by further irradiation of organic mantles on grains in the diffuse interstellar medium. Those grains, during the aggregation to form extended bodies like comets (T-Tau phase of the Sun), are further modified. These latter are also irradiated, after the comet formation, during their long stay in the Oort cloud. In particular it has been suggested that comet may develop an ion-produced cometary organic crust that laboratory evidences show to be stable against temperature increases experienced during passages near the Sun. The comparison between the Raman spectra of some IDP (Interplanetary Dust Particles) and the Raman spectra of some ion-produced amorphous carbons, is also discussed. PMID:11539252

Strazzulla, G; Baratta, G A; Spinella, F

1995-03-01

334

Study of 160 MeV Ni 12+ ion irradiation effects on electrodeposited polypyrrole films  

NASA Astrophysics Data System (ADS)

Conducting polymer polypyrrole thin films doped with LiCF 3SO 3, [CH 3(CH 2) 3] 4NBF 4 and [CH 3(CH 2) 3] 4NPF 6 have been electrodeposited potentiodynamically on ITO coated glass substrate. The polymer films are irradiated with 160 MeV Ni 12+ ions at three different fluences of 5 × 10 10, 5 × 10 11 and 3 × 10 12 ions cm -2. An increase in dc conductivity of polypyrrole films from ˜100 S/cm to ˜170 S/cm after irradiation with highest fluence is observed in four-probe measurement. X-ray diffractogram shows increase in the crystallinity of the polypyrrole films upon SHI irradiation, which goes on increasing with the increase in fluence. Absorption intensity increase in the higher wavelength region is observed in the UV-Vis spectra. The SEM studies show that the cauliflower like flaky microstructure of the surface of polypyrrole films turns globular upon SHI irradiation at fluence 5 × 10 11 ions cm -2 and becomes smooth and dense at the highest fluence used. The cyclic voltammetry studies exhibit that the redox properties of the polypyrrole films do not change much on SHI irradiation.

Hussain, A. M. P.; Kumar, A.; Saikia, D.; Singh, F.; Avasthi, D. K.

2005-12-01

335

The first narrow-band XeCl-excilamp application for complex psoriasis curing  

NASA Astrophysics Data System (ADS)

Clinical efficiency estimation of XeCl-excilamp application for psoriasis curing in comparison with other methods of phototherapy for has been carried out for the first time. Curing psoriasis by XeCl-excilamp assistance is shown to be an effective and present-date method. Such a phototherapy advantages suggested are the good tolerance, and absence of intact skin irradiation. The use of chemicals is no longer relevant, and the total doze of irradiation happens to be rather low.

Dmitruck, Vadim S.; Sosnin, Edward A.; Obgol'tz, Irina A.

2006-05-01

336

Amorphization of -Thorium Phosphate Diphosphate (-TPD) irradiated with high energy krypton ions  

E-print Network

Amorphization of -Thorium Phosphate Diphosphate (-TPD) irradiated with high energy krypton ions C of nuclear wastes, the -Thorium Phosphate Diphosphate ceramic (-TPD), Th4(PO4)4P2O7, must be resistant as good candidates for nuclear waste immobilization [1-3]. Thorium Phosphate-Diphosphate (-TPD), -Th4(PO4

Paris-Sud XI, Université de

337

Mass transport processes initiated in multielemental solids affected by ion beam irradiation  

Microsoft Academic Search

The experimentally observed non-monotonous time dependence of the surface composition initiated by sharp changes in parameters of ion irradiation of multielemental materials are explained on the basis of consideration of preferential sputtering and component interdiffusion. The driving force of the component interdiffusion is the preferential sputtering which forms concentration gradients of components in the near-surface layer. The influence of the

A. Galdikas; C. Templier

1996-01-01

338

Comparison of conductivity produced in polymers and carbon films by pyrolysis and high energy ion irradiation  

Microsoft Academic Search

We compare the effects of pyrolysis and 2 MeV Ar+ ion irradiation in modifying the conductivity of polymeric and carbon films. Chemical degradation (in the polymer films) and structural rearrangement (in both polymer and carbon films) are introduced by either process. Metallic carrier densities (1022 - 1023 cm-3) have been observed in these films by Hall measurements. Transmission electron microscope

T. Venkatesan; R. C. Dynes; B. Wilkens; A. E. White; J. M. Gibson; R. Hamm

1984-01-01

339

Mössbauer study of some ion-beam irradiated Co?Sn electrodeposits  

Microsoft Academic Search

The effect of ion-beam irradiation on the composition and structure of some Co–Sn electrodeposits has been studied by Mössbauer spectroscopy. A transformation of dissolved tin and cubic CoSn to -Co3Sn2 was observed.

A. Vértes; G. Principi; L. M. Gratton; C. Tosello; I. Czakó-Nagy

1985-01-01

340

Structural changes induced by heavy ion irradiation in titanium silicon carbide J.C. Nappa,  

E-print Network

Structural changes induced by heavy ion irradiation in titanium silicon carbide Authors J.C. Nappéa at high temperature. The MAX phases, and more particularly titanium silicon carbide, are distinguished the studied materials, titanium silicon carbide can be distinguished by its propensity to combine

Paris-Sud XI, Université de

341

Analysis of Si crystal irradiated by highly-charged Ar ions using RBS-channeling technique  

NASA Astrophysics Data System (ADS)

An ion-beam is one of the powerful tools applied in nanotechnology and nanoscience. It is expected that the application of highly-charged ion (HCI) beams, which have a higher reactivity in materials, would yield further developments in these fields. For effective applications of HCI beams, it is important to investigate any modifications of irradiated materials from a microscopic point of view. For this purpose, an irradiation-induced defect in a single crystal was analyzed by means of Rutherford backscattering-channeling (RBS) technique. In order to induce defects, Ar 6+ and Ar 9+ beams with an energy of 100 keV were irradiated onto a single crystal of Si. By means of a simple analysis, the depth distribution of disordered Si atoms induced by the irradiation was extracted from the observed RBS-C spectra. The present result implies that the productivity of defects in a Si crystal is enhanced for Ar 9+ ions compared with Ar 6+ ions in a limited region of the surface.

Momota, S.; Nishimura, K.; Nojiri, Y.; Kashihara, M.; Narusawa, T.; Nishiyama, F.

2009-05-01

342

Amorphization and reduction of thermal conductivity in porous silicon by irradiation with swift heavy ions  

SciTech Connect

In this article, we demonstrate that the thermal conductivity of nanostructured porous silicon is reduced by amorphization and also that this amorphous phase in porous silicon can be created by swift (high-energy) heavy ion irradiation. Porous silicon samples with 41%-75% porosity are irradiated with 110 MeV uranium ions at six different fluences. Structural characterisation by micro-Raman spectroscopy and SEM imaging show that swift heavy ion irradiation causes the creation of an amorphous phase in porous Si but without suppressing its porous structure. We demonstrate that the amorphization of porous silicon is caused by electronic-regime interactions, which is the first time such an effect is obtained in crystalline silicon with single-ion species. Furthermore, the impact on the thermal conductivity of porous silicon is studied by micro-Raman spectroscopy and scanning thermal microscopy. The creation of an amorphous phase in porous silicon leads to a reduction of its thermal conductivity, up to a factor of 3 compared to the non-irradiated sample. Therefore, this technique could be used to enhance the thermal insulation properties of porous Si. Finally, we show that this treatment can be combined with pre-oxidation at 300 Degree-Sign C, which is known to lower the thermal conductivity of porous Si, in order to obtain an even greater reduction.

Newby, Pascal J. [Institut des Nanotechnologies de Lyon, Universite de Lyon, INL-UMR5270, CNRS, INSA de Lyon, Villeurbanne 69621 (France); Institut Interdisciplinaire d'Innovation Technologique (3IT), Universite de Sherbrooke, CNRS UMI-LN2, Sherbrooke, Quebec J1K0A5 (Canada); Canut, Bruno; Bluet, Jean-Marie; Lysenko, Vladimir [Institut des Nanotechnologies de Lyon, Universite de Lyon, INL-UMR5270, CNRS, INSA de Lyon, Villeurbanne 69621 (France); Gomes, Severine [Centre de Thermique de Lyon, Universite de Lyon, CETHIL-UMR5008, CNRS, INSA de Lyon, Villeurbanne 69621 (France); Isaiev, Mykola; Burbelo, Roman [Faculty of Physics, Taras Shevchenko National University of Kyiv, 64/13, Volodymyrs'ka St., Kyiv 01601 (Ukraine); Termentzidis, Konstantinos [Laboratoire LEMTA, Universite de Lorraine-CNRS UMR 7563, 54506 Vandoeuvre-les-Nancy cedex (France); Chantrenne, Patrice [Universite de Lyon, INSA de Lyon, MATEIS-UMR CNRS 5510, Villeurbanne 69621 (France); Frechette, Luc G. [Institut Interdisciplinaire d'Innovation Technologique (3IT), Universite de Sherbrooke, CNRS UMI-LN2, Sherbrooke, Quebec J1K0A5 (Canada)

2013-07-07

343

Nanoscale manipulation of Ge nanowires by ion irradiation Lucia Romano,1,a  

E-print Network

Nanoscale manipulation of Ge nanowires by ion irradiation Lucia Romano,1,a Nicholas G. Rudawski,2,b and electromechanical devices. However, in many cases, manipulation and modification of nanowires are required to fully direction. This effect demonstrates the detailed manipulation of nanoscale structures is possible through

Florida, University of

344

Amorphization and reduction of thermal conductivity in porous silicon by irradiation with swift heavy ions  

NASA Astrophysics Data System (ADS)

In this article, we demonstrate that the thermal conductivity of nanostructured porous silicon is reduced by amorphization and also that this amorphous phase in porous silicon can be created by swift (high-energy) heavy ion irradiation. Porous silicon samples with 41%-75% porosity are irradiated with 110 MeV uranium ions at six different fluences. Structural characterisation by micro-Raman spectroscopy and SEM imaging show that swift heavy ion irradiation causes the creation of an amorphous phase in porous Si but without suppressing its porous structure. We demonstrate that the amorphization of porous silicon is caused by electronic-regime interactions, which is the first time such an effect is obtained in crystalline silicon with single-ion species. Furthermore, the impact on the thermal conductivity of porous silicon is studied by micro-Raman spectroscopy and scanning thermal microscopy. The creation of an amorphous phase in porous silicon leads to a reduction of its thermal conductivity, up to a factor of 3 compared to the non-irradiated sample. Therefore, this technique could be used to enhance the thermal insulation properties of porous Si. Finally, we show that this treatment can be combined with pre-oxidation at 300 °C, which is known to lower the thermal conductivity of porous Si, in order to obtain an even greater reduction.

Newby, Pascal J.; Canut, Bruno; Bluet, Jean-Marie; Gomès, Séverine; Isaiev, Mykola; Burbelo, Roman; Termentzidis, Konstantinos; Chantrenne, Patrice; Fréchette, Luc G.; Lysenko, Vladimir

2013-07-01

345

Ion irradiation effects on electric properties of hydrogenated amorphous silicon thin films  

NASA Astrophysics Data System (ADS)

Change in the dominant electronic conduction mechanism of hydrogenated amorphous silicon (a-Si:H) thin films from the band transport to the hopping transport due to ion irradiation is investigated. The change is clarified by the experimental study of electric conductivity of a-Si:H irradiated with energetic protons. Dark electric conductivity (DC) and photoconductivity (PC) variations as a function of 100 keV proton fluence, and variations of temperature dependence of DC due to 100 keV proton irradiation are investigated in detail. As a result, the decrease in DC and PC due to reduction of the band transport is observed at the fluence of less than 1014 cm-2, and the drastic increase in DC and the loss of photoconduction due to enhancement of the hopping transport are observed in the high fluence regime. However, the hopping transport induced by proton irradiation easily disappears at above 300 K and after that, the band transport dominates the electric conduction again. The conductivity based on the band transport after irradiation is not completely restored even after thermal annealing, indicating that thermally stable dangling bonds remain. It is concluded that these electronic transport changes originated from ion irradiation and thermal annealing are caused by the increase or decrease in dangling bond density (localized density of states).

Sato, Shin-ichiro; Ohshima, Takeshi

2013-05-01

346

TEM investigation on the microstructural evolution of Hastelloy N induced by Ar? ion irradiation.  

PubMed

Hastelloy N alloy has been selected as the primary structure material for molten salt reactor. In this article, Hastelloy N alloy samples were irradiated to different doses at room temperature using 300 keV Ar(+) ions. The microstructural evolution was investigated by transmission electron microscopy (TEM) and energy-dispersive spectroscopy (EDS). Black dot defects emerged in sample irradiated at low dose (0.4 displacement per atom (dpa)), and they grew up with irradiation doses (0.4-2 dpa). A high density of small dislocation loops (nano meters in size) were observed in the sample irradiated to 4 dpa. When the ion dose increased to 12 dpa, complicated structures with defects (including dislocation lines, larger loops and smaller black dots) were observed. Dislocation networks were detected from high-angle annular dark field (HAADF) images. Larger dislocation loops (size: 30-80 nm) were visible in the sample irradiated to 40 dpa. Irradiation with dose of 120 dpa led to the formation of face-centered cubic nanocrystallites with preferred orientations. PMID:24285574

Liu, Min; Lu, Yanling; Liu, Renduo; Zhou, Xingtai

2014-02-01

347

Effects of high energy (MeV) ion beam irradiation on polyethylene terephthalate  

NASA Astrophysics Data System (ADS)

Irradiation effects of 50 MeV Li 3+ ion beams in polyethylene terephthalate (PET) films were studied with respect to their structural and electrical properties by using Fourier transform infrared (FTIR) spectroscopy and ac electrical measurement in the frequency range: 50-100 kHz at different temperatures of 30-150 °C. It is found that ac resistivity of PET decreases as frequency increases. The temperature dependencies of dielectric loss tangent exhibit a peak ( Tg) at 60 °C. The capacitance value of irradiated PET is almost temperature independent and ones increases with an increasing of lithium fluence. FTIR spectra show various bands related to C-H, C?O, C-O-C molecular bonds and groups which get modified or break down due to ion beam irradiation.

Singh, Nandlal; Sharma, Anita; Avasthi, D. K.

2003-05-01

348

Annealing effects on the photoluminescence of Pb-ion irradiated He-doped sapphire  

NASA Astrophysics Data System (ADS)

In the present work, the photoluminescence (PL) character of single crystal sapphire (Al2O3) samples with and without implantation by 110 keV He and/or irradiation by 230-MeV Pb ions, as well as subsequently annealing at 600, 900 and 1100 K ( T A) was studied. The modification of the structure and optical properties induced by ion irradiation were analyzed by using PL and FTIR spectra. The PL measurements showed that luminescence peaks located at 390, 413, 450, and 564 nm appeared in irradiated samples. The luminescence peaks appeared at 360, 380, and 516 nm after annealing. Infrared spectra showed a broadening of the absorption band between 460 cm-1 and 510 cm-1, which indicated the formation of strongly damaged regions in the Al2O3 samples. The position shift of the absorption band in 1000-1300 cm-1 tended towards to a higher wavelength.

Song, Yin; Zhang, ChongHong; He, DeYan; Zhang, LiQing; Gou, Jie; Yang, YiTao; Li, JianJian

2012-10-01

349

Effects of heavy ion irradiation on amorphous hydrogenated (diamondlike) carbon films  

NASA Astrophysics Data System (ADS)

Energetic ion-beam irradiation of diamondlike carbon thin films induces a decrease of 5-6 orders of magnitude in the resistivity of the films from their as-grown value of 107 ? cm. Diagnostics used to characterize the nature of the transformation included optical absorption measurements (band gap), Raman spectroscopy (microcrystalline structure), Rutherford backscattering spectroscopy (hydrogen content of the films), and measurements of the temperature dependence of the conductivity (electronic structure). It was found that the initial decrease in resistivity with an increasing ion dose is due to the loss of hydrogen from the films, with a concomitant decrease in the optical band gap. Heating the films during the irradiation greatly accelerates the rate of hydrogen loss as a function of dose. Once the hydrogen removal is complete, further irradiation increases the film conductivity by inducing the growth of microcrystallites of graphite.

Prawer, S.; Kalish, R.; Adel, M.; Richter, V.

1987-05-01

350

1\\/ f noise studies of swift heavy ion irradiated magnetite thin films  

Microsoft Academic Search

The effect of 190MeV 107Ag ion irradiation on antiphase boundaries (APBs) of epitaxial Fe3O4 thin films (thickness ?70nm) grown on MgO (100) oriented substrate has been investigated. The X-ray diffraction shows that at low fluence values upto 5×1011ions\\/cm2, the strain in the films is relaxed whereas at high fluence 1×1012ions\\/cm2, the epitaxial relationship with the substrate is decreasing. The low

M. Wasi Khan; Ravi Kumar; J. P. Srivastava; S. K. Arora; R. J. Choudhary; I. V. Shvets

2008-01-01

351

Characterization of ion-irradiated poly-L-lactic acid using nano-cutting.  

PubMed

Effects on the mechanical strength of poly-L-lactic acid (PLLA) upon irradiation with 150 keV He(+) ion were studied. Changes in the irradiated surface were investigated using a surface texture and contour measuring instrument and an atomic force microscope. Observations made with the atomic force microscope revealed that the irradiated surface subsided significantly as the fluence increased. In order to investigate the dependence on fluence of the depth of the Bragg peak for the ion implantation, the cutting strength, ?, was analysed [F. Saito, I. Nishiyama and T. Hyodo, Mater. Lett., 2012, 66, 144-146]; this value is an indicator of the strength of a material against cutting, and is obtained from the cutting resistance. The averaged ion projected range increased from about 1.1 ?m for a fluence of 1 × 10(15) He(+)/cm(2) to about 4 ?m for a fluence of 1 × 10(16) He(+)/cm(2). The density of the region following irradiation was estimated using a combination of cutting resistance measurements and positron annihilation ? ray Doppler broadening measurements made with an energy-variable positron beam. The density decreased from the value of 1.27 g cm(-3) to about 0.6 g cm(-3) after irradiation with a fluence of 3 × 10(15) He(+)/cm(2). By considering the decrease in the density and the subsidence of the surface, it is concluded that only 30% of the original weight remained in the irradiated region after exposure to the He(+) ions. Anisotropic change in the cutting resistance suggests that mechanical strength in the direction normal to the surface increased while that in the lateral direction decreased. PMID:25380102

Saito, F; Yotoriyama, T; Nishiyama, I; Suzuki, Y; Goto, A; Nagashima, Y; Hyodo, T

2014-12-28

352

Iron ion irradiation increases promotes adhesion of monocytic cells to arterial vascular endothelium  

NASA Astrophysics Data System (ADS)

Radiation causes inflammation, and chronic, low-level vascular inflammation is a risk factor for atherosclerosis. Consistent with this, exposure to radiation from a variety of sources is associated with increased risk of heart disease and stroke. Part of the inflammatory response to radiation is a change in the adhesiveness of the endothelial cells that line the blood vessels, triggering inappropriate accumulation of leukocytes, leading to later, damaging effects of inflammation. Although some studies have been done on the effects of gamma irradiation on vascular endothelium, the response of endothelium to heavy ion radiation likely to be encountered in prolonged space flight has not been determined. We investigated how irradiation of aortic endothelial cells with iron ions affects adhesiveness of cultured aortic endothelial cells for monocytic cells and the consequences of this for development of atherosclerosis. Aortic endothelial cells were irradiated with 600 MeV iron ions at Brookhaven National Laboratory and adhesion-related changes were measured. Cells remained viable for at least 72 hours, and were even able to repair acute damage to cell junctions. We found that iron ion irradiation altered expression levels of specific endothelial cell adhesion molecules. Further, these changes had functional consequences. Using a flow chamber adhesion assay to measure adhesion of monocytic cells to endothelial cells under physiological shear stress, we found that adhesivity of vascular endothelium was enhanced in as little as 24 hours after irradiation. Further, the radiation dose dependence was not monotonic, suggesting that it was not simply the result of endothelial cell damage. We also irradiated aortic arches and carotid arteries of Apolipoprotein-E-deficient mice. Histologic analysis of these mice will be conducted to determine whether effects of radiation on endothelial adhesiveness result in consequences for development of atherosclerosis. (Supported by NSBRI: NCC-9-58-162)

Kucik, Dennis; Khaled, Saman; Gupta, Kiran; Wu, Xing; Yu, Tao; Chang, Polly; Kabarowski, Janusz

353

Morphological change of self-organized protrusions of fluoropolymer surface by ion beam irradiation  

NASA Astrophysics Data System (ADS)

Polytetrafluoroethylene (PTFE) and fluorinated ethylene propylene (FEP) are typical fluoropolymers displaying several desirable technological properties such as electrical insulation and high chemical resistance. When their surfaces are irradiated with ion beams, dense micro-protrusions formed after the emergence and spread of micropores across the entire irradiated area, allowing culture cells to spread on the top of the protrusions. In this study, we investigate the morphological changes introduced in the fluoropolymer surfaces by ion beams as the energy of the beams is increased. When an FEP sample was irradiated with a nitrogen ion beam with an energy of less than 350 keV at 1.0 ?A/cm2, protrusions were formed with a density between 2 × 107/cm2 and 2 × 108/cm2. However, at energies higher than 350 keV, the protrusions became sparse, and the density dropped to 5 × 102/cm2. Protrusions appeared sporadically during irradiation at high energies, and the top of the protrusions appeared as spots inside the sample, which were difficult to etch and became elongated as the erosion of the surface progressed. Erosion was caused by sputtering of FEP molecules and evaporation at notably elevated temperatures on the surface. Analysis based on attenuated total reflectance/Fourier transform infrared spectroscopy showed the presence of Cdbnd C bonds as well as -COOH, -Cdbnd O, and -OH bonds on all irradiated samples. Their concentration on the surface densely covered with micro-protrusions was higher than that on the surface with sparse protrusions after irradiation at energies exceeding 350 keV. Thus, we determined a suitable range for the ion energy for creating FEP surfaces densely covered with protrusions.

Kitamura (Ogawa), Akane; Kobayashi, Tomohiro; Satoh, Takahiro; Koka, Masashi; Kamiya, Tomihiro; Suzuki, Akihiro; Terai, Takayuki

2013-07-01

354

Swift heavy ion irradiation induced enhancement in the antioxidant activity and biocompatibility of polyaniline nanofibers.  

PubMed

Polyaniline (PAni) nanofibers doped with HCl and CSA have been irradiated with 90 MeV O(7+) ions with fluence of 3 x 10(10), 3 x 10(11) and 1 x 10(12) ions cm(-2). TEM micrographs show a decrease in the fiber diameter with increasing irradiation fluence, which has been explained on the basis of the Coulomb explosion model. XRD analysis reveals a decrease in the crystalline domain length and an increase in the strain. The increase in d-spacing for the (100) reflection with increasing irradiation fluence is ascribed to the increase in the tilt angle of the polymer chain, which is also evident from micro-Raman spectra. UV-vis spectra of the PAni nanofibers exhibit blue-shift in the absorption bands attributed to pi-pi* band transitions indicating a reduction in particle size after SHI irradiation; as also observed in TEM micrographs. Micro-Raman spectra also reveal a transition from the benzenoid to quinoid structures in the PAni chain as the fluence is increased. Although the quinoid unit has no hydrogen for DPPH scavenging, the antioxidant activity of PAni nanofibers is found to increase with increasing fluence. This has been attributed to the availability of more reaction sites as a result of fragmentation of the PAni nanofibers which compensates for the benzenoid to quinoid transition after irradiation. The biocompatibility of the PAni nanofibers is also found to increase with increasing irradiation fluence, indicating the possibility of employing swift heavy ion irradiation as an effective technique in order to modify conducting polymer nanostructures for biomedical applications. PMID:20357408

Kumar, A; Banerjee, Somik; Saikia, Jyoti P; Konwar, B K

2010-04-30

355

Formation of ion-irradiation-induced atomic-scale defects on walls of carbon nanotubes A. V. Krasheninnikov,1,2  

E-print Network

Formation of ion-irradiation-induced atomic-scale defects on walls of carbon nanotubes A. V Recent experiments on irradiated carbon nanotubes provide evidence that ion bombardment gives rise tunneling microscopy STM images of irradiated nanotubes. We demonstrate that irradiation-induced defects may

Krasheninnikov, Arkady V.

356

In situ creep measurements on micropillar samples during heavy ion irradiation  

NASA Astrophysics Data System (ADS)

We report on the development of an in situ micropillar compression apparatus capable of measuring creep under heavy ion beam irradiation. The apparatus has a force resolution of 1 ?N and a displacement resolution of 1 nm. The experimental setup consists of a nanopositioner, a laser displacement sensor, and a microfabricated doubly clamped silicon-beam transducer. The system was tested by measuring the creep rate of amorphous Cu56Ti38Ag6 micropillars as a function of applied stress during room temperature irradiation with 2.1 MeV Ne+. Measured values of the irradiation induced fluidity are in the range 0.5-3 dpa-1 GPa-1, and in good agreement with values obtained by stress relaxation experiments on other metallic glasses, and with predictions of molecular dynamics simulations. The in situ apparatus provides a practical approach for accelerated evaluation of irradiation induced creep in promising nuclear materials.

Özerinç, Sezer; Averback, Robert S.; King, William P.

2014-08-01

357

Formation and evolution of ripples on ion-irradiated semiconductor surfaces  

SciTech Connect

We have examined the formation and evolution of ripples on focused-ion-beam (FIB) irradiated compound semiconductor surfaces. Using initially normal-incidence Ga{sup +} FIB irradiation of InSb, we tuned the local beam incidence angle (?{sub eff}) by varying the pitch and/or dwell time. For single-pass FIB irradiation, increasing ?{sub eff} induces morphological evolution from pits and islands to ripples to featureless surfaces. Multiple-pass FIB irradiation of the rippled surfaces at a fixed ?{sub eff} leads to island formation on the ripple crests, followed by nanorod (NR) growth. This ripple-NR transition provides an alternative approach for achieving dense arrays of NRs.

Kang, M.; Wu, J. H.; Ye, W.; Jiang, Y.; Robb, E. A.; Chen, C.; Goldman, R. S., E-mail: rsgold@umich.edu [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States)

2014-02-03

358

Inactivation, DNA double strand break induction and their rejoining in bacterial cells irradiated with heavy ions  

NASA Technical Reports Server (NTRS)

Besides inactivation one of the major interests in our experiments is to study the primary damage in the DNA double strand breaks (DSB) after heavy ion irradiation. These damages lead not only to cell death but also under repair activities to mutations. In further experiments we have investigated the inactivation with two different strains of Deinococcus radiodurans (R1, Rec 30) and the induction of DSB as well as the rejoining of DSB in stationary cells of E. coli (strain B/r) irradiated with radiations of different quality. In the latter case irradiations were done so that the cell survival was roughly at the same level. We measured the DSB using the pulse field gelelectrophoresis which allows to separate between intact (circular) and damaged (linear) DNA. The irradiated cells were transferred to NB medium and incubated for different times to allow rejoining.

Schaefer, M.; Zimmermann, H.; Schmitz, C.

1994-01-01

359

Inactivation, DNA double strand break induction and their rejoining in bacterial cells irradiated with heavy ions  

SciTech Connect

Besides inactivation one of the major interests in the authors experiments is to study the primary damage in the DNA double strand breaks (DSB) after heavy ion irradiation. These damages lead not only to cell death but also under repair activities to mutations. In further experiments they have investigated the inactivation with two different strains of Deinococcus radiodurans (R1, Rec 30) and the induction of DSB as well as the rejoining of DSB in stationary cells of E. coli (strain B/r) irradiated with radiations of different quality. In the latter case irradiations were done so that the cell survival was roughly at the same level. The authors measured the DSB using the pulse field gelelectrophoresis which allows to separate between intact (circular) and damaged (linear) DNA. The irradiated cells were transferred to NB medium and incubated for different times to allow rejoining.

Schaefer, M.; Zimmermann, H.; Schmitz, C.

1994-12-31

360

Uniaxial in-plane magnetic anisotropy of a CoPt thin film induced by ion irradiation  

Microsoft Academic Search

The mechanism for ion-induced uniaxial magnetic anisotropy of ferromagnetic CoPt thin films is investigated using x-ray diffraction and soft x-ray emission spectroscopy. When Co\\/Pt multilayers 64 nm thick are irradiated with 80 keV Ar+ ions in an externally applied magnetic field, the magnetization of the ion-irradiated area shows a significant anisotropic angular dispersion in its hysteresis. Analysis of x-ray diffraction

G. S. Chang; A. Moewes; S. H. Kim; J. Lee; K. Jeong; C. N. Whang; D. H. Kim; S.-C. Shin

2006-01-01

361

Amorphization and recrystallization of single-crystalline hydrogen titanate nanowires by N{sup +} ion irradiation  

SciTech Connect

We report on the phase transformation of hydrogen titanate (H{sub 2}Ti{sub 3}O{sub 7}) nanowires induced by 50?keV N{sup +} ion irradiation at room temperature with fluences of 1?×?10{sup 15} ions/cm{sup 2} and 1?×?10{sup 16} ions/cm{sup 2}, respectively. Using transmission electron microscopy, the internal structure of the ion irradiated nanowires is analyzed. At low fluence, a transformation from crystalline H{sub 2}Ti{sub 3}O{sub 7} to amorphous TiO{sub 2} is observed. However, at higher fluence, a remarkable crystalline-amorphous TiO{sub 2} core-shell structure is formed. At this higher fluence, the recrystallization occurs in the core of the nanowire and the outer layer remains amorphous. The phase transformation and formation of core-shell structure are explained using the thermal spike model, radiation enhanced diffusion, and classical theory of nucleation and growth under non-equilibrium thermodynamics. X-ray photoelectron spectroscopy and Raman scattering reveal further insight into the structure of the nanowires before and after ion irradiation.

Behera, Akshaya K.; Bandyopadyay, Malay K.; Chatterjee, Shyamal, E-mail: shyamal@iitbbs.ac.in [School of Basic Sciences, Indian Institute of Technology Bhubaneswar, Bhubaneswar 751007 (India); Facsko, Stefan [Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden (Germany); Das, Siddhartha [Department of Metallurgical and Materials Engineering, Indian Institute of Technology Kharagpur, Kharagpur 721302 (India)

2014-06-21

362

fcc-hcp phase transformation in Co nanoparticles induced by swift heavy-ion irradiation  

SciTech Connect

We demonstrate a face-centered cubic (fcc) to hexagonally close-packed (hcp) phase transformation in spherical Co nanoparticles achieved via swift heavy-ion irradiation. Co nanoparticles of mean diameter 13.2 nm and fcc phase were first formed in amorphous SiO{sub 2} by ion implantation and thermal annealing and then irradiated at room temperature with 9-185 MeV Au ions. The crystallographic phase was identified with x-ray absorption spectroscopy and electron diffraction and quantified, as functions of the irradiation energy and fluence, with the former. The transformation was complete at low fluence prior to any change in nanoparticle shape or size and was governed by electronic stopping. A direct-impact mechanism was identified with the transformation interaction cross-section correlated with that of a molten ion track in amorphous SiO{sub 2}. We suggest the shear stress resulting from the rapid thermal expansion about an ion track in amorphous SiO{sub 2} was sufficient to initiate the fcc-to-hcp phase transformation in the Co nanoparticles.

Sprouster, D. J.; Giulian, R.; Schnohr, C. S.; Araujo, L. L.; Kluth, P.; Byrne, A. P.; Foran, G. J.; Johannessen, B.; Ridgway, M. C. [Department of Electronic Materials Engineering, Research School of Physics and Engineering, Australian National University, Canberra, Australian Capital Territory 0200 (Australia); Department of Physics, Faculty of Science, Australian National University, Canberra, Australian Capital Territory 0200 (Australia); Australian Nuclear Science and Technology Organization, Menai, New South Wales 2234 (Australia); Department of Electronic Materials Engineering, Research School of Physics and Engineering, Australian National University, Canberra, Australian Capital Territory 0200 (Australia)

2009-09-15

363

Amorphization and recrystallization of single-crystalline hydrogen titanate nanowires by N+ ion irradiation  

NASA Astrophysics Data System (ADS)

We report on the phase transformation of hydrogen titanate (H2Ti3O7) nanowires induced by 50 keV N+ ion irradiation at room temperature with fluences of 1 × 1015 ions/cm2 and 1 × 1016 ions/cm2, respectively. Using transmission electron microscopy, the internal structure of the ion irradiated nanowires is analyzed. At low fluence, a transformation from crystalline H2Ti3O7 to amorphous TiO2 is observed. However, at higher fluence, a remarkable crystalline-amorphous TiO2 core-shell structure is formed. At this higher fluence, the recrystallization occurs in the core of the nanowire and the outer layer remains amorphous. The phase transformation and formation of core-shell structure are explained using the thermal spike model, radiation enhanced diffusion, and classical theory of nucleation and growth under non-equilibrium thermodynamics. X-ray photoelectron spectroscopy and Raman scattering reveal further insight into the structure of the nanowires before and after ion irradiation.

Behera, Akshaya K.; Facsko, Stefan; Bandyopadyay, Malay K.; Das, Siddhartha; Chatterjee, Shyamal

2014-06-01

364

In situ luminescence as monitor of radiation damage under swift heavy ion irradiation  

NASA Astrophysics Data System (ADS)

In this paper, we discuss the results of recent ionoluminescence experiments concerning the study of radiation dose effects in ?-Al 2O 3, ?-Al 2O 3:Cr and LiF crystals under the irradiation with different swift heavy ions in a wide range of nuclear and electronic stopping powers. To monitor the lattice disorder in alumina and lithium fluoride, the luminescence of F-type centres have been used. It was shown that the degradation stage of the F + centre luminescence signal under 710 MeV Bi ion irradiation begins at a very low damage level and cannot be induced by defects produced by elastic collisions. The observed difference in the evolution of F3+-centre luminescence in LiF by swift heavy ions and conventional radiation is ascribed to the high local concentration of defects in the ion-track region. In experiments with ruby, we explored a well-known piezospectroscopic method for in situ monitoring of the build up and accumulation of mechanical stress under the irradiation with high-energy heavy ion. The obtained data strongly imply that the lattice disorder induced by collective electronic excitations plays a dominant role in generation of mechanical stress in the studied fluence range.

Skuratov, V. A.; Gun, Kim Jong; Stano, J.; Zagorski, D. L.

2006-04-01

365

Visualising discrete structural transformations in germanium nanowires during ion beam irradiation and subsequent annealing.  

PubMed

In this article we detail the application of electron microscopy to visualise discrete structural transitions incurring in single crystalline Ge nanowires upon Ga-ion irradiation and subsequent thermal annealing. Sequences of images for nanowires of varying diameters subjected to an incremental increase of the Ga-ion dose were obtained. Intricate transformations dictated by a nanowire's geometry indicate unusual distribution of the cascade recoils in the nanowire volume, in comparison to planar substrates. Following irradiation, the same nanowires were annealed in the TEM and corresponding crystal recovery followed in situ. Visualising the recrystallisation process, we establish that full recovery of defect-free nanowires is difficult to obtain due to defect nucleation and growth. Our findings will have large implications in designing ion beam doping of Ge nanowires for electronic devices but also for other devices that use single crystalline nanostructured Ge materials such as thin membranes, nanoparticles and nanorods. PMID:25231220

Kelly, Roisin A; Holmes, Justin D; Petkov, Nikolay

2014-11-01

366

Magnetic stability of He+ ion irradiated FeO+Fe3N granular films  

SciTech Connect

Ion irradiation effects on the magnetic properties of FeO/Fe3N (Iron oxide/Iron Nitride) nanoparticles are investigated in this study. The FeO/Fe3N nanoparticles were prepared using a nanocluster deposition system. The x-ray diffraction data confirms the presence of FeO and Fe3N compounds in the prepared nanoparticles. The saturation magnetization (30 emu/g), coercivity (87.9 Oe) and remanence (3.2 emu/g) of these nanoparticles remain unaltered after irradiation with 2 MeV He+ ions to a fluence of 3E15 ions/cm2 at room temperature, indicating that the magnetic properties of these nanoparticles are not affected in a highly radioactive environment. This unique property of the magnetic stability may provide promising applications for advanced data storage.

Sundararajan, J. A.; Zhang, Dongtao; Qiang, You; Jiang, Weilin; McCloy, John S.

2011-04-01

367

Ion irradiation-induced phase transformation mechanisms in Y2O3 thin films  

NASA Astrophysics Data System (ADS)

This work studies the ion irradiation-induced phase transformations in thin films of yttrium oxide. The films were deposited using an ion beam sputtering technique that allows the control of the order/disorder of the microstructure. As-deposited (disordered) and annealed (ordered) samples were irradiated by xenon ions at different energies and doses. Two different structural phase transformations were observed: cubic/amorphous-like and cubic/monoclinic. In both cases, it is shown that the pristine structure is of prime importance in the transformation process. The phase transformations are analysed in terms of structural extended defect nucleation originating from the oxygen network behaviour, which leads to polygonisation up to a nanocrystallite-like structure, followed by a phase transformation into a monoclinic structure.

Gaboriaud, R. J.; Paumier, F.; Jublot, M.; Lacroix, B.

2013-09-01

368

Mechanisms of nanorod growth on focused-ion-beam-irradiated semiconductor surfaces: Role of redeposition  

SciTech Connect

We have examined the formation and evolution of irradiation-induced nanorod (NR) growth through a comparison of focused-ion-beam irradiation of InSb wafers and InSb/GaAs heterostructures. Above a critical ion dose, cone-shaped NRs capped with In islands form on both InSb surfaces. For InSb wafers, the NR base diameter increases with ion energy. In the case of InSb/GaAs heterostructures, as the milled depth approaches the InSb/GaAs interface, the cone-shaped NRs transition to capless NRs with a truncated cone shape. These results suggest a growth mechanism in which both the NR cap and body are supplied by redeposition of atoms sputtered from InSb.

Wu, J. H.; Goldman, R. S.

2012-01-30

369

Plastic flow induced by single ion impacts on gold  

SciTech Connect

In situ TEM was used to follow RT irradiation of thinned bulk and 62nm thick gold films with Xe ions at 50-400 keV. Energy spikes from single ion impacts give rise to surface craters and holes which exist until annihilated by subsequent ion impacts. Video recording provided details with a time resolution of 33 ms. Craters were produced on the irradiated surface at all ion energies and on the opposite surface when the ions had enough energy to traverse the specimen. Crater sizes were as large as 12nm for the higher energy irradiations. On average, about 6% of impinging ions result in craters. A single 200 keV Xe ion may produce a hole in thin gold foils. Hole formation involves the movement by plastic flow of massive amounts of material, on the order of tens of thousand Au atoms per ion impact. Individual ion impacts also result in a filling of both holes and craters as well as a thickening of the gold foil. Change in morphology during irradiation is attributed to a localized, thermal-spike induced melting, coupled with plastic flow under the influence of surface forces.

Birtcher, R.C. [Argonne National Lab., IL (United States). Materials Science Div.; Donnelly, S.E. [Salford Univ. (United Kingdom). Joule Physics Lab.

1996-12-01

370

Modeling of the DBD in Xe-Cl2 mixtures: effect of chlorine concentration and pressure  

NASA Astrophysics Data System (ADS)

Characteristics of the DBD in Xe-Cl2 mixtures were simulated using the 1D fluid model at gas pressure 150-300 Tor and chlorine concentration in the mixtures 0.1- 5%. The discharge gap is fixed at 4 mm. Two dielectric layers have an identical thickness 2 mm and relative permittivity 4. The source voltage US=U0sin?t with f=100 kHz and U0=4.25 or 5 kV is applied to the electrodes. Simulations show at all chlorine concentrations in the Xe-Cl2 mixtures the most abundant negative species in the discharge are Cl^- ions, the most abundant positive ions are Xe2^+. At the current pulse densities of electrons and Xe^+ ions near the dielectric barrier sharply increases. The potential drop across the discharge gap increases and the magnitude of the current pulse falls with chlorine content in the mixture. Power deposited into heating of positive and negative ions grows with chlorine concentration; power deposited into electrons mainly decreases with chlorine concentration. Growth of the chlorine content in Xe-Cl2 mixtures results in increase of electron energy expenses on Cl2 dissociation, Xe and Cl2 ionization, and Cl2^* and Xe^** excitation. At chlorine concentration higher than 0.1% emission of the XeCl^* 308 nm band predominates in radiation flux. The DBD radiative efficiency decreases with pressure and has maximum at small chlorine concentration.

Avtaeva, Svetlana; Saghi, Belkacem; Rahmani, Bouabdellah

2012-10-01

371

Structural Changes Induced by Low-Flux Ion Irradiation in a Ni4Mo Alloy  

NASA Astrophysics Data System (ADS)

Irradiation induced random displacements of atoms and replacement collision sequences are possible mechanisms for phase transformations as well as other physical properties changes as grain size variation and hardness increase or decrease. In this study Ni4Mo alloy samples were subject to low-flux bombardment by ion beams. This alloy has similar structure to the Hastelloy-C used in industry and to U3Si that is used as nuclear fuel. Sample regions were irradiated while the energy density of the bombarding beams was carefully controlled and the non-irradiated regions were kept close to room temperature. This way the irradiation induced temperature increase was highly localized creating "quench-like" conditions. After the irradiation, the samples were annealed at low temperature. Due to irradiation conditions there was a high density of nucleation sites favoring the formation of finer grain structures as well as localized phase transformations. The results showed that with the appropriate fluence and post-irradiation treatment, a coarse grained specimen can be forced to re-crystallize with a smaller grain size and manifest a specific change in hardening values due mainly to an order-disorder transformation [1,2].

Toader, O. F.; Naab, F.; Ari-Gur, P.; Kimmel, G.

2009-03-01

372

Temporal evolution of nanoporous layer in off-normally ion irradiated GaSb  

SciTech Connect

Room temperature irradiation of GaSb by 60?keV Ar{sup +}-ions at an oblique incidence of 60° leads to simultaneous formation of a nanoporous layer and undulations at the interface with the underlying substrate. Interestingly, with increasing ion fluence, a gradual embedding of the dense nanoporous layer takes place below ridge-like structures (up to the fluence of 1?×?10{sup 17} ions cm{sup ?2}), which get extended to form a continuous layer (at fluences ?4?×?10{sup 17} ions cm{sup ?2}). Systematic compositional analyses reveal the co-existence of Ga{sub 2}O{sub 3} and Sb{sub 2}O{sub 3} in the surface layer. The results are discussed in terms of a competition between ion-induced defect accumulation and re-deposition of sputtered atoms on the surface.

Datta, D. P.; Garg, S. K.; Som, T., E-mail: tsom@iopb.res.in [SUNAG Laboratory, Institute of Physics, Bhubaneswar 751 005, Odisha (India); Kanjilal, A. [Department of Physics, School of Natural Sciences, Shiv Nadar University, Gautam Budh Nagar, Uttar Pradesh 203 207 (India); Sahoo, P. K. [School of Physical Sciences, National Institute of Science Education and Research, Bhubaneswar 751 005, Odisha (India); Kanjilal, D. [Inter-University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110 067 (India)

2014-03-28

373

Visualising discrete structural transformations in germanium nanowires during ion beam irradiation and subsequent annealing  

NASA Astrophysics Data System (ADS)

In this article we detail the application of electron microscopy to visualise discrete structural transitions incurring in single crystalline Ge nanowires upon Ga-ion irradiation and subsequent thermal annealing. Sequences of images for nanowires of varying diameters subjected to an incremental increase of the Ga-ion dose were obtained. Intricate transformations dictated by a nanowire's geometry indicate unusual distribution of the cascade recoils in the nanowire volume, in comparison to planar substrates. Following irradiation, the same nanowires were annealed in the TEM and corresponding crystal recovery followed in situ. Visualising the recrystallisation process, we establish that full recovery of defect-free nanowires is difficult to obtain due to defect nucleation and growth. Our findings will have large implications in designing ion beam doping of Ge nanowires for electronic devices but also for other devices that use single crystalline nanostructured Ge materials such as thin membranes, nanoparticles and nanorods.In this article we detail the application of electron microscopy to visualise discrete structural transitions incurring in single crystalline Ge nanowires upon Ga-ion irradiation and subsequent thermal annealing. Sequences of images for nanowires of varying diameters subjected to an incremental increase of the Ga-ion dose were obtained. Intricate transformations dictated by a nanowire's geometry indicate unusual distribution of the cascade recoils in the nanowire volume, in comparison to planar substrates. Following irradiation, the same nanowires were annealed in the TEM and corresponding crystal recovery followed in situ. Visualising the recrystallisation process, we establish that full recovery of defect-free nanowires is difficult to obtain due to defect nucleation and growth. Our findings will have large implications in designing ion beam doping of Ge nanowires for electronic devices but also for other devices that use single crystalline nanostructured Ge materials such as thin membranes, nanoparticles and nanorods. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr04513k

Kelly, Roisin A.; Holmes, Justin D.; Petkov, Nikolay

2014-10-01

374

Magnetic Texturing of Xenon-Irradiated Iron Films Studied by Magnetic Orientation Mössbauer Spectroscopy  

NASA Astrophysics Data System (ADS)

Modifications of magnetic properties upon heavy-ion irradiation have been recently investigated for films of ferromagnetic 3d-elements (Fe, Ni, Co) and alloys (permendur, permalloy), in relation to changes of their microstructure. Here we report on Xe-ion irradiation of a highly textured iron film prepared via pulsed-laser deposition on a MgO(100) single crystal and containing a thin 57Fe marker layer for magnetic orientation Mössbauer spectroscopy (MOMS). We compare the results with those obtained for a polycrystalline Fe/Si(100) sample produced by electron evaporation and premagnetized before Xe-irradiation in a 300 Oe external field. Characterization of the samples also included magneto-optical Kerr effect (MOKE), Rutherford backscattering spectroscopy (RBS) and X-ray diffraction (XRD).

Müller, G. A.; Lieb, K. P.; Carpene, E.; Zhang, K.; Schaaf, P.; Faupel, J.; Krebs, H. U.

2004-11-01

375

Effects of high energy Au-ion irradiation on the microstructure of diamond films  

SciTech Connect

The effects of 2.245 GeV Au-ion irradiation and subsequent annealing processes on the evolution of microstructure of diamond films with microcrystalline (MCD) or ultra-nanocrystalline (UNCD) granular structure were investigated, using near edge x-ray absorption fine structure and electron energy loss spectroscopy in transmission electron microscopy. For MCD films, the Au-ion irradiation disintegrated some of the diamond grains, resulting in the formation of nano-sized carbon clusters embedded in a matrix of amorphous carbon (a-C). The annealing process recrystallized the diamond grains and converted the a-C into nano-sized graphite particulates and, at the same time, induced the formation of nano-sized i-carbon clusters, the bcc structured carbon with a{sub 0} = 0.432 nm. In contrast, for UNCD films, the Au-ion irradiation transformed the grain boundary phase into nano-sized graphite, but insignificantly altered the crystallinity of the grains of the UNCD films. The annealing process recrystallized the materials. In some of the regions, the residual a-C phases were transformed into nano-sized graphites, whereas in other regions i-carbon nanoclusters were formed. The difference in irradiation-induced microstructural transformation behavior between the MCD and the UNCD films is ascribed to the different granular structures of the two types of films.

Chen, Shih-Show [Department of Physics, Tamkang University, Tamsui, New-Taipei 251, Taiwan (China); Department of Information Technology and Mobile Communication, Taipei College of Maritime Technology, Tamsui, New-Taipei 251, Taiwan (China); Chen, Huang-Chin [Department of Physics, Tamkang University, Tamsui, New-Taipei 251, Taiwan (China); Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 300, Taiwan (China); Wang, Wei-Cheng; Lin, I-Nan; Chang, Ching-Lin [Department of Physics, Tamkang University, Tamsui, New-Taipei 251, Taiwan (China); Lee, Chi-Young [Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 300, Taiwan (China); Guo Jinghua [Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

2013-03-21

376

Radiation damage effects in cubic-stabilized zirconia irradiated with 72 MeV I + ions  

NASA Astrophysics Data System (ADS)

Cubic-stabilized zirconia single crystals were irradiated using 72 MeV I + ions in the TASSC accelerator facility at Chalk River Laboratory (to simulate a typical U or Pu fission fragment). Irradiations were performed over the fluence range 1 × 10 18-5 × 10 19 ions/m 2, at temperatures of 300, 770, and 1170 K. Damage accumulation was monitored using Rutherford Backscattering Spectroscopy and ion-channeling (RBS/C) techniques. At ambient temperature and at the highest I + fluence used in these experiments (5 × 10 19 I +/m 2), RBS/C measurements revealed a rather high degree of lattice disorder. Specifically, the dechanneling parameter ?min varied from 80% to greater than 90% over the depth probed by RBS/C (˜1 ?m). Nano-indentation measurements on the same sample indicated decreases in elastic modulus, E, and hardness, H (both by about 9%). These results suggest that an alteration in structure beyond simple defect accumulation occurs under these irradiation conditions. However, transmission electronmicroscopy (TEM) observations and in particular microdiffraction measurements failed to reveal any structural transformations in the irradiated material.

Sickafus, Kurt E.; Matzke, Hansjoachim; Yasuda, Kazuhiro; Chodak, Paul, III; Verrall, Richard A.; Lucuta, Petru G.; Andrews, H. Robert; Turos, Andrzej; Fromknecht, Rainer; Baker, Neil P.

1998-05-01

377

Microstructure evolution and hardness change in ordered Ni3V intermetallic alloy by energetic ion irradiation  

NASA Astrophysics Data System (ADS)

Ni3V bulk intermetallic compounds with ordered D022 structure were irradiated with 16 MeV Au ions at room temperature. The irradiation induced phase transformation was examined by means of the transmission electron microscope (TEM), the extended X-ray absorption fine structure measurement (EXAFS) and the X-ray diffraction (XRD). We also measured the Vickers hardness for unirradiated and irradiated specimens. The TEM observation shows that by the Au irradiation, the lamellar microstructures and the super lattice spot in diffraction pattern for the unirradiated specimen disappeared. This TEM result as well as the result of XRD and EXAFS measurements means that the intrinsic D022 structure of Ni3V changes into the A1 (fcc) structure which is the lattice structure just below the melting point in the thermal equilibrium phase diagram. The lattice structure change from D022 to A1 (fcc) accompanies a remarkable decrease in Vickers microhardness. The change in crystal structure was discussed in terms of the thermal spike and the sequential atomic displacements induced by the energetic heavy ion irradiation.

Hashimoto, A.; Kaneno, Y.; Semboshi, S.; Yoshizaki, H.; Saitoh, Y.; Okamoto, Y.; Iwase, A.

2014-11-01

378

Amorphization kinetics of Zr(Cr,Fe){sub 2} under ion irradiation  

SciTech Connect

Thin foils of Zircaloy-4 were irradiated with 350 KeV {sup 40}Ar ions in the dual ion beam/HVEM facility at Argonne National Laboratory at 300--650 K. The irradiation-induced amorphization of the intermetallic precipitates Zr (Cr; Fe){sub 2} and Zr{sub 2} (Ni, Fe) was studied in-situ. For Zr (Cr, Fe){sub 2} precipitates the dose-to-amorphization was found to increase exponentially with temperature, with a critical temperature of about 650 K. The amorphization morphology was shown to be homogeneous, with no preferential site for nucleation, in contrast to neutron-irradiation amorphization which started at the precipitate-matrix interface. For Zr{sub 2} (Ni,Fe) precipitates it was found that amorphization occurred at 550 and 600 K, whereas in neutron irradiation no amorphization has been observed at those temperatures. The results are discussed in context of previous neutron and electron irradiations and likely amorphization mechanisms are proposed.

Motta, A.T. [Pennsylvania State Univ., University Park, PA (United States). Dept. of Nuclear Engineering; Howe, L.M. [Atomic Energy of Canada Ltd., Chalk River, ON (Canada). Chalk River Labs.; Okamoto, P.R. [Argonne National Lab., IL (United States)

1992-12-01

379

Microstructure and Mechanical Properties of Ti3SiC2 Irradiated by Carbon Ions  

NASA Astrophysics Data System (ADS)

Thanks to its noteworthy mechanical properties, excellent damage tolerance and good thermal stability, the Ti3SiC2 ternary compound has attracted great concern and has been considered as a potential structural component material for the 4th generation of reactors (e.g., gas fast nuclear reactors) and future fusion reactors. The outstanding properties are due to the nanolamellar structure which imparts characteristics of both metals and ceramics to this material. In our work, Ti3SiC2 samples have been irradiated by C+ ions with a high fluence of 1.78 × 1017 ions/cm2 at a range of temperatures from 120°C-850°C. Subsequently, series of characterization techniques including synchrotron irradiation x-ray diffraction, scanning electron microscopy and nano-indentation are carried out to understand the changes of microstructure and mechanical properties. The composition exhibits high damage tolerant properties and a high recovery rate through the analysis, especially at high temperature. The minimum damage to an irradiated sample appears around 350°C in the temperature range 120°C-550°C. At a high irradiation temperature, a significant reduction in the damage can be achieved and an almost complete lack of damage compared with an un-irradiated sample is revealed at the temperature of 850°C.

Wang, Kun; Qi, Qiang; Cheng, Gui-Jun; Shi, Li-Qun

2014-07-01

380

Microstructure evolution and degradation mechanisms of reactor internal steel irradiated with heavy ions  

NASA Astrophysics Data System (ADS)

Structure evolution and degradation mechanisms during irradiation of 18Cr-10Ni-Ti steel (material of VVER-1000 reactor internals are investigated). Using accelerator irradiations with Cr 3+ and Ar + ions allowed studying effects of dose rate, different initial structure state and implanted ions on features of structure evolution and main mechanisms of degradation including low temperature swelling and embrittlement of the 18Cr-10Ni-Ti steel. It is shown that differences in dose rate at most irradiation temperatures mainly exert their influence on the duration of the swelling transient regime. Calculations of possible transmutation products during irradiation of this steel in a VVER-1000 spectrum were performed. It is shown that gaseous atoms (He and H), which are generated simultaneously with radiation defects, stabilize the elements of radiation microstructure and influence the swelling. The nature of deformation under different temperatures of irradiation and of mechanical testing is investigated. It is shown that the temperature sensitivity of swelling behaviour in the investigated steel, with different initial structures can be connected with the dynamic behaviour of point defect sinks.

Borodin, O. V.; Bryk, V. V.; Kalchenko, A. S.; Parkhomenko, A. A.; Shilyaev, B. A.; Tolstolutskaya, G. D.; Voyevodin, V. N.

2009-03-01

381

Detection of chromosomal instability in bystander cells after Si490-ion irradiation.  

PubMed

There is increasing evidence that two of the biological effects associated with low-dose ionizing radiation, genomic instability and bystander responses, may be linked. To verify and validate the link between the two phenomena, the ability of Si490 ions (high-energy particles associated with radiation risk in space) to induce bystander responses and chromosomal instability in human bronchial epithelial (HBEC-3kt) cells was investigated. These studies were conducted at both the population and single cell level in irradiated and nonirradiated bystander cells receiving medium from the irradiated cultures. At the general population level, transfer of medium from silicon-ion (Si490)-irradiated cultures (at doses of 0.073 Gy, 1.2 Gy and 2 Gy) to nonirradiated bystander cells resulted in small increases in the levels of chromosomal aberrations at the first division. Subsequently, single cell clones isolated from irradiated and bystander populations were analyzed for the appearance of de novo chromosome-type aberrations after ?50 population doublings using mFISH. Both irradiated and bystander clones demonstrated chromosomal instability (as seen by the de novo appearance of translocations and chromosomal fragments), albeit to different degrees, whereas sham-treated controls showed relatively stable chromosomal patterns. The results presented here highlight the importance of nontargeted effects of radiation on chromosomal instability in human epithelial cells and their potential relevance to human health. PMID:21718104

Ponnaiya, Brian; Suzuki, Masao; Tsuruoka, Chirzuru; Uchihori, Yukio; Wei, Ying; Hei, Tom K

2011-09-01

382

Laboratory studies of electron and ion irradiation of solid acetonitrile (CH?CN).  

PubMed

The structure and bonding of solid acetonitrile (CH?CN) films on amorphous silica are studied, and chemical and physical processes under irradiation with 200 keV protons and 250-400 eV electrons are quantified using transmission infrared spectroscopy, reflection-absorption infrared spectroscopy and temperature-programmed desorption, with the assistance of basic computational chemistry and nuclear materials calculations. The thermal desorption profiles are found to depend strongly on the balance between CH?CN-surface and CH?CN-CH?CN interactions, passing from a sub-monolayer regime (binding energy: 35-50 kJ mol?¹) to a multilayer regime (binding energy: 38.2±1.0 kJ mol?¹) via a fractional order desorption regime characteristic of islanding as the coverage increases. Calculations using the SRIM code reveal that the effects of the ion irradiation are dominated by electronic stopping of incident protons, and the subsequent generation of secondary electrons. Therefore, ion irradiation and electron irradiation experiments can be quantitatively compared. During ion irradiation of thicker CH?CN films, a cross section for secondary electron-promoted chemical destruction of CH3CN of 4 (±1) × 10?¹? cm² was measured, while electron-promoted desorption was not detected. A significantly higher cross section for electron-promoted desorption of 0.82-3.2 × 10?¹? cm² was measured during electron irradiation of thinner CH?CN films, while no chemical products were detected. The differences between the experimental results can be rationalized by recognizing that chemical reaction is a bulk effect in the CH?CN film, whereas desorption is a surface sensitive process. In thicker films, electron-promoted desorption is expected to occur a rate that is independent of the film thickness; i.e. show zeroth-order kinetics with respect to the surface concentration. PMID:23734051

Abdulgalil, A G M; Marchione, D; Thrower, J D; Collings, M P; McCoustra, M R S; Islam, F; Palumbo, M E; Congiu, E; Dulieu, F

2013-07-13

383

1/ f noise studies of swift heavy ion irradiated magnetite thin films  

NASA Astrophysics Data System (ADS)

The effect of 190 MeV 107Ag ion irradiation on antiphase boundaries (APBs) of epitaxial Fe 3O 4 thin films (thickness ˜70 nm) grown on MgO (1 0 0) oriented substrate has been investigated. The X-ray diffraction shows that at low fluence values upto 5 × 10 11 ions/cm 2, the strain in the films is relaxed whereas at high fluence 1 × 10 12 ions/cm 2, the epitaxial relationship with the substrate is decreasing. The low frequency conduction noise (1/ f noise) and electrical transport properties are found to depend on the value of ion fluence. The variation in Verwey transition temperature ( Tv) has been observed for low fluence, but it disappears at higher fluence (1 × 10 12 ions/cm 2). In the low fluence regime the Sv (V 2/Hz) decreases which is an evidence of the decrease in density of APBs. But higher fluence creates disorder in the system and hence increase in Sv and the density of APBs. The conduction noise is proportional to the square of the bias current ( Sv ? I2) for all films at room temperature, which confirms that the noise arises from the conduction fluctuations. On the basis of our observations we conclude that the strain created due to swift heavy ion (SHI) irradiation plays a major role in controlling the density of APBs.

Wasi Khan, M.; Kumar, Ravi; Srivastava, J. P.; Arora, S. K.; Choudhary, R. J.; Shvets, I. V.

2008-04-01

384

Tunneling current change of graphite surface by single ion irradiation  

SciTech Connect

The authors discuss changes in electronic structure and the topography of a graphite surface undergoing by a single ion impact. Protrusion-like regions (PLRs) found in a scanning tunneling microscope image disappeared in the same view of a noncontact atomic force microscope image. They measured tunneling current versus voltage characteristics to determine the density-of-states change in PLRs. They found that the density of states at the Fermi level of PLRs was greater than that of the intact surface. They therefore concluded that the PLRs were not actual topographical changes, but originated from electronic structural changes in semimetal to metal transition.

Ogiso, H. [National Inst. for Advanced Interdisciplinary Research, Tsukuba, Ibaraki (Japan). Joint Research Center for Atom Technology; [Mechanical Engineering Lab., Tsukuba, Ibaraki (Japan); Mizutani, W.; Nakano, S.; Tokumoto, H. [National Inst. for Advanced Interdisciplinary Research, Tsukuba, Ibaraki (Japan); Yamanaka, K. [Mechanical Engineering Lab., Tsukuba, Ibaraki (Japan)

1997-12-01

385

Spectral studies on Ag 8+ ions irradiated LAHCl·H 2O and LAHBr·H 2O single crystals  

NASA Astrophysics Data System (ADS)

L-Arginine hydrochloride monohydrate and L-arginine hydrobromide monohydrate single crystals are irradiated by 100 MeV Ag 8+ swift heavy ions. The residual gases liberated from the irradiated samples are monitored as a function of ion fluence using quadrupole mass analyzer. The C 2H 3+, C 2H 2, N 2, CO, HCl and CO 2 are the dominant gases liberated. Fourier transform infrared spectra of irradiated crystals explain the breaking of bonds in a localized region of the crystals. The crystallinity of irradiated crystals is analyzed by powder X-ray diffractions.

Sangeetha, K.; Ramesh Babu, R.; Ramamurthi, K.; Prakash, Jai; Khan, S. A.

2011-09-01

386

Effect of ion irradiation on structural properties of Cu64Zr36 metallic glass  

NASA Astrophysics Data System (ADS)

By means of molecular dynamics simulations, we study the low energy ion irradiation effect on the short-range order (SRO) of metallic glass structures. Breaking the topological SRO in a controlled manner may lead to desirable modifications of deformation behavior of glass structures. These changes in SRO were also found to be stable during the thermal annealing at temperatures below the glass transition temperature (Tg). The tensile deformation simulations performed for the Cu-Zr glass nanorods show that irradiated nanorods become softer compared to the pristine ones, changing the yielding mechanism - from a slip via formation of a single shear band to formation of a broad necking region.

Avchaciov, K. A.; Ritter, Y.; Djurabekova, F.; Nordlund, K.; Albe, K.

2014-12-01

387

Heavy-ion microbeam system for cell irradiation at Kyoto University  

NASA Astrophysics Data System (ADS)

We have developed a heavy-ion microbeam system for cell irradiation that uses an 8-MV tandem Van de Graaff accelerator at Kyoto University. Using a pair of apertures as the final collimator, microbeams of carbon, fluorine, and silicon were extracted to the atmosphere with few background particles. We used a thin transmission scintillator and a photomultiplier detector to accurately measure the number of extracted particles. To examine beam spreading, the beam profile was measured by observing tracks of an irradiated CR-39 track detector. The two disks with holes which were added to the collimating apertures reduced background radiation due to secondary X-rays and electrons from the apertures.

Nakamura, M.; Imai, K.; Hirose, M.; Matsumoto, H.; Tosaki, M.; Ohsawa, D.; Makino, S.

2011-12-01

388

Nanometer-scale tunnel formation in metallic glass by helium ion irradiation  

SciTech Connect

We have shown that upon high fluence helium ion irradiation, metallic glass Cu{sub 50}Zr{sub 45}Ti{sub 5} becomes highly porous at the depth of the helium projected range. The resulting porous region is characterized by the formation of a tunnel like structure and self-linkage of nanometer size gas bubbles. Furthermore, the irradiation leads to the formation of nanometer size Cu{sub x}Zr{sub y} crystals that are randomly distributed. The results of this study indicate that the He-filled bubbles have attractive interactions and experience considerable mobility. Movement of the bubbles is believed to be assisted by ballistic collisions.

Shao Lin [Department of Nuclear Engineering, Texas A and M University, College Station, Texas 77843 (United States); Materials Science and Engineering Program, Texas A and M University, College Station, Texas 77843 (United States); Gorman, Brian P. [Department of Metallurgical and Materials Engineering, Colorado School of Mines, Golden, Colorado 80401 (United States); Aitkaliyeva, Assel [Materials Science and Engineering Program, Texas A and M University, College Station, Texas 77843 (United States); David Theodore, N. [CHD-Fab, Freescale Semiconductor, Inc., Chandler, Arizona 85224 (United States); Xie Guoqiang [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan)

2012-07-23

389

The effects of high-energy uranium ion irradiation on Au/n-GaN Schottky diodes  

NASA Astrophysics Data System (ADS)

The I-V and C-V characteristics of Au/n-GaN Schottky diodes irradiated with 290-MeV 238U32+ ions are presented. The U ions can penetrate the n-type GaN epi-layer with a thickness about 3 ?m grown on the c-plane of a sapphire substrate using the MOCVD technique, leaving a purely electronic energy deposition. The Au/n-GaN Schottky diodes were irradiated to successively increasing fluences from 1 × 109 to 5 × 1011 ions cm-2. The measured I-V curves show that the height of the Schottky barrier decreases after irradiation and that the Schottky barrier almost disappears when the ion fluence reaches 5 × 1010 ions cm-2. Meanwhile, the irradiation increases the series resistance. The C-V curves show that the capacitance drops sharply when the ion fluence reaches 5 × 1010 ions cm-2. The dielectric constant also decreases following the irradiation. The changes of the electrical properties are ascribed to the neutralization of the donor-like surface state and the acceptor-like surface state due to the migration of Au atoms at the interface of Au/n-GaN under energetic U ions irradiations.

Gou, J.; Zhang, C. H.; Zhang, L. Q.; Song, Y.; Wang, L. X.; Li, J. J.; Meng, Y. C.; Li, H. X.; Yang, Y. T.; Lu, Z. W.

2014-11-01

390

Defect accumulation in ThO2 irradiated with swift heavy ions  

NASA Astrophysics Data System (ADS)

Polycrystalline ThO2 was irradiated with 2.2 GeV Au ions and characterized by synchrotron X-ray diffraction, X-ray absorption spectroscopy, and Raman spectroscopy. The diffraction measurements indicated an increase in the unit cell parameter and the accumulation of heterogeneous microstrain with increasing ion fluence, both of which are consistent with a single-impact model of damage accumulation. An analytical fit of the data to a single-impact model yielded a saturation unit cell expansion of 0.049 ± 0.002% and a saturation strain of 10.4 ± 0.2%. Cross-section data determined from the model values yielded effective ion track diameters of 1.9 ± 0.2 nm and 3.2 ± 0.3 nm for the two modifications, respectively, indicating that the tracks consist of a core region in which swelling and strain have occurred and a defect-rich halo in which microstrain is present but the initial unit cell parameter has not changed significantly. The spectroscopic analysis revealed the presence of significant local structural distortion in the irradiated material, but no evidence of systematic modification to the electronic state or chemical environment of the cations. This indicates that swift heavy ion irradiation of ThO2 primarily produces simple point defects or defect agglomerates.

Tracy, Cameron L.; McLain Pray, J.; Lang, Maik; Popov, Dmitry; Park, Changyong; Trautmann, Christina; Ewing, Rodney C.

2014-05-01

391

Hyperpolarized 131Xe NMR spectroscopy  

PubMed Central

Hyperpolarized (hp) 131Xe with up to 2.2% spin polarization (i.e., 5000-fold signal enhancement at 9.4 T) was obtained after separation from the rubidium vapor of the spin-exchange optical pumping (SEOP) process. The SEOP was applied for several minutes in a stopped-flow mode, and the fast, quadrupolar-driven T1 relaxation of this spin I = 3/2 noble gas isotope required a rapid subsequent rubidium removal and swift transfer into the high magnetic field region for NMR detection. Because of the xenon density dependent 131Xe quadrupolar relaxation in the gas phase, the SEOP polarization build-up exhibits an even more pronounced dependence on xenon partial pressure than that observed in 129Xe SEOP. 131Xe is the only stable noble gas isotope with a positive gyromagnetic ratio and shows therefore a different relative phase between hp signal and thermal signal compared to all other noble gases. The gas phase 131Xe NMR spectrum displays a surface and magnetic field dependent quadrupolar splitting that was found to have additional gas pressure and gas composition dependence. The splitting was reduced by the presence of water vapor that presumably influences xenon-surface interactions. The hp 131Xe spectrum shows differential line broadening, suggesting the presence of strong adsorption sites. Beyond hp 131Xe NMR spectroscopy studies, a general equation for the high temperature, thermal spin polarization, P, for spin I?1/2 nuclei is presented. PMID:21051249

Stupic, Karl F.; Cleveland, Zackary I.; Pavlovskaya, Galina E.; Meersmann, Thomas

2011-01-01

392

Hyperpolarized (131)Xe NMR spectroscopy.  

PubMed

Hyperpolarized (hp) (131)Xe with up to 2.2% spin polarization (i.e., 5000-fold signal enhancement at 9.4 T) was obtained after separation from the rubidium vapor of the spin-exchange optical pumping (SEOP) process. The SEOP was applied for several minutes in a stopped-flow mode, and the fast, quadrupolar-driven T(1) relaxation of this spin I = 3/2 noble gas isotope required a rapid subsequent rubidium removal and swift transfer into the high magnetic field region for NMR detection. Because of the xenon density dependent (131)Xe quadrupolar relaxation in the gas phase, the SEOP polarization build-up exhibits an even more pronounced dependence on xenon partial pressure than that observed in (129)Xe SEOP. (131)Xe is the only stable noble gas isotope with a positive gyromagnetic ratio and shows therefore a different relative phase between hp signal and thermal signal compared to all other noble gases. The gas phase (131)Xe NMR spectrum displays a surface and magnetic field dependent quadrupolar splitting that was found to have additional gas pressure and gas composition dependence. The splitting was reduced by the presence of water vapor that presumably influences xenon-surface interactions. The hp (131)Xe spectrum shows differential line broadening, suggesting the presence of strong adsorption sites. Beyond hp (131)Xe NMR spectroscopy studies, a general equation for the high temperature, thermal spin polarization, P, for spin I ? 1/2 nuclei is presented. PMID:21051249

Stupic, Karl F; Cleveland, Zackary I; Pavlovskaya, Galina E; Meersmann, Thomas

2011-01-01

393

Correlation between the Atomic Alignment and the Alignment of XeX* (B, C) Rotation in the Reactions of Oriented Xe (3P2, MJ = 2) + Halogen (X)-Containing Molecules  

NASA Astrophysics Data System (ADS)

The polarization of the XeX* (B) and XeX* (C) emissions in the reactions of oriented Xe* (3P2, MJ = 2) + halogen (X)-containing molecules (CCl4, CF3Br, CF3I, CH3I, NF3) has been measured as a function of each magnetic MJ' substate in the collision frame. The parallel polarization of the XeX* (B, C) emissions to the relative velocity vector is commonly observed for all magnetic MJ' substates. The correlation between the atomic alignment (MJ') and the MJ'-dependent alignment (AMJ') of the XeX* (B, C) rotation is found to be extremely different between the XeX* (B) and XeX* (C) channels: For XeX* (B), AMJ' is highest for the MJ' = 0 state, except CCl4, whereas the |MJ'| = 2 states give the highest AMJ' for XeX* (C). Alternatively, the correlation between the configuration (LZ') of the inner 5p orbital and the LZ'-dependent alignment (ALZ') of the XeX* (B, C) rotations is revealed. The collision with |LZ'| = 1 causes a similar positive alignment ALZ' for the XeX* (B) and XeX* (C) channels. The alignment ALZ' at the collision with |LZ'| = 0 is extremely different between the XeX* (B) and XeX* (C) channels. The collision with LZ' = 0 induces no alignment of XeX* (C) except CF3I, that is, ALZ'=0 ? 0, whereas it induces the higher positive ALZ' of XeX* (B). The different MJ' dependence on the alignment of the XeX* (B, C) rotation between the XeX* (B) and XeX* (C) channels can be recognized as the change of reaction mechanism due to the difference in the favorable impact parameter for each MJ' state between the XeX* (B) and XeX* (C) channels, which reflects the ?' conservation in the course of ion-pair (Xe+-RX-) formation.

Ohoyama, H.; Yasuda, K.; Kasai, T.

2009-09-01

394

Heavy-Ion Irradiation of Thulium(III) Oxide Targets Prepared by Polymer-Assisted Deposition  

SciTech Connect

Thulium(III) oxide (Tm{sub 2}O{sub 3}) targets prepared by the polymer-assisted deposition (PAD) method were irradiated by heavy-ion beams to test the method's feasibility for nuclear science applications. Targets were prepared on silicon nitride backings (thickness of 1000 nm, 344 {micro}g/cm{sup 2}) and were irradiated with an {sup 40}Ar beam at laboratory frame energy of {approx}210 MeV (50 particle nA). The root mean squared (RMS) roughness prior to irradiation is 1.1 nm for a {approx}250 nm ({approx}220 {micro}g/cm{sup 2}) Tm{sub 2}O{sub 3} target, and an RMS roughness of 2.0 nm after irradiation was measured by atomic force microscopy (AFM). Scanning electron microscopy of the irradiated target reveals no significant differences in surface homogeneity when compared to imaging prior to irradiation. Target flaking was not observed from monitoring Rutherford scattered particles as a function of time.

Garcia, Mitch A.; Ali, Mazhar N.; Chang, Noel N.; Parsons-Moss, Tashi; Ashby, Paul D.; Gates, Jacklyn M.; Stavsetra, Liv; Gregorich, Kenneth E.; Nitsche, Heino

2008-09-15

395

Virus inactivation studies using ion beams, electron and gamma irradiation  

NASA Astrophysics Data System (ADS)

Known methods of virus inactivation are based on the chemical action of some substances such as acetylethylenimine, betapropiolactone, glycidalaldehyde, formaldehyde, etc. In such a process, the viral suspension should be kept at room or higher temperatures for 24-48 h. Under these conditions, physical and chemical agents act to degrade the virus antigenic proteins. On the contrary with ionizing radiations at low temperatures, the treatment does not cause such degradation allowing the study of different viral functions. In this work, particle (?, d and ß) and ? irradiations were used for partial and total inactivation of Foot and Mouth Disease Virus (FMDV), Rauscher Leukemia Virus (RLV) and Herpes Simplex Virus (HSV). Obtention of the D37 dose from survival curves and the application of the target theory, permitted the determination of molecular weight of the nucleic acid genomes, EBR values and useful information for vaccine preparation. For RLV virus, a two target model of the RNA genome was deduced in accordance with biological information while from data from the literature and our own work on the structure of the scrapie prion, considering the molecular weight obtained by application of the theory, a new model for prion replication is presented, based on a trimer molecule.

Smolko, Eduardo E.; Lombardo, Jorge H.

2005-07-01

396

The real structure of columnar pinning centers in heavy-ion-irradiated cuprate superconductors  

SciTech Connect

There has been considerable recent interest in the use of columnar defects produced by irradiation with energetic heavy ions to raise the irreversibility line and improve the critical current density of cuprate superconductors. In the interpretation and theoretical modeling of the flux-pinning characteristics of heavy-ion tracks, it is generally assumed that they are simply columns of non-superconducting material. In this paper we present a more realistic description, based both on resistivity measurements and on detailed, quantitative transmission electron microscope methods (both imaging and analytical studies), of the nature of heavy-ion damage, including defects, disorder, strain fields, and oxygen deficiencies in the matrix of the superconductor surrounding the amorphous columns. The presence of such disorder appears to be a consequence of the mechanism of track formation, which involves partial epitaxial regrowth of a molten region which follows the passage of sufficiently energetic ions.

Welch, D.O.; Zhu, Y. [Brookhaven National Lab., Upton, NY (United States); Budhani, R.C. [Indian Institute of Technology Kanpur (India). Dept. of Physics

1995-12-31

397

Atomistic model of defects for the simulation of RBS-channeling measurements in ion irradiated silicon  

NASA Astrophysics Data System (ADS)

In this work, a new method for the atomistic simulation of ion-channeling spectra for ion irradiated Si is reported. The disordered crystal is represented by a supercell populated with point defects and then relaxed through a static energy minimization procedure based on empirical potentials. By including this supercell in a computer code for the simulation of ion-channeling spectra, we try to reproduce multi-axial results in the slightly damaged surface region of high-energy ion implanted Si. In spite of the simple assumptions on the nature of defects, we find that our method substantially improves the multi-axial data fit in comparison with that obtained under the usual assumption of random point defects.

Lulli, G.; Albertazzi, E.; Balboni, S.; Bianconi, M.

2003-08-01

398

Nanoscale density fluctuations in swift heavy ion irradiated amorphous SiO{sub 2}  

SciTech Connect

We report on the observation of nanoscale density fluctuations in 2 {mu}m thick amorphous SiO{sub 2} layers irradiated with 185 MeV Au ions. At high fluences, in excess of approximately 5 x 10{sup 12} ions/cm{sup 2}, where the surface is completely covered by ion tracks, synchrotron small angle x-ray scattering measurements reveal the existence of a steady state of density fluctuations. In agreement with molecular dynamics simulations, this steady state is consistent with an ion track ''annihilation'' process, where high-density regions generated in the periphery of new tracks fill in low-density regions located at the center of existing tracks.

Kluth, P.; Giulian, R.; Ridgway, M. C. [Department of Electronic Materials Engineering, Australian National University, Canberra ACT 0200 (Australia); Pakarinen, O. H.; Djurabekova, F.; Nordlund, K. [Department of Physics and Helsinki Institute of Physics, University of Helsinki, Helsinki (Finland); Byrne, A. P. [Department of Nuclear Physics, Australian National University, Canberra ACT 0200 (Australia)

2011-12-15

399

Purification/annealing of graphene with 100-MeV Ag ion irradiation  

PubMed Central

Studies on interaction of graphene with radiation are important because of nanolithographic processes in graphene-based electronic devices and for space applications. Since the electronic properties of graphene are highly sensitive to the defects and number of layers in graphene sample, it is desirable to develop tools to engineer these two parameters. We report swift heavy ion (SHI) irradiation-induced annealing and purification effects in graphene films, similar to that observed in our studies on fullerenes and carbon nanotubes (CNTs). Raman studies after irradiation with 100-MeV Ag ions (fluences from 3?×?1010 to 1?×?1014 ions/cm2) show that the disorder parameter ?, defined by ID/IG ratio, decreases at lower fluences but increases at higher fluences beyond 1?×?1012 ions/cm2. This indicates that SHI induces annealing effects at lower fluences. We also observe that the number of graphene layers is reduced at fluences higher than 1?×?1013 ions/cm2. Using inelastic thermal spike model calculations, we estimate a radius of 2.6 nm for ion track core surrounded by a halo extending up to 11.6 nm. The transient temperature above the melting point in the track core results in damage, whereas lower temperature in the track halo is responsible for annealing. The results suggest that SHI irradiation fluence may be used as one of the tools for defect annealing and manipulation of the number of graphene layers. PACS 60.80.x; 81.05.ue PMID:24636520

2014-01-01

400

Effect of Proton and Silicon Ion Irradiation on Defect Formation in GaAs  

SciTech Connect

Electrical and structural changes in GaAs are monitored using electron beam induced current (EBIC) and transmission electron microscopy (TEM) measurements after irradiation by protons and silicon ions. It has been determined that higher energy protons (E ges 10 MeV) and silicon ions disordered regions that are electrically and structurally different than those produced by lower energy protons. The data suggest that these disordered regions are responsible for causing the deviations between experimental data and NIEL. From analyses of the recoil spectra, high energy recoils appear to be responsible for the formation of these disordered regions.

Warner, J. H.; Inguimbert, C.; Twigg, M. E.; Messenger, S. R.; Walters, R. J.; Romero, M. J.; SUmmers, G. P.

2008-12-01

401

Wide variety of flower-color and -shape mutants regenerated from leaf cultures irradiated with ion beams  

NASA Astrophysics Data System (ADS)

The efficiency of ion-beam irradiation combined with tissue culture in obtaining floral mutants was investigated and compared with those of gamma rays and X-rays in carnation. Leaf segments of carnation plants in vitro were irradiated with the 220 MeV carbon ions, and cultured till the shoot regenerated. The carbon ion had the highest effect in reducing the regeneration frequency, and the RBE value with respect to gamma-rays was four. The higher mutation frequency and the wider mutation spectrum were obtained in plants irradiated with the carbon ions than low LET radiations. Three new carnation varieties developed by ion-beam irradiation were applied for the registration of the Japanese Ministry of Agriculture, Forestry and Fisheries. The results indicate that ion beam irradiation could induce wide variety of flower-color and -shape mutants, and that the combined method of ion-beam irradiation with tissue culture is useful to obtain the commercial varieties in a short time.

Okamura, M.; Yasuno, N.; Ohtsuka, M.; Tanaka, A.; Shikazono, N.; Hase, Y.

2003-05-01

402

Effects of defect clustering on optical properties of GaN by single and molecular ion irradiation  

SciTech Connect

The effects of irradiation by F, P, and PF{sub 4} on optical properties of GaN were studied experimentally and by atomistic simulations. Additionally, the effect of Ag was studied by simulation. The irradiation energy was 0.6?keV/amu for all projectiles. The measured photoluminescence (PL) decay time was found to be decreasing faster when irradiation was done by molecular ion compared to light ion irradiation. The PL decay time change is connected with the types of defect produced by different projectiles. Simulation results show that the light ions mainly produce isolated point defects while molecular and heavy ions produce clusters of point defects. The total amount of defects produced by the PF{sub 4} projectile was found to be very close to the sum of all defects produced in five individual cascades started by one P and four F single ions. This and the similar depth profiles of damage produced by molecular and light ion irradiations suggest that the defect clusters are one of the important reasons for fast PL decay. Moreover, the simulations of irradiation by Ag ions, whose mass is close to the mass of the PF{sub 4} molecule, showed that the produced defects are clustering in even bigger conglomerates compared to PF{sub 4} case. The latter has a tendency to split in the pre-surface region, reducing on average the density of the collision cascade.

Ullah, M. W., E-mail: mohammad.ullah@helsinki.fi; Kuronen, A.; Nordlund, K.; Djurabekova, F. [Department of Physics, University of Helsinki, P.O. Box 64, FIN 00014 (Finland); Karaseov, P. A.; Karabeshkin, K. V.; Titov, A. I. [Department of Physical Electronics, St. Petersburg State Polytechnic University, St. Petersburg (Russian Federation)

2013-11-14

403

From holes to sponge at irradiated Ge surfaces with increasing ion energy—an effect of defect kinetics?  

NASA Astrophysics Data System (ADS)

We show that hole patterns and sponge-like layers at irradiated Ge surfaces originate from the same driving force, namely the kinetics of ion beam induced defects in the amorphous Ge surface layer. Ge hole patterns reported earlier for irradiation with low energy (5 keV) Ga+ ions were reproduced for low energy Bi+ but also for Ge+ self-irradiation, which proves that the dominating driving force for morphology evolution cannot originate from the implanted impurities. At higher ion energies the well-known formation of sponge-like Ge surface layers after heavy ion irradiation was found for Bi+ irradiation and Ge+ self-irradiation, also. The transition from smooth surfaces via hole patterns to sponge-like morphologies with increasing ion energies was studied in detail. A model based on the kinetics of ion beam induced defects was developed and implemented in 3D kinetic Monte Carlo simulations, which reproduce the transition from hole patterns to sponge-like layers with increasing ion energy.

Böttger, Roman; Heinig, Karl-Heinz; Bischoff, Lothar; Liedke, Bartosz; Facsko, Stefan

2013-10-01

404

Investigation of microstructure modification of C-doped a-SiO2/Si after Pb-ion irradiation  

NASA Astrophysics Data System (ADS)

Thermally grown amorphous SiO2 (a-SiO2) films were implanted at room temperature (RT) with 100 keV C-ions to 5.0×1017 ions/cm2. These samples were irradiated at RT with 853 MeV Pb-ions to 1.0×1012 and 5.0×1012 ions/cm2. Then the samples were investigated using Transmission Electron Microscopy (TEM) at RT. Significant microstructure modifications were observed in C-doped a-SiO2/Si samples after high energy Pb-ion irradiations, and the formation of new structures depended strongly on the Pb-ion irradiation fluences. For example, tracks in high density were observed in a 1.0×1012 Pb/cm2 irradiated and C-doped sample. Additionally, the length of tracks grows, and a large number of 8H-SiC nanocrystals can be seen in the film when irradiation fluence is increased to 5.0×1012 Pb/cm2. Possible modification processes of C-doped a-SiO2 under swift heavy ion irradiations are briefly discussed.

Liu, ChunBao; Wei, KongFang; Yao, CunFeng; Wang, ZhiGuang; Jin, YunFan; Toulemonde, M.

2012-02-01

405

Evolution of nanoripples on silicon by gas cluster-ion irradiation  

NASA Astrophysics Data System (ADS)

Si wafers of (100), (110) and (111) orientations were bombarded by gas cluster ion beam (GCIB) of 3000 Ar-atoms/cluster on average at a series of angles. Similar surface morphology ripples developed in different nanoscales. A simple scaling functional satisfactorily describe the roughness and wavelength of the ripple patterns as a function of dosage and angle of incidence. The ripples are formed orthogonal to the incident cluster-ions at large off-normal angles. An ellipsoidal pattern was created by two consecutive irradiations incident in mutually orthogonal directions with unequal exposure times between each irradiation, from 7:1 to 10:1, beyond which the original ripple imprints would be over-written. This work was inspired by use of the ripples to seed growth of controlled nanostructures without patterning by lithography or predeposition of catalysts.

Lozano, Omar; Chen, Q. Y.; Tilakaratne, B. P.; Seo, H. W.; Wang, X. M.; Wadekar, P. V.; Chinta, P. V.; Tu, L. W.; Ho, N. J.; Wijesundera, D.; Chu, W. K.

2013-06-01

406

In-situ investigation of polyvinyl formal irradiated with GeV Au ions  

NASA Astrophysics Data System (ADS)

Polyvinyl formal (Formvar®) foils were irradiated with 5.4 MeV/u Au ions and analysed in-situ by residual gas analysis and infrared spectroscopy. The experiment was performed at the new materials-research beamline (M-branch) at the universal linear accelerator of the GSI Helmholtz Centre in Darmstadt (Germany). Simultaneously analysing outgassing fragments and changes within the irradiated polymer film allows monitoring details of the degradation process. Ion-induced degradation of polyvinyl formal is characterized by fragmentation of side chains of the polymer backbone. The infrared spectra show the formation of unsaturated hydrocarbons and ketones. A possible degradation mechanism is proposed including the production of enols as reported earlier for degradation of polyvinyl alcohol exposed to gamma radiation.

Seidl, T.; Baake, O.; Hossain, U. H.; Bender, M.; Severin, D.; Trautmann, C.; Ensinger, W.

2012-02-01

407

Application of positron beam Doppler broadening technique to ion beam irradiation in nickel  

NASA Astrophysics Data System (ADS)

The formation processes of vacancy-type defects induced by ion irradiation in nickel were investigated with a variable-energy positron beam Doppler broadening technique in order to find the appropriate experimental condition for in situ positron beam experiments. Nickel ion irradiation at 300-343 K induces an S parameter increase, but the dependence of the S parameter on positron energy is very similar to that of cold-rolled nickel, which suggests positron trapping by small vacancy-type defects such as SFTs. The best experimental condition for investigation of cavity nucleation process by in situ positron beam Doppler experiments is suggested to be around 0.1-0.4 dpa at 773 K.

Iwai, Takeo; Tsuchida, Hidetsugu; Awano, Misa

2007-08-01

408

Optical waveguides in LiTaO3 crystals fabricated by swift C5+ ion irradiation  

NASA Astrophysics Data System (ADS)

We report on the optical waveguides, in both planar and ridge configurations, fabricated in LiTaO3 crystal by using carbon (C5+) ions irradiation at energy of 15 MeV. The planar waveguide was produced by direct irradiation of swift C5+ ions, whilst the ridge waveguides were manufactured by using femtosecond laser ablation of the planar layer. The reconstructed refractive index profile of the planar waveguide has showed a barrier-shaped distribution, and the near-field waveguide mode intensity distribution was in good agreement with the calculated modal profile. After thermal annealing at 260 °C in air, the propagation losses of both the planar and ridge waveguides were reduced to 10 dB/cm.

Liu, Guiyuan; He, Ruiyun; Akhmadaliev, Shavkat; Vázquez de Aldana, Javier R.; Zhou, Shengqiang; Chen, Feng

2014-04-01

409

Control of interlayer exchange coupling in Fe/Cr/Fe trilayers by ion beam irradiation.  

PubMed

The manipulation of the antiferromagnetic interlayer coupling in epitaxial Fe/Cr/Fe(001) trilayers by 5 keV He ion beam irradiation has been investigated. It is shown that even for irradiation with low fluences a drastic change in strength of the coupling appears. For thin Cr spacers (below 0.6-0.7 nm) it decreases with fluence, becoming ferromagnetic for fluences above 2x10(14) ions/cm(2). The effect is connected with the creation of magnetic bridges in the layered system due to atomic exchange events caused by the bombardment. For thicker Cr spacers an enhancement of the antiferromagnetic coupling strength is found. A possible explanation of the enhancement effect is given. PMID:12689250

Demokritov, S O; Bayer, C; Poppe, S; Rickart, M; Fassbender, J; Hillebrands, B; Kholin, D I; Kreines, N M; Liedke, O M

2003-03-01

410

Outgassing and degradation of polyimide induced by swift heavy ion irradiation at cryogenic temperature  

NASA Astrophysics Data System (ADS)

Polyimide foils were irradiated with energetic Kr (740 MeV) and Pb (890 MeV) ions at cryogenic temperature (12 K). Beam-induced degradation processes were monitored by residual gas analysis and online infrared spectroscopy. The outgassing components observed at low irradiation temperatures differ in quantity but are similar in mass distribution to those identified at room temperature exposure. Besides CO as major volatile fragment, a significant contribution of short hydrocarbons like C2Hx is released. In situ infrared spectroscopy indicates accumulation of CO and CO2 molecules at 12 K in the foils. During heat-up cycles, most of these frozen gases become mobile and outgas at a temperature between 35 and 55 K. The study is motivated by the application of polyimide foils as insulating material in high radiation environment of the future accelerator facility for antiproton and ion research (FAIR).

Severin, D.; Balanzat, E.; Ensinger, W.; Trautmann, C.

2010-07-01

411

Annealing of defects in Fe after MeV heavy-ion irradiation  

NASA Astrophysics Data System (ADS)

We report a study of recovery dynamics, followed by in situ resistivity measurements after 100 MeV oxygen ion irradiation, in cold rolled Fe at 300 K. Scaling behavior with microstructural density and temperature of the sample have been used to establish stress-induced defects formed during irradiation as a new type of sink. The dynamics after irradiation has been shown to be due to migration of defects to two types of sinks, i.e. stress-induced defects as variable sinks and internal surfaces as fixed sinks. Experimental data obtained under various experimental conditions have been fitted to theoretical curves. The parameters thus obtained from fitting are employed to establish the effect of electronic energy loss and temperature on the recovery dynamics and stress associated with variable sinks.

Aggarwal, G.; Sen, P.

1998-11-01

412

Encapsulation of cesium inside single-walled carbon nanotubes by plasma-ion irradiation method  

Microsoft Academic Search

Positive Cs ions are irradiated to a negatively biased substrate, which is covered with the dispersed single-walled carbon nanotubes (SWNTs) and immersed in the Cs plasma. Field emission type transmission electron microscopy (FE-TEM) and Z-contrast technique by scanning TEM (STEM) are used for the precise observation. FE-TEM gives high resolved images of structurally modified SWNTs such as irreversible bending of

Goo-Hwan Jeong; A. A. Farajian; Takamichi Hirata; Rikizo Hatakeyama; Kazuyuki Tohji; T. M. Briere; Hiroshi Mizuseki; Yoshiyuki Kawazoe

2003-01-01

413

Temperature and frequency dependent electrical properties of 50 MeV Li ion irradiated polymeric blends  

Microsoft Academic Search

The polymeric blends of polyvinyl chloride (PVC) and polyethylene terephthalate (PET) with equal composition by weight have been irradiated with 50 MeV Li ions at different fluences. The AC electrical properties of polymeric blends were measured in the frequency range 0.05–100 kHz, and at temperature range 40–150 C using LCR meter. There is an exponential increase in conductivity with log of frequency and

N. L. Singh; Anita Sharma; D. K. Avasthi; V. Shrinet

2005-01-01

414

Effects of high energy (MeV) ion beam irradiation on polyethylene terephthalate  

Microsoft Academic Search

Irradiation effects of 50 MeV Li3+ ion beams in polyethylene terephthalate (PET) films were studied with respect to their structural and electrical properties by using Fourier transform infrared (FTIR) spectroscopy and ac electrical measurement in the frequency range: 50–100 kHz at different temperatures of 30–150 °C. It is found that ac resistivity of PET decreases as frequency increases. The temperature

Nandlal Singh; Anita Sharma; D. K. Avasthi

2003-01-01

415

Ion irradiation: its relevance to the evolution of complex organics in the outer solar system.  

PubMed

Ion irradiation of carbon containing ices produces several effects among which the formation of complex molecules and even refractory organic materials whose spectral color and molecular complexity both depend on the amount of deposited energy. Here results from laboratory experiments are summarized. Their relevance for the formation and evolution of simple molecules and complex organic materials on planetary bodies in the external Solar System is outlined. PMID:11541336

Strazzulla, G

1997-01-01

416

Effect of ion irradiation on the thermal stability of thin polymer films  

NASA Astrophysics Data System (ADS)

We report on the stability of poly(methyl methacrylate) thin films in vacuum after exposure to moderate doses of 300 keV H+, 2 MeV H+, and 18 MeV Au7+ ions combined to thermal treatments. A small but steady increase in roughness of the films with increasing fluence was observed for bombardments at room temperature at a rate that varied strongly with dE/dx. For irradiations at 100 °C, the roughness also increased sharply