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Sample records for low-energy nitrogen implantation

  1. Nitrogen mass transfer models for plasma-based low-energy ion implantation

    SciTech Connect

    Zheng, Bocong; Wang, Kesheng; Zhang, Zhipeng; Che, Honglong; Lei, Mingkai

    2015-03-15

    The nitrogen mass transfer process in plasma-based low-energy ion implantation (PBLEII) is theoretically and experimentally studied in order to explore the process mechanism of PBLEII and therefore to optimize the apparatus design and the process conditions. An electron cyclotron resonance (ECR) microwave discharge generates the nitrogen plasma with a high density of 10{sup 11}–10{sup 12} ions/cm{sup 3}, which diffuses downstream to the process chamber along the divergent magnetic field. The nitrogen ions in the plasma implant into the surface and transport to the matrix of an austenitic stainless steel under the low negative pulsed bias of −2 kV at a process temperature of 400 °C. A global plasma model is used to simulate the ECR microwave plasma discharge for a range of working pressures and microwave powers. The fluid models are adopted to calculate the plasma downstream diffusion, the sheath expansion and the low-energy ion implantation on the surface. A nonlinear kinetic discrete model is established to describe the nitrogen transport in the austenitic stainless steel and the results are compared with the experimental measurements. Under an average implantation current density of 0.3–0.6 mA/cm{sup 2}, the surface nitrogen concentration in the range from 18.5 to 29 at. % is a critical factor for the nitrogen transport in the AISI 304 austenitic stainless steel by PBLEII, which accelerates the implanted nitrogen diffusion inward up to 6–12 μm during a nitriding time of 4 h.

  2. Enhanced nitrogen and phosphorus removal from eutrophic lake water by Ipomoea aquatica with low-energy ion implantation.

    PubMed

    Li, Miao; Wu, Yue-Jin; Yu, Zeng-Liang; Sheng, Guo-Ping; Yu, Han-Qing

    2009-03-01

    Ipomoea aquatica with low-energy N+ ion implantation was used for the removal of both nitrogen and phosphorus from the eutrophic Chaohu Lake, China. The biomass growth, nitrate reductase and peroxidase activities of the implanted I. aquatica were found to be higher than those of I. aquatica without ion implantation. Higher NO3-N and PO4-P removal efficiencies were obtained for the I. aquatica irradiation at 25 keV, 3.9 x 10(16) N+ ions/cm(2) and 20 keV 5.2 x 10(16) N+ ions/cm(2), respectively (p < 0.05). Moreover, the nitrogen and phosphorus contents in the plant biomass with ion implantation were also greater than those of the controls. I. aquatica with ion implantation was directly responsible for 51-68% N removal and 54-71% P removal in the three experiments. The results further confirm that the ion implantation could enhance the growth potential of I. aquatica in real eutrophic water and increase its nutrient removal efficiency. Thus, the low-energy ion implantation for aquatic plants could be considered as an approach for in situ phytoremediation and bioremediation of eutrophic waters.

  3. Biological effects of low energy nitrogen ion implantation on Jatropha curcas L. seed germination

    NASA Astrophysics Data System (ADS)

    Xu, Gang; Wang, Xiao-teng; Gan, Cai-ling; Fang, Yan-qiong; Zhang, Meng

    2012-09-01

    To explore the biological effects of nitrogen ion beam implantation on dry Jatropha curcas seed, a beam of N+ with energy of 25 keV was applied to treat the dry seed at six different doses. N+ beam implantation greatly decreased germination rate and seedling survival rate. The doses within the range of 12 × 1016 to 15 × 1016 ions cm-2 severely damaged the seeds: total antioxidant capacity (TAC), germination rate, seedling survival rate, reduced ascorbate acid (HAsA) and reduced glutathione (GSH) contents, and most of the tested antioxidases activity (i.e. catalase (CAT), ascorbate peroxidase (APX) and superoxide dismutase (SOD)) reached their lowest levels. At a dose of 18 × 1016 ion cm-2, biological repair took place: moderate increases were found in TAC, germination rate, seedling survival rate, HAsA and GSH contents, and some antioxidant enzyme activities (i.e. CAT, APX, SOD and GPX). The dose of 18 × 1016 ions cm-2 may be the optimum dose for use in dry J. curcas seed mutation breeding. CAT, HAsA and GSH contributed to the increase of TAC, but CAT was the most important. POD performed its important role as seed was severely damaged. The main role of the HAsA-GSH cycle appeared to be for regeneration of HAsA.

  4. Improving low-energy boron/nitrogen ion implantation in graphene by ion bombardment at oblique angles

    NASA Astrophysics Data System (ADS)

    Bai, Zhitong; Zhang, Lin; Liu, Ling

    2016-04-01

    Ion implantation is a widely adopted approach to structurally modify graphene and tune its electrical properties for a variety of applications. Further development of the approach requires a fundamental understanding of the mechanisms that govern the ion bombardment process as well as establishment of key relationships between the controlling parameters and the dominant physics. Here, using molecular dynamics simulations with adaptive bond order calculations, we demonstrate that boron and nitrogen ion bombardment at oblique angles (particularly at 70°) can improve both the productivity and quality of perfect substitution by over 25%. We accomplished this by systematically analyzing the effects of the incident angle and ion energy in determining the probabilities of six distinct types of physics that may occur in an ion bombardment event, including reflection, absorption, substitution, single vacancy, double vacancy, and transmission. By analyzing the atomic trajectories from 576 000 simulations, we identified three single vacancy creation mechanisms and four double vacancy creation mechanisms, and quantified their probability distributions in the angle-energy space. These findings further open the door for improved control of ion implantation towards a wide range of applications of graphene.Ion implantation is a widely adopted approach to structurally modify graphene and tune its electrical properties for a variety of applications. Further development of the approach requires a fundamental understanding of the mechanisms that govern the ion bombardment process as well as establishment of key relationships between the controlling parameters and the dominant physics. Here, using molecular dynamics simulations with adaptive bond order calculations, we demonstrate that boron and nitrogen ion bombardment at oblique angles (particularly at 70°) can improve both the productivity and quality of perfect substitution by over 25%. We accomplished this by systematically

  5. Surface Passivation and Junction Formation Using Low Energy Hydrogen Implants

    NASA Technical Reports Server (NTRS)

    Fonash, S. J.

    1985-01-01

    New applications for high current, low energy hydrogen ion implants on single crystal and polycrystal silicon grain boundaries are discussed. The effects of low energy hydrogen ion beams on crystalline Si surfaces are considered. The effect of these beams on bulk defects in crystalline Si is addressed. Specific applications of H+ implants to crystalline Si processing are discussed. In all of the situations reported on, the hydrogen beams were produced using a high current Kaufman ion source.

  6. Study of Biological Effects of Low Energy Ion Implantation on Tomato and Radish Breeding

    NASA Astrophysics Data System (ADS)

    Liang, Qiuxia; Huang, Qunce; Cao, Gangqiang; Ying, Fangqing; Liu, Yanbo; Huang, Wen

    2008-04-01

    Biological effects of 30 keV low energy nitrogen ion implantation on the seeds of five types of tomato and one type of radish were investigated. Results showed that low energy ions have different effects on different vegetables. The whole dose-response curve of the germination ratio did not take on "the shape of saddle", but was a rising and falling waveform with the increase or decrease in ion implantation. In the vegetable of Solanaceae, two outstanding aberrant plants were selected from M1 of Henan No.4 tomato at a dose of 7 × 1017 nitrogen ions/cm2, which had thin-leaves, long-petal and nipple tip fruit stably inherited to M7. Furthermore the analysis of the isozyme showed that the activity of the mutant tomato seedling was distinct in quantity and color. In Raphanus sativus L., the aberrances were obvious in the mutant of radish 791 at a dose of 5 × 1017 nitrogen ions/cm2, and the weight of succulent root and the volume of growth were over twice the control's. At present, many species for breeding have been identified in the field and only stable species have been selected for the experiment of production. It is evident that the low energy ion implantation technology has clear effects on vegetables' genetic improvement.

  7. Dynamic MC simulation of low-energy ion implantation

    NASA Astrophysics Data System (ADS)

    Yamamura, Y.

    1999-06-01

    In order to investigate the ion fluence effect in the depth profiles of the dynamic Monte Carlo code, ACAT-DIFFUSE, is applied to the calculation of depth profiles due to low-energy B ion implantation, where 1 and 5 keV B ions are implanted into an amorphized silicon target. As the ion fluence increases, the dopant B atoms are accumulated in solids and the target must be considered as a two-component material composed of the original target atoms and trapped implanted ions. This results in the radiation-induced-diffusion and the self-sputtering of trapped implanted ions. It is found that the peak locations of the dopant B depth profiles at 1 keV B ion bombardment shifted to the surface due to radiation-induced diffusion as ion increased and we observe the near-the-surface enhancement in the dopant B depth profiles due to 5 keV B ion bombardment. The self-sputtering also becomes important with increasing ion fluence. The retention ratios of the implanted B atoms are about 0.89 and 0.94 for 1 and 5 keV B ions, respectively, at 3.0 × 10 13 B ions/cm 2.

  8. Molecular ion sources for low energy semiconductor ion implantation (invited)

    NASA Astrophysics Data System (ADS)

    Hershcovitch, A.; Gushenets, V. I.; Seleznev, D. N.; Bugaev, A. S.; Dugin, S.; Oks, E. M.; Kulevoy, T. V.; Alexeyenko, O.; Kozlov, A.; Kropachev, G. N.; Kuibeda, R. P.; Minaev, S.; Vizir, A.; Yushkov, G. Yu.

    2016-02-01

    Smaller semiconductors require shallow, low energy ion implantation, resulting space charge effects, which reduced beam currents and production rates. To increase production rates, molecular ions are used. Boron and phosphorous (or arsenic) implantation is needed for P-type and N-type semiconductors, respectively. Carborane, which is the most stable molecular boron ion leaves unacceptable carbon residue on extraction grids. A self-cleaning carborane acid compound (C4H12B10O4) was synthesized and utilized in the ITEP Bernas ion source resulting in large carborane ion output, without carbon residue. Pure gaseous processes are desired to enable rapid switch among ion species. Molecular phosphorous was generated by introducing phosphine in dissociators via 4PH3 = P4 + 6H2; generated molecular phosphorous in a pure gaseous process was then injected into the HCEI Calutron-Bernas ion source, from which P4+ ion beams were extracted. Results from devices and some additional concepts are described.

  9. Molecular ion sources for low energy semiconductor ion implantation (invited).

    PubMed

    Hershcovitch, A; Gushenets, V I; Seleznev, D N; Bugaev, A S; Dugin, S; Oks, E M; Kulevoy, T V; Alexeyenko, O; Kozlov, A; Kropachev, G N; Kuibeda, R P; Minaev, S; Vizir, A; Yushkov, G Yu

    2016-02-01

    Smaller semiconductors require shallow, low energy ion implantation, resulting space charge effects, which reduced beam currents and production rates. To increase production rates, molecular ions are used. Boron and phosphorous (or arsenic) implantation is needed for P-type and N-type semiconductors, respectively. Carborane, which is the most stable molecular boron ion leaves unacceptable carbon residue on extraction grids. A self-cleaning carborane acid compound (C4H12B10O4) was synthesized and utilized in the ITEP Bernas ion source resulting in large carborane ion output, without carbon residue. Pure gaseous processes are desired to enable rapid switch among ion species. Molecular phosphorous was generated by introducing phosphine in dissociators via 4PH3 = P4 + 6H2; generated molecular phosphorous in a pure gaseous process was then injected into the HCEI Calutron-Bernas ion source, from which P4(+) ion beams were extracted. Results from devices and some additional concepts are described.

  10. Low-energy ion implantation: Large mass fractionation of argon

    NASA Technical Reports Server (NTRS)

    Ponganis, K. V.; Graf, TH.; Marti, K.

    1993-01-01

    The isotropic signatures of noble gases in the atmospheres of the Earth and other planets are considerably evolved when compared to signatures observed in the solar wind. The mechanisms driving the evolution of planetary volatiles from original compositions in the solar accretion disk are currently poorly understood. Modeling of noble-gas compositional histories requires knowledge of fractionating processes that may have operated through the evolutionary stages. Since these gases are chemically inert, information on noble-gas fractionation processes can be used as probes. The importance of understanding these processes extends well beyond 'noble-gas planetology.' Trapped argon acquired by low-energy implantation (approximately less than 100 eV) into solids is strongly mass fractionated (approximately greater than or equal to 3 percent/amu). This has potential implications for the origin and evolution of terrestrial planet atmospheres.

  11. Molecular ion sources for low energy semiconductor ion implantation (invited)

    SciTech Connect

    Hershcovitch, A.; Gushenets, V. I.; Bugaev, A. S.; Oks, E. M.; Vizir, A.; Yushkov, G. Yu.; Seleznev, D. N.; Kulevoy, T. V.; Kozlov, A.; Kropachev, G. N.; Kuibeda, R. P.; Minaev, S.; Dugin, S.; Alexeyenko, O.

    2016-02-15

    Smaller semiconductors require shallow, low energy ion implantation, resulting space charge effects, which reduced beam currents and production rates. To increase production rates, molecular ions are used. Boron and phosphorous (or arsenic) implantation is needed for P-type and N-type semiconductors, respectively. Carborane, which is the most stable molecular boron ion leaves unacceptable carbon residue on extraction grids. A self-cleaning carborane acid compound (C{sub 4}H{sub 12}B{sub 10}O{sub 4}) was synthesized and utilized in the ITEP Bernas ion source resulting in large carborane ion output, without carbon residue. Pure gaseous processes are desired to enable rapid switch among ion species. Molecular phosphorous was generated by introducing phosphine in dissociators via 4PH{sub 3} = P{sub 4} + 6H{sub 2}; generated molecular phosphorous in a pure gaseous process was then injected into the HCEI Calutron-Bernas ion source, from which P{sub 4}{sup +} ion beams were extracted. Results from devices and some additional concepts are described.

  12. Damaging Effect of Low Energy N+ Implantation on Aspergillus niger Spores

    NASA Astrophysics Data System (ADS)

    Wang, Lisheng; Cai, Kezhou; Cheng, Maoji; Chen, Lijuan; Liu, Xuelan; Zhang, Shuqing; Yu, Zengliang

    2007-06-01

    The mutant effects of a keV range nitrogen ion (N+) beam on enzyme-producing probiotics were studied, particularly with regard to the induction in the genome. The electron spin resonance (ESR) results showed that the signal of ESR spectrum existed in both implanted and non-implanted spores, and the yields of free radicals increased in a dose-dependent manner. The ionic etching and dilapidation of cell wall could be observed distinctly through the scanning electron microscope (SEM). The mutagenic effect on genome indicated that N+ implantation could make base mutation. This study provided an insight into the roles low-energy ions might play in inducing mutagenesis of micro-organisms.

  13. Effect of low-energy hydrogen ion implantation on dendritic web silicon solar cells

    NASA Technical Reports Server (NTRS)

    Rohatgi, A.; Meier, D. L.; Rai-Choudhury, P.; Fonash, S. J.; Singh, R.

    1986-01-01

    The effect of a low-energy (0.4 keV), short-time (2-min), heavy-dose (10 to the 18th/sq cm) hydrogen ion implant on dendritic web silicon solar cells and material was investigated. Such an implant was observed to improve the cell open-circuit voltage and short-circuit current appreciably for a number of cells. In spite of the low implant energy, measurements of internal quantum efficiency indicate that it is the base of the cell, rather than the emitter, which benefits from the hydrogen implant. This is supported by the observation that the measured minority-carrier diffusion length in the base did not change when the emitter was removed. In some cases, a threefold increase of the base diffusion length was observed after implantation. The effects of the hydrogen implantation were not changed by a thermal stress test at 250 C for 111 h in nitrogen. It is speculated that hydrogen enters the bulk by traveling along dislocations, as proposed recently for edge-defined film-fed growth silicon ribbon.

  14. A novel approach to microbial breeding--low-energy ion implantation.

    PubMed

    Gu, Shao-Bin; Li, Shi-Chang; Feng, Hui-Yun; Wu, Ying; Yu, Zeng-Liang

    2008-02-01

    Low-energy ions exist widely in the natural world. People had neglected the interaction between low-energy ions and material; it was even more out of the question to study the relation of low-energy ions and the complicated organism until the biological effects of low-energy ion implantation were discovered in 1989. Nowadays, the value of low-energy ion beam implantation, as a new breeding way, has drawn extensive attention of biologists and breeding experts. In this review, the understanding and utilization of microbial breeding by low-energy ion beam irradiation is summarized, including the characteristics of an ion beam bioengineering facility, present status of the technology of low-energy ions for microbial breeding, and new insights into microbial biotechnology.

  15. Low-energy plasma immersion ion implantation to induce DNA transfer into bacterial E. coli

    NASA Astrophysics Data System (ADS)

    Sangwijit, K.; Yu, L. D.; Sarapirom, S.; Pitakrattananukool, S.; Anuntalabhochai, S.

    2015-12-01

    Plasma immersion ion implantation (PIII) at low energy was for the first time applied as a novel biotechnology to induce DNA transfer into bacterial cells. Argon or nitrogen PIII at low bias voltages of 2.5, 5 and 10 kV and fluences ranging from 1 × 1012 to 1 × 1017 ions/cm2 treated cells of Escherichia coli (E. coli). Subsequently, DNA transfer was operated by mixing the PIII-treated cells with DNA. Successes in PIII-induced DNA transfer were demonstrated by marker gene expressions. The induction of DNA transfer was ion-energy, fluence and DNA-size dependent. The DNA transferred in the cells was confirmed functioning. Mechanisms of the PIII-induced DNA transfer were investigated and discussed in terms of the E. coli cell envelope anatomy. Compared with conventional ion-beam-induced DNA transfer, PIII-induced DNA transfer was simpler with lower cost but higher efficiency.

  16. Characterization of nitrogen species incorporated into graphite using low energy nitrogen ion sputtering.

    PubMed

    Kiuchi, Hisao; Kondo, Takahiro; Sakurai, Masataka; Guo, Donghui; Nakamura, Junji; Niwa, Hideharu; Miyawaki, Jun; Kawai, Maki; Oshima, Masaharu; Harada, Yoshihisa

    2016-01-07

    The electronic structures of nitrogen species incorporated into highly oriented pyrolytic graphite (HOPG), prepared by low energy (200 eV) nitrogen ion sputtering and subsequent annealing at 1000 K, were investigated by X-ray photoelectron spectroscopy (XPS), angle-dependent X-ray absorption spectroscopy (XAS), and Raman spectroscopy. An additional peak was observed at higher binding energy of 401.9 eV than 400.9 eV for graphitic1 N (graphitic N in the basal plane) in N 1s XPS, where graphitic2 N (graphitic N in the zigzag edge and/or vacancy sites) has been theoretically expected to appear. N 1s XPS showed that graphitic1 N and graphitic2 N were preferably incorporated under low nitrogen content doping conditions (8 × 10(13) ions cm(-2)), while pyridinic N and graphitic1 N were dominantly observed under high nitrogen content doping conditions. In addition, angle-dependent N 1s XAS showed that the graphitic N and pyridinic N atoms were incorporated into the basal plane of HOPG and thus were highly oriented. Furthermore, Raman spectroscopy revealed that low energy sputtering resulted in almost no fraction of the disturbed graphite surface layers under the lowest nitrogen doping condition. The suitable nitrogen doping condition was discovered for realizing the well-controlled nitrogen doped HOPG. The electrochemical properties for the oxygen reduction reaction of these samples in acidic solution were examined and discussed.

  17. Study on the growth and the photosynthetic characteristics of low energy C(+) ion implantation on peanut.

    PubMed

    Han, Yuguo; Xu, Lei; Yang, Peiling; Ren, Shumei

    2013-01-01

    Employing the Nonghua 5 peanut as experimental material, the effects of low energy C(+) ion implantation on caulis height, root length, dry weight, photosynthetic characteristics and leaf water use efficiency (WUE) of Peanut Ml Generation were studied. Four fluences were observed in the experiment. The results showed that ion implantation harmed the peanut seeds because caulis height, root length and dry weight all were lower in the treatments than in CK, and the harm was aggravated with the increase of ion fluence. Both Pn and Tr show a saddle-shape curve due to midday depression of photosynthesis. Low fluence of low energy C(+) ion implantation could increase the diurnal average Pn of peanut. The diurnal variation of Tr did not change as significantly as Pn. The light saturation point (LSP) was restrained by the ions. After low energy C(+) ion implantation, WUE was enhanced. When the fluence increased to a certain level, the WUE began to decrease.

  18. Use of low energy hydrogen ion implants in high efficiency crystalline silicon solar cells

    NASA Technical Reports Server (NTRS)

    Fonash, S. J.; Singh, R.

    1985-01-01

    This program is a study of the use of low energy hydrogen ion implantation for high efficiency crystalline silicon solar cells. The first quarterly report focuses on two tasks of this program: (1) an examination of the effects of low energy hydrogen implants on surface recombination speed; and (2) an examination of the effects of hydrogen on silicon regrowth and diffusion in silicon. The first part of the project focussed on the measurement of surface properties of hydrogen implanted silicon. Low energy hydrogen ions when bombarded on the silicon surface will create structural damage at the surface, deactivate dopants and introduce recombination centers. At the same time the electrically active centers such as dangling bonds will be passivated by these hydrogen ions. Thus hydrogen is expected to alter properties such as the surface recombination velocity, dopant profiles on the emitter, etc. In this report the surface recombination velocity of a hydrogen emplanted emitter was measured.

  19. Low Energy, Low Emissions: Sulfur Dioxide; Nitrogen Oxides, and Carbon Dioxide in Western Europe.

    ERIC Educational Resources Information Center

    Alcamo, Joseph; De Vries, Bert

    1992-01-01

    Links proposed low-energy scenarios for different Western European countries with the amount of pollutants that may result from these scenarios. Sulfur dioxide, nitrogen oxide, and carbon dioxide emissions are calculated for the 10 countries for which low-energy scenarios are available, resulting in reductions of 54%, 37%, and 40%, respectively.…

  20. Use of low-energy hydrogen ion implants in high-efficiency crystalline-silicon solar cells

    NASA Technical Reports Server (NTRS)

    Fonash, S. J.; Sigh, R.; Mu, H. C.

    1986-01-01

    The use of low-energy hydrogen implants in the fabrication of high-efficiency crystalline silicon solar cells was investigated. Low-energy hydrogen implants result in hydrogen-caused effects in all three regions of a solar cell: emitter, space charge region, and base. In web, Czochralski (Cz), and floating zone (Fz) material, low-energy hydrogen implants reduced surface recombination velocity. In all three, the implants passivated the space charge region recombination centers. It was established that hydrogen implants can alter the diffusion properties of ion-implanted boron in silicon, but not ion-implated arsenic.

  1. Detection of changes in DNA methylation induced by low-energy ion implantation in Arabidopsis thaliana.

    PubMed

    Yu, Haichan; Zhao, Jin; Xu, Jing; Li, Xiaoqu; Zhang, Fengshou; Wang, Yugang; Carr, Christopher; Zhang, Jun; Zhang, Genfa

    2011-05-01

    This study evaluated changes in DNA methylation in Arabidopsis thaliana plants grown from seeds implanted with low-energy N(+) and Ar(+) ions. Methylation-sensitive amplified polymorphism (MSAP) testing revealed altered DNA methylation patterns after ion implantation at doses of 1 × 10(14) to 1 × 10(16) ions/cm(2). Comparison of the MSAP electrophoretic profiles revealed nine types of polymorphisms in ion-implanted seedlings relative to control seedlings, among which four represented methylation events, three represented demethylation events, and the methylation status of two was uncertain. The diversity of plant DNA methylation was increased by low-energy ion implantation. At the same time, total genomic DNA methylation levels at CCGG sites were unchanged by ion implantation. Moreover, a comparison of polymorphisms seen in N(+) ion-implanted, Ar(+) ion-implanted, and control DNA demonstrated that the species of incident ion influenced the resulting DNA methylation pattern. Sequencing of eight isolated fragments that showed different changing patterns in implanted plants allowed their mapping onto variable regions on one or more of the five Arabidopsis chromosomes; these segments included protein-coding genes, transposon and repeat DNA sequence. A further sodium bisulfite sequencing of three fragments also displayed alterations in methylation among either different types or doses of incident ions. Possible causes for the changes in methylation are discussed.

  2. The point mutation induced by the low-energy N+ ion implantation in impatiens balsamine genome.

    PubMed

    Gao, W J; Su, J X; Xie, L; Deng, C L; Zhang, T; Lu, L D

    2012-10-01

    To investigate the effect of genome mutations induced by low energy ions implantation in higher plants, genome mutation of Impatiens balsamine mutant induced by low energy N+ ion implantation were analyzed by the RAPD, ISSR and genome sequence. Six out of the 121 ISSR primers and 6 out of the 135 RAPD primers showed that polymorphism ratios between mutants and wild type were 4.96% and 2.89%, respectively. Sequence analysis revealed that base deletions, insertions, and substitutions were observed in the mutant genome comparable to wild type. N+ induced point mutations were mostly base substitution (77.4%), no duplication, long fragments insertions and deletions was found. In all point mutation, adenine (A) was most sensitive to the N+ ion implantation in impatiens. The transition was mainly A --> guanine (G) (15.90%) and thymine (T) --> cytosine (C) (12.55%). Transversion happened in A <--> T (16.74%), which much higher than C <--> G(5.02%), G <--> T(6.69%), A <--> C (7.11%) bases. These findings indicate that low energy ions being a useful mutagen were mostly cause the point mutation in impatiens.

  3. Sources and transport systems for low energy extreme of ion implantation

    SciTech Connect

    Hershcovitch, A.; Batalin, V.A.; Bugaev, A.S.; Gushenets, V.I.; Alexeyenko, O.; Gurkova, E.; Johnson, B.M.; Kolomiets, A.A.; Kropachev, G.N.; Kuibeda, R.P.; Kulevoy, T.V.; Masunov, E.S.; Oks, E.M.; Pershin, V.I.; Polozov, S.M.; Poole, H.J.; Seleznev, D.N.; Storozhenko, P.A.; Vizir, A.; Svarovski, A.Ya.; Yakushin, P.; Yushkov, G.Yu.

    2010-06-06

    For the past seven years a joint research and development effort focusing on the design of steady state, intense ion sources has been in progress with the ultimate goal being to meet the two, energy extreme range needs of mega-electron-volt and 100's of electron-volt ion implanters. However, since the last Fortier is low energy ion implantation, focus of the endeavor has shifted to low energy ion implantation. For boron cluster source development, we started with molecular ions of decaborane (B{sub 10}H{sub 14}), octadecaborane (B{sub 18}H{sub 22}), and presently our focus is on carborane (C{sub 2}B{sub 10}H{sub 12}) ions developing methods for mitigating graphite deposition. Simultaneously, we are developing a pure boron ion source (without a working gas) that can form the basis for a novel, more efficient, plasma immersion source. Our Calutron-Berna ion source was converted into a universal source capable of switching between generating molecular phosphorous P{sub 4}{sup +}, high charge state ions, as well as other types of ions. Additionally, we have developed transport systems capable of transporting a very large variety of ion species, and simulations of a novel gasless/plasmaless ion beam deceleration method were also performed.

  4. Room temperature diamond-like carbon coatings produced by low energy ion implantation

    NASA Astrophysics Data System (ADS)

    Markwitz, A.; Mohr, B.; Leveneur, J.

    2014-07-01

    Nanometre-smooth diamond-like carbon coatings (DLC) were produced at room temperature with ion implantation using 6 kV C3Hy+ ion beams. Ion beam analysis measurements showed that the coatings contain no heavy Z impurities at the level of 100 ppm, have a homogeneous stoichiometry in depth and a hydrogen concentration of typically 25 at.%. High resolution TEM analysis showed high quality and atomically flat amorphous coatings on wafer silicon. Combined TEM and RBS analysis gave a coating density of 3.25 g cm-3. Raman spectroscopy was performed to probe for sp2/sp3 bonds in the coatings. The results indicate that low energy ion implantation with 6 kV produces hydrogenated amorphous carbon coatings with a sp3 content of about 20%. Results highlight the opportunity of developing room temperature DLC coatings with ion beam technology for industrial applications.

  5. DLTS of low-energy hydrogen ion implanted n-Si

    NASA Astrophysics Data System (ADS)

    Deenapanray, Prakash N. K.

    2003-12-01

    We have used deep level transient spectroscopy and capacitance-voltage measurements to study the influence of low-energy hydrogen ion implantation on the creation of defects in n-Si. In particular, we have studied the ion fluence dependence of the free carrier compensation at room temperature, and we have measured the generation of VO-H complex and VP-pair in ion implanted samples. The 7.5 keV H ions created defects in the top 0.3 μm of samples, which resulted in carrier compensation to depths exceeding 1 μm. This effect is not due to defects created by ion channeling but is rather due to the migration of defects as demonstrated using binary collision code MARLOWE.

  6. Plasma-assisted low energy N2 implant for Vfb tuning of Ge gate stacks

    NASA Astrophysics Data System (ADS)

    Kothari, Shraddha; Joishi, Chandan; Nejad, Hasan; Variam, Naushad; Lodha, Saurabh

    2016-08-01

    This work reports Vfb tuning of TiN/HfO2 gate stacks on Ge using low energy plasma-assisted doping with N2 without significant impact on gate capacitance and gate/channel interface trap densities. As required for multi-VT Ge p-FinFETs, controlled change in effective work function up to 180 mV from the near midgap to the near valence band edge of Ge is demonstrated by varying implant dose and energy. Unlike Si gate stacks, increased gate leakage in implanted Ge gate stacks is shown to result from traps created in the HfO2 layer during the implant and exposed to channel carriers due to a low band offset GeO2 interfacial layer (IL). Recovery of gate leakage is demonstrated by substituting GeO2 with an Al2O3 IL. Further, a simple physical model is proposed to extract the work function and oxide charge components of the change in Vfb for varying implant doses and energies.

  7. A novel mechanism of ultrathin SOI synthesis by extremely low-energy hot O+ implantation

    NASA Astrophysics Data System (ADS)

    Hoshino, Yasushi; Yachida, Gosuke; Inoue, Kodai; Toyohara, Taiga; Nakata, Jyoji

    2016-08-01

    Extremely low-energy oxygen implantations at 10 keV in silicon were challengingly performed to directly synthesize ultrathin silicon-on-insulator (SOI) structure separated by a buried oxide (BOX) layer. We quantitatively investigated the optimum condition and the formation mechanism of homogeneous and continuous stoichiometric SOI/BOX structure. In this study, oxygen ions were implanted into Si(0 0 1) substrates with keeping the temperatures at 500, 800, and 1000 °C with ion-fluences from 0.5 to 2.0× {{10}17} ions cm-2. These samples were then postannealed at high temperatures from 950 to 1150 °C in Ar ambient for several hours. We found that ultrathin stoichiometric SOI/BOX structure with less than 20 nm thick was synthesized by oxygen implantation with an ion dose of 1.0× {{10}17} ions cm-2 from 500 °C to 800 °C followed by annealing at a significantly low temperature of 1050 °C for 5 h. According to the RBS-channeling analysis, the crystallinity was excellent as quality as that of the SOI structure formed by a wafer-bonding method. We found that the BOX layer was finally formed around the deeper end of the oxygen distribution in the as-implanted sample, though the depth of the BOX formation was much deeper than the projected range of oxygen and the damage peak of silicon. The formation process of the SOI/BOX structure proposed so far could not be applicable to the present conditions for ultrathin SOI/BOX synthesis by extremely low-energy implantation followed by low-temperature annealing. We thus suggested a novel mechanism of the ultrathin SOI/BOX synthesis as follows. The mechanism during the thermal treatment was demonstrated that the recrystallization of the damaged Si layers induced by ion irradiation took place from the very surface with relatively less irradiation-damages toward deeper layers with sweeping interstitial oxygen atoms, and the condensed oxygen atoms finally synthesized the stoichiometric BOX layer.

  8. [Absorption spectrum study of HeLa cells treated with vacuum and low-energy ions implantation].

    PubMed

    Zhang, Feng-Qiu; Zhao, Yuan-Li; Ge, Xiang-Hong; Liu, Wei; Zhang, Guang-Shui; Qin, Guang-Yong

    2009-08-01

    Mineral oil was selected to protect HeLa cells from water evaporation during low-energy ions implantation in the present paper. Then, HeLa cells having been treated with vacuum and low-energy N+ ions implantation were used to collect ultraviolet absorption spectrum by spectrophotometer. Analytical results indicated that HeLa cells had some characteristic absorption peaks near 202 and 260 nm, respectively. And then the study also found: (1) The spectral intensity increased with the vacuum treatment time. In addition, the effect of vacuum on cellular spectrum was greater than that of mineral oil. (2) The influence of low energy N+ ions on absorption spectrum was far more than that of vacuum. (3) The spectral intensity increased with the implantation dose. According to these results, the effect of low-energy N+ ions implantation and vacuum on tumorous cells (HeLa cells), especially on the molecular configuration and component of tumorous cells (HeLa cells) was discussed. In a word, this study provides a basis for further research on the functionary mechanism of low-energy ions implantation on biomaterial.

  9. Incorporation of low energy activated nitrogen onto HOPG surface: Chemical states and thermal stability studies by in-situ XPS and Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Chandran, Maneesh; Shasha, Michal; Michaelson, Shaul; Hoffman, Alon

    2016-09-01

    In this paper we report the chemical states analysis of activated nitrogen incorporated highly oriented pyrolytic graphite (HOPG) surface under well-controlled conditions. Nitrogen incorporation is carried out by two different processes: an indirect RF nitrogen plasma and low energy (1 keV) N2+ implantation. Bonding configuration, concentration and thermal stability of the incorporated nitrogen species by aforesaid processes are systematically compared by in-situ X-ray photoelectron spectroscopy (XPS). Relatively large concentration of nitrogen is incorporated onto RF nitride HOPG surface (16.2 at.%), compared to N2+ implanted HOPG surface (7.7 at.%). The evolution of N 1s components (N1, N2, N3) with annealing temperature is comprehensively discussed, which indicates that the formation and reorganization of local chemical bonding states are determined by the process of nitridation and not by the prior chemical conditioning (i.e., amorphization or hydrogenation) of the HOPG surface. A combined XPS and Raman spectroscopy studies revealed that N2+ implantation process resulted in a high level of defects to the HOPG surface, which cannot be annealed-out by heat treatment up to 1000 °C. On the other hand, the RF nitrogen plasma process did not produce a high level of surface defects, while incorporating nearly the same amount of stable nitrogen species.

  10. Monolithic integration of multiple-emission-wavelength laser diodes using low-energy ion implantation

    NASA Astrophysics Data System (ADS)

    Aimez, Vincent; Paquette, Michel; Beauvais, Jacques; Beerens, Jean; Poole, Philip J.; Charbonneau, N. Sylvain

    1998-09-01

    A monolithic optoelectronic chip containing multiple emission wavelength laser diodes has been developed. The semiconductor quantum well lasers have Fabry-Perot cavities of 500 micrometers in length. Electrical insulation between individual integrated devices has been achieved by wet etching the top contact layer and by a lift-off of the surface metal contact between the different lasers. The electroluminescence peak emission spectra of the integrated laser diodes has been shifted over a 25 nm range and 74 nm for discrete devices. Blueshifting of the emission wavelength has been achieved by quantum well intermixing using an industrial low energy ion implanter to generate point defects and a rapid thermal annealer to promote interdiffusion of the barrier and quantum well atoms during the recrystallization anneal. Phosphorus ions were implanted with an energy of 360 keV to precisely defined regions of the heterostructure with SiO2 serving as a masking material. Thus reference and intermixed regions were integrated on a single component. Integrated and discrete laser diodes have been assessed in terms of threshold currents and emission wavelengths.

  11. Creation of High-Yield Polyhydroxyalkanoates Engineered Strains by Low Energy Ion Implantation

    NASA Astrophysics Data System (ADS)

    Qian, Shiquan; Cheng, Ying; Zhu, Suwen; Cheng, Beijiu

    2008-12-01

    Polyhydroxyalkanoates (PHAs), as a candidate for biodegradable plastic materials, can be synthesized by numerous microorganisms. However, as its production cost is high in comparison with those of chemically synthesized plastics, a lot of research has been focused on the efficient production of PHAs using different methods. In the present study, the mutation effects of PHAs production in strain pCB4 were investigated with implantation of low energy ions. It was found that under the implantation conditions of 7.8 × 1014 N+/cm2 at 10 keV, a high-yield PHAs strain with high genetic stability was generated from many mutants. After optimizing its fermentation conditions, the biomass, PHAs concentration and PHAs content of pCBH4 reached 2.26 g/L, 1.81 g/L, and 80.08% respectively, whereas its wild type controls were about 1.24 g/L, 0.61 g/L, and 49.20%. Moreover, the main constituent of PHAs was identified as poly-3-hydroxybutyrates (PHB) in the mutant stain and the yield of this compound was increased up to 41.33% in contrast to that of 27.78% in the wild type strain.

  12. Doping of Graphene by Low-Energy Ion Beam Implantation: Structural, Electronic, and Transport Properties.

    PubMed

    Willke, Philip; Amani, Julian A; Sinterhauf, Anna; Thakur, Sangeeta; Kotzott, Thomas; Druga, Thomas; Weikert, Steffen; Maiti, Kalobaran; Hofsäss, Hans; Wenderoth, Martin

    2015-08-12

    We investigate the structural, electronic, and transport properties of substitutional defects in SiC-graphene by means of scanning tunneling microscopy and magnetotransport experiments. Using ion incorporation via ultralow energy ion implantation, the influence of different ion species (boron, nitrogen, and carbon) can directly be compared. While boron and nitrogen atoms lead to an effective doping of the graphene sheet and can reduce or raise the position of the Fermi level, respectively, (12)C(+) carbon ions are used to study possible defect creation by the bombardment. For low-temperature transport, the implantation leads to an increase in resistance and a decrease in mobility in contrast to undoped samples. For undoped samples, we observe in high magnetic fields a positive magnetoresistance that changes to negative for the doped samples, especially for (11)B(+)- and (12)C(+)-ions. We conclude that the conductivity of the graphene sheet is lowered by impurity atoms and especially by lattice defects, because they result in weak localization effects at low temperatures.

  13. Surface engineering of a Zr-based bulk metallic glass with low energy Ar- or Ca-ion implantation.

    PubMed

    Huang, Lu; Zhu, Chao; Muntele, Claudiu I; Zhang, Tao; Liaw, Peter K; He, Wei

    2015-02-01

    In the present study, low energy ion implantation was employed to engineer the surface of a Zr-based bulk metallic glass (BMG), aiming at improving the biocompatibility and imparting bioactivity to the surface. Ca- or Ar-ions were implanted at 10 or 50 keV at a fluence of 8 × 10(15)ions/cm(2) to (Zr0.55Al0.10Ni0.05Cu0.30)99Y1 (at.%) BMG. The effects of ion implantation on material properties and subsequent cellular responses were investigated. Both Ar- and Ca-ion implantations were suggested to induce atom displacements on the surfaces according to the Monte-Carlo simulation. The change of atomic environment of Zr in the surface regions as implied by the alteration in X-ray absorption measurements at Zr K-edge. X-ray photoelectron spectroscopy revealed that the ion implantation process has modified the surface chemical compositions and indicated the presence of Ca after Ca-ion implantation. The surface nanohardness has been enhanced by implantation of either ion species, with Ca-ion implantation showing more prominent effect. The BMG surfaces were altered to be more hydrophobic after ion implantation, which can be attributed to the reduced amount of hydroxyl groups on the implanted surfaces. Higher numbers of adherent cells were found on Ar- and Ca-ion implanted samples, while more pronounced cell adhesion was observed on Ca-ion implanted substrates. The low energy ion implantation resulted in concurrent modifications in atomic structure, nanohardness, surface chemistry, hydrophobicity, and cell behavior on the surface of the Zr-based BMG, which were proposed to be mutually correlated with each other.

  14. A modified broad beam ion source for low-energy hydrogen implantation

    NASA Astrophysics Data System (ADS)

    Otte, K.; Schindler, A.; Bigl, F.; Schlemm, H.

    1998-03-01

    A modified broad beam ion source for low-energy hydrogen ion implantation of semiconductors is described. Based on a Kaufman type ion source two different solutions are presented: (a) an ion source with an extraction system consisting of two molybdenum grids with a low gas flow conductance reworked for hydrogen operation, and (b) a ten-grid mass separating ion beam system which enables the mass selection of H+, H2+, and H3+. The ion energy could be set in the range of 200-500 eV with a current density reaching from 1 to 100 μA/cm2. It is shown that at higher pressure the main ion created in the ion source is H3+ due to ion-molecule processes, whereas at lower pressure only H2+ and H+ are produced. Special consideration is given to the ion beam analysis of the two grid ion source operating in the 10-3 mbar range allowing to explain the different peak structures by the potential distribution across the ion source and different charge transfer processes. In addition, the analysis reveals neutral and ionized collision products in the ion beam. The ten-grid mass separating ion source could be operated in the 10-4 mbar range resulting in a nearly collision free ion beam which permits the generation of a mass separated hydrogen ion beam.

  15. Optimization of L(+)-Lactic Acid Fermentation Without Neutralisation of Rhizopus Oryzae Mutant RK02 by Low-Energy Ion Implantation

    NASA Astrophysics Data System (ADS)

    Li, Wen; Wang, Tao; Yang, Yingge; Liu, Dan; Fan, Yonghong; Wang, Dongmei; Yang, Qian; Yao, Jianming; Zheng, Zhiming; Yu, Zengliang

    2008-04-01

    In order to get an industrial strain which can yield a high concentration of lactic acid for ISPR (in situ product removal), the original strain Rhizopus oryzae RE3303 was mutated by low-energy ion beam implantation. A mutant RK02 was screened, and the factors such as the substrate concentration, nitrogen source concentration, inoculum size, seed age, aeration and temperature that affect the production of lactic acid were studied in detail. Under optimal conditions, the maximum concentration of L(+)-lactic acid reached 34.85 g/L after 30 h shake-flask cultivation without adding any neutralisation (5% Glucose added), which was a 146% increase in lactic acid production after ion implantation compared with the original strain. It was also shown that RK02 can be used in ISPR to reduce the number of times of separation.

  16. Optimization of L(+)-Lactic Acid Production from Xylose with Rhizopus Oryzae Mutant RLC41-6 Breeding by Low-Energy Ion Implantation

    NASA Astrophysics Data System (ADS)

    Yang, Yingge; Fan, Yonghong; Li, Wen; Wang, Dongmei; Wu, Yuejin; Zheng, Zhiming; Yu, Zengliang

    2007-10-01

    In order to obtain an industrial strain with a higher L(+)-lactic acid yield, the strain Rhizopus oryzae PW352 was mutated by means of nitrogen ion beam implantation and the mutant strain Rhizopus oryzae RLC41-6 was obtained. An experimental finding was made in surprise that Rhizopus oryzae mutant RLC41-6 is not only an L(+)-lactic acid producer from corn starch but also an efficient producer of L(+)-lactic acid from xylose. Under optimal conditions, the production of L(+)-lactic acid from 100 g/L xylose reached 77.39 g/L after 144 h fed-batch fermentation. A high mutation rate and a wide mutation spectrum of low-energy ion implantation were observed in the experiment.

  17. Tribological properties of nitrogen implanted and boron implanted steels

    SciTech Connect

    Kern, K.T.; Walter, K.C.; Griffin, A.J. Jr.; Kung, H.; Lu, Y.; Nastasi, M.; Tesmer, J.R.; Fayeulle, S.

    1996-06-01

    Samples of a steel with high chrome content was implanted separately with 75 keV nitrogen ions and with 75 keV boron ions. Implanted doses of each ion species were 2-, 4-, and 8 {times} 10{sup 17}/cm{sup 2}. Retained doses were measured using resonant non-Rutherford Backscattering Spectrometry. Tribological properties were determined using a pin-on-disk test with a 6-mm diameter ruby pin with a velocity of 0.94 m/min. Testing was done at 10% humidity with a load of 377 g. Wear rate and coefficient of friction were determined from these tests. While reduction in the wear rate for nitrogen implanted materials was observed, greater reduction (more than an order of magnitude) was observed for boron implanted materials. In addition, reduction in the coefficient of friction for high-dose boron implanted materials was observed. Nano-indentation revealed a hardened layer near the surface of the material. Results from grazing incidence x-ray diffraction suggest the formation of Fe{sub 2}N and Fe{sub 3}N in the nitrogen implanted materials and Fe{sub 3}B in the boron implanted materials. Results from transmission electron microscopy will be presented.

  18. Cracks and blisters formed close to a silicon wafer surface by He-H co-implantation at low energy

    SciTech Connect

    Cherkashin, N. Darras, F.-X.; Claverie, A.; Daghbouj, N.; Fnaiech, M.

    2015-12-28

    We have studied the effect of reducing the implantation energy towards low keV values on the areal density of He and H atoms stored within populations of blister cavities formed by co-implantation of the same fluence of He then H ions into Si(001) wafers and annealing. Using a variety of experimental techniques, we have measured blister heights and depth from the surface, diameter, areal density of the cracks from which they originate as functions of implantation energy and fluence. We show that there is a direct correlation between the diameters of the cracks and the heights of the associated blisters. This correlation only depends on the implantation energy, i.e., only on the depth at which the cracks are located. Using finite element method modeling, we infer the pressure inside the blister cavities from the elastic deformations they generate, i.e., from the height of the blisters. From this, we demonstrate that the gas pressure within a blister only depends on the diameter of the associated crack and not on its depth position and derive an analytical expression relating these parameters. Relating the pressure inside a blister to the respective concentrations of gas molecules it contains, we deduce the areal densities of He and H atoms contained within the populations of blisters. After low-energy implantations (8 keV He{sup +}, 3 keV H{sup +}), all the implanted He and H atoms contribute to the formation of the blisters. There is no measurable exo-diffusion of any of the implanted gases, in contrast to what was assumed at the state of the art to explain the failure of the Smart-Cut technology when using very low energy ion implantation for the fabrication of ultra-thin layers. Alternative explanations must be investigated.

  19. Cracks and blisters formed close to a silicon wafer surface by He-H co-implantation at low energy

    NASA Astrophysics Data System (ADS)

    Cherkashin, N.; Daghbouj, N.; Darras, F.-X.; Fnaiech, M.; Claverie, A.

    2015-12-01

    We have studied the effect of reducing the implantation energy towards low keV values on the areal density of He and H atoms stored within populations of blister cavities formed by co-implantation of the same fluence of He then H ions into Si(001) wafers and annealing. Using a variety of experimental techniques, we have measured blister heights and depth from the surface, diameter, areal density of the cracks from which they originate as functions of implantation energy and fluence. We show that there is a direct correlation between the diameters of the cracks and the heights of the associated blisters. This correlation only depends on the implantation energy, i.e., only on the depth at which the cracks are located. Using finite element method modeling, we infer the pressure inside the blister cavities from the elastic deformations they generate, i.e., from the height of the blisters. From this, we demonstrate that the gas pressure within a blister only depends on the diameter of the associated crack and not on its depth position and derive an analytical expression relating these parameters. Relating the pressure inside a blister to the respective concentrations of gas molecules it contains, we deduce the areal densities of He and H atoms contained within the populations of blisters. After low-energy implantations (8 keV He+, 3 keV H+), all the implanted He and H atoms contribute to the formation of the blisters. There is no measurable exo-diffusion of any of the implanted gases, in contrast to what was assumed at the state of the art to explain the failure of the Smart-Cut technology when using very low energy ion implantation for the fabrication of ultra-thin layers. Alternative explanations must be investigated.

  20. Tribological characteristics of nitrogen (N+) implanted iron

    NASA Technical Reports Server (NTRS)

    Jones, W. R.; Ferrante, J.

    1982-01-01

    The effect of implantation of nitrogen ions (1.5 MeV) on the friction and wear characteristics of pure ion sliding against M-50 steel (unimplanted) was studied in a pin-on-disk sliding friction apparatus. Test conditions included room temperature (25 C), a dry air atmosphere, a load of 1/2 kg (4.9 N), sliding velocities of 0.043 to 0.078 m/sec (15 to 25 rpm), a pure hydrocarbon lubricant (n-hexadecane), or a U.S.P. mineral oil and nitrogen ion implantation doses of 5x10 to the 15th power and 5x10 to the 17th power ions/sq cm. No differences in wear rates were observed in the low dose experiments. In the high dose experiments, small reductions in initial (40 percent) and steady state (20 percent) wear rates were observed for nitrogen implanted iron riders as compared with unimplanted controls. No differences in average friction coefficients were noted for either dose. Auger electron spectroscopy combined with argon ion bombardment revealed a subsurface Gaussian nitrogen distribution with a maximum concentration of 6 atomic percent at a depth of 0.8 microns. Similar analysis within the wear scar of an implanted rider after 20 microns of wear yielded only background nitrogen concentration. No inward migration of nitrogen ions was observed.

  1. Tribological characteristics of nitrogen (N+) implanted iron

    NASA Technical Reports Server (NTRS)

    Jones, W. R., Jr.; Ferrante, J.

    1983-01-01

    The effect of implantation of nitrogen ions (1.5 MeV) on the friction and wear characteristics of pure ion sliding against M-50 steel (unimplanted) was studied in a pin-on-disk sliding friction apparatus. Test conditions included room temperature (25 C), a dry air atmosphere, a load of 1/2 kg (4.9 N), sliding velocities of 0.043 to 0.078 m/sec (15 to 25 rpm), a pure hydrocarbon lubricant (n-hexadecane), or a U.S.P. mineral oil and nitrogen ion implantation doses of 5x10 to the 15th power and 5x10 to the 17th power ions/sq cm. No differences in wear rates were observed in the low dose experiments. In the high dose experiments, small reductions in initial (40 percent) and steady state (20 percent) wear rates were observed for nitrogen implanted iron riders as compared with unimplanted controls. No differences in average friction coefficients were noted for either dose. Auger electron spectroscopy combined with argon ion bombardment revealed a subsurface Gaussian nitrogen distribution with a maximum concentration of 6 atomic percent at a depth of 0.8 microns. Similar analysis within the wear scar of an implanted rider after 20 microns of wear yielded only background nitrogen concentration. No inward migration of nitrogen ions was observed. Previously announced in STAR as N82-24322

  2. Preliminary Studies on Base Substitutions and Repair of DNA Mismatch Damage Stimulated by Low Energy N+ Ion Beam Implantation in Escherichia coli

    NASA Astrophysics Data System (ADS)

    Xie, Chuan-xiao; Guo, Jin-hua; Cheng, Bei-jiu; Yu, Zeng-liang

    2003-02-01

    Ever since the low energy N+ ion beam has been accepted that the mutation effects of ionizing radiation are attributed mainly to direct or indirect damage to DNA. Evidences based on naked DNA irradiation in support of a mutation spectrum appears to be consistent, but direct proof of such results in vivo are limited. Using mutS, dam and/or dcm defective Eschericha coli mutator strains, an preliminary experimental system on induction of in vivo mutation spectra of low energy N+ ion beam has been established in this study. It was observed that the mutation rates of rifampicin resistance induced by N+ implantation were quite high, ranging from 9.2 × 10-8 to 4.9 × 10-5 at the dosage of 5.2 × 1014 ions/cm2. Strains all had more than 90-fold higher mutation rate than its spontaneous mutation rate determined by this method. It reveals that base substitutions involve in induction of mutation of low energy nitrogen ion beam implantation. The mutation rates of mutator strains were nearly 500-fold (GM2929), 400-fold (GM5864) and 6-fold larger than that of AB1157. The GM2929 and GM5864 both lose the ability of repair DNA mismatch damage by virtue of both dam and dcm pathways defective (GM2929) or failing to assemble the repair complex (GM5864) respectively. It may explain the both strains had a similar higher mutation rate than GM124 did. It indicated that DNA cytosine methylase might play an important role in mismatch repair of DNA damage induced by N+ implantation. The further related research were also discussed.

  3. Improved thermostable α-amylase activity of Bacillus amyloliquefaciens by low-energy ion implantation.

    PubMed

    Li, X Y; Zhang, J L; Zhu, S W

    2011-09-23

    Thermostable α-amylase is of great importance in the starch fermentation industry; it is extensively used in the manufacture of beverages, baby foods, medicines, and pharmaceuticals. Bacillus amyloliquefaciens produces thermostable α-amylase; however, production of thermostable α-amylase is limited. Ion-beam implantation is an effective method for mutation breeding in microbes. We conducted ion-beam implantation experiments using two different ions, Ar(+) and N(+), to determine the survival rate of and dose effect on a high α-amylase activity strain of B. amyloliquefaciens that had been isolated from soil samples. N(+) implantation resulted in a higher survival rate than Ar(+) implantation. The optimum implantation dose was 2.08 × 10(15) ions/cm(2). Under this implantation condition, we obtained a thermally and genetically stable mutant α-amylase strain (RL-1) with high enzyme activity for degrading α-amylase. Compared to the parental strain (RL), the RL-1 strain had a 57.1% increase in α-amylase activity. We conclude that ion implantation in B. amyloliquefaciens can produce strains with increased production of thermostable α-amylase.

  4. Fabrication and characterization of a co-planar detector in diamond for low energy single ion implantation

    SciTech Connect

    Abraham, John Bishoy Sam; Pacheco, Jose L.; Aguirre, Brandon Adrian; Vizkelethy, Gyorgy; Bielejec, Edward S.

    2016-08-09

    We demonstrate low energy single ion detection using a co-planar detector fabricated on a diamond substrate and characterized by ion beam induced charge collection. Histograms are taken with low fluence ion pulses illustrating quantized ion detection down to a single ion with a signal-to-noise ratio of approximately 10. We anticipate that this detection technique can serve as a basis to optimize the yield of single color centers in diamond. In conclusion, the ability to count ions into a diamond substrate is expected to reduce the uncertainty in the yield of color center formation by removing Poisson statistics from the implantation process.

  5. Fabrication and characterization of a co-planar detector in diamond for low energy single ion implantation

    NASA Astrophysics Data System (ADS)

    Abraham, J. B. S.; Aguirre, B. A.; Pacheco, J. L.; Vizkelethy, G.; Bielejec, E.

    2016-08-01

    We demonstrate low energy single ion detection using a co-planar detector fabricated on a diamond substrate and characterized by ion beam induced charge collection. Histograms are taken with low fluence ion pulses illustrating quantized ion detection down to a single ion with a signal-to-noise ratio of approximately 10. We anticipate that this detection technique can serve as a basis to optimize the yield of single color centers in diamond. The ability to count ions into a diamond substrate is expected to reduce the uncertainty in the yield of color center formation by removing Poisson statistics from the implantation process.

  6. Breeding of D(-)-lactic acid high producing strain by low-energy ion implantation and preliminary analysis of related metabolism.

    PubMed

    Xu, Ting-Ting; Bai, Zhong-Zhong; Wang, Li-Juan; He, Bing-Fang

    2010-01-01

    The low-energy nitrogen ion beam implantation technique was used in the breeding of mutant D(-)-lactic-acid-producing strains. The wild strain Sporolactobacillus sp. DX12 was mutated by an N(+) ion beam with energy of 10keV and doses ranging from 0.4 x 10(15) to 6.60 x 10(15) ions/cm(2). Combined with an efficient screening method, an efficient mutant Y2-8 was selected after two times N(+) ion beam implantation. By using the mutant Y2-8, 121.6g/l of D-lactic acid was produced with the molar yields of 162.1% to the glucose. The yield of D-lactic acid by strain Y2-8 was 198.8% higher than the wild strain. Determination of anaerobic metabolism by Biolog MT2 was used to analyze the activities of the concerned enzymes in the lactic acid metabolic pathway. The results showed that the activities of the key enzymes responded on the substrates such as 6-phosphofructokinase, pyruvate kinase, and D-lactate dehydrogenase were considerably higher in the mutants than the wild strain. These might be affected by ion beam implantation.

  7. Effects of low-energy argon ion implantation on the dynamic organization of the actin cytoskeleton during maize pollen germination.

    PubMed

    Deng, F; Zhu, S W; Wu, L J; Cheng, B J

    2010-04-27

    The relationship between pollen germination and the dynamic organization of the actin cytoskeleton during pollen germination is a central theme in plant reproductive biology research. Maize (Zea mays) pollen grains were implanted with 30 keV argon ion (Ar(+)) beams at doses ranging from 0.78 x 10(15) to 13 x 10(15) ions/cm(2). The effects of low-energy ion implantation on pollen germination viability and the dynamic organization of the actin cytoskeleton during pollen germination were studied using confocal laser scanning microscopy. Maize pollen germination rate increased remarkably with Ar(+) dose, in the range from 3.9 x 10(15) to 6.5 x 10(15) ions/cm(2); the germination rate peaked at an Ar(+) dose of 5.2 x 10(15) ions/cm(2). When the implantation dose exceeded 7.8 x 10(15) ions/cm(2), the rate of pollen germination decreased sharply. The actin filaments assembled in pollen grains implanted with 5.2 x 10(15) ions/cm(2) Ar(+) much earlier than in controls. The actin filaments organized as longer parallel bundles and extended into the emerging pollen tube in treated pollen grains, while they formed random and loose fine bundles and were gathered at the pollen aperture in the control. The reorganization of actin cytoskeleton in the pollen implanted with 9.1 x 10(15) ions/cm(2) Ar(+) was slower than in controls. There was a positive correlation between pollen germination and the dynamic organization of the actin cytoskeleton during pollen germination. Ion implantation into pollen did not cause changes in the polarization of actin filaments and organelle dynamics in the pollen tubes. The effects of Ar(+) implantation on pollen germination could be mediated by changes in the polymerization and rearrangement of actin polymers.

  8. Shallow nitrogen ion implantation: Evolution of chemical state and defect structure in titanium

    NASA Astrophysics Data System (ADS)

    Manojkumar, P. A.; Chirayath, V. A.; Balamurugan, A. K.; Krishna, Nanda Gopala; Ilango, S.; Kamruddin, M.; Amarendra, G.; Tyagi, A. K.; Raj, Baldev

    2016-09-01

    Evolution of chemical states and defect structure in titanium during low energy nitrogen ion implantation by Plasma Immersion Ion Implantation (PIII) process is studied. The underlying process of chemical state evolution is investigated using secondary ion mass spectrometry and X-ray photoelectron spectroscopy. The implantation induced defect structure evolution as a function of dose is elucidated using variable energy positron annihilation Doppler broadening spectroscopy (PAS) and the results were corroborated with chemical state. Formation of 3 layers of defect state was modeled to fit PAS results.

  9. Nitrogen ion implantation into various materials using 28 GHz electron cyclotron resonance ion source.

    PubMed

    Shin, Chang Seouk; Lee, Byoung-Seob; Choi, Seyong; Yoon, Jang-Hee; Kim, Hyun Gyu; Ok, Jung-Woo; Park, Jin Yong; Kim, Seong Jun; Bahng, Jungbae; Hong, Jonggi; Lee, Seung Wook; Won, Mi-Sook

    2016-02-01

    The installation of the 28 GHz electron cyclotron resonance ion source (ECRIS) ion implantation beamline was recently completed at the Korea Basic Science Institute. The apparatus contains a beam monitoring system and a sample holder for the ion implantation process. The new implantation system can function as a multipurpose tool since it can implant a variety of ions, ranging hydrogen to uranium, into different materials with precise control and with implantation areas as large as 1-10 mm(2). The implantation chamber was designed to measure the beam properties with a diagnostic system as well as to perform ion implantation with an in situ system including a mass spectrometer. This advanced implantation system can be employed in novel applications, including the production of a variety of new materials such as metals, polymers, and ceramics and the irradiation testing and fabrication of structural and functional materials to be used in future nuclear fusion reactors. In this investigation, the first nitrogen ion implantation experiments were conducted using the new system. The 28 GHz ECRIS implanted low-energy, multi-charged nitrogen ions into copper, zinc, and cobalt substrates, and the ion implantation depth profiles were obtained. SRIM 2013 code was used to calculate the profiles under identical conditions, and the experimental and simulation results are presented and compared in this report. The depths and ranges of the ion distributions in the experimental and simulation results agree closely and demonstrate that the new system will enable the treatment of various substrates for advanced materials research.

  10. Nitrogen ion implantation into various materials using 28 GHz electron cyclotron resonance ion source

    NASA Astrophysics Data System (ADS)

    Shin, Chang Seouk; Lee, Byoung-Seob; Choi, Seyong; Yoon, Jang-Hee; Kim, Hyun Gyu; Ok, Jung-Woo; Park, Jin Yong; Kim, Seong Jun; Bahng, Jungbae; Hong, Jonggi; Lee, Seung Wook; Won, Mi-Sook

    2016-02-01

    The installation of the 28 GHz electron cyclotron resonance ion source (ECRIS) ion implantation beamline was recently completed at the Korea Basic Science Institute. The apparatus contains a beam monitoring system and a sample holder for the ion implantation process. The new implantation system can function as a multipurpose tool since it can implant a variety of ions, ranging hydrogen to uranium, into different materials with precise control and with implantation areas as large as 1-10 mm2. The implantation chamber was designed to measure the beam properties with a diagnostic system as well as to perform ion implantation with an in situ system including a mass spectrometer. This advanced implantation system can be employed in novel applications, including the production of a variety of new materials such as metals, polymers, and ceramics and the irradiation testing and fabrication of structural and functional materials to be used in future nuclear fusion reactors. In this investigation, the first nitrogen ion implantation experiments were conducted using the new system. The 28 GHz ECRIS implanted low-energy, multi-charged nitrogen ions into copper, zinc, and cobalt substrates, and the ion implantation depth profiles were obtained. SRIM 2013 code was used to calculate the profiles under identical conditions, and the experimental and simulation results are presented and compared in this report. The depths and ranges of the ion distributions in the experimental and simulation results agree closely and demonstrate that the new system will enable the treatment of various substrates for advanced materials research.

  11. Nitrogen ion implantation into various materials using 28 GHz electron cyclotron resonance ion source

    SciTech Connect

    Shin, Chang Seouk; Lee, Byoung-Seob; Choi, Seyong; Yoon, Jang-Hee; Kim, Hyun Gyu; Ok, Jung-Woo; Park, Jin Yong; Kim, Seong Jun; Bahng, Jungbae; Hong, Jonggi; Won, Mi-Sook; Lee, Seung Wook

    2016-02-15

    The installation of the 28 GHz electron cyclotron resonance ion source (ECRIS) ion implantation beamline was recently completed at the Korea Basic Science Institute. The apparatus contains a beam monitoring system and a sample holder for the ion implantation process. The new implantation system can function as a multipurpose tool since it can implant a variety of ions, ranging hydrogen to uranium, into different materials with precise control and with implantation areas as large as 1–10 mm{sup 2}. The implantation chamber was designed to measure the beam properties with a diagnostic system as well as to perform ion implantation with an in situ system including a mass spectrometer. This advanced implantation system can be employed in novel applications, including the production of a variety of new materials such as metals, polymers, and ceramics and the irradiation testing and fabrication of structural and functional materials to be used in future nuclear fusion reactors. In this investigation, the first nitrogen ion implantation experiments were conducted using the new system. The 28 GHz ECRIS implanted low-energy, multi-charged nitrogen ions into copper, zinc, and cobalt substrates, and the ion implantation depth profiles were obtained. SRIM 2013 code was used to calculate the profiles under identical conditions, and the experimental and simulation results are presented and compared in this report. The depths and ranges of the ion distributions in the experimental and simulation results agree closely and demonstrate that the new system will enable the treatment of various substrates for advanced materials research.

  12. Breeding of Coenzyme Q10 Produced Strain by Low-Energy Ion Implantation and Optimization of Coenzyme Q10 Fermentation

    NASA Astrophysics Data System (ADS)

    Xu, Dejun; Zheng, Zhiming; Wang, Peng; Wang, Li; Yuan, Hang; Yu, Zengliang

    2008-12-01

    In order to increase the production efficiency of coenzyme Q10, the original strain Agrobacterium tumefaciens ATCC 4452 was mutated by means of Nitrogen ions implantation. A mutant strain, ATX 12, with high contents of coenzyme Q10 was selected. Subsequently, the conditions such as carbohydrate concentration, nitrogen source concentration, inoculum's size, seed age, aeration and temperature which might affect the production of CoQ10 were investigated in detail. Under optimal conditions, the maximum concentration of the intracellular CoQ10 reached 200.3 mg/L after 80 h fed-batch fermentation, about 245% increasing in CoQ10 production after ion implantation, compared to the original strain.

  13. Atomistic simulations of tungsten surface evolution under low-energy neon implantation

    NASA Astrophysics Data System (ADS)

    Backman, Marie; Hammond, Karl D.; Sefta, Faiza; Wirth, Brian D.

    2016-04-01

    Tungsten is a candidate material for the divertor of fusion reactors, where it will be subject to a high flux of particles coming from the fusion plasma as well as a significant heat load. Under helium plasma exposure in fusion-reactor-like conditions, a nanostructured morphology is known to form on the tungsten surface in certain temperature and incident energy ranges, although the formation mechanism is not fully established. A recent experimental study (Yajima et al 2013 Plasma Sci. Technol. 15 282-6) using neon or argon exposure did not produce similar nanostructure. This article presents molecular dynamics simulations of neon implantation in tungsten aimed at investigating the surface evolution and elucidating the role of noble gas mass in fuzz formation. In contrast to helium, neon impacts can sputter both tungsten and previously implanted neon atoms. The shorter range of neon ions, along with sputtering, limit the formation of large bubbles and likely prevents nanostructure formation.

  14. Low flux and low energy helium ion implantation into tungsten using a dedicated plasma source

    NASA Astrophysics Data System (ADS)

    Pentecoste, Lucile; Thomann, Anne-Lise; Melhem, Amer; Caillard, Amael; Cuynet, Stéphane; Lecas, Thomas; Brault, Pascal; Desgardin, Pierre; Barthe, Marie-France

    2016-09-01

    The aim of this work is to investigate the first stages of defect formation in tungsten (W) due to the accumulation of helium (He) atoms inside the crystal lattice. To reach the required implantation conditions, i.e. low He ion fluxes (1011-1014 ions.cm2.s-1) and kinetic energies below the W atom displacement threshold (about 500 eV for He+), an ICP source has been designed and connected to a diffusion chamber. Implantation conditions have been characterized by means of complementary diagnostics modified for measurements in this very low density helium plasma. It was shown that lowest ion fluxes could only be reached for the discharge working in capacitive mode either in α or γ regime. Special attention was paid to control the energy gained by the ions by acceleration through the sheath at the direct current biased substrate. At very low helium pressure, in α regime, a broad ion energy distribution function was evidenced, whereas a peak centered on the potential difference between the plasma and the biased substrate was found at higher pressures in the γ mode. Polycrystalline tungsten samples were exposed to the helium plasma in both regimes of the discharge and characterized by positron annihilation spectroscopy in order to detect the formed vacancy defects. It was found that W vacancies are able to be formed just by helium accumulation and that the same final implanted state is reached, whatever the operating mode of the capacitive discharge.

  15. The interdiffusion and solid-state reaction of low-energy copper ions implanted in silicon

    NASA Astrophysics Data System (ADS)

    Gao, Xing-Xin; Li, Tian-Jing; Li, Gong-Ping; Cao, Bo

    2008-06-01

    At room temperature, single-crystal silicon was implanted with Cu+ ions at an energy of 80 keV using two doses of 5 × 1015 and 1 × 1017 Cu+ cm-2. The samples were heat treated by conventional thermal annealing at different temperatures: 200 °C, 230 °C, 350 °C, 450 °C and 500 °C. The interdiffusion and solid-state reactions between the as-implanted samples and the as-annealed samples were investigated by means of Rutherford backscattering spectrometry (RBS) and X-ray diffraction (XRD). After annealing at 230 °C, the XRD results of the samples (subject to two different doses) showed formation of Cu3Si. According to RBS, the interdiffusion between Cu and Si atoms after annealing was very insignificant. The reason may be that the formation of Cu3Si after annealing at 230 °C suppressed further interdiffusion between Si and Cu atoms.

  16. Measurement of the spectra of low energy electrons resulting from Auger transitions induced by the annihilation of low energy positrons implanted at The Ag (100) surface

    NASA Astrophysics Data System (ADS)

    Shastry, Karthik; Joglekar, Prasad; Weiss, A. H.; Fazleev, N. G.

    2013-04-01

    A few percent of positrons bound to a solid surface annihilate with core electrons resulting in highly excited atoms containing core holes. These core holes may be filled in an auto-ionizing process in which a less tightly bound electron drops into the hole and the energy difference transferred to an outgoing "Auger electron." Because the core holes are created by annihilation and not impact it is possible to use very low energy positron beams to obtain annihilation induced Auger signals. The Auger signals so obtained have little or none of the large impact induced secondary electron background that interferes with measurements of the low energy Auger spectra obtained using the much higher incident energies necessary when using electron or photon beams. Here we present the results of measurements of the energy spectrum of low energy electrons emitted as a result of Positron Annihilation Induce Auger Electron Emission [1] from a clean Ag (100) surface. The measurements were performed using the University of Texas Arlington Time of Flight Positron Annihilation induced Auger Electron Spectrometer (T-O-F-PAES) System [2]. A strong double peak was observed at ˜35eV corresponding to the N2VV and N3VV Auger transitions in agreement with previous PAES studies [3].

  17. Making AlN(x) Tunnel Barriers Using a Low-Energy Nitrogen-Ion Beam

    NASA Technical Reports Server (NTRS)

    Kaul, Anupama; Kleinsasser, Alan; Bumble, Bruce; LeDuc, Henry; Lee, Karen

    2005-01-01

    A technique based on accelerating positive nitrogen ions onto an aluminum layer has been demonstrated to be effective in forming thin (<2 nm thick) layers of aluminum nitride (AlN(x)) for use as tunnel barriers in Nb/Al-AlN(x)/Nb superconductor/insulator/ superconductor (SIS) Josephson junctions. AlN(x) is the present material of choice for tunnel barriers because, to a degree greater than that of any other suitable material, it offers the required combination of low leakage current at high current density and greater thermal stability. While ultra-thin AlN films with good thickness and stoichiometry control are easily formed using techniques such as reactive molecular beam epitaxy and chemical vapor deposition, growth temperatures of 900 C are necessary for the dissociative adsorption of nitrogen from either nitrogen (N2) or ammonia (NH3). These growth temperatures are prohibitively high for the formation of tunnel barriers on Nb films because interfacial reactions at temperatures as low as 200 to 300 C degrade device properties. Heretofore, deposition by reactive sputtering and nitridation of thin Al layers with DC and RF nitrogen plasmas have been successfully used to form AlN barriers in SIS junctions. However, precise control over critical current density Jc has proven to be a challenge, as is attaining adequate process reproducibility from system to system. The present ion-beam technique is an alternative to the plasma or reactive sputtering techniques as it provides a highly controlled arrival of reactive species, independent of the electrical conditions of the substrate or vacuum chamber. Independent and accurate control of parameters such as ion energy, flux, species, and direction promises more precise control of film characteristics such as stoichiometry and thickness than is the case with typical plasma processes. In particular, the background pressure during ion-beam nitride growth is 2 or 3 orders of magnitude lower, minimizing the formation of

  18. DLC coating of interior surfaces of steel tubes by low energy plasma source ion implantation and deposition

    NASA Astrophysics Data System (ADS)

    Baba, K.; Hatada, R.; Flege, S.; Ensinger, W.

    2014-08-01

    The plasma source ion implantation (PSII) process can be used for the treatment of the interior surfaces of tubes. Typically, this is done with higher ion energies of 10 keV or more. The resulting film thickness and the properties of the DLC film usually show a dependence on position, i.e. the distance from the edge of the tube. In order to investigate whether this effect is also present with lower energies (and if so, to what extent), deposition was carried out at negative pulse voltages of -5 kV. A diamond-like carbon (DLC) film was deposited by using acetylene as the plasma gas. The substrate consisted of stainless steel tubes with an inner diameter of 20 mm and a length of 100 and 200 mm, respectively. The distribution of the thickness, film composition, structure, surface morphology and friction coefficient as a function of the position inside the tube were investigated. The results of this low energy treatment were compared with investigations which employed higher ion energies.

  19. Tribological performance of surfaces enhanced by texturing and nitrogen implantation

    NASA Astrophysics Data System (ADS)

    Liu, Derong; Zhang, Qi; Qin, Zhenbo; Luo, Qin; Wu, Zhong; Liu, Lei

    2016-02-01

    In this paper, a novel texturing technology by means of electrodepositon is introduced. Textured surface covered with small bumps with the average size of 28 μm in diameter and 10 μm in height was fabricated. The trough around the bumps acts as the pocket to trap the debris. The nitrogen implantation was used to enhance the tribological properties of textured surfaces. The effects of implanted energy and dose on the structures of coating and tribological performances of textured surfaces were studied. The results show that the formation of Cr2N or CrN depends on the implanted dose. After nitrogen ion implantation, the friction coefficient of textured surface reduced and the wear resistance of textured surface was improved. The wear resistance enhances with increase of implanted dose, and has little to do with implanted energy.

  20. Photonic integration of InGaAs-InGaAsP laser using low-energy-implantation-induced quantum well intermixing

    NASA Astrophysics Data System (ADS)

    Lim, Hwi Siong; Ooi, Boon Siew; Lam, Yee Loy; Chan, Yuen Chuen; Zhou, Yan; Aimez, Vincent; Beauvais, Jacques; Beerens, Jean

    1999-11-01

    Neutral impurity induced quantum well intermixing (QWI) is an attractive and promising postgrowth bandgap engineering process for the fabrication of photonic integrated circuits (PICs), as it introduces no additional electrical active dopants into the material system after intermixing. Here, we report the development of neutral impurity induced QWI processes in InGaAs-InGaAsP laser structure using low energy, i.e. 360keV, arsenic and phosphorous ion implantation. The samples were implanted at room temperature and 200 degrees C, with a dose range between 1012 and 1014 ions/cm2. The QWI stage was carried out by annealing the implanted samples at 650 degrees C for 120 s. Samples implanted at 200 degrees C give higher degree of QWI. Compared to P implanted samples, larger bandgap shift was observed form As implanted samples after annealing. A differential PL bandgap shift as large as 93 nm was observed from samples implanted with 1014 ions/cm2 of As. Bandgap tuned lasers fabricate from intermixed sample; the current threshold density of the intermixed lasers slowly increases with the amount of blueshift and is kept below 20 percent for the most blueshifted devices. The attractive device characteristics of the bandgap tuned lasers show that damage induced by the ion implantation can be almost fully tread after annealing. This implies that the material remains in good quality after QWI.

  1. RNA-seq reveals the downregulated proteins related to photosynthesis in growth-inhibited rice seedlings induced by low-energy N+ beam implantation.

    PubMed

    Chen, Q F; Ya, H Y; Wang, W D; Jiao, Z

    2014-03-26

    Transcriptomic research based on RNA sequencing (RNA-seq) technology is innovative and will provide new opportunities and biological perspectives for the use of ion-beam implantation in plants. Using RNA-seq, transcriptomes of whole rice seedlings generated from seeds implanted with a low-energy N+ beam were analyzed 96 h after planting. We identified 544 transcripts that were differentially expressed genes (DEGs) in the non-growth-inhibited sample implanted by an N+ beam, including 262 upregulated transcripts and 282 downregulated transcripts. Next, 776 transcripts were identified as DEGs in significantly damaged and growth-inhibited rice seedlings induced by N+ beam implantation, including 283 upregulated transcripts and 493 downregulated transcripts. The Gene Ontology (GO) analysis showed that 19 downregulated DEGs in the injured rice seedlings are enriched for the biological process GO term photosynthesis. The Kyoto Encyclopedia of Genes and Genomes pathway analysis also showed that 11 downregulated DEGs related to chlorophyll a/b-binding proteins are statistically significantly enriched in the photosynthesis-antenna protein pathway (Pathwayid: map00196). This result suggested that the downregulated and injured photosynthesis system contributed to the growth inhibition of rice seedlings induced by low-energy N+ beam implantation.

  2. Impact of the end of range damage from low energy Ge preamorphizing implants on the thermal stability of shallow boron profiles

    SciTech Connect

    Camillo-Castillo, R.A.; Law, M.E.; Jones, K.S.

    2004-11-01

    A fundamental understanding of the effect of scaling amorphous layers on the thermal stability of active concentrations is required for the formation of ultrashallow junctions. A study on the influence of boron on the evolution of the end of range defects for samples containing shallow amorphous layers formed by low energy germanium implants is conducted. Czochralski grown (100) silicon wafers are preamorphized with 1x10{sup 15} cm{sup -2}, 10 keV Ge{sup +} and subsequently implanted with 1x10{sup 15} cm{sup -2}, 1 keV B{sup +} such that high boron levels are attained in the end of range region. A sequence of anneals are performed at 750 deg. C, under nitrogen ambient for times ranging from 1 s to 6 h and the end of range defect evolution is imaged via plan-view transmission electron microscopy (TEM). Defect analyses are conducted utilizing quantitative TEM which indicates substantial differences in the defect evolution for samples with boron in the end of range. The extended defects observed are very unstable and undergo a fast dissolution. In contrast, stable defects are observed in the experimental control in which the evolution follows an Ostwald ripening behavior. Secondary ion mass spectroscopy analyses confirm the ephemeral nature of the defects observed and also demonstrates drastic reductions in interstitial supersaturation. In addition, uphill-type diffusion is observed to occur for a short time frame, which emphasizes a transient interstitial supersaturation. Correlation of this data with sheet resistance and active dose measurements conducted on a Hall measurement system strongly indicates the formation of boron interstitial clusters. The high boron concentrations and supersaturation levels attained at the anneal temperature enables the cluster formation. An estimate of the boron concentrations trapped in the clusters is determined from the active dose obtained from the Hall measurements and indicates concentrations much higher than those available in

  3. Annealing Behavior of Ion-implanted Nitrogen in D9 Steel

    NASA Astrophysics Data System (ADS)

    Arunkumar, J.; David, C.; Nair, K. G. M.; Magudapathy, P.; Panigrahi, B. K.; Kennedy, John

    2011-07-01

    Nitrogen isotope N15 was implanted at the sub-surface of D9 steel. The resonance nuclear reaction analysis was used to probe the implanted nitrogen as a function of depth. The as-implanted D9 sample was isochronally annealed and by observing the broadening of nitrogen depth profile at various annealing junctures, activation energy for nitrogen diffusion in steel was deduced.

  4. Effect of low-energy laser (He-Ne) irradiation on embryo implantation rate in the rat

    NASA Astrophysics Data System (ADS)

    Stein, Anat; Kraicer, P. F.; Oron, Uri

    1997-12-01

    Attempts to date to increase the rate of embryo implantation, for example by assisting embryo hatching from the zona pellucida, have failed. Recently, several studies have suggested the biostimulating effect of low power laser irradiation. The objective of this study was therefore to examine the potential of low power laser irradiation of the uterus to enhance embryo implantation rate in the rat. Rat potential of low power laser irradiation of the uterus to enhance embryo implantation rate in the rat. Rat blastocysts were flushed from the uterus on day 5 of gestation. They were transferred to the uteri of pseudopregnant recipients on day 4 or 5 of pseudopregnancy. One cornu of the recipient uterus was irradiated; the other was used as control. On day 5 of pregnancy, irradiation did not change implantation rate after 10 or 30 sec of irradiation while 120 sec. of irradiation significantly decreased embryonic implantation. On the other hand, on day 4 of pregnancy, 120 sec. of radiation allowed embryonic implantation to a level similar to that seen after synchronized transfer. Conclusion: He-Ne laser irradiation of the exposed rat uterus can attenuate embryo implantation rate.

  5. Low Energy Boron Implantation in Silicon: (1) Reduction of Channeling Tail by Careful Alignments. (2) Transient Diffusion during Rapid Thermal Annealing

    NASA Astrophysics Data System (ADS)

    Cho, Keelho

    The channeling tail in dopant distribution formed during low energy ion implantation into crystal targets is one of the major problems in shallow junction technology. The problem is more significant for implantation of light ions such as boron since it is difficult for light ions to render the crystalline target amorphous during room temperature implantation. In this thesis an attempt is made to minimize the channeling tail by implantation along a random equivalent direction following a careful alignment of the target. In order to analytically determine the random equivalent directions, critical angles for channeling are mapped on a stereogram. Boron ions with energies of 17 and 45 keV are implanted along specified directions determined from the map. The depth distribution of the dopant is profiled by SIMS and the effects of wafer orientation upon the channeling tail are noted. Industrial common use of a 7(DEGREES) tilt is not optimum. However, implantation with the wafer tilted at 5.5 (+OR-) 0.5(DEGREES) from the surface normal and rotated at 7.0 (+OR-) 0.5(DEGREES) from a (100) plane shows the least channel-tail compared to implantation along other directions. Rapid thermal annealing (RTA) is a promising annealing method for shallow junction formation. Transient enhanced diffusion of implanted boron is observed. Two different mechanisms for the boron diffusion enhancement have been suggested; namely the fast diffusion of boron interstitials or the enhancement by point defects generated during RTA. However, no experimental evidence exists so far. In this work experiments are performed with various annealing sequences of ('11)B implanted silicon combined with post-implantation of ('10)B or Si and SIMS profiling of the boron distribution. The data show that enhanced diffusion of boron during RTA is not caused by fast diffusion of boron interstitials. Rather, the enhancement is associated with an enhancement due to point defects generated during RTA. Two

  6. Fabrication and characterization of a co-planar detector in diamond for low energy single ion implantation

    DOE PAGES

    Abraham, John Bishoy Sam; Pacheco, Jose L.; Aguirre, Brandon Adrian; ...

    2016-08-09

    We demonstrate low energy single ion detection using a co-planar detector fabricated on a diamond substrate and characterized by ion beam induced charge collection. Histograms are taken with low fluence ion pulses illustrating quantized ion detection down to a single ion with a signal-to-noise ratio of approximately 10. We anticipate that this detection technique can serve as a basis to optimize the yield of single color centers in diamond. In conclusion, the ability to count ions into a diamond substrate is expected to reduce the uncertainty in the yield of color center formation by removing Poisson statistics from the implantationmore » process.« less

  7. Implantation of nitrogen, carbon, and phosphorus ions into metals

    SciTech Connect

    Guseva, M.I.; Gordeeva, G.V.

    1987-01-01

    The application of ion implantation for alloying offers a unique opportunity to modify the chemical composition, phase constitution, and microstructure of the surface layers of metals. The authors studied ion implantation of nitrogen and carbon into the surface layers of metallic targets. The phase composition of the implanted layers obtained on the Kh18N10T stainless steel, the refractory molybdenum alloy TsM-6, niobium, and nickel was determined according to the conventional method of recording the x-ray diffraction pattern of the specimens using monochromatic FeK/sub alpha/-radiation on a DRON-2,0 diffractometer. The targets were bombarded at room temperature in an ILU-3 ion accelerator. The implantation of metalloid ions was also conducted with the targets being bombarded with 100-keV phosphorus ions and 40-keV carbon ions.

  8. Few-Layer MoS₂ p-Type Devices Enabled by Selective Doping Using Low Energy Phosphorus Implantation.

    PubMed

    Nipane, Ankur; Karmakar, Debjani; Kaushik, Naveen; Karande, Shruti; Lodha, Saurabh

    2016-02-23

    P-type doping of MoS2 has proved to be a significant bottleneck in the realization of fundamental devices such as p-n junction diodes and p-type transistors due to its intrinsic n-type behavior. We report a CMOS compatible, controllable and area selective phosphorus plasma immersion ion implantation (PIII) process for p-type doping of MoS2. Physical characterization using SIMS, AFM, XRD and Raman techniques was used to identify process conditions with reduced lattice defects as well as low surface damage and etching, 4X lower than previous plasma based doping reports for MoS2. A wide range of nondegenerate to degenerate p-type doping is demonstrated in MoS2 field effect transistors exhibiting dominant hole transport. Nearly ideal and air stable, lateral homogeneous p-n junction diodes with a gate-tunable rectification ratio as high as 2 × 10(4) are demonstrated using area selective doping. Comparison of XPS data from unimplanted and implanted MoS2 layers shows a shift of 0.67 eV toward lower binding energies for Mo and S peaks indicating p-type doping. First-principles calculations using density functional theory techniques confirm p-type doping due to charge transfer originating from substitutional as well as physisorbed phosphorus in top few layers of MoS2. Pre-existing sulfur vacancies are shown to enhance the doping level significantly.

  9. Laser Diode Integrated with a Dual-Waveguide Spot-Size Converter by Low-Energy Ion Implantation Quantum Well Intermixing

    NASA Astrophysics Data System (ADS)

    Hou, Lian-Ping; Zhu, Hong-Liang; Zhou, Fan; Wang, Lu-Feng; Bian, Jing; Wang, Wei

    2005-07-01

    A ridge laser diode monolithically integrated with a buried-ridge-structure dual-waveguide spot-size converter operating at 1.58 μm is successfully fabricated by means of low-energy ion implantation quantum well intermixing and asymmetric twin waveguide technology. The passive waveguide is optically combined with a laterally tapered active core to control the mode size. The devices emit in a single transverse and quasi single longitudinal mode with a side mode suppression ratio of 40.0 dB although no grating is fabricated in the LD region. The threshold current is 50 mA. The beam divergence angles in the horizontal and vertical directions are as small as 7.3 degrees ×18.0 degrees, respectively, resulting in 3.0 dB coupling loss with a cleaved single-mode optical fibre.

  10. Electrochemical behaviour of nitrogen-implanted 4145 steel

    NASA Astrophysics Data System (ADS)

    Singh, Amarjit; Knystautas, Emile J.; Elboujdaini, Mimoun; Ghali, Edward

    1988-12-01

    The corrosion behaviour of nitrogen-implanted (with and without Ti-coating) 4145 steel was investigated using the potentiodynamic technique in a 0.5M sodium acetate/acetic acid buffer (pH 5.0) solution. Nitrogen ions (N +2) were implanted at 100 keV with doses ranging from 1 × 10 16 to 3 × 10 17 ions cm -2. Parameters such as polarization resistance, anodic and cathodic Tafel slopes along with corrosion rates were evaluated. The best results were obtained with a dose of 3× 10 17 ions cm -2. Surface morphology studied by scanning electron microscopy revealed fewer pits in Ti-coated 4145 steel. Moreover, it also suggested an increase in Ep = Epass - Epit compared to uncoated steel, thus protecting the surface from active corrosion. EDXA analysis was also carried out to study the constituents and possible mechanism of pitting.

  11. Annealing Behavior of Ion-implanted Nitrogen in D9 Steel

    SciTech Connect

    Arunkumar, J.; David, C.; Nair, K. G. M.; Panigrahi, B. K.; Magudapathy, P.; Kennedy, John

    2011-07-15

    Nitrogen isotope N{sup 15} was implanted at the sub-surface of D9 steel. The resonance nuclear reaction analysis was used to probe the implanted nitrogen as a function of depth. The as-implanted D9 sample was isochronally annealed and by observing the broadening of nitrogen depth profile at various annealing junctures, activation energy for nitrogen diffusion in steel was deduced.

  12. Nano-welding and junction formation in hydrogen titanate nanowires by low-energy nitrogen ion irradiation

    NASA Astrophysics Data System (ADS)

    Dhal, Satyanarayan; Chatterjee, Shyamal; Sarkar, Subhrangsu; Tribedi, Lokesh C.; Bapat, Rudheer; Ayyub, Pushan

    2015-06-01

    Crystalline hydrogen titanate (H2Ti3O7) nanowires were irradiated with N+ ions of different energies and fluences. Scanning electron microscopy reveals that at relatively lower fluence the nanowires are bent and start to adhere strongly to one another as well as to the silicon substrate. At higher fluence, the nanowires show large-scale welding and form a network of mainly ‘X’ and ‘Y’ junctions. Transmission electron microscopy and Raman scattering studies confirm a high degree of amorphization of the nanowire surface after irradiation. We suggest that while ion-irradiation induced defect formation and dangling bonds may lead to chemical bonding between nanowires, the large scale nano-welding and junction network formation can be ascribed to localized surface melting due to heat spike. Our results demonstrate that low energy ion irradiation with suitable choice of fluence may provide an attractive route to the formation and manipulation of large-area nanowire-based devices.

  13. Optimization of L-lactic Acid Production of Rhizopus Oryzae Mutant RLC41-6 by Ion Beam Implantation at Low-Energy

    NASA Astrophysics Data System (ADS)

    Zhou, Xiuhong; Ge, Chunmei; Yao, Jianming; Pan, Renrui; Yu, Zengliang

    2005-10-01

    In order to obtain an industrial strain with a higher L(+)-lactic acid yield, the strain Rhizopus oryzae RF3608 was mutated by means of nitrogen ion beam implantation and the mutant strain RLC41-6 was isolated. Under optimal conditions the yield of L(+)-lactic acid produced in a shake-flask reached 133 g/L-137 g/L after 36 h cultivation, indicating that the conversion rate based on glucose was as high as 88%-91% and the productivity was 3.75 g/L.h. It was almost a 115% increase in lactic acid production compared with the original strain RF3608.

  14. Estimation of nitrogen ion energy calculated using distribution for nitrogen in Si implanted by PBII

    NASA Astrophysics Data System (ADS)

    Tanaka, T.; Watanabe, S.; Takagi, T.

    2006-01-01

    Plasma-based ion implantation (PBII) using N2 gas is examined as a sterilization technique for three-dimensional targets. The application of a pulsed negative voltage (5 μs pulse width, 300 pulses/s, -800 V to -13 kV) at an N2 gas pressure of 2.4 Pa is shown to reduce the number of Bacillus pumilus survivors by up to 105 times after just 5 min of exposure. The energy of nitrogen ions is calculated based on the depth profile of nitrogen concentration in Si implanted by PBII, and it is revealed that the actual nitrogen ion energy is much lower than that calculated based on the voltage applied during processing.

  15. FeN foils by nitrogen ion-implantation

    SciTech Connect

    Jiang, Yanfeng; Wang, Jian-Ping; Al Mehedi, Md; Fu, Engang; Wang, Yongqiang

    2014-05-07

    Iron nitride samples in foil shape (free standing, 500 nm in thickness) were prepared by a nitrogen ion-implantation method. To facilitate phase transformation, the samples were bonded on the substrate followed by a post-annealing step. By using two different substrates, single crystal Si and GaAs, structural and magnetic properties of iron nitride foil samples prepared with different nitrogen ion fluences were characterized. α″-Fe{sub 16}N{sub 2} phase in iron nitride foil samples was obtained and confirmed by the proposed approach. A hard magnetic property with coercivity up to 780 Oe was achieved for the FeN foil samples bonded on Si substrate. The feasibility of using nitrogen ion implantation techniques to prepare FeN foil samples up to 500 nm thickness with a stable martensitic phase under high ion fluences has been demonstrated. A possible mechanism was proposed to explain this result. This proposed method could potentially be an alternative route to prepare rare-earth-free FeN bulk magnets by stacking and pressing multiple free-standing thick α″-Fe{sub 16}N{sub 2} foils together.

  16. SEMICONDUCTOR TECHNOLOGY: Influence of nitrogen dose on the charge density of nitrogen-implanted buried oxide in SOI wafers

    NASA Astrophysics Data System (ADS)

    Zhongshan, Zheng; Zhongli, Liu; Ning, Li; Guohua, Li; Enxia, Zhang

    2010-02-01

    To harden silicon-on-insulator (SOI) wafers fabricated using separation by implanted oxygen (SIMOX) to total-dose irradiation, the technique of nitrogen implantation into the buried oxide (BOX) layer of SIMOX wafers can be used. However, in this work, it has been found that all the nitrogen-implanted BOX layers reveal greater initial positive charge densities, which increased with increasing nitrogen implantation dose. Also, the results indicate that excessively large nitrogen implantation dose reduced the radiation tolerance of BOX for its high initial positive charge density. The bigger initial positive charge densities can be ascribed to the accumulation of implanted nitrogen near the Si-BOX interface after annealing. On the other hand, in our work, it has also been observed that, unlike nitrogen-implanted BOX, all the fluorine-implanted BOX layers show a negative charge density. To obtain the initial charge densities of the BOX layers, the tested samples were fabricated with a metal-BOX-silicon (MBS) structure based on SIMOX wafers for high-frequency capacitance-voltage (C-V) analysis.

  17. Structural, mechanical and optical properties of nitrogen-implanted titanium at different pulse frequency

    NASA Astrophysics Data System (ADS)

    Raaif, Mohamed; Mohamed, Sodky H.; Abd El-Rahman, Ahmed M.; Kolitsch, Andreas

    2013-04-01

    Plasma-immersion ion implantation (PIII) is a potent method to obtain hard and wear-resistant surface on Ti by nitrogen implantation. This presentation is one part of a sequence of experiments to optimize the microstructure and physical properties of TiN through adapting the plasma-processing parameters. In this work, nitrogen ions were implanted into samples of pure Ti at different nitrogen pulse frequency without using any external source of heating. The nitrogen-implanted surfaces were characterized by X-ray diffraction (XRD), Auger electron spectroscopy (AES), optical microscope, nano-indentation technique, ball-on-disk type tribometer, surface profilemeter, Tafel polarization technique for corrosion performance and ellipsometry. The outcomes show that, nitrogen PIII is an effectual method for nitriding titanium and nitrogen pulse frequency affected the microstructure and physical properties of the treated Ti. X-ray diffraction depicted the formation of α-Ti (N) and the cubic TiN after implanting titanium by nitrogen and the thickness of the nitrided layer increased as the nitrogen pulse frequency increased. The wear and corrosion resistance of the nitrogen-implanted titanium are improved and the friction coefficient decreased from nearly 0.8 for the un-implanted titanium to 0.3 for the implanted titanium, this ascribed to the formation of the titanium nitrided phases. Ellipsometric measurements were carried out on the PIII titanium samples at different nitrogen pulse frequency. The ellipsometric measurements show that, the thickness of the nitrided layer and surface roughness increased while the refractive index decreased with increasing nitrogen pulse frequency.

  18. An Auger Sputter Profiling Study of Nitrogen and Oxygen Ion Implantations in Two Titanium Alloys

    SciTech Connect

    Barton, B. D., Pope, L. E., Wittberg, T. N.

    1989-07-31

    Samples of two titanium alloys, Ti-6A1-4V and Ti-15V-3Cr-3Sn-3A1, were ion implanted with a combination of nitrogen (N+) and oxygen (O+). For each alloy, implantation parameters were chosen to give implanted nitrogen concentrations of approximately 10 or 50 atomic percent, from a depth of 100 nanometers to a depth of 400 nanometers. In all but one case, dual energy (200 keV and 90 keV) implantations of nitrogen were used to give a relatively uniform nitrogen concentration to a depth of 300 nanometers. In each case, oxygen was implanted at 35 keV, following the nitrogen implantation, to give an oxygen-enriched region near the surface. The implanted samples were then examined by Auger electron spectroscopy (AES) combined with argon ion sputtering. In order to determine the stoichiometry of the nitrogen implanted regions, it was necessary to determine the N (KVV) contribution to the overlapping N (KVV) and Ti (LMM) Auger transitions. It was also necessary to correct for the ion-bombardment-induced compositional changes which have been described in an earlier study of titanium nitride thin films. The corrected AES depth profiles were in good agreement with theoretical predictions.

  19. Microstructural and mechanical characterization of nitrogen ion implanted layer on 316L stainless steel

    NASA Astrophysics Data System (ADS)

    Öztürk, O.

    2009-05-01

    Nitrogen ion implantation can be used to improve surface mechanical properties (hardness, wear, friction) of stainless steels by modifying the near-surface layers of these materials. In this study, a medical grade FeCrNi alloy (316L stainless steel plate) was implanted with 85 keV nitrogen ions to a high fluence of 1 × 1018N2+ /cm2 at a substrate temperature <200 °C in an industrial implantation facility. The N implanted layer microstructures, thicknesses and strengths were studied by a combination of X-ray diffraction (XRD), conversion electron Mössbauer spectroscopy (CEMS), atomic force microscopy (AFM) and nanohardness measurements. AFM was also used for the surface roughness analysis of the implanted as well as polished materials. The CEMS analysis indicate that the N implanted layer is ∼200 nm thick and is composed of ε-(Fe,Cr,Ni)2+xN-like nitride phase with mainly paramagnetic characteristics. The nanohardness measurements clearly indicate an enhanced hardness behaviour for the N implanted layer. It is found that the implanted layer hardness is increased by a factor of 1.5 in comparison to that of the substrate material. The increased hardness resulting from nitrogen implantation is attributed to the formation of ε nitride phase.

  20. Carbon, nitrogen, and oxygen ion implantation of stainless steel

    SciTech Connect

    Rej, D.J.; Gavrilov, N.V.; Emlin, D.

    1995-12-31

    Ion implantation experiments of C, N, and O into stainless steel have been performed, with beam-line and plasma source ion implantation methods. Acceleration voltages were varied between 27 and 50 kV, with pulsed ion current densities between 1 and 10 mA/cm{sup 2}. Implanted doses ranged from 0.5 to 3 {times} 10{sup 18}cm{sup -2}, while workpiece temperatures were maintained between 25 and 800 C. Implant concentration profiles, microstructure, and surface mechanical properties of the implanted materials are reported.

  1. Production and characterization of a nitrogen-implanted Fe standard to calibrate PIGE measurements

    NASA Astrophysics Data System (ADS)

    Rodrigues, C. L.; Silva, T. F.; Added, N.; Santos, H. C.; Tabacniks, M. H.

    2014-11-01

    Three calibration standard was produced by ion implantation of nitrogen in samples of Armco iron (99.7% iron). The samples was irradiated with nitrogen ion beams at several different energies (between 4 keV and 40 keV), and the ion doses were adjusted to obtain an uniform depth profile, using simulations with SRIM code. Two standards, one thick and other a foil (1.62mg/cm2), was irradiated at same time with total nominal dose of 6.6×10-16 atoms/cm2 distributed in a region of 100 nm in depth, with an average concentration of 9.0% nitrogen in iron. The third sample uses the same profile, but with a small dose, 1.1×10-16 atoms/cm2 and average concentration of 1.5% nitrogen. The characterization of the implanted samples was done using RBS and NRA techniques to quantification of nitrogen.

  2. Temperature dependent photoluminescence properties of InAs/InP quantum dashes subjected to low energy phosphorous ion implantation and subsequent annealing.

    PubMed

    Alouane, M H Hadj; Ilahi, B; Maaref, H; Salem, B; Aimez, V; Morris, D; Gendry, M

    2011-10-01

    We report on the impact of phosphorous ion-implantation-induced band gap tuning on the temperature dependent photoluminescence (PL) properties of InAs/InP quantum dashes (QDas). The high temperature range carriers' activation energy, extracted from Arrhenius plots, is found to decrease from 238 to 42 meV when the ion implantation dose increases from 10(11) cm(-2) to 5 x 10(14) cm(-2) which is consistent with the observed emission energy blueshift increase with increasing the ion implantation doses. This effect is attributed to the As/P exchange which reduces the carrier confining potential depth. For intermediate ion implantation doses the reduced carrier confining potential barrier combined with the non-uniform intermixing process, that causes an increased QDas size dispersion, result in anomalous temperature-dependent PL properties. Indeed, the temperature induced PL emission energy redshift measured between 10 K and 300 K is found to be strongly affected by the carrier redistribution within the broadened localized QDas states.

  3. Formation of complex Al-N-C layer in aluminium by successive carbon and nitrogen implantation

    NASA Astrophysics Data System (ADS)

    Uglov, V. V.; Cherenda, N. N.; Khodasevich, V. V.; Sokol, V. A.; Abramov, I. I.; Danilyuk, A. L.; Wenzel, A.; Gerlach, J.; Rauschenbach, B.

    1999-01-01

    The results of Auger electron spectroscopy and transmission electron microscopy of the surface layer of aluminium after successive implantation by carbon and nitrogen ions are presented in this work. The energy of implanted ions is 40 keV. The implantation dose varies in the range (3.3-6.5) × 10 17 ions/cm 2. The findings show that successive implantation leads to the formation of two main layers in aluminium. The first layer is AlNC x (0 < x < 0.5) layer with violated hcp. AlN structure, where carbon atoms form bonds with nitrogen atoms. The second layer contains disoriented Al 4C 3 precipitates and carbon atoms migrated from the first layer. The mechanism of migration is discussed.

  4. Corrosion resistance and microstructure of nitrogen plasma source ion implanted bearing steel

    SciTech Connect

    Mente, K.; Baum, C.; Wang, W.; Zhang, L.; Booske, J.; Shohet, J.L.; Jacobs, J.; Freeman, D.; Perez-Albuerne, E.A.

    1996-12-31

    Feasibility of plasma source ion implantation (PSII) treatments for metal corrosion protection of bearing steel in humid environments has been investigated, following successful results with aluminum alloy. The bearing steel coupons have been treated by nitrogen PSII with a statistically designed range of processing conditions, including stage bias implant voltage, and dose. Corrosion properties of the implanted samples were tested using aerated distilled water (72, 168, and 720 hours), 90 F, 90% RH air (24, 120, 816, and 1,464 hours), and a nitric acid soak. The results are compared favorably with 400 C stainless steel, and 52100 steel with nitrogen and argon recoil-implanted chromium. Evidence is seen for an optimal process contour (low voltage-high dose; high voltage-low dose). Results from microstructure analysis will also be presented.

  5. Long-range effect in nitrogen ion-implanted AISI 316L stainless steel

    NASA Astrophysics Data System (ADS)

    Budzynski, P.

    2015-01-01

    The effect of nitrogen ion implantation on AISI 316L stainless steel was investigated. The microstructure and composition of an N implanted layer were studied by RBS, GIXRD, SEM, and EDX measurements. Friction and wear tests were also performed. The discrepancy between the measured and calculated stopped ion maximum range does not exceed 0.03 μm. After nitrogen implantation with a fluence of 5 × 1017 ion/cm2, additional phases of expanded austenite were detected. At a 5-fold larger depth than the maximum ion range, improvement in the coefficient of friction and wear was detected. We have shown, for the first time, the long-range effect in tribological investigations. The long-range effect is caused by movement of not only defects along the depth of the sample, as assumed so far, but also nitrogen atoms.

  6. Differential Expression of Retrotransposon WIS 2-1A Response to Vacuum, Low-Energy N+ Implantation and 60Coγ-ray Irradiation in Wheat

    NASA Astrophysics Data System (ADS)

    Zhao, Huiru; Gu, Yunhong; Ya, Huiyuan; Jiao, Zhen; Qin, Guangyong

    2009-02-01

    Mutagenesis and retrotransposons have a close relationship, but little attention has been paid yet to the activity of retrotransposons produced by physical mutagens. The variation of retrotransposon WIS 2-1A activity in wheat (Triticum aestivum L.) embryos at three different growth times (30 h, 45 h and 60 h) was investigated after they had been treated with N+ implantation in a vacuum of 5 × 10-2 Pa and irradiation by 60Coγ-ray respectively. For each of the three growth times the expression of WIS 2-1A showed almost entirely a same trend of downregulation, upregulation, then downregulation, and upregulation again with the increase in dose of N+ implantation, but the expression appeared irregular with the increase in irradiation of 60Coγ-ray. In conclusion, the acutely activating effect of WIS 2-1A stimulated by vacuum and high dose N+ implantation within a shorter incubation time may provide a convenient tool to advance the research on mutagenic breeding and function genes.

  7. Influence of nitrogen implantation on thermoluminescence of synthetic quartz

    NASA Astrophysics Data System (ADS)

    Nsengiyumva, S.; Chithambo, M. L.; Pichon, L.

    2014-11-01

    Thermoluminescence (TL) of synthetic quartz exposed to beta irradiation following implantation with 60 keV N+ ions at fluences ranging between 1 × 1014 and 5 × 1015 ions/cm2 is reported. The glow curve measured at 5°C/s typically consists of a prominent peak near 110°C, studied in this work, and minor glow peaks at around 130°C and 190°C. The TL intensity of the main peak increased both with implantation and with fluence of implantation. The dependence of the intensity on heating rate and fluence suggests that the implantation introduces new defects that may possibly act as recombination centres. The increase in TL intensity with the heating rate exhibited by implanted samples has been observed in other luminescence materials. This anti-quenching phenomenon has been described as a competition effect between multiple luminescence pathways in luminescence materials. Kinetic analysis of the main glow peak using the initial rise, various heating rate and glow curve deconvolution methods shows that the activation energy of the main peak is about 0.7 eV with no systematic change due to ion fluence.

  8. Influence of nitrogen implantation on thermoluminescence of synthetic quartz

    NASA Astrophysics Data System (ADS)

    Nsengiyumva, S.; Chithambo, M. L.; Pichon, L.

    2015-01-01

    Thermoluminescence (TL) of synthetic quartz exposed to beta irradiation following implantation with 60 keV N+ ions at fluences ranging between 1 × 1014 and 5 × 1015 ions/cm2 is reported. The glow curve measured at 5°C/s typically consists of a prominent peak near 110°C, studied in this work, and minor glow peaks at around 130°C and 190°C. The TL intensity of the main peak increased both with implantation and with fluence of implantation. The dependence of the intensity on the heating rate and fluence suggests that the implantation introduces new defects that may possibly act as recombination centres. The increase in TL intensity with the heating rate exhibited by implanted samples has been observed in other luminescence materials. This anti-quenching phenomenon has been described as a competition effect between multiple luminescence pathways in luminescence materials. Kinetic analysis of the main glow peak using the initial rise, various heating rate and glow-curve deconvolution methods shows that the activation energy of the main peak is about 0.7 eV with no systematic change due to ion fluence.

  9. Friction wear and auger analysis of iron implanted with 1.5-MeV nitrogen ions

    NASA Technical Reports Server (NTRS)

    Ferrante, J.; Jones, W. R., Jr.

    1982-01-01

    The effect of implantation of 1.5-MeV nitrogen ions on the friction and wear characteristics of pure iron sliding against steel was studied in a pin-on disk apparatus. An implantation dose of 5 x 10 to the 17th power ions/sq cm was used. Small reductions in initial and steady-state wear rates were observed for nitrogen-implanted iron riders as compared with unimplanted controls. Auger electron spectroscopy revealed a subsurface Gaussian nitrogen distribution with a maximum concentration of 15 at. % at a depth of 8 x 10 to the -7th m. A similar analysis within the wear scar of an implanted rider after 20 microns of wear yielded only background nitrogen concentration, thus giving no evidence for diffusion of nitrogen beyond the implanted range.

  10. Surface hardness increasing of iron alloys by nitrogen-deuterium ion implanting

    NASA Astrophysics Data System (ADS)

    Figueroa, C. A.; Alvarez, F.

    2004-12-01

    In situ x-ray photoemission spectroscopy is used to study the deuterium and hydrogen oxygen etching effect in nitrogen-implanted iron alloys. A suitable deuterium-nitrogen mixture can increase the surface original steel hardness up to ˜40%. In similar conditions, hydrogen-nitrogen mixtures improves the hardness by ˜10%. On deuteration, the main change is the reduction of the zero-point energy of the hydrides bond. Due to this, the lower scission energy of hydrogen-metal bonds as compared with deuterium-metal bonds determines the favorable effect of deuterium on the nitriding process.

  11. Estimation of Nitrogen Ion Energy in Sterilization Technology by Plasma Based Ion Implantation

    NASA Astrophysics Data System (ADS)

    Kondou, Youhei; Nakashima, Takeru; Tanaka, Takeshi; Takagi, Toshinori; Watanabe, Satoshi; Ohkura, Kensaku; Shibahara, Kentaro; Yokoyama, Shin

    Plasma based ion implantation (PBII) with negative voltage pulses to the test specimen has been applied to the sterilization process as a technique suitable for three-dimensional work pieces. Pulsed high negative voltage (5 μs pulse width, 300 pulses/s, -800 V to -15 kV) was applied to the electrode in this process at a gas pressure of 2.4 Pa of N2. We found that the PBII process, in which N2 gas self-ignitted plasma generated by only pulsed voltages is used, reduces the number of active Bacillus pumilus cell. The number of bacteria survivors was reduced by 10-5 x with 5 min exposure. Since the ion energy is the most important processing parameter, a simple method to estimate the nitrogen ion energy from distribution of nitrogen atoms in Si implanted by PBII was developed. The implanted ion energy is discussed from the SIMS in depth profiles.

  12. Physical integrated diffusion-oxidation model for implanted nitrogen in silicon

    NASA Astrophysics Data System (ADS)

    Adam, Lahir Shaik; Law, Mark E.; Dokumaci, Omer; Hegde, Suri

    2002-02-01

    Scaling the gate oxide thickness is one of many process development challenges facing device engineers today. Nitrogen implantation has been used to control gate oxide thickness. By varying the dose of the nitrogen implant, process engineers can have multiple gate oxide thicknesses in the same process. Although it has been observed that nitrogen retards gate oxidation kinetics, the physics of how this occurs is not yet well understood. Since the retardation in oxide growth is due to the diffusion of nitrogen and its subsequent incorporation at the silicon/silicon oxide interface, the study of the diffusion behavior of nitrogen in silicon becomes important. Further, it is also necessary to study how this diffusion behavior impacts oxide growth. Models have been developed to explore these issues. The diffusion model is based on ab initio results and is compared to experimental results at two temperatures. The oxide reduction model is based on the diffusion of nitrogen to the surface. The surface nitrogen is coupled to the surface reaction rate of silicon and oxygen to moderate oxide growth.

  13. Single track nanodosimetry of low energy electrons

    NASA Astrophysics Data System (ADS)

    Bantsar, A.; Grosswendt, B.; Pszona, S.; Kula, J.

    2009-02-01

    Auger-electron-emitting radionuclides (for instance, 125I) with a predominant energy spectrum below 3 keV are an active area of research towards the clinical application of radiopharmaceuticals. Hence, the necessity for an adequate description of the effects of radiation by low-energy electrons on nanometric biological targets seems to be unquestionable. Experimental nanodosimetry for low-energy electrons has been accomplished with a device named JET COUNTER. The present paper describes, for the first time, nanodosimetric experiments in nanometer-sized cavities of nitrogen using low energy electrons ranging from 100 eV to 2 keV.

  14. Structural disorder in hard amorphous carbon films implanted with nitrogen ions

    SciTech Connect

    Freire, F.L. Jr.; Franceschini, D.F.; Achete, C.A.; Brusa, R.S.; Mariotto, G.; Karwasz, G.P.; Canteri, R.

    1996-12-31

    Hard amorphous hydrogenated carbon films deposited by self-bias glow discharge were implanted at room temperature with 70 keV-nitrogen ions at fluences between 2.0 and 9.0 {times} 10{sup 16} N/cm{sup 2}. The implanted samples were analyzed by Raman spectroscopy, SIMS and positron annihilation spectroscopy (Doppler broadening technique with the determination of the parameter S). For samples implanted with 2.0 {times} 10{sup 16} N/cm{sup 2} the S parameter follows the vacancies depth profile predicted by Monte Carlo simulation. For higher fluences the authors observed a reduction in the measured value of S. This result is discussed in terms of both hydrogen loss and structural modifications (increase of disorder at local scale and of the number of graphitic domains) induced in the carbon film by ion implantation.

  15. Study of nitrogen implanted amorphous hydrogenated carbon thin films by variable-energy positron annihilation spectroscopy

    SciTech Connect

    Freire, F.L. Jr.; Franceschini, D.F.; Brusa, R.S.; Karwasz, G.R.; Mariotto, G.; Zecca, A.; Achete, C.A.

    1997-03-01

    Hard amorphous hydrogenated carbon ({ital a}-C:H) films deposited by self-bias glow discharge were implanted at room temperature with 70 keV nitrogen ions at fluences between 2.0 and 9.0{times}10{sup 16} N/cm{sup 2}. The implanted samples were analyzed by positron Doppler broadening annihilation spectroscopy to determine the voids distribution. For samples implanted with 2.0{times}10{sup 16} N/cm{sup 2} the defect distribution is broader than the vacancies depth profile predicted by Monte Carlo simulation. For higher fluences we observed a reduction of the defect density. These results are discussed in terms of a competition between two processes: ion induced defects and structural modifications induced in the films due to ion implantation. {copyright} {ital 1997 American Institute of Physics.}

  16. Formation of ultrathin nitrided SiO{sub 2} oxides by direct nitrogen implantation into silicon

    SciTech Connect

    Soleimani, H.R.; Doyle, B.S.; Philipossian, A.

    1995-08-01

    A nitridation technique is proposed for ultrathin, SiO{sub 2} oxides in deep submicron CMOS technology, which involves direct implantation of molecular nitrogen (N{sub 2}) into the silicon substrate. N{sub 2} ions were implanted into silicon at different doses and energies, through a 150 {angstrom} thick screen oxide. In this study the effect of implanted N atoms on silicon oxidation, and SiO{sub 2} oxide nitridation process have been studied. Two groups of the N{sub 2}-implanted wafers were used: wafers from one group were annealed prior to the screen oxide removal, whereas wafers of the other group did not receive this anneal. It is shown that nitridation can be achieved both ways, allowing this technique to be easily integrated into a semiconductor IC fabrication process.

  17. Low energy supersymmetry phenomenology

    SciTech Connect

    Baer, H.; Chen, C.H.; Bartl, A.; Feng, J.; Fujii, K.; Gunion, J.; Kamon, T.; Lopez, J.L.; Kao, C.

    1995-04-01

    The authors summarize the current status and future prospects for low energy (weak scale) supersymmetry. In particular, they evaluate the capabilities of various e{sup +}e{sup {minus}}, p{bar p} and pp colliders to discover evidence for supersymmetric particles. Furthermore, assuming supersymmetry is discovered, they discuss capabilities of future facilities to disentangle the anticipated spectrum of super-particles, and, via precision measurements, to test mass and coupling parameters for comparison with various theoretical expectations. The authors then comment upon the complementarity of proposed hadron and e{sup +}e{sup {minus}} machines for a comprehensive study of low energy supersymmetry.

  18. Low energy supersymmetry phenomenology

    SciTech Connect

    Baer, H.; Chen, C.H.; Bartl, A.

    1995-03-01

    The authors summarize the current status and future prospects for low energy (weak scale) supersymmetry. In particular, they evaluate the capabilities of various e{sup +}e{sup {minus}}, p{anti p} and pp colliders to discover evidence for supersymmetric particles. Furthermore, assuming supersymmetry is discovered, they discuss capabilities of future facilities to disentangle the anticipated spectrum of superparticles, and, via precision measurements, to test mass and coupling parameters for comparison with various theoretical expectations. They comment upon the complementarity of proposed hadron and e{sup +}e{sup {minus}} machines for a comprehensive study of low energy supersymmetry.

  19. Microstructure and oxidation behavior of high strength steel AISI 410 implanted with nitrogen ion

    NASA Astrophysics Data System (ADS)

    Bandriyana, Ismoyo, Agus Hadi; Sujitno, Tjipto; Dimyati, A.

    2016-04-01

    Surface treatment by implantation with nitrogen-ion was performed on the commercial feritic high strength steel AISI 410 which is termed for high temperature applications. The aim of this research was focused on the surface modification to improve its high temperature oxidation property in the early stages. Ion implantation was carried out at acceleration energy of 100 KeV and ion current 10 mA for 30, 60 and 90 minutes. The samples were subjected to the high temperature oxidation test by means of thermogravimetry in a magnetic suspension balance (MSB) at 500 °C for 5 hours. The scanning electron microscopy (SEM), X-ray diffraction spectrometry (XRD) and Vickers Hardness measurement were used for sample characterization. The formation of ferro-nitride phase after implantation did not occur, however a thin layer considered to contain nitrogen interstitials was detected. The oxidation of both samples before and after implantation followed parabolic kinetics indicating inward growth of oxide scale characteristically due to diffusion of oxygen anions towards matrix surface. After oxidation test relativelly stable oxide scales were observed. Oxidation rates decreased proportionally with the increasing of implantation time due to the formation of oxide layer which is considered to be effectiv inhibitor for the oxygen diffusion.

  20. LOW ENERGY COUNTING CHAMBERS

    DOEpatents

    Hayes, P.M.

    1960-02-16

    A beta particle counter adapted to use an end window made of polyethylene terephthalate was designed. The extreme thinness of the film results in a correspondingly high transmission of incident low-energy beta particles by the window. As a consequence, the counting efficiency of the present counter is over 40% greater than counters using conventional mica end windows.

  1. Short-range ordering of ion-implanted nitrogen atoms in SiC-graphene

    SciTech Connect

    Willke, P.; Druga, T.; Wenderoth, M.; Amani, J. A.; Weikert, S.; Hofsäss, H.; Thakur, S.; Maiti, K.

    2014-09-15

    We perform a structural analysis of nitrogen-doped graphene on SiC(0001) prepared by ultra low-energy ion bombardment. Using scanning tunneling microscopy, we show that nitrogen atoms are incorporated almost exclusively as graphitic substitution in the graphene honeycomb lattice. With an irradiation energy of 25 eV and a fluence of approximately 5 × 10{sup 14 }cm{sup −2}, we achieve a nitrogen content of around 1%. By quantitatively comparing the position of the N-atoms in the topography measurements with simulated random distributions, we find statistically significant short-range correlations. Consequently, we are able to show that the dopants arrange preferably at lattice sites given by the 6 × 6-reconstruction of the underlying substrate. This selective incorporation is most likely triggered by adsorbate layers present during the ion bombardment. This study identifies low-energy ion irradiation as a promising method for controlled doping in epitaxial graphene.

  2. Correlation between defect and magnetism of low energy Ar+9 implanted and un-implanted Zn0.95Mn0.05O thin films suitable for electronic application

    NASA Astrophysics Data System (ADS)

    Neogi, S. K.; Midya, N.; Pramanik, P.; Banerjee, A.; Bhattacharyya, A.; Taki, G. S.; Krishna, J. B. M.; Bandyopadhyay, S.

    2016-06-01

    The structural, morphological, optical and magnetic properties of Ar+9 implanted 5 at% Mn doped ZnO films have been investigated to detect the correlation between ferromagnetism (FM) and defect. Sol-gel derived films were implanted with fluences 0 (un-implanted), 5×1014 (low), 1015 (intermediate) and 1016 (high) ions/cm2. Rutherford back scattering (RBS), X-ray diffraction (XRD), atomic force microscope (AFM) and magnetic force microscope (MFM), UV-visible, photoluminescence and X-ray absorption spectroscopy (XAS) and superconducting quantum interference device vibrating sample magnetometer (SQUID VSM) were employed for investigation. XRD indicated single phase nature of the films. Absence of impurity phase has been confirmed from several other measurements also. Ion implantation induces a large concentration of point defects into the films as identified from optical study. All films exhibit intrinsic FM at room temperature (RT). The magnetization attains the maximum for the film implanted with fluence 1016 ions/cm2 with saturation magnetization (MS) value 0.69 emu/gm at RT. Magnetic properties of the films were interpreted using bound magnetic polaron (BMP). BMP generated from the intrinsic exchange interaction of Mn2+ ions and VZn related defects actually controls the FM. The practical utility of these films in transparent spin electronic device has also been exhibited.

  3. Production and characterization of a nitrogen-implanted Fe standard to calibrate PIGE measurements

    SciTech Connect

    Rodrigues, C. L.; Silva, T. F.; Added, N.; Santos, H. C.; Tabacniks, M. H.

    2014-11-11

    Three calibration standard was produced by ion implantation of nitrogen in samples of Armco iron (99.7% iron). The samples was irradiated with nitrogen ion beams at several different energies (between 4 keV and 40 keV), and the ion doses were adjusted to obtain an uniform depth profile, using simulations with SRIM code. Two standards, one thick and other a foil (1.62mg/cm{sup 2}), was irradiated at same time with total nominal dose of 6.6×10{sup −16} atoms/cm{sup 2} distributed in a region of 100 nm in depth, with an average concentration of 9.0% nitrogen in iron. The third sample uses the same profile, but with a small dose, 1.1×10{sup −16} atoms/cm{sup 2} and average concentration of 1.5% nitrogen. The characterization of the implanted samples was done using RBS and NRA techniques to quantification of nitrogen.

  4. Nitrogen implantation effects on the chemical bonding and hardness of boron and boron nitride coatings

    SciTech Connect

    Anders, S; Felter, T; Hayes, J; Jankowski, A F; Patterson, R; Poker, D; Stamler, T

    1999-02-08

    Boron nitride (BN) coatings are deposited by the reactive sputtering of fully dense, boron (B) targets utilizing an argon-nitrogen (Ar-N{sub 2}) reactive gas mixture. Near-edge x-ray absorption fine structure analysis reveals features of chemical bonding in the B 1s photoabsorption spectrum. Hardness is measured at the film surface using nanoindentation. The BN coatings prepared at low, sputter gas pressure with substrate heating are found to have bonding characteristic of a defected hexagonal phase. The coatings are subjected to post-deposition nitrogen (N{sup +} and N{sub 2}{sup +}) implantation at different energies and current densities. The changes in film hardness attributed to the implantation can be correlated to changes observed in the B 1s NEXAFS spectra.

  5. Low energy antiproton beams

    NASA Astrophysics Data System (ADS)

    Klapisch, R.

    1992-04-01

    It was the invention of stochastic cooling by S. Van Meer that has allowed antiproton beams to become a powerful tool for the physicist. As a byproduct of the high energy proton-antiproton collider, a versatile low-energy facility, LEAR has been operating at CERN since 1984. The facility and its characteristics will be described as well as examples of its use for studying fundamental properties of the antiproton and for topics in atomic, nuclear and particle Physics.

  6. The influence of nitrogen ion implantation on microhardness of the Stellite 6 alloy

    NASA Astrophysics Data System (ADS)

    Budzyński, P.; Kamiński, M.; Pałka, K.; Droździel, A.; Wiertel, M.

    2016-09-01

    Cobalt alloys known as Stellite used to produce or surfacing machine elements subjected to combustion gases and heat. They are used a currently in the manufacture of valves and valve seats in internal combustion engines. Because of the small thermal conductivity, stellite may not be subjected heat treatment. In order to improve the mechanical properties of cobalt alloys, samples were implanted with nitrogen ions with 65 keV energy and ion dose of 1·1016, 5·1016, 1·1017 N+/cm2. The influence of ion implantation on properties of strength was determined by measuring microhardness using a Vickers hardness test. The measurement results allowed to determine the increase in the microhardness of 20% with dose 5·1016 N+/cm2 compared to the sample not implanted. Implantation of nitrogen ions can increase the strength of the valves and the valve seats having Stellite without changing the external dimensions of the final element, and without interfering with its inner structure by low-temperature of modification the surface layer.

  7. Electrical activation of nitrogen heavily implanted 3C-SiC(1 0 0)

    NASA Astrophysics Data System (ADS)

    Li, Fan; Sharma, Yogesh; Shah, Vishal; Jennings, Mike; Pérez-Tomás, Amador; Myronov, Maksym; Fisher, Craig; Leadley, David; Mawby, Phil

    2015-10-01

    A degenerated wide bandgap semiconductor is a rare system. In general, implant levels lie deeper in the band-gap and carrier freeze-out usually takes place at room temperature. Nevertheless, we have observed that heavily doped n-type degenerated 3C-SiC films are achieved by nitrogen implantation level of ∼6 × 1020 cm-3 at 20 K. According to temperature dependent Hall measurements, nitrogen activation rates decrease with the doping level from almost 100% (1.5 × 1019 cm-3, donor level 15 meV) to ∼12% for 6 × 1020 cm-3. Free donors are found to saturate in 3C-SiC at ∼7 × 1019 cm-3. The implanted film electrical performances are characterized as a function of the dopant doses and post implantation annealing (PIA) conditions by fabricating Van der Pauw structures. A deposited SiO2 layer was used as the surface capping layer during the PIA process to study its effect on the resultant film properties. From the device design point of view, the lowest sheet resistivity (∼1.4 mΩ cm) has been observed for medium doped (4 × 1019 cm-3) sample with PIA 1375 °C 2 h without a SiO2 cap.

  8. High-Sensitivity Temperature Sensing Using an Implanted Single Nitrogen-Vacancy Center Array in Diamond

    NASA Astrophysics Data System (ADS)

    Wang, Guanzhong; Wang, Junfeng; Advanced Thinfilm Laboratory, University of Science; Technology of China Team

    2015-03-01

    We present a high-sensitivity temperature detection using an implanted single Nitrogen-Vacancy center array in diamond. The high-order Thermal Carr-Purcell-Meiboom-Gill (TCPMG) method was performed on the implanted single nitrogen vacancy (NV) center in diamond in a static magnetic field. We demonstrated that under small detunings for the two driving microwave frequencies, the oscillation frequency of the induced fluorescence of the NV center equals approximately to the average of the detunings of the two driving fields. On basis of the conclusion, the zero-field splitting D for the NV center and the corresponding temperature could be determined. The experiment showed that the coherence time for the high-order TCPMG was effectively extended, particularly up to 108 μs for TCPMG-8, about 14 times of the value 7.7 μs for thermal Ramsey method. This coherence time corresponded to a thermal sensitivity of 10.1 mK/Hz1/2. We also detected the temperature distribution on the surface of a diamond chip by using the implanted NV center array with the TCPMG-3. Our approach implies the feasibility for using implanted NV centers in high-quality diamonds to detect temperatures with high-sensitivity and nanoscale resolution. This work was supported by the National Basic Research Program of China (2013CB921800, 2011CB921400) and the Natural Science Foundation of China (Grant Nos. 11374280, 50772110).

  9. Corrosion behaviors of Mo coating on stainless steel 316 substrates implanted by different nitrogen ion fluences

    NASA Astrophysics Data System (ADS)

    Mojtahedzadeh Larijani, Madjid; Bafandeh, Nastaran

    2014-03-01

    The molybdenum nitride coating was produced by nitrogen ion implantation of the molybdenum layer deposited on the stainless steel 316 (SS) substrates. At first, molybdenum layers were deposited on the substrates by ion beam sputtering method, then nitrogen ions with an energy of 30 keV and a fluence between 1×1017 and 12×1017 N+ cm-2 were implanted in Mo/SS system. Crystal structure and topography of the surface are investigated by grazing incidence X-ray diffraction (GIXRD) and atomic force microscopy (AFM) image respectively. XRD patterns showed the formation of molybdenum nitride phases in all implanted samples. Corrosion tests showed that the corrosion resistance of the samples strongly depends on the nitrogen applied fluences. A considerable improvement of corrosion performance by increasing ions fluences was observed. The lowest corrosion current density with amount of 0.1 μA/cm2 was obtained at 12×1017 ions/cm2 fluence in our case.

  10. Improvement of Vitamin K2 Production by Escherichia sp. with Nitrogen Ion Beam Implantation Induction

    NASA Astrophysics Data System (ADS)

    Liu, Yan; Wang, Li; Zheng, Zhiming; Wang, Peng; Zhao, Genhai; Liu, Hui; Gong, Guohong; Wu, Hefang; Liu, Hongxia; Tan, Mu; Li, Zhemin

    2015-02-01

    Low-energy ion implantation as a novel mutagen has been increasingly applied in the microbial mutagenesis for its higher mutation frequency and wider mutation spectra. In this work, N+ ion beam implantation was used to enhance Escherichia sp. in vitamin K2 yield. Optimization of process parameters under submerged fermentation was carried out to improve the vitamin K2 yield of mutant FM5-632. The results indicate that an excellent mutant FM5-632 with a yield of 123.2±1.6 μg/L, that is four times that of the original strain, was achieved by eight successive implantations under the conditions of 15 keV and 60×2.6×1013 ions/cm2. A further optimization increased the yield of the mutant by 39.7%, i.e. 172.1±1.2 μg/L which occurred in the mutant cultivated in the optimal fermentation culture medium composed of (per liter): 15.31 g glycerol, 10 g peptone, 2.89 g yeast extract, 5 g K2HPO4, 1 g NaCl, 0.5 g MgSO4·7H2O and 0.04 g cedar wood oil, incubated at 33 °C, pH 7.0 and 180 rpm for 120 h.

  11. Acetone, butanol, and ethanol production from cane molasses using Clostridium beijerinckii mutant obtained by combined low-energy ion beam implantation and N-methyl-N-nitro-N-nitrosoguanidine induction.

    PubMed

    Li, Han-guang; Luo, Wei; Gu, Qiu-ya; Wang, Qiang; Hu, Wen-jun; Yu, Xiao-bin

    2013-06-01

    In order to obtain mutant strains showing higher solvent tolerance and butanol production than those of wild-type strains, the butanol-producing strain Clostridium beijerinckii L175 was subjected to mutagenesis using a combined method of low-energy ion beam implantation and N-methyl-N-nitro-N-nitrosoguanidine induction. With this effort, mutant strain MUT3 was isolated. When it was used for butanol fermentation in P2 medium, the production of butanol was 15.8±0.7 g/L 46% higher than the wild-type strain. Furthermore, after optimization of butanol production from cane molasses with MUT3, the maximum butanol production of 14.9±0.5 g/L were obtained in crew-capped bottles. When ABE production by MUT3 was carried out in a bioreactor, the production of butanol and total solvent were 15.1±0.8 g/L and 22.1±0.9 g/L, respectively. The remarkable butanol production and solvent tolerance of MUT3 make it promising for butanol production from cane molasses.

  12. The change of atomic distribution and hardness by nitrogen implantation into aluminum alloya)

    NASA Astrophysics Data System (ADS)

    Chung, J. P.; Lee, J. S.; Kim, K. R.; Choi, B. H.

    2008-02-01

    Through many studies of the nitrogen implantation into aluminum alloy, researchers have concluded that AlN (aluminum nitride) formation is the key to hardening the aluminum surface. We implanted nitrogen ions into the Al6061, using an ion implanter which has a modified Bernas ion source. We changed the incident ion energies (25keV, 50keV) and fluences (1×1017-2×1018ions/cm2). To measure the depth hardness of implanted samples, we used nanoindentation test. The test results showed that the hardness of the implanted sample increased as the incident ion fluence increased until 1×1018ions/cm2. However, the hardness did not increase at the fluence of 2×1018ions/cm2. Furthermore, another result showed that the hardness was slightly decreased. To see the depth distribution of elements, we used Auger electron spectroscopy (AES) analysis with depth profiling. Through the AES analysis, we observed that the nitrogen atomic ratio did not increase; since the atomic ratio reached its maximum point (50%), the depth profile formed a flat curve in the AES. It is determined by the AlN structure (1:1 combination), that is, by the stoichiometrical rule. The nitrogen atoms diffused to the inner and outer sides rather than made a narrowly ranged accumulation. We observed that the flat curve was lowered downward a little at the fluence of 2×1018ions/cm2. Observing the atomic distribution of oxygen in AES, we could conclude that the lowered curve was due to the recoil implantation of oxygen which had been originally combined with the aluminum surface in the aluminum oxide (Al2O3) layer. Comparing the AES result and the nanoindention result, we concluded that the recoiled oxygen atoms are not effective on hardening the Al surface. In this study, we observed the tendency to stop increasing the samples' hardness over the ion fluence of 1×1018ions/cm2. We observed the saturation of the atomic ratio by the stoichiometrical rule.

  13. The change of atomic distribution and hardness by nitrogen implantation into aluminum alloy.

    PubMed

    Chung, J P; Lee, J S; Kim, K R; Choi, B H

    2008-02-01

    Through many studies of the nitrogen implantation into aluminum alloy, researchers have concluded that AlN (aluminum nitride) formation is the key to hardening the aluminum surface. We implanted nitrogen ions into the Al6061, using an ion implanter which has a modified Bernas ion source. We changed the incident ion energies (25 keV, 50 keV) and fluences (1x10(17)-2x10(18) ions/cm(2)). To measure the depth hardness of implanted samples, we used nanoindentation test. The test results showed that the hardness of the implanted sample increased as the incident ion fluence increased until 1x10(18) ions/cm(2). However, the hardness did not increase at the fluence of 2x10(18) ions/cm(2). Furthermore, another result showed that the hardness was slightly decreased. To see the depth distribution of elements, we used Auger electron spectroscopy (AES) analysis with depth profiling. Through the AES analysis, we observed that the nitrogen atomic ratio did not increase; since the atomic ratio reached its maximum point (50%), the depth profile formed a flat curve in the AES. It is determined by the AlN structure (1:1 combination), that is, by the stoichiometrical rule. The nitrogen atoms diffused to the inner and outer sides rather than made a narrowly ranged accumulation. We observed that the flat curve was lowered downward a little at the fluence of 2x10(18) ions/cm(2). Observing the atomic distribution of oxygen in AES, we could conclude that the lowered curve was due to the recoil implantation of oxygen which had been originally combined with the aluminum surface in the aluminum oxide (Al(2)O(3)) layer. Comparing the AES result and the nanoindention result, we concluded that the recoiled oxygen atoms are not effective on hardening the Al surface. In this study, we observed the tendency to stop increasing the samples' hardness over the ion fluence of 1x10(18) ions/cm(2). We observed the saturation of the atomic ratio by the stoichiometrical rule.

  14. Luminescence studies on green emitting InGaN/GaN MQWs implanted with nitrogen

    PubMed Central

    Sousa, Marco A.; Esteves, Teresa C.; Sedrine, Nabiha Ben; Rodrigues, Joana; Lourenço, Márcio B.; Redondo-Cubero, Andrés; Alves, Eduardo; O'Donnell, Kevin P.; Bockowski, Michal; Wetzel, Christian; Correia, Maria R.; Lorenz, Katharina; Monteiro, Teresa

    2015-01-01

    We studied the optical properties of metalorganic chemical vapour deposited (MOCVD) InGaN/GaN multiple quantum wells (MQW) subjected to nitrogen (N) implantation and post-growth annealing treatments. The optical characterization was carried out by means of temperature and excitation density-dependent steady state photoluminescence (PL) spectroscopy, supplemented by room temperature PL excitation (PLE) and PL lifetime (PLL) measurements. The as-grown and as-implanted samples were found to exhibit a single green emission band attributed to localized excitons in the QW, although the N implantation leads to a strong reduction of the PL intensity. The green band was found to be surprisingly stable on annealing up to 1400°C. A broad blue band dominates the low temperature PL after thermal annealing in both samples. This band is more intense for the implanted sample, suggesting that defects generated by N implantation, likely related to the diffusion/segregation of indium (In), have been optically activated by the thermal treatment. PMID:25853988

  15. Significantly Enhanced Visible Light Photoelectrochemical Activity in TiO₂ Nanowire Arrays by Nitrogen Implantation.

    PubMed

    Wang, Gongming; Xiao, Xiangheng; Li, Wenqing; Lin, Zhaoyang; Zhao, Zipeng; Chen, Chi; Wang, Chen; Li, Yongjia; Huang, Xiaoqing; Miao, Ling; Jiang, Changzhong; Huang, Yu; Duan, Xiangfeng

    2015-07-08

    Titanium oxide (TiO2) represents one of most widely studied materials for photoelectrochemical (PEC) water splitting but is severely limited by its poor efficiency in the visible light range. Here, we report a significant enhancement of visible light photoactivity in nitrogen-implanted TiO2 (N-TiO2) nanowire arrays. Our systematic studies show that a post-implantation thermal annealing treatment can selectively enrich the substitutional nitrogen dopants, which is essential for activating the nitrogen implanted TiO2 to achieve greatly enhanced visible light photoactivity. An incident photon to electron conversion efficiency (IPCE) of ∼10% is achieved at 450 nm in N-TiO2 without any other cocatalyst, far exceeding that in pristine TiO2 nanowires (∼0.2%). The integration of oxygen evolution reaction (OER) cocatalyst with N-TiO2 can further increase the IPCE at 450 nm to ∼17% and deliver an unprecedented overall photocurrent density of 1.9 mA/cm(2), by integrating the IPCE spectrum with standard AM 1.5G solar spectrum. Systematic photoelectrochemical and electrochemical studies demonstrated that the enhanced PEC performance can be attributed to the significantly improved visible light absorption and more efficient charge separation. Our studies demonstrate the implantation approach can be used to reliably dope TiO2 to achieve the best performed N-TiO2 photoelectrodes to date and may be extended to fundamentally modify other semiconductor materials for PEC water splitting.

  16. The influence of nitrogen ion implantation on the tribological properties of piston rings made of Hardox and Raex steels

    NASA Astrophysics Data System (ADS)

    Budzyński, P.; Kamiński, M.; Pyszniak, K.

    2016-09-01

    The implantation of nitrogen, carbon, and oxygen can be used for enhancing the tribological properties of critical components for internal combustion engines. Hardox and Raex steels have very similar strength parameters as for steel used for piston rings in internal combustion engines. An essential criterion when selecting material for the production of piston rings is a low friction factor and a low wear index. The aim of this study was to determine the extent to which these parameters can be enhanced by nitrogen ion implantation. Samples were implanted with nitrogen ions with 65 keV energy and the fluence of implanted ions set to 1.1017 N + /cm2. Friction and wear measurements were performed on a pin-on disc stand. The results demonstrate that implantation with nitrogen ions significantly reduces the friction factor and wear of Hardox 450 and Raex 400 steels. Implantation can and should be used for enhancing the tribological properties of steel used for friction elements in internal combustion engines, particularly when heat treatment is excluded. Final elements can be subjected to implantation, as the process does not change their dimensions.

  17. Enhanced light extraction efficiency of GaN-based light-emittng diodes by nitrogen implanted current blocking layer

    SciTech Connect

    Kim, Yong Deok; Oh, Seung Kyu; Park, Min Joo; Kwak, Joon Seop

    2016-10-15

    Highlights: • A nitrogen implanted current-blocking layer was successfully demonstrated. • Light-extraction efficiency and radiant intensity was increased by more than 20%. • Ion implantation was successfully implemented in GaN based light-emitting diodes. - Abstract: GaN-based light emitting diodes (LEDs) with a nitrogen implanted current-blocking layer (CBL) were successfully demonstrated for improving the light extraction efficiency (LEE) and radiant intensity. The LEE and radiant intensity of the LEDs with a shallow implanted CBL with nitrogen was greatly increased by more than 20% compared to that of a conventional LED without the CBL due to an increase in the effective current path, which reduces light absorption at the thick p-pad electrode. Meanwhile, deep implanted CBL with a nitrogen resulted in deterioration of the LEE and radiant intensity because of formation of crystal damage, followed by absorption of the light generated at the multi-quantum well(MQW). These results clearly suggest that ion implantation method, which is widely applied in the fabrication of Si based devices, can be successfully implemented in the fabrication of GaN based LEDs by optimization of implanted depth.

  18. Effects of nitrogen ion implantation time on tungsten films deposited by DC magnetron sputtering on AISI 410 martensitic stainless steel

    NASA Astrophysics Data System (ADS)

    Malau, Viktor; Ilman, Mochammad Noer; Iswanto, Priyo Tri; Jatisukamto, Gaguk

    2016-03-01

    Nitrogen ion implantation time on tungsten thin film deposited on surface of AISI 410 steel has been performed. Tungsten thin film produced by dc magnetron sputtering method was deposited on AISI 410 martensitic stainless steel substrates, and then the nitrogen ions were implanted on tungsten thin film. The objective of this research is to investigate the effects of implantation deposition time on surface roughness, microhardness, specific wear and corrosion rate of nitrogen implanted on tungsten film. Magnetron sputtering process was performed by using plasma gas of argon (Ar) to bombardier tungsten target (W) in a vacuum chamber with a pressure of 7.6 x 10-2 torr, a voltage of 300 V, a sputter current of 80 mA for sputtered time of 10 minutes. Nitrogen implantation on tungsten film was done with an initial pressure of 3x10-6 mbar, a fluence of 2 x 1017 ions/cm2, an energy of 100 keV and implantation deposition times of 0, 20, 30 and 40 minutes. The surface roughness, microhardness, specific wear and corrosion rate of the films were evaluated by surfcorder test, Vickers microhardness test, wear test and potentiostat (galvanostat) test respectively. The results show that the nitrogen ions implanted deposition time on tungsten film can modify the surface roughness, microhardness, specific wear and corrosion rate. The minimum surface roughness, specific wear and corrosion rate can be obtained for implantation time of 20 minutes and the maximum microhardness of the film is 329 VHN (Vickers Hardness Number) for implantation time of 30 minutes. The specific wear and corrosion rate of the film depend directly on the surface roughness.

  19. Direct observation of enhanced emission sites in nitrogen implanted hybrid structured ultrananocrystalline diamond films

    SciTech Connect

    Panda, Kalpataru; Sundaravel, B.; Panigrahi, B. K.; Chen, Huang-Chin; Lin, I.-Nan

    2013-02-07

    A hybrid-structured ultrananocrystalline diamond (h-UNCD) film, synthesized on Si-substrates by a two-step microwave plasma enhanced chemical vapour deposition (MPECVD) process, contains duplex structure with large diamond aggregates evenly dispersed in a matrix of ultra-small grains ({approx}5 nm). The two-step plasma synthesized h-UNCD films exhibit superior electron field emission (EFE) properties than the one-step MPECVD deposited UNCD films. Nitrogen-ion implantation/post-annealing processes further improve the EFE properties of these films. Current imaging tunnelling spectroscopy in scanning tunnelling spectroscopy mode directly shows increased density of emission sites in N implanted/post-annealed h-UNCD films than as-prepared one. X-ray photoelectron spectroscopy measurements show increased sp{sup 2} phase content and C-N bonding fraction in N ion implanted/post-annealed films. Transmission electron microscopic analysis reveals that the N implantation/post-annealing processes induce the formation of defects in the diamond grains, which decreases the band gap and increases the density of states within the band gap of diamond. Moreover, the formation of nanographitic phase surrounding the small diamond grains enhanced the conductivity at the diamond grain boundaries. Both of the phenomena enhance the EFE properties.

  20. High-sensitivity temperature sensing using an implanted single nitrogen-vacancy center array in diamond

    NASA Astrophysics Data System (ADS)

    Wang, Junfeng; Feng, Fupan; Zhang, Jian; Chen, Jihong; Zheng, Zhongcheng; Guo, Liping; Zhang, Wenlong; Song, Xuerui; Guo, Guoping; Fan, Lele; Zou, Chongwen; Lou, Liren; Zhu, Wei; Wang, Guanzhong

    2015-04-01

    We presented a high-sensitivity temperature detection using an implanted single nitrogen-vacancy (NV) center array in diamond. The high-order thermal Carr-Purcell-Meiboom-Gill (TCPMG) method was performed on the implanted single NV center in diamond in a static magnetic field. We demonstrated that under small detunings for the two driving microwave frequencies, the oscillation frequency of the induced fluorescence of the NV center equals approximately the average of the detunings of the two driving fields. On the basis of the conclusion, the zero-field splitting D for the NV center and the corresponding temperature could be determined. The experiment showed that the coherence time for the high-order TCPMG was effectively extended, particularly up to 108 μ s for TCPMG-8, about 14 times the value 7.7 μ s for thermal Ramsey method. This coherence time corresponded to a thermal sensitivity of 10.1 mK/Hz1 /2. We also detected the temperature distribution on the surface of a diamond chip in three different circumstances by using the implanted NV center array with the TCPMG-3 method. The experiment implies the feasibility of using implanted NV centers in high-quality diamonds to detect temperatures in biology, chemistry, materials science, and microelectronic systems with high sensitivity and nanoscale resolution.

  1. Microstructural investigation of alumina implanted with 30 keV nitrogen ions

    NASA Astrophysics Data System (ADS)

    Shikha, Deep; Jha, Usha; Sinha, S. K.; Barhai, P. K.; Sarkhel, G.; Nair, K. G. M.; Dash, S.; Tyagi, A. K.; Kothari, D. C.

    2007-11-01

    Among ceramics, alumina is being widely used as biomaterials now these days. It is being used as hip joints, tooth roots etc. Ion implantation has been employed to modify its surface without changing it bulk properties. 30 keV nitrogen with varying ion dose ranging from 5 × 10 15 ions/cm 2 to 5 × 10 17 ions/cm 2 is implanted in alumina. Surface morphology has been studied with optical microscope and atomic force microscope (AFM). Improvement in brittleness has been observed with the increase in ion dose. Compound formation and changes in grain size have been studied using X-Ray diffraction (XRD). AlN compound formation is also observed by Fourier transform infrared spectroscopy (FTIR). The change in the grain size is related with the nanohardness and Hall-Petch relationship is verified.

  2. X-ray photoelectron spectroscopic depth profilometry of nitrogen implanted in materials for modification of their surface properties

    SciTech Connect

    Sarkissian, A.H.; Paynter, R.; Stansfield, B.L.; Leblanc, J.B.; Paradis, E.

    1996-12-31

    The modification of the surface properties of materials has a wide range of industrial applications. For example, the authors change the electrical characteristics of semiconductors, improve surface hardness, decrease friction, increase resistance to corrosion, improve adhesion, etc. Nitriding is one of the most common processes used in industry for surface treatment. Nitrogen ion implantation is one technique often used to achieve this goal. Ion implantation offers the power to control the deposition profile, and can be achieved by either conventional ion beam implantation or plasma assisted ion implantation. They have used the technique of plasma assisted ion implantation to implant nitrogen in several materials, including titanium, silicon and stainless steel. The plasma source is a surface ECR source developed at INRS-Energie et Materiaux. The depth profile of the implanted ions has been measured by X-ray photoelectron spectroscopy. They have also conducted simulations using the TRIM-95 code to predict the depth profile of the implanted ions. Comparisons of the measured results with those from simulations are used to deduce information regarding the plasma composition and the collisional effects in the plasma. A fast responding, current and voltage measuring circuit with fiber optic links is being developed, which allows more accurate quantitative measurements. Further experiments to study the characteristics of the plasma, and their effects on the characteristics of the implanted surfaces are in progress, and the results are presented at this meeting.

  3. Interaction between Low Energy Ions and the Complicated Organism

    NASA Astrophysics Data System (ADS)

    Yu, Zeng-liang

    1999-12-01

    Low energy ions exist widely in natural world, but people pay a little attention on the interaction between low energy ions and matter, it is even more out of the question of studying on the relation of low energy ions and the complicated organism. The discovery of bioeffect induced by ion implantation has, however, opened a new branch in the field of ion beam application in life sciences. This paper reports recent advances in research on the role of low energy ions in chemical synthesis of the biomolecules and application in genetic modification.

  4. Formation of boron nitride and boron carbide composite by nitrogen implantation at elevated temperature

    NASA Astrophysics Data System (ADS)

    Yu, N.; Romero-Borja, F.; Zhang, Z. H.; Cui, X. T.; Liu, J. R.; Wood, L. T.; Chu, W. K.; Marton, D.; Rabalais, J. W.; Forster, K. M.; Reeber, R. R.

    1993-09-01

    Boron carbide (B4C) is a wear resistant material with hardness slightly less than that of diamond. It has an excellent strength to weight ratio and relatively high toughness under controlled processing. These essential mechanical properties make B4C an ideal candidate for cutting tool and bearing applications. We will demonstrate that hexagonal boron nitride (h-BN), a good solid lubricant, can be formed on B4C surfaces through high temperature (850 °C) nitrogen ion implantation. The formation of composite B4C and h-BN on the B4C surface can potentially reduce surface friction coefficients, making the material more attractive for tribological applications.

  5. Nitrogen plasma-implanted titanium as bipolar plates in polymer electrolyte membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Feng, Kai; Kwok, Dixon T. K.; Liu, Dongan; Li, Zhuguo; Cai, Xun; Chu, Paul K.

    Nitrogen plasma immersion ion implantation (PIII), a non-line-of-sight surface treatment technique suitable for bipolar plates in polymer electrolyte membrane fuel cells, is conducted at low and high temperature to improve the corrosion resistance and conductivity of titanium sheets. X-ray photoelectron spectroscopy (XPS) shows that high-temperature (HT) nitrogen PIII produces a thick oxy-nitride layer on the titanium surface. This layer which provides good corrosion resistance and high electrical conductivity as verified by electrochemical tests, inductively coupled plasma optical emission spectroscopy, and interfacial contact resistance (ICR) measurements renders the materials suitable for polymer electrolyte membrane fuel cells. In comparison, the low-temperature (LT) PIII titanium sample exhibits poorer corrosion resistance and electrical conductivity than the untreated titanium control.

  6. Low energy ballasted flotation.

    PubMed

    Jarvis, P; Buckingham, P; Holden, B; Jefferson, B

    2009-08-01

    A novel process which involves the replacement or supplementation of bubbles in the dissolved air flotation process with low density beads is presented. The work comprised a series of bench-scale flotation trials treating three commonly encountered algal species (Microcystis, Melosira and Chlorella) that were removed in a flotation cell configured as either: conventional dissolved air flotation (DAF); ballasted flotation using low density 70 microm glass beads with a density of 100 kg m(-3); or a hybrid process of ballasted flotation combined with conventional DAF. Results indicated that the bead only system was capable of achieving better residual turbidity than standard DAF at bead concentrations of 500 mg L(-1). Addition of beads in combination with standard DAF reduced turbidity further to even lower residual turbidity levels. Algae removal was improved when glass beads were dosed, but removal was dependent on algal species. Microcystis was removed by 97% for bead only systems and this removal did not change significantly with the addition of air bubbles. Melosira was the next best removed algae with bead only dosed systems giving similar removals to that achieved by standard DAF using a 10% air recycle ratio (81 and 76% removal respectively). Chlorella was the least well removed algae by bead only systems (63% removal). However, removal was rapidly improved to 86% by the addition of air bubbles using only a 2% recycle ratio. Energy estimations suggested that at least a 50% energy reduction could be achieved using the process offering a potential route for future development of low energy separation processes for algae removal.

  7. Nitrogen Plasma Ion Implantation of Al and Ti alloys in the High Voltage Glow Discharge Mode

    NASA Astrophysics Data System (ADS)

    Oliveira, R. M.; Ueda, M.; Rossi, J. O.; Reuther, H.; Lepienski, C. M.; Beloto, A. F.

    2006-11-01

    Enhanced surface properties can be attained for aluminum and its alloys (mechanical and tribological) and Ti6Al4V (mainly tribological) by Plasma Immersion Ion Implantation (PIII) technique. The main problem here, more severe for Al case, is the rapid oxygen contamination even in low O partial pressure. High energy nitrogen ions during PIII are demanded for this situation, in order to enable the ions to pass through the formed oxide layer. We have developed a PIII system that can operate at energies in excess of 50keV, using a Stacked Blumlein (SB) pulser which can nominally provide up to 100 kV pulses. Initially, we are using this system in the High Voltage Glow Discharge (HVGD) mode, to implant nitrogen ions into Al5052 alloy with energies in the range of 30 to 50keV, with 1.5μs duration pulses at a repetition rate of 100Hz. AES, pin-on-disc, nanoindentation measurements are under way but x-ray diffraction results already indicated abundant formation of AlN in the surface for Al5052 treated with this HVGD mode. Our major aim in this PIII experiment is to achieve this difficult to produce stable and highly reliable AlN rich surface layer with high hardness, high corrosion resistance and very low wear rate.

  8. Nitrogen Plasma Ion Implantation of Al and Ti alloys in the High Voltage Glow Discharge Mode

    SciTech Connect

    Oliveira, R. M.; Ueda, M.; Rossi, J. O.; Reuther, H.; Lepienski, C. M.; Beloto, A. F.

    2006-11-13

    Enhanced surface properties can be attained for aluminum and its alloys (mechanical and tribological) and Ti6Al4V (mainly tribological) by Plasma Immersion Ion Implantation (PIII) technique. The main problem here, more severe for Al case, is the rapid oxygen contamination even in low O partial pressure. High energy nitrogen ions during PIII are demanded for this situation, in order to enable the ions to pass through the formed oxide layer. We have developed a PIII system that can operate at energies in excess of 50keV, using a Stacked Blumlein (SB) pulser which can nominally provide up to 100 kV pulses. Initially, we are using this system in the High Voltage Glow Discharge (HVGD) mode, to implant nitrogen ions into Al5052 alloy with energies in the range of 30 to 50keV, with 1.5{mu}s duration pulses at a repetition rate of 100Hz. AES, pin-on-disc, nanoindentation measurements are under way but x-ray diffraction results already indicated abundant formation of AlN in the surface for Al5052 treated with this HVGD mode. Our major aim in this PIII experiment is to achieve this difficult to produce stable and highly reliable AlN rich surface layer with high hardness, high corrosion resistance and very low wear rate.

  9. Highly tunable formation of nitrogen-vacancy centers via ion implantation

    SciTech Connect

    Sangtawesin, S.; Brundage, T. O.; Atkins, Z. J.; Petta, J. R.

    2014-08-11

    We demonstrate highly tunable formation of nitrogen-vacancy (NV) centers using 20 keV {sup 15}N{sup +} ion implantation through arrays of high-resolution apertures fabricated with electron beam lithography. By varying the aperture diameters from 80 to 240 nm, as well as the average ion fluences from 5×10{sup 10} to 2 × 10{sup 11} ions/cm{sup 2}, we can control the number of ions per aperture. We analyze the photoluminescence on multiple sites with different implantation parameters and obtain ion-to-NV conversion yields of 6%–7%, consistent across all ion fluences. The implanted NV centers have spin dephasing times T{sub 2}{sup *} ∼ 3 μs, comparable to naturally occurring NV centers in high purity diamond with natural abundance {sup 13}C. With this technique, we can deterministically control the population distribution of NV centers in each aperture, allowing for the study of single or coupled NV centers and their integration into photonic structures.

  10. Towards Low Energy Atrial Defibrillation.

    PubMed

    Walsh, Philip; Kodoth, Vivek; McEneaney, David; Rodrigues, Paola; Velasquez, Jose; Waterman, Niall; Escalona, Omar

    2015-09-03

    transcutaneous power transfer and sensing of ICI during cardioversion are evidenced as key to the advancement of low-energy atrial defibrillation.

  11. Towards Low Energy Atrial Defibrillation

    PubMed Central

    Walsh, Philip; Kodoth, Vivek; McEneaney, David; Rodrigues, Paola; Velasquez, Jose; Waterman, Niall; Escalona, Omar

    2015-01-01

    transcutaneous power transfer and sensing of ICI during cardioversion are evidenced as key to the advancement of low-energy atrial defibrillation. PMID:26404298

  12. The effect of nitrogen ion implantation on the corrosion resistance and microstructure of tantalum-coated stainless steel

    NASA Astrophysics Data System (ADS)

    Eshghi, S.; Hanteh Zadeh, M.; Yari, M.; Jafari-Khamse, E.

    2014-06-01

    In this work, the effects of nitrogen ion implantation on the corrosion resistance and microstructure of DC magnetron sputtered tantalum-coated stainless steel were investigated. The nitrogen fluence was varied between 3-10 × 1017 ions/cm2 while the beam energy was kept constant at 30 keV. The effects of ion implantation were characterized by X-ray diffraction pattern, atomic force microscopy, and potentiodynamic corrosion test in a 0.5 MH2SO4 solution. The atomic force microscopy micrographs were quantitatively and statistically analyzed by computing the multifractal spectrum of the atomic force microscopy images. The results showed that the fluence variation strongly affected the surface roughness and formation of TaN and Ta2N phases. Increasing the nitrogen fluence up to 10 × 1017 ions/cm2 increased surface roughness. The highest corrosion resistance was obtained at 7 × 1017 ions/cm2 nitrogen fluence.

  13. In vivo biocompatibility of boron doped and nitrogen included conductive-diamond for use in medical implants.

    PubMed

    Garrett, David J; Saunders, Alexia L; McGowan, Ceara; Specks, Joscha; Ganesan, Kumaravelu; Meffin, Hamish; Williams, Richard A; Nayagam, David A X

    2016-01-01

    Recently, there has been interest in investigating diamond as a material for use in biomedical implants. Diamond can be rendered electrically conducting by doping with boron or nitrogen. This has led to inclusion of boron doped and nitrogen included diamond elements as electrodes and/or feedthroughs for medical implants. As these conductive device elements are not encapsulated, there is a need to establish their clinical safety for use in implants. This article compares the biocompatibility of electrically conducting boron doped diamond (BDD) and nitrogen included diamond films and electrically insulating poly crystalline diamond films against a silicone negative control and a BDD sample treated with stannous octoate as a positive control. Samples were surgically implanted into the back muscle of a guinea pig for a period of 4-15 weeks, excised and the implant site sectioned and submitted for histological analysis. All forms of diamond exhibited a similar or lower thickness of fibrotic tissue encapsulating compared to the silicone negative control samples. All forms of diamond exhibited similar or lower levels of acute, chronic inflammatory, and foreign body responses compared to the silicone negative control indicating that the materials are well tolerated in vivo.

  14. Mass Deposition, Etching and Sputtering Effects of Low-Energy N+ Ion Irradiation on Solid Fly Ash

    NASA Astrophysics Data System (ADS)

    Miao, Chunguang; Wang, Xiangqin

    2013-12-01

    Fly ash is an industrial waste created when coal is burned to generate electrical power. In the present study, we used low-energy nitrogen ion implantation on fly ash to improve its surface properties. Scanning electron microscope (SEM), fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and inductively coupled plasma-atomic emission spectroscopy (ICP-AES) were used to study the changes of physical and chemical properties of fly ash after N+ ion implantation, and the mechanism of fly ash modified by ion implantation. In the optimal implantation with energy of 5 keV and dose of 15D0, the ion beam could effectively increase the specific surface area (approximately 150% increase) of the fly ash. Lots of scratches were generated in the surface of the fly ash after N+ ion implantation, therefore it is good for enhancing the specific surface area. Experimental results show that the ion implantation could open the chemical bonds of Si-O, Si-Al and Al-O, and deposit nitrogen ions on the surface of fly ash.

  15. Improvement in wear performance of surgical Ti-6Al-4V alloy by ion implantation of nitrogen or carbon

    SciTech Connect

    Williams, J.M.; Buchanan, R.A.; Rigney, E.D. Jr.

    1985-06-01

    The effects of ion implantations of either nitrogen or carbon on the corrosive-wear performance of surgical Ti-6A1-4V alloy were investigated. In vitro tests made use of an apparatus which could produce certain chemical and mechanical aspects of a sliding interface such as that which occurs between alloy and polyethylene components of an artificial hip (or knee) joint. Cylindrical samples of the Ti alloy were rotated between loaded, conforming pads made of ultrahigh molecular weight polyethylene (UHMWPE) while these test components were immersed either in a saline solution or a saline solution with bovine serum added. During the tests open-circuit corrosion currents for the alloy were measured by the Tafel extrapolation technique. Profilometry studies were done before and after the tests. Alloy samples implanted with either nitrogen or carbon remained as-new for all test conditions. Unimplanted control samples were severely scored. Corrosion currents as measured under the mechanical action were reduced by a factor of approximately one hundred by the ion implantation treatments. It is concluded that nitrogen or carbon ion implantation produces a marked improvement in the corrosive wear performance of the alloy in these tests. It is inferred that abrasive wear is the dominant mechanism of material removal. In addition, apparently owing to reduction of wear debris in the sliding interface, ion treatment of the alloy greatly improves wear performance of the mating UHMWPE component. 11 refs., 11 figs., 2 tabs.

  16. Enhancement of nitrogen and phosphorus removal from eutrophic water by economic plant annual ryegrass (Lolium multiflorum) with ion implantation.

    PubMed

    Li, Miao; Sheng, Guo-ping; Wu, Yue-jin; Yu, Zeng-liang; Bañuelos, Gary S; Yu, Han-qing

    2014-01-01

    Severe eutrophication of surface water has been a major problem of increasing environmental concern worldwide. In the present study, economic plant annual ryegrass (Lolium multiflorum) was grown in floating mats as an economic plant-based treatment system to evaluate its potential after ion implantation for removing nutrients in simulated eutrophic water. The specific weight growth rate of L. multiflorum with ion implantation was significantly greater than that of the control, and the peroxidase, nitrate reductase, and acid phosphatase activities of the irradiated L. multiflorum were found to be greater than those plants without ion implantation. Higher total nitrogen (TN) and total phosphorus (TP) removal efficiencies were obtained for the L. multiflorum irradiated with 25 keV 5.2 × 10(16) N(+) ions/cm(2) and 30 keV 4.16 × 10(16) N(+) ions/cm(2), respectively (p < 0.05). Furthermore, the nitrogen and phosphorus contents in the plant biomass with ion implantation were also greater than those in the control and were positively correlated with TN and TP supplied. L. multiflorum itself was directly responsible for 39-49 and 47-58 % of the overall N and P removal in the experiment, respectively. The research results suggested that ion implantation could become a promising approach for increasing phytoremediation efficiency of nutrients from eutrophic water by L. multiflorum.

  17. Effects Of Ion Energy On Nitrogen Plasma Immersion Ion Implantation In UHMWPE Polymer Through A Metal Grid

    SciTech Connect

    Ueda, M.; Oliveira, R. M.; Rossi, J. O.; Lepienski, C. M.; Vilela, W. A.

    2006-11-13

    Herein, we consider the potential application of plasma immersion ion implantation (PIII) for treatment of polymer surfaces. This paper presents some experimental data for ultra-high molecular weight polyethylene (UHMWPE) implanted with nitrogen using PIII process. This polymer is widely used in medical prosthesis and PIII treatment has revealed to be an ease and cheap way to improve the lifetime of prosthesis made with UHMWPE. Here we show the latest results for UHMWPE surface treatment obtained with the use of a high voltage pulser of 100kV/200A based on coaxial Blumlein technology.

  18. Effects Of Ion Energy On Nitrogen Plasma Immersion Ion Implantation In UHMWPE Polymer Through A Metal Grid

    NASA Astrophysics Data System (ADS)

    Ueda, M.; Oliveira, R. M.; Rossi, J. O.; Lepienski, C. M.; Vilela, W. A.

    2006-11-01

    Herein, we consider the potential application of plasma immersion ion implantation (PIII) for treatment of polymer surfaces. This paper presents some experimental data for ultra-high molecular weight polyethylene (UHMWPE) implanted with nitrogen using PIII process. This polymer is widely used in medical prosthesis and PIII treatment has revealed to be an ease and cheap way to improve the lifetime of prosthesis made with UHMWPE. Here we show the latest results for UHMWPE surface treatment obtained with the use of a high voltage pulser of 100kV/200A based on coaxial Blumlein technology.

  19. Corrosion Behaviour of Nitrogen-Implantation Ti-Ta-Nb Alloy in Physiological Solutions Simulating Real Conditions from Human Body

    NASA Astrophysics Data System (ADS)

    Drob, Silviu Iulian; Vasilescu, Cora; Drob, Paula; Vasilescu, Ecaterina; Gordin, Doina Margareta; Gloriant, Thierry

    2015-04-01

    We applied a new nitrogen-implantation technique (trademark Hardion+) using a source of nitrogen ions, electron cyclotron resonance that assures higher energy and deeper implantation than the conventional techniques. The N-implantation surface of the new Ti-25Ta-25Nb alloy was analyzed as follows: for the phase identification by x-ray diffraction (XRD) in a glancing geometry (1°); for the hardness by the nano-indentation method; for the corrosion behaviour in Ringer solutions of different pH values (simulating the real conditions from the human body) by cyclic and linear polarization, electrochemical impedance spectroscopy and the monitoring of the open circuit potentials and corresponding potential gradients. XRD pattern was indexed with face-centred cubic TiN compound partially substituted with TaN and NbN. The hardness increased about 2 times for the N-implantation alloy. The implantation layer had a protection effect, increasing the corrosion and passivation potentials and decreasing the tendency to passivation and passive current density, due to its compactness, reinforcement action. The corrosion current density and rate decreased by about 10 times and the polarization resistance increased by about 2 times, indicative of a more resistant nitride layer. The porosity was much reduced and the protection efficiency had values closed to 90%, namely the implantation treatment led to the formation of a dense, resistant layer. Impedance spectra showed that the capacitive behaviour of the N-implantation alloy was more insulating and protective. An electric equivalent circuit with two times constants was modelled.

  20. Mechanical properties of nitrogen-rich surface layers on SS304 treated by plasma immersion ion implantation

    NASA Astrophysics Data System (ADS)

    Fernandes, B. B.; Mändl, S.; Oliveira, R. M.; Ueda, M.

    2014-08-01

    The formation of hard and wear resistant surface regions for austenitic stainless steel through different nitriding and nitrogen implantation processes at intermediate temperatures is an established technology. As the inserted nitrogen remains in solid solution, an expanded austenite phase is formed, accounting for these surface improvements. However, experiments on long-term behavior and exact wear processes within the expanded austenite layer are still missing. Here, the modified layers were produced using plasma immersion ion implantation with nitrogen gas and had a thickness of up to 4 μm, depending on the processing temperature. Thicker layers or those with higher surface nitrogen contents presented better wear resistance, according to detailed microscopic investigation on abrasion, plastic deformation, cracking and redeposition of material inside the wear tracks. At the same time, cyclic fatigue testing employing a nanoindenter equipped with a diamond ball was carried out at different absolute loads and relative unloadings. As the stress distribution between the modified layer and the substrate changes with increasing load, additional simulations were performed for obtaining these complex stress distributions. While high nitrogen concentration and/or thicker layers improve the wear resistance and hardness, these modifications simultaneously reduce the surface fatigue resistance.

  1. A low energy electron magnetometer

    NASA Technical Reports Server (NTRS)

    Singh, J. J.; Wood, G. M., Jr.; Rayborn, G. H.; White, F. A.

    1979-01-01

    The concept of a highly sensitive magnetometer based on the deflection of low energy electron beams in magnetic fields is analyzed. Because of its extremely low mass and consequently high e/m ratio, a low energy electron is easily deflected in a magnetic field, thus providing a basis for very low field measurement. Calculations for a specific instrument design indicate that a low energy electron magnetometer (LEEM) can measure magnetic fields as low as 1000 nT. The anticipated performance of LEEM is compared with that of the existing high resolution magnetometers in selected applications. The fast response time of LEEM makes it especially attractive as a potential instrument for magnetic signature analysis in large engineering systems.

  2. Study of the effects of E × B fields as mechanism to carbon-nitrogen plasma immersion ion implantation on stainless steel samples

    NASA Astrophysics Data System (ADS)

    Pillaca, E. J. D. M.; Ueda, M.; Oliveira, R. M.; Pichon, L.

    2014-08-01

    Effects of E × B fields as mechanism to carbon-nitrogen plasma immersion ion implantation (PIII) have been investigated. This magnetic configuration when used in PIII allows obtaining high nitrogen plasma density close to the ion implantation region. Consequently, high ions dose on the target is possible to be achieved compared with standard PIII. In this scenario, nitrogen and carbon ions were implanted simultaneously on stainless steel, as measured by GDOES and detected by X-ray diffraction. Carbon-tape disposed on the sample-holder was sputtered by intense bombardment of nitrogen ions, being the source of carbon atoms in this experiment. The implantation of both N and C caused changes on sample morphology and improvement of the tribological properties of the stainless steel.

  3. Low Energy Schools in Ireland

    ERIC Educational Resources Information Center

    Heffernan, Martin

    2004-01-01

    Out of a commitment to reducing carbon dioxide emissions, Ireland's Department of Education and Science has designed and constructed two low energy schools, in Tullamore, County Offaly, and Raheen, County Laois. With energy use in buildings responsible for approximately 55% of the CO[subscript 2] released into the atmosphere and a major…

  4. Nanoarchitectured Co-Cr-Mo orthopedic implant alloys: nitrogen-enhanced nanostructural evolution and its effect on phase stability.

    PubMed

    Yamanaka, Kenta; Mori, Manami; Chiba, Akihiko

    2013-04-01

    Our previous studies indicate that nitrogen addition suppresses the athermal γ (face-centered cubic, fcc)→ε (hexagonal close-packed, hcp) martensitic transformation of biomedical Co-Cr-Mo alloys and ultimately offers large elongation to failure while maintaining high strength. In the present study, structural evolution and dislocation slip as an elementary process in the martensitic transformation in Co-Cr-Mo alloys were investigated to reveal the origin of their enhanced γ phase stability due to nitrogen addition. Alloy specimens with and without nitrogen addition were prepared. The N-doped alloys had a single-phase γ matrix, whereas the N-free alloys had a γ/ε duplex microstructure. Irrespective of the nitrogen content, dislocations frequently dissociated into Shockley partial dislocations with stacking faults. This indicates that nitrogen has little effect on the stability of the γ phase, which is also predicted by thermodynamic calculations. We discovered short-range ordering (SRO) or nanoscale Cr2N precipitates in the γ matrix of the N-containing alloy specimens, and it was revealed that both SRO and nanoprecipitates function as obstacles to the glide of partial dislocations and consequently significantly affect the kinetics of the γ→ε martensitic transformation. Since the formation of ε martensite plays a crucial role in plastic deformation and wear behavior, the developed nanostructural modification associated with nitrogen addition must be a promising strategy for highly durable orthopedic implants.

  5. The low energy signaling network.

    PubMed

    Tomé, Filipa; Nägele, Thomas; Adamo, Mattia; Garg, Abhroop; Marco-Llorca, Carles; Nukarinen, Ella; Pedrotti, Lorenzo; Peviani, Alessia; Simeunovic, Andrea; Tatkiewicz, Anna; Tomar, Monika; Gamm, Magdalena

    2014-01-01

    Stress impacts negatively on plant growth and crop productivity, caicultural production worldwide. Throughout their life, plants are often confronted with multiple types of stress that affect overall cellular energy status and activate energy-saving responses. The resulting low energy syndrome (LES) includes transcriptional, translational, and metabolic reprogramming and is essential for stress adaptation. The conserved kinases sucrose-non-fermenting-1-related protein kinase-1 (SnRK1) and target of rapamycin (TOR) play central roles in the regulation of LES in response to stress conditions, affecting cellular processes and leading to growth arrest and metabolic reprogramming. We review the current understanding of how TOR and SnRK1 are involved in regulating the response of plants to low energy conditions. The central role in the regulation of cellular processes, the reprogramming of metabolism, and the phenotypic consequences of these two kinases will be discussed in light of current knowledge and potential future developments.

  6. The Low Energy Neutrino Factory

    SciTech Connect

    Bross, Alan; Geer, Steve; Ellis, Malcolm; Fernandez Martinez, Enrique; Li, Tracey; Pascoli, Silvia; Mena, Olga

    2010-03-30

    We show that a low energy neutrino factory with a baseline of 1300 km and muon energy of 4.5 GeV has an excellent physics reach. The results of our optimisation studies demonstrate that such a setup can have remarkable sensitivity to theta{sub 13} and delta for sin{sup 2}(2theta{sub 13})>10{sup -4}, and to the mass hierarchy for sin{sup 2}(2theta{sub 13})>10{sup -3}. We also illustrate the power of the unique combination of golden and platinum channels accessible to the low energy neutrino factory. We have considered both a 20 kton totally active scintillating detector and a 100 kton liquid argon detector as possible detector technologies, finding that a liquid argon detector with very good background rejection can produce sensitivity to theta{sub 13} and delta with that of the International Design Study neutrino factory.

  7. Review of Low Energy Neutrinos

    NASA Astrophysics Data System (ADS)

    Vergados, J. D.

    2007-04-01

    Some issues regarding low energy neutrinos are reviewed. We focus on three aspects i)We show that by employing very low energy (a few keV) electron neutrinos, neutrino disappearance oscillations can be investigated by detecting recoiling electrons with low threshold spherical gaseous TPC's. In such an experiment, which is sensitive to the small mixing angle θ13, the novel feature is that the oscillation length is so small that the full oscillation takes place inside the detector. Thus one can determine accurately all the oscillation parameters and, in particular, measure or set a good limit on θ13. ii) Low threshold gaseous TPC detectors can also be used in detecting nuclear recoils by exploiting the neutral current interaction. Thus these robust and stable detectors can be employed in supernova neutrino detection. iii) The lepton violating neutrinoless double decay is investigated focusing on how the absolute neutrino mass can be extracted from the data.

  8. The low energy signaling network

    PubMed Central

    Tomé, Filipa; Nägele, Thomas; Adamo, Mattia; Garg, Abhroop; Marco-llorca, Carles; Nukarinen, Ella; Pedrotti, Lorenzo; Peviani, Alessia; Simeunovic, Andrea; Tatkiewicz, Anna; Tomar, Monika; Gamm, Magdalena

    2014-01-01

    Stress impacts negatively on plant growth and crop productivity, caicultural production worldwide. Throughout their life, plants are often confronted with multiple types of stress that affect overall cellular energy status and activate energy-saving responses. The resulting low energy syndrome (LES) includes transcriptional, translational, and metabolic reprogramming and is essential for stress adaptation. The conserved kinases sucrose-non-fermenting-1-related protein kinase-1 (SnRK1) and target of rapamycin (TOR) play central roles in the regulation of LES in response to stress conditions, affecting cellular processes and leading to growth arrest and metabolic reprogramming. We review the current understanding of how TOR and SnRK1 are involved in regulating the response of plants to low energy conditions. The central role in the regulation of cellular processes, the reprogramming of metabolism, and the phenotypic consequences of these two kinases will be discussed in light of current knowledge and potential future developments. PMID:25101105

  9. Hemocompatibility of nitrogen-doped, hydrogen-free diamond-like carbon prepared by nitrogen plasma immersion ion implantation-deposition.

    PubMed

    Kwok, Sunny C H; Yang, Ping; Wang, Jin; Liu, Xuanyong; Chu, Paul K

    2004-07-01

    Amorphous hydrogenated carbon (a-C:H) has been shown to be a potential material in biomedical devices such as artificial heart valves, bone implants, and so on because of its chemical inertness, low coefficient of friction, high wear resistance, and good biocompatibility. However, the biomedical characteristics such as blood compatibility of doped hydrogen-free diamond-like carbon (DLC) have not been investigated in details. We recently began to investigate the potential use of nitrogen-doped, hydrogen-free DLC in artificial heart valves. In our experiments, a series of hydrogen-free DLC films doped with nitrogen were synthesized by plasma immersion ion implantation-deposition (PIII-D) utilizing a pulsed vacuum arc plasma source and different N to Ar (FN/FAr) gas mixtures in the plasma chamber. The structures and properties of the film were evaluated by Raman spectroscopy, Rutherford backscattering spectrometry (RBS), and X-ray photoelectron spectroscopy (XPS). To assess the blood compatibility of the films and the impact on the blood compatibility by the presence of nitrogen, platelet adhesion tests were conducted. Our results indicate that the blood compatibility of both hydrogen-free carbon films (a-C) and amorphous carbon nitride films are better than that of low-temperature isotropic pyrolytic carbon (LTIC). The experimental results are consistent with the relative theory of interfacial energy and surface tension including both dispersion and polar components. Our results also indicate that an optimal fraction of sp2 bonding is desirable, but an excessively high nitrogen concentration degrades the properties to an extent that the biocompatibility can be worse than that of LTIC.

  10. Deposition of silicon oxynitride films by low energy ion beam assisted nitridation at room temperature

    NASA Astrophysics Data System (ADS)

    Youroukov, S.; Kitova, S.; Danev, G.

    2008-05-01

    The possibility is studied of growing thin silicon oxynitride films by e-gun evaporation of SiO and SiO2 together with concurrent bombardment with low energy N2+ ions from a cyclotron resonance (ECR) source at room temperature of substrates. The degree of nitridation and oxidation of the films is investigated by means of X-ray spectroscopy. The optical characteristics of the films, their environmental stability and adhesion to different substrates are examined. The results obtained show than the films deposited are transparent. It is found that in the case of SiO evaporation with concurrent N2+ ion bombardment, reactive implantation of nitrogen within the films takes place at room temperature of the substrate with the formation of a new silicon oxynitride compound even at low ion energy (150-200 eV).

  11. Bias in bonding behavior among boron, carbon, and nitrogen atoms in ion implanted a-BN, a-BC, and diamond like carbon films

    SciTech Connect

    Genisel, Mustafa Fatih; Uddin, Md. Nizam; Say, Zafer; Bengu, Erman; Kulakci, Mustafa; Turan, Rasit; Gulseren, Oguz

    2011-10-01

    In this study, we implanted N{sup +} and N{sub 2}{sup +} ions into sputter deposited amorphous boron carbide (a-BC) and diamond like carbon (DLC) thin films in an effort to understand the chemical bonding involved and investigate possible phase separation routes in boron carbon nitride (BCN) films. In addition, we investigated the effect of implanted C{sup +} ions in sputter deposited amorphous boron nitride (a-BN) films. Implanted ion energies for all ion species were set at 40 KeV. Implanted films were then analyzed using x-ray photoelectron spectroscopy (XPS). The changes in the chemical composition and bonding chemistry due to ion-implantation were examined at different depths of the films using sequential ion-beam etching and high resolution XPS analysis cycles. A comparative analysis has been made with the results from sputter deposited BCN films suggesting that implanted nitrogen and carbon atoms behaved very similar to nitrogen and carbon atoms in sputter deposited BCN films. We found that implanted nitrogen atoms would prefer bonding to carbon atoms in the films only if there is no boron atom in the vicinity or after all available boron atoms have been saturated with nitrogen. Implanted carbon atoms also preferred to either bond with available boron atoms or, more likely bonded with other implanted carbon atoms. These results were also supported by ab-initio density functional theory calculations which indicated that carbon-carbon bonds were energetically preferable to carbon-boron and carbon-nitrogen bonds.

  12. Effects of carbon and nitrogen plasma immersion ion implantation on in vitro and in vivo biocompatibility of titanium alloy.

    PubMed

    Zhao, Ying; Wong, Sze Man; Wong, Hoi Man; Wu, Shuilin; Hu, Tao; Yeung, Kelvin W K; Chu, Paul K

    2013-02-01

    Growth of bony tissues on titanium biomedical implants can be time-consuming, thereby prolonging recovery and hospitalization after surgery and a method to improve and expedite tissue-implant integration and healing is thus of scientific and clinical interests. In this work, nitrogen and carbon plasma immersion ion implantation (N-PIII and C-PIII) is conducted to modify Ti-6Al-4V to produce a graded surface layer composed of TiN and TiC, respectively. Both PIII processes do not significantly alter the surface hydrophilicity but increase the surface roughness and corrosion resistance. In vitro studies disclose improved cell adhesion and proliferation of MC3T3-E1 preosteoblasts and L929 fibroblasts after PIII. Micro-CT evaluation conducted 1 to 12 weeks after surgery reveals larger average bone volumes and less bone resorption on the N-PIII and C-PIII titanium alloy pins than the unimplanted one at every time point. The enhancements observed from both the in vitro and in vivo studies can be attributed to the good cytocompatibility, roughness, and corrosion resistance of the TiN and TiC structures which stimulate the response of preosteoblasts and fibroblasts and induce early bone formation. Comparing the two PIII processes, N-PIII is more effective and our results suggest a simple and practical means to improve the surface biocompatibility of medical-grade titanium alloy implants.

  13. Fusion reactions at low energy

    SciTech Connect

    Beckerman, M.

    1985-01-01

    Fusion measurement methods at low energies are briefly described, and experimental and theoretical fusion cross sections for /sup 58/Ni + /sup 58/Ni, /sup 58/Ni + /sup 64/Ni and /sup 64/Ni + /sup 64/Ni reactions are discussed. It is shown that quantal tunneling calculations do not describe the near- and sub-barrier behavior of the fusion data. Instead, the WKB predictions fall progressively further blow the experimental results as the energy is lowered. At far subbarrier energies the measured cross sections exceed the WKB predictions by more than three orders of magnitude. The unexpectedly strong dependence of the fusion probability upon the nuclear valence structure is illustrated and discussed. The relationship of channel coupling and quantal tunneling is discussed. In conclusion, it was established that atomic nuclei fuse far more readily at low energies that would be expected from quantal tunneling considerations alone. It was found that the behavior of the cross sections for fusion depends strongly upon the valence structure of the collision partners. This structural dependence extends from light 1p-shell systems to systems involving nearly 200 nucleons. These new phenomena may be viewed as characterizing the tunneling of a quantal system with many degrees of freedom. The failure of standard tunneling models may be understood as resulting from the ability of the dinuclear system to tunnel into the classically forbidden region by means of couplings to intrinsic degrees of freedom. 38 refs. (WHK)

  14. High Resolution Rutherford Back Scattering Estimation of the Surface Implanted Nitrogen Ion by Using Plasma-based Ion Implantation

    NASA Astrophysics Data System (ADS)

    Tanaka, Takeshi; Takagi, Toshinori

    Plasma-based ion implantation (PBII) with negative voltage pulses to the test specimen has been applied to the sterilization process as a technique suitable for three-dimensional work pieces. Pulsed high negative voltage (5 μs pulse width, 300 pulses/s, -800 V to -15 kV) was applied to the electrode in this process at a gas pressure of 2.4 Pa of N2. We found that the PBII process, in which (N2 gas self-ignitted plasma generated by only pulsed voltages is used) reduces the numbers of active Bacillus pumilus cell. The number of bacteria survivors was reduced by 10-5 x with 5 min exposure. As the ion energy is one of the important processing parameters on sterilization of the surface, the ion energy is discussed from the high resolution RBS depth profile.

  15. Low energy p p physics

    SciTech Connect

    Amsler, C.; Crowe, K. . Inst. fuer Physik; Lawrence Berkeley Lab., CA )

    1989-02-01

    A detailed investigation of proton-antiproton interactions at low energy has become feasible with the commissioning of the LEAR facility in 1983. We shall shortly review the status of {bar p}p annihilation at rest and the physics motivations for second generation experiments with the Crystal Barrel detector. This type of detector would be adequate for the study of both Kp and {bar p}p interactions on an extracted beam of the KAON Factory. We shall conclude with a few remarks on the physics opportunities with {bar p}'s at the KAON Factory which, in our opinion, will not be covered by the present LEAR facility. 11 refs., 10 figs., 2 tabs.

  16. Low-Energy Proton Testing Methodology

    NASA Technical Reports Server (NTRS)

    Pellish, Jonathan A.; Marshall, Paul W.; Heidel, David F.; Schwank, James R.; Shaneyfelt, Marty R.; Xapsos, M.A.; Ladbury, Raymond L.; LaBel, Kenneth A.; Berg, Melanie; Kim, Hak S.; Phan, Anthony; Friendlich, M.R.; Rodbell, Kenneth P.; Hakey, Mark C.; Dodd, Paul E.; Reed, Robert A.; Weller, Robert A.; Mendenhall, Marcus H.; Sierawski, B.D.

    2009-01-01

    Use of low-energy protons and high-energy light ions is becoming necessary to investigate current-generation SEU thresholds. Systematic errors can dominate measurements made with low-energy protons. Range and energy straggling contribute to systematic error. Low-energy proton testing is not a step-and-repeat process. Low-energy protons and high-energy light ions can be used to measure SEU cross section of single sensitive features; important for simulation.

  17. The relationship between depth profiles of nitrogen concentration, hardness, and wear rate in ion-implanted Ti—6Al—4V

    NASA Astrophysics Data System (ADS)

    Blanchard, James P.; Chen, An; Qiu, Bogin

    1993-07-01

    The property changes induced by nitrogen ion implantation of Ti sbnd 6Al sbnd 4V alloys are considered, with emphasis on the effects of the nitrogen concentration profiles on hardness and wear rate. The comparison of the measured hardness profile to the profile from a finite element simulation reinforces the assumption that nitride formation, rather than damage, is the primary hardening mechanism. In addition, these techniques allow determination of the increase in the yield stress caused by the ion implantation. In this case, a ten-fold increase in the yield stress is found. Wear rate profiles are compared to the nitrogen concentration profile and are found to be low at depths greater than the nitrogen profile depth. This is assumed to occur because of the geometry of the wear test device.

  18. Low energy neutral atom imaging

    SciTech Connect

    McComas, D.J.; Funsten, H.O.; Gosling, J.T.; Moore, K.R.; Thomsen, M.F.

    1992-01-01

    Energetic neutral atom (ENA) and low energy neutral atom (LENA) imaging of space plasmas are emerging new technology which promises to revolutionize the way we view and understand large scale space plasma phenomena and dynamics. ENAs and LENAs are produced in the magnetosphere by charge exchange between energetic and plasma ions and cold geocoronal neutrals. While imaging techniques have been previously developed for observing ENAs, with energies above several tens of keV, most of the ions found in the terrestrial magnetosphere have lower energies. We recently suggested that LENAs could be imaged by first converting the neutrals to ions and then electrostatically analyzing them to reject the UV background. In this paper we extend this work to examine in detail the sensor elements needed to make an LENA imager. These elements are (1) a biased collimator to remove the ambient plasma ions and electrons and set the azimuthal field-of-view; (2) a charge modifier to convert a portion of the incident LENAs to ions; (3) an electrostatic analyzer to reject UV light and set the energy passband; and (4) a coincidence detector to measure converted LENAs while rejecting noise and penetrating radiation. We also examine the issue of LENA imager sensitivity and describe ways of optimizing sensitivity in the various sensor components. Finally, we demonstrate in detail how these general considerations are implemented by describing one relatively straightforward design based on a hemispherical electrostatic analyzer.

  19. Intense low energy positron beams

    SciTech Connect

    Lynn, K.G.; Jacobsen, F.M.

    1993-12-31

    Intense positron beams are under development or being considered at several laboratories. Already today a few accelerator based high intensity, low brightness e{sup +} beams exist producing of the order of 10{sup 8} {minus} 10{sup 9} e{sup +}/sec. Several laboratories are aiming at high intensity, high brightness e{sup +} beams with intensities greater than 10{sup 9} e{sup +}/sec and current densities of the order of 10{sup 13} {minus} 10{sup 14} e{sup +} sec{sup {minus}} {sup 1}cm{sup {minus}2}. Intense e{sup +} beams can be realized in two ways (or in a combination thereof) either through a development of more efficient B{sup +} moderators or by increasing the available activity of B{sup +} particles. In this review we shall mainly concentrate on the latter approach. In atomic physics the main trust for these developments is to be able to measure differential and high energy cross-sections in e{sup +} collisions with atoms and molecules. Within solid state physics high intensity, high brightness e{sup +} beams are in demand in areas such as the re-emission e{sup +} microscope, two dimensional angular correlation of annihilation radiation, low energy e{sup +} diffraction and other fields. Intense e{sup +} beams are also important for the development of positronium beams, as well as exotic experiments such as Bose condensation and Ps liquid studies.

  20. Photoelectrocatalytic properties of nitrogen doped TiO2/Ti photoelectrode prepared by plasma based ion implantation under visible light.

    PubMed

    Han, Lei; Xin, Yanjun; Liu, Huiling; Ma, Xinxin; Tang, Guangze

    2010-03-15

    Nitrogen doped TiO(2)/Ti photoelectrodes were prepared by a sequence of anodization and plasma based ion implantation (PBII). The properties of this photoelectrode were characterized by scanning electronic microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), X-ray photoelectron spectrometry (XPS), Ultra violet/visible light diffuse reflectance spectra (UV/vis/DRS), surface photovoltage (SPV), etc. Photoelectrocatalytic (PEC) performance of N-doped TiO(2)/Ti photoelectrode was tested under visible light irradiation. Their photocatalytic activity was evaluated by degradation of Rhodamine B (Rh.B). The results of XPS showed that nitrogen element was in form of three species, i.e. beta-N, molecular gamma-N and O-Ti-N, which existed in the lattices of TiO(2) and gaps between molecules. The results of UV/vis/DRS spectra and SPV revealed that proper doping of nitrogen could expand the response of photoelectrodes towards visible light and diminish the recombination of photo-generated holes and electrons, respectively. The photoelectrocatalytic activity of N-doped TiO(2)/Ti photoelectrodes was superior to those of undoped one under visible light region irradiation.

  1. Nitrogen

    USGS Publications Warehouse

    Apodaca, Lori E.

    2013-01-01

    The article presents an overview of the nitrogen chemical market as of July 2013, including the production of ammonia compounds. Industrial uses for ammonia include fertilizers, explosives, and plastics. Other topics include industrial capacity of U.S. ammonia producers CF Industries Holdings Inc., Koch Nitrogen Co., PCS Nitrogen, Inc., and Agrium Inc., the impact of natural gas prices on the nitrogen industry, and demand for corn crops for ethanol production.

  2. Low-Energy Sputtering Research

    NASA Technical Reports Server (NTRS)

    Ray, P. K.; Shutthanandan, V.

    1999-01-01

    An experimental study is described to measure low-energy (less than 600 eV) sputtering yields of molybdenum with xenon ions using Rutherford backscattering spectroscopy (RBS) and secondary neutral mass spectroscopy (SNMS). An ion gun was used to generate the ion beam. The ion current density at the target surface was approximately 30 (micro)A/sq cm. For RBS measurements, the sputtered material was collected on a thin aluminum strip which was mounted on a semi-circular collector plate. The target was bombarded with 200 and 500 eV xenon ions at normal incidence. The differential sputtering yields were measured using the RBS method with 1 MeV helium ions. The differential yields were fitted with a cosine fitting function and integrated with respect to the solid angle to provide the total sputtering yields. The sputtering yields obtained using the RBS method are in reasonable agreement with those measured by other researchers using different techniques. For the SNMS measurements, 150 to 600 eV xenon ions were used at 50deg angle of incidence. The SNMS spectra were converted to sputtering yields for perpendicular incidence by normalizing SNMS spectral data at 500 eV with the yield measured by Rutherford backscattering spectrometry. Sputtering yields as well as the shape of the yield-energy curve obtained in this manner are in reasonable agreement with those measured by other researchers using different techniques. Sputtering yields calculated by using two semi-spherical formulations agree reasonably well with measured data. The isotopic composition of secondary ions were measured by bombarding copper with xenon ions at energies ranging from 100 eV to 1.5 keV. The secondary ion flux was found to be enriched in heavy isotopes at low incident ion energies. The heavy isotope enrichment was observed to decrease with increasing impact energy. Beyond 700 eV, light isotopes were sputtered preferentially with the enrichment remaining nearly constant.

  3. Coherent transverse-optical phonon generation induced by lattice defects in nitrogen-ion-implanted GaAs

    NASA Astrophysics Data System (ADS)

    Kim, J. S.; Ryu, H. C.; Kim, S. H.; Kim, H.; Rho, H.; Kim, Y. J.; Lim, Y. S.; Yee, K. J.

    2013-10-01

    We describe our observation of coherent phonon oscillations of X-point zone-boundary transverse-optical (TO) mode, TO(X), in nitrogen-ion-implanted GaAs that has been annealed at high temperatures. With the TO(X) mode being forbidden from the Raman selection rule in pure zinc-blende GaAs, the lattice defects have provided additional momentum for phonon generation. Annealing-induced structural modifications were demonstrated through X-ray diffraction, transmission electron microscopy, and Raman scattering measurements. The polarization dependence of the TO(X) mode was compared with that of the longitudinal optical mode, and the temperature dependence of the TO(X) phonon dephasing was also investigated.

  4. Low Energy Defibrillation in Human Cardiac Tissue: A Simulation Study

    PubMed Central

    Morgan, Stuart W.; Plank, Gernot; Biktasheva, Irina V.; Biktashev, Vadim N.

    2009-01-01

    We aim to assess the effectiveness of feedback-controlled resonant drift pacing as a method for low energy defibrillation. Antitachycardia pacing is the only low energy defibrillation approach to have gained clinical significance, but it is still suboptimal. Low energy defibrillation would avoid adverse side effects associated with high voltage shocks and allow the application of implantable cardioverter defibrillator (ICD) therapy, in cases where such therapy is not tolerated today. We present results of computer simulations of a bidomain model of cardiac tissue with human atrial ionic kinetics. Reentry was initiated and low energy shocks were applied with the same period as the reentry, using feedback to maintain resonance. We demonstrate that such stimulation can move the core of reentrant patterns, in the direction that depends on the location of the electrodes and the time delay in the feedback. Termination of reentry is achieved with shock strength one-order-of-magnitude weaker than in conventional single-shock defibrillation. We conclude that resonant drift pacing can terminate reentry at a fraction of the shock strength currently used for defibrillation and can potentially work where antitachycardia pacing fails, due to the feedback mechanisms. Success depends on a number of details that these numerical simulations have uncovered. PMID:19217854

  5. Phase formation and mechanical/tribological modification induced by nitrogen high temperature plasma based ion implantation into molybdenum

    NASA Astrophysics Data System (ADS)

    Carreri, F. C.; Oliveira, R. M.; Oliveira, A. C.; Silva, M. M. N. F.; Ueda, M.; Silva, M. M.; Pichon, L.

    2014-08-01

    Transition metal nitrides present high hardness, good wear resistance and chemical stability. The formation of a surface layer of these materials on different types of substrates can improve surface properties without changing bulk characteristics. Molybdenum is used in many technological applications and the search for ways to effectively improve its properties is justified. In this work nitrogen ions were implanted into molybdenum by means of high temperature plasma based ion implantation (HTPBII), in order to produce a layer of molybdenum nitride on the surface of the material. The treatment was performed in the temperature range of 800-1200 °C, for 1 h. X-ray diffraction spectra showed the presence of the cubic-Mo2N phase in most of the samples. The tetragonal-Mo2N phase was also observed, depending on treatment conditions. Glow discharge optical emission spectroscopy was used to study the composition and thickness of the nitride layer. A 12 μm thick Mo2N layer was observed for samples treated at 1100 °C, although beyond this temperature threshold, a significant amount of nitride can no longer be produced. In relation to the surface mechanical properties, a ninefold increase in surface hardness was obtained, as well as a decrease in the friction coefficient. Wear against an alumina ball was not observed.

  6. Production of [15O]Water at Low-Energy Proton Cyclotrons

    SciTech Connect

    Powell, James; O'Neil, James P.

    2005-12-12

    We report a simple system for producing [15O]H2O from nitrogen-15 in a nitrogen/hydrogen gas target with recycling of the target nitrogen, allowing production on low-energy proton-only accelerators with minimal consumption of isotopically enriched nitrogen-15. The radiolabeled water is separated from the target gas and radiolytically produced ammonia by temporary freezing in a small trap at -40 C.

  7. ECR Based Low Energy Ion Beam Facility at VECC, Kolkata

    NASA Astrophysics Data System (ADS)

    Taki, G. S.; Chakraborty, D. K.; Ghosh, Subhash; Majhi, S.; Pal, Gautam; Mallik, C.; Bhandari, R. K.; Krishna, J. B. M.; Dey, K.; Sinha, A. K.

    2012-11-01

    A low energy heavy ion irradiation/implantation facility has been developed at VECC, Kolkata for materials science and atomic physics research, utilizing indigenously developed 6.4 GHz ECR ion source. The facility provides high charge state ion beams of N, O, Ne, Ar, S, Kr, Xe, Fe, Ti, Hf etc. up to a few micro amperes to an energy of 10 keV per charge state.The beam energy can be further enhanced by floating the target at a negative potential (up to 25 kV). The ion beam is focused to a spot of about 2 mm diameter on the target using a set of glaser lenses. A x-y scanner is used to scan the beam over a target area of 10 mm x 10 mm to obtain uniform implantation. The recently commissioned multi facility sample chamber has provision for mounting multiple samples on indigenously developed disposable beam viewers for insitu beam viewing during implantation. The ionization chamber of ECR source is mainly pumped by ECR plasma. An additional pumping speed has been provided through extraction hole and pumping slots to obtain low base pressure. In the ion source, base pressure of 1x10-7 Torr in injector stage and ~5x10-8 Torr in extraction chamber have been routinely obtained. The ultra-high vacuum multi facility experimental chamber is generally kept at ~ 1x10-7 Torr during implantation on the targets. This facility is a unique tool for studying fundamental and technologically important problems of materials science and atomic physics research. High ion flux available from this machine is suitable for generating high defect densities i.e. high value of displacement-per-atom (dpa). Recently this facility has been used for studies like "Tunability of dielectric constant of conducting polymer Polyaniline (PANI) by low energy Ar9+ irradiation" and "Fe10+ implantation in ZnO for synthesis of dilute magnetic semiconductor".

  8. Effect of nitrogen high temperature plasma based ion implantation on the creep behavior of Ti-6Al-4V alloy

    NASA Astrophysics Data System (ADS)

    Oliveira, A. C.; Oliveira, R. M.; Reis, D. A. P.; Carreri, F. C.

    2014-08-01

    Nitrogen high temperature plasma based ion implantation (HTPBII) performed on Ti-6Al-4V significantly improved the creep behavior of the alloy. Treatments were performed for 1 h at a working pressure of 4 mbar and negative high voltage pulses of 7.5 kV, 30 μs and 500 Hz were applied on the specimens heated at 800 °C and 900 °C, respectively. Microstructural characterization of the treated samples revealed the formation of nitrided layers, with simultaneous formation of TiN and Ti2N. The most intense peaks of these compounds were obtained at higher treatment temperature, probably due to the diffusion of nitrogen into titanium. The presence of nitrides caused surface hardening up to three times higher in comparison with untreated alloy. Constant load creep tests were conducted on a standard creep machine in air atmosphere, at stress level of 319 MPa at 600 °C. Significant reductions of the steady-state creep rates (ɛ) were measured for martensitic Ti-6Al-4V treated by nitrogen HTPBII, reaching minimum creep rates of 0.0318 h-1 in comparison with 0.1938 h-1 for untreated sample. The improvement of the creep resistance seems to be associated with the formation of a thick nitrided layer, which acts as a barrier to oxygen diffusion into the material. In addition, the increase of the grain size generated by the heating of the substrate during the treatment can affect some creep mechanisms, leading to a significant reduction of ɛ.

  9. Chemical interaction between nitrogen and iron in silica glasses via sequential ion-implantation

    SciTech Connect

    Isobe, T.; Toriyama, T.; Weeks, R.A.; Zuhr, R.A.

    1998-08-01

    Silica glass plates (Corning 7940 excimer grade) were implanted sequentially with N{sup +} at 52 keV to different doses, ranging from 0 to 1.2{times}10{sup 17}thinspionsthinspcm{sup {minus}2}, and then with Fe{sup +} at 160 keV to 6{times}10{sup 16}thinspionsthinspcm{sup {minus}2} at room temperature and 4 {mu}Athinspcm{sup {minus}2}. The intensity of ferromagnetic magnetic resonance (FMR) absorption and the magnetization calculated by the angular dependence of the FMR field reach maxima at an N/Fe atomic ratio {approximately}0.2. Two peaks due to Fe 2p{sub 3/2} electron are observed at 707.2{plus_minus}0.2 and 710.9{plus_minus}0.2thinspeV in the x-ray photoelectron spectra. The intensity of the former relative to the latter decreases with increasing the N dose. The conversion electron M{umlt o}ssbauer spectrum reveals the formation of superparamagnetic iron nitride as well as the existence of Fe{sup 2+} and Fe{sup 3+} in silica when implanting N{sup +} to 7.5{times}10{sup 15}thinspionsthinspcm{sup {minus}2} and then {sup 57}Fe{sup +} to 6{times}10{sup 16}thinspionsthinspcm{sup {minus}2} at N/Fe=0.125. These results suggest that sequential ion-implantation of N{sup +} and Fe{sup +} produces iron nitride in silica glasses. {copyright} {ital 1998 Materials Research Society.}

  10. Study of non-linear Hall effect in nitrogen-grown ZnO microstructure and the effect of H{sup +}-implantation

    SciTech Connect

    Kumar, Yogesh Bern, Francis; Barzola-Quiquia, Jose; Lorite, Israel; Esquinazi, Pablo

    2015-07-13

    We report magnetotransport studies on microstructured ZnO film grown by pulsed laser deposition in N{sub 2} atmosphere on a-plane Al{sub 2}O{sub 3} substrates and the effect of low energy H{sup +}-implantation. Non-linearity has been found in the magnetic field dependent Hall resistance, which decreases with temperature. We explain this effect with a two-band model assuming the conduction through two different parallel channels having different types of charge carriers. Reduced non-linearity after H{sup +}-implantation in the grown film is due to the shallow-donor effect of hydrogen giving rise to an increment in the electron density, reducing the effect of the other channel.

  11. Nitrogen

    USGS Publications Warehouse

    Kramer, D.A.

    2006-01-01

    In 2005, ammonia was produced by 15 companies at 26 plants in 16 states in the United States. Of the total ammonia production capacity, 55% was centered in Louisiana, Oklahoma and Texas because of their large reserves of natural gas. US producers operated at 66% of their rated capacity. In descending order, Koch Nitrogen, Terra Industries, CF Industries, Agrium and PCS Nitrogen accounted for 81% of the US ammonia production capacity.

  12. Effects of nitrogen-related defects on visible light photocatalytic response in N{sup +} implanted TiO{sub 2}: A first-principles study

    SciTech Connect

    Senga, Junya; Tatsumi, Kazuyoshi Muto, Shunsuke; Yoshida, Tomoko

    2015-09-21

    It was found that the visible-light responsiveness of a nitrogen ion-implanted TiO{sub 2} photocatalyst was attributable to the predominant chemical states of nitrogen, depending on the local nitrogen concentration near the surface. In the present study, we examined the effects of conceivable nitrogen-related defects on the visible light responsiveness, based on electronic structures calculated from first principles. Possible chemical states were proposed by comparing previously reported experiments with the present theoretical N-K X-ray absorption spectra. The theoretically predicted visible light absorption spectra and carrier trap states due to the bandgap states associated with the defects well explained the relationship between the catalytic reactivity and the proposed chemical states.

  13. Solar-assisted low energy dwellings

    SciTech Connect

    Esbensen, T V

    1980-02-01

    The Zero Energy House Group was formed as a subproject of the CCMS Solar Energy Pilot Study in 1974 by seven participating countries experimenting with solar-assisted low-energy dwellings for temperate and northern European climatic conditions. A Zero Energy House is one in which solar energy is used to meet the reduced energy needs of buildings incorporating various thermal energy conservation features. This final report of the Zero Energy House Group includes brief descriptions of 13 major low-energy dwellings in the participating CCMS countries. An overall assessment of the state-of-the-art in solar-assisted low-energy dwellings is also included.

  14. Low energy ghosts and the Jeans' instability

    NASA Astrophysics Data System (ADS)

    Gümrükçüoǧlu, A. Emir; Mukohyama, Shinji; Sotiriou, Thomas P.

    2016-09-01

    We show that a massless canonical scalar field minimally coupled to general relativity can become a tachyonic ghost at low energies around a background in which the scalar's gradient is spacelike. By performing a canonical transformation we demonstrate that this low energy ghost can be recast, at the level of the action, in a form of a fluid that undergoes a Jeans-like instability affecting only modes with large wavelength. This illustrates that low energy tachyonic ghosts do not lead to a catastrophic quantum vacuum instability, unlike the usual high-energy ghost degrees of freedom.

  15. Surface mechanical properties, corrosion resistance, and cytocompatibility of nitrogen plasma-implanted nickel-titanium alloys: a comparative study with commonly used medical grade materials.

    PubMed

    Yeung, K W K; Poon, R W Y; Chu, P K; Chung, C Y; Liu, X Y; Lu, W W; Chan, D; Chan, S C W; Luk, K D K; Cheung, K M C

    2007-08-01

    Stainless steel and titanium alloys are the most common metallic orthopedic materials. Recently, nickel-titanium (NiTi) shape memory alloys have attracted much attention due to their shape memory effect and super-elasticity. However, this alloy consists of equal amounts of nickel and titanium, and nickel is a well known sensitizer to cause allergy or other deleterious effects in living tissues. Nickel ion leaching is correspondingly worse if the surface corrosion resistance deteriorates. We have therefore modified the NiTi surface by nitrogen plasma immersion ion implantation (PIII). The surface chemistry and corrosion resistance of the implanted samples were studied and compared with those of the untreated NiTi alloys, stainless steel, and Ti-6Al-4V alloy serving as controls. Immersion tests were carried out to investigate the extent of nickel leaching under simulated human body conditions and cytocompatibility tests were conducted using enhanced green fluorescent protein mice osteoblasts. The X-ray photoelectron spectroscopy results reveal that a thin titanium nitride (TiN) layer with higher hardness is formed on the surface after nitrogen PIII. The corrosion resistance of the implanted sample is also superior to that of the untreated NiTi and stainless steel and comparable to that of titanium alloy. The release of nickel ions is significantly reduced compared with the untreated NiTi. The sample with surface TiN exhibits the highest amount of cell proliferation whereas stainless steel fares the worst. Compared with coatings, the plasma-implanted structure does not delaminate as easily and nitrogen PIII is a viable way to improve the properties of NiTi orthopedic implants.

  16. Nitrogen

    USGS Publications Warehouse

    Apodaca, L.E.

    2012-01-01

    Ammonia was produced by 12 companies at 27 plants in 15 states in the United States during 2011. Sixty-one percent of total U.S. ammonia production capacity was centered in Louisiana, Oklahoma and Texas because of those states' large reserves of natural gas, the dominant domestic feedstock. In 2011, U.S. producers operated at about 84 percent of their rated capacity (excluding plants that were idle for the entire year). Four companies — CF Industries Holdings Inc.; Koch Nitrogen Co.; PCS Nitrogen Inc. and Agrium Inc., in descending order — accounted for 77 percent of the total U.S. ammonia production capacity.

  17. Surface modification by nitrogen plasma immersion ion implantation into new steel 460Li-21Cr in a capacitively coupled radio frequency discharge

    NASA Astrophysics Data System (ADS)

    Bhuyan, H.; Mändl, S.; Bora, B.; Favre, M.; Wyndham, E.; Maze, J. R.; Walczak, M.; Manova, D.

    2014-10-01

    A novel steel 460Li-21Cr belonging to a new generation of superferritic grade steel has been implanted with nitrogen in a low power 13.56 MHz radio frequency plasma by the plasma immersion ion implantation (PIII) technique in order to study its physical and chemical properties under different experimental conditions. We observed improved hardness and wear behavior of 460Li-21Cr steel with a layer thickness between 1.5 and 4.0 μm after 60 min implantation in the temperature range from 350 to 550 °C. The modified surface layer containing nitrogen does not show CrN in X-ray diffraction (XRD). Compared to untreated substrates, the hardness can be increased by a factor of 4, depending on the experimental conditions, and the wear behavior was also improved by two orders of magnitude. The results are very similar to those for austenitic stainless steel with a similar pronounced increase in wear resistance and plateau-like nitrogen depth profiles.

  18. In situ x-ray diffraction investigations during low energy ion nitriding of austenitic stainless steel grade 1.4571

    NASA Astrophysics Data System (ADS)

    Manova, D.; Mändl, S.; Gerlach, J. W.; Hirsch, D.; Neumann, H.; Rauschenbach, B.

    2014-09-01

    Insertion of nitrogen into austenitic stainless steel leads to anomalously fast nitrogen diffusion and the formation of an expanded face-centred cubic phase which is known to contain a large amount of mechanical stress. In situ x-ray diffraction (XRD) measurements during low energy nitrogen ion implantation into steel 316Ti at 300-550 °C allow a direct view into diffusion and phase formation. While the layer growth is directly observable from the decreasing substrate reflection intensity, the time evolution of the intensities for the expanded phase reflection is much more complex: several mechanisms including at least formation and annealing of defects, twinning, reduction of the crystal symmetry, or grain rotation may be active inside the expanded phase, besides the thermally activated decay of the metastable expanded phase. This locally varying coherence length or scattering intensity from the expanded phase is furthermore a function of temperature and time, additionally complicating the deconvolution of XRD spectra for stress and concentration gradients. As no concise modelling of this coherence length is possible at present, a simple qualitative model assuming a dependence of the scattering intensity on the depth, influence by stress and plastic flow during the nitriding process is proposed for understanding the underlying processes.

  19. Synthesis of Fe16N2 compound Free-Standing Foils with 20 MGOe Magnetic Energy Product by Nitrogen Ion-Implantation

    NASA Astrophysics Data System (ADS)

    Jiang, Yanfeng; Mehedi, Md Al; Fu, Engang; Wang, Yongqiang; Allard, Lawrence F.; Wang, Jian-Ping

    2016-05-01

    Rare-earth-free magnets are highly demanded by clean and renewable energy industries because of the supply constraints and environmental issues. A promising permanent magnet should possess high remanent magnetic flux density (Br), large coercivity (Hc) and hence large maximum magnetic energy product ((BH)max). Fe16N2 has been emerging as one of promising candidates because of the redundancy of Fe and N on the earth, its large magnetocrystalline anisotropy (Ku > 1.0 × 107 erg/cc), and large saturation magnetization (4πMs > 2.4 T). However, there is no report on the formation of Fe16N2 magnet with high Br and large Hc in bulk format before. In this paper, we successfully synthesize free-standing Fe16N2 foils with a coercivity of up to 1910 Oe and a magnetic energy product of up to 20 MGOe at room temperature. Nitrogen ion implantation is used as an alternative nitriding approach with the benefit of tunable implantation energy and fluence. An integrated synthesis technique is developed, including a direct foil-substrate bonding step, an ion implantation step and a two-step post-annealing process. With the tunable capability of the ion implantation fluence and energy, a microstructure with grain size 25–30 nm is constructed on the FeN foil sample with the implantation fluence of 5 × 1017/cm2.

  20. Nitrogen

    USGS Publications Warehouse

    Kramer, D.A.

    2007-01-01

    Ammonia was produced by 15 companies at 25 plants in 16 states in the United States during 2006. Fifty-seven percent of U.S. ammonia production capacity was centered in Louisiana, Oklahoma and Texas because of their large reserves of natural gas, the dominant domestic feedstock. In 2006, U.S. producers operated at about 72 percent of their rated capacity (excluding plants that were idle for the entire year). Five companies, Koch Nitrogen, Terra Industries, CF Industries, PCS Nitro-gen, and Agrium, in descending order, accounted for 79 percent U.S. ammonia production capacity. The United States was the world's fourth-ranked ammonia producer and consumer following China, India and Russia. Urea, ammonium nitrate, ammonium phosphates, nitric acid and ammonium sulfate were the major derivatives of ammonia in the United States, in descending order of importance.

  1. Nitrogen

    USGS Publications Warehouse

    Apodaca, L.E.

    2010-01-01

    Ammonia was produced by 13 companies at 23 plants in 16 states during 2009. Sixty percent of all U.S. ammonia production capacity was centered in Louisiana. Oklahoma and Texas because of those states' large reserves of natural gas, the dominant domestic feedstock. In 2009, U.S. producers operated at about 83 percent of their rated capacity (excluding plants that were idle for the entire year). Five companies — Koch Nitrogen Co.; Terra Industries Inc.; CF Industries Inc.; PCS Nitrogen Inc. and Agrium Inc., in descending order — accounted for 80 percent of the total U.S. ammonia production capacity. U.S. production was estimated to be 7.7 Mt (8.5 million st) of nitrogen (N) content in 2009 compared with 7.85 Mt (8.65 million st) of N content in 2008. Apparent consumption was estimated to have decreased to 12.1 Mt (13.3 million st) of N, a 10-percent decrease from 2008. The United States was the world's fourth-ranked ammonia producer and consumer following China, India and Russia. Urea, ammonium nitrate, ammonium phosphates, nitric acid and ammonium sulfate were the major derivatives of ammonia in the United States, in descending order of importance.

  2. Surface and bulk-loss reduction research by low-energy hydrogen doping

    NASA Technical Reports Server (NTRS)

    Fonash, S.

    1985-01-01

    Surface and bulk loss reduction by low energy hydrogen doping of silicon solar cells was examined. Hydrogen ions provided a suppression of space charge recombination currents. Implantation of hydrogen followed by the anneal cycle caused more redistribution of boron than the anneal which could complicate processing. It was demonstrated that passivation leads to space charge current reduction.

  3. Positron annihilation study of P implanted Si

    SciTech Connect

    Asoka-Kumar, P.; Au, H.L.; Lynn, K.G. ); Sferlazzo, P. . SED Division)

    1992-01-01

    High-energy ion implantation (above 200 keV) is now commonly used in a variety of VLSI processes. The high energy required for these implants is often achieved by implanting multiply charged ions, which inevitably brings in the problem of low-energy ion contamination. The low-energy contamination is difficult to diagnose and detect. Positron annihilation spectroscopy is used to examine the defect distributions in these high energy implants with varying degrees of contamination.

  4. Positron annihilation study of P implanted Si

    SciTech Connect

    Asoka-Kumar, P.; Au, H.L.; Lynn, K.G.; Sferlazzo, P.

    1992-12-01

    High-energy ion implantation (above 200 keV) is now commonly used in a variety of VLSI processes. The high energy required for these implants is often achieved by implanting multiply charged ions, which inevitably brings in the problem of low-energy ion contamination. The low-energy contamination is difficult to diagnose and detect. Positron annihilation spectroscopy is used to examine the defect distributions in these high energy implants with varying degrees of contamination.

  5. Improvements of anti-corrosion and mechanical properties of NiTi orthopedic materials by acetylene, nitrogen and oxygen plasma immersion ion implantation

    NASA Astrophysics Data System (ADS)

    Poon, Ray W. Y.; Ho, Joan P. Y.; Liu, Xuanyong; Chung, C. Y.; Chu, Paul K.; Yeung, Kelvin W. K.; Lu, William W.; Cheung, Kenneth M. C.

    2005-08-01

    Nickel-titanium shape memory alloys (NiTi) are useful materials in orthopedics and orthodontics due to their unique super-elasticity and shape memory effects. However, the problem associated with the release of harmful Ni ions to human tissues and fluids has been raising safety concern. Hence, it is necessary to produce a surface barrier to impede the out-diffusion of Ni ions from the materials. We have conducted acetylene, nitrogen and oxygen plasma immersion ion implantation (PIII) into NiTi alloys in an attempt to improve the surface properties. All the implanted and annealed samples surfaces exhibit outstanding corrosion and Ni out-diffusion resistance. Besides, the implanted layers are mechanically stronger than the substrate underneath. XPS analyses disclose that the layer formed by C2H2 PIII is composed of mainly TiCx with increasing Ti to C concentration ratios towards the bulk. The nitrogen PIII layer is observed to be TiN, whereas the oxygen PIII layer is composed of oxides of Ti4+, Ti3+ and Ti2+.

  6. The Simbol-X Low Energy Detector

    SciTech Connect

    Lechner, Peter

    2009-05-11

    For the Low Energy Detector of Simbol-X a new type of active pixel sensor based on the integrated amplifier DEPFET has been developed. This concept combines large area, scalable pixel size, low noise, and ultra-fast readout. Flight representative prototypes have been processed with a performance matching the Simbol-X specifications and demonstrating the technology readiness.

  7. The Simbol-X Low Energy Detector

    NASA Astrophysics Data System (ADS)

    Lechner, Peter

    2009-05-01

    For the Low Energy Detector of Simbol-X a new type of active pixel sensor based on the integrated amplifier DEPFET has been developed. This concept combines large area, scalable pixel size, low noise, and ultra-fast readout. Flight representative prototypes have been processed with a performance matching the Simbol-X specifications and demonstrating the technology readiness.

  8. Studies in Low-Energy Nuclear Science

    SciTech Connect

    Carl R. Brune; Steven M. Grimes

    2010-01-13

    This report presents a summary of research projects in the area of low energy nuclear reactions and structure, carried out between March 1, 2006 and October 31, 2009 which were supported by U.S. DOE grant number DE-FG52-06NA26187.

  9. Low-energy Neutrino Astronomy in LENA

    NASA Astrophysics Data System (ADS)

    Wurm, M.; Bick, D.; Enqvist, T.; Hellgartner, D.; Kaiser, M.; Loo, K. K.; Lorenz, S.; Meloni, M.; Meyer, M.; Möllenberg, R.; Oberauer, L.; Soiron, M.; Smirnov, M.; Trzaska, W. H.; Wonsak, B.

    LENA (Low Energy Neutrino Astronomy) is a proposed next-generation neutrino detector based on 50 kilotons of liquid scintillator. The low detection threshold, good energy resolution and excellent background rejection inherent to the liquid-scintillator detectors make LENA a versatile observatory for low-energy neutrinos from astrophysical and terrestrial sources. In the framework of the European LAGUNA-LBNO design study, LENA is also considered as far detector for a very-long baseline neutrino beam from CERN to Pyhäsalmi (Finland). The present contribution gives an overview LENA's broad research program, highlighting the unique capabilities of liquid scintillator for the detection of low-energy neutrinos from astrophysical sources. In particular, it will focus on the precision measurement of the solar neutrino spectrum: The search for time modulations in the 7Be neutrino flux, the determination of the electron neutrino survival probability in the low-energy region of the 8B spectrum and the favorable detection conditions for neutrinos from the CNO fusion cycle.

  10. Parity violation in low-energy

    SciTech Connect

    Martin Savage

    2001-12-01

    Parity violation in low-energy nuclear observables is included in the pionless effective field theory. The model-independent relation between the parity-violating asymmetry in polarized np -> d gamma and the non-nucleon part of the deuteron anapole moment is discussed. The asymmetry in np -> d gamma computed with KSW power-counting, and recently criticized by Desplanques, is discussed.

  11. Improvement of L(+)-Lactic Acid Production of Rhizopus Oryzae by Low-Energy Ions and Analysis of Its Mechanism

    NASA Astrophysics Data System (ADS)

    Ge, Chunmei; Yang, Yingge; Fan, Yonghong; Li, Wen; Pan, Renrui; Zheng, Zhiming; Yu, Zengliang

    2008-02-01

    The wild type strain Rhizopus oryzae PW352 was mutated by means of nitrogen ion implantation (15 keV, 7.8 × 1014 ~ 2.08 × 1015 ions/cm2) to find an industrial strain with a higher L(+)-lactic acid yield, and two mutants RE3303 and RF9052 were isolated. In order to discuss the mechanism primarily, Lactate Dehydrogenase of Rhizopus oryzae was studied. While the two mutants produced L(+)-lactic acid by 75% more than the wild strain did, their specific activity of Lactate Dehydrogenase was found to be higher than that in the wild strain. The optimum temperature of Lactate Dehydrogenase in Rhizopus oryzae RF9052 was higher. Compared to the wild strain, the Michaelis constant (Km) value of Lactate Dehydrogenase in the mutants was changed. All these changes show that L(+)-lactic acid production has a correlation with the specific activity of Lactate Dehydrogenase. The low-energy ions, implanted into the strain, may improve the specific activity of Lactate Dehydrogenase by influencing its gene structure and protein structure.

  12. Low energy cyclotron for radiocarbon dating

    SciTech Connect

    Welch, J.J.

    1985-01-01

    The author built and tested a low energy cyclotron for radiocarbon dating similar to a conventional mass spectrometer. These tests clearly show that with the addition of a conventional ion source, the low energy cyclotron can perform the extremely high sensitivity /sup 14/C measurements that are now done at accelerator facilities. The author found that no significant background is present when the cyclotron is tuned to accelerate /sup 14/C negative ions and the transmission efficiency is adequate to perform radiocarbon dating on milligram samples of carbon. The internal ion source used did not produce sufficient current to detect /sup 14/C directly at modern concentrations. The author shows how a conventional carbon negative ion source located outside the cyclotron magnet, would produce sufficient beam and provide for quick sample changing to make radiocarbon dating milligram samples with a modest laboratory instrument feasible.

  13. Tissue modeling schemes in low energy breast brachytherapy

    NASA Astrophysics Data System (ADS)

    Afsharpour, Hossein; Landry, Guillaume; Reniers, Brigitte; Pignol, Jean-Philippe; Beaulieu, Luc; Verhaegen, Frank

    2011-11-01

    Breast tissue is heterogeneous and is mainly composed of glandular (G) and adipose (A) tissues. The proportion of G versus A varies considerably among the population. The absorbed dose distributions in accelerated partial breast irradiation therapy with low energy photon brachytherapy sources are very sensitive to tissue heterogeneities. Current clinical algorithms use the recommendations of the AAPM TG43 report which approximates the human tissues by unit density water. The aim of this study is to investigate various breast tissue modeling schemes for low energy brachytherapy. A special case of breast permanent seed implant is considered here. Six modeling schemes are considered. Uniform and non-uniform water breast (UWB and NUWB) consider the density but neglect the effect of the composition of tissues. The uniform and the non-uniform G/A breast (UGAB and NUGAB) as well the age-dependent breast (ADB) models consider the effect of the composition. The segmented breast tissue (SBT) method uses a density threshold to distinguish between G and A tissues. The PTV D90 metric is used for the analysis and is based on the dose to water (D90(w,m)). D90(m,m) is also reported for comparison to D90(w,m). The two-month post-implant D90(w,m) averaged over 38 patients is smaller in NUWB than in UWB by about 4.6% on average (ranging from 5% to 13%). Large average differences of G/A breast models with TG43 (17% and 26% in UGAB and NUGAB, respectively) show that the effect of the chemical composition dominates the effect of the density on dose distributions. D90(w,m) is 12% larger in SBT than in TG43 when averaged. These differences can be as low as 4% or as high as 20% when the individual patients are considered. The high sensitivity of dosimetry on the modeling scheme argues in favor of an agreement on a standard tissue modeling approach to be used in low energy breast brachytherapy. SBT appears to generate the most geometrically reliable breast tissue models in this report. This

  14. Unitarization and low-energy scattering data

    NASA Astrophysics Data System (ADS)

    Magalhães, P. C.; Robilotta, M. R.

    2014-07-01

    A procedure based on the well-known K-matrix formalism is presented, which makes patterns in inelastic regions of low-energy scattering data considerably more transparent. It relies on the use of an empirical kernel, obtained by eliminating elastic loops from the experimental amplitude. This allows structures associated with resonances, such as locations, widths, and heights, to become visible with the naked eye. The method is illustrated with a study of the P-wave Kπ amplitude.

  15. PHYSICS WITH ULTRA-LOW ENERGY ANTIPROTONS

    SciTech Connect

    M. HOLZSCHEITER

    2001-02-01

    In this report the author describes the current status of the antiproton deceleration (AD) facility at CERN, and highlights the physics program with ultra-low energy antiproton at this installation. He also comments on future possibilities provided higher intensity antiproton beams become available at Fermilab, and review possibilities for initial experiments using direct degrading of high energy antiprotons in material has been developed and proven at CERN.

  16. Low energy {bar p} physics at FNAL

    SciTech Connect

    Hsueh, S.Y.

    1992-12-01

    The charmonium formation experiment is the only low energy {bar p} experiment at FNAL. This paper describes the performance of the Fermilab {bar p} Accumulator during fixed target run for the experiment and the planned upgrades. We also discuss the proposal for the direct CP violation search in {bar p} + p {yields} {bar {Lambda}} + {Lambda} {yields} {bar p}{pi}{sup +} + p{pi}{sup {minus}}.

  17. Low-energy sterile neutrinos: Theory

    NASA Astrophysics Data System (ADS)

    Palazzo, Antonio

    2013-04-01

    Several experimental anomalies seem to point towards the existence of light sterile neutrinos. We focus on the low-energy anomalous results (the so-called gallium and reactor anomalies), which indicate a non-zero admixture U of the electron neutrino with a fourth (mostly) sterile mass eigenstate ν4. We point out that solar sector data, in combination with the precision measurement of θ13, provide the constraint |<0.041 (90% C.L.), independent of the reactor flux determinations.

  18. Targeting Low-Energy Ballistic Lunar Transfers

    NASA Technical Reports Server (NTRS)

    Parker, Jeffrey S.

    2010-01-01

    Numerous low-energy ballistic transfers exist between the Earth and Moon that require less fuel than conventional transfers, but require three or more months of transfer time. An entirely ballistic lunar transfer departs the Earth from a particular declination at some time in order to arrive at the Moon at a given time along a desirable approach. Maneuvers may be added to the trajectory in order to adjust the Earth departure to meet mission requirements. In this paper, we characterize the (Delta)V cost required to adjust a low-energy ballistic lunar transfer such that a spacecraft may depart the Earth at a desirable declination, e.g., 28.5(white bullet), on a designated date. This study identifies the optimal locations to place one or two maneuvers along a transfer to minimize the (Delta)V cost of the transfer. One practical application of this study is to characterize the launch period for a mission that aims to launch from a particular launch site, such as Cape Canaveral, Florida, and arrive at a particular orbit at the Moon on a given date using a three-month low-energy transfer.

  19. Soft X-ray bremsstrahlung and fluorescent line production in the atmosphere by low energy electrons

    NASA Technical Reports Server (NTRS)

    Kraushaar, W. L.

    1974-01-01

    The effect of low energy quasi-trapped or precipitating electrons which impact on the counter windows of soft X-ray detectors are discussed. The errors caused by X-rays produced in the residual atmosphere above a rocket-borne detector because of the resemblance to X-rays of cosmic origin are examined. The design and development of counter windows which make it possible to identify the atmospherically produced X-rays are described. Curves are presented to show the following: (1) preliminary low energy electron data from Atmospheric Explorer C, (2) X-ray flux in electron-excited nitrogen and oxygen, (3) typical proportional counter response to low energy cosmic rays, and (4) proportional counter response to X-radiation produced by electrons incident upon a gas of oxygen to nitrogen number of 0.4.

  20. Dual ions implantation of zirconium and nitrogen into magnesium alloys for enhanced corrosion resistance, antimicrobial activity and biocompatibility.

    PubMed

    Cheng, Mengqi; Qiao, Yuqin; Wang, Qi; Qin, Hui; Zhang, Xianlong; Liu, Xuanyong

    2016-12-01

    Biodegradable magnesium-based alloys have shown great potential for medical applications due to their superior biological performances and mechanical properties. However, on one hand, some side effects including inferior biocompatibility, a local high-alkaline environment and gas cavities caused by a rapid corrosion rate, hinder their clinical application. On the other hand, it is also necessary to endow Mg alloys with antibacterial properties, which are crucial for clinic orthopedic applications. In this study, Zr and N ions are simultaneously implanted into AZ91 Mg alloys by plasma immersion ion implantation (PIII). A modified layer with a thickness of approximately 80nm is formed on the surface of AZ91 Mg alloys, and the hydrophobicity and roughness of these AZ91 Mg alloys obviously increase after Zr and N implantation. The in vitro evaluations including corrosion resistance tests, antimicrobial tests and cytocompatibility and alkaline phosphatase (ALP) activity tests, revealed that the dual ions implantation of Zr and N not only enhanced the corrosion resistance of the AZ91 Mg alloy but also provided better antimicrobial properties in vitro. Furthermore, the formation of biocompatible metal nitrides and metal oxides layer in the near surface of the Zr-N-implanted AZ91 Mg alloy provided a favorable implantation surface for cell adhesion and growth, which in return further promoted the bone formation in vivo. These promising results suggest that the Zr-N-implanted AZ91 Mg alloy shows potential for future application in the orthopedic field.

  1. Synthesis of Fe16N2 compound Free-Standing Foils with 20 MGOe Magnetic Energy Product by Nitrogen Ion-Implantation

    PubMed Central

    Jiang, Yanfeng; Mehedi, Md Al; Fu, Engang; Wang, Yongqiang; Allard, Lawrence F.; Wang, Jian-Ping

    2016-01-01

    Rare-earth-free magnets are highly demanded by clean and renewable energy industries because of the supply constraints and environmental issues. A promising permanent magnet should possess high remanent magnetic flux density (Br), large coercivity (Hc) and hence large maximum magnetic energy product ((BH)max). Fe16N2 has been emerging as one of promising candidates because of the redundancy of Fe and N on the earth, its large magnetocrystalline anisotropy (Ku > 1.0 × 107 erg/cc), and large saturation magnetization (4πMs > 2.4 T). However, there is no report on the formation of Fe16N2 magnet with high Br and large Hc in bulk format before. In this paper, we successfully synthesize free-standing Fe16N2 foils with a coercivity of up to 1910 Oe and a magnetic energy product of up to 20 MGOe at room temperature. Nitrogen ion implantation is used as an alternative nitriding approach with the benefit of tunable implantation energy and fluence. An integrated synthesis technique is developed, including a direct foil-substrate bonding step, an ion implantation step and a two-step post-annealing process. With the tunable capability of the ion implantation fluence and energy, a microstructure with grain size 25–30 nm is constructed on the FeN foil sample with the implantation fluence of 5 × 1017/cm2. PMID:27145983

  2. Structure Change of PTFE by Low Energy Ion Irradiation

    NASA Astrophysics Data System (ADS)

    Watari, Kunio; Iwao, Toru; Yumoto, Motoshige

    The authors irradiate low energy nitrogen ion (100eV) on PTFE (poly-tetra-fluoro-ethylene) for surface modification. However, PTFE cannot anticipate adhesive strength improvement because it is collapse type polymer and weariness of surface occurs by ion irradiation. We paid attention to cross-linked structure to solve this problem. By this study introduce below, PTFE was changed collapse type polymer into cross-linked type polymer by rising temperature above the glass transition in the case of ion irradiation. As a result, the formation of the CF3 combination was restrained and collapse phenomenon was prevented by ion irradiation above the glass transition. In addition, it was suggested that cross-linked structure is effective for adhesive strength improvement by convolution of C1s spectrum and density profile.

  3. The Low-Energy Telescopes on EXIST

    NASA Astrophysics Data System (ADS)

    Ramsey, Brian; Kaaret, P.; Jernigan, J. G.; Remillard, R. A.; Rothschild, R.; Hong, J.; Grindlay, J. E.

    2007-05-01

    The low-energy telescopes on EXIST are a coded aperture system that will continually image the 5-30 keV sky with 1' angular resolution and 12" source localization accuracy. The good source localization accuracy is essential to uniquely identify counterparts to obscured AGN and gamma-ray bursts. A total detector area of about one square meter with 200 micron square pixel is required. We are evaluating two silicon-based technologies capable of achieving the required performance: active pixel sensors with integrated DEPFET readout, and fully pixellated hybrid sensors with CMOS readout multiplexers optimized for X-ray detection.

  4. The Low-Energy Telescopes on EXIST

    NASA Astrophysics Data System (ADS)

    Ramsey, Brian; Kaaret, Philip E.; Jernigan, J. G.; Remillard, R. A.; Rothschild, R. E.; Hong, J.; Grindlay, J. E.

    2006-12-01

    The low-energy telescopes on EXIST are a coded aperture system that will continually image the 5-30 keV sky with 1' angular resolution and 12" source localization accuracy. The good source localization accuracy is essential to uniquely identify counterparts to obscured AGN and gamma-ray bursts. A total detector area of about one square meter with 200 micron square pixel is required. We are evaluating two silicon-based technologies capable of achieving the required performance: active pixel sensors with integrated DEPFET readout, and fully pixellated hybrid sensors with CMOS readout multiplexers optimized for X-ray detection.

  5. RHIC CHALLENGES FOR LOW ENERGY OPERATIONS

    SciTech Connect

    SATOGATA,T.; BRENNAN, J.M.; DREES, A.; FEDOTOV, A.; ROSER, T.; TSOUPAS, N.

    2007-06-25

    There is significant interest in RHIC heavy ion collisions at {radical}s =5-50 GeV/u, motivated by a search for the QCD phase transition critical point. The lowest energies are well below the nominal RHIC gold injection {radical}s = 19.6 GeV/u. There are several challenges that face RHIC operations in this regime, including longitudinal acceptance, magnet field quality, lattice control, and luminosity monitoring. We report on the status of work to address these challenges, including results from beam tests of low energy RHIC operations with protons and gold.

  6. Low-Temperature Activation of Ion-Implanted Boron and Nitrogen Ions in Cd x Hg1- x Te Heteroepitaxial Layers

    NASA Astrophysics Data System (ADS)

    Voitsekhovskii, A. V.; Talipov, N. Kh.

    2013-12-01

    Processes of electrical activation of ion-implanted boron and nitrogen atoms in Cd x Hg1- x Te (CMT) heteroepitaxial layers grown by methods of molecular-beam epitaxy (HEL CMT MBE) and liquid-phase epitaxy (LPE CMT) have been investigated; likewise in bulk crystals of CMT with low-temperature annealings under anodic oxide. The possibility has been demonstrated of using anodic oxide as an efficient mask for postimplantation annealings of p-type HEL CMT MBE in the temperature interval Т = 200-250°C without disruption of the composition of the variband layer or alteration of the electrophysical properties of the structure. It has been established that in HEL CMT MBE the efficiency of activation of boron as a slowly diffusing donor impurity is lowered with growth of the dose of the B+ ions and is increased by thermal cycling from Т = 77 K to room temperature. Implanted nitrogen, in contrast to boron, is a rapidly diffusing acceptor impurity in CMT, efficiently compensating both radiation donor centers and activated boron. The degree of electrical activation of nitrogen grows substantially upon thermal cycling. It has been shown that the mobility spectrum is an efficient method for monitoring the process of electrical activation of boron in p-type HEL CMT MBE. Mesa photodiodes based on activated boron in p-type HEL CMT MBE with long-wavelength photosensitivity boundary λc = 11 μm, prepared here for the first time, had a high maximum value of the product of the differential resistance by the area of the photodiode R d A = (6 - 8)ṡ102 Ωṡcm2, product R 0 A = 5 - 6 Ωṡcm2 (at zero bias), and a diffusion ledge on the inverse branch of the current-voltage ( I- V) characteristic out to a bias voltage of 1.3 V.

  7. Low Energy Ion-Molecule Reactions

    SciTech Connect

    James M. Farrar

    2004-05-01

    This objective of this project is to study the dynamics of the interactions of low energy ions important in combustion with small molecules in the gas phase and with liquid hydrocarbon surfaces. The first of these topics is a long-standing project in our laboratory devoted to probing the key features of potential energy surfaces that control chemical reactivity. The project provides detailed information on the utilization of specific forms of incident energy, the role of preferred reagent geometries, and the disposal of total reaction energy into product degrees of freedom. We employ crossed molecular beam methods under single collision conditions, at collision energies from below one eV to several eV, to probe potential surfaces over a broad range of distances and interaction energies. These studies allow us to test and validate dynamical models describing chemical reactivity. Measurements of energy and angular distributions of the reaction products with vibrational state resolution provide the key data for these studies. We employ the crossed beam low energy mass spectrometry methods that we have developed over the last several years.

  8. Low energy antiproton possibilities at BNL

    SciTech Connect

    Lee, Y.Y.; Lowenstein, D.I.

    1987-01-01

    Antinuclear physics in the energy range of 0 to 20 GeV has long been a mainstay of the high energy physics program at BNL. The emphasis of the experimental program in the last couple of years has however moved to other areas as new facilities in the world have come on line. The initiatives stimulated by the USAF has caused a renewed interest in the low energy capabilities at BNL, which are still very competitive and considerable for the production of low energy antiprotons. A synopsis is given of the present BNL accelerator plans and the near term possibilities for a high yield antiproton production experiment. This paper does not address the longer term facility possibilities of producing ''large'' amounts of antimatter. Parenthetically, even though several aspects of the program are of little interest for this audience, such as the Relativistic Heavy Ion Collider (RHIC) and the Stretcher, it is important to understand their parameters and impact upon various possible antinucleon initiatives at BNL.

  9. Low energy cyclotron for radiocarbon dating

    SciTech Connect

    Welch, J.J.

    1984-12-01

    The measurement of naturally occurring radioisotopes whose half lives are less than a few hundred million years but more than a few years provides information about the temporal behavior of geologic and climatic processes, the temporal history of meteoritic bodies as well as the production mechanisms of these radioisotopes. A new extremely sensitive technique for measuring these radioisotopes at tandem Van de Graaff and cyclotron facilities has been very successful though the high cost and limited availability have been discouraging. We have built and tested a low energy cyclotron for radiocarbon dating similar in size to a conventional mass spectrometer. These tests clearly show that with the addition of a conventional ion source, the low energy cyclotron can perform the extremely high sensitivity /sup 14/C measurements that are now done at accelerator facilities. We found that no significant background is present when the cyclotron is tuned to accelerate /sup 14/C negative ions and the transmission efficiency is adequate to perform radiocarbon dating on milligram samples of carbon. The internal ion source used did not produce sufficient current to detect /sup 14/C directly at modern concentrations. We show how a conventional carbon negative ion source, located outside the cyclotron magnet, would produce sufficient beam and provide for quick sampling to make radiocarbon dating milligram samples with a modest laboratory instrument feasible.

  10. Low energy neutrinos in Super-Kamiokande

    NASA Astrophysics Data System (ADS)

    Sekiya, Hiroyuki

    2016-05-01

    Super-Kamiokande (SK), a 50 kton water Cherenkov detector, observes 8B solar neutrinos via neutrino-electron elastic scattering. The analysis threshold was successfully lowered to 3.5 MeV (recoil electron kinetic energy) in SK-IV. To date SK has observed solar neutrinos for 18 years. An analysis regarding possible correlations between the solar neutrino flux and the 11 year solar activity cycle is shown. With large statistics, SK searches for distortions of the solar neutrino energy spectrum caused by the MSW resonance in the core of the sun. SK also searches for a day/night solar neutrino flux asymmetry induced by the matter in the Earth. The Super-Kamiokande Gd (SK-Gd) project is the upgrade of the SK detector via the addition of water-soluble gadolinium (Gd) salt. This modification will enable it to efficiently identify low energy anti-neutrinos. SK-Gd will pursue low energy physics currently inaccessible to SK due to backgrounds. The most important will be the world’s first observation of the diffuse supernova neutrino background. The main R&D program towards SK-Gd is EG ADS: a 200 ton, fully instrumented tank built in a new cavern in the Kamioka mine.

  11. Performance monitoring of low energy house, Macclesfield

    NASA Astrophysics Data System (ADS)

    Stephen, F. R.

    1980-01-01

    The monitoring of the energy balance of a very well insulated low-energy house in Macclesfield, England is discussed. The house is an existing dwelling which had been converted into a low-energy-requiring house by the reduction of heat loss through a high level of thermal insulation and the collection of solar energy by a water cascade solar panel with warm water storage. Measurements of house temperatures, radiation, off-peak electricity consumption and hot water and heating using were performed from January to August, 1978 and reveal that the house used less than 22,000 kWh electricity during that period, compared to 55,000 kWh expected if the house had been constructed to average insulation levels. Solar energy is found to contribute only 2% of house energy requirements, with the use of a heat pump combined with the solar panel leading to greater efficiency and thus utilization. In addition, the large thermal mass and good insulation are found to improve comfort by reducing temperature fluctuations, and the ventilation and low-temperature water return system employed provided satisfactory results.

  12. Low energy ion-molecule reactions

    SciTech Connect

    Farrar, J.M.

    1993-12-01

    This project is concerned with elucidating the dynamics of elementary ion-molecule reactions at collision energies near and below 1 eV. From measurements of the angular and energy distributions of the reaction products, one can infer intimathe details about the nature of collisions leading to chemical reaction, the geometries and lifetimes of intermediate complexes that govern the reaction dynamics, and the collision energy dependence of these dynamical features. The author employs crossed-beam low energy mass spectrometry technology developed over the last several years, with the focus of current research on proton transfer and hydrogen atom transfer reactions of te O{sup {minus}} ion with species such as HF, H{sub 2}O, and NH{sub 3}.

  13. Low energy dislocation structures in epitaxy

    NASA Technical Reports Server (NTRS)

    Van Der Merwe, Jan H.; Woltersdorf, J.; Jesser, W. A.

    1986-01-01

    The principle of minimum energy was applied to epitaxial interfaces to show the interrelationship beteen misfit, overgrowth thickness and misfit dislocation spacing. The low energy dislocation configurations were presented for selected interfacial geometries. A review of the interfacial energy calculations was made and a critical assessment of the agreement between theory and experiment was presented. Modes of misfit accommodation were presented with emphasis on the distinction between kinetic effects and equilibrium conditions. Two-dimensional and three-dimensional overgrowths were treated together with interdiffusion-modified interfaces, and several models of interfacial structure were treated including the classical and the current models. The paper is concluded by indicating areas of needed investigation into interfacial structure.

  14. Low-energy pion-nucleon scattering

    SciTech Connect

    Gibbs, W.R.; Ai, L.; Kaufmann, W.B.

    1998-02-01

    An analysis of low-energy charged pion-nucleon data from recent {pi}{sup {plus_minus}}p experiments is presented. From the scattering lengths and the Goldberger-Miyazawa-Oehme (GMO) sum rule we find a value of the pion-nucleon coupling constant of f{sup 2}=0.0756{plus_minus}0.0007. We also find, contrary to most previous analyses, that the scattering volumes for the P{sub 31} and P{sub 13} partial waves are equal, within errors, corresponding to a symmetry found in the Hamiltonian of many theories. For the potential models used, the amplitudes are extrapolated into the subthreshold region to estimate the value of the {Sigma} term. Off-shell amplitudes are also provided. {copyright} {ital 1998} {ital The American Physical Society}

  15. Low-energy pion-nucleon scattering

    NASA Astrophysics Data System (ADS)

    Gibbs, W. R.; Ai, Li; Kaufmann, W. B.

    1998-02-01

    An analysis of low-energy charged pion-nucleon data from recent π+/-p experiments is presented. From the scattering lengths and the Goldberger-Miyazawa-Oehme (GMO) sum rule we find a value of the pion-nucleon coupling constant of f2=0.0756+/-0.0007. We also find, contrary to most previous analyses, that the scattering volumes for the P31 and P13 partial waves are equal, within errors, corresponding to a symmetry found in the Hamiltonian of many theories. For the potential models used, the amplitudes are extrapolated into the subthreshold region to estimate the value of the Σ term. Off-shell amplitudes are also provided.

  16. Low-energy neutrino factory design

    SciTech Connect

    Ankenbrandt, C.; Bogacz, S.A.; Bross, A.; Geer, S.; Johnstone, C.; Neuffer, D.; Popovic, M.; /Fermilab

    2009-07-01

    The design of a low-energy (4 GeV) neutrino factory (NF) is described, along with its expected performance. The neutrino factory uses a high-energy proton beam to produce charged pions. The {pi}{sup {+-}} decay to produce muons ({mu}{sup {+-}}), which are collected, accelerated, and stored in a ring with long straight sections. Muons decaying in the straight sections produce neutrino beams. The scheme is based on previous designs for higher energy neutrino factories, but has an improved bunching and phase rotation system, and new acceleration, storage ring, and detector schemes tailored to the needs of the lower energy facility. Our simulations suggest that the NF scheme we describe can produce neutrino beams generated by {approx} 1.4 x 10{sup 21} {mu}{sup +} per year decaying in a long straight section of the storage ring, and a similar number of {mu}{sup -} decays.

  17. Low-energy dynamics of gravitation

    NASA Astrophysics Data System (ADS)

    Torma, Tibor

    The present status of theories of quantum gravity are reviewed from the low energy point of view. String theory relates classical black-hole type solutions of Einstein- like equations (e.g. axidilaton gravity) to the string vacuum. Several such solutions are proposed and their properties are investigated, including their behavior under supersymmetry transformations. A general feature of all possible quantum theories of gravitation is that they lead to a field theory description at low (as compared to the Planck mass) energies. The theoretical consistency, uniqueness and consequences of such an effective theory are investigated. I show that a power counting theorem allows for the momentum expansion that defines the effective theory even in the presence of large masses. I also show that graviton-graviton scattering is free of potential infrared and collinear divergencies that plague perturbative discussions of Yang-Mills theories.

  18. Low energy consumption spintronics using multiferroic heterostructures.

    PubMed

    Trassin, Morgan

    2016-01-27

    We review the recent progress in the field of multiferroic magnetoelectric heterostructures. The lack of single phase multiferroic candidates exhibiting simultaneously strong and coupled magnetic and ferroelectric orders led to an increased effort into the development of artificial multiferroic heterostructures in which these orders are combined by assembling different materials. The magnetoelectric coupling emerging from the created interface between the ferroelectric and ferromagnetic layers can result in electrically tunable magnetic transition temperature, magnetic anisotropy or magnetization reversal. The full potential of low energy consumption magnetic based devices for spintronics lies in our understanding of the magnetoelectric coupling at the scale of the ferroic domains. Although the thin film synthesis progresses resulted into the complete control of ferroic domain ordering using epitaxial strain, the local observation of magnetoelectric coupling remains challenging. The ability to imprint ferroelectric domains into ferromagnets and to manipulate those solely using electric fields suggests new technological advances for spintronics such as magnetoelectric memories or memristors.

  19. Low-energy irradiation effects in cellulose

    SciTech Connect

    Polvi, Jussi; Nordlund, Kai

    2014-01-14

    Using molecular dynamics simulations, we determined the threshold energy for creating defects as a function of the incident angle for all carbon and oxygen atoms in the cellulose monomer. Our analysis shows that the damage threshold energy is strongly dependent on the initial recoil direction and on average slightly higher for oxygen atoms than for carbon atoms in cellulose chain. We also performed cumulative bombardment simulations mimicking low-energy electron irradiation (such as TEM imaging) on cellulose. Analyzing the results, we found that formation of free molecules and broken glucose rings were the most common forms of damage, whereas cross-linking and chain scission were less common. Pre-existing damage was found to increase the probability of cross-linking.

  20. Low-energy neutral-atom spectrometer

    SciTech Connect

    Voss, D.E.; Cohen, S.A.

    1982-04-01

    The design, calibration, and performance of a low energy neutral atom spectrometer are described. Time-of-flight analysis is used to measure the energy spectrum of charge-exchange deuterium atoms emitted from the PLT tokamak plasma in the energy range from 20 to 1000 eV. The neutral outflux is gated on a 1 ..mu..sec time scale by a slotted rotating chopper disc, supported against gravity in vacuum by magnetic levitation, and is detected by secondary electron emission from a Cu-Be plate. The energy dependent detection efficiency has been measured in particle beam experiments and on the tokamak so that the diagnostic is absolutely calibrated, allowing quantitative particle fluxes to be determined with 200 ..mu..sec time resolution. In addition to its present application as a plasma diagnostic, the instrument is capable of making a wide variety of measurements relevant to atomic and surface physics.

  1. RHIC low energy tests and initial operations

    SciTech Connect

    Satogata,T.; Ahrens, L.; Bai, M.; Brennan, J.M.; Bruno, D.; Butler, J.; Drees, A.; Fedotov, A.; Fischer, W.; Harvey, M.; Hayes, T.; Jappe, W.; Lee, R.C.; Mackay, W.W.; Malitsky, N.; Marr, G.; Michnoff, R.; Oerter, B.; Pozdeyev, E.; Roser, T.; Severino, F.; Smith, K.; Tepikian, S.; Tsoupas, N.

    2009-05-04

    Future Relativistic Heavy Ion Collider (RHIC) runs, including a portion of FY10 heavy ion operations, will explore collisions at center of mass energies of 5-50 GeV/n (GeV/nucleon). Operations at these energies is motivated by a search for the QCD phase transition critical point. The lowest end of this energy range is nearly a factor of four below the nominal RHIC injection center of mass energy of {radical} s = 20.8 GeV/n. There are several operational challenges in the RHIC low-energy regime, including harmonic number changes, small longitudinal acceptance, lowered magnet field quality, nonlinear orbit control, and luminosity monitoring. We report on the experience with some of these challenges during beam tests with gold in March 2008, including first RHIC operations at {radical}s = 9.18 GeV/n and first beam experience at {radical}s = 5 GeV/n.

  2. Spin polarized low-energy positron source

    NASA Astrophysics Data System (ADS)

    Petrov, V. N.; Samarin, S. N.; Sudarshan, K.; Pravica, L.; Guagliardo, P.; Williams, J. F.

    2015-06-01

    This paper presents an investigation of spin polarization of positrons from a source based on the decay of 22Na isotopes. Positrons are moderated by transmission through a tungsten film and electrostatically focussed and transported through a 90 deg deflector to produce a slow positron beam with polarization vector normal to the linear momentum. The polarization of the beam was determined to be about 10% by comparison with polarized electron scattering asymmetries from a thin Fe film on W(110) at 10-10 Torr. Low energy electron emission from Fe layer on W(100) surfaces under positron impact is explored. It is shown that the intensity asymmetry of the electron emission as a function of the incident positron energy can be used to estimate the polarization of the positron beam. Also several materials with long mean free paths for spin relaxation are considered as possible moderators with increased polarization of the emergent positrons.

  3. Low energy demonstration accelerator technical area 53

    SciTech Connect

    1996-04-01

    As part of the Department of Energy`s (DOE) need to maintain the capability of producing tritium in support of its historic and near-term stewardship of the nation`s nuclear weapons stockpile, the agency has recently completed a Programmatic Environmental Impact Statement for Tritium Supply and Recycling. The resulting Record of Decision (ROD) determined that over the next three years the DOE would follow a dual-track acquisition strategy that assures tritium production for the nuclear weapon stockpile in a rapid, cost effective, and safe manner. Under this strategy the DOE will further investigate and compare two options for producing tritium: (1) purchase of an existing commercial light-water reactor or irradiation services with an option to purchase the reactor for conversion to a defense facility; and (2) design, build, and test critical components of a system for accelerator production of tritium (APT). The final decision to select the primary production option will be made by the Secretary of Energy in the October 1998 time frame. The alternative not chosen as the primary production method, if feasible, would be developed as a back-up tritium supply source. This Environmental Assessment (EA) analyzes the potential environmental effects that would be expected to occur if the DOE were to design, build, and test critical prototypical components of the accelerator system for tritium production, specifically the front-end low-energy section of the accelerator, at Los Alamos National Laboratory. The Low Energy Demonstration Accelerator (LEDA) would be incrementally developed and tested in five separate stages over the next seven years. The following issues were evaluated for the proposed action: utility demands, air, human health, environmental restoration, waste management, transportation, water, threatened and endangered species, wetlands, cultural resources, and environmental justice.

  4. Low energy AMS of americium and curium

    NASA Astrophysics Data System (ADS)

    Christl, Marcus; Dai, Xiongxin; Lachner, Johannes; Kramer-Tremblay, Sheila; Synal, Hans-Arno

    2014-07-01

    Accelerator mass spectrometry (AMS) has evolved over the past years as one of the most sensitive, selective, and robust techniques for actinide analyses. While analyses of U and Pu isotopes have already become routine at the ETH Zurich 0.5 MV AMS system "Tandy", there is an increasing demand for highly sensitive analyses of the higher actinides such as Am and Cm for bioassay applications and beyond. In order to extend the actinide capabilities of the compact ETH Zurich AMS system and to develop new, more sensitive bioassay routines, a pilot study was carried out. The aim was to investigate and document the performance and the potential background of Am and Cm analyses with low energy AMS. Our results show that 241Am and Cm isotopes can be determined relative to a 243Am tracer if samples and AMS standards are prepared identically with regard to the matrix elements, in which the sample is dispersed. In this first test, detection limits for Cm and Am isotopes are all in the sub-femtogram range and even below 100 ag for Cm isotopes. In a systematic background study in the mass range of the Cm isotopes, two formerly unknown metastable triply charged Th molecules were found on amu(244) and amu(248). The presence of such a background is not a principal problem for AMS if the stripper pressure is increased accordingly. Based on our first results, we conclude that ultra-trace analyses of Am and Cm isotopes for bioassay are very well possible with low energy AMS.

  5. The Low Energy Effective Area of the Chandra Low Energy Transmission Grating Spectrograph

    NASA Technical Reports Server (NTRS)

    Pease, D.; Drake, J. J.; Johnson, C. O.; Kashya, V.; Ratzlaff, P. W.; Wargelin, B. J.; Brinkman, A. C.; Kaastra, J. S.; vanderMeer, R.; Paerels, F. B.

    2000-01-01

    The Chandra X-ray Observatory was successfully launched on July 23, 1999, and subsequently began an intensive calibration phase. We present the preliminary results from the in-flight calibration of the low energy response of the High Resolution Camera spectroscopic readout (HRC-S) combined with the Low Energy Transmission Grating (LETG) aboard Chandra. These instruments comprise the Low Energy Transmission Grating Spectrograph (LETGS). For this calibration study, we employ a pure hydrogen non-LTE white dwarf emission model (T = 25000 K and log g = 9.0) for comparison with the Chandra observations of Sirius B. The pre-flight calibration of the LETGS effective area only covered wavelengths shortward of 44 A (E less than 277 eV). Our Sirius B analysis shows that the HRC-S quantum efficiency (QE) model assumed for longer wavelengths leads to an overestimate of the effective area by an average factor of about 1.6. We derive a correction to the low energy HRC-S QE model to match the predicted and observed Sirius B spectra over the wavelength range of 44-185 A. We make an independent test of our results by the comparison of a Chandra LETGS observation of HZ 43 with pure hydrogen model atmosphere predictions and find good agreement.

  6. Low energy ion distribution around the Moon

    NASA Astrophysics Data System (ADS)

    Saito, Y.; Yokota, S.; Tanaka, T.; Asamura, K.; Nishino, M. N.; Yamamoto, T.; Tsunakawa, H.

    2009-04-01

    More than a year has passed since MAP-PACE onboard KAGUYA (SELENE) started continuous observation of the low energy charged particles around the Moon from 100km-altitude polar orbit. MAP (MAgnetic field and Plasma experiment) was developed for the comprehensive measurement of the magnetic field and three-dimensional plasma around the Moon. MAP consists of MAP-LMAG (Lunar MAGnetometer) and MAP-PACE (Plasma energy Angle and Composition Experiment). MAP-PACE consists of 4 sensors: ESA (Electron Spectrum Analyzer)-S1, ESA-S2, IMA (Ion Mass Analyzer), and IEA (Ion Energy Analyzer). Since each sensor has hemispherical field of view, two electron sensors and two ion sensors that are installed on the spacecraft panels opposite to each other can make full 3-dimensional measurements of low energy electrons and ions. One of the ion sensors IMA is an energy mass spectrometer. IMA measures mass identified ion energy spectra that have never been obtained at 100km altitude around the Moon. Low energy charged particles around the Moon were vigorously observed by Moon orbiting satellites and plasma instrumentation placed on the lunar surface in 1960s and 1970s. Though there were some satellites that explored the Moon afterwards, most of them were dedicated to the global mapping of the lunar surface. There has been almost no new information about the low energy charged particles around the Moon except the low energy electron measurement by Lunar Prospector, the lunar wake plasma data obtained by WIND during its Moon fly-by, and reports on remote detection of the lunar ions, lunar electrons and ULF waves generated by electron beams around the lunar wake. The newly observed data show characteristic ion distributions around the Moon. Besides the solar wind, MAP-PACE-IMA discovered four clearly distinguishable ion distributions: 1) Solar wind ions reflected/scattered at the lunar surface, 2) Solar wind ions reflected by magnetic anomalies on the lunar surface, 3) Ions that are

  7. 21 CFR 878.4410 - Low energy ultrasound wound cleaner.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Low energy ultrasound wound cleaner. 878.4410... (CONTINUED) MEDICAL DEVICES GENERAL AND PLASTIC SURGERY DEVICES Surgical Devices § 878.4410 Low energy ultrasound wound cleaner. (a) Identification. A low energy ultrasound wound cleaner is a device that...

  8. 21 CFR 878.4410 - Low energy ultrasound wound cleaner.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Low energy ultrasound wound cleaner. 878.4410... (CONTINUED) MEDICAL DEVICES GENERAL AND PLASTIC SURGERY DEVICES Surgical Devices § 878.4410 Low energy ultrasound wound cleaner. (a) Identification. A low energy ultrasound wound cleaner is a device that...

  9. Low energy excitations of the neutron star core

    NASA Astrophysics Data System (ADS)

    Reddy, Sanjay

    2017-01-01

    I will summarize recent work on low energy excitations in cold dense matter and its implications for thermal and transport properties, and seismology of neutron stars. I argue that a low energy Lagrangian with a handful of low energy constants (LECs) provides an adequate framework for calculations. The LECs can be related to the equation of state of dense matter at zero temperature.

  10. 21 CFR 878.4410 - Low energy ultrasound wound cleaner.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Low energy ultrasound wound cleaner. 878.4410... (CONTINUED) MEDICAL DEVICES GENERAL AND PLASTIC SURGERY DEVICES Surgical Devices § 878.4410 Low energy ultrasound wound cleaner. (a) Identification. A low energy ultrasound wound cleaner is a device that...

  11. 21 CFR 878.4410 - Low energy ultrasound wound cleaner.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Low energy ultrasound wound cleaner. 878.4410... (CONTINUED) MEDICAL DEVICES GENERAL AND PLASTIC SURGERY DEVICES Surgical Devices § 878.4410 Low energy ultrasound wound cleaner. (a) Identification. A low energy ultrasound wound cleaner is a device that...

  12. 21 CFR 878.4410 - Low energy ultrasound wound cleaner.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Low energy ultrasound wound cleaner. 878.4410... (CONTINUED) MEDICAL DEVICES GENERAL AND PLASTIC SURGERY DEVICES Surgical Devices § 878.4410 Low energy ultrasound wound cleaner. (a) Identification. A low energy ultrasound wound cleaner is a device that...

  13. Effect of nitrogen ion implantation on corrosion inhibition of nickel coated 316 stainless steel and correlation with nano-structure

    NASA Astrophysics Data System (ADS)

    Grayeli-Korpi, Ali-Reza; Savaloni, Hadi

    2012-10-01

    The influence of implantation of N+ with 20 keV energy and different fluences in the range of 1 × 1017 and 5 × 1018 ions/cm2 in the nickel coated type 316 stainless steel (SS) on the corrosion inhibition of SS in 3.5 wt% NaCl solution is investigated. The highest available N+ fluence showed highest corrosion inhibition. X-ray diffraction (XRD) analysis showed formation of nickel nitride phases that enhanced by increasing the N+ fluence. Surface morphology was studied by atomic force microscope (AFM) and scanning electron microscope (SEM) before and after corrosion test, respectively. AFM results showed that by increasing N+ fluence surface of the sample becomes smoother that may be the result of heat accumulation during implantation causing higher rate of diffusion in the sample.

  14. Effects of recombinant bovine somatotropin implants on serum concentrations of somatotropin, insulin-like growth factor-I and blood urea nitrogen in steers.

    PubMed

    Roeder, R A; Garber, M J; Dalke, B S; Kasser, T R; Veenhuizen, J; Schelling, G T

    1994-09-01

    Four cross-bred beef steers averaging 346 kg were used in a 4 x 4 Latin square design to determine the effect of prolonged-release recombinant bovine somatotropin (rbGH) implants on serum concentrations of somatotropin (GH), insulin-like growth factor-I (IGF-I) and blood urea nitrogen (BUN). Recombinant bGH implants of 0, 40, 80 or 160 mg were administered subcutaneously in the tailhead during the 4 trial periods. Each steer received each treatment starting at 06:00 on day 0 with 21 days between treatments. Jugular vein blood samples were collected on days 0, 1, 2 and 3 (4 day time course for GH, IGF-I and BUN) and every 15 min (GH profile) for 6 h on day 3. Serum baseline GH values were higher (P < 0.10) for the 80 and 160 mg treatments than for the control, and peak amplitude was decreased (P < 0.05) by the 40 and 160 mg treatments. There was a trend (P < 0.11) for fewer GH peaks during the 160 mg treatment. Somatotropin concentrations decreased from day 1 to day 3 (P < 0.05) in a linear manner. Serum IGF-I concentrations increased (P < 0.05) in a linear dose-dependent manner from the 0 mg to the 160 mg treatment. BUN concentrations were not significantly altered by rbGH treatment. Results from this experiment indicate that rbGH implants significantly increase serum IGF-I and GH baseline concentrations while suppressing GH peak amplitude in finishing steers.

  15. RHIC low-energy challenges and plans

    SciTech Connect

    Satogata,T.; Ahrens, L.; Bai, M.; Brennan, J.M.; Bruno, D.; Butler, J.; Drees, A.; Fedotov, A.; Fischer, W.; Harvey, M.; Hayes, T.; Jappe, W.; Lee, R.C.; MacKay, W.W.; Malitsky, N.; Marr, G.; Michnoff, R.; Oerter, B.; Pozdeyev, E.; Roser, T.; Schoefer, V.; Severino, F.; Smith, K.; Tepikian, S.; Tsoupas, N.

    2009-06-08

    Future Relativistic Heavy Ion Collider (RHIC) runs, including a portion of FY10 heavy ion operations, will explore collisions at center of mass energies of 5-50 GeV/n (GeV/nucleon). Operations at these energies is motivated by the search for a possible QCD phase transition critical point. The lowest end of this energy range is nearly a factor of four below the nominal RHIC injection center of mass energy {radical}s = 19.6 GeV/n. There are several operational challenges in the RHIC low-energy regime, including harmonic number changes, small longitudinal acceptance, lowered magnet field quality, nonlinear orbit control, and luminosity monitoring. We report on the experience with these challenges during beam tests with gold beams in March 2008. This includes first operations at {radical}s = 9.18 GeV/n, first beam experience at {radical}s = 5 GeV/n, and luminosity projections for near-term operations.

  16. Low Energy Electron Impact Excitation of Water

    NASA Astrophysics Data System (ADS)

    Ralphs, Kevin; Serna, Gabriela; Hargreaves, Leigh R.; Khakoo, Murtadha A.; Winstead, Carl; McKoy, B. Vincent

    2011-10-01

    We present normalized absolute differential and integral cross-section measurements for the low energy electron impact excitation of the lowest dissociative 3B1, 1B1,3A1 and 1A1 states of H2O. The DCS were taken at incident energies of 9 eV, 10 eV, 12 eV, 15 eV and 20 eV and scattering angles of 15° to 130° and normalized to the elastic electron scattering measurements of. The DCS were obtained after a sophisticated unfolding of the electron energy loss spectrum of water using photoabsorption data in the literature as investigated by Thorn et al.. Our measurements extend those of to near-threshold energies. We find both important agreements and differences between our DCS and those of. Comparison to our theory (multi-channel Schwinger) and that of earlier work will also be presented. Funded by an NSF grant # RUI-PHY 0968874.

  17. Low energy CMOS for space applications

    NASA Technical Reports Server (NTRS)

    Panwar, Ramesh; Alkalaj, Leon

    1992-01-01

    The current focus of NASA's space flight programs reflects a new thrust towards smaller, less costly, and more frequent space missions, when compared to missions such as Galileo, Magellan, or Cassini. Recently, the concept of a microspacecraft was proposed. In this concept, a small, compact spacecraft that weighs tens of kilograms performs focused scientific objectives such as imaging. Similarly, a Mars Lander micro-rover project is under study that will allow miniature robots weighing less than seven kilograms to explore the Martian surface. To bring the microspacecraft and microrover ideas to fruition, one will have to leverage compact 3D multi-chip module-based multiprocessors (MCM) technologies. Low energy CMOS will become increasingly important because of the thermodynamic considerations in cooling compact 3D MCM implementations and also from considerations of the power budget for space applications. In this paper, we show how the operating voltage is related to the threshold voltage of the CMOS transistors for accomplishing a task in VLSI with minimal energy. We also derive expressions for the noise margins at the optimal operating point. We then look at a low voltage CMOS (LVCMOS) technology developed at Stanford University which improves the power consumption over conventional CMOS by a couple of orders of magnitude and consider the suitability of the technology for space applications by characterizing its SEU immunity.

  18. Low energy neutral atom imaging techniques

    SciTech Connect

    Funsten, H.O. McComas, D.J.; Scime, E.E.

    1993-01-01

    The potential scientific return from low energy neutral atom (LENA) imaging of the magnetosphere is extraordinary. The technical challenges of LENA detection include (1) removal of LENAs from the tremendous ambient UV without losing information of their incident trajectories, (2) quantification of their trajectories, and (3) obtaining high sensitivity measurements. Two techniques that have been proposed for this purpose are based on fundamentally different atomic interaction mechanisms between LENAs and a solid: LENA transmission through an ultrathin foil and LENA reflection from a solid surface. Both of these methods provide LENA ionization (for subsequent removal from the UV by electrostatic deflection) and secondary electron emission (for start pulse generation for time-of-flight and/or coincidence). We present a comparative study of the transmission and reflection techniques based on differences in atomic interactions with solids and surfaces. We show that transmission methods yield an order of magnitude greater secondary electron emission than reflection methods. Transmission methods are shown to be sufficient for LENA energies of approximately 1 keV to greater than 30 keV. Reflection methods using low work function surfaces could be employed for LENA ionization for energies less than several keV.

  19. Optimal Low Energy Earth-Moon Transfers

    NASA Technical Reports Server (NTRS)

    Griesemer, Paul Ricord; Ocampo, Cesar; Cooley, D. S.

    2010-01-01

    The optimality of a low-energy Earth-Moon transfer is examined for the first time using primer vector theory. An optimal control problem is formed with the following free variables: the location, time, and magnitude of the transfer insertion burn, and the transfer time. A constraint is placed on the initial state of the spacecraft to bind it to a given initial orbit around a first body, and on the final state of the spacecraft to limit its Keplerian energy with respect to a second body. Optimal transfers in the system are shown to meet certain conditions placed on the primer vector and its time derivative. A two point boundary value problem containing these necessary conditions is created for use in targeting optimal transfers. The two point boundary value problem is then applied to the ballistic lunar capture problem, and an optimal trajectory is shown. Additionally, the ballistic lunar capture trajectory is examined to determine whether one or more additional impulses may improve on the cost of the transfer.

  20. Oscillations of very low energy atmospheric neutrinos

    SciTech Connect

    Peres, Orlando L. G.; Smirnov, A. Yu.

    2009-06-01

    There are several new features in the production, oscillations, and detection of the atmospheric neutrinos of low energies E < or approx. 100 MeV. The flavor ratio r of muon to electron neutrino fluxes is substantially smaller than 2 and decreases with energy, a significant part of events is due to the decay of invisible muons at rest, etc. Oscillations in a two-layer medium (atmosphere-Earth) should be taken into account. We derive analytical and semianalytical expressions for the oscillation probabilities of these 'sub-sub-GeV' neutrinos. The energy spectra of the e-like events in water Cherenkov detectors are computed, and the dependence of the spectra on the 2-3 mixing angle {theta}{sub 23}, the 1-3 mixing, and the CP-violation phase are studied. We find that variations of {theta}{sub 23} in the presently allowed region change the number of e-like events by about 15%-20% as well as lead to distortion of the energy spectrum. The 1-3 mixing and CP violation can lead to {approx}10% effects. Detailed study of the sub-sub-GeV neutrinos will be possible in future megaton-scale detectors.

  1. Low-energy electron scattering from cyanamide

    NASA Astrophysics Data System (ADS)

    Wang, Kedong; Guo, Shuangcheng; Meng, Ju; Huang, Xiaotian; Wang, Yongfeng

    2016-09-01

    The low-energy electron collisions with cyanamide molecule are investigated by using the UK molecular R -matrix codes for electron energies ranging from 0.01 eV to 10 eV. Three models including static-exchange, static-exchange plus polarization, and close-coupling (CC) approximations are employed to reveal the dynamic interaction. Elastic (integrated and differential), momentum-transfer, and excitation cross sections from the ground state to the three low-lying electron excited states have been presented. Two shape resonances, two core-excited resonances, and two Feshbach resonances are detected in the CC approximation. The role of active space in the target and scattering problem including the resonances is discussed. The precise resonance parameters are found to be sensitive to the treatment of polarization effects employed. These resonances may be responsible for the fragments observed in a recent experiment of the dissociative electron attachments to cyanamide. Since the cyanamide molecule has a large permanent dipole moment, a Born closure procedure is used to account for the contribution of partial waves higher than l =4 to obtain converged cross sections.

  2. Low energy stable plasma calibration facility.

    PubMed

    Frederick-Frost, K M; Lynch, K A

    2007-07-01

    We have designed and fabricated a low energy plasma calibration facility for testing and calibration of rocket-borne charged-particle detectors and for the investigation of plasma sheath formation in an environment with ionospheric plasma energies, densities, and Debye lengths. We describe the vacuum system and associated plasma source, which was modified from a Naval Research Laboratory design [Bowles et al. Rev. Sci. Instrum. 67, 455 (1996)]. Mechanical and electrical modifications to this cylindrical microwave resonant source are outlined together with a different method of operating the magnetron that achieves a stable discharge. This facility produces unmagnetized plasmas with densities from 1x10(3)/cm(3) to 6x10(5)/cm(3), electron temperatures from 0.1 to 1.7 eV, and plasma potentials from 0.5 to 8 V depending on varying input microwave power and neutral gas flow. For the range of input microwave power explored (350-600 W), the energy density of the plasma remains constant because of an inverse relationship between density and temperature. This relationship allows a wide range of Debye lengths (0.3-8.4 cm) to be investigated, which is ideal for simulating the ionospheric plasma sheaths we explore.

  3. Low Energy Electron Scattering from Fuels

    NASA Astrophysics Data System (ADS)

    Lopes, M. Cristina A.

    2012-06-01

    We report an investigation of processes that occur during the ignition of the plasma and its consequences in post-discharge time for an internal combustion engine, in order to find the appropriate parameters to be used in cars that operate with lean mixtures air-fuel. The relevance of this theme has attracted much attention, and has been one of the subjects of collaboration between experimental and theoretical groups in the USA and Brazil. We have produced some basic information necessary to modeling spark ignition in alcohol- fuelled engines. Total cross sections of electron scattering by methanol and ethanol molecules were obtained, using the linear transmission method based on the Beer-Lambert law to first approximation. Measurements and calculations of differential cross sections for low-energy (rotationally unresolved) electron scattering were also obtained, for scattering angles of 5 --130 . The measurements were taken using the relative flow method with an aperture source, and calculations using two different implementations of the Schwinger multichannel method, one that takes all electrons into account and is adapted for parallel computers, and another that uses pseudopotentials and considers only the valence electrons. Additionally to these, computer simulation studies of electronic discharge in mixtures of ethanol were performed, using a Zero-Dimensional Plasma Kinetic solver. Previous reported models for combustion of ethanol and cross sections data for momentum transfer of electron collisions with ethanol were used. The time evolutions of the main species densities are reported and the ignition time delay discussed.

  4. Low Energy Electron Scattering from Fuels

    NASA Astrophysics Data System (ADS)

    Lopes, M. C. A.; Silva, D. G. M.; Bettega, M. H. F.; da Costa, R. F.; Lima, M. A. P.; Khakoo, M. A.; Winstead, C.; McKoy, V.

    2012-11-01

    In order to understand and optimize processes occurring during the ignition of plasma and its consequences in post-discharge for an internal combustion engine, especially considering the spark plug, we have produced in this work some basic information necessary to modeling spark ignition in alcohol- fuelled engines. Total cross sections of electron scattering by methanol and ethanol molecules in the energy range from 60 to 500 eV are reported, using the linear transmission method based on the Beer-Lambert law to first approximation. Aditionally to that, measurements and calculations of differential cross sections for elastic low-energy (rotationally unresolved) electron scattering were also discussed, for impact energies of 1, 2, 5, 10, 15, 20, 30, 50, and 100 eV and for scattering angles of 5°-130°. The measurements were obtained using the relative flow method with an aperture source, and calculations using two different implementations of the Schwinger multichannel method, one that takes all electrons into account and is adapted for parallel computers, and another that uses pseudopotentials and considers only the valence electrons.

  5. Low-energy muon [LEM] study of Zn-phthalocyanine and ZnO thin films

    NASA Astrophysics Data System (ADS)

    Alberto, H. V.; Piroto Duarte, J.; Weidinger, A.; Vilão, R. C.; Gil, J. M.; Ayres de Campos, N.; Fostiropoulos, K.; Prokscha, T.; Suter, A.; Morenzoni, E.

    2009-04-01

    Implantation of low-energy muons in zinc-phthalocyanine (ZnPc) thin-films leads to the formation of muoniated radical states, the fast decaying of the μSR signal at low fields being a clear indication of muonium formation. The formation probability of these paramagnetic states is independent of the implantation depth and amounts, as in the bulk, to approximately 100% of all muons. In these molecular crystals the formation of muonium is a highly local effect and is fairly independent of crystalline structure and defects in the sample. In contrast to that, in vapour-grown ZnO films the paramagnetic signal known from bulk experiments is not observed, even for the deeper implantations. We suggest that in this case muonium is not formed due to the low concentration of free electrons. In these strongly distorted films, electrons are captured at defects and are not available for muonium formation.

  6. Low energy beam transport system developments

    SciTech Connect

    Dudnikov, V.; Han, B.; Stockli, M.; Welton, R.; Dudnikova, G.

    2015-04-08

    For high brightness beam production it is important to preserve the brightness in the low energy beam transport system (LEBT) used to transport and match the ion beams to the next stage of acceleration, usually an RFQ. While electrostatic focusing can be problematic for high current beam transport, reliable electrostatic LEBT operation has been demonstrated with H{sup −} beams up to 60 mA. Now, however, it is commonly accepted that an optimal LEBT for high current accelerator applications consists of focusing solenoids with space charge compensation. Two-solenoid LEBTs are successfully used for high current (>100 mA) proton beam transport. Preservation of low emittances (~0.15 π mm-mrad) requires the addition of a heavy gas (Xe, Kr), which causes ~5% of proton loss in a 1 m long LEBT. Similar Xe densities would be required to preserve low emittances of H{sup −} beams, but such gas densities cause unacceptably high H{sup −} beam losses. A short LEBT with only one short solenoid, movable for RFQ matching, can be used for reduced negative ion stripping. A strong electrostatic-focusing LEBT has been successfully adopted for transport of high current H{sup −} beams in the SNS Front End. Some modifications of such electrostatic LEBTs are expected to improve the reliable transport of intense positive and negative ion beams without greatly degrading their low emittances. We concentrate on processes that determine the beam brightness degradation and on their prevention. Proposed improvements to the SNS electrostatic LEBT are discussed.

  7. Low-energy electron collisions with thiophene.

    PubMed

    da Costa, R F; Varella, M T do N; Lima, M A P; Bettega, M H F

    2013-05-21

    We report on elastic integral, momentum transfer, and differential cross sections for collisions of low-energy electrons with thiophene molecules. The scattering calculations presented here used the Schwinger multichannel method and were carried out in the static-exchange and static-exchange plus polarization approximations for energies ranging from 0.5 eV to 6 eV. We found shape resonances related to the formation of two long-lived π∗ anion states. These resonant structures are centered at the energies of 1.00 eV (2.85 eV) and 2.82 eV (5.00 eV) in the static-exchange plus polarization (static-exchange) approximation and belong to the B1 and A2 symmetries of the C2v point group, respectively. Our results also suggest the existence of a σ∗ shape resonance in the B2 symmetry with a strong d-wave character, located at around 2.78 eV (5.50 eV) as obtained in the static-exchange plus polarization (static-exchange) calculation. It is worth to mention that the results obtained at the static-exchange plus polarization level of approximation for the two π∗ resonances are in good agreement with the electron transmission spectroscopy results of 1.15 eV and 2.63 eV measured by Modelli and Burrow [J. Phys. Chem. A 108, 5721 (2004)]. The existence of the σ∗ shape resonance is in agreement with the observations of Dezarnaud-Dandiney et al. [J. Phys. B 31, L497 (1998)] based on the electron transmission spectra of dimethyl(poly)sulphides. A comparison among the resonances of thiophene with those of pyrrole and furan is also performed and, altogether, the resonance spectra obtained for these molecules point out that electron attachment to π∗ molecular orbitals is a general feature displayed by these five-membered heterocyclic compounds.

  8. Low-energy electron collisions with thiophene

    NASA Astrophysics Data System (ADS)

    da Costa, R. F.; Varella, M. T. do N.; Lima, M. A. P.; Bettega, M. H. F.

    2013-05-01

    We report on elastic integral, momentum transfer, and differential cross sections for collisions of low-energy electrons with thiophene molecules. The scattering calculations presented here used the Schwinger multichannel method and were carried out in the static-exchange and static-exchange plus polarization approximations for energies ranging from 0.5 eV to 6 eV. We found shape resonances related to the formation of two long-lived π* anion states. These resonant structures are centered at the energies of 1.00 eV (2.85 eV) and 2.82 eV (5.00 eV) in the static-exchange plus polarization (static-exchange) approximation and belong to the B1 and A2 symmetries of the C2v point group, respectively. Our results also suggest the existence of a σ* shape resonance in the B2 symmetry with a strong d-wave character, located at around 2.78 eV (5.50 eV) as obtained in the static-exchange plus polarization (static-exchange) calculation. It is worth to mention that the results obtained at the static-exchange plus polarization level of approximation for the two π* resonances are in good agreement with the electron transmission spectroscopy results of 1.15 eV and 2.63 eV measured by Modelli and Burrow [J. Phys. Chem. A 108, 5721 (2004), 10.1021/jp048759a]. The existence of the σ* shape resonance is in agreement with the observations of Dezarnaud-Dandiney et al. [J. Phys. B 31, L497 (1998), 10.1088/0953-4075/31/11/004] based on the electron transmission spectra of dimethyl(poly)sulphides. A comparison among the resonances of thiophene with those of pyrrole and furan is also performed and, altogether, the resonance spectra obtained for these molecules point out that electron attachment to π* molecular orbitals is a general feature displayed by these five-membered heterocyclic compounds.

  9. Absolute calorimetric calibration of low energy brachytherapy sources

    NASA Astrophysics Data System (ADS)

    Stump, Kurt E.

    In the past decade there has been a dramatic increase in the use of permanent radioactive source implants in the treatment of prostate cancer. A small radioactive source encapsulated in a titanium shell is used in this type of treatment. The radioisotopes used are generally 125I or 103Pd. Both of these isotopes have relatively short half-lives, 59.4 days and 16.99 days, respectively, and have low-energy emissions and a low dose rate. These factors make these sources well suited for this application, but the calibration of these sources poses significant metrological challenges. The current standard calibration technique involves the measurement of ionization in air to determine the source air-kerma strength. While this has proved to be an improvement over previous techniques, the method has been shown to be metrologically impure and may not be the ideal means of calbrating these sources. Calorimetric methods have long been viewed to be the most fundamental means of determining source strength for a radiation source. This is because calorimetry provides a direct measurement of source energy. However, due to the low energy and low power of the sources described above, current calorimetric methods are inadequate. This thesis presents work oriented toward developing novel methods to provide direct and absolute measurements of source power for low-energy low dose rate brachytherapy sources. The method is the first use of an actively temperature-controlled radiation absorber using the electrical substitution method to determine total contained source power of these sources. The instrument described operates at cryogenic temperatures. The method employed provides a direct measurement of source power. The work presented here is focused upon building a metrological foundation upon which to establish power-based calibrations of clinical-strength sources. To that end instrument performance has been assessed for these source strengths. The intent is to establish the limits of

  10. [Cardioversion of atrial fibrillation with low energy internal electric shock].

    PubMed

    Ricard, P; Socas, A G; Taramasco, V; Guenoun, M; Lévy, S

    1997-12-01

    The efficacy and safety of low internal cardioversion for the reduction of atrial fibrillation was assessed prospectively in 104 consecutive patients. Sixty-two patients had chronic atrial fibrillation (Group I). 16 patients had paroxysmal atrial fibrillation (Group II) and 26 patients had induced atrial fibrillation (Group III). The average duration of the current episode of atrial fibrillation was 9 +/- 19 months in Group I, 4 +/- 2 days in Group II and 18 +/- 7 minutes in Group III. Two intracardiac defibrillation catheters were used, one (the cathode) in the right atrium and the other in the coronary sinus or left branch of the pulmonary artery (anode). These catheters were connected to an external defibrillator delivering biphasic 3/3 ms shocks with a voltage which could be programmed from 10 to 400 volts. The shocks were synchronised on the R wave. Sinus rhythm was restored in 44 of the 62 patients in Group I (70%), 12 of the 16 patients in Group II (75%) and 20 of the 26 patients in Group III (77%). The average voltages and energies restoring sinus rhythm were 300 +/- 68 volts and 3.5 +/- 1.5 joules respectively in Group I, 245 +/- 72 volts and 2.0 +/- 2.9 joules in Group II, and 270 +/- 67 volts and 2.6 +/- 1.2 joules in Group III. These results show that the energy required to restore sinus rhythm is significantly greater in patients with chronic atrial fibrillation than in patients with paroxysmal or induced atrial fibrillation. There were no ventricular proarrhythmic effects in the 686 shocks synchronised on the R wave. This study shows that internal cardioversion of atrial fibrillation is feasible with low energies under simple sedation. These results support the concept of an implantable atrial defibrillator.

  11. Development of a Low-energy Trigger for VERITAS

    SciTech Connect

    Kildea, J.

    2008-12-24

    During the 2007/2008 observing season a low-energy trigger configuration was developed and tested for VERITAS. The configuration makes uses of the small ({approx}35 m) baseline between two of the VERITAS telescopes and employs a much lower discriminator threshold and tighter coincidence window compared to the standard VERITAS trigger. Five hours of Crab Nebula ON/OFF observations were obtained in low-energy mode and were used to test new low-energy analysis algorithms. We present some details of the VERITAS low-energy trigger and the associated data analysis.

  12. Low-Energy Ballistic Transfers to Lunar Halo Orbits

    NASA Technical Reports Server (NTRS)

    Parker, Jeffrey S.

    2009-01-01

    Recent lunar missions have begun to take advantage of the benefits of low-energy ballistic transfers between the Earth and the Moon rather than implementing conventional Hohmann-like lunar transfers. Both Artemis and GRAIL plan to implement low-energy lunar transfers in the next few years. This paper explores the characteristics and potential applications of many different families of low-energy ballistic lunar transfers. The transfers presented here begin from a wide variety of different orbits at the Earth and follow several different distinct pathways to the Moon. This paper characterizes these pathways to identify desirable low-energy lunar transfers for future lunar missions.

  13. Electronic structure of nitinol surfaces oxidized by low-energy ion bombardment

    SciTech Connect

    Petravic, M. Varasanec, M.; Peter, R.; Kavre, I.; Metikos-Hukovic, M.; Yang, Y.-W.

    2014-06-28

    We have studied the electronic structure of nitinol exposed to low-energy oxygen-ion bombardment, using x-ray photoemission spectroscopy (XPS) and near-edge x-ray absorption fine structure (NEXAFS) spectroscopy. XPS spectra reveal a gradual transformation of nitinol surfaces into TiO{sub 2} with increased dose of implanted oxygen. No oxidation of Ni atoms has been detected. NEXAFS spectra around O K-edge and Ti L{sub 2,3}-edge, reflecting the element-specific partial density of empty electronic states, exhibit features, which can be attributed to the creation of molecular orbitals, crystal field splitting, and the absence of long-range order, characteristic of the amorphous TiO{sub 2}. Based on these results, we discuss the oxidation kinetics of nitinol under low-energy oxygen-ion bombardment.

  14. Electronic structure of nitinol surfaces oxidized by low-energy ion bombardment

    NASA Astrophysics Data System (ADS)

    Petravic, M.; Varasanec, M.; Peter, R.; Kavre, I.; Metikos-Hukovic, M.; Yang, Y.-W.

    2014-06-01

    We have studied the electronic structure of nitinol exposed to low-energy oxygen-ion bombardment, using x-ray photoemission spectroscopy (XPS) and near-edge x-ray absorption fine structure (NEXAFS) spectroscopy. XPS spectra reveal a gradual transformation of nitinol surfaces into TiO2 with increased dose of implanted oxygen. No oxidation of Ni atoms has been detected. NEXAFS spectra around O K-edge and Ti L2,3-edge, reflecting the element-specific partial density of empty electronic states, exhibit features, which can be attributed to the creation of molecular orbitals, crystal field splitting, and the absence of long-range order, characteristic of the amorphous TiO2. Based on these results, we discuss the oxidation kinetics of nitinol under low-energy oxygen-ion bombardment.

  15. Transferring Gus gene into intact rice cells by low energy ion beam

    NASA Astrophysics Data System (ADS)

    Zengliang, Yu; Jianbo, Yang; Yuejin, Wu; Beijiu, Cheng; Jianjun, He; Yuping, Huo

    1993-06-01

    A new technique of transferring genes by low energy ion beam has been reported in this paper. The Gus and CAT (chloramphenicol acetyltransferase) genes, as "foreign" genetic materials, were introduced into the suspension cells and ripe embryos or rice by implantation of 20-30 keV Ar + at doses ranging from 1 × 10 15 to 4 × 10 15 ions/cm 2. The activities of CAT and Gus were detected in the cells and embryos after several weeks. The results indicate that the transfer was a success.

  16. What is a low-energy house and who cares?

    SciTech Connect

    Litt, B.R.

    1994-12-01

    Most energy analysts view low-energy houses as good things, yet differ in their expectations of what exactly a low energy house is. There are two intertwining threads to this report. The first is an evaluation of 50 buildings that have been claimed to be low-energy residences, for which monitored energy performance data have been collected. These data represent the preliminary effort in the ongoing update of the Buildings Energy-Use Compilation and Analysis (BECA) data base for new residences. The second thread concerns the definition of a low-energy house. After the elements of a definition are presented, their implications for actors involved in providing housing are identified. Several more tractable definitions are applied to the houses in this compilation. The outcomes illustrate ways in which different interests are served by various definitions. Different definitions can yield very different energy rankings. No single definition of a low-energy house is universally applicable.

  17. Low-energy ion beam-based deposition of gallium nitride

    SciTech Connect

    Vasquez, M. R.; Wada, M.

    2016-02-15

    An ion source with a remote plasma chamber excited by a 13.56 MHz radio frequency power was used for low-energy broad ion beam extraction. Optical emission spectral analyses showed the sputtering and postionization of a liquid gallium (Ga) target placed in a chamber separated from the source bombarded by argon (Ar) plasma guided by a bent magnetic field. In addition, an E × B probe successfully showed the extraction of low-energy Ga and Ar ion beams using a dual-electrode extractor configuration. By introducing dilute amounts of nitrogen gas into the system, formation of thin Ga-based films on a silicon substrate was demonstrated as determined from X-ray diffraction and X-ray reflectivity studies.

  18. Low-energy ion beam-based deposition of gallium nitride.

    PubMed

    Vasquez, M R; Wada, M

    2016-02-01

    An ion source with a remote plasma chamber excited by a 13.56 MHz radio frequency power was used for low-energy broad ion beam extraction. Optical emission spectral analyses showed the sputtering and postionization of a liquid gallium (Ga) target placed in a chamber separated from the source bombarded by argon (Ar) plasma guided by a bent magnetic field. In addition, an E × B probe successfully showed the extraction of low-energy Ga and Ar ion beams using a dual-electrode extractor configuration. By introducing dilute amounts of nitrogen gas into the system, formation of thin Ga-based films on a silicon substrate was demonstrated as determined from X-ray diffraction and X-ray reflectivity studies.

  19. Low-energy ion beam-based deposition of gallium nitride

    NASA Astrophysics Data System (ADS)

    Vasquez, M. R.; Wada, M.

    2016-02-01

    An ion source with a remote plasma chamber excited by a 13.56 MHz radio frequency power was used for low-energy broad ion beam extraction. Optical emission spectral analyses showed the sputtering and postionization of a liquid gallium (Ga) target placed in a chamber separated from the source bombarded by argon (Ar) plasma guided by a bent magnetic field. In addition, an E × B probe successfully showed the extraction of low-energy Ga and Ar ion beams using a dual-electrode extractor configuration. By introducing dilute amounts of nitrogen gas into the system, formation of thin Ga-based films on a silicon substrate was demonstrated as determined from X-ray diffraction and X-ray reflectivity studies.

  20. The Low-Energy Background in XENON1T

    NASA Astrophysics Data System (ADS)

    Gao, Fei; Stein, Alec; Xenon1T Collaboration

    2017-01-01

    The XENON1T dark matter direct-detection experiment looks for hypothetical Weakly Interacting Massive Particles (WIMPs). WIMPs are expected to scatter off xenon nuclei at low energies, so understanding the low-energy background of the detector is crucial. In XENON1T, the background in the WIMP search region is due to radioactive decays stemming from the detector construction materials and impurities in the xenon itself. We show that our predicted low-energy background rate of 10-4events .kg-1 .day-1 .keV-1 matches XENON1T's design goals and is in agreement with the data taken during the commissioning of the detector.

  1. Parity violation in low-energy neutron-deuteron scattering

    SciTech Connect

    Song, Young-Ho; Gudkov, Vladimir; Lazauskas, Rimantas

    2011-01-15

    Parity-violating effects for low-energy elastic neutron deuteron scattering are calculated for Desplanques, Donoghue, and Holstein (DDH) and effective field theory types of weak potentials in a distorted-wave Born approximation, using realistic hadronic strong interaction wave functions, obtained by solving three-body Faddeev equations in configuration space. The resulting relation between physical observables and low-energy constants can be used to fix low-energy constants from experiments. Potential model dependencies of parity-violating effects are discussed.

  2. Biological assessments for the low energy demonstration accelerator, 1996

    SciTech Connect

    Cross, S.

    1997-03-01

    This report discusses the biological impact to the area around the Los Alamos National Laboratory of the Low Energy Demonstration Accelerator. In particular the impact to the soils, water quality, vegetation, and wildlife are discussed.

  3. Past, present and future low energy antiproton facilities at CERN

    NASA Astrophysics Data System (ADS)

    Bartmann, W.; Belochitskii, P.; Breuker, H.; Butin, F.; Carli, C.; Eriksson, T.; Maury, S.; Oelert, W.; Pasinelli, S.; Tranquille, G.

    2014-05-01

    Low energy antiprotons are available for physics experiments at CERN since the 1980s and have been used by a large variety of experiments. The Low Energy Antiproton Ring LEAR has been constructed as a complementary use of antiprotons available at that time for high energy physics and delivered beam to experiments mainly using slow extraction. After completion of LEAR exploitation, the Antiproton Decelerator (AD) was constructed (adaptation of the existing Antiproton Collector, AC) to allow for a simpler low energy antiproton scheme (only one accelerator operated with Antiprotons) with fast extraction well suited for trap experiments. The Extra Low ENergy Antiproton ring ELENA is a small synchrotron presently constructed to further decelerate antiprotons from the AD in a controlled manner, and to reduce emittances with the help of an electron cooler to improve the capture efficiencies of existing experiments and allow for additional ones.

  4. Radial Flux Distribution of Low-Energy Neutrons.

    ERIC Educational Resources Information Center

    Higinbotham, J.

    1979-01-01

    Describes an experiment designed to illustrate the basic principle involved in the process of moderation of fast neutrons by water, and the monitoring of the low-energy neutron flux using indium as a probe. (GA)

  5. Beam lifetime and limitations during low-energy RHIC operation

    SciTech Connect

    Fedotov, A.V.; Bai, M.; Blaskiewicz, M.; Fischer, W.; Kayran, D.; Montag, C.; Satogata, T.; Tepikian, S.; Wang, G.

    2011-03-28

    The low-energy physics program at the Relativistic Heavy Ion Collider (RHIC), motivated by a search for the QCD phase transition critical point, requires operation at low energies. At these energies, large nonlinear magnetic field errors and large beam sizes produce low beam lifetimes. A variety of beam dynamics effects such as Intrabeam Scattering (IBS), space charge and beam-beam forces also contribute. All these effects are important to understand beam lifetime limitations in RHIC at low energies. During the low-energy RHIC physics run in May-June 2010 at beam {gamma} = 6.1 and {gamma} = 4.1, gold beam lifetimes were measured for various values of space-charge tune shifts, transverse acceptance limitation by collimators, synchrotron tunes and RF voltage. This paper summarizes our observations and initial findings.

  6. Strong flux of low-energy neutrons produced by thunderstorms.

    PubMed

    Gurevich, A V; Antonova, V P; Chubenko, A P; Karashtin, A N; Mitko, G G; Ptitsyn, M O; Ryabov, V A; Shepetov, A L; Shlyugaev, Yu V; Vildanova, L I; Zybin, K P

    2012-03-23

    We report here for the first time about the registration of an extraordinary high flux of low-energy neutrons generated during thunderstorms. The measured neutron count rate enhancements are directly connected with thunderstorm discharges. The low-energy neutron flux value obtained in our work is a challenge for the photonuclear channel of neutron generation in thunderstorm: the estimated value of the needed high-energy γ-ray flux is about 3 orders of magnitude higher than that one observed.

  7. The Trapping of Low-Energy Particles by Interplanetary Shocks

    NASA Astrophysics Data System (ADS)

    Al Dayeh, M.; Dwyer, J.; Rassoul, H.; Mason, G.; Mazur, J.; Desai, M.

    2007-12-01

    Using ~0.045-10 MeV/nucleon ion data from ACE/ULEIS, we have found that a substantial number of shock- associated solar energetic particle events (20 events) have significant delays in the arrival of the low-energy component beyond what is expected from the travel time of energetic particles from the sun to the earth at 1 AU. Indeed, for some events, after correcting for the velocity dispersion, the low energy component (E < 0.1 MeV/nucleon) is almost completely absent while the high-energy component (E > 1 MeV/nucleon) has very large enhancements. SEP events with the most dramatic initial depletion of low-energy particles are accompanied by large proton fluxes and have large enhancements of the low-energy particles later, in coincidence with the arrival of the interplanetary shock, a day or two after the start of the event. In addition, these events show Fe/O enhancements during the periods in which the low-energy component is depleted and lower Fe/O values once the shock arrives. These new observations appear to be explained by the trapping of particles with low energy-to-charge (E/Q) ratios in the vicinity of the shock by magnetohydrodynamic waves, possibly generated by high energy protons streaming along the magnetic field lines.

  8. On the origin of apparent Z1-oscillations in low-energy heavy-ion ranges

    NASA Astrophysics Data System (ADS)

    Wittmaack, Klaus

    2016-12-01

    It has been known for quite some time that projected ranges measured by Rutherford backscattering spectrometry for a variety of low-energy heavy ions (energy-to-mass ratio E/M1 less than ∼0.4 keV/u) exhibit significant or even pronounced deviations from the theoretically predicted smooth dependence on the projectile's atomic number Z1. Studied most thoroughly for silicon targets, the effect was attributed to 'Z1 oscillations' in nuclear stopping, in false analogy to the well established Z1 oscillations in electronic stopping of low-velocity light ions. In this study an attempt was made to get order into range data published by four different groups. To achieve the goal, the absolute values of the ranges from each group had to be (re-)adjusted by up to about ±10%. Adequate justification for this approach is provided. With the changes made, similarities and differences between the different sets of data became much more transparent than before. Very important is the finding that the distortions in heavy-ion ranges are not oscillatory in nature but mostly one-sided, reflecting element-specific transport of implanted atoms deeper into the solid. Exceptions are rare gas and alkali elements, known to exhibit bombardment induced transport towards the surface. Range distortions reported for Xe and Cs could be reproduced on the basis of the recently established rapid relocation model. The extent of transport into the bulk, observed with many other elements, notably noble metals and lanthanides, reflects their high mobility under ion bombardment. The complexity of the element specific transport phenomena became fully evident by also examining the limited number of data available for the apparent range straggling. Profile broadening was identified in several cases. One element (Eu) was found to exhibit profile narrowing. This observation suggests that implanted atoms may agglomerate at peak concentrations up to 2%, possibly a tool for generating nano-structured dopant

  9. Comparability and accuracy of nitrogen depth profiling in nitrided austenitic stainless steel

    NASA Astrophysics Data System (ADS)

    Manova, D.; Díaz, C.; Pichon, L.; Abrasonis, G.; Mändl, S.

    2015-04-01

    A comparative study of nitrogen depth profiles in low energy ion implantation nitrided austenitic stainless steel 1.4301 by glow discharge optical emission spectroscopy (GDOES), secondary ion mass spectrometry (SIMS) and nuclear reaction analysis (NRA) is presented. All methods require calibration either from reference samples or known scattering or reaction cross sections for the nitrogen concentration, while the methods producing a sputter crater - SIMS and GDOES - need additional conversion from sputter time to depth. NRA requires an assumption of material density for a correct conversion from the 'natural' units inherent to all ion beam analysis methods into 'conventional' depth units. It is shown that a reasonable agreement of the absolute concentrations and very good agreement of the layer thickness is obtained. The observed differences in broadening between the nitrogen distribution near the surface and the deeper region of the nitrided layer-steel interface are discussed on the basis of surface contaminations, surface roughening and energy straggling effects.

  10. A comparative study on low-energy ion beam and neutralized beam modifications of naked DNA and biological effect on mutation

    NASA Astrophysics Data System (ADS)

    Sarapirom, S.; Thongkumkoon, P.; Prakrajang, K.; Anuntalabhochai, S.; Yu, L. D.

    2012-02-01

    DNA conformation change or damage induced by low-energy ion irradiation has been of great interest owing to research developments in ion beam biotechnology and ion beam application in biomedicine. Mechanisms involved in the induction of DNA damage may account for effect from implanting ion charge. In order to check this effect, we used both ion beam and neutralized beam at keV energy to bombard naked DNA. Argon or nitrogen ion beam was generated and extracted from a radiofrequency (RF) ion source and neutralized by microwave-driven plasma in the beam path. Plasmid DNA pGFP samples were irradiated with the ion or neutralized beam in vacuum, followed by gel electrophoresis to observe changes in the DNA conformations. It was revealed that the ion charge played a certain role in inducing DNA conformation change. The subsequent DNA transfer into bacteria Escherichia coli ( E. coli) for mutation analysis indicated that the charged ion beam induced DNA change had high potential in mutation induction while neutralized beam did not. The intrinsic reason was attributed to additional DNA deformation and contortion caused by ion charge exchange effect so that the ion beam induced DNA damage could hardly be completely repaired, whereas the neutralized beam induced DNA change could be more easily recoverable owing to absence of the additional DNA deformation and contortion.

  11. First-principles study on the interaction of nitrogen atom with α–uranium: From surface adsorption to bulk diffusion

    SciTech Connect

    Su, Qiulei; Deng, Huiqiu E-mail: hqdeng@gmail.com; Xiao, Shifang; Li, Xiaofan; Hu, Wangyu; Ao, Bingyun; Chen, Piheng

    2014-04-28

    Experimental studies of nitriding on uranium surfaces show that the modified layers provide considerable protection against air corrosion. The bimodal distribution of nitrogen is affected by both its implantation and diffusion, and the diffusion of nitrogen during implantation is also governed by vacancy trapping. In the present paper, nitrogen adsorption, absorption, diffusion, and vacancy trapping on the surface of and in the bulk of α–uranium are studied with a first-principles density functional theory approach and the climbing image nudged elastic band method. The calculated results indicate that, regardless of the nitrogen coverage, a nitrogen atom prefers to reside at the hollow1 site and octahedral (Oct) site on and below the surface, respectively. The lowest energy barriers for on-surface and penetration diffusion occur at a coverage of 1/2 monolayer. A nitrogen atom prefers to occupy the Oct site in bulk α–uranium. High energy barriers are observed during the diffusion between neighboring Oct sites. A vacancy can capture its nearby interstitial nitrogen atom with a low energy barrier, providing a significant attractive nitrogen-vacancy interaction at the trapping center site. This study provides a reference for understanding the nitriding process on uranium surfaces.

  12. Effects of Ion Implantation on in Vitro Pollen Germination and Cellular Organization of Pollen Tube in Pinus thunbergii Parl. (Japanese Black Pine)

    NASA Astrophysics Data System (ADS)

    Li, Guoping; Huang, Qunce; Yang, Lusheng; Dai, Ximei; Qin, Guangyong; Huo, Yuping

    2006-09-01

    Low-energy ion implantation, as a new technology to produce mutation in plant breeding, has been widely applied in agriculture in China. But so far there is a little understanding of the underlying mechanisms responsible for its biological effects at the cellular level. Here we report the biological effects of a nitrogen ion beams of 30 keV on the pollen grains of Pinus thunbergii Parl. In general, ion implantation inhibited pollen germination. The dose-response curve presented a particular saddle-like pattern. Ion implantation also changed the dimension of the elongated tubes and significantly induced tip swelling. Confocal microscopy indicated that the pollen tube tips in P. thunbergii contained an enriched network of microtubules. Ion implantation led to the disruption of microtubules especially in swollen tips. Treatment with colchicine demonstrated that tip swelling was caused by the disruption of microtubules in the tip, indicating a unique role for microtubules in maintaining the tip integrality of the pollen tube in conifer. Our results suggest that ion implantation induce the disruption of microtubule organization in pollen and pollen tubes and subsequently cause morphological abnormalities in the pollen tubes. This study may provide a clue for further investigation on the interaction between low-energy ion beams and pollen tube growth.

  13. Surface Etching and DNA Damage Induced by Low-Energy Ion Irradiation in Yeast

    NASA Astrophysics Data System (ADS)

    Liu, Xuelan; Xu, An; Dai, Yin; Yuan, Hang; Yu, Zengliang

    2011-06-01

    Bio-effects of survival and etching damage on cell surface and DNA strand breaks were investigated in the yeast saccharomyces cerevisiae after exposure by nitrogen ion with an energy below 40 keV. The result showed that 16% of trehalose provided definite protection for cells against vacuum stress compared with glycerol. In contrast to vacuum control, significant morphological damage and DNA strand breaks were observed, in yeast cells bombarded with low-energy nitrogen, by scanning electron microscopy (SEM) and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) immunofluorescence assays. Moreover, PI (propidium iodide) fluorescent staining indicated that cell integrity could be destroyed by ion irradiation. Cell damage eventually affected cell viability and free radicals were involved in cell damage as shown by DMSO (dimethyl sulfoxide) rescue experiment. Our primary experiments demonstrated that yeast cells can be used as an optional experimental model to study the biological effects of low energy ions and be applied to further investigate the mechanism(s) underlying the bio-effects of eukaryotic cells.

  14. Calculation of astrophysical S factor at low energy levels

    NASA Astrophysics Data System (ADS)

    Andic, Halil Ibrahim; Ozer, Okan

    2017-02-01

    Nuclear reactions are very important for the structure, evolution, nucleosynthesis and various observational manifestations of main-sequence stars, white dwarfs and neutron stars. For astrophysical applications, one needs to know value of S-factor for many reactions at low energies. The experimental measurements of cross-sections at such low energies are essentially not easily available since the Coulomb barrier. Theoretical calculations are model dependent, so that nuclear physics uncertainties of calculated S-factor can be substantial. Using the supersymmetric quantum mechanics one can obtain the supersymmetric partner potential that can vary by several orders of magnitude in the energy range of a given reaction in the calculation of S factor. Since the determination of reaction rates requires accurate values of cross sections at very low energies, then in order to eliminate the main part of the energy dependence of these cross sections one makes use of the astrophysical S-factor in Taylor Expansion series about zero-energy.

  15. Coulomb effects in low-energy nuclear fragmentation

    NASA Technical Reports Server (NTRS)

    Wilson, John W.; Chun, Sang Y.; Badavi, Francis F.; John, Sarah

    1993-01-01

    Early versions of the Langley nuclear fragmentation code NUCFRAG (and a publicly released version called HZEFRG1) assumed straight-line trajectories throughout the interaction. As a consequence, NUCFRAG and HZEFRG1 give unrealistic cross sections for large mass removal from the projectile and target at low energies. A correction for the distortion of the trajectory by the nuclear Coulomb fields is used to derive fragmentation cross sections. A simple energy-loss term is applied to estimate the energy downshifts that greatly alter the Coulomb trajectory at low energy. The results, which are far more realistic than prior versions of the code, should provide the data base for future transport calculations. The systematic behavior of charge-removal cross sections compares favorably with results from low-energy experiments.

  16. Low energy analyzing powers in pion-proton elastic scattering

    NASA Astrophysics Data System (ADS)

    Meier, R.; Cröni, M.; Bilger, R.; van den Brandt, B.; Breitschopf, J.; Clement, H.; Comfort, J. R.; Denz, H.; Erhardt, A.; Föhl, K.; Friedman, E.; Gräter, J.; Hautle, P.; Hofman, G. J.; Konter, J. A.; Mango, S.; Pätzold, J.; Pavan, M. M.; Wagner, G. J.; von Wrochem, F.

    2004-05-01

    Analyzing powers of pion-proton elastic scattering have been measured at PSI with the Low Energy Pion Spectrometer LEPS and a novel polarized scintillator target. Angular distributions between 40 and 120 deg (c.m.) were taken at 45.2, 51.2, 57.2, 68.5, 77.2, and 87.2 MeV incoming pion kinetic energy for π+p scattering, and at 67.3 and 87.2 MeV for π-p scattering. These new measurements constitute a substantial extension of the polarization data base at low energies. Predictions from phase shift analyses are compared with the experimental results, and deviations are observed at low energies.

  17. Light element production by low energy nuclei from massive stars

    NASA Technical Reports Server (NTRS)

    Vangioni-Flam, E.; Casse, M.; Ramaty, R.

    1997-01-01

    The Orion complex is a source of gamma rays attributed to the de-excitation of fast carbon and oxygen nuclei excited through interactions with ambient hydrogen and helium. This has consequences for the production and evolution of light isotopes in the Galaxy, as massive stars appear as prolific sources of C-O rich low energy nuclei. The different stages of massive star evolution are considered in relation to the acceleration of nuclei to moderate energies. It is concluded that the low energy nuclear component originating from massive stars plays a larger role than the usual Galactic cosmic rays in shaping the evolution of Li-6, Be-9, B-10 and B-11, especially in the early Galactic evolution. The enhancement of the B-11/B-10 ratio observed in meteorites and in the interstellar medium is attributed to the interaction of low energy carbon nuclei with ambient H and to a lesser degree, to neutrino spallation.

  18. The problem of low energy particle measurements in the magnetosphere

    NASA Technical Reports Server (NTRS)

    Whipple, E. C., Jr.

    1978-01-01

    The accurate measurement of low energy (less than 100 eV) particle properties in the magnetosphere has been difficult, partly because of the low density of such particles, but more particularly because of spacecraft interference effects. Some early examples of how these phenomena have affected particle measurements on an OGO spacecraft are presented. Data obtained with the UCSD particle detectors on ATS-6 are then presented showing how some of these difficulties have been partially overcome. Future measurements of low energy particles in the magnetosphere can be improved by: (1) improving the low energy resolution of detectors; (2) building electrostatically clean spacecraft; (3) controlling spacecraft potential; and (4) using auxiliary measurements, particularly wave data.

  19. Low-energy physics of high-temperature superconductors

    SciTech Connect

    Emery, V.J. . Physics Dept.); Kivelson, S.A. . Dept. of Physics)

    1992-01-01

    It is argued that the low-energy properties of high temperature superconductors are dominated by the interaction between the mobile holes and a particular class of collective modes, corresponding to local large-amplitude low-energy fluctuations in the hole density. The latter are a consequence of the competition between the effects of long-range Coulomb interactions and the tendency of a low concentration of holes in an antiferromagnet to phase separate. The low-energy behavior of the system is governed by the same fixed point as the two-channel Kondo problem, which accounts for the universality'' of the properties of the cuprate superconductors. Predictions of the optical properties and the spin dynamics are compared with experiment. The pairing resonance of the two Kondo problem gives a mechanism of high temperature superconductivity with an unconventional symmetry of the order parameter.

  20. Low-energy physics of high-temperature superconductors

    SciTech Connect

    Emery, V.J.; Kivelson, S.A.

    1992-09-01

    It is argued that the low-energy properties of high temperature superconductors are dominated by the interaction between the mobile holes and a particular class of collective modes, corresponding to local large-amplitude low-energy fluctuations in the hole density. The latter are a consequence of the competition between the effects of long-range Coulomb interactions and the tendency of a low concentration of holes in an antiferromagnet to phase separate. The low-energy behavior of the system is governed by the same fixed point as the two-channel Kondo problem, which accounts for the ``universality`` of the properties of the cuprate superconductors. Predictions of the optical properties and the spin dynamics are compared with experiment. The pairing resonance of the two Kondo problem gives a mechanism of high temperature superconductivity with an unconventional symmetry of the order parameter.

  1. EVOLUTION OF THE CRAB NEBULA IN A LOW ENERGY SUPERNOVA

    SciTech Connect

    Yang, Haifeng; Chevalier, Roger A. E-mail: rac5x@virginia.edu

    2015-06-20

    The nature of the supernova leading to the Crab Nebula has long been controversial because of the low energy that is present in the observed nebula. One possibility is that there is significant energy in extended fast material around the Crab but searches for such material have not led to detections. An electron capture supernova model can plausibly account for the low energy and the observed abundances in the Crab. Here, we examine the evolution of the Crab pulsar wind nebula inside a freely expanding supernova and find that the observed properties are most consistent with a low energy event. Both the velocity and radius of the shell material, and the amount of gas swept up by the pulsar wind point to a low explosion energy (∼10{sup 50} erg). We do not favor a model in which circumstellar interaction powers the supernova luminosity near maximum light because the required mass would limit the freely expanding ejecta.

  2. Evolution of the Crab Nebula in a Low Energy Supernova

    NASA Astrophysics Data System (ADS)

    Yang, Haifeng; Chevalier, Roger A.

    2015-06-01

    The nature of the supernova leading to the Crab Nebula has long been controversial because of the low energy that is present in the observed nebula. One possibility is that there is significant energy in extended fast material around the Crab but searches for such material have not led to detections. An electron capture supernova model can plausibly account for the low energy and the observed abundances in the Crab. Here, we examine the evolution of the Crab pulsar wind nebula inside a freely expanding supernova and find that the observed properties are most consistent with a low energy event. Both the velocity and radius of the shell material, and the amount of gas swept up by the pulsar wind point to a low explosion energy (∼1050 erg). We do not favor a model in which circumstellar interaction powers the supernova luminosity near maximum light because the required mass would limit the freely expanding ejecta.

  3. Electron polarimetry at low energies in Hall C at JLab

    NASA Astrophysics Data System (ADS)

    Gaskell, D.

    2013-11-01

    Although the majority of Jefferson Lab experiments require multi-GeV electron beams, there have been a few opportunities to make electron beam polarization measurements at rather low energies. This proceedings will discuss some of the practical difficulties encountered in performing electron polarimetry via Mo/ller scattering at energies on the order of a few hundred MeV. Prospects for Compton polarimetry at very low energies will also be discussed. While Mo/ller scattering is likely the preferred method for electron polarimetry at energies below 500 MeV, there are certain aspects of the polarimeter and experiment design that must be carefully considered.

  4. Electron polarimetry at low energies in Hall C at JLab

    SciTech Connect

    Gaskell, D.

    2013-11-07

    Although the majority of Jefferson Lab experiments require multi-GeV electron beams, there have been a few opportunities to make electron beam polarization measurements at rather low energies. This proceedings will discuss some of the practical difficulties encountered in performing electron polarimetry via Mo/ller scattering at energies on the order of a few hundred MeV. Prospects for Compton polarimetry at very low energies will also be discussed. While Mo/ller scattering is likely the preferred method for electron polarimetry at energies below 500 MeV, there are certain aspects of the polarimeter and experiment design that must be carefully considered.

  5. Scattering of low-energy neutrinos on atomic shells

    SciTech Connect

    Babič, Andrej; Šimkovic, Fedor

    2015-10-28

    We present a derivation of the total cross section for inelastic scattering of low-energy solar neutrinos and reactor antineutrinos on bound electrons, resulting in a transition of the electron to an excited state. The atomic-shell structure of various chemical elements is treated in terms of a nonrelativistic approximation. We estimate the interaction rates for modern neutrino detectors, in particular the Borexino and GEMMA experiments. We establish that in these experiments the effect can be safely neglected, but it could be accessible to future large-volume neutrino detectors with low energy threshold.

  6. Scattering of low-energy neutrinos on atomic shells

    NASA Astrophysics Data System (ADS)

    Babič, Andrej; Šimkovic, Fedor

    2015-10-01

    We present a derivation of the total cross section for inelastic scattering of low-energy solar neutrinos and reactor antineutrinos on bound electrons, resulting in a transition of the electron to an excited state. The atomic-shell structure of various chemical elements is treated in terms of a nonrelativistic approximation. We estimate the interaction rates for modern neutrino detectors, in particular the Borexino and GEMMA experiments. We establish that in these experiments the effect can be safely neglected, but it could be accessible to future large-volume neutrino detectors with low energy threshold.

  7. Diffuse Galactic low energy gamma ray continuum emission

    NASA Technical Reports Server (NTRS)

    Skibo, J. G.; Ramaty, R.

    1993-01-01

    We investigate the origin of diffuse low-energy Galactic gamma-ray continuum down to about 30 keV. We calculate gamma-ray emission via bremsstrahlung and inverse Compton scattering by propagating an unbroken electron power law injection spectrum and employing a Galactic emmissivity model derived from COSB observations. To maintain the low energy electron population capable of producing the observed continuum via bremsstrahlung, a total power input of 4 x 10 exp 41 erg/s is required. This exceeds the total power supplied to the nuclear cosmic rays by about an order of magnitude.

  8. Enhanced production of low energy electrons by alpha particle impact.

    PubMed

    Kim, Hong-Keun; Titze, Jasmin; Schöffler, Markus; Trinter, Florian; Waitz, Markus; Voigtsberger, Jörg; Sann, Hendrik; Meckel, Moritz; Stuck, Christian; Lenz, Ute; Odenweller, Matthias; Neumann, Nadine; Schössler, Sven; Ullmann-Pfleger, Klaus; Ulrich, Birte; Fraga, Rui Costa; Petridis, Nikos; Metz, Daniel; Jung, Annika; Grisenti, Robert; Czasch, Achim; Jagutzki, Ottmar; Schmidt, Lothar; Jahnke, Till; Schmidt-Böcking, Horst; Dörner, Reinhard

    2011-07-19

    Radiation damage to living tissue stems not only from primary ionizing particles but to a substantial fraction from the dissociative attachment of secondary electrons with energies below the ionization threshold. We show that the emission yield of those low energy electrons increases dramatically in ion-atom collisions depending on whether or not the target atoms are isolated or embedded in an environment. Only when the atom that has been ionized and excited by the primary particle impact is in immediate proximity of another atom is a fragmentation route known as interatomic Coulombic decay (ICD) enabled. This leads to the emission of a low energy electron. Over the past decade ICD was explored in several experiments following photoionization. Most recent results show its observation even in water clusters. Here we show the quantitative role of ICD for the production of low energy electrons by ion impact, thus approaching a scenario closer to that of radiation damage by alpha particles: We choose ion energies on the maximum of the Bragg peak where energy is most efficiently deposited in tissue. We compare the electron production after colliding He(+) ions on isolated Ne atoms and on Ne dimers (Ne(2)). In the latter case the Ne atom impacted is surrounded by a most simple environment already opening ICD as a deexcitation channel. As a consequence, we find a dramatically enhanced low energy electron yield. The results suggest that ICD may have a significant influence on cell survival after exposure to ionizing radiation.

  9. MEIC Proton Beam Formation with a Low Energy Linac

    SciTech Connect

    Zhang, Yuhong

    2015-09-01

    The MEIC proton and ion beams are generated, accumulated, accelerated and cooled in a new green-field ion injector complex designed specifically to support its high luminosity goal. This injector consists of sources, a linac and a small booster ring. In this paper we explore feasibility of a short ion linac that injects low-energy protons and ions into the booster ring.

  10. Mirrored low-energy channel for the MiniXRD

    SciTech Connect

    Dutra, Eric; MacNeil, Lawrence; Raphaelian, Mark; Compton, Steve; Jacoby, Barry

    2015-10-08

    X-ray Diodes (XRDs) are currently used for spectroscopic measurements, measuring X-ray flux, and estimating spectral shape of the VUV to soft X-ray spectrum. A niche exists for an inexpensive, robust X-ray diode that can be used for experiments in hostile environments on multiple platforms, including explosively driven experiments that have the potential for destroying the diode during the experiment. A multiple channel stacked filtered array was developed with a small field of view where a wider parallel array could not be used, but filtered channels for energies lower than 1000 eV were too fragile to deploy under normal conditions. To achieve both the robustness and the required low-energy detection ability, the researchers designed a small low-energy mirrored channel with a spectral sensitivity from 30 to 1000 eV. The stacked MiniXRD X-ray diode system design incorporates the mirrored low-energy channel on the front of the stacked filtered channels to allow the system to work within a small field of view. We will present results that demonstrate this is a promising solution for low-energy spectrum measurements.

  11. Nuclear phenomena in low-energy nuclear reaction research.

    PubMed

    Krivit, Steven B

    2013-09-01

    This is a comment on Storms E (2010) Status of Cold Fusion, Naturwissenschaften 97:861-881. This comment provides the following remarks to other nuclear phenomena observed in low-energy nuclear reactions aside from helium-4 make significant contributions to the overall energy balance; and normal hydrogen, not just heavy hydrogen, produces excess heat.

  12. Study of Intrabeam Scattering in Low Energy Electron Rings

    SciTech Connect

    Venturini, Marco

    2002-08-08

    The paper contains a study of intrabeam scattering in a low energy electron storage ring to be used as part of a Compton back-scattering x-ray source. We discuss time evolution of emittance and dependence of IBS growth rates on lattice parameters.

  13. Low Energy Transfer Reactions With {sup 11}Be

    SciTech Connect

    Johansen, Jacob

    2009-08-26

    The low-energy transfer reaction {sup 11}Be(d,p){sup 12}Be gives us the opportunity to investigate single particle excitations in {sup 12}Be. The breaking of the magic number N = 8 for {sup 12}Be can be studied by comparing spectroscopic data with theoretical predictions.

  14. ELECTRON COOLING SIMULATIONS FOR LOW-ENERGY RHIC OPERATION.

    SciTech Connect

    FEDOTOV,A.V.; BEN-ZVI, I.; CHANG, X.; KAYRAN, D.; SATOGATA, T.

    2007-09-10

    Recently, a strong interest emerged in running the Relativistic Heavy Ion Collider (RHIC) at low beam total energies of 2.5-25 GeV/nucleon, substantially lower than the nominal beam total energy of 100 GeV/nucleon. Collisions in this low energy range are motivated by one of the key questions of quantum chromodynamics (QCD) about the existence and location of critical point on the QCD phase diagram. Applying electron cooling directly at these low energies in RHIC would result in significant luminosity increase and long beam stores for physics. Without direct cooling in RHIC at these low energies, beam lifetime and store times are very short, limited by strong transverse and longitudinal intrabeam scattering (IBS). In addition, for the lowest energies of the proposed energy scan, the longitudinal emittance of ions injected from the AGS into RHIC may be too big to fit into the RHIC RF bucket. An improvement in the longitudinal emittance of the ion beam can be provided by an electron cooling system at the AGS injection energy. Simulations of electron cooling both for direct cooling at low energies in RHIC and for injection energy cooling in the AGS were performed and are summarized in this report.

  15. String-Loop Effect in Low-Energy Effective Theory

    NASA Astrophysics Data System (ADS)

    Saadat, H.; Tanabchi, B. P.; Saadat, A. M.

    2010-05-01

    In this short article we are going to obtain the equations of motion from the low-energy effective action in the string cosmology. In the first time we consider the string-loop effect in the dilaton gravity and obtain the equations of motion, and obtain solution of them under some assumption for the specific potential.

  16. Physics overview of the Fermilab Low Energy Antiproton Facility Workshop

    SciTech Connect

    Chanowitz, M.S.

    1986-05-01

    A physics overview is presented of the Fermilab workshop to consider a possible high flux, low energy antiproton facility that would use cooled antiprotons from the accumulator ring of the Tevatron collider. Two examples illustrate the power of each a facility to produce narrow states at high rates. Physics topics to which such a facility may be applied are reviewed.

  17. Low energy physics and properties of extra space

    NASA Astrophysics Data System (ADS)

    Rubin, Sergey G.

    2013-02-01

    The mechanism of low energy physics formation in the framework of multidimensional gravity is discussed. It is shown that a wide set of parameters of a primary theory could lead to the observable Universe. Quantum fluctuations of extra space metric and its consequent classical evolution play an important role in this process.

  18. Potential for luminosity improvement for low-energy RHIC operation

    SciTech Connect

    Fedotov A. V.

    2012-05-20

    At the Brookhaven National Laboratory, a physics program, motivated by the search of the QCD phase transition critical point, requires operation of the Relativistic Heavy Ion Collider (RHIC) with heavy ions at very low beam energies corresponding to 2.5-20 GeV/n. Several physics runs were already successfully performed at these low energies. However, the luminosity is very low at lowest energies of interest (< 10 GeV/n) limited by the intra-beam scattering and space-charge, as well as by machine nonlinearities. At these low energies, electron cooling could be very effective in counteracting luminosity degradation due to the IBS, while it is less effective against other limitations. Overall potential luminosity improvement for low-energy RHIC operation from cooling is summarized for various energies, taking into account all these limitations as well as beam lifetime measured during the low-energy RHIC runs. We also explore a possibility of further luminosity improvement under the space-charge limitation.

  19. HEAO-1 analysis of Low Energy Detectors (LED)

    NASA Technical Reports Server (NTRS)

    Nousek, John A.

    1992-01-01

    The activities at Penn State University are described. During the period Oct. 1990 to Dec. 1991 work on HEAO-1 analysis of the Low Energy Detectors (LED) concentrated on using the improved detector spectral simulation model and fitting diffuse x-ray background spectral data. Spectral fitting results, x-ray point sources, and diffuse x-ray sources are described.

  20. Low-energy plasma observations at synchronous orbit

    NASA Technical Reports Server (NTRS)

    Lennartsson, W.; Reasoner, D. L.

    1978-01-01

    The University of California at San Diego Auroral Particles Experiment on the ATS 6 satellite in synchronous orbit has detected a low-energy plasma population which is separate and distinct from both the ring current and the plasma sheet populations. The density and temperature of this low-energy population are highly variable, with temperatures in the range kT = 1-30 eV and densities ranging from less than 1 per cu cm to more than 10 per cu cm. The occurrence of a dense low-energy plasma is most likely in the afternoon and dusk local time sectors, whereas n greater than 1 per cu cm is seen in the local night sector only during magnetically quiet periods. These observations suggest that this plasma is the outer zone of the plasmasphere. During magnetically active periods this low-energy plasma is often observed flowing sunward. In the dusk sector, strong sunward plasma flow is often observed for 1-2 hours prior to the onset of a substorm-associated particle injection.

  1. Low energy x-ray response of Ge detectors with amorphous Ge entrance contacts

    SciTech Connect

    Luke, P.N.; Rossington, C.S.; Wesela, M.F.

    1993-10-01

    The low energy x-ray response of GI detectors with amorphous GI entrance contacts has been evaluated. The spectral background due to near contact incomplete charge collection was found to consist of two components: a low level component which is insensitive to applied voltage and a high level step-like component which is voltage dependent. At high operating voltages, the high level component can be completely suppressed, resulting in background levels which are much lower than those previously observed using GI detectors with Pd surface barrier or B ion implanted contacts, and which also compare favorably to those obtained with Si(Li) x-ray detectors. The response of these detectors to {sup 55}Fe and 1.77 keV x-rays is shown. A qualitative explanation of the origins of the observed background components is presented.

  2. Spatially dependent cluster dynamics modeling of microstructure evolution in low energy helium irradiated tungsten

    NASA Astrophysics Data System (ADS)

    Faney, T.; Wirth, B. D.

    2014-09-01

    In fusion reactors, plasma facing components (PFC) and in particular the divertor will be irradiated with high fluxes of low energy (˜100 eV) helium and hydrogen ions. Tungsten is one of the leading candidate divertor materials for ITER and DEMO fusion reactors. However, the behavior of tungsten under high dose, coupled helium/hydrogen exposure remains to be fully understood. The PFC response and performance changes are intimately related to microstructural changes, such as the formation of point defect clusters, helium and hydrogen bubbles or dislocation loops. Computational materials modeling has been used to investigate the mechanisms controlling microstructural evolution in tungsten following high dose, high temperature helium exposure. The aim of this study is to understand and predict helium implantation, primary defect production and defect diffusion, helium-defect clustering and interactions below a tungsten surface exposed to low energy helium irradiation. The important defects include interstitial clusters, vacancy clusters, helium interstitials and helium-vacancy clusters. We report results from a one-dimensional, spatially dependent cluster dynamics model based on the continuum reaction-diffusion rate theory to describe the evolution in space and time of all these defects. The key parameter inputs to the model (diffusion coefficients, migration and binding energies, initial defect production) are determined from a combination of atomistic materials modeling and available experimental data.

  3. Low-energy shock waves enhance the susceptibility of staphylococcal biofilms to antimicrobial agents in vitro.

    PubMed

    Wanner, S; Gstöttner, M; Meirer, R; Hausdorfer, J; Fille, M; Stöckl, B

    2011-06-01

    Biofilm-associated infections in wounds or on implants are difficult to treat. Eradication of the bacteria is nearly always impossible, despite the use of specific antibiotics. The bactericidal effects of high-energy extracorporeal shock waves on Staphylococcus aureus have been reported, but the effect of low-energy shock waves on staphylococci and staphylococcal biofilms has not been investigated. In this study, biofilms grown on stainless steel washers were examined by electron microscopy. We tested ten experimental groups with Staph. aureus-coated washers and eight groups with Staph. epidermidis. The biofilm-cultured washers were exposed to low-energy shock waves at 0.16 mJ/mm(2) for 500 impulses. The washers were then treated with cefuroxime, rifampicin and fosfomycin, both alone and in combination. All tests were carried out in triplicate. Viable cells were counted to determine the bactericidal effect. The control groups of Staph. aureus and Staph. epidermidis revealed a cell count of 6 × 10(8) colony-forming units/ml. Complete eradication was achieved using the combination of antibiotic therapy (single antibiotic in Staph. aureus, a combination in Staph. epidermidis) and shock wave application (p < 0.01). We conclude that shock waves combined with antibiotics could be tested in an in vitro model of infection.

  4. Cochlear Implants.

    ERIC Educational Resources Information Center

    Clark, Catherine; Scott, Larry

    This brochure explains what a cochlear implant is, lists the types of individuals with deafness who may be helped by a cochlear implant, describes the process of evaluating people for cochlear implants, discusses the surgical process for implanting the aid, traces the path of sound through the cochlear implant to the brain, notes the costs of…

  5. High pressure phases produced by low energy ion implantation with reference to cubic boron nitride

    NASA Astrophysics Data System (ADS)

    McKenzie, D. R.; McFall, W. D.; Smith, H.; Higgins, B.; Boswell, R. W.; Durandet, A.; James, B. W.; Falconer, I. S.

    1995-12-01

    Cubic boron nitride (c-BN) is a high quality abrasive material with hardness second only to diamond and with good oxidation and solubility properties. A new ion plating technique using the helicon wave plasma source combined with electron beam evaporation has been developed for the large area, high rate deposition of this material. The apparatus is fitted with a multiwavelength in situ ellipsometer for monitoring growth. The optical properties of both c-BN and h-BN films have been measured in situ and the operating conditions which produce a high growth rate of c-BN have been determined. A simple model for the movement of boron through the system has been developed and compared to experiment.

  6. Low-energy proton increases associated with interplanetary shock waves.

    NASA Technical Reports Server (NTRS)

    Palmeira, R. A. R.; Allum, F. R.; Rao, U. R.

    1971-01-01

    Impulsive increases in the low energy proton flux observed by the Explorer 34 satellite, in very close time association with geomagnetic storm sudden commencements are described. It is shown that these events are of short duration (20-30 min) and occur only during the decay phase of a solar cosmic-ray flare event. The differential energy spectrum and the angular distribution of the direction of arrival of the particles are discussed. Two similar increases observed far away from the earth by the Pioneer 7 and 8 deep-space probes are also presented. These impulsive increases are compared with Energetic Storm Particle events and their similarities and differences are discussed. A model is suggested to explain these increases, based on the sweeping and trapping of low energy cosmic rays of solar origin by the advancing shock front responsible for the sudden commencement detected on the earth.

  7. Ionization cooling in a low-energy proton storage ring

    SciTech Connect

    Neuffer, David V.; /Fermilab

    2006-03-01

    At the FFAG05 meeting, Mori and Okabe presented a scenario in which the lifetime of protons in a low-energy storage ring ({approx}10 MeV) is extended by energy-loss in a wedge foil, and this enables greater neutron production from the foil. The lifetime extension is due to the cooling effect of this energy loss. We have previously analyzed ionization cooling for muons at optimal cooling energies. The same equations, with appropriate adaptations, can be used to analyze the dynamic situation for proton-material interactions at low energies. In this note we discuss this extension and calculate cooling and heating effects at these very different parameters. The ring could provide a practical application of ionization cooling methods.

  8. Influence of Packing on Low Energy Vibrations of Densified Glasses

    NASA Astrophysics Data System (ADS)

    Carini, Giovanni, Jr.; Carini, Giuseppe; D'Angelo, Giovanna; Tripodo, Gaspare; Di Marco, Gaetano; Vasi, Cirino; Gilioli, Edmondo

    2013-12-01

    A comparative study of Raman scattering and low temperature specific heat capacity has been performed on samples of B2O3, which have been high-pressure quenched to go through different glassy phases having growing density to the crystalline state. It has revealed that the excess volume characterizing the glassy networks favors the formation of specific glassy structural units, the boroxol rings, which produce the boson peak, a broad band of low energy vibrational states. The decrease of boroxol rings with increasing pressure of synthesis is associated with the progressive depression of the excess low energy vibrations until their full disappearance in the crystalline phase, where the rings are missing. These observations prove that the additional soft vibrations in glasses arise from specific units whose formation is made possible by the poor atomic packing of the network.

  9. Beam dynamics limits for low-energy RHIC operation

    SciTech Connect

    Fedotov,A.V.; Ben-Zvi, I.; Chang, X.; Kayran, D.; Litvinenko, V.N.; Pozdeyev, E.; Satogata, T.

    2008-08-25

    There is a strong interest in low-energy RHIC operations in the single-beam total energy range of 2.5-25 GeV/nucleon [1-3]. Collisions in this energy range, much of which is below nominal RHIC injection energy, will help to answer one of the key questions in the field of QCD about the existence and location of a critical point on the QCD phase diagram [4]. There have been several short test runs during 2006-2008 RHIC operations to evaluate RHIC operational challenges at these low energies [5]. Beam lifetimes observed during the test runs were limited by machine nonlinearities. This performance limit can be improved with sufficient machine tuning. The next luminosity limitation comes from transverse and longitudinal Intra-beam Scattering (IBS), and ultimately from the space-charge limit. Here we summarize dynamic effects limiting beam lifetime and possible improvement with electron cooling.

  10. Low-energy dipole modes in unstable nuclei

    NASA Astrophysics Data System (ADS)

    Suzuki, T.; Sagawa, H.

    2001-01-01

    Enhancement of electric dipole (E1) strength at low energy is investigated in light neutron and proton drip-line nuclei with halo or skin by large scale shell model calculations. Large E1 strength are found in low excitation energy region below 5 MeV in 11Li, 12Be and 13O. Both the effects of extended halo or skin wave functions and the coherence in the transition amplitudes are important to enhance the E1 strength. The particle (hole)- vibration coupling model is shown to explain the splitting of the low energy E1 strength in 11Li and 13O. Melting of the shell magicity at N=8 and Z=8 is pointed out. Pigmy resonances in oxygen isotopes are also studied. The pigmy strength below E x = 15 MeV are shown to have about 10 % of the Thomas- Reiche-Kuhn (TRK) sum rule and more than 40 % of the cluster sum rule.

  11. Polarimeter for Low Energy X-ray Astrophysical Sources (PLEXAS)

    NASA Technical Reports Server (NTRS)

    Murray, Stephen S.; Pierce, David L. (Technical Monitor)

    2002-01-01

    The Polarimeter for Low Energy X-ray Astrophysical Sources (PLEXAS) is an astrophysics mission concept for measuring the polarization of X-ray sources at low energies below the C-K band (less than 277 eV). PLEXAS uses the concept of variations in the reflectivity of a multilayered X-ray telescope as a function of the orientation of an X-rays polarization vector with respect to the reflecting surface of the optic. By selecting an appropriate multilayer, and rotating the X-ray telescope while pointing to a source, there will be a modulation in the source intensity, as measured at the focus of the telescope, which is proportional to the degree of polarization in the source.

  12. HIGH POWER OPERATIONS AT THE LOW ENERGY DEMONSTRATION ACCELERATOR (LEDA)

    SciTech Connect

    M. DURAN; V. R. HARRIS

    2001-01-01

    Recently, the Low-Energy Demonstration Accelerator (LEDA) portion of the Accelerator Production of Tritium (APT) project reached its 100-mA, 8-hr continuous wave (CW) beam operation milestone. The LEDA accelerator is a prototype of the low-energy front-end of the linear accelerator (linac) that would have been used in an APT plant. LEDA consists of a 75-keV proton injector, 6.7-MeV, 350-MHz CW radio-frequency quadrupole (RFQ) with associated high-power and low-level RF systems, a short high-energy beam transport (HEBT) and high-power (670-kW CW) beam dump. Details of the LEDA design features will be discussed along with the operational health physics experiences that occurred during the LEDA commissioning phase.

  13. Antineutron and antiproton nuclear interactions at very low energies

    NASA Astrophysics Data System (ADS)

    Friedman, E.

    2014-05-01

    Experimental annihilation cross sections of antineutrons and antiprotons at very low energies are compared. Features of Coulomb focusing are observed for pbar annihilation on protons. Direct comparisons for heavier targets are not straightforward due to lack of overlap between targets and energies of experimental results for pbar and nbar. Nevertheless, the annihilation cross sections for nbar on nuclei cannot be described by an optical potential that fits well all the available data on pbar interactions with nuclei. Comparisons made with the help of this potential reveal in the nbar data features similar to Coulomb focusing. Direct comparisons between nbar and pbar annihilations at very low energies would be possible when pbar cross sections are measured on the same targets and at the same energies as the available cross sections for nbar. Such measurements may be possible in the foreseeable future.

  14. Steering continuum electron dynamics by low-energy attosecond streaking

    NASA Astrophysics Data System (ADS)

    Geng, Ji-Wei; Xiong, Wei-Hao; Xiao, Xiang-Ru; Gong, Qihuang; Peng, Liang-You

    2016-08-01

    A semiclassical model is developed to understand the electronic dynamics in the low-energy attosecond streaking. Under a relatively strong infrared (IR) pulse, the low-energy part of photoelectrons initialized by a single attosecond pulse (SAP) can either rescatter with the ionic core and induce interferences structures in the momentum spectra of the ionized electrons or be recaptured into the Rydberg states. The Coulomb potential plays essential roles in both the electron rescattering and recapturing processes. We find that by changing the time delay between the SAP and the IR pulse, the photoelectrons yield or the population of the Rydberg states can be effectively controlled. The present study demonstrates a fascinating way to steer the electron motion in the continuum.

  15. Surface modification using low energy ground state ion beams

    NASA Technical Reports Server (NTRS)

    Chutjian, Ara (Inventor); Hecht, Michael H. (Inventor); Orient, Otto J. (Inventor)

    1990-01-01

    A method of effecting modifications at the surfaces of materials using low energy ion beams of known quantum state, purity, flux, and energy is presented. The ion beam is obtained by bombarding ion-generating molecules with electrons which are also at low energy. The electrons used to bombard the ion generating molecules are separated from the ions thus obtained and the ion beam is directed at the material surface to be modified. Depending on the type of ion generating molecules used, different ions can be obtained for different types of surface modifications such as oxidation and diamond film formation. One area of application is in the manufacture of semiconductor devices from semiconductor wafers.

  16. Low energy overlineKN interaction in nuclear matter

    NASA Astrophysics Data System (ADS)

    Waas, T.; Kaiser, N.; Weise, W.

    1996-02-01

    We investigate the low-energy overlineKN interaction in nuclear matter including Pauli blocking, Fermi motion and binding effects. We use a coupled-channel approach based on the Chiral SU(3) Effective Lagrangian which describes all available low energy data of the coupled overlineKN, πΣ, πΛ system. Due to the dynamics of the Λ (1405) resonance we find a strong non-linear density dependence of the K -p scattering amplitude in nuclear matter. The real part of the K -p scattering length changes sign already at a small fraction of nuclear matter density, less than 0.2 po. This may explain the striking behaviour of the K - -nuclear optical potential found in the analysis of kaonic atom data.

  17. Unparticle searches through low energy parity violating asymmetry

    SciTech Connect

    Ozansoy, K. O.

    2008-11-01

    In this paper, we study the effects of the unparticles on the parity violating asymmetry for the low energy electron-electron scattering, e{sup -}e{sup -}{yields}e{sup -}e{sup -}. Using the data from the E158 experiment at SLAC we extract the limits on the unparticle coupling {lambda}{sub AV}, and on the energy scale {lambda} at 95% C.L. for various values of the scaling dimension d.

  18. Full QED+QCD low-energy constants through reweighting.

    PubMed

    Ishikawa, Tomomi; Blum, Thomas; Hayakawa, Masashi; Izubuchi, Taku; Jung, Chulwoo; Zhou, Ran

    2012-08-17

    The effect of sea quark electromagnetic charge on meson masses is investigated, and first results for full QED+QCD low-energy constants are presented. The electromagnetic charge for sea quarks is incorporated in quenched QED+full QCD lattice simulations by a reweighting method. The reweighting factor, which connects quenched and unquenched QED, is estimated using a stochastic method on 2+1 flavor dynamical domain-wall quark ensembles.

  19. Pin diode calibration - beam overlap monitoring for low energy cooling

    SciTech Connect

    Drees, A.; Montag, C.; Thieberger, P.

    2015-09-30

    We were trying to address the question whether or not the Pin Diodes, currently installed approximately 1 meter downstream of the RHIC primary collimators, are suitable to monitor a recombination signal from the future RHIC low energy cooling section. A maximized recombination signal, with the Au+78 ions being lost on the collimator, will indicate optimal Au-electron beam overlap as well as velocity matching of the electron beam in the cooling section.

  20. Selected Papers on Low-Energy Antiprotons and Possible Applications

    SciTech Connect

    Noble, Robert

    1998-09-19

    The only realistic means by which to create a facility at Fermilab to produce large amounts of low energy antiprotons is to use resources which already exist. There is simply too little money and manpower at this point in time to generate new accelerators on a time scale before the turn of the century. Therefore, innovation is required to modify existing equipment to provide the services required by experimenters.

  1. Low energy cosmic ray studies from a lunar base

    NASA Technical Reports Server (NTRS)

    Wiedenbeck, Mark E.

    1990-01-01

    Studies of cosmic ray nuclei with energies less than about 7 GeV/nucleon in low earth orbit are hampered by the geomagnetic field. Even in high inclination orbits these effects can be significant. The lunar surface (or lunar orbit) provides an attractive site for carrying out low energy cosmic ray studies which require large detectors. The rationale and requirements for this type of experiment are described.

  2. Strangeness-conserving hadronic parity violation at low energies

    NASA Astrophysics Data System (ADS)

    Liu, C.-P.

    2007-05-01

    The parity-violating nucleaon interacton is the key to understanding the strangeness-conserving hadronic weak interaction at low energies. In this brief talk, I review the past accomplishement in and current status of this subject, and outline a new joint effort between experiment and theory that that tries to address the potential problems in the past by focusing on parity violation in few-nucleon systems and using the language of effective field theory.

  3. Low-energy structures in strong-field ionization

    NASA Astrophysics Data System (ADS)

    Ivanov, I. A.; Nam, Chang Hee; Kim, Kyung Taec

    2016-04-01

    We show that the Gabor transform provides a convenient tool allowing one to study the origin of the low-energy structures (LES) in the process of the strong-field ionization. The classical trajectories associated with the stationary points of the Gabor transform enable us to explicate the role of the forward scattering process in forming LES. Our approach offers a fully quantum mechanical description of LES, which can also be applied for other strong-field processes.

  4. Exchange and relaxation effects in low-energy radiationless transitions

    NASA Technical Reports Server (NTRS)

    Chen, M. H.; Crasemann, B.; Aoyagi, M.; Mark, H.

    1978-01-01

    The effect on low-energy atomic inner-shell Coster-Kronig and super Coster-Kronig transitions that is produced by relaxation and by exchange between the continuum electron and bound electrons was examined and illustrated by specific calculations for transitions that deexcite the 3p vacancy state of Zn. Taking exchange and relaxation into account is found to reduce, but not to eliminate, the discrepancies between theoretical rates and measurements.

  5. Nuclear suppression at low energy in relativistic heavy ion collisions

    SciTech Connect

    Das, Santosh K.; Alam, Jan-e; Mohanty, Payal; Sinha, Bikash

    2010-04-15

    The effects of nonzero baryonic chemical potential on the drag and diffusion coefficients of heavy quarks propagating through a baryon-rich quark-gluon plasma have been studied. The nuclear suppression factor R{sub AA} for nonphotonic single-electron spectra resulting from the semileptonic decays of hadrons containing heavy flavors has been evaluated for low-energy collisions. The effect of nonzero baryonic chemical potential on R{sub AA} is highlighted.

  6. HgI sub 2 low energy beta particle detector

    SciTech Connect

    Shah, K.S.; Squillante, M.R.; Entine, G. )

    1990-04-01

    This paper reports on a HgI{sub 2} device structure designed and tested which allows HgI{sub 2} to be used to make low energy beta particle detectors. The devices detected tritium beta particles with about a 25% efficiency. In addition, an encapsulation scheme was identified which has the potential to protect the devices while permitting most of the beta particles to reach the active region.

  7. Low energy cosmic ray studies from a lunar base

    SciTech Connect

    Wiedenbeck, M.E. Department of Physics, University of Chicago, Chicago, IL )

    1990-03-15

    Studies of cosmic ray nuclei with energies {approx lt}7 GeV/nucleon in low Earth orbit are hampered by the geomagnetic field. Even in high inclination orbits these effects can be significant. The lunar surface (or lunar orbit) provides an attractive site for carrying out low energy cosmic ray studies which require large detectors. The rationale and requirements for this type of experiment are described.

  8. Heavy Meson Production at a Low-Energy Photon Collider

    SciTech Connect

    Asztalos, S

    2004-04-15

    A low-energy {gamma}{gamma} collider has been discussed in the context of a testbed for a {gamma}{gamma} interaction region at the Next Linear Collider(NLC). We consider the production of heavy mesons at such a testbed using Compton-backscattered photons and demonstrate that their production rivals or exceeds those by BELLE, BABAR or LEP where they are produced indirectly via virtual {gamma}{gamma} luminosities.

  9. Modern Theories of Low-Energy Astrophysical Reactions

    SciTech Connect

    Rocco Schiavilla

    2004-02-01

    We summarize recent ab initio studies of low-energy electroweak reactions of astrophysical interest, relevant for both big bang nucleosynthesis and solar neutrino production. The calculational methods include direct integration for np radiative and pp weak capture, correlated hyperspherical harmonics for reactions of A=3,4 nuclei, and variational Monte Carlo for A=6,7 nuclei. Realistic nucleon-nucleon and three-nucleon interactions and consistent current operators are used as input.

  10. Negative ions as a source of low energy neutral beams

    SciTech Connect

    Fink, J.H.

    1980-01-01

    Little consideration has been given to the impact of recent developments in negative ion source technology on the design of low energy neutral beam injectors. However, negative ion sources of improved operating efficiency, higher gas efficiency, and smaller beam divergence will lead to neutral deuterium injectors, operating at less than 100 keV, with better operating efficiencies and more compact layouts than can be obtained from positive ion systems.

  11. Topical problems in low-energy neutrino physics

    NASA Astrophysics Data System (ADS)

    Smirnov, O. Yu.

    2013-12-01

    New data on solar-neutrino flux measurements are presented, and their compatibility with the Mikheev-Smirnov-Wolfenstein oscillation model is discussed. A review is given to topical problems in low-energy neutrino physics, such as the accurate measurement of the CNO-cycle neutrino flux, which is dictated by the data conflict about the chemical composition of the Sun, and a possibility of neutrino oscillations that do not fit into the three-flavor model.

  12. Low energy supersymmetry from the heterotic string landscape.

    PubMed

    Lebedev, Oleg; Nilles, Hans-Peter; Raby, Stuart; Ramos-Sánchez, Saúl; Ratz, Michael; Vaudrevange, Patrick K S; Wingerter, Akin

    2007-05-04

    We study possible correlations between properties of the observable and hidden sectors in heterotic string theory. Specifically, we analyze the case of the Z6-II orbifold compactification which produces a significant number of models with the spectrum of the supersymmetric standard model. We find that requiring realistic features does affect the hidden sector such that hidden sector gauge group factors SU(4) and SO(8) are favored. In the context of gaugino condensation, this implies low energy supersymmetry breaking.

  13. A study of low-energy type II supernovae

    NASA Astrophysics Data System (ADS)

    Lisakov, Sergey M.; Dessart, Luc; Hillier, D. John; Waldman, Roni; Livne, Eli

    2015-08-01

    All stars with an initial mass greater than 8Msun, but not massive enough to encounter the pair-production instability, eventually form a degenerate core and collapse to form a compact object, either a neutron star or a black hole.At the lower mass end, these massive stars die as red-supergiant stars and give rise to Type II supernovae (SNe). The diversity of observed properties of SNe II suggests a range of progenitor mass, radii, but also explosion energy.We have performed a large grid simulations designed to cover this range of progenitor and explosion properties. Using MESA STAR, we compute a set of massive star models (12-30Msun) from the main sequence until core collapse. We then generate explosions with V1D to produce ejecta with a range of explosion energies and yields. Finally, all ejecta are evolved with CMFGEN to generate multi-band light curves and spectra.In this poster, we focus our attention on the properties of low-energy explosions that give rise to low-luminosity Type II Plateau (II-P) SNe. In particular, we present a detailed study of SN 2008bk, but also include other notorious low-energy SNe II-P like 2005cs, emphasising their non-standard properties by comparing to models that match well events like SN 1999em. Such low-energy explosions, characterised by low ejecta expansion rates, are more suitable for reliable spectral line identifications.Based on our models, we discuss the distinct signatures of low-energy explosions in lower and higher mass models. One important goal is to identify whether there is a progenitor-mass bias leading to such events.

  14. Surface conversion techniques for low energy neutral atom imagers

    NASA Technical Reports Server (NTRS)

    Quinn, J. M.

    1995-01-01

    This investigation has focused on development of key technology elements for low energy neutral atom imaging. More specifically, we have investigated the conversion of low energy neutral atoms to negatively charged ions upon reflection from specially prepared surfaces. This 'surface conversion' technique appears to offer a unique capability of detecting, and thus imaging, neutral atoms at energies of 0.01 - 1 keV with high enough efficiencies to make practical its application to low energy neutral atom imaging in space. Such imaging offers the opportunity to obtain the first instantaneous global maps of macroscopic plasma features and their temporal variation. Through previous in situ plasma measurements, we have a statistical picture of large scale morphology and local measurements of dynamic processes. However, with in situ techniques it is impossible to characterize or understand many of the global plasma transport and energization processes. A series of global plasma images would greatly advance our understanding of these processes and would provide the context for interpreting previous and future in situ measurements. Fast neutral atoms, created from ions that are neutralized in collisions with exospheric neutrals, offer the means for remotely imaging plasma populations. Energy and mass analysis of these neutrals provides critical information about the source plasma distribution. The flux of neutral atoms available for imaging depends upon a convolution of the ambient plasma distribution with the charge exchange cross section for the background neutral population. Some of the highest signals are at relatively low energies (well below 1 keV). This energy range also includes some of the most important plasma populations to be imaged, for example the base of the cleft ion fountain.

  15. Electron cooling for low-energy RHIC program

    SciTech Connect

    Fedotov, A.; Ben-Zvi, I.; Chang, X.; Kayran, D.; Litvinenko, V.N.; Pendzick, A.; Satogata, T.

    2009-08-31

    Electron cooling was proposed to increase luminosity of the RHIC collider for heavy ion beam energies below 10 GeV/nucleon. Providing collisions at such energies, termed RHIC 'low-energy' operation, will help to answer one of the key questions in the field of QCD about existence and location of critical point on the QCD phase diagram. The electron cooling system should deliver electron beam of required good quality over energies of 0.9-5 MeV. Several approaches to provide such cooling were considered. The baseline approach was chosen and design work started. Here we describe the main features of the cooling system and its expected performance. We have started design work on a low-energy RHIC electron cooler which will operate with kinetic electron energy range 0.86-2.8 (4.9) MeV. Several approaches to an electron cooling system in this energy range are being investigated. At present, our preferred scheme is to transfer the Fermilab Pelletron to BNL after Tevatron shutdown, and to use it for DC non-magnetized cooling in RHIC. Such electron cooling system can significantly increase RHIC luminosities at low-energy operation.

  16. Interpretation of low-energy electron-CO2 scattering

    NASA Astrophysics Data System (ADS)

    Vanroose, W.; McCurdy, C. W.; Rescigno, T. N.

    2002-09-01

    Recent ab initio calculations of low-energy electron-CO2 scattering [Rescigno et al., Phys. Rev. A 65, 032716 (2002)] are interpreted using an analytically solvable model. The model, which treats two partial-wave Hamiltonians with different l values coupled by a long-range (d/r2) interaction, is a generalization of similar single-channel models that have previously been used to interpret the low-energy behavior of electron scattering by polar diatomic molecules. The present model is used to track the pole trajectories of both resonances and virtual states, both of which figure prominently in low-energy electron-CO2 scattering, in the plane of complex momentum. The connection between resonant and virtual states is found to display a different topology in the case of a polyatomic molecule than it does in diatomic molecules. In a polyatomic molecule, these states may have a conical intersection and consequently acquire a Berry phase along closed paths in two-dimensional vibrational motion. The analytic behavior of the S matrix is further modified by the presence of a geometry-dependent dipole moment.

  17. Saturation of low-energy antiproton annihilation on nuclei

    NASA Astrophysics Data System (ADS)

    Gal, A.; Friedman, E.; Batty, C. J.

    2000-10-01

    Recent measurements of very low-energy (pL<100 MeV//c) /p¯ annihilation on light nuclei reveal apparent suppression of annihilation upon increasing the atomic charge /Z and mass number /A. Using /p¯-nucleus optical potentials Vopt, fitted to /p¯-atom energy-shifts and -widths, we resolve this suppression as due to the strong effective repulsion produced by the very absorptive Vopt. The low-energy /p¯-nucleus wavefunction is kept substantially outside the nuclear surface and the resulting reaction cross section saturates as function of the strength of ImVopt. This feature, for /E>0, parallels the recent prediction, for /E<0, that the level widths of /p¯ atoms saturate and, hence, that /p¯ deeply bound atomic states are relatively narrow. Antiproton annihilation cross sections are calculated at pL=57 MeV//c across the periodic table, and their dependence on /Z and /A is classified and discussed with respect to the Coulomb focussing effect at very low energies.

  18. A Low energy neutrino factory for large theta(13)

    SciTech Connect

    Geer, Steve; Mena, Olga; Pascoli, Silvia; /Durham U., IPPP

    2007-01-01

    If the value of {theta}{sub 13} is within the reach of the upcoming generation of long-baseline experiments, T2K and NOvA, they show that a low-energy neutrino factory, with peak energy in the few GeV range, would provide a sensitive tool to explore CP-violation and the neutrino mass hierarchy. They consider baselines with typical length 1000-1500 km. The unique performance of the low energy neutrino factory is due to the rich neutrino oscillation pattern at energies between 1 and 4 GeV at baselines {Omicron}(1000) km. They perform both a semi-analytical study of the sensitivities and a numerical analysis to explore how well this setup can measure {theta}{sub 13}, CP-violation, and determine the type of mass hierarchy and the {theta}{sub 23} quadrant. A low energy neutrino factory provides a powerful tool to resolve ambiguities and make precise parameter determinations, for both large and fairly small values of the mixing parameter {theta}{sub 13}.

  19. Advances in low energy neutral atom imaging techniques

    SciTech Connect

    Scime, E.E.; Funsten, H.O.; McComas, D.J.; Moore, K.R. ); Gruntman, M. . Space Sciences Center)

    1993-01-01

    Recently proposed low energy neutral atom (LENA) imaging techniques use a collisional process to convert the low energy neutrals into ions before detection. At low energies, collisional processes limit the angular resolution and conversion efficiencies of these devices. However, if the intense ultraviolet light background can be suppressed, direct LENA detection is possible. We present results from a series of experiments designed to develop a novel filtering structure based on free-standing transmission gratings. If the grating period is sufficiently small, free standing transmission gratings can be employed to substantially polarize ultraviolet (UV) light in the wavelength range 300 [Angstrom] to 1500 [Angstrom]. If a second grating is placed behind the first grating with its axis of polarization oriented at a right angle to the first's, a substantial attenuation of UV radiation is achievable. ne neutrals will pass through the remaining open area of two gratings and be detected without UV background complications. We have obtained nominal 2000 [Angstrom] period (1000 [Angstrom] bars with 1000 [Angstrom] slits) free standing, gold transmission gratings and measured their UV and atomic transmission characteristics. The geometric factor of a LENA imager based on this technology is comparable to that of other proposed LENA imagers. In addition, this of imager does not distort the neutral trajectories, allowing for high angular resolution.

  20. Colorado School of Mines low energy nuclear physics project

    SciTech Connect

    Cecil, F.E.

    1991-01-02

    A major accomplishment of this project in the past year is the completion of a fairly comprehensive paper describing the survey of radiative capture reactions of protons on light nuclei at low energies. In addition we have completed a preliminary set of measurements of (d,p)/(d,{alpha}) cross section ratios on the charge symmetric nuclei {sup 6}Li and {sup 10}B as a test of the Oppenheimer-Phillips effect. While the {sup 6}Li data remain inconclusive, the {sup 10}B data show solid evidence for the Oppenheimer-Phillips enhancement of the (d,p) reaction relative to the (d,{alpha}) reaction for deuteron bombarding energies below about 100 keV. We have continued our investigation of fusion reaction products from deuterium-metal systems at room temperatures with the startling observation of intense burst of energetic charged particles from deuterium gas loaded thin titaium foils subject to non-equilibrium thermal and electrical conditions. We have completed two projects involving the application of the low energy particle accelerator to material science problems; firstly a study of the transformation of crystalline to amorphous Fe-Zr systems by proton irradiation and secondly the effects of ion bombardment on the critical temperature of YBCO high-temperature superconductors. Finally we have made progress in several instrumentation projects which will be used in some of the up-coming measurements of nuclear cross sections at very low energies.

  1. The MAJORANA Demonstrator Low-Energy Rare Event Search

    NASA Astrophysics Data System (ADS)

    Wiseman, Clinton; Majorana Collaboration

    2016-09-01

    The extremely low backgrounds of the MAJORANA DEMONSTRATOR neutrinoless double beta decay experiment, combined with the excellent energy resolution of its high-purity germanium (HPGe) detectors, provide an opportunity for a dark matter search at low energy (<100 keV). The DEMONSTRATOR is in the final stages of construction at the 4850-ft. level of the Sanford Underground Research Facility in Lead, SD. The first detector module, consisting of 16.8 kg of HPGe enriched to 88% 76Ge and 5.7 kg of natural HPGe, took 100.6 live days of commissioning data before going blind on April 14th, 2016, and the second module is nearing completion at the time of this writing. The enriched detectors have particularly low levels of cosmogenic activation from their specialized manufacturing process. These ultra-low background designs are suited to rare event searches at low energies, including light WIMPs (<10 GeV/c2) and solar axions. In this talk an update of the MAJORANA low-energy research program will be presented. This material is based upon work supported by the U.S. DOE, Office of Science, Office of Nuclear Physics, the Particle Astrophysics and Nuclear Physics Programs of the National Science Foundation, and the Sanford Underground Research Facility.

  2. Low energy description of quantum gravity and complementarity

    NASA Astrophysics Data System (ADS)

    Nomura, Yasunori; Varela, Jaime; Weinberg, Sean J.

    2014-06-01

    We consider a framework in which low energy dynamics of quantum gravity is described preserving locality, and yet taking into account the effects that are not captured by the naive global spacetime picture, e.g. those associated with black hole complementarity. Our framework employs a "special relativistic" description of gravity; specifically, gravity is treated as a force measured by the observer tied to the coordinate system associated with a freely falling local Lorentz frame. We identify, in simple cases, regions of spacetime in which low energy local descriptions are applicable as viewed from the freely falling frame; in particular, we identify a surface called the gravitational observer horizon on which the local proper acceleration measured in the observer's coordinates becomes the cutoff (string) scale. This allows for separating between the "low-energy" local physics and "trans-Planckian" intrinsically quantum gravitational (stringy) physics, and allows for developing physical pictures of the origins of various effects. We explore the structure of the Hilbert space in which the proposed scheme is realized in a simple manner, and classify its elements according to certain horizons they possess. We also discuss implications of our framework on the firewall problem. We conjecture that the complementarity picture may persist due to properties of trans-Planckian physics.

  3. An ion beam deceleration lens for ultra-low-energy ion bombardment of naked DNA

    NASA Astrophysics Data System (ADS)

    Thopan, P.; Prakrajang, K.; Thongkumkoon, P.; Suwannakachorn, D.; Yu, L. D.

    2013-07-01

    Study of low-energy ion bombardment effect on biological living materials is of significance. High-energy ion beam irradiation of biological materials such as organs and cells has no doubt biological effects. However, ion energy deposition in the ion-bombarded materials dominantly occurs in the low-energy range. To investigate effects from very-low-energy ion bombardment on biological materials, an ion beam deceleration lens is necessary for uniform ion energy lower than keV. A deceleration lens was designed and constructed based on study of the beam optics using the SIMION program. The lens consisted of six electrodes, able to focus and decelerate primary ion beam, with the last one being a long tube to obtain a parallel uniform exiting beam. The deceleration lens was installed to our 30-kV bioengineering-specialized ion beam line. The final decelerated-ion energy was measured using a simple electrostatic field to bend the beam to range from 10 eV to 1 keV controlled by the lens parameters and the primary beam condition. In a preliminary test, nitrogen ion beam at 60 eV decelerated from a primary 20-keV beam bombarded naked plasmid DNA. The original DNA supercoiled form was found to change to relaxed and linear forms, indicating single or double strand breaks. The study demonstrated that the ion bombardment with energy as low as several-tens eV was possible to break DNA strands and thus potential to cause genetic modification of biological cells.

  4. A low-energy-consumption electroactive valveless hydrogel micropump for long-term biomedical applications.

    PubMed

    Kwon, Gu Han; Jeong, Gi Seok; Park, Joong Yull; Moon, Jin Hee; Lee, Sang-Hoon

    2011-09-07

    Stimuli-responsive hydrogels have attracted considerable interest in the field of microfluidics due to their ability to transform electrical energy directly into mechanical work through swelling, bending, and other deformations. In particular, electroactive hydrogels hold great promise for biomedical micropumping applications such as implantable drug delivery systems. In such applications, energy consumption rate and durability are key properties. Here, we developed a valveless micropump system that utilizes a hydrogel as the main actuator, and tested its performance over 6 months of continuous operation. The proposed micropump system, powered by a single 1.5 V commercial battery, expended very little energy (less than 750 μWs per stroke) while pumping 0.9 wt% saline solution under a low voltage (less than 1 V), and remained fully functional after 6 months. CFD simulations were conducted to improve the microchannel geometry so as to minimize the backflow caused by the valveless mechanism of the system. Based on the simulation results, an asymmetric geometry and a stop post were introduced to enhance the pumping performance. To demonstrate the feasibility of the proposed system as a drug delivery pump, an anti-cancer drug (adriamycin) was perfused to human breast cancer cells (MCF-7) using the pump. The present study showed that the proposed system can operate continuously for long periods with low energy consumption, powered by a single 1.5 V battery, making it a promising candidate for an implantable drug delivery system.

  5. High-flux source of low-energy neutral beams using reflection of ions from metals

    NASA Technical Reports Server (NTRS)

    Cuthbertson, John W.; Motley, Robert W.; Langer, William D.

    1992-01-01

    Reflection of low-energy ions from surfaces can be applied as a method of producing high-flux beams of low-energy neutral particles, and is an important effect in several areas of plasma technology, such as in the edge region of fusion devices. We have developed a beam source based on acceleration and reflection of ions from a magnetically confined coaxial RF plasma source. The beam provides a large enough flux to allow the energy distribution of the reflected neutrals to be measured despite the inefficiency of detection, by means of an electrostatic cylindrical mirror analyzer coupled with a quadrupole mass spectrometer. Energy distributions have been measured for oxygen, nitrogen, and inert gas ions incident with from 15 to 70 eV reflected from amorphous metal surfaces of several compositions. For ions of lighter atomic mass than the reflecting metal, reflected beams have peaked energy distributions; beams with the peak at 4-32 eV have been measured. The energy and mass dependences of the energy distributions as well as measurements of absolute flux, and angular distribution and divergence are reported. Applications of the neutral beams produced are described.

  6. Influence of the residual oxygen in the plasma immersion ion implantation (PI3) processing of materials

    NASA Astrophysics Data System (ADS)

    Ueda, M.; Silva, A. R.; Mello, Carina B.; Silva, G.; Reuther, H.; Oliveira, V. S.

    2011-12-01

    In this work, we investigated the effects of the contaminants present in the vacuum chamber of the PI3 system, in particular, the residual oxygen, which results in the formation of the oxide compounds on the surface and hence is responsible for the high implantation energies required to achieve reasonably thick treated layers. We used a mass spectrometer (RGA) with a quadruple filter to verify the composition of the residual vacuum and pressure of the elements present in the chamber. Initially we found a high proportion of residual oxygen in a vacuum with a pressure of 1 × 10 -3 Pa. Minimizing the residual oxygen percentage in about 80%, by efficient cleaning of the chamber walls and by improving the gas feeding process, we mitigated the formation of oxides during the PI3 process. Therefore we achieved a highly efficient PI3 processing obtaining implanted layers reaching about 50 nm, even in cases such as an aluminum alloy, where is very difficult to nitrogen implant at low energies. We performed nitrogen PI3 treatment of SS304 and Al7075 using pulses of only 3 kV and 15 × 10 -6 s at 1 kHz with an operating pressure of 1 Pa.

  7. Improvement of early cell adhesion on Thai silk fibroin surface by low energy plasma.

    PubMed

    Amornsudthiwat, Phakdee; Mongkolnavin, Rattachat; Kanokpanont, Sorada; Panpranot, Joongjai; Wong, Chiow San; Damrongsakkul, Siriporn

    2013-11-01

    Low energy plasma has been introduced to treat the surface of Thai silk fibroin which should be enhanced for cell adhesion due to its native hydrophobic surface. Plasma surface treatment could introduce desirable hydrophilic functionalities on the surface without using any chemicals. In this work, nitrogen glow discharge plasma was generated by a low energy AC50Hz power supply system. The plasma operating conditions were optimized to reach the highest nitrogen active species by using optical emission spectroscopy. X-ray photoelectron spectroscopy (XPS) revealed that amine, hydroxyl, ether, and carboxyl groups were induced on Thai silk fibroin surface after plasma treatment. The results on Fourier transform infrared attenuated total reflection (FTIR-ATR) spectroscopy confirmed that the plasma treated effects were only on the outermost layer since there was no change in the bulk chemistry. The surface topography was insignificantly changed from the detection with atomic force microscopy (AFM). The plasma-treated effects were the improved surface wettability and cell adhesion. After a 90-s treatment, the water contact angle was at 20°, while the untreated surface was at 70°. The early cell adhesion of L929 mouse fibroblast was accelerated. L929 cells only took 3h to reach 100% cell adhesion on 90 s N2 plasma-treated surface, while there was less than 50% cell adhesion on the untreated Thai silk fibroin surface after 6h of culture. The cell adhesion results were in agreement with the cytoskeleton development. L929 F-actin was more evident on 90 s N2 plasma-treated surface than others. It could be concluded that a lower energy AC50Hz plasma system enhanced early L929 mouse fibroblast adhesion on Thai silk fibroin surface without any significant change in surface topography and bulk chemistry.

  8. Developing effective rockfall protection barriers for low energy impacts

    NASA Astrophysics Data System (ADS)

    Mentani, Alessio; Giacomini, Anna; Buzzi, Olivier; Govoni, Laura; Gottardi, Guido; Fityus, Stephen

    2016-04-01

    Recently, important progresses have been made towards the development of high capacity rockfall barriers (100 kJ - 8000 kJ). The interest of researchers and practitioners is now turning to the development of fences of minor capacity, whose use becomes essential in areas where rockfall events generally have low intensity and the use of high capacity barriers would be accompanied by excessive costs and high environmental impact. Low energy barriers can also provide a cost-effective solution even in areas where high energies events are expected. Results of full-scale tests are vital to any investigation on the behaviour of these structures. An experimental set-up has been developed at The University of Newcastle (AUS), to investigate the response of low energy rockfall barrier prototypes to low energy impacts. The Australian territory, and in particular New South Wales, is in fact characterised by rockfall events of low-to-medium intensity (50 kJ - 500 kJ) and the need of protection structures working within such energy range, is particularly felt [1]. The experiments involved the impact of a test block onto three spans, low energy barrier prototypes, made of steel structural posts, fully fixed at the base, side cables and a steel meshwork constituted by a double twist hexagonal wire net [2]. Test data enabled the development, calibration and assessment of FE models [3], on which non-linear and dynamic analyses have been performed addressing the effect of the block size. Results have shown that the response of the structure is strongly governed by the net. Data from tests conducted on the sole net and on the entire barrier showed in fact a similar trend, different to what typically observed for high capacity barriers, whose behaviour is also led by the presence of uphill cables and brakes. In particular, the numerical analyses have demonstrated a dependence of the net performance on the block size. In particular, a loss of capacity in the order of 50% occurred as the

  9. Low Energy Electrons in the Mars Plasma Environment

    NASA Technical Reports Server (NTRS)

    Link, Richard

    2001-01-01

    The ionosphere of Mars is rather poorly understood. The only direct measurements were performed by the Viking 1 and 2 landers in 1976, both of which carried a Retarding Potential Analyzer. The RPA was designed to measure ion properties during the descent, although electron fluxes were estimated from changes in the ion currents. Using these derived low-energy electron fluxes, Mantas and Hanson studied the photoelectron and the solar wind electron interactions with the atmosphere and ionosphere of Mars. Unanswered questions remain regarding the origin of the low-energy electron fluxes in the vicinity of the Mars plasma boundary. Crider, in an analysis of Mars Global Surveyor Magnetometer/Electron Reflectometer measurements, has attributed the formation of the magnetic pile-up boundary to electron impact ionization of exospheric neutral species by solar wind electrons. However, the role of photoelectrons escaping from the lower ionosphere was not determined. In the proposed work, we will examine the role of solar wind and ionospheric photoelectrons in producing ionization in the upper ionosphere of Mars. Low-energy (< 4 keV) electrons will be modeled using the two-stream electron transport code of Link. The code models both external (solar wind) and internal (photoelectron) sources of ionization, and accounts for Auger electron production. The code will be used to analyze Mars Global Surveyor measurements of solar wind and photoelectrons down to altitudes below 200 km in the Mars ionosphere, in order to determine the relative roles of solar wind and escaping photoelectrons in maintaining plasma densities in the region of the Mars plasma boundary.

  10. Low-energy lunar transfers using spatial transit orbits

    NASA Astrophysics Data System (ADS)

    Ren, Yuan; Shan, Jinjun

    2014-03-01

    This paper is concerned with natural and artificial low-energy lunar transfers in three-dimensional space. The main contribution of this paper is that the limitations of the planar manifold assumption, which is adopted in previous low-energy orbit design methods, are avoided by describing the transfer orbits with more realistic spatial transit and non-transit orbits. To start, the limitations of the previous design methods for the low-energy trajectories are highlighted, and the boundaries of the spatial transit orbits, which can enter into or escape from the potential well near the Moon through the L1 or L2 bottleneck regions of the zero velocity surface, are defined on a Poincaré section by using the necessary and sufficient condition of transition. Next, by considering the dominant gravity bodies in different orbit segments the motion near the Moon is analyzed in the Earth-Moon circular restricted three-body problem (CR3BP). For natural celestial bodies, the statistical characteristics of the lunar collision trajectories are studied. For the artificial celestial bodies, the investigation is focused on the achievable range of inclination and height of the low lunar orbit (LLO). Then, the motion between the Earth and the Moon is studied in the Earth-Moon based Sun-perturbed bicircular four-body problem (B4BP). For natural and artificial celestial bodies, the Earth-origin trajectories and the trajectories from the low Earth orbits are analyzed. Compared to the current planar manifold based design methods, the technique introduced in this paper can evaluate the lunar transfer orbits more accurately. Also, some lunar transfer trajectories which do not exist in the manifold based models can be found, and the heights and inclinations of the parking orbits around the Earth and the Moon can also be analyzed.

  11. Low-energy tetrahedral polymorphs of carbon, silicon, and germanium

    NASA Astrophysics Data System (ADS)

    Mujica, Andrés; Pickard, Chris J.; Needs, Richard J.

    2015-06-01

    Searches for low-energy tetrahedral polymorphs of carbon and silicon have been performed using density functional theory computations and the ab initio random structure searching approach. Several of the hypothetical phases obtained in our searches have enthalpies that are lower or comparable to those of other polymorphs of group 14 elements that have either been experimentally synthesized or recently proposed as the structure of unknown phases obtained in experiments, and should thus be considered as particularly interesting candidates. A structure of P b a m symmetry with 24 atoms in the unit cell was found to be a low-energy, low-density metastable polymorph in carbon, silicon, and germanium. In silicon, P b a m is found to have a direct band gap at the zone center with an estimated value of 1.4 eV, which suggests applications as a photovoltaic material. We have also found a low-energy chiral framework structure of P 41212 symmetry with 20 atoms per cell containing fivefold spirals of atoms, whose projected topology is that of the so-called Cairo-type two-dimensional pentagonal tiling. We suggest that P 41212 is a likely candidate for the structure of the unknown phase XIII of silicon. We discuss P b a m and P 41212 in detail, contrasting their energetics and structures with those of other group 14 elements, particularly the recently proposed P 42/n c m structure, for which we also provide a detailed interpretation as a network of tilted diamondlike tetrahedra.

  12. Method and apparatus for generating low energy nuclear particles

    DOEpatents

    Powell, J.R.; Reich, M.; Ludewig, H.; Todosow, M.

    1999-02-09

    A particle accelerator generates an input particle beam having an initial energy level above a threshold for generating secondary nuclear particles. A thin target is rotated in the path of the input beam for undergoing nuclear reactions to generate the secondary particles and correspondingly decrease energy of the input beam to about the threshold. The target produces low energy secondary particles and is effectively cooled by radiation and conduction. A neutron scatterer and a neutron filter are also used for preferentially degrading the secondary particles into a lower energy range if desired. 18 figs.

  13. Method and apparatus for generating low energy nuclear particles

    DOEpatents

    Powell, James R.; Reich, Morris; Ludewig, Hans; Todosow, Michael

    1999-02-09

    A particle accelerator (12) generates an input particle beam having an initial energy level above a threshold for generating secondary nuclear particles. A thin target (14) is rotated in the path of the input beam for undergoing nuclear reactions to generate the secondary particles and correspondingly decrease energy of the input beam to about the threshold. The target (14) produces low energy secondary particles and is effectively cooled by radiation and conduction. A neutron scatterer (44) and a neutron filter (42) are also used for preferentially degrading the secondary particles into a lower energy range if desired.

  14. HgI2 low energy beta particle detector

    NASA Technical Reports Server (NTRS)

    Shah, K. S.; Squillante, M. R.; Entine, G.

    1990-01-01

    An HgI2 device structure was designed and tested which allows HgI2 to be used to make low-energy beta-particle detectors. The devices detected tritium beta particles with an efficiency of about 25 percent. A protective encapsulant has been developed which should protect the devices for up to 20 years and will attenuate only a small fraction of the beta particles. It is noted that the devices hold significant promise to provide a practical alternative to liquid scintillation counters and gas flow-through proportional counters.

  15. Low-energy scattering of electrons and positrons in liquids

    NASA Technical Reports Server (NTRS)

    Schrader, D. M.

    1990-01-01

    The scattering of low energy electrons and positrons is described for the liquid phase and compared and contrasted with that for the gas phase. Similarities as well as differences are noted. The loci of scattering sites, called spurs in the liquid phase, are considered in detail. In particular, their temporal and spatial evolution is considered from the point of view of scattering. Two emphases are made: one upon the stochastic calculation of the distribution of distances required for slowing down to thermal velocities, and the other upon the calculation of cross sections for energy loss by means of quantum mechanics.

  16. Study on electron beam in a low energy plasma focus

    SciTech Connect

    Khan, Muhammad Zubair; Ling, Yap Seong; San, Wong Chiow

    2014-03-05

    Electron beam emission was investigated in a low energy plasma focus device (2.2 kJ) using copper hollow anode. Faraday cup was used to estimate the energy of the electron beam. XR100CR X-ray spectrometer was used to explore the impact of the electron beam on the target observed from top-on and side-on position. Experiments were carried out at optimized pressure of argon gas. The impact of electron beam is exceptionally notable with two different approaches using lead target inside hollow anode in our plasma focus device.

  17. Development of multichannel low-energy neutron spectrometer

    SciTech Connect

    Arikawa, Y. Nagai, T.; Abe, Y.; Kojima, S.; Sakata, S.; Inoue, H.; Utsugi, M.; Iwasa, Y.; Sarukura, N.; Nakai, M.; Shiraga, H.; Fujioka, S.; Azechi, H.; Murata, T.

    2014-11-15

    A multichannel low-energy neutron spectrometer for down-scattered neutron (DSN) measurements in inertial confinement fusion (ICF) experiments has been developed. Our compact-size 256-channel lithium-glass-scintillator-based spectrometer has been implemented and tested in ICF experiments with the GEKKO XII laser. We have performed time calibration of the 256-channel analog-to-digital convertor system used for DSN measurements via X-ray pulse signals. We have clearly observed the DD-primary fusion neutron signal and have successfully studied the detector's impulse response. Our detector is soon to be implemented in future ICF experiments.

  18. Wavelet modulation: An alternative modulation with low energy consumption

    NASA Astrophysics Data System (ADS)

    Chafii, Marwa; Palicot, Jacques; Gribonval, Rémi

    2017-02-01

    This paper presents wavelet modulation, based on the discrete wavelet transform, as an alternative modulation with low energy consumption. The transmitted signal has low envelope variations, which induces a good efficiency for the power amplifier. Wavelet modulation is analyzed and compared for different wavelet families with orthogonal frequency division multiplexing (OFDM) in terms of peak-to-average power ratio (PAPR), power spectral density (PSD) properties, and the impact of the power amplifier on the spectral regrowth. The performance in terms of bit error rate and complexity of implementation are also evaluated, and several trade-offs are characterized. xml:lang="fr"

  19. The Compton-Getting effect for low energy particles

    NASA Technical Reports Server (NTRS)

    Ipavich, F. M.

    1974-01-01

    It was found that the traditional first-order Compton-Getting effect, which relates particle distributions as observed in two frames of reference moving with constant relative velocity, is inadequate for the description of low energy particles (less than a few hundred keV/nucleon) in the solar system. An exact procedure is given for recovering both isotropic and anisotropic distributions in the solar wind frame from observations made in a spacecraft frame. The method was illustrated by analyzing a particle event observed on IPM-7.

  20. Low-energy K- optical potentials: deep or shallow?

    NASA Astrophysics Data System (ADS)

    Cieplý, A.; Friedman, E.; Gal, A.; Mareš, J.

    2001-12-01

    The K- optical potential in the nuclear medium is evaluated self consistently from a free-space K-Nt matrix constructed within a coupled-channel chiral approach. The fit of model parameters gives a good description of the low-energy data plus the available K- atomic data. The resulting optical potential is relatively `shallow' in contradiction to the potentials obtained from phenomenological analysis. The calculated (Kstop-,π) hypernuclear production rates are very sensitive to the details of kaonic bound state wave function. The (Kstop-,π) reaction could thus serve as a suitable tool to distinguish between shallow and deep K- optical potentials.

  1. Low Energy Charged Particle Measurement by Japanese Lunar Orbiter SELENE

    NASA Astrophysics Data System (ADS)

    Saito, Y.; Yokota, S.; Asamura, K.; Mukai, T.

    2004-12-01

    SELENE (SELenological and Engineering satellite) is a Japanese lunar orbiter that will be launched in 2006. The main purpose of this satellite is to study the origin and evolution of the moon by means of global mapping of element abundances, mineralogical composition, and surface geographical mapping from 100km altitude. PACE (Plasma energy Angle and Composition Experiment) is one of the scientific instruments onboard the SELENE satellite. PACE consists of 4 sensors: ESA (Electron Spectrum Analyzer)-S1, ESA-S2, IMA (Ion Mass Analyzer), and IEA (Ion Energy Analyzer). ESA-S1 and S2 measure three-dimensional distribution function of low energy electrons below 17keV. ESA basically employs a method of a top hat electrostatic analyzer with angular scanning deflectors at the entrance and toroidal electrodes inside. IMA and IEA measure the three-dimensional distribution function of low energy ions below 28keV/q. IMA has an ability to discriminate the ion mass with high mass resolution. IMA consists of an energy analyzer that is basically the same as ESA and an LEF (Linear Electric Field) TOF (Time Of Flight) ion mass analyzer. IEA consists of only an energy analyzer that is the same as the energy analyzer of IMA. Each sensor has hemi-spherical field of view (FOV). With two pairs of sensors ESA-S1 & IMA, and ESA-S2 & IEA, which are installed on the +Z and -Z surface of the spacecraft, three-dimensional distribution function of low energy electrons and ions are observed. The scientific objectives of PACE are 1) to measure the ions sputtered from the lunar surface and the lunar atmosphere, 2) to measure the magnetic anomaly on the lunar surface using two ESAs and a magnetometer onboard SELENE simultaneously as an electron reflectometer, 3) to resolve the moon - solar wind interaction, 4) to resolve the moon - Earth's magnetosphere interaction, and 5) to observe the Earth's magnetotail. Sputtered ions from the lunar surface will be measured for the first time. Recently, ground

  2. Dynamics of Low Energy Electron Attachment to Formic Acid

    SciTech Connect

    Rescigno, Thomas N.; Trevisan, Cynthia S.; Orel, Ann E.

    2006-04-03

    Low-energy electrons (<2 eV) can fragment gas phaseformic acid (HCOOH) molecules through resonant dissociative attachmentprocesses. Recent experiments have shown that the principal reactionproducts of such collisions are formate ions (HCOO-) and hydrogen atoms.Using first-principles electron scattering calculations, we haveidentified the responsible negative ion state as a transient \\pi* anion.Symmetry considerations dictate that the associated dissociation dynamicsare intrinsically polyatomic: a second anion surface, connected to thefirst by a conical intersection, is involved in the dynamics and thetransient anion must necessarily deform to non-planar geometries beforeit can dissociate to the observed stable products.

  3. Targeting Low-Energy Transfers to Low Lunar Orbit

    NASA Technical Reports Server (NTRS)

    Parker, Jeffrey S.; Anderson, Rodney L.

    2011-01-01

    A targeting scheme is presented to build trajectories from a specified Earth parking orbit to a specified low lunar orbit via a low-energy transfer and up to two maneuvers. The total transfer delta V (velocity) is characterized as a function of the Earth parking orbit inclination and the departure date for transfers to each given low lunar orbit. The transfer delta V (velocity) cost is characterized for transfers constructed to low lunar polar orbits with any longitude of ascending node and for transfers that arrive at the Moon at any given time during a month.

  4. Low energy process of producing gasoline-ethanol mixtures

    SciTech Connect

    Kyle, B.G.

    1981-10-27

    Gasoline-ethanol mixtures useable as motor fuel are produced by a relatively low energy process comprising interrelated distillation and extraction steps. In the first step, aqueous ethanol, such as an ethanol fermentation beer, is subjected to fractional distillation to produce a distillate of at least 75 weight percent ethanol, which is then subjected to extraction with gasoline under conditions producing an extract containing the desired amount of ethanol, such as 8 to 14% by weight. The aqueous phase raffinate from the extraction is returned to the fractionation column for redistillation.

  5. Modelling low energy electron interactions for biomedical uses of radiation

    NASA Astrophysics Data System (ADS)

    Fuss, M.; Muñoz, A.; Oller, J. C.; Blanco, F.; Limão-Vieira, P.; Huerga, C.; Téllez, M.; Hubin-Fraskin, M. J.; Nixon, K.; Brunger, M.; García, G.

    2009-11-01

    Current radiation based medical applications in the field of radiotherapy, radio-diagnostic and radiation protection require modelling single particle interactions at the molecular level. Due to their relevance in radiation damage to biological systems, special attention should be paid to include the effect of low energy secondary electrons. In this study we present a single track simulation procedure for photons and electrons which is based on reliable experimental and theoretical cross section data and the energy loss distribution functions derived from our experiments. The effect of including secondary electron interactions in this model will be discussed.

  6. Low-Energy Hot Plasma and Particles in Saturn's Magnetosphere.

    PubMed

    Krimigis, S M; Armstrong, T P; Axford, W I; Bostrom, C O; Gloeckler, G; Keath, E P; Lanzerotti, L J; Carbary, J F; Hamilton, D C; Roelof, E C

    1982-01-29

    The low-energy charged particle instrument on Voyager 2 measured low-energy electrons and ions (energies greater, similar 22 and greater, similar 28 kiloelectron volts, respectively) in Saturn's magnetosphere. The magnetosphere structure and particle population were modified from those observed during the Voyager 1 encounter in November 1980 but in a manner consistent with the same global morphology. Major results include the following. (i) A region containing an extremely hot ( approximately 30 to 50 kiloelectron volts) plasma was identified and extends from the orbit of Tethys outward past the orbit of Rhea. (ii) The low-energy ion mantle found by Voyager 1 to extend approximately 7 Saturn radii inside the dayside magnetosphere was again observed on Voyager 2, but it was considerably hotter ( approximately 30 kiloelectron volts), and there was an indication of a cooler ( < 20 kiloelectron volts) ion mantle on the nightside. (iii) At energies greater, similar 200 kiloelectron volts per nucleon, H(1), H(2), and H(3) (molecular hydrogen), helium, carbon, and oxygen are important constituents in the Saturnian magnetosphere. The presence of both H(2) and H(3) suggests that the Saturnian ionosphere feeds plasma into the magnetosphere, but relative abundances of the energetic helium, carbon, and oxygen ions are consistent with a solar wind origin. (iv) Low-energy ( approximately 22 to approximately 60 kiloelectron volts) electron flux enhancements observed between the L shells of Rhea and Tethys by Voyager 2 on the dayside were absent during the Voyager 1 encounter. (v) Persistent asymmetric pitch-angle distributions of electrons of 60 to 200 kiloelectron volts occur in the outer magnetosphere in conjunction with the hot ion plasma torus. (vi) The spacecraft passed within approximately 1.1 degrees in longitude of the Tethys flux tube outbound and observed it to be empty of energetic ions and electrons; the microsignature of Enceladus inbound was also observed. (vii

  7. Low energy sputtering of cobalt by cesium ions

    NASA Technical Reports Server (NTRS)

    Handoo, A.; Ray, Pradosh K.

    1989-01-01

    An experimental facility to investigate low energy (less than 500 eV) sputtering of metal surfaces with ions produced by an ion gun is described. Results are reported on the sputtering yield of cobalt by cesium ions in the 100 to 500 eV energy range at a pressure of 1 times 10(exp -6) Torr. The target was electroplated on a copper substrate. The sputtered atoms were collected on a cobalt foil surrounding the target. Co-57 was used as a tracer to determine the sputtering yield.

  8. Low Energy Continuum and Lattice Effective Field Theories

    NASA Astrophysics Data System (ADS)

    Elhatisari, Serdar

    In this thesis we investigate several constraints and their impacts on the short-range potentials in the low-energy limits of quantum mechanics.We also present lattice Monte Carlo calculations using the adiabatic projection method. In the first part we consider the constraints of causality and unitarity for the low-energy interactions of particles. We generalize Wigner's causality bound to the case of non-vanishing partial-wave mixing. Specifically we analyze the system of the low-energy interactions between protons and neutrons. We derive a general theorem that non-vanishing partial-wave mixing cannot be reproduced with zero-range interactions without violating causality or unitarity. We also analyze low-energy scattering for systems with arbitrary short-range interactions plus an attractive 1/ralpha tail for alpha ≥ 2. In particular, we focus on the case of alpha = 6 and we derive the constraints of causality and unitarity also for these systems and find that the van derWaals length scale dominates over parameters characterizing the short-distance physics of the interaction. This separation of scales suggests a separate universality class for physics characterizing interactions with an attractive 1{r6 tail. We argue that a similar universality class exists for any attractive potential 1/ralpha for alpha ≥ 2. In the second part of the thesis we present lattice Monte Carlo calculations of fermion-dimer scattering in the limit of zero-range interactions using the adiabatic projection method. The adiabatic projection method uses a set of initial cluster states and Euclidean time projection to give a systematically improvable description of the low-lying scattering cluster states in a finite volume. We use Luscher's finite-volume relations to determine the s-wave, p-wave, and d-wave phase shifts. For comparison, we also compute exact lattice results using Lanczos iteration and continuum results using the Skorniakov-Ter-Martirosian equation. For our Monte Carlo

  9. A Mutant of Bacillus Subtilis with High-Producing Surfactin by Ion Beam Implantation

    NASA Astrophysics Data System (ADS)

    Liu, Qingmei; Yuan, Hang; Wang, Jun; Gong, Guohong; Zhou, Wei; Fan, Yonghong; Wang, Li; Yao, Jianming; Yu, Zengliang

    2006-07-01

    In order to generate a mutant of Bacillus subtilis with enhanced surface activity through low energy nitrogen ion beam implantation, the effects of energy and dose of ions implanted were studied. The morphological changes in the bacteria were observed by scanning electron microscope (SEM). The optimum condition of ions implantation, 20 keV of energy and 2.6×1015N+/cm2 in dose, was determined. A mutant, B.s-E-8 was obtained, whose surface activity of 50-fold and 100-fold diluted cell-free Landy medium was as 5.6-fold and 17.4-fold as the wild strain. The microbial growth and biosurfactant production of both the mutant and the wild strain were compared. After purified by ultrafiltration and SOURCE 15PHE, the biosurfactant was determined to be a complex of surfactin family through analysis of electrospray ionization mass spectrum (ESI/MS) and there was an interesting finding that after the ion beam implantation the intensities of the components were different from the wild type strain.

  10. Materials for Low-Energy Neutron Radiation Shielding

    NASA Technical Reports Server (NTRS)

    Singleterry, Robert C., Jr.; Thibeault, Sheila A.

    2000-01-01

    Various candidate aircraft and spacecraft materials were analyzed and compared in a low-energy neutron environment using the Monte Carlo N-Particle (MCNP) transport code with an energy range up to 20 MeV. Some candidate materials have been tested in particle beams, and others seemed reasonable to analyze in this manner before deciding to test them. The two metal alloys analyzed are actual materials being designed into or used in aircraft and spacecraft today. This analysis shows that hydrogen-bearing materials have the best shielding characteristics over the metal alloys. It also shows that neutrons above 1 MeV are reflected out of the face of the slab better by larger quantities of carbon in the material. If a low-energy absorber is added to the material, fewer neutrons are transmitted through the material. Future analyses should focus on combinations of scatterers and absorbers to optimize these reaction channels and on the higher energy neutron component (above 50 MeV).

  11. Response of plastic scintillators to low-energy photons.

    PubMed

    Peralta, Luis; Rêgo, Florbela

    2014-08-21

    Diagnostic radiology typically uses x-ray beams between 25 and 150 kVp. Plastic scintillation detectors (PSDs) are potentially successful candidates as field dosimeters but careful selection of the scintillator is crucial. It has been demonstrated that they can suffer from energy dependence in the low-energy region, an undesirable dosimeter characteristic. This dependence is partially due to the nonlinear light yield of the scintillator to the low-energy electrons set in motion by the photon beam. In this work, PSDs made of PMMA, PVT or polystyrene were studied for the x-ray beam range 25 to 100 kVp. For each kVp data has been acquired for additional aluminium filtrations of 0.5, 1.0, 2.0 and 4.0 mm. Absolute dose in the point of measurement was obtained with an ionization chamber calibrated to dose in water. From the collected data, detector sensitivities were obtained as function of the beam kVp and additional filtration. Using Monte Carlo simulations relative scintillator sensitivities were computed. For some of the scintillators these sensitivities show strong energy-dependence for beam average energy below 35 keV for each additional filtration but fair constancy above. One of the scintillators (BC-404) has smaller energy-dependence at low photon average energy and could be considered a candidate for applications (like mammography) where beam energy has small span.

  12. MARLEY: Model of Argon Reaction Low Energy Yields

    NASA Astrophysics Data System (ADS)

    Gardiner, Steven; Bilton, Kyle; Grant, Christopher; Pantic, Emilija; Svoboda, Robert

    2015-10-01

    Core-collapse supernovae are sources of tremendous numbers of neutrinos with energies of up to about 50 MeV. In recent years, there has been growing interest in building detectors that are sensitive to supernova neutrinos. Such detectors can provide information about the initial stages of stellar collapse, early warning signals for light emission from supernovae, and opportunities to study neutrino oscillation physics over astronomical distances. In an effort to enable supernova neutrino detection in next-generation experiments like DUNE, the CAPTAIN collaboration plans to make the first direct measurement of cross sections for neutrino interactions on argon in the supernova energy regime. To help predict neutrino event signatures in the CAPTAIN liquid argon time projection chamber (LArTPC), we have developed a first-of-its-kind Monte Carlo event generator called MARLEY (Model of Argon Reaction Low Energy Yields). This generator attempts to model the complicated nuclear structure dependence of low-energy neutrino-nucleus reactions in sufficient detail for use in LArTPC simulations. In this talk we present some preliminary results calculated using MARLEY and discuss how the current version of the generator may be improved and expanded.

  13. Development of Low Energy Gap and Fully Regioregular Polythienylenevinylene Derivative

    DOE PAGES

    David, Tanya M. S.; Zhang, Cheng; Sun, Sam-Shajing

    2014-01-01

    Low energy gap and fully regioregular conjugated polymers find its wide use in solar energy conversion applications. This paper will first briefly review this type of polymers and also report synthesis and characterization of a specific example new polymer, a low energy gap, fully regioregular, terminal functionalized, and processable conjugated polymer poly-(3-dodecyloxy-2,5-thienylene vinylene) or PDDTV. The polymer exhibited an optical energy gap of 1.46 eV based on the UV-vis-NIR absorption spectrum. The electrochemically measured highest occupied molecular orbital (HOMO) level is −4.79 eV, resulting in the lowest unoccupied molecular orbital (LUMO) level of −3.33 eV based on optical energy gap. The polymer wasmore » synthesized via Horner-Emmons condensation and is fairly soluble in common organic solvents such as tetrahydrofuran and chloroform with gentle heating. DSC showed two endothermic peaks at 67°C and 227°C that can be attributed to transitions between crystalline and liquid states. The polymer is thermally stable up to about 300°C. This polymer appears very promising for cost-effective solar cell applications.« less

  14. Low-Energy Electron Scattering by Sugarcane Lignocellulosic Biomass Molecules

    NASA Astrophysics Data System (ADS)

    Oliveira, Eliane; Sanchez, Sergio; Bettega, Marcio; Lima, Marco; Varella, Marcio

    2012-06-01

    The use of second generation (SG) bioethanol instead of fossil fuels could be a good strategy to reduce greenhouse gas emissions. However, the efficient production of SG bioethanol has being a challenge to researchers around the world. The main barrier one must overcome is the pretreatment, a very important step in SG bioethanol aimed at breaking down the biomass and facilitates the extraction of sugars from the biomass. Plasma-based treatment, which can generate reactive species, could be an interesting possibility since involves low-cost atmospheric-pressure plasma. In order to offer theoretical support to this technique, the interaction of low-energy electrons from the plasma with biomass is investigated. This study was motived by several works developed by Sanche et al., in which they understood that DNA damage arises from dissociative electron attachment, a mechanism in which electrons are resonantly trapped by DNA subunits. We will present elastic cross sections for low-energy electron scattering by sugarcane biomass molecules, obtained with the Schwinger multichannel method. Our calculations indicate the formation of π* shape resonances in the lignin subunits, while a series of broad and overlapping σ* resonances are found in cellulose and hemicellulose subunits. The presence of π* and σ* resonances could give rise to direct and indirect dissociation pathways in biomass. Then, theoretical resonance energies can be useful to guide the plasma-based pretreatment to break down specific linkages of interest in biomass.

  15. Neutrino phenomenology of very low-energy seesaw scenarios

    SciTech Connect

    Gouvea, Andre de; Jenkins, James; Vasudevan, Nirmala

    2007-01-01

    The standard model augmented by the presence of gauge-singlet right-handed neutrinos proves to be an ideal scenario for accommodating nonzero neutrino masses. Among the new parameters of this 'new standard model' are right-handed neutrino Majorana masses M. Theoretical prejudice points to M much larger than the electroweak symmetry breaking scale, but it has recently been emphasized that all M values are technically natural and should be explored. Indeed, M around 1-10 eV can accommodate an elegant oscillation solution to the liquid scintillator neutrino detector (LSND) anomaly, while other M values lead to several observable consequences. We consider the phenomenology of low-energy (M < or approx. 1 keV) seesaw scenarios. By exploring such a framework with three right-handed neutrinos, we can consistently fit all oscillation data--including those from LSND--while partially addressing several astrophysical puzzles, including anomalous pulsar kicks, heavy element nucleosynthesis in supernovae, and the existence of warm dark matter. In order to accomplish all of this, we find that a nonstandard cosmological scenario is required. Finally, low-energy seesaws - regardless of their relation to the LSND anomaly - can also be tested by future tritium beta-decay experiments, neutrinoless double-beta decay searches, and other observables. We estimate the sensitivity of such probes to M.

  16. Study of chirally motivated low-energy K - optical potentials

    NASA Astrophysics Data System (ADS)

    Cieplý, A.; Friedman, E.; Gal, A.; Mareš, J.

    2001-12-01

    The K - optical potential in the nuclear medium is evaluated self consistently from a free-space K -N t matrix constructed within a coupled-channel chiral approach to the low-energy K¯N data. The chiral-model parameters are fitted to a select subset of the low-energy data plus the K - atomic data throughout the periodic table. The resulting attractive K - optical potentials are relatively 'shallow', with central depth of the real part about 55 MeV, for a fairly reasonable reproduction of the atomic data with χ2/ N≈2.2. Relatively 'deep' attractive potentials of depth about 180 MeV, which result in other phenomenological approaches with χ2/ N≈1.5, are ruled out within chirally motivated models. Different physical data input is required to distinguish between shallow and deep K - optical potentials. The (K -stop, π) reaction could provide such a test, with exclusive rates differing by over a factor of three for the two classes of potentials. Finally, forward (K -,p) differential cross sections for the production of relatively narrow deeply bound K -nuclear states are evaluated for deep K - optical potentials, yielding values considerably lower than those estimated before.

  17. The low energy detector of Simbol-X

    NASA Astrophysics Data System (ADS)

    Lechner, P.; Andricek, L.; Briel, U.; Hasinger, G.; Heinzinger, K.; Herrmann, S.; Huber, H.; Kendziorra, E.; Lauf, T.; Lutz, G.; Richter, R.; Santangelo, A.; Schaller, G.; Schnecke, M.; Schopper, F.; Segneri, G.; Strüder, L.; Treis, J.

    2008-07-01

    Simbol-X is a French-Italian-German hard energy X-ray mission with a projected launch in 2014. Being sensitive in the energy range from 500 eV to 80 keV it will cover the sensitivity gap beyond the energy interval of today's telescopes XMM-Newton and Chandra. Simbol-X will use an imaging telescope of nested Wolter-I mirrors. To provide a focal length of 20 m it will be the first mission of two independent mirror and detector spacecrafts in autonomous formation flight. The detector spacecraft's payload is composed of an imaging silicon low energy detector in front of a pixelated cadmium-telluride hard energy detector. Both have a sensitive area of 8 × 8 cm2 to cover a 12 arcmin field of view and a pixel size of 625 × 625 μm2 adapted to the telescope's resolution of 20 arcsec. The additional LED specifications are: high energy resolution, high quantum efficiency, fast readout and optional window mode, monolithic device with 100 % fill factor and suspension mounting, and operation at warm temperature. To match these requirements the low energy detector is composed of 'active macro pixels', combining the large, scalable area of a Silicon Drift Detector and the low-noise, on-demand readout of an integrated DEPFET amplifier. Flight representative prototypes have been processed at the MPI semiconductor laboratory, and the prototype's measured performance demonstrates the technology readiness.

  18. Low Energy Charged Particle Measurement by Japanese Lunar Orbiter SELENE

    NASA Astrophysics Data System (ADS)

    Saito, Yu.; Yokota, S.; Asamura, K.; Tanaka, T.; Mukai, T.

    SELenological and ENgineering Explorer (SELENE) is a Japanese lunar orbiter that will be launched in 2007. The main purpose of this satellite is to study the origin and evolution of the Moon by means of global mapping of element abundances, mineralogical composition, and surface geographical mapping from 100 km altitude. Plasma energy Angle and Composition Experiment (PACE) is one of the scientific instruments onboard the SELENE satellite. The scientific objectives of PACE are (1) to measure the ions sputtered from the lunar surface and the lunar atmosphere, (2) to measure the magnetic anomaly on the lunar surface using two electron spectrum analyzers (ESAs) and a magnetometer onboard SELENE simultaneously as an electron reflectometer, (3) to resolve the Moon-solar wind interaction, (4) to resolve the Moon-Earth's magnetosphere interaction, and (5) to observe the Earth's magnetotail. PACE consists of four sensors: ESA-S1, ESA-S2, ion mass analyzer (IMA), and ion energy analyzer (IEA). ESA-S1 and S2 measure the three-dimensional distribution function of low energy electrons below 15 keV, while IMA and IEA measure the three-dimensional distribution function of low energy ions below 28 keV/q.

  19. Cross sections for low-energy inelastic H + Na collisions

    SciTech Connect

    Belyaev, A. K.; Barklem, P. S.; Dickinson, A. S.; Gadea, F. X.

    2010-03-15

    Full quantum-scattering calculations are reported for low-energy near-threshold inelastic collision cross sections for H+Na. The calculations include transitions between all levels up to and including the ionic state (ion-pair production) for collision energies from the threshold up to 10 eV. These results are important for astrophysical modeling of spectra in stellar atmospheres. Results for the 3s-3p excitation are carefully examined using three different quantum chemistry input data sets, and large differences are found near the threshold. The differences are found to be predominantly due to differences in the radial coupling rather than potentials and are also found not to relate to differences in couplings in a simple manner. In fact, of the three input couplings, the two that are most similar give the cross sections with the largest differences. The 3s-3p cross sections show orbiting resonances which have been seen in earlier studies, while Feshbach resonances associated with closed channels were also found to be present in the low-energy cross sections for some transitions.

  20. Formation of a high intensity low energy positron string

    NASA Astrophysics Data System (ADS)

    Donets, E. D.; Donets, E. E.; Syresin, E. M.; Itahashi, T.; Dubinov, A. E.

    2004-05-01

    The possibility of a high intensity low energy positron beam production is discussed. The proposed Positron String Trap (PST) is based on the principles and technology of the Electron String Ion Source (ESIS) developed in JINR during the last decade. A linear version of ESIS has been used successfully for the production of intense highly charged ion beams of various elements. Now the Tubular Electron String Ion Source (TESIS) concept is under study and this opens really new promising possibilities in physics and technology. In this report, we discuss the application of the tubular-type trap for the storage of positrons cooled to the cryogenic temperatures of 0.05 meV. It is intended that the positron flux at the energy of 1-5 eV, produced by the external source, is injected into the Tubular Positron Trap which has a similar construction as the TESIS. Then the low energy positrons are captured in the PST Penning trap and are cooled down because of their synchrotron radiation in the strong (5-10 T) applied magnetic field. It is expected that the proposed PST should permit storing and cooling to cryogenic temperature of up to 5×109 positrons. The accumulated cooled positrons can be used further for various physics applications, for example, antihydrogen production.

  1. Radiative neutralino production in low energy supersymmetric models

    SciTech Connect

    Basu, Rahul; Sharma, Chandradew; Pandita, P. N.

    2008-06-01

    We study the production of the lightest neutralinos in the radiative process e{sup +}e{sup -}{yields}{chi}-tilde{sub 1}{sup 0}{chi}-tilde{sub 1}{sup 0}{gamma} in low energy supersymmetric models for the International Linear Collider energies. This includes the minimal supersymmetric standard model as well as its extension with an additional chiral Higgs singlet superfield, the nonminimal supersymmetric standard model. We compare and contrast the dependence of the signal cross section on the parameters of the neutralino sector of the minimal and nonminimal supersymmetric standard model. We also consider the background to this process coming from the standard model process e{sup +}e{sup -}{yields}{nu}{nu}{gamma}, as well as from the radiative production of the scalar partners of the neutrinos (sneutrinos) e{sup +}e{sup -}{yields}{nu}-tilde{nu}-tilde*{gamma}, which can be a background to the radiative neutralino production when the sneutrinos decay invisibly. In low energy supersymmetric models radiative production of the lightest neutralinos may be the only channel to study supersymmetric partners of the standard model particles at the first stage of a linear collider, since heavier neutralinos, charginos, and sleptons may be too heavy to be pair produced at a e{sup +}e{sup -} machine with {radical}(s)=500 GeV.

  2. Very low energy supernovae and their resulting transients

    NASA Astrophysics Data System (ADS)

    Lovegrove, Elizabeth

    Core-collapse supernovae play a key role in many of astrophysical processes, but the details of how these explosive events work remain elusive. Many questions about the CCSN explosion mechanism and progenitor stars could be answered by either detecting very-low-energy supernovae (VLE SNe) or alternately placing a tight upper bound on their fraction of the CCSN population. However, VLE SNe are by definition dim events. Many VLE SNe result from the failure of the standard CCSN explosion mechanism, meaning that any observable signature must be created by secondary processes either before or during the collapse. In this dissertation I examine alternate means of producing transients in otherwise-failed CCSNe and consider the use of shock breakout flashes to both detect VLE SNe and retrieve progenitor star information. I begin by simulating neutrino-mediated mass loss in CCSNe progenitors to show that a dim, unusual, but still observable transient can be produced. I then simulate shock breakout flashes in VLE SNe for both the purposes of detection as well as extracting information about the exploding star. I discuss particular challenges of modeling shock breakout at low energies and behaviors unique to this regime, in particular the behavior of the spectral temperature. All simulations in this dissertation were done with the CASTRO radiation-hydrodynamic code.

  3. TOPICAL REVIEW: RBE of low energy electrons and photons

    NASA Astrophysics Data System (ADS)

    Nikjoo, Hooshang; Lindborg, Lennart

    2010-05-01

    Relative biological effectiveness (RBE) compares the severity of damage induced by a radiation under test at a dose D relative to the reference radiation Dx for the same biological endpoint. RBE is an important parameter in estimation of risk from exposure to ionizing radiation (IR). The present work provides a review of the recently published data and the knowledge of the RBE of low energy electrons and photons. The review presents RBE values derived from experimental data and model calculations including cell inactivation, chromosome aberration, cell transformation, micronuclei formation and induction of double-strand breaks. Biophysical models, including physical features of radiation track, and microdosimetry parameters are presented, analysed and compared with experimental data. The biological effects of low energy electrons and photons are of particular interest in radiation biology as these are strongly absorbed in micrometer and sub-micrometer layers of tissue. RBE values not only depend on the electron and photon energies but also on the irradiation condition, cell type and experimental conditions.

  4. Low Energy Nuclear Structure Modeling: Can It Be Improved?

    NASA Astrophysics Data System (ADS)

    Stone, Jirina R.

    Since the discovery of the atomic nucleus in 1911 generations of physicists have devoted enormous effort to understand low energy nuclear structure. Properties of nuclei in their ground state, including mass, binding energy and shape, provide vital input to many areas of sub-atomic physics as well as astrophysics and cosmology. Low energy excited states are equally important for understanding nuclear dynamics. Yet, no consensus exists as to what is the best path to a theory which would not only consistently reproduce a wide variety of experimental data but also have enough predictive power to yield credible predictions in areas where data are still missing. In this contribution some of the main obstacles preventing building such a theory are discussed. These include modification of the free nucleon-nucleon force in the nuclear environment and effects of the sub-nucleon (quark) structure of the nucleon. Selected classes of nuclear models, mean-field, shell and ab-initio models are briefly outlined. Finally, suggestions are made for, at least partial, progress that can be achieved with the quark-meson coupling model, as reported in recent publication [1].

  5. Low energy charged particles interacting with amorphous solid water layers

    SciTech Connect

    Horowitz, Yonatan; Asscher, Micha

    2012-04-07

    The interaction of charged particles with condensed water films has been studied extensively in recent years due to its importance in biological systems, ecology as well as interstellar processes. We have studied low energy electrons (3-25 eV) and positive argon ions (55 eV) charging effects on amorphous solid water (ASW) and ice films, 120-1080 ML thick, deposited on ruthenium single crystal under ultrahigh vacuum conditions. Charging the ASW films by both electrons and positive argon ions has been measured using a Kelvin probe for contact potential difference (CPD) detection and found to obey plate capacitor physics. The incoming electrons kinetic energy has defined the maximum measurable CPD values by retarding further impinging electrons. L-defects (shallow traps) are suggested to be populated by the penetrating electrons and stabilize them. Low energy electron transmission measurements (currents of 0.4-1.5 {mu}A) have shown that the maximal and stable CPD values were obtained only after a relatively slow change has been completed within the ASW structure. Once the film has been stabilized, the spontaneous discharge was measured over a period of several hours at 103 {+-} 2 K. Finally, UV laser photo-emission study of the charged films has suggested that the negative charges tend to reside primarily at the ASW-vacuum interface, in good agreement with the known behavior of charged water clusters.

  6. Low Energy Laser Biostimulation: New Prospects For Medical Applications

    NASA Astrophysics Data System (ADS)

    Castel, John C.; Abergel, R. Patrick; Willner, Robert E.; Baumann, James G.

    1987-03-01

    The therapeutic benefits of light-energy is not a new concept to the modern world. Documented applications from ancient times tell of the therapeutic effects of ordinary sun-light to treat such common ailments as painful body joints, wounds, compound fractures and tetanus. The discovery of laser light in the 1960's, opened up new prospects for the medical use of light. Laser light differs from other forms of electromagnetic spectrum in that a single wavelength rather than a spectrum of wavelengths is emitted. Since the early 1970's, low-energy laser radiation has been reported to enhance wound healing rates, reduce edema, and relieve musculoskeletal pain. There is no detectable thermal effect of this laser on the tissue being treated. The effects are considered to occur as a result of photochemical, non thermal effects of the laser beam. Photons are absorbed by the tissue being treated and, in turn, produce positive therapeutic effects such as reduction of pain and edema. Pre-clinical and clinical evaluations are, presently, underway to document the safety and efficacy of low energy laser therapy, which represents a significant advance in the non-invasive treatment of pain.

  7. Low energy probes of PeV scale sfermions

    SciTech Connect

    Altmannshofer, Wolfgang; Harnik, Roni; Zupan, Jure

    2013-11-27

    We derive bounds on squark and slepton masses in mini-split supersymmetry scenario using low energy experiments. In this setup gauginos are at the TeV scale, while sfermions are heavier by a loop factor. We cover the most sensitive low energy probes including electric dipole moments (EDMs), meson oscillations and charged lepton flavor violation (LFV) transitions. A leading log resummation of the large logs of gluino to sfermion mass ratio is performed. A sensitivity to PeV squark masses is obtained at present from kaon mixing measurements. A number of observables, including neutron EDMs, mu->e transitions and charmed meson mixing, will start probing sfermion masses in the 100 TeV-1000 TeV range with the projected improvements in the experimental sensitivities. We also discuss the implications of our results for a variety of models that address the flavor hierarchy of quarks and leptons. We find that EDM searches will be a robust probe of models in which fermion masses are generated radiatively, while LFV searches remain sensitive to simple-texture based flavor models.

  8. Low energy ion beam assisted growth of metal multilayers

    NASA Astrophysics Data System (ADS)

    Quan, Junjie

    Vapor deposited metal multilayers have attracted a great deal of interest in recent years because they offer extraordinary strength, hardness, heat resistance, and unexpected new properties like high reflectivity and spin-dependent conductivity. The giant magnetoresistance effects discovered in Fe/Cr artificial superstructures in 1988 stimulated a large number of studies on the electronic transport properties of spintronic materials because of their important applications in highly sensitive magnetic sensors, nonvolatile random access memories, and the data storage industry in general. Magnetic multilayers allow exploitation of unique micromagnetic, magnetooptic, and magnetoelectronic phenomena that cannot be realized using conventional materials. For example, if ferromagnetic layers (such as CoFe) with a thicknesses of 5-7 nm are separated by a non-magnetic spacer (such as Cu or AlOx) of an appropriate thickness (1-3 nm), they can exhibit large changes in their electrical resistance when a magnetic field is applied. These changes are caused mainly by spin-dependent conduction electron scattering at magnetic multilayer interfaces. Many experimental and theoretical works have sought to promote a basic understanding of the effect of atomic structure in thin film multilayers upon spin dependent transport. It has been found that interfacial imperfections, such as interfacial roughness and interlayer mixing, dramatically reduce the properties exploited for spintronic applications. A combination of computer modeling and experiments has been used to discover more effective ways to control the interfacial structures of metal multilayers. Earlier atomic simulations had indicated that it is very important to control adatom energy during deposition in order to improve interface properties. Based on these ideas, this dissertation has investigated the effects of low energy ion assistance during metal multilayer deposition. Using molecular dynamics modeling, the effects of ion

  9. The low energy spectra of gamma-ray bursts

    NASA Technical Reports Server (NTRS)

    Bussard, R. W.; Lamb, F. K.

    1982-01-01

    The implications of observed gamma-ray burst spectra for the physical conditions and geometries of the sources are examined. It is noted that an explanation of the continua in terms of optically thin thermal bremsstrahlung requires a relatively large area but a fairly shallow depth. On the other hand, a spectrum similar to that observed could be produced by rapid flickering of sources with less extreme geometries if each flicker emits a Comptonized thermal spectrum. Either field inhomogeneities or plasma motions are required to interpret the low energy features as cyclotron extinction. An alternative explanation is photoelectric absorption by heavy atoms; this requires a field strength high enough to make one-photon electron positron annihilation possible. Observational tests of these possibilities are proposed

  10. Theoretical Study of Low Energy Scattering from Metal Nuclei.

    NASA Astrophysics Data System (ADS)

    Gomez, Bernadette; Hira, Ajit; Duran, Joe; Jaramillo, Danelle

    2015-04-01

    We continue our interest in the interactions between different nuclear species with a computational study of the scattering of the low-energy nuclei of H through F atoms (Z <= 9 ) from Silver, Palladium and other metals. Recent work has shown that neutron scattering can be used to record holographic images of materials. We have developed a FORTRAN computer program to compute stopping cross sections and scattering angles in Ag and other metals for the small nuclear projectiles, using Monte Carlo calculation. This code allows for different angles of incidence. Next, simulations were done in the energy interval from 50 to 210 keV. The computational results thus obtained are compared with relevant experimental data. The data are further analyzed to identify periodic trends in terms of the atomic number of the projectile. Such studies have potential applications in nuclear physics and in nuclear medicine.

  11. Low energy electron magnetometer using a monoenergetic electron beam

    NASA Technical Reports Server (NTRS)

    Singh, J. J.; Wood, G. M.; Rayborn, G. H.; White, F. A. (Inventor)

    1983-01-01

    A low energy electron beam magnetometer utilizes near-monoenergetic electrons thereby reducing errors due to electron energy spread and electron nonuniform angular distribution. In a first embodiment, atoms in an atomic beam of an inert gas are excited to a Rydberg state and then electrons of near zero energy are detached from the Rydberg atoms. The near zero energy electrons are then accelerated by an electric field V(acc) to form the electron beam. In a second embodiment, a filament emits electrons into an electrostatic analyzer which selects electrons at a predetermined energy level within a very narrow range. These selected electrons make up the electron beam that is subjected to the magnetic field being measured.

  12. Opportunistic Sensor Data Collection with Bluetooth Low Energy.

    PubMed

    Aguilar, Sergio; Vidal, Rafael; Gomez, Carles

    2017-01-23

    Bluetooth Low Energy (BLE) has gained very high momentum, as witnessed by its widespread presence in smartphones, wearables and other consumer electronics devices. This fact can be leveraged to carry out opportunistic sensor data collection (OSDC) in scenarios where a sensor node cannot communicate with infrastructure nodes. In such cases, a mobile entity (e.g., a pedestrian or a vehicle) equipped with a BLE-enabled device can collect the data obtained by the sensor node when both are within direct communication range. In this paper, we characterize, both analytically and experimentally, the performance and trade-offs of BLE as a technology for OSDC, for the two main identified approaches, and considering the impact of its most crucial configuration parameters. Results show that a BLE sensor node running on a coin cell battery can achieve a lifetime beyond one year while transferring around 10 Mbit/day, in realistic OSDC scenarios.

  13. A New Instrument Design for Imaging Low Energy Neutral Atoms

    NASA Technical Reports Server (NTRS)

    Keller, John W.; Collier, Michael R.; Chornay, Dennis; Rozmarynowski, Paul; Getty, Stephanie; Cooper, John F.; Smith, Billy

    2007-01-01

    The MidSTAR-2 satellite, to be built at the US Naval Academy as a follow-on to the successful MidSTAR-1 satellite (http://web.ew.usna.edu/midstar/), will launch in 2011 and carry three Goddard Space Flight Center (GSFC) experiments developed under Goddard's Internal Research and Development (IRAD) program. One of these GSFC instruments, the Miniature Imager for Neutral Ionospheric atoms and Magnetospheric Electrons (MINI-ME) builds on the heritage of the Goddard-developed Low-Energy Neutral Atom (LENA) imager launched on the IMAGE spacecraft in 2000. MINI-ME features a Venetian-blind conversion surface assembly that improves both light rejection and conversion efficiency in a smaller and lighter package than LENA making this an highly effective instrument for viewing solar wind charge exchange with terrestrial and planetary exospheres. We will describe the MINI-ME prototyping effort and its science targets.

  14. Low-energy structure of four-dimensional superstrings

    SciTech Connect

    Zwirner, F.

    1988-05-01

    The N = 1, d = 4 supergravity theories derived as the low-energy limit of four-dimensional superstrings are discussed, focusing on the properties of their effective potentials. Gauge symmetry breaking is possible along several flat directions. A class of superpotential modifications is introduced, which describes supersymmetry breaking with vanishing cosmological constant and Str M{sup 2} = 0 at any minimum of the tree level potential. Under more restrictive assumptions, there are minima with broken supersymmetry at which also Str f(M{sup 2}) = 0 for any function f, so that the whole one-loop cosmological constant vanishes. This result is interpreted in terms of a new discrete boson-fermion symmetry, relating particles whose helicities differ by 3/2, e.g., the graviton and the dilatino.' 21 refs.

  15. Contamination control and plume assessment of low-energy thrusters

    NASA Technical Reports Server (NTRS)

    Scialdone, John J.

    1993-01-01

    Potential contamination of a spacecraft cryogenic surface by a xenon (Xe) ion generator was evaluated. The analysis involves the description of the plume exhausted from the generator with its relative component fluxes on the spacecraft surfaces, and verification of the conditions for condensation, adsorption, and sputtering at those locations. The data describing the plume fluxes and their effects on surfaces were obtained from two sources: the tests carried out with the Xe generator in a small vacuum chamber to indicate deposits and sputter on monitor slides; and the extensive tests with a mercury (Hg) ion thruster in a large vacuum chamber. The Hg thruster tests provided data on the neutrals, on low-energy ion fluxes, on high-energy ion fluxes, and on sputtered materials at several locations within the plume.

  16. Quantifying Low Energy Proton Damage in Multijunction Solar Cells

    NASA Technical Reports Server (NTRS)

    Messenger, Scott R.; Burke, Edward A.; Walters, Robert J.; Warner, Jeffrey H.; Summers, Geoffrey P.; Lorentzen, Justin R.; Morton, Thomas L.; Taylor, Steven J.

    2007-01-01

    An analysis of the effects of low energy proton irradiation on the electrical performance of triple junction (3J) InGaP2/GaAs/Ge solar cells is presented. The Monte Carlo ion transport code (SRIM) is used to simulate the damage profile induced in a 3J solar cell under the conditions of typical ground testing and that of the space environment. The results are used to present a quantitative analysis of the defect, and hence damage, distribution induced in the cell active region by the different radiation conditions. The modelling results show that, in the space environment, the solar cell will experience a uniform damage distribution through the active region of the cell. Through an application of the displacement damage dose analysis methodology, the implications of this result on mission performance predictions are investigated.

  17. Opportunistic Sensor Data Collection with Bluetooth Low Energy

    PubMed Central

    Aguilar, Sergio; Vidal, Rafael; Gomez, Carles

    2017-01-01

    Bluetooth Low Energy (BLE) has gained very high momentum, as witnessed by its widespread presence in smartphones, wearables and other consumer electronics devices. This fact can be leveraged to carry out opportunistic sensor data collection (OSDC) in scenarios where a sensor node cannot communicate with infrastructure nodes. In such cases, a mobile entity (e.g., a pedestrian or a vehicle) equipped with a BLE-enabled device can collect the data obtained by the sensor node when both are within direct communication range. In this paper, we characterize, both analytically and experimentally, the performance and trade-offs of BLE as a technology for OSDC, for the two main identified approaches, and considering the impact of its most crucial configuration parameters. Results show that a BLE sensor node running on a coin cell battery can achieve a lifetime beyond one year while transferring around 10 Mbit/day, in realistic OSDC scenarios. PMID:28124987

  18. NRV web knowledge base on low-energy nuclear physics

    NASA Astrophysics Data System (ADS)

    Karpov, V.; Denikin, A. S.; Alekseev, A. P.; Zagrebaev, V. I.; Rachkov, V. A.; Naumenko, M. A.; Saiko, V. V.

    2016-09-01

    Principles underlying the organization and operation of the NRV web knowledge base on low-energy nuclear physics (http://nrv.jinr.ru) are described. This base includes a vast body of digitized experimental data on the properties of nuclei and on cross sections for nuclear reactions that is combined with a wide set of interconnected computer programs for simulating complex nuclear dynamics, which work directly in the browser of a remote user. Also, the current situation in the realms of application of network information technologies in nuclear physics is surveyed. The potential of the NRV knowledge base is illustrated in detail by applying it to the example of an analysis of the fusion of nuclei that is followed by the decay of the excited compound nucleus formed.

  19. Low Energy p-bar+ H Collisions in Hyperspheroidal Coordinates

    SciTech Connect

    Matveenko, A.V.; Fukuda, Hiroshi; Alt, E.O.

    2005-10-26

    Recently, Esry and Sadeghpour (2003), and Hesse, Le and Lin (2004), have reported calculations of protonium formation in p-bar+ H collisions at low energies, using hyperspherical coordinates in a hyperradial adiabatic approach. In order to make the problem tractable both groups were forced to introduce an artificial proton mass (m{sub p}{sup '} = 17.824 a.u. and m{sub p}{sup '} = 100 a.u., respectively) which raises doubts as to the physical relevance of their results and conclusions. Here we make use of the hyperspheroidal coordinates in order to attack the same problem in basically the same approach but without need for changing the physical particle masses.

  20. Coulomb path'' interference in low energy He sup + + He collisions

    SciTech Connect

    Swenson, J.K. ); Burgdoerfer, J. ); Meyer, F.W.; Havener, C.C.; Gregory, D.C.; Stolterfoht, N. )

    1990-01-01

    A new interference mechanism, analogous to classic'' double-slit electron scattering, has been identified in low energy ion-atom collisions. This Coulomb path'' interference results from the existence of two trajectories, indistinguishable with respect to laboratory energy and emission angle, along which ejected autoionizing electrons may be scattered by the attractive Coulomb potential of the slowly receding spectator ion. We present a simple semi-classical model for this effect in which we account for the path dependence of the amplitude of the ejected electron following decay of the autoionizing state. Calculated model lineshapes are found to be in excellent agreement with strong angular dependence of the interference structure observed in the He target 2s{sup 2} {sup 1}S autoionizing lineshape measured near 0{degree} following 10 keV He{sup +} + He collisions.

  1. Low-energy antinucleon-nucleus interaction revisited

    NASA Astrophysics Data System (ADS)

    Friedman, E.

    2015-08-01

    Annihilation cross sections of antiprotons and antineutrons on the proton between 50 and 400 MeV/c show Coulomb focusing below 200 MeV/c and almost no charge-dependence above 200 MeV/c. Similar comparisons for heavier targets are not possible for lack of overlap between nuclear targets studied with and beams. Interpolating between -nucleus annihilation cross sections with the help of an optical potential to compare with -nucleus annihilation cross sections reveal unexpected features of Coulomb interactions in the latter. Direct comparisons between -nucleus and -nucleus annihilations at very low energies could be possible if cross sections are measured on the same targets and at the same energies as the available cross sections for . Such measurements may be feasible in the foreseeable future.

  2. Maximum Likelihood Analysis of Low Energy CDMS II Germanium Data

    SciTech Connect

    Agnese, R.

    2015-03-30

    We report on the results of a search for a Weakly Interacting Massive Particle (WIMP) signal in low-energy data of the Cryogenic Dark Matter Search experiment using a maximum likelihood analysis. A background model is constructed using GEANT4 to simulate the surface-event background from Pb210decay-chain events, while using independent calibration data to model the gamma background. Fitting this background model to the data results in no statistically significant WIMP component. In addition, we also perform fits using an analytic ad hoc background model proposed by Collar and Fields, who claimed to find a large excess of signal-like events in our data. Finally, we confirm the strong preference for a signal hypothesis in their analysis under these assumptions, but excesses are observed in both single- and multiple-scatter events, which implies the signal is not caused by WIMPs, but rather reflects the inadequacy of their background model.

  3. ULTRA-LOW-ENERGY HIGH-CURRENT ION SOURCE

    SciTech Connect

    Anders, Andre; Yushkov, Georgy Yu.; Baldwin, David A.

    2009-11-20

    The technical objective of the project was to develop an ultra-low-energy, high-intensity ion source (ULEHIIS) for materials processing in high-technology fields including semiconductors, micro-magnetics and optics/opto-electronics. In its primary application, this ion source can be incorporated into the 4Wave thin-film deposition technique called biased target ion-beam deposition (BTIBD), which is a deposition technique based on sputtering (without magnetic field, i.e., not the typical magnetron sputtering). It is a technological challenge because the laws of space charge limited current (Child-Langmuir) set strict limits of how much current can be extracted from a reservoir of ions, such as a suitable discharge plasma. The solution to the problem was an innovative dual-discharge system without the use of extraction grids.

  4. Ignitor with stable low-energy thermite igniting system

    DOEpatents

    Kelly, Michael D.; Munger, Alan C.

    1991-02-05

    A stable compact low-energy igniting system in an ignitor utilizes two components, an initiating charge and an output charge. The initiating charge is a thermite in ultra-fine powder form compacted to 50-70% of theoretical maximum density and disposed in a cavity of a header of the ignitor adjacent to an electrical ignition device, or bridgewire, mounted in the header cavity. The initiating charge is ignitable by operation of the ignition device in a hot-wire mode. The output charge is a thermite in high-density consoladated form compacted to 90-99% of theoretical maximum density and disposed adjacent to the initiating charge on an opposite end thereof from the electrical ignition device and ignitable by the initiating charge. A sleeve is provided for mounting the output charge to the ignitor header with the initiating charge confined therebetween in the cavity.

  5. Status report on the Low Energy Neutron Source for 2015

    NASA Astrophysics Data System (ADS)

    Baxter, D. V.; Rinckel, T.

    2016-11-01

    The Low Energy Neutron Source at Indiana University first produced cold neutrons in April of 2005. Ten years after first reaching this milestone, the facility has three instruments in operation on its cold target station, and a second target station is devoted to thermal and fast neutron physics offers capabilities in radiation effects research (single-event effects in electronics) and radiography. Key elements in our success over these last ten years have been the diversity of activities we have been able maintain (which often involves using each of our instruments for multiple different activities), the close relationship we have developed with a number of major sources, and the focus we have had on innovation in neutron instrumentation. In this presentation, we will introduce some of the highlights from our most recent activities, provide an update on some of our technical challenges, and describe some of our ideas for the future.

  6. HIGH INTENSITY LOW-ENERGY POSITRON SOURCE AT JEFFERSON

    SciTech Connect

    Serkan Golge, Bogdan Wojtsekhowski, Branislav Vlahovic

    2012-07-01

    We present a novel concept of a low-energy e{sup +} source with projected intensity on the order of 10{sup 10} slow e{sup +}/s. The key components of this concept are a continuous wave e{sup -} beam, a rotating positron-production target, a synchronized raster/anti-raster, a transport channel, and extraction of e{sup +} into a field-free area through a magnetic plug for moderation in a cryogenic solid. Components were designed in the framework of GEANT4-based (G4beamline) Monte Carlo simulation and TOSCA magnetic field calculation codes. Experimental data to demonstrate the effectiveness of the magnetic plug is presented.

  7. Inelastic low energy electron diffraction at metal surfaces

    NASA Astrophysics Data System (ADS)

    Nazarov, V. U.; Nishigaki, S.

    2001-06-01

    The role of incident electrons penetration under a metal surface in electron energy loss spectroscopy is considered within the fully quantum-mechanical approach. The stabilized jellium model of the surface in the semi-infinite geometry and the time-dependent local density approximation for the dynamical response are used. The travel of the projectile electron inside the target metal is treated within the kinematic low energy electron diffraction theory. Confirming our simplified hard-wall reflection model results [Phys. Rev. B 59 (1999) 9866], the dramatic enhancement of the multipole plasmon peak as compared with the dipole-mode calculations is obtained for Na and Cs, which is in a qualitative agreement with the experiment. However, for K the calculation fails to explain the experiment, which discrepancy is discussed and the future improvements of the method are outlined.

  8. Low-energy lepton violation from supersymmetric flipped SU(5)

    NASA Astrophysics Data System (ADS)

    Brahm, David E.; Hall, Lawrence J.

    1989-10-01

    We construct a supersymmetric flipped SU(5)⊗U(1) model which violates R parity and electron number at low energies, through a superpotential term (1/2CijkLiLjEck. Rotation of the electron and Higgs superfields makes this term also responsible for charged-lepton masses. The model employs a missing-partners mechanism for the Higgs fields and a seesaw mechanism for the neutrinos. It correctly predicts the approximate electron mass and several mass relations, as well as numerical values for the grand unification scale and the Cijk coefficients. The electron-neutrino Majorana mass is close to experimental limits, and provides constraints. Interesting Z0 decays are predicted: e.g., Z0-->e-μ+e+μ- with invariant-mass peaks in the (e,μ) channels.

  9. Low-energy dissociative recombination in small polyatomic molecules.

    PubMed

    Jungen, Ch; Pratt, S T

    2010-12-07

    Indirect dissociative recombination of low-energy electrons and molecular ions often occurs through capture into vibrationally excited Rydberg states. Properties of vibrational autoionization, the inverse of this capture mechanism, are used to develop some general ideas about the indirect recombination process, and these ideas are illustrated by examples from the literature. In particular, the Δv = -1 propensity rule for vibrational autoionization, i.e., that vibrational autoionization occurs by the minimum energetically allowed change in vibrational quantum numbers, leads to the prediction of thresholds in the dissociative recombination cross sections and rates at the corresponding vibrational thresholds. Capture into rotationally excited Rydberg states is also discussed in terms of recent low-temperature studies of the dissociative recombination of H(3)(+).

  10. Low energy neutral atoms in the earth's magnetosphere: Modeling

    SciTech Connect

    Moore, K.R.; McComas, D.J.; Funsten, H.O.; Thomsen, M.F.

    1992-01-01

    Detection of low energy neutral atoms (LENAs) produced by the interaction of the Earth's geocorona with ambient space plasma has been proposed as a technique to obtain global information about the magnetosphere. Recent instrumentation advances reported previously and in these proceedings provide an opportunity for detecting LENAs in the energy range of <1 keV to {approximately}50 keV. In this paper, we present results from a numerical model which calculates line of sight LENA fluxes expected at a remote orbiting spacecraft for various magnetospheric plasma regimes. This model uses measured charge exchange cross sections, either of two neural hydrogen geocorona models, and various empirical modes of the ring current and plasma sheet to calculate the contribution to the integrated directional flux from each point along the line of sight of the instrument. We discuss implications for LENA imaging of the magnetosphere based on these simulations. 22 refs.

  11. Low-energy electron rescattering in laser-induced ionization

    NASA Astrophysics Data System (ADS)

    Becker, W.; Goreslavski, S. P.; Milošević, D. B.; Paulus, G. G.

    2014-10-01

    The low-energy structure (LES) in the energy spectrum of above-threshold ionization of rare-gas atoms is reinvestigated from three different points of view. First, the role of forward rescattering in the completely classical simple-man model (SMM) is considered. Then, the corresponding classical electronic trajectories are retrieved in the quantum-mechanical ionization amplitude derived in the strong-field approximation augmented to allow for rescattering. Third, classical trajectories in the presence of both the laser field and the Coulomb field are scrutinized in order to see how they are related to the LES. It is concluded that the LES is already rooted in the SMM. The Coulomb field enhances the structure so that it can successfully compete with other contributions and become visible in the total spectrum.

  12. Origins of the low energy relativistic interplanetary electrons

    NASA Technical Reports Server (NTRS)

    Eraker, J. H.; Simpson, J. A.

    1981-01-01

    Electron measurements in the energy range 2-25 MeV on the Pioneer 10 spacecraft are studied from 1 to 21.5 AU. It is found that in this radial range, interplanetary low energy electron fluxes are of Jovian origin, based on the decreasing electron intensity from about 6 to 21.5 AU, a negative gradient from about 11 to 21.5 AU, and the constant spectral index observed from 1 to 21.5 AU. The upper limit of the galactic flux is estimated at 12 MeV and standard assumptions are applied to solar modulation. It is found that at 1 AU, the expected flux of galactic origin is a factor 300 or more below the observed quiet time flux, and the extrapolated interstellar flux level is consistent with estimates based on galactic diffuse radio and gamma-ray emissions.

  13. Low Dose, Low Energy 3d Image Guidance during Radiotherapy

    NASA Astrophysics Data System (ADS)

    Moore, C. J.; Marchant, T.; Amer, A.; Sharrock, P.; Price, P.; Burton, D.

    2006-04-01

    Patient kilo-voltage X-ray cone beam volumetric imaging for radiotherapy was first demonstrated on an Elekta Synergy mega-voltage X-ray linear accelerator. Subsequently low dose, reduced profile reconstruction imaging was shown to be practical for 3D geometric setup registration to pre-treatment planning images without compromising registration accuracy. Reconstruction from X-ray profiles gathered between treatment beam deliveries was also introduced. The innovation of zonal cone beam imaging promises significantly reduced doses to patients and improved soft tissue contrast in the tumour target zone. These developments coincided with the first dynamic 3D monitoring of continuous body topology changes in patients, at the moment of irradiation, using a laser interferometer. They signal the arrival of low dose, low energy 3D image guidance during radiotherapy itself.

  14. First evidence of low energy enhancement in Ge isotopes

    NASA Astrophysics Data System (ADS)

    Renstrøm, T.; Nyhus, H.-T.; Utsunomiya, H.; Larsen, A. C.; Siem, S.; Guttormsen, M.; Filipescu, D. M.; Gheorghe, I.; Goriely, S.; Bernstein, L. A.; Bleuel, D. L.; Glodariu, T.; Görgen, A.; Hagen, T. W.; Lui, Y.-W.; Negi, D.; Ruud, I. E.; Şahin, E.; Schwengner, R.; Shima, T.; Takahisa, K.; Tesileanu, O.; Tornyi, T. G.; Tveten, G. M.; Wiedeking, M.

    2015-05-01

    The γ-strength functions and level densities of 73,74Ge have been extracted from particle-γ coincidence data using the Oslo method. In addition the γ-strength function of 74Ge above the neutron separation threshold, Sn = 10.196 MeV has been extracted from photoneutron measurements. When combined, these two experiments give a γ-strength function covering the energy range of ˜1-13 MeV for 74Ge. This thorough investigation of 74Ge is a part of an international campaign to study the previously reported low energy enhancement in this mass region in the γ-strength function from ˜3MeV towards lower γ energies. The obtained data show that both 73,74Ge display an increase in strength at low γ energies.

  15. Elastic positron-cadmium scattering at low energies

    SciTech Connect

    Bromley, M. W. J.; Mitroy, J.

    2010-05-15

    The elastic and annihilation cross sections for positron-cadmium scattering are reported up to the positronium-formation threshold (at 2.2 eV). The low-energy phase shifts for the elastic scattering of positrons from cadmium were derived from the bound and pseudostate energies of a very large basis configuration-interaction calculation of the e{sup +}-Cd system. The s-wave binding energy is estimated to be 126{+-}42 meV, with a scattering length of A{sub scat}=(14.2{+-}2.1)a{sub 0}, while the threshold annihilation parameter, Z{sub eff}, was 93.9{+-}26.5. The p-wave phase shift exhibits a weak shape resonance that results in a peak Z{sub eff} of 91{+-}17 at a collision energy of about 490{+-}50 meV.

  16. Low-Energy Properties of Aperiodic Quantum Spin Chains

    NASA Astrophysics Data System (ADS)

    Vieira, André P.

    2005-02-01

    We investigate the low-energy properties of antiferromagnetic quantum XXZ spin chains with couplings following two-letter aperiodic sequences, by an adaptation of the Ma-Dasgupta-Hu renormalization-group method. For a given aperiodic sequence, we argue that, in the easy-plane anisotropy regime, intermediate between the XX and Heisenberg limits, the general scaling form of the thermodynamic properties is essentially given by the exactly known XX behavior, providing a classification of the effects of aperiodicity on XXZ chains. As representative illustrations, we present analytical and numerical results for the low-temperature thermodynamics and the ground-state correlations for couplings following the Fibonacci quasiperiodic structure and a binary Rudin-Shapiro sequence, whose geometrical fluctuations are similar to those induced by randomness.

  17. Low-energy dissociative electron attachment to CF2

    NASA Astrophysics Data System (ADS)

    Chourou, S. T.; Larson, Ã.; Orel, A. E.

    2015-08-01

    We present the results of a theoretical study of dissociative electron attachment (DEA) of low-energy electrons to CF2. We carried out electron scattering calculations using the complex Kohn variational method at the static-exchange and relaxed self-consistent field (SCF) level at the equilibrium geometry and compare our differential cross sections to other results. We then repeated these calculations as a function of the three internal degrees of freedom to obtain the resonance energy surfaces and autoionization widths. We use this data as input to form the Hamiltonian relevant to the nuclear dynamics. The multidimensional wave equation is solved using the multiconfiguration time-dependent Hartree (MCTDH) approach within the local approximation.

  18. Low-energy properties of aperiodic quantum spin chains.

    PubMed

    Vieira, André P

    2005-02-25

    We investigate the low-energy properties of antiferromagnetic quantum XXZ spin chains with couplings following two-letter aperiodic sequences, by an adaptation of the Ma-Dasgupta-Hu renormalization-group method. For a given aperiodic sequence, we argue that, in the easy-plane anisotropy regime, intermediate between the XX and Heisenberg limits, the general scaling form of the thermodynamic properties is essentially given by the exactly known XX behavior, providing a classification of the effects of aperiodicity on XXZ chains. As representative illustrations, we present analytical and numerical results for the low-temperature thermodynamics and the ground-state correlations for couplings following the Fibonacci quasiperiodic structure and a binary Rudin-Shapiro sequence, whose geometrical fluctuations are similar to those induced by randomness.

  19. Space charge effects in the SSC Low Energy Booster

    SciTech Connect

    Machida, S.; Bourianoff, G.; Mahale, N.K.; Mehta, N.; Pilat, F.; Talman, R.; York, R.C.

    1991-05-01

    By means of multi-particle tracking, we explore space charge effects in the Low Energy Booster (LEB) which has a strong requirement for small transverse emittance. Macro-particles are tracked in a self-consistent manner in six dimensional phase space with transverse space charge kicks so that the emittance evolution as well as the particle distribution are simulated as a function of time. Among recent improvements of the code, the longitudinal motion, i.e. synchrotron oscillations as well as acceleration, makes it possible to simulate the capture process of linac microbunches. The code was calibrated by comparing with the experimental results at the Fermilab Booster. Preliminary results of the LEB show slow emittance growth due to the space charge. 5 refs., 5 figs., 1 tab.

  20. Advanced satellite sensors: Low Energy Neutral Atom (LENA) imager

    SciTech Connect

    Funsten, H.O.; McComas, D.J.

    1996-09-01

    This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). Imaging of low energy neutral atoms (LENDs) created by electron capture by magnetospheric plasma ions from interactions with cold geocoronal neutrals promises to be a revolutionary technique for providing unprecedented information about the global structure and dynamics of the terrestrial magnetosphere. This has significant implications in space weather forecasting, weather-induced satellite upset diagnostics, and revolutionary insights into global magnetospheric physics. The Los Alamos Space and Atmospheric Sciences Group has completed extensive neutral atom simulations and detailed instrument definition, and we designed a proof-of-concept demonstration prototype and have obtained externally- funded programs for full instrument development

  1. Low energy neutral atom imaging: Remote observations of the magnetosphere

    SciTech Connect

    Funsten, H.O.; McComas, D.J.; Scime, E.E.; Moore, K.R.

    1995-02-01

    Recent developments in detection of neutral atom imaging should enable imaging the global structure and dynamics of the terrestrial magnetosphere. The inherent technical challenge of imaging low energy neutral atoms (LENAs) with energy < 30 keV is their separation from the tremendous UV background, to which LENA detectors are sensitive, without loss of information of LENA trajectory and energy. Three instrument concepts for separating LENAs from the background UV are presented: LENA charge conversion via transmission through an ultrathin carbon foil and subsequent electrostatic deflection, EUV grating polarizers and attenuators, and high frequency shutters. Each of these concepts can be mated to a detector section that provides both LENA imaging capability and coincidence/time-of-flight.

  2. Spectroscopy of low energy solar neutrinos by MOON

    NASA Astrophysics Data System (ADS)

    Hazama, R.; Doe, P.; Ejiri, H.; Elliott, S. R.; Engel, J.; Finger, M.; Formaggio, J. A.; Fushimi, K.; Gehman, V.; Gorin, A.; Greenfield, M.; Ichihara, K.; Ikegami, Y.; Ishii, H.; Itahashi, T.; Kavitov, P.; Kekelidze, V.; Kuroda, K.; Kutsalo, V.; Manouilov, I.; Matsuoka, K.; Nakamura, H.; Nomachi, M.; Para, A.; Rielage, K.; Rjazantsev, A.; Robertson, R. G. H.; Shichijo, Y.; Shima, T.; Shimada, Y.; Shirkov, G.; Sissakian, A.; Sugaya, Y.; Titov, A.; Vatulin, V.; Vilches, O. E.; Voronov, V.; Wilkerson, J. F.; Will, D. I.; Yoshida, S.

    2005-01-01

    The MOON (Molybdenum Observatory Of Neutrinos) project aims at high sensitive studies of the double beta (ββ) decays with sensitivity to Majorana ν mass of the order of ˜0.03 eV and the charged-current (CC) neutrino spectroscopy of the major components of the pp and 7Be solar ν's. The present status of MOON for the low energy solar ν experiment is briefly discussed. The inverse β rays from solar-ν captures of 100Mo are measured in delayed coincidence with the subsequent β decay of 100Tc. MOON's exclusive CC value by 7Be solar ν, together with the GNO CC data, will provide the pp solar ν flux with good accuracy.

  3. Bluetooth low energy: wireless connectivity for medical monitoring.

    PubMed

    Omre, Alf Helge

    2010-03-01

    Electronic wireless sensors could cut medical costs by enabling physicians to remotely monitor vital signs such as blood pressure, blood glucose, and blood oxygenation while patients remain at home. According to the IDC report "Worldwide Bluetooth Semiconductor 2008-2012 Forecast," published November 2008, a forthcoming radio frequency communication ("wireless connectivity") standard, Bluetooth low energy, will link wireless sensors via radio signals to the 70% of cell phones and computers likely to be fitted with the next generation of Bluetooth wireless technology, leveraging a ready-built infrastructure for data transmission. Analysis of trends indicated by this data can help physicians better manage diseases such as diabetes. The technology also addresses the concerns of cost, compatibility, and interoperability that have previously stalled widespread adoption of wireless technology in medical applications.

  4. Modeling of human movement monitoring using Bluetooth Low Energy technology.

    PubMed

    Mokhtari, G; Zhang, Q; Karunanithi, M

    2015-01-01

    Bluetooth Low Energy (BLE) is a wireless communication technology which can be used to monitor human movements. In this monitoring system, a BLE signal scanner scans signal strength of BLE tags carried by people, to thus infer human movement patterns within its monitoring zone. However to the extent of our knowledge one main aspect of this monitoring system which has not yet been thoroughly investigated in literature is how to build a sound theoretical model, based on tunable BLE communication parameters such as scanning time interval and advertising time interval, to enable the study and design of effective and efficient movement monitoring systems. In this paper, we proposed and developed a statistical model based on Monte-Carlo simulation, which can be utilized to assess impacts of BLE technology parameters in terms of latency and efficiency, on a movement monitoring system, and can thus benefit a more efficient system design.

  5. Flux tube spectra from approximate integrability at low energies

    NASA Astrophysics Data System (ADS)

    Dubovsky, S.; Flauger, R.; Gorbenko, V.

    2015-03-01

    We provide a detailed introduction to a method we recently proposed for calculating the spectrum of excitations of effective strings such as QCD flux tubes. The method relies on the approximate integrability of the low-energy effective theory describing the flux tube excitations and is based on the thermodynamic Bethe ansatz. The approximate integrability is a consequence of the Lorentz symmetry of QCD. For excited states, the convergence of the thermodynamic Bethe ansatz technique is significantly better than that of the traditional perturbative approach. We apply the new technique to the lattice spectra for fundamental flux tubes in gluodynamics in D = 3 + 1 and D = 2 + 1, and to k-strings in gluodynamics in D = 2 + 1. We identify a massive pseudoscalar resonance on the worldsheet of the confining strings in SU(3) gluodynamics in D = 3 + 1, and massive scalar resonances on the worldsheet of k = 2.3 strings in SU(6) gluodynamics in D = 2 + 1.

  6. Low-energy Coulomb excitation of Sr,9896 beams

    NASA Astrophysics Data System (ADS)

    Clément, E.; Zielińska, M.; Péru, S.; Goutte, H.; Hilaire, S.; Görgen, A.; Korten, W.; Doherty, D. T.; Bastin, B.; Bauer, C.; Blazhev, A.; Bree, N.; Bruyneel, B.; Butler, P. A.; Butterworth, J.; Cederkäll, J.; Delahaye, P.; Dijon, A.; Ekström, A.; Fitzpatrick, C.; Fransen, C.; Georgiev, G.; Gernhäuser, R.; Hess, H.; Iwanicki, J.; Jenkins, D. G.; Larsen, A. C.; Ljungvall, J.; Lutter, R.; Marley, P.; Moschner, K.; Napiorkowski, P. J.; Pakarinen, J.; Petts, A.; Reiter, P.; Renstrøm, T.; Seidlitz, M.; Siebeck, B.; Siem, S.; Sotty, C.; Srebrny, J.; Stefanescu, I.; Tveten, G. M.; Van de Walle, J.; Vermeulen, M.; Voulot, D.; Warr, N.; Wenander, F.; Wiens, A.; De Witte, H.; Wrzosek-Lipska, K.

    2016-11-01

    The structure of neutron-rich Sr,9896 nuclei was investigated by low-energy safe Coulomb excitation of radioactive beams at the REX-ISOLDE facility, CERN, with the MINIBALL spectrometer. A rich set of transitional and diagonal E 2 matrix elements, including those for non-yrast structures, has been extracted from the differential Coulomb-excitation cross sections. The results support the scenario of a shape transition at N =60 , giving rise to the coexistence of a highly deformed prolate and a spherical configuration in 98Sr, and are compared to predictions from several theoretical calculations. The experimental data suggest a significant contribution of the triaxal degree of freedom in the ground state of both isotopes. In addition, experimental information on low-lying states in 98Rb has been obtained.

  7. Low energy electron collisions with He 2+ molecules

    NASA Astrophysics Data System (ADS)

    McLaughlin, B. M.; Gillan, C. J.; Burke, P. G.; Dahler, J. S.

    1991-04-01

    The R-matrix method is used in an ab initio study of low energy elastic scattering by He 2+ molecular ions. SCF and correlated CI wavefunctions have been used in a two state approximation, which retains the lowest two states, 2∑ u+ and 2∑ g+, of the He 2+ molecular ion in the scattering basis. Cross section calculations have been performed at two fixed internuclear separations, 1.8 and 2.0625 a0. At the equilibrium bond separation we have detected and fitted the lowest lying n pσ 3Σ u+ resonances in the 3Σ +u scattering symmetry. In addition, bound state calculations have also been carried out for the He 2 (1 σg+1 σu2s a 3Σu+) state at these two internuclear separations and are seen to compare favorably with MCSCF and SOCI results.

  8. Linac4 low energy beam measurements with negative hydrogen ions

    NASA Astrophysics Data System (ADS)

    Scrivens, R.; Bellodi, G.; Crettiez, O.; Dimov, V.; Gerard, D.; Granemann Souza, E.; Guida, R.; Hansen, J.; Lallement, J.-B.; Lettry, J.; Lombardi, A.; Midttun, Ø.; Pasquino, C.; Raich, U.; Riffaud, B.; Roncarolo, F.; Valerio-Lizarraga, C. A.; Wallner, J.; Yarmohammadi Satri, M.; Zickler, T.

    2014-02-01

    Linac4, a 160 MeV normal-conducting H- linear accelerator, is the first step in the upgrade of the beam intensity available from the LHC proton injectors at CERN. The Linac4 Low Energy Beam Transport (LEBT) line from the pulsed 2 MHz RF driven ion source, to the 352 MHz RFQ (Radiofrequency Quadrupole) has been built and installed at a test stand, and has been used to transport and match to the RFQ a pulsed 14 mA H- beam at 45 keV. A temporary slit-and-grid emittance measurement system has been put in place to characterize the beam delivered to the RFQ. In this paper a description of the LEBT and its beam diagnostics is given, and the results of beam emittance measurements and beam transmission measurements through the RFQ are compared with the expectation from simulations.

  9. Linac4 low energy beam measurements with negative hydrogen ions

    SciTech Connect

    Scrivens, R. Bellodi, G.; Crettiez, O.; Dimov, V.; Gerard, D.; Granemann Souza, E.; Guida, R.; Hansen, J.; Lallement, J.-B.; Lettry, J.; Lombardi, A.; Midttun, Ø.; Pasquino, C.; Raich, U.; Riffaud, B.; Roncarolo, F.; Valerio-Lizarraga, C. A.; Wallner, J.; Yarmohammadi Satri, M.; Zickler, T.

    2014-02-15

    Linac4, a 160 MeV normal-conducting H{sup −} linear accelerator, is the first step in the upgrade of the beam intensity available from the LHC proton injectors at CERN. The Linac4 Low Energy Beam Transport (LEBT) line from the pulsed 2 MHz RF driven ion source, to the 352 MHz RFQ (Radiofrequency Quadrupole) has been built and installed at a test stand, and has been used to transport and match to the RFQ a pulsed 14 mA H{sup −} beam at 45 keV. A temporary slit-and-grid emittance measurement system has been put in place to characterize the beam delivered to the RFQ. In this paper a description of the LEBT and its beam diagnostics is given, and the results of beam emittance measurements and beam transmission measurements through the RFQ are compared with the expectation from simulations.

  10. Low-Energy Impacts onto Lunar Regolith Simulant

    NASA Astrophysics Data System (ADS)

    Seward, Laura M.; Colwell, J.; Mellon, M.; Stemm, B.

    2012-10-01

    Low-Energy Impacts onto Lunar Regolith Simulant Laura M. Seward1, Joshua E. Colwell1, Michael T. Mellon2, and Bradley A. Stemm1, 1Department of Physics, University of Central Florida, Orlando, Florida, 2Southwest Research Institute, Boulder, Colorado. Impacts and cratering in space play important roles in the formation and evolution of planetary bodies. Low-velocity impacts and disturbances to planetary regolith are also a consequence of manned and robotic exploration of planetary bodies such as the Moon, Mars, and asteroids. We are conducting a program of laboratory experiments to study low-velocity impacts of 1 to 5 m/s into JSC-1 lunar regolith simulant, JSC-Mars-1 Martian regolith simulant, and silica targets under 1 g. We use direct measurement of ejecta mass and high-resolution video tracking of ejecta particle trajectories to derive ejecta mass velocity distributions. Additionally, we conduct similar experiments under microgravity conditions in a laboratory drop tower and on parabolic aircraft with velocities as low as 10 cm/s. We wish to characterize and understand the collision parameters that control the outcome of low-velocity impacts into regolith, including impact velocity, impactor mass, target shape and size distribution, regolith depth, target relative density, and crater depth, and to experimentally determine the functional dependencies of the outcomes of low-velocity collisions (ejecta mass and ejecta velocities) on the controlling parameters of the collision. We present results from our ongoing study showing the positive correlation between impact energy and ejecta mass. The total ejecta mass is also dependent on the packing density (porosity) of the regolith. We find that ejecta mass velocity fits a power-law or broken power-law distribution. Our goal is to understand the physics of ejecta production and regolith compaction in low-energy impacts and experimentally validate predictive models for dust flow and deposition. We will present our

  11. Low energy ion beam dynamics of NANOGAN ECR ion source

    NASA Astrophysics Data System (ADS)

    Kumar, Sarvesh; Mandal, A.

    2016-04-01

    A new low energy ion beam facility (LEIBF) has been developed for providing the mass analyzed highly charged intense ion beams of energy ranging from a few tens of keV to a few MeV for atomic, molecular and materials sciences research. The new facility consists of an all permanent magnet 10 GHz electron cyclotron resonance (ECR) ion source (NANOGAN) installed on a high voltage platform (400 kV) which provides large currents of multiply charged ion beams. Higher emittance at low energy of intense ion beam puts a tremendous challenge to the beam optical design of this facility. The beam line consists of mainly the electrostatic quadrupoles, an accelerating section, analyzing cum switching magnet and suitable beam diagnostics including vacuum components. The accelerated ion beam is analyzed for a particular mass to charge (m/q) ratio as well as guided to three different lines along 75°, 90° and 105° using a large acceptance analyzing cum switching magnet. The details of transverse beam optics to all the beam lines with TRANSPORT and GICOSY beam optics codes are being described. Field computation code, OPERA 3D has been utilized to design the magnets and electrostatic quadrupoles. A theoretical estimation of emittance for optimized geometry of ion source is given so as to form the basis of beam optics calculations. The method of quadrupole scan of the beam is used to characterize the emittance of the final beam on the target. The measured beam emittance increases with m/q ratios of various ion beams similar to the trend observed theoretically.

  12. Restrained dark U (1 )d at low energies

    NASA Astrophysics Data System (ADS)

    Correia, Fagner C.; Fajfer, Svjetlana

    2016-12-01

    We investigate a spontaneously broken U (1 )d gauge symmetry with a muon-specific dark Higgs. Our first goal is to verify how the presence of a new dark Higgs, ϕ , and a dark gauge boson, V , can simultaneously face the anomalies from the muon magnetic moment and the proton charge radius. Second, by assuming that V must decay to an electron-positron pair, we explore the corresponding parameter space determined with the low-energy constraints coming from K →μ X , electron (g -2 )e, K →μ νμe+e-, K →μ νμμ+μ-, and τ →ντμ νμe+e-. We focus on the scenario where the V mass is below ˜2 mμ and the ϕ mass runs from few MeV to 250 MeV, with V -photon mixing of the order ˜O (10-3). Among weak process at low energies, we check the influence of the new light vector on kaon decays as well as on the scattering e+e-→μ+μ-e+e- and discuss the impact of the dark Higgs on e+e-→μ+μ-μ+μ-. Finally, we consider contributions of the V -photon mixing in the decays π0→γ e+e-, η →γ e+e-, ρ →π e+e-, K*→K e+e-, and ϕ (1020 )→η e+e-.

  13. White paper on nuclear astrophysics and low-energy nuclear physics, Part 2: Low-energy nuclear physics

    DOE PAGES

    Carlson, Joe; Carpenter, Michael P.; Casten, Richard; ...

    2017-05-01

    In preparation for the 2015 NSAC Long Range Plan (LRP), the DNP town meetings on Nuclear Astrophysics and Low-Energy Nuclear Physics were held at the Mitchell Center on the campus of Texas A&M University August 21–23, 2014. Participants met in a number of topic-oriented working groups to discuss progress since the 2007 LRP, compelling science opportunities, and the resources needed to advance them. These considerations were used to determine priorities for the next five to ten years. In addition, approximately 270 participants attended the meetings, coming from US national laboratories, a wide range of US universities and other research institutionsmore » and universities abroad.« less

  14. Dental Implants.

    PubMed

    Zohrabian, Vahe M; Sonick, Michael; Hwang, Debby; Abrahams, James J

    2015-10-01

    Dental implants restore function to near normal in partially or completely edentulous patients. A root-form implant is the most frequently used type of dental implant today. The basis for dental implants is osseointegration, in which osteoblasts grow and directly integrate with the surface of titanium posts surgically embedded into the jaw. Radiologic assessment is critical in the preoperative evaluation of the dental implant patient, as the exact height, width, and contour of the alveolar ridge must be determined. Moreover, the precise locations of the maxillary sinuses and mandibular canals, as well as their relationships to the site of implant surgery must be ascertained. As such, radiologists must be familiar with implant design and surgical placement, as well as augmentation procedures utilized in those patients with insufficient bone in the maxilla and mandible to support dental implants.

  15. Cochlear Implants

    MedlinePlus

    ... NIDCD A cochlear implant is a small, complex electronic device that can help to provide a sense ... are better able to hear, comprehend sound and music, and speak than their peers who receive implants ...

  16. Cochlear implant

    MedlinePlus

    ... antenna. This part of the implant receives the sound, converts the sound into an electrical signal, and sends it to ... implants allow deaf people to receive and process sounds and speech. However, these devices do not restore ...

  17. Low-energy Model for Strongly Correlated Oxides

    NASA Astrophysics Data System (ADS)

    Liu, Shiu

    We provide a detailed derivation of the low-energy model for site-diluted strongly correlated oxides, an example being Zn-diluted La2CuO 4, in the limit of low doping together with a study of the ground-state properties of that model. The generally complicated Hamiltonian on the energy scale of the most relevant atomic orbitals is systematically downfolded to an effective model containing only spin-spin interactions using several techniques. In our study, beginning with the site-diluted three-band Hubbard model for La2ZnxCu(1- x)O4, we first determine the hybridized electronic states of CuO4 and ZnO4 plaquettes within the CuO2 planes utilizing Wannier-orthogonalization of oxygen orbitals and cell-perturbation of the Hamiltonian of each plaquett. Qualitatively, we find that the hybridization of zinc and oxygen orbitals can result in an impurity state with the energy epsilon, which is lower than the effective Hubbard gap U. Then we apply canonical transformation in the limit of the effective hopping integral t << epsilon, U, to obtain the low-energy, spin-only Hamiltonian, which includes terms of the order t2/U, t4/epsilon3, and t 4/Uepsilon2. In other words, besides the usual diluted nearest-neighbor superexchange J-terms of order t2/U, the low-energy model contains impurity-mediated, further-neighbor frustrating interactions among the Cu spins surrounding Zn-sites in an otherwise unfrustrated antiferromagnetic background. These terms, denoted as J'Zn and J''Zn , are of order t4/epsilon3 and can be substantial when epsilon ˜ U/2, the latter value corresponding to the realistic CuO2 parameters. The other further-neighbor Cu spin interactions are of order t 4/U3, which are neglected in both pure and diluted systems, because they are much lesser than J'Zn and J''Zn and independent of impurity concentration. In order to verify this spin-only model, we subsequently apply the T-matrix approach to study the effect of impurities on the antiferromagnetic order parameter

  18. In-medium nuclear interactions of low-energy hadrons

    NASA Astrophysics Data System (ADS)

    Friedman, E.; Gal, A.

    2007-11-01

    Exotic atoms provide a unique laboratory for studying strong interactions and nuclear medium effects at zero kinetic energy. Experimental and theoretical developments of the last decade in the study of exotic atoms and some related low-energy reactions are reviewed. The exotic atoms considered are of π-,K-,pbar,Σ-, and also the so far unobserved Ξ- atoms. The analysis of these atomic systems consists of fitting density-dependent optical potentials Vopt=t(ρ)ρ to comprehensive sets of data of strong-interaction level shifts, widths and yields across the periodic table. These provide information on the in-medium hadron-nucleon t matrix t(ρ) over a wide range of densities up to central nuclear densities. For pions, the review focuses on the extraction of the πN in-medium s-wave interaction from pionic atoms, which include also the deeply bound π- atomic states recently observed at GSI in isotopes of Sn and Pb. Also included are recent measurements at PSI of elastic scattering of π± on Si, Ca, Ni and Zr at 21.5 MeV. The experimental results are analyzed in the context of chirally motivated π-nuclear potentials, and the evidence for partial restoration of chiral symmetry in dense nuclear matter is critically discussed. For antikaons, we review the evidence from K- atoms, and also from low-energy K-p scattering and reaction data for and against a deepKbar-nucleus potential of 150-200 MeV attraction at nuclear matter density. The case for relatively narrow deeply bound K-atomic states is made, essentially independent of the potential-depth issue. Recent experimental suggestions from KEK and DA ΦNE (Frascati) for signals of Kbar-nuclear deeply bound states are reviewed, and dynamical models for calculating binding energies and widths of Kbar- nuclear states are discussed. For kaons we review the evidence, from K+ total and reaction cross section measurements at the AGS (BNL) on Li, C, Si and Ca at plab=500-700 MeV/c, for significant absorptivity of t

  19. Hybrid Organic/Inorganic Materials Depth Profiling Using Low Energy Cesium Ions

    NASA Astrophysics Data System (ADS)

    Noël, Céline; Houssiau, Laurent

    2016-05-01

    The structures developed in organic electronics, such as organic light emitting diodes (OLEDs) or organic photovoltaics (OPVs) devices always involve hybrid interfaces, joining metal or oxide layers with organic layers. No satisfactory method to probe these hybrid interfaces physical chemistry currently exists. One promising way to analyze such interfaces is to use in situ ion beam etching, but this requires ion beams able to depth profile both inorganic and organic layers. Mono- or diatomic ion beams commonly used to depth profile inorganic materials usually perform badly on organics, while cluster ion beams perform excellently on organics but yield poor results when organics and inorganics are mixed. Conversely, low energy Cs+ beams (<500 eV) allow organic and inorganic materials depth profiling with comparable erosion rates. This paper shows a successful depth profiling of a model hybrid system made of metallic (Au, Cr) and organic (tyrosine) layers, sputtered with 500 eV Cs+ ions. Tyrosine layers capped with metallic overlayers are depth profiled easily, with high intensities for the characteristic molecular ions and other specific fragments. Metallic Au or Cr atoms are recoiled into the organic layer where they cause some damage near the hybrid interface as well as changes in the erosion rate. However, these recoil implanted metallic atoms do not appear to severely degrade the depth profile overall quality. This first successful hybrid depth profiling report opens new possibilities for the study of OLEDs, organic solar cells, or other hybrid devices.

  20. Low-Energy Plasma Spray (LEPS) Deposition of Hydroxyapatite/Poly-ɛ-Caprolactone Biocomposite Coatings

    NASA Astrophysics Data System (ADS)

    Garcia-Alonso, Diana; Parco, Maria; Stokes, Joseph; Looney, Lisa

    2012-01-01

    Thermal spraying is widely employed to deposit hydroxyapatite (HA) and HA-based biocomposites on hip and dental implants. For thick HA coatings (>150 μm), problems are generally associated with the build-up of residual stresses and lack of control of coating crystallinity. HA/polymer composite coatings are especially interesting to improve the pure HA coatings' mechanical properties. For instance, the polymer may help in releasing the residual stresses in the thick HA coatings. In addition, the selection of a bioresorbable polymer may enhance the coatings' biological behavior. However, there are major challenges associated with spraying ceramic and polymeric materials together because of their very different thermal properties. In this study, pure HA and HA/poly-ɛ-caprolactone (PCL) thick coatings were deposited without significant thermal degradation by low-energy plasma spraying (LEPS). PCL has never been processed by thermal spraying, and its processing is a major achievement of this study. The influence of selected process parameters on microstructure, composition, and mechanical properties of HA and HA/PCL coatings was studied using statistical design of experiments (DOE). The HA deposition rate was significantly increased by the addition of PCL. The average porosity of biocomposite coatings was slightly increased, while retaining or even improving in some cases their fracture toughness and microhardness. Surface roughness of biocomposites was enhanced compared with HA pure coatings. Cell culture experiments showed that murine osteoblast-like cells attach and proliferate well on HA/PCL biocomposite deposits.

  1. Hybrid Organic/Inorganic Materials Depth Profiling Using Low Energy Cesium Ions.

    PubMed

    Noël, Céline; Houssiau, Laurent

    2016-05-01

    The structures developed in organic electronics, such as organic light emitting diodes (OLEDs) or organic photovoltaics (OPVs) devices always involve hybrid interfaces, joining metal or oxide layers with organic layers. No satisfactory method to probe these hybrid interfaces physical chemistry currently exists. One promising way to analyze such interfaces is to use in situ ion beam etching, but this requires ion beams able to depth profile both inorganic and organic layers. Mono- or diatomic ion beams commonly used to depth profile inorganic materials usually perform badly on organics, while cluster ion beams perform excellently on organics but yield poor results when organics and inorganics are mixed. Conversely, low energy Cs(+) beams (<500 eV) allow organic and inorganic materials depth profiling with comparable erosion rates. This paper shows a successful depth profiling of a model hybrid system made of metallic (Au, Cr) and organic (tyrosine) layers, sputtered with 500 eV Cs(+) ions. Tyrosine layers capped with metallic overlayers are depth profiled easily, with high intensities for the characteristic molecular ions and other specific fragments. Metallic Au or Cr atoms are recoiled into the organic layer where they cause some damage near the hybrid interface as well as changes in the erosion rate. However, these recoil implanted metallic atoms do not appear to severely degrade the depth profile overall quality. This first successful hybrid depth profiling report opens new possibilities for the study of OLEDs, organic solar cells, or other hybrid devices.

  2. The use of low energy, ion induced nuclear reactions for proton radiotherapy applications

    SciTech Connect

    Horn, K.M.; Doyle, B.; Segal, M.N.; Hamm, R.W.; Adler, R.J.; Glatstein, E.

    1995-04-01

    Medical radiotherapy has traditionally relied upon the use of external photon beams and internally implanted radioisotopes as the chief means of irradiating tumors. However, advances in accelerator technology and the exploitation of novel means of producing radiation may provide useful alternatives to some current modes of medical radiation delivery with reduced total dose to surrounding healthy tissue, reduced expense, or increased treatment accessibility. This paper will briefly overview currently established modes of radiation therapy, techniques still considered experimental but in clinical use, innovative concepts under study that may enable new forms of treatment or enhance existing ones. The potential role of low energy, ion-induced nuclear reactions in radiotherapy applications is examined specifically for the 650 keV d({sup 3}He,p){sup 4}He nuclear reaction. This examination will describe the basic physics associated with this reaction`s production of 17.4 MeV protons and the processes used to fabricate the necessary materials used in the technique. Calculations of the delivered radiation dose, heat generation, and required exposure times are presented. Experimental data are also presented validating the dose calculations. The design of small, lower cost ion accelerators, as embodied in `nested`-tandem and radio frequency quadrupole accelerators is examined, as is the potential use of high-output {sup 3}He and deuterium ion sources. Finally, potential clinical applications are discussed in terms of the advantages and disadvantages of this technique with respect to current radiotherapy methods and equipment.

  3. Sensitivity of low energy brachytherapy Monte Carlo dose calculations to uncertainties in human tissue composition

    SciTech Connect

    Landry, Guillaume; Reniers, Brigitte; Murrer, Lars; Lutgens, Ludy; Bloemen-Van Gurp, Esther; Pignol, Jean-Philippe; Keller, Brian; Beaulieu, Luc; Verhaegen, Frank

    2010-10-15

    Purpose: The objective of this work is to assess the sensitivity of Monte Carlo (MC) dose calculations to uncertainties in human tissue composition for a range of low photon energy brachytherapy sources: {sup 125}I, {sup 103}Pd, {sup 131}Cs, and an electronic brachytherapy source (EBS). The low energy photons emitted by these sources make the dosimetry sensitive to variations in tissue atomic number due to the dominance of the photoelectric effect. This work reports dose to a small mass of water in medium D{sub w,m} as opposed to dose to a small mass of medium in medium D{sub m,m}. Methods: Mean adipose, mammary gland, and breast tissues (as uniform mixture of the aforementioned tissues) are investigated as well as compositions corresponding to one standard deviation from the mean. Prostate mean compositions from three different literature sources are also investigated. Three sets of MC simulations are performed with the GEANT4 code: (1) Dose calculations for idealized TG-43-like spherical geometries using point sources. Radial dose profiles obtained in different media are compared to assess the influence of compositional uncertainties. (2) Dose calculations for four clinical prostate LDR brachytherapy permanent seed implants using {sup 125}I seeds (Model 2301, Best Medical, Springfield, VA). The effect of varying the prostate composition in the planning target volume (PTV) is investigated by comparing PTV D{sub 90} values. (3) Dose calculations for four clinical breast LDR brachytherapy permanent seed implants using {sup 103}Pd seeds (Model 2335, Best Medical). The effects of varying the adipose/gland ratio in the PTV and of varying the elemental composition of adipose and gland within one standard deviation of the assumed mean composition are investigated by comparing PTV D{sub 90} values. For (2) and (3), the influence of using the mass density from CT scans instead of unit mass density is also assessed. Results: Results from simulation (1) show that variations

  4. Low-energy theory for the graphene twist bilayer

    NASA Astrophysics Data System (ADS)

    Weckbecker, D.; Shallcross, S.; Fleischmann, M.; Ray, N.; Sharma, S.; Pankratov, O.

    2016-01-01

    The graphene twist bilayer represents the prototypical system for investigating the stacking degree of freedom in few-layer graphenes. The electronic structure of this system changes qualitatively as a function of angle, from a large-angle limit in which the two layers are essentially decoupled—with the exception of a 28-atom commensuration unit cell for which the layers are coupled on an energy scale of ≈8 meV —to a small-angle strong-coupling limit. Despite sustained investigation, a fully satisfactory theory of the twist bilayer remains elusive. The outstanding problems are (i) to find a theoretically unified description of the large- and small-angle limits, and (ii) to demonstrate agreement between the low-energy effective Hamiltonian and, for instance, ab initio or tight-binding calculations. In this article, we develop a low-energy theory that in the large-angle limit reproduces the symmetry-derived Hamiltonians of Mele [Phys. Rev. B 81, 161405 (2010), 10.1103/PhysRevB.81.161405], and in the small-angle limit shows almost perfect agreement with tight-binding calculations. The small-angle effective Hamiltonian is that of Bistritzer and MacDonald [Proc. Natl. Acad. Sci. (U.S.A.) 108, 12233 (2011), 10.1073/pnas.1108174108], but with the momentum scale Δ K , the difference of the momenta of the unrotated and rotated special points, replaced by a coupling momentum scale g(c )=8/π √{3 }a sinθ/2 . Using this small-angle Hamiltonian, we are able to determine the complete behavior as a function of angle, finding a complex small-angle clustering of van Hove singularities in the density of states (DOS) that after a "zero-mode" peak regime between 0 .90°<θ <0 .15° limits θ <0 .05° to a DOS that is essentially that of a superposition DOS of all bilayer stacking possibilities. In this regime, the Dirac spectrum is entirely destroyed by hybridization for -0.25

  5. Study on astrophysical reactions using low-energy RI beams

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Hidetoshi

    2009-10-01

    In recent years, low-energy RI beams can be produced in a good intensity and they have been used for studying many astrophysical reactions. One of the facilities producing low-energy RI beams is CRIB (CNS Radio-Isotope Beam separator) [1,2], an RI-beam separator of Center for Nuclear Study, University of Tokyo. Taking CRIB as an example, recent improvements on the RI-beam production and experimental results on astrophysical studies are presented. Several experimental approaches have been taken for the studies on astrophysical reactions.The feature of each method are discussed based on real measurements performed at CRIB. One is the direct method, applied for measurements of reactions such as (α,p) [3]. Another is the measurement of proton/alpha resonance scattering using the thick target method in inverse kinematics, by which we can obtain information on the resonances relevant in astrophysical reactions [4,5]. A recent fruitful result was from a measurement of proton resonance scattering using a ^7Be beam [5]. The energy level structure of ^8B, revealed by the experiment, is especially of interest as it is related with the ^7Be(p,γ) ^8B reaction, responsible for the production of ^8B neutrinos in the sun. We successfully determined parameters of resonances in ^8B below 6.7 MeV, which may affect the ^7Be(p,γ)^8B reaction rate at the solar temparature. Indirect methods, such as ANC and the Trojan Horse Method, were also used in some of the measurements.[4pt] [1] S. Kubono et al., Eur. Phys. J. A13 (2002) 217.[0pt] [2] Y. Yanagisawa et al., Nucl. Instrum. Meth. Phys. Res., Sect. A 539 (2005) 74.[0pt] [3] M. Notani et al., Nucl. Phys. A 764 (2004) 113c.[0pt] [4] T. Teranishi et al., Phys. Lett. B 650 (2007) 129.[0pt] [5] H. Yamaguchi et al., Phys. Lett. B 672 (2009) 230.

  6. Testing SO(10)-inspired leptogenesis with low energy neutrino experiments

    SciTech Connect

    Bari, Pasquale Di; Riotto, Antonio E-mail: Antonio.Riotto@cern.ch

    2011-04-01

    We extend the results of a previous analysis of ours showing that, when both heavy and light flavour effects are taken into account, successful minimal (type I + thermal) leptogenesis with SO(10)-inspired relations is possible. Barring fine tuned choices of the parameters, these relations enforce a hierarchical RH neutrino mass spectrum that results into a final asymmetry dominantly produced by the next-to-lightest RH neutrino decays (N{sub 2} dominated leptogenesis). We present the constraints on the whole set of low energy neutrino parameters. Allowing a small misalignment between the Dirac basis and the charged lepton basis as in the quark sector, the allowed regions enlarge and the lower bound on the reheating temperature gets relaxed to values as low as ∼ 10{sup 10} GeV. It is confirmed that for normal ordering (NO) there are two allowed ranges of values for the lightest neutrino mass: m{sub 1} ≅ (1−5) × 10{sup −3} eV and m{sub 1} ≅ (0.03−0.1) eV. For m{sub 1}∼<0.01 eV the allowed region in the plane θ{sub 13}-θ{sub 23} is approximately given by θ{sub 23}∼<49°+0.65 (θ{sub 13}−5°), while the neutrinoless double beta decay effective neutrino mass falls in the range m{sub ee} = (1−3) × 10{sup −3} eV for θ{sub 13} = (6°−11.5°). For m{sub 1}∼>0.01 eV, one has quite sharply m{sub ee} ≅ m{sub 1} and an upper bound θ{sub 23}∼<46°. These constraints will be tested by low energy neutrino experiments during next years. We also find that inverted ordering (IO), though quite strongly constrained, is not completely ruled out. In particular, we find approximately θ{sub 23} ≅ 43°+12° log (0.2 eV/m{sub 1}), that will be fully tested by future experiments.

  7. Effect of surface modification by nitrogen ion implantation on the electrochemical and cellular behaviors of super-elastic NiTi shape memory alloy.

    PubMed

    Maleki-Ghaleh, H; Khalil-Allafi, J; Sadeghpour-Motlagh, M; Shakeri, M S; Masoudfar, S; Farrokhi, A; Beygi Khosrowshahi, Y; Nadernezhad, A; Siadati, M H; Javidi, M; Shakiba, M; Aghaie, E

    2014-12-01

    The aim of this investigation was to enhance the biological behavior of NiTi shape memory alloy while preserving its super-elastic behavior in order to facilitate its compatibility for application in human body. The surfaces of NiTi samples were bombarded by three different nitrogen doses. Small-angle X-ray diffraction was employed for evaluating the generated phases on the bombarded surfaces. The electrochemical behaviors of the bare and surface-modified NiTi samples were studied in simulated body fluid (SBF) using electrochemical impedance and potentio-dynamic polarization tests. Ni ion release during a 2-month period of service in the SBF environment was evaluated using atomic absorption spectrometry. The cellular behavior of nitrogen-modified samples was studied using fibroblast cells. Furthermore, the effect of surface modification on super-elasticity was investigated by tensile test. The results showed the improvement of both corrosion and biological behaviors of the modified NiTi samples. However, no significant change in the super-elasticity was observed. Samples modified at 1.4E18 ion cm(-2) showed the highest corrosion resistance and the lowest Ni ion release.

  8. Low-energy neutral-atom imaging techniques

    NASA Astrophysics Data System (ADS)

    Funsten, Herbert O.; McComas, David J.; Scime, Earl E.

    1993-07-01

    The potential scientific return from low energy neutral atom (LENA) imaging of the magnetosphere is extraordinary. The technical challenges of LENA detection include (1) removal of LENAs from the tremendous ambient UV without losing information of their incident trajectories, (2) quantification of their trajectories, and (3) obtaining high sensitivity measurements. Two techniques that have been proposed for this purpose are based on fundamentally different atomic interaction mechanisms between LENAs and a solid: LENA transmission through an ultrathin foil and LENA reflection from a solid surface. Both of these methods provide LENA ionization (for subsequent removal from the UV by electrostatic deflection) and secondary electron emission (for start pulse generation for time-of-flight and/or coincidence). We present a comparative study of the transmission and reflection techniques based on differences in atomic interactions with solids and surfaces. We show that transmission yield an order of magnitude greater secondary electron emission than reflection methods. Transmission methods are shown to be sufficient for LEAN energies of approximately 1 keV to greater than 30 keV.

  9. Symmetry Energy Effects on Low Energy Dissipative Heavy Ion Collisions

    NASA Astrophysics Data System (ADS)

    Rizzo, C.; Baran, V.; Colonna, M.; Di Toro, M.; Odsuren, M.

    2011-02-01

    We investigate the reaction path followed by Heavy Ion Collisions with exotic nuclear beams at low energies. We focus on the interplay between reaction mechanisms, fusion vs. break-up (fast-fission, deep-inelastic), that in exotic systems is expected to be influenced by the symmetry energy term at densities around the normal value. The method described here, based on the event by event evolution of phase space quadrupole collective modes, will nicely allow to extract the fusion probability at relatively early times, when the transport results are reliable. Fusion probabilities for reactions induced by 132Sn on 64,58Ni targets at 10 AMeV are evaluated. We obtain larger fusion cross sections for the more n-rich composite system, and, for a given reaction, with a soft symmetry term above saturation. A collective charge equilibration mechanism (the Dynamical Dipole Resonance, DDR) is revealed in both fusion and break-up events, depending on the stiffness of the symmetry term just below saturation. Finally we investigate the effect of the mass asymmetry in the entrance channel for systems with the same overall isospin content and similar initial charge asymmetry. As expected we find reduced fusion probabilities for the more mass symmetric case, while the DDR strength appears not much affected. This is a nice confirmation of the prompt nature of such collective isovector mode.

  10. The low-energy program of the MAJORANA DEMONSTRATOR

    NASA Astrophysics Data System (ADS)

    Massarczyk, Ralph; MAJORANA Collaboration

    2017-01-01

    The MAJORANA Collaboration constructed an ultra-low background, modular high-purity Ge detector array to search for neutrinoless double-beta decay in 76Ge. Located at the 4850-ft level of the Sanford Underground Research Facility, the DEMONSTRATOR detector assembly has the goal to show that it is possible to achieve background rates necessary for future ton-scale experiments. The ultra-clean assembly in combination with low-noise p-type point contact detectors allows measurements with thresholds in the keV range. The talk will give an overview of the low-energy physics and recent achievements made since the completed DEMONSTRATOR array started data taking in mid 2016. Recent results from campaign will be presented, including new limits on bosonic dark matter interaction rates. This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, the Particle Astrophysics Program of the National Science Foundation, and the Sanford Underground Research Facility. We acknowledge the support of the U.S. Department of Energy through the LANL/LDRD Program.

  11. Seeking to Improve Low Energy Neutral Atom Detection in Space

    NASA Technical Reports Server (NTRS)

    Shappirio, M.; Coplan, M.; Chornay, D.; Collier, M.; Herrero, F.; Ogilvie, K.; Williams, E.

    2007-01-01

    The detection of energetic neutral atoms allows for the remote examination of the interactions between plasmas and neutral populations in space. Before these neutral atoms can be measured, they must first be converted to ions. For the low energy end of this spectrum, interaction with a conversion surface is often the most efficient method to convert neutrals into ions. It is generally thought that the most efficient surfaces are low work functions materials. However, by their very nature, these surfaces are highly reactive and unstable, and therefore are not suitable for space missions where conditions cannot be controlled as they are in a laboratory. We therefore are looking to optimize a stable surface for conversion efficiency. Conversion efficiency can be increased either by changing the incident angle of the neutral particles to be grazing incidence and using stable surfaces with high conversion efficiencies. We have examined how to increase the angle of incidence from -80 degrees to -89 degrees, while maintaining or improving the total active conversion surface area without increasing the overall volume of the instrument. We are developing a method to micro-machine silicon, which will reduce the volume to surface area ratio by a factor of 60. We have also examined the material properties that affect the conversion efficiency of the surface for stable surfaces. Some of the parameters we have examined are work function, smoothness, and bond structure. We find that for stable surfaces, the most important property is the smoothness of the surface.

  12. Low-energy fusion caused by an interference

    NASA Astrophysics Data System (ADS)

    Ivlev, Boris

    2013-04-01

    Fusion of two deuterons of room temperature energy is discussed. The nuclei are in vacuum with no connection to any external source(electric or magnetic field, illumination, surrounding matter, traps, etc.) which may accelerate them. The energy of two nuclei is conserved and remains small during the motion through the Coulomb barrier. The penetration through this barrier, which is the main obstacle for low-energy fusion, strongly depends on a form of the incident flux on the Coulomb center at large distances from it. In contrast to the usual scattering, the incident wave is not a single plane wave but the certain superposition of plane waves of the same energy and various directions, for example, a conergent conical wave. The wave function close to the Coulomb center is determined by cusp caustic which is probed by de Broglie waves. The particle flux gets away from the cusp and moves to the Coulomb center providing a not small probability of fusion (cusp driven tunneling). Getting away from a caustic cusp also occurs in optics and acoustics. arXiv:1211.1243

  13. Biophysics behavior of acupuncture points irradiated with low energy lasers.

    PubMed

    Moldovan, C

    2007-01-01

    This work describes the Low Energy Laser (LEL) coherent light interaction with the skin cover on acupuncture loci for the purpose of detecting and measuring the spatial and temporal alteration of the thermal, electric and optical properties of the LI4 (HEGU) acupoint, irradiated with a 685 nm, 30 mW, III.B Laser. Novel electrostatic imaging technique, an original Acupuncture 3-D Thermal and Electric Mapping Technique and an original Method for Laser-Skin Reflectance, were used in the study. The results indicate that the visible laser light, with low frequency and low power, specifically modify the 3-D pattern of the temperature, electric potential and electric impedance outline of an acupuncture point, meanwhile with a significant decrease of the laser reflectance index, all measured on a 27 apparently healthy subject lot (48 years mean age, 54% male), when comparing with a non-active, non-acupunctural skin area, placed on the volar side of the same hand. The biophysical method presented, combines in a complex way and reproducible the electro stasis exploration (bioelectric homeostasis), with cutaneous thermodynamic exploration and photo-optical exploration of the derma and provides information that can be appreciated in dynamics and compared depending on the exploration target.

  14. [Progress of low-energy shockwave therapy in clinical application].

    PubMed

    Xin, Zhong-cheng; Liu, Jing; Wang, Lin; Li, Hui-xi

    2013-08-18

    A shock wave is a transient pressure disturbance that propagates rapidly in three-dimensional space. It is associated with a sudden rise from ambient pressure to its maximum pressure. Shock wave therapy in urology is primarily used to disintegrate urolithiasis. Recently, low-energy shock wave therapy (LESWT), which is a novel convenient and cost-effective therapeutic modality, is extended to treat other pathological conditions including coronary heart disease, musculoskeletal disorders and erectile dysfunction. However, the exact therapeutic mechanisms and clinical safety and efficacy of LESWT remain to be investigated. Based on the results of previous studies, it is suggested that LESWT could regulate angiogenesis-related growth factors expression including endothelial nitric oxide synthase (eNOS), vessel endothelial growth factor (VEGF) and proliferating cell nuclear antigen (PCNA), which might induce the ingrowth of neovascularization that improves blood supply and increases cell proliferation and eventual tissue regeneration for restore pathological changes. The further studies on cellular and molecular biological changes by LESWT for clarification its mechanism and clinical safety and efficacy studies are recommended.

  15. Vacancy-Induced Low-Energy States in Undoped Graphene

    NASA Astrophysics Data System (ADS)

    Sanyal, Sambuddha; Damle, Kedar; Motrunich, Olexei I.

    2016-09-01

    We demonstrate that a nonzero concentration nv of static, randomly placed vacancies in graphene leads to a density w of zero-energy quasiparticle states at the band center ɛ =0 within a tight-binding description with nearest-neighbor hopping t on the honeycomb lattice. We show that w remains generically nonzero in the compensated case (exactly equal number of vacancies on the two sublattices) even in the presence of hopping disorder and depends sensitively on nv and correlations between vacancy positions. For low, but not-too-low, |ɛ |/t in this compensated case, we show that the density of states ρ (ɛ ) exhibits a strong divergence of the form ρDyson(ɛ )˜|ɛ |-1/[log (t /|ɛ |)](y+1 ), which crosses over to the universal low-energy asymptotic form (modified Gade-Wegner scaling) expected on symmetry grounds ρGW(ɛ )˜|ɛ |-1e-b [log (t /|ɛ |)]2/3 below a crossover scale ɛc≪t . ɛc is found to decrease rapidly with decreasing nv, while y decreases much more slowly.

  16. Collisions of low-energy electrons with cyclohexane

    SciTech Connect

    Barbosa, Alessandra Souza; Bettega, Márcio H. F.

    2014-12-28

    We report calculated cross sections for elastic scattering of low-energy electrons by cyclohexane (c-C{sub 6}H{sub 12}). We employed the Schwinger multichannel method implemented with norm-conserving pseudopotentials in the static-exchange and static-exchange plus polarization approximations, for impact energies up to 30 eV. We compare our calculated integral cross section with experimental total cross sections available in the literature. We also compare our calculated differential cross sections (DCSs) with experimental results for benzene and experimental and theoretical results for 1,4-dioxane, in order to investigate the similarities between those molecules under electron collisions. Although benzene is a cyclic six-carbon molecule, as cyclohexane, we found that the differential cross sections of the latter are more similar to those of 1,4-dioxane than those of benzene. These similarities suggest that the geometry may play an important role in the behavior of the DCSs of these molecules. Our integral cross section displays a broad structure at around 8.5 eV, in agreement with the total cross section experimental data of 8 eV and vibrational excitation data of 7.5 eV. The present integral cross section also shows the presence of a Ramsauer-Townsend minimum at around 0.12 eV. In general, our integral cross section shows a qualitative agreement with the experimental total cross section.

  17. Very Low Energy Electron Scattering from Ozone and Chlorine Dioxide

    NASA Astrophysics Data System (ADS)

    Gulley, R. J.; Field, T. A.; Steer, W. A.; Mason, N. J.; Ziesel, J. P.; Lunt, S. L.; Field, D.

    1998-10-01

    Total cross-sections are reported for the scattering of electrons from ozone (O_3) and chlorine dioxide (OClO) for energies in the range of 9 meV to 10 eV. The measurements were made in transmission experiments using a synchrotron photoionization apparatus with an energy resolution in the incident electron beam of ~ 3.5 meV (FWHM). The cross section for O3 shows strong rotational scattering at low energy, through the presence of the permanent dipole moment of O_3. Superposed on this strong scattering signal, there is evidence of a weak structure around 50 meV associated with dissociative attachment. A shape resonance, known from earlier work at ~ 4 meV, is also observed. Electron scattering from OClO is dominated by rotationally inelastic scattering decreasing from a peak at essentially zero eV to an energy of 40 meV, where p-wave attachment becomes more important, peaking at 50--60 meV and extending to several hundred meV.

  18. Addressing Kitchen Contaminants for Healthy, Low-Energy Homes

    SciTech Connect

    Stratton, J. Chris; Singer, Brett C.

    2014-01-01

    Cooking and cooking burners emit pollutants that can adversely affect indoor air quality in residences and significantly impact occupant health. Effective kitchen exhaust ventilation can reduce exposure to cooking-related air pollutants as an enabling step to healthier, low-energy homes. This report by Lawrence Berkeley National Laboratory identifies barriers to the widespread adoption of kitchen exhaust ventilation technologies and practice and proposes a suite of strategies to overcome these barriers. The recommendations have been vetted by a group of industry, regulatory, health, and research experts and stakeholders who convened for two meetings and provided input and feedback to early drafts of this document. The most fundamental barriers are (1) the common misconception, based on a sensory perception of risk, that kitchen exhaust when cooking is unnecessary and (2) the lack of a code requirement for kitchen ventilation in most U.S. locations. Highest priority objectives include the following: (1) Raise awareness among the public and the building industry of the need to install and routinely use kitchen ventilation; (2) Incorporate kitchen exhaust ventilation as a requirement of building codes and improve the mechanisms for code enforcement; (3) Provide best practice product and use-behavior guidance to ventilation equipment purchasers and installers, and; (4) Develop test methods and performance targets to advance development of high performance products. A specific, urgent need is the development of an over-the-range microwave that meets the airflow and sound requirements of ASHRAE Standard 62.2.

  19. Review of lattice results concerning low-energy particle physics

    SciTech Connect

    Aoki, S.; Aoki, Y.; Bernard, C.; Blum, T.; Colangelo, G.; Della Morte, M.; Dürr, S.; El-Khadra, A. X.; Fukaya, H.; Horsley, R.; Jüttner, A.; Kaneko, T.; Laiho, J.; Lellouch, L.; Leutwyler, H.; Lubicz, V.; Lunghi, E.; Necco, S.; Onogi, T.; Pena, C.; Sachrajda, C. T.; Sharpe, S. R.; Simula, S.; Sommer, R.; Van de Water, R. S.; Vladikas, A.; Wenger, U.; Wittig, H.

    2014-09-01

    We review lattice results related to pion, kaon, D- and B-meson physics with the aim of making them easily accessible to the particle physics community. More specifically, we report on the determination of the light-quark masses, the form factor f+(0), arising in semileptonic K -> pi transition at zero momentum transfer, as well as the decay constant ratio fK/fpi of decay constants and its consequences for the CKM matrix elements Vus and Vud. Furthermore, we describe the results obtained on the lattice for some of the low-energy constants of SU(2)LxSU(2)R and SU(3)LxSU(3)R Chiral Perturbation Theory and review the determination of the BK parameter of neutral kaon mixing. The inclusion of heavy-quark quantities significantly expands the FLAG scope with respect to the previous review. Therefore, for this review, we focus on D- and B-meson decay constants, form factors, and mixing parameters, since these are most relevant for the determination of CKM matrix elements and the global CKM unitarity-triangle fit. In addition we review the status of lattice determinations of the strong coupling constant alpha_s.

  20. Photon strength and the low-energy enhancement

    NASA Astrophysics Data System (ADS)

    Wiedeking, M.; Bernstein, L. A.; Krtička, M.; Bleuel, D. L.; Allmond, J. M.; Basunia, M. S.; Burke, J. T.; Fallon, P.; Firestone, R. B.; Goldblum, B. L.; Hatarik, R.; Lake, P. T.; Lee, I.-Y.; Lesher, S. R.; Paschalis, S.; Petri, M.; Phair, L.; Scielzo, N. D.

    2014-08-01

    Several measurements in medium mass nuclei have reported a low-energy enhancement in the photon strength function. Although, much effort has been invested in unraveling the mysteries of this effect, its physical origin is still not conclusively understood. Here, a completely model-independent experimental approach to investigate the existence of this enhancement is presented. The experiment was designed to study statistical feeding from the quasi-continuum (below the neutron separation energy) to individual low-lying discrete levels in 95Mo produced in the (d, p) reaction. A key aspect to successfully study gamma decay from the region of high-level density is the detection and extraction of correlated particle-gamma-gamma events which was accomplished using an array of Clover HPGe detectors and large area annular silicon detectors. The entrance channel excitation energy into the residual nucleus produced in the reaction was inferred from the detected proton energies in the silicon detectors. Gating on gamma-transitions originating from low-lying discrete levels specifies the state fed by statistical gamma-rays. Any particle-gamma-gamma event in combination with specific energy sum requirements ensures a clean and unambiguous determination of the initial and final state of the observed gamma rays. With these requirements the statistical feeding to individual discrete levels is extracted on an event-by-event basis. The results are presented and compared to 95Mo photon strength function data measured at the University of Oslo.

  1. Collisions of low-energy electrons with formamide

    NASA Astrophysics Data System (ADS)

    Bettega, Márcio H. F.

    2010-06-01

    We present integral and momentum transfer cross sections for elastic scattering of low-energy electrons by formamide (HCONH2) from 1 to 12 eV. To calculate the cross sections we employed the Schwinger multichannel method with pseudopotentials in the static-exchange and in the static-exchange-polarization approximations. We found a π* shape resonance belonging to the A″ symmetry which is located at around 4.5 eV in the static-exchange approximation, and at around 2.5 eV in the static-exchange-polarization approximation. This result is in close agreement with the observations of Seydou [Eur. Phys. J. DEPJDF61434-606010.1140/epjd/e2005-00089-5 35, 199 (2005)] which reported the value of 2.05 eV to the vertical electron attachment energy, and is lower than the value of 3.77 eV computed by Goumans [J. Chem. Theory Comp.JPCBFK1549-961810.1021/ct800379h 5, 217 (2009)]. We carried out additional minimal basis set electronic structure calculations to help in the interpretation of our results. Our results support the conclusions of Goumans , namely, that this resonance may initiate the indirect dissociation mechanism of formamide by electron impact.

  2. Addressing Kitchen Contaminants for Healthy, Low-Energy Homes

    SciTech Connect

    Stratton, J. Chris; Singer, Brett C.

    2014-01-01

    Cooking and cooking burners emit pollutants that can adversely affect indoor air quality in residences and significantly impact occupant health. Effective kitchen exhaust ventilation can reduce exposure to cooking-related air pollutants as an enabling step to healthier, low-energy homes. This report identifies barriers to the widespread adoption of kitchen exhaust ventilation technologies and practice and proposes a suite of strategies to overcome these barriers. The recommendations have been vetted by a group of industry, regulatory, health, and research experts and stakeholders who convened for two web-based meetings and provided input and feedback to early drafts of this document. The most fundamental barriers are (1) the common misconception, based on a sensory perception of risk, that kitchen exhaust when cooking is unnecessary and (2) the lack of a code requirement for kitchen ventilation in most US locations. Highest priority objectives include the following: (1) Raise awareness among the public and the building industry of the need to install and routinely use kitchen ventilation; (2) Incorporate kitchen exhaust ventilation as a requirement of building codes and improve the mechanisms for code enforcement; (3) Provide best practice product and use-behavior guidance to ventilation equipment purchasers and installers, and; (4) Develop test methods and performance targets to advance development of high performance products. A specific, urgent need is the development of an over-the-range microwave that meets the airflow and sound requirements of ASHRAE Standard 62.2.

  3. Maximum Likelihood Analysis of Low Energy CDMS II Germanium Data

    DOE PAGES

    Agnese, R.

    2015-03-30

    We report on the results of a search for a Weakly Interacting Massive Particle (WIMP) signal in low-energy data of the Cryogenic Dark Matter Search experiment using a maximum likelihood analysis. A background model is constructed using GEANT4 to simulate the surface-event background from Pb210decay-chain events, while using independent calibration data to model the gamma background. Fitting this background model to the data results in no statistically significant WIMP component. In addition, we also perform fits using an analytic ad hoc background model proposed by Collar and Fields, who claimed to find a large excess of signal-like events in ourmore » data. Finally, we confirm the strong preference for a signal hypothesis in their analysis under these assumptions, but excesses are observed in both single- and multiple-scatter events, which implies the signal is not caused by WIMPs, but rather reflects the inadequacy of their background model.« less

  4. Review of lattice results concerning low-energy particle physics

    DOE PAGES

    Aoki, S.; Aoki, Y.; Bernard, C.; ...

    2014-09-01

    We review lattice results related to pion, kaon, D- and B-meson physics with the aim of making them easily accessible to the particle physics community. More specifically, we report on the determination of the light-quark masses, the form factor f+(0), arising in semileptonic K -> pi transition at zero momentum transfer, as well as the decay constant ratio fK/fpi of decay constants and its consequences for the CKM matrix elements Vus and Vud. Furthermore, we describe the results obtained on the lattice for some of the low-energy constants of SU(2)LxSU(2)R and SU(3)LxSU(3)R Chiral Perturbation Theory and review the determination ofmore » the BK parameter of neutral kaon mixing. The inclusion of heavy-quark quantities significantly expands the FLAG scope with respect to the previous review. Therefore, for this review, we focus on D- and B-meson decay constants, form factors, and mixing parameters, since these are most relevant for the determination of CKM matrix elements and the global CKM unitarity-triangle fit. In addition we review the status of lattice determinations of the strong coupling constant alpha_s.« less

  5. Evolving landscape of low-energy nuclear physics publications

    SciTech Connect

    Pritychenko, B.

    2016-10-01

    Evolution of low-energy nuclear physics publications over the last 120 years has been analyzed using nuclear physics databases. An extensive study of Nuclear Science References, Experimental Nuclear Reaction Data (EXFOR), and Evaluated Nuclear Structure Data File (ENSDF) contents provides a unique picture of refereed and non-refereed nuclear physics references. Significant fractional contributions of non-refereed reports, private communications and conference proceedings in EXFOR and ENSDF databases in the 1970’s reflect extensive experimental campaigns and an insufficient number of research journals. This trend has been reversed in recent years because the number of measurements is much lower, while number of journals is higher. In addition, nuclear physics results are mainly published in a limited number of journals, such as Physical Review C and Nuclear Physics A. In the present work, historic publication trends and averages have been extracted and analyzed using nuclear data mining techniques. Lastly, the results of this study and implications are discussed and conclusions presented.

  6. Evolving landscape of low-energy nuclear physics publications

    DOE PAGES

    Pritychenko, B.

    2016-10-01

    Evolution of low-energy nuclear physics publications over the last 120 years has been analyzed using nuclear physics databases. An extensive study of Nuclear Science References, Experimental Nuclear Reaction Data (EXFOR), and Evaluated Nuclear Structure Data File (ENSDF) contents provides a unique picture of refereed and non-refereed nuclear physics references. Significant fractional contributions of non-refereed reports, private communications and conference proceedings in EXFOR and ENSDF databases in the 1970’s reflect extensive experimental campaigns and an insufficient number of research journals. This trend has been reversed in recent years because the number of measurements is much lower, while number of journals ismore » higher. In addition, nuclear physics results are mainly published in a limited number of journals, such as Physical Review C and Nuclear Physics A. In the present work, historic publication trends and averages have been extracted and analyzed using nuclear data mining techniques. Lastly, the results of this study and implications are discussed and conclusions presented.« less

  7. A new look at low-energy nuclear reaction research.

    PubMed

    Krivit, Steven B; Marwan, Jan

    2009-10-01

    This paper presents a new look at low-energy nuclear reaction research, a field that has developed from one of the most controversial subjects in science, "cold fusion." Early in the history of this controversy, beginning in 1989, a strong polarity existed; many scientists fiercely defended the claim of new physical effects as well as a new process in which like-charged atomic nuclei overcome the Coulomb barrier at normal temperatures and pressures. Many other scientists considered the entire collection of physical observations-along with the hypothesis of a "cold fusion"--entirely a mistake. Twenty years later, some people who had dismissed the field in its entirety are considering the validity of at least some of the reported experimental phenomena. As well, some researchers in the field are wondering whether the underlying phenomena may be not a fusion process but a neutron capture/absorption process. In 2002, a related tabletop form of thermonuclear fusion was discovered in the field of acoustic inertial confinement fusion. We briefly review some of this work, as well.

  8. Low-energy electron scattering by cellulose and hemicellulose components.

    PubMed

    de Oliveira, Eliane M; da Costa, Romarly F; Sanchez, Sergio d'A; Natalense, Alexandra P P; Bettega, Márcio H F; Lima, Marco A P; Varella, Márcio T do N

    2013-02-07

    We report elastic integral, differential and momentum transfer cross sections for low-energy electron scattering by the cellulose components β-D-glucose and cellobiose (β(1 → 4) linked glucose dimer), and the hemicellulose component β-D-xylose. For comparison with the β forms, we also obtain results for the amylose subunits α-D-glucose and maltose (α(1 → 4) linked glucose dimer). The integral cross sections show double peaked broad structures between 8 eV and 20 eV similar to previously reported results for tetrahydrofuran and 2-deoxyribose, suggesting a general feature of molecules containing furanose and pyranose rings. These broad structures would reflect OH, CO and/or CC σ* resonances, where inspection of low-lying virtual orbitals suggests significant contribution from anion states. Though we do not examine dissociation pathways, these anion states could play a role in dissociative electron attachment mechanisms, in case they were coupled to the long-lived π* anions found in lignin subunits [de Oliveira et al., Phys. Rev. A, 2012, 86, 020701(R)]. Altogether, the resonance spectra of lignin, cellulose and hemicellulose components establish a physical-chemical basis for electron-induced biomass pretreatment that could be applied to biofuel production.

  9. Vacuum polarization corrections to low energy quark effective couplings

    NASA Astrophysics Data System (ADS)

    Paulo, Ademar; Braghin, Fabio L.

    2014-07-01

    In this work corrections to low energy punctual effective quark couplings up to the eighth order are calculated by considering vacuum polarization effects with the scalar quark-antiquark condensate. The departing point is a QCD-based Nambu-Jona-Lasinio model. By separating the quark field into two components, one that condenses and another one for interacting quarks, the former is integrated out with the help of usual auxiliary fields and an effective action in terms of interacting quark fields is found. The scalar auxiliary field reduces to the quark-antiquark condensate in the vacuum and the determinant is expanded in powers of the quark-antiquark bilinears generating chiral invariant effective 2N-quark interactions (N =2,3…). The corresponding coupling constants and effective masses are estimated, and the general trend is that for increasing the effective gluon mass the values of the effective coupling constants decrease. All the values are in good agreement with phenomenological fits.

  10. Low energy, high power hydrogen neutral beam for plasma heating

    SciTech Connect

    Deichuli, P.; Davydenko, V.; Ivanov, A. Mishagin, V.; Sorokin, A.; Stupishin, N.; Korepanov, S.; Smirnov, A.

    2015-11-15

    A high power, relatively low energy neutral beam injector was developed to upgrade of the neutral beam system of the gas dynamic trap device and C2-U experiment. The ion source of the injector produces a proton beam with the particle energy of 15 keV, current of up to 175 A, and pulse duration of a few milliseconds. The plasma emitter of the ion source is produced by superimposing highly ionized plasma jets from an array of four arc-discharge plasma generators. A multipole magnetic field produced with permanent magnets at the periphery of the plasma box is used to increase the efficiency and improve the uniformity of the plasma emitter. Multi-slit grids with 48% transparency are fabricated from bronze plates, which are spherically shaped to provide geometrical beam focusing. The focal length of the Ion Optical System (IOS) is 3.5 m and the initial beam diameter is 34 cm. The IOS geometry and grid potentials were optimized numerically to ensure accurate beam formation. The measured angular divergences of the beam are ±0.01 rad parallel to the slits and ±0.03 rad in the transverse direction.

  11. Review of lattice results concerning low-energy particle physics.

    PubMed

    Aoki, S; Aoki, Y; Bernard, C; Blum, T; Colangelo, G; Della Morte, M; Dürr, S; El-Khadra, A X; Fukaya, H; Horsley, R; Jüttner, A; Kaneko, T; Laiho, J; Lellouch, L; Leutwyler, H; Lubicz, V; Lunghi, E; Necco, S; Onogi, T; Pena, C; Sachrajda, C T; Sharpe, S R; Simula, S; Sommer, R; Van de Water, R S; Vladikas, A; Wenger, U; Wittig, H

    We review lattice results related to pion, kaon, [Formula: see text]- and [Formula: see text]-meson physics with the aim of making them easily accessible to the particle-physics community. More specifically, we report on the determination of the light-quark masses, the form factor [Formula: see text], arising in semileptonic [Formula: see text] transition at zero momentum transfer, as well as the decay-constant ratio [Formula: see text] of decay constants and its consequences for the CKM matrix elements [Formula: see text] and [Formula: see text]. Furthermore, we describe the results obtained on the lattice for some of the low-energy constants of [Formula: see text] and [Formula: see text] Chiral Perturbation Theory and review the determination of the [Formula: see text] parameter of neutral kaon mixing. The inclusion of heavy-quark quantities significantly expands the FLAG scope with respect to the previous review. Therefore, we focus here on [Formula: see text]- and [Formula: see text]-meson decay constants, form factors, and mixing parameters, since these are most relevant for the determination of CKM matrix elements and the global CKM unitarity-triangle fit. In addition we review the status of lattice determinations of the strong coupling constant [Formula: see text].

  12. Radiochromic film dosimetry of a low energy proton beam.

    PubMed

    Piermattei, A; Miceli, R; Azario, L; Fidanzio, A; delle Canne, S; De Angelis, C; Onori, S; Pacilio, M; Petetti, E; Raffaele, L; Sabini, M G

    2000-07-01

    In this work some dosimetric characteristics of MD-55-2 GafChromic films were studied in a low energy proton beam (21.5 MeV) directly in a water phantom. The nonlinearity of the optical density was quantified by a factor P(lin). A correction factor P(en), that accounts for optical density dependence on the energy, was empirically determined. The effects of detector thickness in depth dose measurements and of the film orientation with respect to beam direction were investigated. The results show that the MD-55-2 films provide dose measurements with the films positioned perpendicularly to the proton beam. A dosimetric formalizm is proposed to determine the dose to water at depth d, with films oriented perpendicularly to the beam axis. This formalism uses a calibration factor of the radiochromic film determined directly on the proton beam at a reference depth in water, and the P(lin) factor, that takes into account the nonlinearity of the calibration curve and the P(en) factor that, in turn takes into account the change of proton beam energy in water. The MD-55-2 films with their high spatial resolution and the quasiwater equivalent material are attractive, positioned perpendicularly along the beam axis, for the absolute dose determination of very small beam sizes and modulated proton beams.

  13. Low energy electrons and swift ion track structure in PADC

    SciTech Connect

    Fromm, Michel; Quinto, Michele A.; Weck, Philippe F.; Champion, Christophe

    2015-05-27

    The current work aims at providing an accurate description of the ion track-structure in poly-allyl dyglycol carbonate (PADC) by using an up-to-date Monte-Carlo code-called TILDA-V (a French acronym for Transport d’Ions Lourds Dans l’Aqua & Vivo). In this simulation the ion track-structure in PADC is mainly described in terms of ejected electrons with a particular attention done to the Low Energy Electrons (LEEs). After a brief reminder of the most important channels through which LEEs are prone to break a chemical bond, we will report on the simulated energetic distributions of LEEs along an ion track in PADC for particular incident energies located on both sides of the Bragg-peak position. Lastly, based on the rare data dealing with LEEs interaction with polymers or organic molecules, we will emphasise the role played by the LEEs in the formation of a latent track in PADC, and more particularly the one played by the sub-ionization electrons.

  14. Electronic excitation of molecular hydrogen by low-energy electrons

    NASA Astrophysics Data System (ADS)

    Hargreaves, Leigh

    2016-09-01

    Molecular hydrogen is the most abundant element in the universe, particularly in interstellar plasmas such as atmospheres of gas giant planets and stars. Electron collision data for hydrogen is critical to interpreting the spectroscopy of interstellar objects, as well as being of applied value for modelling technological plasmas. Hydrogen is also fundamentally interesting, as while highly accurate wave functions for this simple molecule are available, providing an accurate, ab initio, treatment the collision dynamics has proven challenging, on account of the need to have a complete description of channel coupling and polarization effects. To date, no single theoretical approach has been able to replicate experimental results across all transitions and incident energies, while the experimental database that is available is far from complete and not all available measurements are in satisfactory agreement. In this talk, we present differential and integral cross section measurements for electronic excitation cross sections for molecular hydrogen by low-energy electron impact. The data were measured at incident energies below 20eV, using a well-tested crossed beam apparatus and employing a moveable gas source approach to ensure that background contributions to the scattering are accurately accounted for. These measurements are compared with new theoretical results employing the convergent close coupling approach.

  15. Low-energy gamma ray attenuation characteristics of aviation fuels

    NASA Technical Reports Server (NTRS)

    Singh, Jag J.; Shen, Chih-Ping; Sprinkle, Danny R.

    1990-01-01

    Am241 (59.5 keV) gamma ray attenuation characteristics were investigated in 270 aviation fuel (Jet A and Jet A-1) samples from 76 airports around the world as a part of world wide study to measure the variability of aviation fuel properties as a function of season and geographical origin. All measurements were made at room temperature which varied from 20 to 27 C. Fuel densities (rho) were measured concurrently with their linear attenuation coefficients (mu), thus providing a measure of mass attenuation coefficient (mu/rho) for the test samples. In 43 fuel samples, rho and mu values were measured at more than one room temperature, thus providing mu/rho values for them at several temperatures. The results were found to be independent of the temperature at which mu and rho values were measured. It is noted that whereas the individual mu and rho values vary considerably from airport to airport as well as season to season, the mu/rho values for all samples are constant at 0.1843 + or - 0.0013 cu cm/gm. This constancy of mu/rho value for aviation fuels is significant since a nuclear fuel quantity gauging system based on low energy gamma ray attenuation will be viable throughout the world.

  16. Surface analysis of catalysts by low-energy ion scattering

    NASA Astrophysics Data System (ADS)

    Vanleerdam, Gerrit Cornelis

    1991-01-01

    The characterization of catalyst surfaces using Low Energy Ion Scattering (LEIS) is described. The structure of a catalyst is generally described in conjunction with the different spectroscopic techniques used to characterize them. LEIS is discussed in detail. The importance of the different mechanisms for a number of elements is discussed and related to the total shape of a LEIS spectrum. The consequences for quantitative surface composition analysis are addressed. The absence of signals for tetragonally coordinated cations in the surface of gamma Al2O3 is argued to be due to the preferential exposure of crystallographic planes which contain exclusively octahedral sites. The insight makes it possible to propose a detailed model for the surface structure of gamma Al2O3 and the position of deposited metaloxides there upon. The location of molybdenum strongly depends on the amount deposited and the calcination temperature. The addition of lanthanum making gamma Al2O3 more thermostable is investigated. A series of silica supported molybdenum oxide catalysts is investigated toexplain the remarkable behavior to the selective oxidation of ammonia.

  17. Projectile - Mass asymmetry systematics for low energy incomplete fusion

    NASA Astrophysics Data System (ADS)

    Singh, Pushpendra P.; Yadav, Abhishek; Sharma, Vijay R.; Sharma, Manoj K.; Kumar, Pawan; Sahoo, Rudra N.; Kumar, R.; Singh, R. P.; Muralithar, S.; Singh, B. P.; Bhowmik, R. K.; Prasad, R.

    2015-06-01

    In the present work, low energy incomplete fusion (ICF) in which only a part of projectile fuses with target nucleus has been investigated in terms of various entrance channel parameters. The ICF strength function has been extracted from the analysis of experimental excitation functions (EFs) measured for different projectile-target combinations from near- to well above- barrier energies in 12C,16O(from 1.02Vb to 1.64Vb)+169Tm systems. Experimental EFs have been analysed in the framework statistical model code PACE4 based on the idea of equilibrated compound nucleus decay. It has been found that the value of ICF fraction (FICF) increases with incident projectile energy. A substantial fraction of ICF (FICF ≈ 7 %) has been accounted even at energy as low as ≈ 7.5% above the barrier (at relative velocity νrel ≈0.027) in 12C+169Tm system, and FICF ≈ 10 % at νrel ≈0.014 in 16O+169Tm system. The probability of ICF is discussed in light of the Morgenstern's mass-asymmetry systematics. The value of FICF for 16O+169Tm systems is found to be 18.3 % higher than that observed for 12C+169Tm systems. Present results together with the re-analysis of existing data for nearby systems conclusively demonstrate strong competition of ICF with CF even at slightly above barrier energies, and strong projectile dependence that seems to supplement the Morgenstern's systematics.

  18. Low energy electrons and swift ion track structure in PADC

    NASA Astrophysics Data System (ADS)

    Fromm, Michel; Quinto, Michele A.; Weck, Philippe F.; Champion, Christophe

    2015-10-01

    The current work aims at providing an accurate description of the ion track-structure in poly-allyl dyglycol carbonate (PADC) by using an up-to-date Monte-Carlo code-called TILDA-V (a French acronym for Transport d'Ions Lourds Dans l'Aqua & Vivo). In this simulation the ion track-structure in PADC is mainly described in terms of ejected electrons with a particular attention done to the Low Energy Electrons (LEEs). After a brief reminder of the most important channels through which LEEs are prone to break a chemical bond, we will report on the simulated energetic distributions of LEEs along an ion track in PADC for particular incident energies located on both sides of the Bragg-peak position. Finally, based on the rare data dealing with LEEs interaction with polymers or organic molecules, we will emphasise the role played by the LEEs in the formation of a latent track in PADC, and more particularly the one played by the sub-ionization electrons.

  19. Foil optimization for low energy neutral atom imaging

    SciTech Connect

    Funsten, H.O.; McComas, D.J.; Barraclough, B.L.

    1992-01-01

    Magnetospheric imaging has been proposed using remote detection of low energy neutral atoms (LENAs) of magnetospheric origin. In the detector, LENAs can be removed from the immense ambient EUV by charge modification (ionization) using a carbon stripping foil and can be subsequently deflected into an E/q analysis section. The detector sensitivity efficiency of LENAs is highly dependent on the ionization probability of neutrals as they transit the carbon foil. In this study, we present equilibrium charge state distributions and scatter distributions for 1-30 keV atomic hydrogen and oxygen transiting 0.5 {mu}g cm{sup {minus}2} carbon foils. The fraction of hydrogen exiting a foil as H{sup +} ranges from approximately 5% at 1 keV to 41% at 30 keV. The fraction of oxygen exiting the foil as O{sup +} ranges from 2% at 10 keV to 8% at 30 keV. Results obtained after coating the exit surface of foils with either aluminum (which forms aluminum oxide when exposed to air) or gold suggests that the exit surface chemistry has no effect on the charge state distributions due to foil contamination from exposure to air. Scattering resulting from the atom-foil interaction is shown to be independent of the charge state distribution, suggesting that the interaction mechanisms resulting in charge exchange and scattering are distinctly different.

  20. Low-energy Cathodoluminescence for (Oxy)Nitride Phosphors

    PubMed Central

    Cho, Yujin; Dierre, Benjamin; Sekiguchi, Takashi; Suehiro, Takayuki; Takahashi, Kohsei; Takeda, Takashi; Xie, Rong-Jun; Yamamoto, Yoshinobu; Hirosaki, Naoto

    2016-01-01

    Nitride and oxynitride (Sialon) phosphors are good candidates for the ultraviolet and visible emission applications. High performance, good stability and flexibility of their emission properties can be achieved by controlling their composition and dopants. However, a lot of work is still required to improve their properties and to reduce the production cost. A possible approach is to correlate the luminescence properties of the Sialon particles with their local structural and chemical environment in order to optimize their growth parameters and find novel phosphors. For such a purpose, the low-voltage cathodoluminescence (CL) microscopy is a powerful technique. The use of electron as an excitation source allows detecting most of the luminescence centers, revealing their luminescence distribution spatially and in depth, directly comparing CL results with the other electron-based techniques, and investigating the stability of their luminescence properties under stress. Such advantages for phosphors characterization will be highlighted through examples of investigation on several Sialon phosphors by low-energy CL. PMID:27911365

  1. A compact, versatile low-energy electron beam ion source

    SciTech Connect

    Zschornack, G.; König, J.; Schmidt, M.; Thorn, A.

    2014-02-15

    A new compact Electron Beam Ion Source, the Dresden EBIT-LE, is introduced as an ion source working at low electron beam energies. The EBIT-LE operates at an electron energy ranging from 100 eV to some keV and can easily be modified to an EBIT also working at higher electron beam energies of up to 15 keV. We show that, depending on the electron beam energy, electron beam currents from a few mA in the low-energy regime up to about 40 mA in the high-energy regime are possible. Technical solutions as well as first experimental results of the EBIT-LE are presented. In ion extraction experiments, a stable production of low and intermediate charged ions at electron beam energies below 2 keV is demonstrated. Furthermore, X-ray spectroscopy measurements confirm the possibility of using the machine as a source of X-rays from ions excited at low electron energies.

  2. A compact, versatile low-energy electron beam ion source.

    PubMed

    Zschornack, G; König, J; Schmidt, M; Thorn, A

    2014-02-01

    A new compact Electron Beam Ion Source, the Dresden EBIT-LE, is introduced as an ion source working at low electron beam energies. The EBIT-LE operates at an electron energy ranging from 100 eV to some keV and can easily be modified to an EBIT also working at higher electron beam energies of up to 15 keV. We show that, depending on the electron beam energy, electron beam currents from a few mA in the low-energy regime up to about 40 mA in the high-energy regime are possible. Technical solutions as well as first experimental results of the EBIT-LE are presented. In ion extraction experiments, a stable production of low and intermediate charged ions at electron beam energies below 2 keV is demonstrated. Furthermore, X-ray spectroscopy measurements confirm the possibility of using the machine as a source of X-rays from ions excited at low electron energies.

  3. Low energy electrons and swift ion track structure in PADC

    DOE PAGES

    Fromm, Michel; Quinto, Michele A.; Weck, Philippe F.; ...

    2015-05-27

    The current work aims at providing an accurate description of the ion track-structure in poly-allyl dyglycol carbonate (PADC) by using an up-to-date Monte-Carlo code-called TILDA-V (a French acronym for Transport d’Ions Lourds Dans l’Aqua & Vivo). In this simulation the ion track-structure in PADC is mainly described in terms of ejected electrons with a particular attention done to the Low Energy Electrons (LEEs). After a brief reminder of the most important channels through which LEEs are prone to break a chemical bond, we will report on the simulated energetic distributions of LEEs along an ion track in PADC for particularmore » incident energies located on both sides of the Bragg-peak position. Lastly, based on the rare data dealing with LEEs interaction with polymers or organic molecules, we will emphasise the role played by the LEEs in the formation of a latent track in PADC, and more particularly the one played by the sub-ionization electrons.« less

  4. DISCO: a low-energy multipurpose beamline at synchrotron SOLEIL.

    PubMed

    Giuliani, Alexandre; Jamme, Frédéric; Rouam, Valérie; Wien, Frank; Giorgetta, Jean-Luc; Lagarde, Bruno; Chubar, Oleg; Bac, Stéphane; Yao, Isabelle; Rey, Solène; Herbeaux, Christian; Marlats, Jean-Louis; Zerbib, Daniel; Polack, François; Réfrégiers, Matthieu

    2009-11-01

    DISCO, a novel low-energy beamline covering the spectrum range from the VUV to the visible, has received its first photons at the French synchrotron SOLEIL. In this article the DISCO design and concept of three experimental stations serving research communities in biology and chemistry are described. Emphasis has been put on high flux generation and preservation of polarization at variable energy resolutions. The three experiments include a completely new approach for microscopy and atmospheric pressure experiments as well as a ;classical' synchrotron radiation circular dichroism station. Preliminary tests of the optical design and technical concept have been made. Theoretical predictions of the beam have been compared with the first images produced by the first photons originating from the large-aperture bending-magnet source. Results are also reported concerning the cold finger used to absorb hard X-ray radiation in the central part of the synchrotron beam and to avoid heavy thermal load on the following optics. Wavelength selection using monochromators with different gratings for each experimental set-up as well as beam propagation and conditioning throughout the optical system are detailed. First photons comply very well with the theoretical calculations.

  5. Low-Energy Elastic Electron Scattering by Atomic Oxygen

    NASA Technical Reports Server (NTRS)

    Zatsarinny O.; Bartschat, K.; Tayal, S. S.

    2006-01-01

    The B-spline R-matrix method is employed to investigate the low-energy elastic electron scattering by atomic oxygen. Flexible non-orthogonal sets of radial functions are used to construct the target description and to represent the scattering functions. A detailed investigation regarding the dependence of the predicted partial and total cross sections on the scattering model and the accuracy of the target description is presented. The predicted angle-integrated elastic cross sections are in good agreement with experiment, whereas significant discrepancies are found in the angle-differential elastic cross sections near the forward direction. .The near-threshold results are found to strongly depend on the treatment of inner-core short-range correlation effects in the target description, as well as on a proper account of the target polarizability. A sharp increase in the elastic cross sections below 1 eV found in some earlier calculations is judged to be an artifact of an unbalanced description of correlation in the N-electron target structure and the (N+l)-electron-collision problems.

  6. Rydberg phases of Hydrogen and low energy nuclear reactions

    NASA Astrophysics Data System (ADS)

    Olafsson, Sveinn; Holmlid, Leif

    2016-03-01

    For over the last 26 years the science of cold fusion/LENR has been researched around the world with slow pace of progress. Modest quantity of excess heat and signatures of nuclear transmutation and helium production have been confirmed in experiments and theoretical work has only resulted in a large flora of inadequate theoretical scenarios. Here we review current state of research in Rydberg matter of Hydrogen that is showing strong signature of nuclear processes. In the presentation experimental behavior of Rydberg matter of hydrogen is described. An extensive collaboration effort of surface physics, catalysis, atomic physics, solid state physics, nuclear physics and quantum information is need to tackle the surprising experimental results that have so far been obtained. Rydberg matter of Hydrogen is the only known state of matter that is able to bring huge collection of protons to so short distances and for so long time that tunneling becomes a reasonable process for making low energy nuclear reactions. Nuclear quantum entanglement can also become realistic process at theses conditions.

  7. Analysis of latency performance of bluetooth low energy (BLE) networks.

    PubMed

    Cho, Keuchul; Park, Woojin; Hong, Moonki; Park, Gisu; Cho, Wooseong; Seo, Jihoon; Han, Kijun

    2014-12-23

    Bluetooth Low Energy (BLE) is a short-range wireless communication technology aiming at low-cost and low-power communication. The performance evaluation of classical Bluetooth device discovery have been intensively studied using analytical modeling and simulative methods, but these techniques are not applicable to BLE, since BLE has a fundamental change in the design of the discovery mechanism, including the usage of three advertising channels. Recently, there several works have analyzed the topic of BLE device discovery, but these studies are still far from thorough. It is thus necessary to develop a new, accurate model for the BLE discovery process. In particular, the wide range settings of the parameters introduce lots of potential for BLE devices to customize their discovery performance. This motivates our study of modeling the BLE discovery process and performing intensive simulation. This paper is focused on building an analytical model to investigate the discovery probability, as well as the expected discovery latency, which are then validated via extensive experiments. Our analysis considers both continuous and discontinuous scanning modes. We analyze the sensitivity of these performance metrics to parameter settings to quantitatively examine to what extent parameters influence the performance metric of the discovery processes.

  8. Local formation of nitrogen-vacancy centers in diamond by swift heavy ions

    NASA Astrophysics Data System (ADS)

    Schwartz, J.; Aloni, S.; Ogletree, D. F.; Tomut, M.; Bender, M.; Severin, D.; Trautmann, C.; Rangelow, I. W.; Schenkel, T.

    2014-12-01

    We exposed nitrogen-implanted diamonds to beams of swift heavy ions (˜1 GeV, ˜4 MeV/u) and find that these irradiations lead directly to the formation of nitrogen vacancy (NV) centers, without thermal annealing. We compare the photoluminescence intensities of swift heavy ion activated NV- centers to those formed by irradiation with low-energy electrons and by thermal annealing. NV- yields from irradiations with swift heavy ions are 0.1 of yields from low energy electrons and 0.02 of yields from thermal annealing. We discuss possible mechanisms of NV center formation by swift heavy ions such as electronic excitations and thermal spikes. While forming NV centers with low efficiency, swift heavy ions could enable the formation of three dimensional NV- assemblies over relatively large distances of tens of micrometers. Further, our results show that NV center formation is a local probe of (partial) lattice damage relaxation induced by electronic excitations from swift heavy ions in diamond.

  9. Local formation of nitrogen-vacancy centers in diamond by swift heavy ions

    SciTech Connect

    Schwartz, J.; Aloni, S.; Ogletree, D. F.; Tomut, M.; Bender, M.; Severin, D.; Trautmann, C.; Rangelow, I. W.; Schenkel, T.

    2014-12-07

    We exposed nitrogen-implanted diamonds to beams of swift heavy ions (∼1 GeV, ∼4 MeV/u) and find that these irradiations lead directly to the formation of nitrogen vacancy (NV) centers, without thermal annealing. We compare the photoluminescence intensities of swift heavy ion activated NV{sup −} centers to those formed by irradiation with low-energy electrons and by thermal annealing. NV{sup −} yields from irradiations with swift heavy ions are 0.1 of yields from low energy electrons and 0.02 of yields from thermal annealing. We discuss possible mechanisms of NV center formation by swift heavy ions such as electronic excitations and thermal spikes. While forming NV centers with low efficiency, swift heavy ions could enable the formation of three dimensional NV{sup −} assemblies over relatively large distances of tens of micrometers. Further, our results show that NV center formation is a local probe of (partial) lattice damage relaxation induced by electronic excitations from swift heavy ions in diamond.

  10. Silicon on sapphire for ion implantation studies

    NASA Technical Reports Server (NTRS)

    Pisciotta, B. P.

    1974-01-01

    Van der Pauw or bridge samples are ultrasonically cut from silicon on sapphire wafers. Contact pad regions are implanted with moderately heavy dose of ions. Ion of interest is implanted into sample; and, before being annealed in vacuum, sample is sealed with sputtered layer of silicon dioxide. Nickel or aluminum is sputtered onto contact pad areas and is sintered in nitrogen atmosphere.

  11. High-speed and low-energy nitride memristors

    DOE PAGES

    Choi, Byung Joon; Torrezan, Antonio C.; Strachan, John Paul; ...

    2016-05-24

    High-performance memristors based on AlN films have been demonstrated, which exhibit ultrafast ON/OFF switching times (≈85 ps for microdevices with waveguide) and relatively low switching current (≈15 μA for 50 nm devices). Physical characterizations are carried out to understand the device switching mechanism, and rationalize speed and energy performance. The formation of an Al-rich conduction channel through the AlN layer is revealed. Here, the motion of positively charged nitrogen vacancies is likely responsible for the observed switching.

  12. Low Energy Solar Neutrino Spectroscopy:. Results from the Borexino Experiment

    NASA Astrophysics Data System (ADS)

    D'Angelo, D.

    2011-03-01

    Till very recent the real-time solar neutrino experiments were detecting the tiny fraction of about 0.01% of the total neutrino flux above some MeV energy, the sub-MeV region remained explored only by radiochemical experiments without spectroscopical capabilities. The Borexino experiment, an unsegmented large volume liquid scintillator detector located in the Gran Sasso National Laboratory in central Italy, is at present the only experiment in the world acquiring the real-time solar neutrino data in the low-energy region, via the elastic scattering on electrons in the target mass. The data taking campaign started in 2007 and rapidly lead to the first independent measurement of the mono-cromatic line of 7Be of the solar neutrino spectrum at 862keV, which is of special interest because of the very loose limits coming from existing experiments. The latest measurement, after 41.3t · yr of exposure, is (49 ± 3stat ± 4syst)c/(day · 100t) and leaves the hypothesis of no oscillation inconsistent with data at 4σ level. It also represents the first direct measurement of the survival probability for solar ν e (P{7 Be}ee = 0.56 ± 0.10) in the vacuum-dominates oscillation regime. Recently Borexino was also able to measure of the 8B solar neutrinos interaction rate down to the threshold energy of 3 MeV, the lowest achieved so far. The inferred electron neutrino flux is Φ {8 B}ES = (2.7 ± 0.4stat ± 0.1syst ) × 106 cm{ - 2} s{ - 1} . The corresponding mean electron neutrino survival probability, is P{8 B}ee = 0.29 ± 0.10 at the effective energy of 8.9 MeV. Both measurements are in good agreement with other existing measurements and with predictions from the SSM in the hypothesis of MSW-LMA oscillation scenario. For the first time, thanks to the unprecedented radio-purity of the Borexino target and construction materials, we confirm with a single detector, the presence of a transition between the low energy vacuum-dominated and the high-energy matter-enhanced solar

  13. Screening in Low Energy Nuclear Reactions of Importance to Astrophysics

    NASA Astrophysics Data System (ADS)

    Miley, George H.; Hora, Heinz; Luo, Nie

    2004-05-01

    Recent experiments in the LUNAR (Laboratory for Underground Nuclear Astrophysics) project have shown anonymously high electron screening may occur during acceleration driven low energy (<400 kV) ion bombardment of solid targets [1]. These effects become particularly important for E/ Ue < 100 (here E= ion energy and Ue = electron-screening potential energy). Thus these effects become significant for the understanding of reactions involved in nucleosynthesis of the elements and the interpretation of astrophysical data [1]. Another example of the behavior is the surprising threshold behavior near 18 keV for deuterons stopping in 3He gas at energies below the Bragg peak [2]. As pointed out in ref [1], the theoretical explanation for these effects is still under debate. Several researchers have proposed variations of the Trojan Horse Method (THM) to explain these effects [3]. In this paper, we propose an alternate mechanism associated with electron charge accumulation around the target atoms arising from the solid-state structure of the host. This concept will be explained in terms of density functional calculations of charge density profiles in a target undergoing ion dynamic effects [4]. REFERENCES [1] F. Strieder, et al., Naturwissenschaften (2000)88:461-467 [2] A. Formicola, et al., (2000) Eur Phys J. A 8:443-446 [3] S. Typel and H H Wolter, (2000) Few-Body System 29:75-93 [4] G. Miley and H. Hora, (2000) Nuclear Reactions in Solids, APS mtg. Lansing, MI [5] G. Miley, A. Lipson, N. Luo, and H. Hora, (2003) IEEE NSS/MIC Conf., Portland, OR

  14. Nanoscale Dynamics of Radiosensitivity: Role of Low Energy Electrons

    NASA Astrophysics Data System (ADS)

    Sanche, Léon

    This chapter addresses the nanoscale dynamics involved in the sensitization of biological cells to ionizing radiation. More specifically, it describes the role of low energy electrons (LEE) in radiosensitization by gold nanoparticles and chemotherapeutic agents, as well as potential applications to radiotherapy. The basic mechanisms of action of the LEE generated within nanoscopic volumes by ionizing radiation are described in solid water ice and various forms of DNA. These latter include the subunits (i.e., a base, a sugar or the phosphate group), short single strands (i.e., oligonucleotides) and plasmid and linear DNA. By comparing the results from experiments with the different forms of the DNA molecule and theory, it is possible to determine fundamental mechanisms that are involved in the dissociation of the subunits, base release and the production of single, double-strand breaks and cross-links. Below 15 eV, LEE localize on DNA subunits to form transient negative ions. Such states can damage DNA by dissociating into a stable anion and radical fragment(s), via dissociative electron attachment, or by decaying into dissociative electronically excited states. LEE can also transfer from one DNA subunit to another, particularly from a base to the phosphate group, where they can induce cleavage of the C-O bond (i.e., break a strand). DNA damage and the corresponding nanoscale dynamics are found to be modified in the presence of other cellular constituents. For example, condensing on DNA the most abundant cellular molecule, H2O, induces the formation of a new type of transient anion whose parent is a H2O-DNA complex.

  15. Detectors for low energy electron cooling in RHIC

    SciTech Connect

    Carlier, F. S.

    2016-02-15

    Low energy operation of RHIC is of particular interest to study the location of a possible critical point in the QCD phase diagram. The performance of RHIC at energies equal to or lower than 10 GV/nucleon is limited by nonlinearities, Intra-BeamScattering (IBS) processes and space-charge effects. To successfully address the luminosity and ion store lifetime limitations imposed by IBS the method of electron cooling has been envisaged. During electron cooling processes electrons are injected along with the ion beam at the nominal ion bunch velocities. The velocity spread of the ion beam is reduced in all planes through Coulomb interactions between the cold electron beam and the ion beam. The electron cooling system proposed for RHIC will be the first of its kind to use bunched beams for the delivery of the electron bunches, and will therefore be accompanied by the necessary challenges. The designed electron cooler will be located in IP2. The electron bunches will be accelerated by a linac before being injected along side the ion beams. Thirty consecutive electron bunches will be injected to overlap with a single ion bunch. They will first cool the yellow beam before being extracted turned by 180-degrees and reinjected into the blue beam for cooling. As such, both the yellow and blue beams will be cooled by the same ion bunches. This will pose considerable challenges to ensure proper electron beam quality to cool the second ion beam. Furthermore, no ondulator will be used in the electron cooler so radiative recombination between the ions and the electrons will occur.

  16. Charge neutralized low energy beam transport at Brookhaven 200 MeV linac

    SciTech Connect

    Raparia, D. Alessi, J.; Atoian, G.; Zelenski, A.

    2016-02-15

    The H{sup −} magnetron source provides about 100 mA H{sup −} beam to be match into the radio-frequency quadrupole accelerator. As H{sup −} beam traverses through low energy transport, it ionizes the residual gas and electrons are repelled and positive ions are trapped in the beam, due to negative potential of the beam, providing charge neutralization for the H{sup −} beam. The neutralization time for the critical density depends upon the background gas and its pressure. Critical density for xenon gas at 35 keV is about 43 times smaller than that of hydrogen and stripping cross section is only 5 times than that of hydrogen gas. We are using xenon gas to reduce neutralization time and to improve transmission through the 200 MeV linac. We are also using pulse nitrogen gas to improve transmission and stability of polarized H{sup −} beam from optically pumped polarized ion source.

  17. Implantable Microimagers

    PubMed Central

    Ng, David C.; Tokuda, Takashi; Shiosaka, Sadao; Tano, Yasuo; Ohta, Jun

    2008-01-01

    Implantable devices such as cardiac pacemakers, drug-delivery systems, and defibrillators have had a tremendous impact on the quality of live for many disabled people. To date, many devices have been developed for implantation into various parts of the human body. In this paper, we focus on devices implanted in the head. In particular, we describe the technologies necessary to create implantable microimagers. Design, fabrication, and implementation issues are discussed vis-à-vis two examples of implantable microimagers; the retinal prosthesis and in vivo neuro-microimager. Testing of these devices in animals verify the use of the microimagers in the implanted state. We believe that further advancement of these devices will lead to the development of a new method for medical and scientific applications. PMID:27879873

  18. Nitrogen In Saturn's Magnetosphere

    NASA Astrophysics Data System (ADS)

    Smith, H. T.; Sittler, E. C.; Johnson, R. E.; McComas, D. J.; Reisenfeld, D.; Shappirio, M. D.; Baragiola, R.; Michael, M.; Shematovich, V. I.; Crary, F.; Young, D. T.

    2004-12-01

    We are analyzing CAPS instrument data on Cassini to look for nitrogen ions in Saturn's magnetosphere. Because Voyager could not separate oxygen and nitrogen, there has been considerable controversy on nitrogen's presence and relative importance. Two principal sources have been suggested: Titan's atmosphere and nitrogen species trapped in Saturn's icy satellite surfaces (Sittler et al 2004). The latter may be primordial nitrogen, likely as NH3 in ice (Stevenson 1982; Squyers et al. 1983) or nitrogen ions that have been implanted in the surface (Delitsky and Lane 2002). We will present the results of Saturnian nitrogen cloud modeling and relevant CAPS observations. We recently described the Titan source (Michael, et al. 2004; Shematovich et al. 2003; Smith et al. 2004; Sittler et al. 2004) in preparation for Cassini's Saturnian plasma measurements. Two components were identified: energetic nitrogen ions formed near Titan and energized as they diffused inward (Sittler et al. 2004) and neutrals in orbits with small perigee that became ionized in the inner magnetosphere (Smith et al 2004). The latter component would be a source of lower energy, co-rotating nitrogen ions in the inner magnetosphere. Such a component would have an energy spectrum similar to nitrogen species sputtered from the icy satellite surfaces (Johnson and Sittler 1990). However, the mass spectrum would differ, likely containing NHx and NOx species also, and, hence, may be separated from the Titan source. Our preliminary analysis for nitrogen species in the CAPS data will be compared to our models. Of interest will be the energy spectra, which can indicate whether any nitrogen present is formed locally or near Titan's orbit and diffused inward. This work is supported by the NASA Planetary Atmospheres, NASA Graduate Student Research, Virginia Space Grant Consortium Graduate Research Fellowship and CAPS Cassini instrument team programs.

  19. Low Energy Electrons as Probing Tool for Astrochemical Reaction Mechanisms

    NASA Astrophysics Data System (ADS)

    Hendrik Bredehöft, Jan; Swiderek, Petra; Hamann, Thorben

    hitting anything solid, they will create secondary electrons. These electrons are in fact the energy source needed to run interstellar chemistry. Slow electrons can in principle trigger three different primary processes in a molecule. The first is ionisation by electron impact (EI), which is used to create ions in mass spectrometry. In this process an electron hits a molecule M and knocks an outer shell electron to create a cation. This occurs whenever the electron energy is above the ionisation threshold of the target molecule. Another possibility is the attachment of a slow electron to a molecule to create an anion. This can occur at sharply defined resonance energies specific to the molecule M. A third possibility is to excite the molecule M to a neutral state M∗ .[9] M + e- -> M+ + 2 e- (Electron impact ionisation) M + e- -> M- (Electron attachment) M + e- -> M∗ + e- (Neutral excitation) The created states M+ , M- and M∗ are usually not stable states so they very often dissociate into ions and radicals, which can then further react with neighbouring molecules to form new chemical species. In these chemical reactions some products can be formed even at very low temperatures that would otherwise require a lot of thermal energy and/or special catalysts. The formation of ethylamine from ethylene and ammonia by hydroamination is one such example. The reaction is characterized by a high activation barrier caused by the electronic repulsion between the electron density rich C=C double bound and the lone pair electrons of ammo-nia. The reaction also has a highly negative entropy, so it becomes less favourable at higher temperatures, ruling out heat as a means to facilitate the reaction. In classical chemistry this problem is overcome by the use of catalysts. Unfortunately there still is no general catalyst for this kind of reaction. Recently it was shown that the reaction can efficiently be induced by low energy electron radiation.[10] One of the reaction partners is

  20. Meta-analysis on intravascular low energy laser therapy

    NASA Astrophysics Data System (ADS)

    Zhao, Shu-Dong; Liu, Timon Cheng-Yi; Wang, Yan-Fang; Liu, Song-Hao

    2008-12-01

    Intravascular low energy laser therapy (ILELT) was put forward for cardiocirculatory diseases in USA in 1982, was popular in Russia in 1980s, and then in China in 1990s. The therapeutic effects of ILELT and drugs in comparison with drugs only on Chinese patients and their blood parameters were analyzed with meta-analyses and reported as (OR, 95%CI) for patient improvement and (WMD, 95% CI) for blood parameter improvement, where 95%CI, OR and WMD denoted 95% confidence intervals, odds ratio and weighted mean difference, respectively. It was found that the patients of cerebral infarction (2.39, 2.09~2.74) and cerebrovascular diseases (2.97, 1.69~2.53) were cured, respectively, (P < 0.01), and the symptom improvement of patients of cerebral infarction, cerebrovascular diseases and diabetes were significant (3.13, 2.79~3.51), (4.92, 3.39~7.14) , and (3.80, 2.79~5.18), and mild (3.66, 3.15~4.24), (4.95, 2.77~8.84), and (7.11, 4.54~11.13), respectively, (P < 0.01). It was also found that the blood parameters such as cholesterol (-0.78, -1.32~-0.24), total cholesterol (-1.08, -1.80~-0.36), low density lipoprotein cholesterol (-0.6, -1.01~-0.19), triacylglycerol (0.63, -0.83~-0.42), high density lipoprotein (0.34, 0.10~0.59), erythrocyte aggregation index (-0.24, -0.27~-0.21), erythrocyte Sedimentation Rate (-4.57, -7.26~-1.89), fibrinogen (-0.76, -1.31~-0.21), whole blood contrast viscosity (-0.40, -0.69~-0.12), low cut blood viscosity (-1.2, -1.93~-0.48), high cut blood viscosity (-0.62, -0.92~-0.32), whole blood viscosity(-1.2, -1.85~-0.54) and plasma blood contrast viscosity(-0.07, -0.12~-0.03) were found improved (P < 0.05). It is concluded that the patients of cerebral infarction, cerebrovascular diseases and diabetes might be improved with ILELT, which might be mediated by blood parameter improvement.